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STORMWATER COMPREHENSIVE DEVELOPMENT PLAN SANTA ROSA COUNTY FL Feb 1988 TD 665 .S26 1988 3 EA"ECUTIVE SUMMARY N-N .......... . ......... .. . ....... .... . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .................: . ...... .............. .............. .. ....... .......... :T 0: R .......... . ........... . ......... . ................. .. : ........................ ........ ......... .. ........ ..... ............ ............. ............ ........ ........ .......... X. --A Prepared BY: JOHNSON/CRE=O'rnlxm9j/.FA13'rnlx%9j CO=TING == foln Association With: ENGINEERING & PLANNING 0 ARCHITECTURE LANDSCAPE ARCHITECTURE US Departmont of Commerce NOAA Coastal Sorvices Center Library 2234 South Hobson Avenue Charleston, SC 29405-2413-- This project was partially funded by a grant from the Office of Coastal Management, Department of Environmental Regulation, with funds provided by the National Ocearlic and Atmospheric Administration under the Coastal Zone Management Act of 1972, as amended. SANTA ROSA COUNTY COMPREHENSIVE ST0RMWATER DEVELOPMENT PIAN EXECUTIVE SUMMARY February 4, 1988 EXISTING NEEDS A. Capital Improvement Projects Construction Total cost cost 1 Major New System $1,800,000 $2,070,000 46 Remedial Projects 1,755,68 2,019.00 TOTAL $3,555,685 $4,089,000 B. Comprehensive Stormwater Management Ordinance C. Formalized Technical Design Standards and Criteria D. Systematic Stormwater Management Program E. Baseline Conditions Analysis F. Stormwater Facilities Inventory G. Stormwater Atlas H. Enhanced 0 & M Program I. Enhanced CIP Program FUITURE NEEDS A. Potential Capital Improvement Projects construction Total cost cost 15 Maj or Conveyance $ 833,700 $ 962,000 Structures 8 Minor Culverts 168,800- 192,000 TOTAL $1,000,500 $1,118,000 B. Increased 0 & M Requirements C. Repair and Replacement. Program for Existing Facilities D . Regulation and Monitoring of Development Activities E. Regulation of Private Stormwater Facility Design and Construction F Development of Long-Term Financing for County Stormwater Management Program SRJDY PROEUCIS A. Initial Stormwater Facility Inventory * 430 Major Facilities * Unique Structure Numbering System * Size, Type and Ijocation of Facilities B. Stormwater Atlas of Entire County � Basin and Subbasin Delineations � Structure Identification C. Draft Stonwater Management ordinance � Provides for Floodplain Management � Requires Stonruater Improvements � Provides for Erosion and Sediment Control � Requires Permits � Provides for Penalties � Includes an Appeals Process � Regionally Consistent D. Draft Stormwater Engineering Teckmcal Manual � Provides Requirements for a Stormwater Management Plan � Establishes Engineering standards and criteria � Defines Acceptable Analytical Methods � Provides for Development of Adminisstxative Guidelines by County E. Capital Improvements Program � Identification of 47 Currently Needed Projects costing approximately $4,089,000 * Preliminaxy Identification of 23 Potential Projects that may be required after 1998 costing approximately $1,118,000 � Prioritization of CIP Projects for Implementation F. Implementation Program for County Storadater management program � Identified CIP Projects � Potential CIP Projects � Strategic Basin Studies � 0 & M Program � Repair and Replacement Program � 20-Year Strategy G. Draft Goals, objectives and Policies for the Stonwater Management Program H. Detailed Report Vbich Summarizes the Various Aspects of the Cwprehensive Storawater Development Plan 2 RECOMMENDATIONS A. Adopt the Stormwater Managenjent ordinance for the Regulation of StornTwater in Santa Rosa County B. Approve the Stormwater Engineering Technical Manual to Direct the Design of Stormwater Management Facilities in Santa Rosa County C. Fund the First year of the Drainage Facilities Survey and Atlas Updating D. Authorize a Functional Needs Assesment to: � Identify Detailed Stonruater Funding Needs � Define organizational Needs and Structure � Define Appropriate Funding Mechanisms � Evaluate Suitability of Funding Meduv-dsms to Meet Long-term Revenue Needs E. Develop a Detention/Retention Pond Policy Which Addresses: * Standards for Pond Design for Public vs. Private Ownership * Procedures for Accepting Ponds for Public Ow@@p and Maintenance * Conditions and Funding Mechanism for Accepting Ponds for Public Maintenance * Pravision of a Continuing and Increasing Source of Funding for Pond Maintenance 3 A SANTA ROSA COl`_NTY WCOMPREHENSIVE STORMWATER DEVELOPMENT PLAN/ 000 ........... ... . . . . . . . . ..... ........................ .. ........... ....................... .......... ...... ... ... ...... ........... ....... ..... .... . -.-Xv .......... ........ ....... ... .......... ....................... ............ ............ ............ ............ ............ .......... ........... .......... -:xX ..... .......... X. ............... ........ . ....... .. . ..... . .......... .. . . ...... . ............. .......... ................. . ...... . .. ..... .. ..... .... .... .............. ........... ....................... . ............ ..... ........ :5.5... ix .......... JANUARY 1988 ............. Sol. . . . . . . . . . . . . . . . Prepared By: :0MTS0N/CP6=0-nV/FA n'nV aP.%W . Cm=Tm EMIN= in Association With: 1 IRC 4 Cl I'-' -I"' IL 11 - 11 A k I k I I k I/,- A r)i-L_Jf'rrf-n I D r i A A nC A Dlo-Wi'r-.l`-'n lPr SANTA ROSA COUNTY COMPREHENSIVE STORMWATER DEVELOPMENT PLAN TABLE OF CONTENTS SECTION TITLE, PAGE 1 INTRODUCTION 1.1 Background 1-1 1.2 Purpose 1-2 2 STORMWATER MANAGEMENT PLAN 2.1 General 2-1 2.2 Preparation of Stormwater Managememt Plans 2-1 2.2.1 Preparation by Qualified Professional 2-1 2.2.2 Submission Standards 2-1 2.3 Contents of Plan 2-2 2.3.1 Application Information 2-2 2.3.2 Engineer's Report 2-3 2.4 Construction Plans and Specifications 2-6 2.5 Operation and Maintenance 2-6 3 ENGINEERING STANDARDS 3.1 General Design Criteria 3-1 3.1.1 Design Method 3-1 3.1.2 Design Frequency 3-1 3.1.3 Coefficient of Runoff 3-2 3.1.4 Elevation of the Low Edge 3-2 of Street Pavement 3.1.5 Elevation of the Bottom of Street Subgrade 3-4 tm: SANTA ROSA- 2: 11 TABLE OF CONTENTS (Continued) SECTION TITLE PAGE 3.2 Culvert Design 3-5 3.2.1 Manning's Coefficient 'In" for Culvert 3-5 3.2.2 Minimum Culvert Size 3-5 3.2.3 Pipe Size Increment 3-5 3.2.4 Culvert Length 3-5 3.2.5 Maximum Velocity 3-5 3.2.6 Endwalls 3-6 3.2.7 Minimum Clearance 3-6 3.2.8 Conflict Manholes 3-6 3.3 Storm Sewer Design 3-7 3.3.1 Storm Sewer Tabulations 3-7 .3.3.2 Inlets, Manholes and Junction Boxes 3-7 3.3.3 Storm Sewer Alignment 3-7 3.3.4 Hydraulic Gradient Slope and Elevation 3-9 3.3.5 Minimum Physical Slope 3-9 3.3.6 Inlet Capacity 3-9 3.3.7 Maximum Gutter Run 3-9 3.3.8 Inlet Location 3-10 3.3.9 Drainage Easement or Right-of-Way 3-10 3.4 Non-Roadway Ditches 3-11 3.4.1 Drainge Easement or Right-of-Way 3-11 3.4.2 Grading Adjacent to Ditches 3-11 3.4.3 Maximum Sideslope 3-11 3.4.4 Minimum Bottom Width 3-11 3.4.5 Dependence on Future Units 3-12 3.4.6 Design 3-12 3.4.7 Maximum Allowable Velocity 3-12 3.4.8 Ditch Grades 3-12 3.4.9 Pavement 3-13 3.4.10 Grassing and Mulching 3-13 3.4.11 Utilities Crossing Drainage Easement or Right-of-Way 3-14 tm:SANTA ROSA-2:11 TABLE OF CONTENTS (Continued) SECTION TITLE PAGE 3.5 Detention and Retention Basins 3-14 3.5.1 General Requirements 3-14 3.5.2 Drainage Easement or Right-of-Way 3-15 3.5.3 Stormwater ingress 3-15 3.5.4 Maximum Sideslope 3-15 3.5.5 Fencing 3-16 3.5.6 Minimum Freeboard 3-16 3.5.7 Grassing, Mulching and Sodding 3-16 3.5.8 Detention Basins 3-16 3.5.9 Retention Basins 3-18 3.6 Underdrains 3-21 3.7 Material Specifications for Culverts 3-23 3.7.1 General Specifications 3-23 3.7.2 Culvert Joints 3-25 4 ANALYTICAL METHODS 4.1 General 4-1 4.2 Time of Concentration 4-1 4.2.1 Overland Flow 4-2 4.2.2 Shallow Channel Flow 4-5 4.2.3 Main Channel Flow 4-5 4.3 Stormwater Runoff 4-5 4.3.1 Rational Method 4-7 4.3.2 Modified Rational Method 4-7 4.3.3 Synthetic Unit HydrographMethod 4-8 4.3.4 Santa Barbara Urban Hydrograph Method 4-8 4.4 Design Storm 4-9 4.4.1 Rainfall Frequency 4-9 4.4.2 Rainfall Duration 4-10 4.4.3 Rainfall Volume 4-11 4.4.4 Rainfall Distribution 4-11 tm: SANTA ROSA- 2: 11 TABLE OF CONTENTS (Continued) SECTION TITLE PAGE 5 ALTERNATIVE GUIDELINES 5.1 General 5-1 5.2 Applications 5-1 5.3 Application Packages 5-1 5.4 Review Procedures and Time Frames 5-1 5.5 Issuance of Permit 5-1 tm:SANTA ROSA-2:II 0 I 6 .. I SECTION ONE I CSE C ONE ip Section 1 INTRODUCTION 1.1. BACKGROUND Unless specifically stated otherwise, any proposed designs in conflict with this Manual will require either a waiver of the applicable County ordinance or approval of the County Engineer, whichever is applicable. In addition, the County Engineer shall be solely responsible for interpreting any criteria in this Manual which may be deemed vague or uncertain. Furthermore, the interpretation shall be in the best interest of the citizens of Santa Rosa County. In the past twenty years, Santa Rosa County has been undergoing dramatic development and growth. All predictions of future development indicate that growth patterns will not only continue but will, in fact increase. Growth trends indicate that by the beginning of the next century, Florida is expected to experience the third highest state-wide population growth in the nation. Impacts of urbanization and land development impose technological, economic, environmental, social and political implications upon the quality of life for the future. Stormwater management affects all governmental jurisdictions and all parcels of property. As a result, regulation is often passed between jurisdictional boundaries. This necessitates the development of a stormwater management design plan which balances public and private interests. tm:SANTA ROSA:CC 1.2 PURPOSE The purpose of this Manual is to guide engineers, architects, planners, and developers in the design of stormwater management systems in Santa Rosa County. The Manual integrates recommended methodologies, design procedures and standards into a single-source criteria. This manual represents a coordinated effort to bring water resource managers, developers and designers up-to-date with the regulations and criteria imparted upon stormwater management in Santa Rosa County. This manual will be utilized by Santa Rosa County for permitting, study, review, and design. tm:SANTA ROSA:CC 1-2 0 6 SECTION TWO I CSE C :W DO 6 @@l Section 2 STORMWATER MANAGEMENT PLAN 2.1 GENERAL It is the responsibility of the Applicant to include 'in the Stormwater Management Plan sufficient information for the County Engineer to evaluate the environmental characteristics of the affected areas, the potential and predicted impacts of the proposed activity on County receiving waters, and the effectiveness and acceptability of those measures proposed by the Appl'-icant for reducing adverse impacts. The Stormwater Management Plan shall contain maps, graphs, tables, photographs, narrative descriptions, explanations and the information required by this section. 2.2 PREPARATION OF STORMWATER MANAGEMENT PLANS It is the responsibility of the Applicant to prepare and submit a Stormwater Management Plan. 2.2.1 Preparation by Qualified Professional A. The Stormwater Management Plan shall be prepared, signed and sealed by a Professional Engineer registered in the State of Florida. tm:SANTA ROSA:DD 2-1 B The Engineer of Record shall be responsible for his stormwater management system design. 2.2.2 Submission Standards The County Engineer shall establish standards for the Stormwater Management Plan and materials submitted as supporting documents. Minimum standards are 2.3 CONTENTS OF PLAN The Stormwater Management Plan shall consist of the Application, the Engineer's Report, the plans for site alteration clearly indicating the Applicant's proposed stormwater management facilities, and supporting documents as required by the County Engineer or considered to be essential by the Engineer of Record. 2.3.1 Application Information The name, address and telephone number of the applicant. tm:SANTA ROSA:DD 2-2 2.3.2 Engineer's Report The Engineer's Report shall address, at a minimum, the following aspects of stormwater management on the Applicant's property: A. Site Location Information A location map,.Iegal description and an aerial photo with boundary lines clearly outlining the project extent. B. Existing/Predevelopment Conditions The existing predevelopment environmental and hydrologic conditions of the site and/or receiving waters and wetlands described in detail with appropriate site plan including the following: 1. The direction, flow rate, and volume of stormwater runoff for existing conditions and, to the extent practicable, predevelopment conditions. 2. The location of natural storage areas on the site where stormwater presently collects and/or percolates into the ground. tm:SANTA ROSA:DD 2-3 3. A description Of all upland acreage, watercourses, waterbodies and wetlands on or adjacent to the si te or into which stormwater flows. 4. Groundwater levels, including seasonal fluctuations. 5. Location of floodplains. 6. Vegetation. 7. Topography. 8. Soils. 9. Basin and subbasin delineations. 10. Points of discharge and estimated discharge rates. C. Proposed Site Alteration and Impacts 1. Any proposed alterations of the site described in detail, including changes in topography; areas where vegetation will be cleared or killed; areas that will be covered with an tm:SANTA ROSA:DD 2-4 impervious surface with a description of the surfacing material; and, the size and location of any buildings or other structures. 2. Predicted impacts of the proposed development on existing conditions described in detail, including change in water quality; changes in groundwater levels; changes in the incidence and duration of flooding on the site and properties upstream and downstream from it; impacts on wetlands; and, impacts on vegetation. 3. All components of the stormwater management system and any measure for the detention, retention, or infiltration of water or for the protection of water quality, described in detail, including: a. The channel, direction, flow rate, and volume of stormwater that will be conveyed from the site, with a comparison to existing conditions and, to the extent practicable, predevelopment conditions. b. Detention and retention areas, including plans for the discharge of contained water, and maintenance plans. C. Areas of the site to be used or reserved for percolation. tm:SANTA ROSA:DD 2-5 d A plan for the control of erosion and sedimentation which describes in detail the type and location of control measures, the stage of development at which they will be put into place or used, provisions for their maintenance, and disposal of collected sediment. e. Any other information which the applicant or the County Engineer believes is reasonably necessary for an evaluation of the proposed development. 2.4 CONSTRUCTION PLANS AND SPECIFICATIONS Signed and sealed construction plans and specifications for all components of the stormwater management system. 2.5 OPERATION AND MAINTENANCE PLAN An Operation and Maintenance Plan for proposed facilities which sets forth scheduled maintenance needs and includes an opera tion/ma i ntenance manual to be provided to the designated entity responsible for maintenance of the stormwater management system. tm:SANTA ROSA:DD 2-6 b I . I .0 IIII SECTION T REE @l CSECI H:RDEE I io I Section 3 ENGINEERING STANDARDS 3.1 GENERAL DESIGN CRITERIA 3.1.1 Design Method The design method used shall be the state-of-the-art except that the Rational Method shall not be used for drainage areas over ten (10) acres unless approved by the County Engineer. 3.1.2 Design Frequency Rainfall data is to be obtained using the Florida DOT Zone 1 Rainfall Curves. Specific design storm information and requirements are further described in Section 4.4 of this Manual. The design storm frequency and duration shall be as listed below: Facility Frequency Duration Bridges 50-Year Critical Duration Crossdrains, ditches, side- 25-Year Critical Duration drains and storm sewers for external subdivision drainage Crossdrains, ditches, side- 25-Year Critical Duration drdins and storm sewers for internal subdivision drainage Detention basins 25-Year 24-hour Retention basins without 100-Year 24-hour an overflow outlet tm: SANTA ROSA: EE 3-1 Facility Frequency Duration Retention basins with an 25 Year 24-hour overflow outlet Floor elevations Floor elevations shall be designed to be 2.0 feet above the water level associa-ted with the 100-Year storm event (except that near retention basins without an overflow outlet the floor elevations shall be no lower than 3.0' above the retention basin 100- year design high water elevation) 3.1.3 Coefficient of Runoff The coefficient of runoff for roofed and paved areas shall be 0.95. The coefficient of runoff for bodies of water shall be 1.00. The coefficient of runoff for other areas shall be determined by the Engineer of Record by considering vegetation, slope, soil type and season high groundwater elevation using common engineering standard values. Guidelines for selection of appropriate runoff coefficients are established in Table 3-1. 3.1.4 Elevation of the Low Edge of Street Pavement A. The low edge of street pavement near marine waters of the Gulf of Mexico, Santa Rosa Sound, Pensacola Bay, Blackwater Bay and Escambia Bay, shall be no lower than elevation 7.0 NGVD. tm: SANTA ROSA: EE 3-2 TABLE 3-1 SUGGESTED RATIONAL METHOD RUNOFF COEFFICIENTS a FOR 2 TO 10 YEAR DESIGN FREQUENCY STORMS Sandy Soils Clay Soils Slope Land Use min. Max. Min. Max. Flat Woodlands b 0.10 0.15 0.15 0.20 (0-2%) Pasture, grass, and farmland 0.15 0.20 0.20 0.25 Rooftops and pavement 0.95 0.95 0.95 0.95 Pervious pavements c 0.75 0.95 0.90 0.95 SFR: @-acre lots and larger 0.30 0.35 0.35 0.45 Smaller lots 0.35 0.45 0.40 0.50 Duplexes 0.35 0.45 0.40 0.50 MFR: Apartments, townhouses, and condominiums 0.45 0.60 0.50 0.70 Commercial and Industrial 0.50 0.95 0.50 0.95 Rolling Woodlands b 0.15 0.20 0.20 0.25 (2-7%) Pasture, grass, and farmland 0.20 0.25 0.25 0.30 Rooftops and pavement 0.95 0.95 0.95 0.95 Pervious pavements c 0.80 0.95 0.90 0.95 SFR: @-acre lots and larger 0.35 0.50 0.40 0.55 Smaller lots 0.40 0.55 0.45 0.60 Duplexes 0.40 0.55 0.45 0.60 MFR: Apartments, townhouses, and condominiums 0.50 0.70 0.60 0.80 Commercial and Industr ial 0.50 0.95 0.60 0.95 Steep Woodlands b 0.20 0.25 0.25 0.30 Pasture, grass, and farmland 0.25 0.35 0.30 0.40 Rooftops and pavement 0.95 0.95 0.95 0.95 Pervious pavements c 0.85 0.95 0.90 0.95 SFR: @-acre lots and larger 0.40 0.55 0.50 0.65 Smaller lots 0.45 0.60 0.55 0 . '70 Duplexes 0.45 0.60 0.55 0.70 KFR: Apartments, townhouses, and condominiums 0.60 0.75 0.65 0.35 Commercial and Industrial 0.60 0.95 0.65 0.95 aWeighted coefficient based on percentage of impervious surfaces and green areas must be selected for each site. b Coefficients assume good ground cover and conservation treatment. c Depends on depth and degree of permeability of underlying strata. Note: SFR a Single Family Residential MFR = Multi-Family Residential Soure: FDOT Drainage Manual (1987) tm: SANTA ROSA: EE 3-3 B The low edge of street pavement shall be no lower than 0.5' above the twenty-five (25) year design high water elevation for external subdivision drainage except that when and/or sand-clay base is used the low edge of street pavement shall be no lower than 1.0' above the twenty-five (25) year design high water elevation. C. The low edge of street pavement shall be no lower than 1.0' above the twenty-five (25) year design high water elevation for internal subdivision drainage. D. The low edge of street pavement near detention basins with an outflow outlet shall be no lower than 1.0' above the twenty-five (25) year design high water elevation. E. The low edge of street pavement near retention basins without an overflow outlet shall be no lower than 1.0' above the one hundred (100) year design high water elevation. F. The low edge of street pavement near retention basins with an overflow outlet shall be no lower than 1.0' above the twenty-five (25) year design high water elevation. 3.1.5 Elevation of the Bottom of Street Subgrade The bottom of street subgrade shall be no lower than 0.5 foot above the design seasonal high groundwater elevation. tm: SAINTA ROSA: EE 3-4 3.2 CULVERT DESIGN 3.2.1 Manning's Coefficient "n" for Culverts Type of Culvert Manning's Coefficient "n" Reinforced concrete pipe 0.012 Concrete box culvert 0.012 Corrugated metal pipe 0.024 3.2.2 Minimum Culvert Size Type of Culvert Minimum Size Crossdrains 1811 or Equivalent Elliptical Pipe Storm sewer 18" or Equivalent Elliptical Pipe Sidedrains 18" or Equivalent Elliptical Pipe Box culvert 3' x 3' 3.2.3 Pipe Size Increment Pipe sizes above twenty-four (24) inch or equivalent elliptical section shall be based on six (6) inch increment. 3.2.4 Culvert Length The maximum length of culvert to be used without an access structure shall be: Culvert Size Maximum Length 1511 pipe or elliptical equivalent 300' 18" pipe or elliptical equivalent 400' 24" to 36" pipe or elliptical equivalent 500' 4211 and larger pipe or equivalent 500' Box culvert 500, 3.2.5 Maximum Velocity Unless unstable or highly erosive soil conditions indicate a lower design -velocity is desirable, or unless ditch paving at the outlet is provided, the maximum allowable outlet velocity for culverts shall be 5.0 feet per second. tm: SANTA ROSA: EE 3-5 3.2.6 Endwalls Endwalls shall be installed on all culverts (except sidedrains which shall have mitered end sections) unless other provision is made for erosion protection. Endwalls shall conform to the latest editions of the Standard Indexes and the Florida DOT Standard Specifications for Road and Bridge Construction. 3.2.7 Minimum Clearance The minimum clearance for all pipe culverts shall be: To Minimum Clearance Bottom Roadway Subgrade 1.01 to Crown of Pipe Utility Crossing 0.51 to Shell of Pipe 3.2.8 Conflict Manholes A. Where it is necessary to allow a utility to pass through a manhole, inlet or junction box because of no reasonable alternative, the utility shall be ductile iron. The utility shall be located in the upper half of the storm sewer opening. B. A minimum of 1.0' clearance between the shell of the utility and invert of a culvert, entrance or discharge point, shall be provided. tm:SANTA ROSA:EE 3-6 C The manhole, inlet or junction box shall be appropriately sized to provide equivalent flow cross-section area to compensate for conflict pipe. 3.3 STORM SEWER DESIGN 3.3.1 Storm Sewer Tabulations In subdivisions where storm sewers are planned, the Engineer of Record shall include in his Engineering Report appropriate drainage calculations prepared on a standard FDOT storm sewer tabulation form as shown in Figure -3-1. Procedures fo r use of this storm tabulation form is described in FDOT's Drainage Manual, Volume 24 (1987). 3.3.2 Inlets, Manholes and Junction Boxes All inlets, manholes and junction boxes shall conform to the Santa Rosa County Standard Indexes and the Florida DOT Standard Specifications for Road and Bridge Construction, latest edition. 3.3.3 Storm Sewer Alignment All storm sewer alignments shall avoid abrupt changes in direction or slope and shall maintain reasonable consistencies in flow velocity. Where abrupt changes in direction or slope are encountered, provisions shall be made to handle the resulting head loss. All inlets and manholes shall be designed to drop 0.10 foot in elevation for any changes in alignment of more than 45 0. tm:SANTA ROSA:EE 3-7 STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION STORM DRAIN TABULATION FORM SHEET NO. OAFF rsojtcT NO. SOAn - couNTY SY PRAINAC ELLV. OF N.C. ZONE -1-REquil"cl 'IR LOC A7 I col ARE& (ACRES) k;jowN 1L@xv@ p t. b ...012 CONCRETE P11r or 12 J C C. FLOWL WE E TiVy. upp" Emu StAff DisriS I-A I L-LL L FIGURE 3-1 3.3.4 Hydraulic Gradient Slope and Elevation The maximum hydraulic gradient slope allowed will be that which will produce a velocity of: Type of Culvert Maximum Velocity O-Ring RCP 20 feet per second Diaper Joint RCP 12 feet per second Gasketed CMP 10 feet per second The maximum hydraulic gradient elevation shall be 1.0 feet below the low edge of street pavement. 3.3.5 Minimum Physical Slope The minimum physical slope for culverts shall be that which will produce a velocity of 2.5 feet per second when the culvert is flowing full. 3.3.6 Inlet Capacity The capacity of the inlet shall be considered to be 5.0 cubic feet per second per throat. The effects of inlet bypass shall be addressed by the Engineer of Record in his Engineering Report. 3.3.7 Maximum Gutter Run The maximum distance in which surface water will be allowed to run in the gutter shall be controlled by the spread of flow. The spread shall be limited tm: SANTA ROSA: EE 3-9 to the outside lane for a five (5) year frequency rainfall having a duration of ten (10) minutes plus the overland time of concentration. In no case shall the gutter run exceed eight hundred (800) feet. 3.3.8 Inlet Location A. Where inlets are located on returns in which one bf the intersecting roadway grades exceeds one (1) percent, a return profile shall be included in the construction plans. B. Other than at intersections and at lots which are wider than one hundred (100) feet, inlets shall be located as near as possible to common lot lines. 3.3.9 Drainage Easement or Right-of-Way Storm sewers shall be located in a drainage easement or right-of-way dedicated to Santa Rosa County. For storm sewers not within street right-of-way, the drainage easement or right-of-way width shall be sufficient to accommodate a work trench with 1:1 sideslopes and with a bottom width of 2.0 feet wider than the storm sewer width. In no case shall the drainage easement or right-of-way width be less than 30.0 feet. tm: SANTA ROSA: EE 3-10 3.4 NON-ROADWAY DITCHES 3.4.1 Drainage Easement or Right-of-Way Ditches shall have sufficient drainage easement or right-of-way dedicatWd to Santa Rosa County to allow for installation of the ditch plus an unobstructed 30.0-foot width maintenance berm on both sides, measured from the top of the bank, unless otherwise approved by the County Engineer. A drainage easement or right-of-way 30.0 feet in width shall be dedicated to Santa Rosa County from the street to the ditch wherever needed for ingress and egress. 3.4.2 Grading Adjacent,to Ditches Areas adjacent to ditches shall be graded to preclude the entrance of excessive stormwater runoff except at locations provided. 3.4.3 Maximum Sideslope The maximum sideslope shall be 4:1 for ditches within the boundaries of a subdivision and 3:1 for ditches outside the boundaries of a subdivision. 3.4.4 Minimum Bottom Width The minimum bottom width for trapezoidal ditches shall be 3.0 feet. Minimum width for other ditch cross-sections shall be established by the County Engineer. tm: SANTA ROSA: EE 3-11 3.4.5 Dependence on Future Units Where projects are designed in multiple units with a phased construction schedule, no design of an individual unit shall be dependent upon the ultimate installation of a future unit. 3.4.6 Design Ditches shall be sized using Manning's formula. In all cases, data giving drainage area, peak design flow rate, velocity and depth of flow shall be included in the drainage calculations. A hydraulic profile shall be included for all ditches which clearly shows ditch bottom, design water surface and top of bank for both left and right sides of the ditch. 3.4.7 Maximum Allowable Velocity Unless unstable or highly erosive soil conditions indicate a lower design velocity is desirable or unless ditch paving has been provided, the maximum velocity allowed shall be 2.5 feet per second. 3.4.8 Ditch Grades A minimum of 0.10% or the minimum required to provide for the design flow, whichever is greater shall be the minimum allowable ditch grade. Unless unstable or highly erosive soil conditions indicate a flatter grade is tm: SANTA ROSA: EE 3-12 desirable or unless ditch paving has been provided, the maxim um allowable grade shall be that which will produce a velocity of 2.5 feet per second. The following minimum erosion protection requirements shall be provided: Ditch Grade Protection Required 0.1% - 1.0% Grassing and Mulching 1.0% - 2.0% Sodding 2.0% and Greater Ditch Paving Ditches shall be sodded when the ditch grade is less than 1.0% and the velocity is greater than 2.0 feet per second. 3.4.9 Pavement All new non-roadway ditches within the boundaries of a subdivision with side slopes steeper than 4:1 or design velocities higher than 3.0 feet/per second shall be paved. The pavement shall be in accordance with the latest editions of the Standard Indexes and the Florida DOT Standard Specifications for Road and Bridge Construction. 3.4.10 Grassing and Mulching Drainage easements or rights-of-way shall be grassed and mulched in accordance with latest edition of the Florida DOT Standard Specifications for Road and Bridge Construction. tm: SANTA ROSA: EE 3-13 3.4.11 Utilities Crossing Drainage Easement or Right-of-Way Where it is necessary for a utility to cross the drainage easement or right- of-way, the following minimum requirements shall be adhered to: A. Aerial Crossing: Minimum of 3.0' clearance to design high water. B. Underground: Minimum of 3.0' clearance to the invert of the ditch. C. Utilities shall be adequately marked to protect against accidental damage during maintenance operations. D. No aerial supports shall be allowed in the confines of the ditch cut unless authorized by the County Engineer. E. All sleeves or crossings shall be ductile iron, or other suitable material subject to the approval of the County Engineer. 3.5 DETENTION AND RETENTION BASINS 3.5.1 General Requirements A peak flow attenuating basin shall be provided to reduce the peak discharge rate unless otherwise approved by the County Engineer. The instantaneous peak tm:SANTA ROSA: EE 3-14 discharge from the undeveloped site due to a twenty-five (25) year rainfall shall not be exceeded by the instantaneous peak discharge from the developed site due to this same storm event. Existing storage shall be considered when calculating the instantaneous peak discharge from the undeveloped site. A peak discharge analysis shall be included in the drainage calculations. 3.5.2 Drainage Easement or Right-of-Way Sufficient drainage easement or right-of-way shall be dedicated to Santa Rosa County to allow for installation of the basin plus an unobstructed (@@foo t wide maintenance berm around the perimeter of the basin unless otherwise approved by the County Engineer. Th I foot width is measured from the top of the bank. However, a retention basin with sideslopes of 6:1 or flatter may have a maintenance berm 10.0 feet in width. A drainage easement or right-of- way 30.0 feet in width shall be dedicated to Santa Rosa County from the street to the basin wherever needed for ingress and egress. 3.5.3 Stormwater Ingress Areas adjacent to the basin shall be graded to preclude the entrance of excessive stormwater runoff. Runoff ingress shall be by culvert with endwall. 3.5.4 Maximum Sideslope The maximum sideslope shall be 4:1 for fenced basins or 8:1 for unfenced basins. tm: SANTA ROSA: EE 3-15 3.5.5 Fencing Unless otherwise approved by the County Engineer, all fenced basins shall be enclosed by 8'-high galvanized chain link fencing on poles at 10, on center, top rails and bottom tension wires. Fence shall be topped with three strands of barbed wire and have a double swing gate with a clear opening of no less than 24'. 3.5.6 Minimum Freeboard The minimum freeboard for basins shall be 1.0 foot between design high water and top of bank. 3.5.7 Grassing, Mulching and Sodding The basin drainage easement or right-of-way shall be grassed and mulched in accordance with the latest editions of the Florida DOT Standard Specifications for Road and Bridge Construction. The sideslopes of the basin shall be sodded and maintained until the grass is established and the bottom of the basin shall be grassed and mulched (if designed as a dry bottom basin). 3.5.8 Detention Basins A. The seasonal high groundwater elevation shall be determined for a location proposed to be utilized as a detention basin. tm: SANTA ROSA: EE 3-16 B The outlet of a detention basin shall have a water level control structure that enables the basin to function as shown in the drainage calculations. The water level control structure shall not be a pipe riser and shall not be adjustable. The water level control structure shall be an endwall or ditch bottom inlet constructed in accordance with the Standard Indexes and the Florida DOT Standard Specifications for Road and Bridge Construction unless an endwall or ditch bottom inlet will not enable the basin to function as designed. in the event an endwall or ditch bottom inlet will not enable the basin to function as shown in the drainage calculations, the water level control structured used shall be approved by the County Engineer. C. In the event the water level control structure is an endwall, the design low water elevation of the detention basin shall be the endwall invert elevation. In the event the water level control structure is a ditch bottom inlet, the inlet shall have a slot and the design low water elevation of the detention basin shall be the slot invert elevation. For a man-made detention basin with standing water below the design low water elevation, the basin bottom shall be a minimum of 6.0 feet below the design low water elevation. D. Conditions downstream of the water level control structure (i.e., tailwater) shall be such that enable the water level control structure to function as indicated in the design calculations. tm:SANTA ROSA: EE 3-17 E Percolation may be considered in the design of a det ention basin provided the criteria for retention basins is met. In the event percolation is considered in the design of a detention basin, the design low water elevation of the detention bas-in shall be the bottom elevation of the basin. Percolation shall be determined in accordance with Section 3.5.9. 3.5.9 Retention Basins A. A suitable overflow outlet (man-made or natural ) shall be provided for retention basins where practical. B. Retention basins shall have a subsoil inves tigation report including one boring for each one-third (1/3) acre of basin bottom. However, there shall be no less than two borings per retention basin. The borings shall extend fifteen (15) feet below the proposed basin bottom and be uniformly distributed. The soil profile, and existing groundwater elevations and seasonal high groundwater elevation shall be determined for each boring. The soils shall be sampled and classified in accordance with the American Society for Testing and Materials Standard Method D2487. The subsoil investigation report shall be included in the drainage calculations. C. Retention basins shall have an infiltration rate test performed for each one-third (1/3) acre of basin bottom. The infiltration rate test shall be ASTM Standard Method D3385-75 (as modified below) and tm:SANTA ROSA: EE 3-18 shall be performed on the least permeable strata below and within 5.0-feet of the retention basin bottom. The County Engineer may authorize an alternate infiltration rate test. ASTM D3385-75 shall be modified as follows: 1. The outer ring shall be thirty-six (36) inches in diameter. 2. The allowable water depth may be up to twelve (12) inches. 3. The test shall be run for a minimum of four (4) hours. The water level shall be maintained at least six (6) inches deep for the duration of the test. 4. As an alternate to ASTM D3385-75(5.5) - Measurements and ASTM D3385-75(6) - Calculations, the infiltration rate may be determined by shutting off the water and recording the time required for water to drop 3.0 inches. 5. In lieu of ASTM D3385-75(7) Report - the infiltration rate shall be the lowest rate measured during the last two (2) hours, except when the rates decrease by more.than five (5) percent between the third and fourth hour measurements. if this occurs, the test duration shall be extended as necessary to reach a point of stability when the rate does not vary by over five (5) percent between successive one (1) hour measurements. tm: SANTA ROSA: EE 3-19 The County Engineer shall be notified 24 hours prior to the infiltration test. Test results certified by a qualified testing laboratory or the Engineer of Record shall be included in the drainage calculations portion of the Engineering Report. D. The retention basin bottom shall be no less than fifteen (15) feet above SM, SC, ML, CL, OL, MH, CH, OH and PT soils as defined by ASTM Standard Method D2487 and shall be no less than twenty (20) feet above bedrock. The seasonal high groundwater shall be at least five (5.0) feet bel ow the retention basin bottom for drainage CA (C = coefficient of runoff and A = area in acres) of 2.0 or less. - This clearance shall increase 1 inearly to 10.0 feet between CA = 2.0 to CA = 4. 0. For a CA of 4.0 or more, the clearance to seasonal high groundwater shall be at least 10.0 feet unless sufficient data is provided by the Engineer of Record to show the infiltration rate will not be reduced by mounding of the groundwater. E. The retention basin design shall be based on an infiltration rate that is one-half (112) of the lowest infiltration rate obtained from the tests . The infiltration through sideslopes shall be considered at the same rate as that for the basin bottom but shall be considered over the plan area of the sideslopes. F. The retention basin bottom shall be uniformly graded to provide a tm: SANTA ROSA: EE 3-20 low point twelve (12) inches below the bottom perimeter elevation. The final grading of the basin bottom shall remove the final six (6) inches and shal 1 be the last work in the construction of the project. 3.6 UNDERDRAINS A. Underdrains may be approved or required by the County Engineer to facilitate groundwater control during construction and may be left in place. When the use of underdrains is required, construction plans shall include all details necessary to clearly indicate the underdrain construction. B. Underdrains are considered to be a permanent control of the groundwater table. The design of the roadway may be based on long term groundwater level control through the use of underdrains. C. A filler fabric envelope shall be used with underdrains and shall be an approved strong, porous nylon, polyester, polypropylene or other fabric approved by the County Engineer which completely covers the underdrain surface in such a way as to prevent infiltration of surrounding material. The filter envelope shall weigh a minimum of 2.5 ounces per square yard, shall retain soil particles larger than two hundred twelve (212) microns (no. 70 sieve) and shall pass particles finer than twenty-five (25) microns. When tested in tm: SANTA ROSA: EE 3-21 accordance with ASTM D1682, the grab strength (wet) of the filter fabric shall not be less than one hundred (100) pounds and the grab elongation shall not be less than sixty (60) percent. Storage and handling of the filter fabric shall be in accordance with the manufacturer's recommendations. Torn or punctured filter fabric shall not be used. The filter fabric shall not be exposed to sunlight for periods exceeding the manufacturer's recommendation or six (6) weeks, whichever is shorter. D. Underdrain pipe shall be of sufficient size to effectively control the flow. Underdrain pipe shall be concrete, corrugated aluminum, polyvinyl-chloride, corrugated polyethylene or other material approved by the County Engineer. Concrete, corrugated aluminum and polyvinyl-chloride underdrain shal 1 be in accordance wi th. the Florida DOT Standard Specifications for Road and Bridge Construction, latest edition. Corrugated aluminum underdrain shall also meet the requirements of Section 3.7.1 b. 2. Corrugated polyethylene tubing underdrain installations shall conform to the following: 1. Corrugated polyethylene tubing and fittings shall meet the requirements of AASHTO M252, latest edition. The minimum wall thickness of the crown, sidewalls or valley shall be 0.025 .inches. Coiling of tubing is not permitted. tm: SANTA ROSA: EE 3-22 2. The tubing shall not be exposed to sunlight for periods exceeding the manufacturer's recommendation of six (6) weeks, whichever is shorter. Tubing shall be placed and maintained true to line and grade until secured with compacted backfill. Tubing shall not be placed under street pavement. Underdrain sections which deflect or collapse greater than five (5) percent shall be rejected. 3. Fine aggregate for cement concrete, in accordance with the Florida DOT Standard Specifications for Road and . Bridge Construction, latest edition, shall be used to backfili the trench, except that the County Engineer may approve other backfill material provided tests are submitted indicating the material will adequately serve as a filter. The minimum density of the backfill shall be ninety-five (95) percent of the standard laboratory density determined in accordance with AASHTO T99 (Method A). A three (3) inch layer of the approved backfill shall be placed under the pipe. 3.7 MATERIAL SPECIFICATIONS FOR CULVERTS 3.7.1 General Specifications A. Acceptable Materials 1. Reinforced Concrete Pipe (Round and Elliptical). tm: SANTA ROSA: EE 3-23 2. Corrugated Aluminum Alloy Pipe and Pipe Arch. 3. Cast-in-Place and Precast Reinforced Concrete Box Culvert. 4. Aluminum Alloy Box Culvert (subject to the approval of the County Engineer). 5. Corrugated Polyethylene Pipe (subject to approval of the County Engineer) Notes: 1. Corrugated.. Metal Pipe and metal box culverts will not be permitted south of Highway 90. 2. Corrugated metal pipe shall not be used under roadways accepted for ownership or maintenance by Santa Rosa County. B. Minimum Specifications 1. Workmanship and pipe materials shall conform to the Florida DOT Standard Specifications for Road and Bridge Construction, latest edition. 2. Corrugated Aluminum Alloy Pipe and Pipe Arch may not be used in tidal areas. 3. Concrete and reinforcing steel for cast-in-place reinforced concrete box culverts shall conform to the Florida DOT Standard tm: SANTA ROSA: EE 3-24 Specifications for Road and Bridge Construction, latest edition. 4. Precast reinforced concrete box culvert shall conform to the applicable American Society for Testing and Materials Standard Specifications (C789 or C850). The methods for construction of trench and foundation, and for laying and' backfilling shall conform to the requirements specified in Section 430 of the Florida DOT Standard Specifications for Road and Bridge Construction, latest edition, with the following additional requirements: the bedding shall consist of a maximum of six (6) inch depth of coarse concrete sand placed below the culvert to a minimum width of one (1) foot outside the exterior walls of the culvert between graded forms set one (1) foot outside each exterior wall of the box culvert. The sand shall be uniformly compacted and then graded off using the forms. The forms shall be removed after placement of the precast box culvert section. Holes provided for lifting or joint restraint shall be sealed by plugging using a non-shrinking mortar in accordance with Section 450-11.2 of the Florida DOT Standard Specifications for Road and Bridge Construction, latest edition. The mortar shall be properly cured to insure a sound and watertight plug. 3.7.2 Culvert Joints Joints and joint material for culverts shall conform to the Florida DOT tm:SANTA ROSA: EE 3-25 Standard Specifications for Road and Bridge construction, latest edition. Field joints for precast concrete box culvert shall be made with butyl rubber based preformed plastic gasket material. Culverts shall be subject to the requirements of Section 430-7.3 of the Florida DOT Standard Specifications for Road and bridge construction, latest edition, with the following additional requirements: 0 The culvert producer shall furnish to the Engineer of Record a written recommendation of the size (cross-sectional area) of gasket material which will create a watertight seal. 0 This recommendation shall be the minimum quantity of gasket"material permitted. In addition, the outside of each joint shall be completely wrapped with either a woven or non-woven filter fabric. The fabric shall be a minimum of two (2) feet in width and secured tightly against the box culvert section by metal strapping. The joint shall be secured by a device capable of holding the sections to line and grade as well as fully home. These devices shall be removed after sufficient backfill has been placed and compacted to secure the sections. tm:SANTA ROSA:EE 3-26 0 0 III C SECTION FOUR ammmmmmmmm@ S E C 1) 0 1 Section 4 ANALYTICAL METHODS 4.1 GENERAL Santa Rosa County will consider all sound analytical methods which are routinely used in Florida for use in the preparation of the Stormwater Management Plan by the Engineer of Record. However, techniques which are not specifically discussed in this section may require longer review periods than allowed under standard guidelines in order that the County Engineer can assess the validity and accuracy of these techniques for use in Santa Rosa County. 4.2 TIME OF CONCENTRATION The Time of Concentration is a common parameter required of hydrologic and hydraulic methods. The time of concentration shall be determined by the velocity method for specific project conditions. The velocity method is a segmental approach that cam be used to account for overland, shallow channel, and main channel flows by considering the average velocity for each flow segment, and by calculating a travel time using the following equation: tm: SANTA ROSA: FF 4-1 10 Ti = Li / (60) x Vi Ti = Travel time for velocity segment (i), in minutes Li = Length of the flow path for segment (i), i-n ft Vi = Average velocity for segment (i), in ft/sec The time of concentration is then calculated by summing the individual segment travel times as follows: TC = T1 + T2 + T3 + ... + TL Where: TC = Time of concentration, in minutes TI = Overland flow travel time, in minutes T2 = Shallow channel travel time (typically rill or gutter flow), in minutes TL = Travel time for the last segment, in minutes 4.2.1 Overland Flow The Kinematic Wave Equation developed by Ragan (1971) shall be used for calculating the travel time for overland flow conditions. Figure 4-1 presents a nomograph that can be used to solve this equation, which is express as: tm: SANTA ROSA: FF 4-2 lczO.93 L 06H 06 EXAMPLE: 02 0.4s03 GIVEN: SzOO; n=0.1' LalOOFT; 1=5 IWHR -01 F*w: Ic 7.7 MIN UNMR) -006 lo- 0.06 0-6 c L (FT) 2 6 - -004 -0.4 -003 -0.3 10 3 - oJ02 -02 -20 4 3 2 -30 6- -04 -40 -006 -aof -006 -60 - .10- 0.8- -0000 - -SO -.:-100 - Q006 -004 0.6- - -003 -200 0.4- -0004 -002 - 300 20 -0003 -400 30- .0.002 -001 600 800 40] 1000 60 L)5j)01. MWA. MC Figure 4-1 OVERLAND FLOW NOMOGRAPH T1 0.93 (LO.6 NO.6)/(IO.4 SO.3) Where: T1 Overland flow travel time, in minutes L Overland flow length, in ft N Surface roughness coefficient for overland flow (see Table 4-1) I Rainfall intensity, in inches/hr, corresponding to the design storm frequency storm S Average slope of the overland flow path, in ft/ft It should be noted that the surface roughness coefficient values shown in Table 4-1 were determined specifically for overland flow conditions and are not to be used for conventional open channel flow calculations. TABLE 4-1 ACCEPTABLE "N" VALUES FOR USE IN THE KINEMATIC WAVE FORMULA Land Use "N" Value Pavement 0.015 Bare Soil (Average Roughness) 0.05 Poor Grass Cover 0.2 Average Grass Cover or Lawns 0.4 Dense Grass Cover or Woodlands 0.6 Forest With Thick Humus/Litter Layer and Dense Undergrowth 0.8 tm: SANTA ROSA: FF 4-4 4.2.2 Shallow Channel Flow Average velocities for shallow channel flows, also known as swale and gutter flows, can be evaluated using Mannings Equation or Figure 4-2. 4.2.3 Main Channel Flow Average velocities for main channel flows, also known as ditch or stream flows, should be evaluated using Mannings Equation or appropriate modelling techniques. 4.3 STORMWATER RUNOFF This section outlines the approved methods available to the Engineer of Record for estimating storm runoff. Of the many methods available, this Manual makes use of four, which have proved convenient and reliable. In addition, other recognized methods may be used if their applicability can be demonstrated to the satisfaction of the County Engineer. 0 The Rational Method (For Areas of Ten (10) Acres or Less) 0 The Modified Rational Method For Volume and Hydrograph Generation (For Areas of Ten (10) Acres or Less) 0 SCS Synthetic Unit Hydrograph Method tm: SANTA ROSA: FF 4-5 .50 f I I T I I Ii I I II I II I I I I I A Lff I I T I I F I I II I I II I II I I .ZO .10 .06 T T fT 4A .04 I I tffTI T TIF I @A i i F I f 1A I I F I i I IF I1A ilt 1A f71 111 A !A i Hill .02 ell .01 A I It I .005 1 2 4 6 10 20 Average velocity, ft/sec Figure 4-2 SHALLOW CHANNEL FLOW VELOCITY source: FDOT Drainage Manual (1987) tm: SANTA ROSA: FF 4-6 0 Santa Barbara Urban Hydrograph Method These methods should be used to calculate the discharge and runoff volumes resulting from rainfall events of specified frequency and duration. 4.3.1 Rational Method The Rational method uses an empirical equation to estimate peak discharge and has gained wide acceptance because of its simplicity. This method relates peak rate of runoff or discharge to rainfall intensity, surface area and surface characteristics. The Rational Method tends to over estimate the rates of flow for larger areas, therefore the application of a more sophisticated runoff computation technique is usually warranted on large drainage areas. A detailed discussion of this method is presented in FDOT's Drainage Manual, Volumes 2A - Procedures (1987). 4.3.2 Modified Rational Method For small drainage areas (less than 10 acres) a inflow hydrograph can be developed by utilizing the Modified Rational Method. Using the project drainage area (A), the project runoff coefficient (C), and the rainfall intensities (I) taken from the FDOT Zone 1 intensity-duration-frequency curves, an inflow hydrograph can be developed. tm: SANTA ROSA: FF 4-7 4.3.3 Synthetic Unit Hydrograph Method The unit hydrograph of a drainage basin (watershed) is defined as the runoff hydrograph which represents the time response to one (1) inch of rainfall excess (runoff) distributed uniformly over the basin during a specified period of time (time step). The SCS has derived general dimensionless unit hydrographs from a large number of observed unit hydrographs for watersheds of various sizes and geographic locations. Once the time to peak and peak flow for a particular unit hydrograph have been defined, the entire shape of the unit hydrograph can be estimated using the appropriate dimensionless unit hydrograph. A more detailed analysis of the unit hydrograph procedure can be found in "SCS National Engineering Handbook, Section 4, Hydrology, Revised 1969" and other publications. 4.3.4 Santa Barbara Urban Hydrograph Method The Santa Barbara Urban Hydrograph Method (SBUH Method) was developed by Stubchaer (1975) for the Santa Barbara County (California) Flood Control and Water Conservation District. In many respects, the SBUH method is similar to some of the time-area-concentration curve procedures for hydrograph computation in which an instantaneous hydrograph in a basin was developed and then routed through an element of linear storage to determine basin response. However, in the SBUH method the final design (outflow) hydrograph is obtained by routing @he instantaneous hydrograph for each time period (obtained by multiplying the various incremental rainfall excesses by the watershed area in acres) through an imaginary linear reservoir with a routing constant which is tm: SANTA ROSA: FF 4-8 re lated to the time of concentration of the drainage basin. As a result, the intermediate process of preparing a ti me- area- concentration curve for the basin is eliminated. 4.4 DESIGN STORM The usual analytical methodology adopted for the design of stormwater management facilities is to evaluate the flooding conditions that would be caused by selected critical rainstorms. The same critical rainstorms are used to evaluate the stormwater runoff impacts occurring due to land use changes due to development within a basin. The four facets which define a particular design storm are (1) the frequency of occurrence, (2) the storm duration, (3) the total volume of rainfall for the particular frequency and duration; and (4) the temporal distribution of that amount over the storm duration. 4.4.1 Rainfall Frequency The 25-year design storm tends to be the most commonly used "extreme" event for stormwater facility design in Florida. Santa Rosa County drainage regulations stipulate its use in design of external subdivision drainage facilities and detention basins. The justification for selecting the 25-year event for stormwater facility design is that it is more conservative than the 10-year design storm typically used for local storm sewer design, but less conservative than the 50- and 100-year events which would require more extensive runoff control measures that would be used infrequently. tm: SANTA ROSA: FF 4-9 4.4.2 Rainfall Duration From various studies of past major rainfall events that have occurred in the southeastern portion of the United States, and in the northwest portion of 4- Florida in particular, it is apparent that a large portion of the total rainfall of most major storms occurs within a 24-hour period. From the design perspective for stormwater conveyances such as ditches, inlets, storm sewers, and culverts, it is the peak rate of runoff that is the critical design factor, not the total volume of runoff. Hence a shorter duration storm event can be utilized in the evaluation and design of these facilities. A 6-hour duration design rainfall will be used for design of ditches, inlets, storm sewers and on-site culverts for projects in Santa Rosa County. In accordance with the design criteria for hydrologic studies which mandates that the duration of the design rainfall should be approximately equal to or greater than the time of concentration of the basin, a 6-hour duration should be sufficient for any application within the County for determination of design peak flow rates. A 24-hour storm will be used to check stormwater attenuation, detention and retention facilities for proper function and response to FDER's "drain-down" requirements. tm:SANTA ROSA: FF 4-10 4.4.3 Rainfall Volume Water Management Districts, excluding the NWFWMD, typically approve the use of the Department of Commerce's Technical Paper No. 40 as a reference for the design storm rainfall volume within the state. FDOT's new Drainage Manual (1987) utilizes this reference in addition to the more recent NOAA Technical Memorandum NWS HYDRO-35 "five to 60-Minute Precipitation Frequency for the Eastern and Central United States" publication to develop its set of rainfall intensity-duration-frequency (IDF) curves. Table 4-2 presents an appropriate set of IDF curves and design rainfall volumes for use within the County. These IDF curves were derived from these sources specifically for the Santa Rosa County. Figure 4-3 presents a family of i ntens i ty-durati on- frequency curves for storms with recurrence intervals of 2-, 3-, 5-, 10-, 25-, 50-, and 100-years. 4.4.4 Rainfall Distribution Peak runoff rates for a small (less than 100 acres in size and less than 30- minute time-of-concentration) urban drainage basin can be determined using the Rational Method. This method requires only a design rainfall intensity which corresponds to the time-of-concentration at the design point for the specified design return period. Table 4-2 presents a set of rainfall intensity- duration- frequency (IDF) relationships for Santa Rosa County to be used in the Rational Method. tm: SANTA ROSA: FF 4-11 15 15 I i f f i I ffl-H + f f f-Hflfl--- 10 10 .2.Ye... 7 3 77 6 6 cc 5 5 Y",F 0 rt-- 10 YOW-- CL ... co ul H SOO y eowww z Z 2 2 T-T -f 4+11- F r%, I z +*i++[ I r 1 10 tI 1 4 .9 7771-1 11 1 1 1111 1 1T 11 1 1 1.I19 U. .8 1111111 11 11 NJ I 111 8 3 -7 1 1 1 1 11 1 111 '< Ir .7 7 6 6 .5 5 4 ZONE 1 4 ++ 4 1 1 11 1 4 4 a -7- .3 3 .2 2 8 10 15 20 30 40 5WO 6 0 2 3 4 5 10 MINUTES HOURS DURATION Figure 4-3 RAINFALL INTENSITY-DURATION-FREQUENCY CURVES 4-13 Since the Rational Method generates design peak flow rates, it is inappropriate to develop design storm hydrographs or determine runoff volumes. For these purposes, or for large basins (greater than 100 acres in size or longer than 30-minute time-of-concentration) an alternate methodology which uses unit hydrograph theory must be used. This method requires a design storm hyetograph which distributes a design storm rainfall volume over its duration at discrete time steps. The 24-hour storm distribution, listed in 30-minute increments in Table 4-3, is the SCS Type II Florida - Modified Distribution. The 6-hour storm distribution presented in Table 4-4 and is broken down into smaller, 10-minute time increments, and should be used to generate design peak flows and hydrographs for applications on which the smallest drainage subbasin being analyzed has a time-of-concentration less than 30 minutes. The 6-hour duration design storm distribution was derived by the methodology originally employed by the SCS to derive the Type 11 Florida-Modified distribution. This procedure, as documented in "Interim Runoff Procedure for. Florida", SCS Florida Bulletin Number 210-1-2, utilizes the rainfall volumes listed in NWS publications HYDRO-35 and TP-40 to obtain a set of design storm rainfall increments for a storm of given recurrence interval and duration. tm: SANTA ROSA: FF 4-14 Table 4-2 RAINFALL INTENSITY, IN/HR (VOLUME, IN.) RETURN PERIOD, YEARS DURATION 2-YR 5-YR 10-YR 25-YR 50-YR 100-YR 5-min 6.60 (0.55) 7.45 (0.62) 8.15 (0.68) 9.10 (0.76) 9.95 (0.83) 10.80 (0.90) 10-min 5.70 (0.95) 6.45 (1.07) 7.10 (1.18) 8.00 (1.33) 8.70 (1.45) 9.50 (1.58) 15-min 4.90 (1.22) 5.55 (1.39) 6.10 (1.53) 6.90 (1.73) 7.55 (1.89) 8.20 (2.05) 20-min 4.30 (1.43) 5.00 (1.67) 5.50 (1.83) 6.35 (2.18) 7.00 (2.33) 7.60 (2.53) 30-min 3.55 (1.75) 4.20 (2.10) 4.70 (2.35) 5.40 (2.70) 6.00 (3.00) 6.55 (3.30) 45-min 2.80 (2.10) 3.35 (2.50) 3.70 (2.80) 4.35 (3.25) 4.85 (3.65) 5.30 (4.00) 1-hr 2.35 (2.35) 2.85 (2.85) 3.20 (3.20) 3.75 (3.75) 4.15 (4.15) 4.55 (4.55) 1.5-hr 1.80 (2.70) 2.25 (3.40) 2.50 (3.75) 2.90 (4.35) 3.20 (4.80) 3.55 (5.35) 2-hr 1.50 (3.00) 1.90 (3.80) 2.10 (4.20) 2.40 (4.80) 2.70 (5.40) 2.95 (5.90) 3-hr 1.10 (3.30) 1.40 (4.20) 1.60 (4.80) 1.80 (5.40) 2.05 (6.10) 2.25 (6.70) 4-hr 0.90 (3.60) 1.15 (4.60) 1.30 (5.20) 1.52 (6.10) 1.70 (6.80) 1.90 (7.60) 6-hr 0.68 (4.08) 0.87 (5.25) 1.00 (6.00) 1.17 (7.00) 1.30 (7.80) 1.45 (8.70) 9-hr 0.51 (4.60) 0.66 (5.95) 0.75 (6.75) 0.88 (7.90) 1.00 (9.00) 1.10 (9.90) 12-hr 0.42 (5.10) 0.54 (6.50) 0.62 (7.50) 0.73 (8.80) 0.81 (9.70) 0.91 (10.9) 18-hr 0.31 (5.60) 0.41 (7.40) 0.46 (8.30) 0.55 (9.90) 0.62 (11.2) 0.69 (12.4) 24-hr 0.25 (6.00) 0.33 (7.80) 0.38 (9.10) 0.45 (10.7) 0.50 (12.0) 0.57 (13.6) SOURCES: (1) NOAA Technical Memorandum NWS HYDRO-35, FIVE TO 60 MINUTE PRECIPITATION FREQUENCY FOR THE EASTERN AND CENTRAL UNITED STATES, 1977. (2) Technial Paper No. 40, RAINFALL FREQUENCY ATLAS OF THE UNITED STATES FOR DURATIONS FROM 30 MINUTES TO 24 HOURS AND RETURN PERIODS FROM I TO 100 YEARS, 1961. (3) STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION, DRAINAGE MANUAL, VOLUME 2, PROCEDURES, 1987. tm:SANTA ROSA:Z TABLE 4-3 DESIGN STORM RAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL-- FRACTION OF TOTAL FRACTION OF TOTAL TIME, HRS. 24-HOUR RAINFALL 24-HOUR RAINFALL 0.0 0.000 0.000 0.5 0.006 0.006 1.0 0.012 0.006 1.5 0.019 0.007 2.0 0.026 0.007 2.5 0.034 0.008 3.0 0.042 0.008 3.5 0.050 0.008 4.0 0.059 0.008 4.5 0.068 0.009 5.0 0.078 0.010 5.5 0.088 .0.010 6.0 0.099 0.011 6.5 0.110 0.011 7.0 0.122 0.012 7.5 0.135 0.013 8.0 0.149 0.014 8.5 0.164 0.015 9.0 0.180 0.016 9.5 0.200 0.020 10.0 0.224 0.024 10.5 0.253 0.029 11.0 0.289 0.036 11.5 0.343 0.054 12.0 0.593 0.250 12.5 0.689 0.096 13.0 0.731 0.042 13.5 0/763 0.032 14.0 0.789 0.026 14.5 0.811 0.022 15.*o 0.829 0.018 15.5 0.844 0.015 16.0 0.858 0.014 16.5 0.871 0.013 17.0 0.883 0.012 tm: SANTA ROSA: FF 4-15 TABLE 4-3 (Continued) DESIGN STORM RAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TOTAL TIME, HRS. 24-HOUR RAINFALL 24-HOUR RAINFALL 17.5 0.894 0.011 18.0 0.905 0.011 18.5 0.915 0.010 19.0 0.925 0.010 19.5 0.934 0.009 20.0 0.943 0.009 20.5 0.951 0.008 21.0 0.959 0.008 21.5 0.967 0.008 22.0 0.974 0.007 22.5 0.981 0.007 23.0 0.988 0.007 23.5 0.994 0.006 24.0 1.000 0.006 TOTAL 1.000 tm: SANTA ROSA: FF 4-16 TABLE 4-4 DESIGN STORKRAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TdTAL TIME, HRS. 6-HOUR RAINFALL 6-HOUR RAINFALL 0 0.000 0.000 0.17 0.010 0.010 0.33 0.020 0.010 0.50 0.030 0.010 0.67 0.041 0.011 0.83 0.053 0.012 1.00 0.065 0.012 1.17 0.078 0.013 1.33 0.092 0.014 1.50 0.107 0.015 1.67 0.123 0.016 1.83 0.140 0.017 2.00 0.159 0.019 2.17 0.181 0.022 2.33 0.209 0.028 2.50 0.244 0.035 2.67 0.290 0.046 2.83 0.370 0.080 3.00 0.559 0.189 3.17 0.672 0.113 3.33 0.732 0.060 3.50 0.772 0.040 3.67 0.803 0.031 3.83 0.828 0.025 4.00 0.848 0.020 4.17 0.866 0.018 4.33 0.882 0.016 4.50 0.897 0.015 4.67 0.911 0.014 4.83 0.924 0.013 5.00 0.937 0.013 5.17 0.949 0.012 5.33 0.960 0.011 5.50 0.971 0.011 5.67 0.981 0.010 @.83 0.991 0.010 6.00 1.000 0.009 TOTAL 1.000 tm:SANTA ROSA:FF 4-17 7 SECTION FIVE SE C Section 5 ADMINISTRATIVE GUIDELINES 5.1 GENERAL Santa Rosa County has adopted administrative guidelines in the form of procedures and regulations for the administration and enforcement of the Stormwater Management Ordinance. These procedures and regulations cover the submission and review, and permitting of stormwater management facilities within Santa Rosa County. 5.2 APPLICATIONS (To be developed by Santa Rosa County) 5.3 APPLICATION PACKAGES (To be developed by Santa Rosa County) 5.4 REVIEW PROCEDURES AND TIME FRAMES (To be developed by Santa Rosa County) 5.5 ISSURANCE OF PERMITS (To be developed by Santa Rosa County) tm:SANTA ROSA:HH 5-1 APPENDIX A SANTA ROSA COUNTY STRUCTURE INVENTORY DIRECTORY BY BASIN AND SUBBASIN BASIN 01: ESCAMBIA RIVER BASIN SUBBASINS: LOCATION NO./SIZE/TYPE 01 BEALE CREEK -905 SR 197-A 1-36" RCP -910 SR 197-A 1-30" RCP -915 SR 197-A 1-36" RCP -920 SR 197-A 1-30" RCP -925 SR 197 8'x3' Box Culvert -930 SR 197-A 2-30" RCP -935 SR 184 1-36" CMP -940 SR 184 3-36" RCP -945 SR 184 2-8'x4' Box Culvert -950 SR 184 2-48" RCP -955 SR 184 2-30" RCP -960 SR 184 1-30" RCP -965 SR 184 1-3611 CMP -970 SR 184 1-36" RCP -975 SR 197 1-30" RCP -980 SR 197 8'x4' Box Culvert -985 SR 197 8'x4' Box Culvert 02 TENMILE CREEK -005 SR 184 3-10'xlO' Box Culvert -010 SR 184 4-10'x3' Box Culvert -015 SR 184 2-12'x5' Box Culvert -905 SR 184 8'x4' Box Culvert -910 SR 184 2-10'x5' Box Culvert -915 SR 197 6'x4' Box Culvert -920 SR 197 2-40" & 1-36" RCP -925 SR 197 1-2411 RCP -930 SR 197 1-24" RCP -935 SR 197 1-3' RCP -940 SR 197 1-3011 CMP 03 THOMAS CREEK -905 SR 197 30"x48" CMPA -910 SR 197 1-30" CMP -915 SR 197 30"x48" CMPA -920 SR 197 2-24" CMP Continued SANTA ROSA BASIN 01: ESCAMBIA RIVER BASIN (concluded) SUBBASINS: LOCATION NO./SIZE/TYPE 04 MOORE CREEK -005 SR 164 2-8'xlO' Box Culvert -010 SR 197 8'xl2' Box Culvert -015 Bell Creek 30'x3l Bridge & SR 182 -905 SR 164 2-24" -910 SR 164 1-30" RCP -915 SR 197 2-4'x6' Box Culvert -920 SR 182 2-2411 RCP -925 SR 182 2-24't RCP -930 SR 182 2-24" RCP -935 SR 182 1-3011 RCP 05 CAMPBELL CREEK No structures identified 06 HOLLY CREEK -005 SR 4 U -010 SR 4 U -015 SR 4 U -020 SR 4 U -025 SR 4 U -030 Holly Creek U & unnamed road -035 County Line U -905 SR 197 1-3611 RCP -910 SR 4 1-36" RCP -915 SR 4 3-4'x8' Box Culvert -920 SR 197 1-3611 RCP -925 SR 197 1-30" RCP BASIN 02: ESCA14BIA BAY COASTAL REGION SUBBASINS: 01 BARNETT MILL CREEK -005 SR 10 & ? 12'x4' Box Culvert -010 SR 197 24"x3O" CMPA -015 SR 197 U -020 Barnett Mill Creek 2-36" - North End -905 SR 197 3-4811 RCP Continued Ilk ow SANTA ROSA -2- BASIN 02: ESCANBIA BAY COASTAL REGION (continued) SUBBASINS: LOCATION NO./SIZE/TYPE 01 BARNETT MILL CREEK (concluded) -910 SR 197 2-36" RCP -915 SR 197 21-,'01@' CMPA -920 SR 197 1- 24' CMP -925 SR 191-A 2-24" RCP -930 SR 191-A 2-54" RCP -935 SR 191-A 1-30" CMP -940 SR 191-A 3-30" RCP -945 SR 191-A 3-36" RCP -950 SR 197 2-2411 CMP -955 SR 197 & SR 10 2-3' RCP -960 SR 10 1-72" RCP -965 SR 10 1-36" RCP -970 SR 197 1-30" RCP -975 SR 197-B 1-30" RCP -980 SR 197-B 1-48" RCP -985 SR 197 1-30" CMP -990 SR 197 1-301, CMP -995 SR 197 1-30" CMP -996 SR 197 1-48" RCP 02 INDIAN BAYOU -005 SR 281 & Mulatto Bridge 98'+xlO+ Bayou -010 SR 281 & Mulatto Bridge 98'+xlO+ Bayou -015 SR 281 U -905 SR 97-A 1-24" RCP -910 SR 191-B 2-24" RCP -915 SR 191-A 3-24" RCP -920 SR 191-A 2-30" RCP -925 SR 281-A U -930 SR 191-A 2-36" RCP -935 SR 191-A 1-36" RCP -940 SR 281 2-24" RCP -945 SR 281 1-36" RCP -950 SR 281 1-36" RCP -955 SR 281-A 1-3611 RCP -960 SR 281-A IO'x6' Box Culvert -965 SR 8 2-30" CMP -970 SR 8 2-24" CMP & 42" Pipe Culvert -975 SR 8 1-3611 CMP -980 SR 8 3-2'x7' Box Culvert Continued SANTA ROSA -3- BASIN 02: ESCAMBIA BAY COASTAL REGION (concluded) 1111ASI11: LOCATION NO./SIZE/TYPE 02 INDIAN BAYOU (concluded) -985 SR 8 6'x8' Box Culvert -986 SR 281 2-2411 RCP -987 SR 281 1-2411 RCP & 1-30" RCP -988 SR 281 4-30" RCP -989 SR 281 Bridge 168'x3O' Indian Bayou -990 SR 281 Bridge 114'x22' Trout Bayou -991 SR 281 3-24" RCP -992 SR 281 3-24 RCP -993 SR 281 2-24" RCP & 1-24" -994 SR 281 Drainage Ditch towards Bay -995 SR 281 Drainage Ditch towards Bay -996 SR 281 5' Box Culvert -997 SR 281 5' Box Culvert BASIN 03: POND CREEK BASIN SUBBASINS: 01 POND CREEK -005 SR 191 Gutter 363'x13' -010 Pond Creek Bridge 300'+xl2'+ -905 Unnamed E. of 1-30" RCP Spencer Olf -910 1-3011 CMP -915 1-3011 CMP -920 2-181100" CMPA -925 SR 191-A 1-3011 CMP -930 SR 191-A 241, V.C. -935 SR 191-A 1-24" RCP -940 SR 191-A 1-2411 CMP -945 SR 191-A 1-30" RCP -950 SR 10 10'x4' Box Culvert -955 SR 97-A 2-24" RCP -960 SR 197-A 1-24" RCP 02 POND CREEK -905 SR 184-A 2-3011 RCP -910 SR 184-A 2-24" RCP Continued SANTA ROSA -4- BASIN 03: POND CREEK BASIN (continued) SUBBASINS: LOCATION NO./SIZE/TYPE 02 POND CREEK (continued) -915 SR 184-A 2-4811 RCP -920 SR 184-A 12'x14' Box Culvert -925 SR 184-A 2-10'x3' Box Culvert -930 SR 191 1-30" RCP -935 SR 191 1-30" RCP -940 SR 191 1-24" RCP -945 SR 191 1-36" RCP 03 POND CREEK -005 SR 191 U & Reader Creek -010 N. off 191 U -015 N. off 191 U -020 Reader Creek U & unnamed road -905 SR 191 1-24" RCP -910 SR 191 2-42" RCP -915 SR 191 1-24" -920 SR 191 1-24" RCP -925 SR 191 1-24" RCP -930 SR 191 1-24" RCP -935 SR 191 1-24" RCP -940 Off 197 & 191 2-30" RCP -945 Off 197 & 191 2-24" CMP -950 Off 197 & 191 3-24" RCP -955 Off 197 & 191 3-24" RCP -960 Off 197 & 191 Bridge 26'x6'+ -965 SR 89 3-24" CMP -970 SR 89 2-241, CMP -975 SR 89 1-241, CMp -980 SR 89 1-24" CMP -985 SR 89 1-24" CMP 04 POND CREEK -905 SR 182 8'x6' Box Culvert -910 SR 182 2-24" -915 SR 197 2-30"x48" CMPA -920 SR 197 1-2411 Continued SANTA ROSA -5- BASIN 03: POND CREEK BASIN (concluded) SUBBASINS: LOCATION NO./SIZE/TYPE 05 POND CREEK -905 SR 197 1-30" -910 SR 197 1-2411 -915 SR 197 1-3011 -920 SR 178 10'x10' Box Culvert -925 SR 178 1-36" -930 SR 89 1-4811 BASIN 04: EAST BAY COASTAL BASIN SUBBASINS: 01 WHITEOAK BAYOU -105 SR 191 3-10' Box Culvert -110 SR 8 U -205 SR 191 8' Box Culvert -210 SR 8 U -905 SR 191 2-24" -910 SR 191 Ditch towards Bay -915 SR 191 1-36" -920 SR 191 1-3011 -925 SR 191 2-2411 -930 SR 191 2-30" -935 SR 8 1-30" CMP & 36" Pipe Culvert -940 SR 191 1-36" -945 SR 191 2-42" -950 SR 191 & SR 8 1O'x3' Box Culvert 02 BLACKWATER BAY -905 SR 191 1-18" RCP w/4 Inlet -910 SR 191 1-36" RCP -915 SR 191 1-401, CMP -920 SR 191 2-24" RCP -925 SR 191 1-2411 Continued SANTA ROSA -6- BASIN 04: EAST BAY COASTAL BASIN (continued) SUBBASINS: LOCATION NO./SIZE/TYPE 03 BLACKWATER BAY -005 SR 8 U -010 @SR 8 U -015 SR 10 1-3011 04 BLACKWATER BAY -005 SR 89 & unnamed Creek 3-42"x6O" CMP -010 Unnamed road off 2'x3O"- SR 89 & SR 184 -015 S. off SR 184 U unnamed road -905 SR 89 1-3011 -910 SR 89 2-36" -915 SR 89 1-30" -920 SR 89 3-78'1 -925 Unnamed road off 2'x24" SR 89 & SR 184 -930 SR 184 Vx24" 05 CATFISH BRANCH No structures identified 06 FUNDY BAYOU No structures identified 07 ALABAMA HOLLOW No structures identified 08 DEAN CREEK -005 SR 87 Dean Creek 80'x9' (to water) -010 SR 87 U -015 Holley Pt. U & unnamed road -020 Unnamed road U -905 SR 87 1-30" -910 SR 87 3-2411 Continued SANTA ROSA -7- BASIN 04: EAST BAY COASTAL BASIN (concluded) 1111AIIII: LOCATION NO./SIZE/TYPE 09 TOM KING BAYOU -905 SR 30 1-3011 -910 SR 399 2-3611 -915 SR 399 2-36" -920 Sr 399 1-30" -925 SR 399 2-30" -930 SR 399 12'x3k' Box Culvert -935 SR 399 1-30" -940 SR 399 1-3011 -945 SR 399 1-24" & 1-36" & 1-42" -950 SR 399 2-3611 -955 SR 399 1-3011 -960 SR 399 1-3611 -965 SR 399 2-3011 -970 SR 399 Bridge 120'x14' -975 SR 399 12'x4' Box Culvert -980 Sr 399 2-2911 -990 Sr 399 8'x3' Box Culvert 10 EAST BAY -905 SR 399 1-36" CMP -910 SR 399 2-36" CMP & 1-18" CMP -915 SR 399 2-30" 11 PENSACOLA BAY No structures identified BASIN 05: BLACKWATER RIVER BASIN SUBBASINS: 01 WRIGHT BASIN -005 SR 191 Bridge 60'+x9+ -010 SR 10 U -011 SR 10 U -015 SR 191 Bridge 98'+xlO'+ -020 SR 191 2-6011 CMP -905 SR 191 Bridge 60'+xO'+ -915 SR 184-A 2-24" RCP -920 SR 191 2-24" RCP -925 SR 191 2-24" RCP Continued SANTA ROSA -8- BASIN 05: BLACKWATER RIVER BASIN (continued) 1111AIIII: LOCATION NO./SIZE/TYPE 01 WRIGHT BASIN (concluded) -930 SR 87 36"x24" Box Culvert -935 SR 89 1-30" RCP -940 SR 89 1-30" RCP -945 SR 89 7'x2' Box Culvert 02 CLEAR CREEK -005 Off of SR 191 Woodpile supported Bridge L15'xl4'+H -010 SR 191 40'+ Wood Bridge 4'+High -015 SR 87-A Bri"jge being replac-@d -020 SR 87 Bridge 100'Lx9'+H -905 Off of SR 191 20'+ Woodbridge 4'+ -910 SR 89 1-@-011 CMP -915 SR 89 1-30" CMP -920 SR 89 2-241, CMP -925 SR 89 3'x2' Box Culvert -930 SR 87 36"x24" Box Culvert -935 SR 87 1-30" RCP -940 SR 87 24"x18" Box Culvert -945 SR 87 1-30" CMP -950 SR 87 1-36" CMP -955 SR 87 1-361, CMP -960 Off of SR. 182 1-36" CMP & SR 87 03 BLACKWATER RIVER -905 SR 191 1-30" -910 SR 191 DBL S'x5' Box Culvert 04 BLACKWATER RIVER -005 Unnamed road 16' Wood bridge 6'+ high -905 Unnamed road 1-60" CMP & 1-36" RCP -910 SR 191 2-36" CMP SANTA ROSA -9- BASIN 05: BLACKWATER RIVER BASIN (concluded) SUBBASINS: LOCATION NO./SIZE/TYPE 05 BLACKWATER RIVER -005 Blackwater River 210' Bridge & BWR State Park -010 Green Br N of BWR Wood Bridge 40'x45' -015 Shingle Bridge 3-2411 & unnamed road -020 BWR & County Line U -025 Wolftrap Branch U -030 Shingle Branch U 06 ATES CREEK No structures identified 07 MIDDLE CREEK -905 SR 4 3'x3' Box Culvert -910 SR 4 3'x2' Box Culvert BASIN 06: COLDWATER CREEK BASIN SUBBASINS: 01 BIG COLDWATER CREEK -005 SR 191 & Coldwater Coldwater River 1300'+ Creek Bridge -010 SR 191 2-36" -015 N. of R.R. 1-36" CMP unnamed road -020 SR 191 12'x4' High wood Box Culvert -025 off SR 87-A 1-30" CMP -905 SR 87-A 12'x4' Box Culvert -910 SR 87-A 2 6'x3' Box Culvert -915 SR 87-A 3-3691 -920 SR 87-A 8'x2' Box Culvert 02 BIG COLDWATER CREEK No structures identified Continued SANTA ROSA -10- BASIN 06: COLDWATER CREEK BASIN (continued) 11BB11111: LOCATION NO./SIZE/TYPE 03 EARNEST MILL CREEK -905 SR 191 1-3011 CMP 04 WOLFE CREEK -005 Wolfe Creek Wood Bridge 10'x5' -010 W. of Baas Brinks Wood Bridge 30'x8' unnamed road 05 EAST FORK COLDWATER CREEK -005 E. Fork off SR 87 Wood Bridge 110'x6'+ -010 SR 4 & Coldwater Coldwater Bridge Creek 425'x25' -015 SR 4 & Thompson Branch 10'x8' Box Culvert -905 SR 4 1-30" CMP -910 SR 4 7'x2' Box Culvert -915 SR 4 4'x3' Box Culvert -920 SR 4 5'x3' Box Culvert 06 EAST FORK COLDWATER CREEK No structures identified 07 DIXON CREEK -905 Off SR 87 2-24" & 2-18" CMP 08 COLDWATER CREEK -005 SR 87 5'x5' Box Culvert -010 SR 87 & Manning Creek Bridge -015 Unnamed road Wood Bridge 40'xlO' S. of SR 399 -020 SR 399 U -025 SR 89 1-30" -905 SR 87 3'x2' Box Culvert -910 SR 87 2-24" -915 SR 87 2-36" SANTA ROSA BASIN 06: COLDWATER CREEK BASIN (continued) 1111AIIII: LOCATION NO./SIZE/TYPE 08 COLDWATER CREEK (concluded) -920 SR 87 1-36" -925 SR 87 8'xlO' Box Culvert -930 SR 87 1-30" -935 OFF SR 87, 1-24" RCP & 1-24" CMP unnamed road -940 unnamed road 2-2411 CMP -945 S. of E. end of Wood Bridge 50'x6' SR 399, unnamed road -950 SR 399 Wood Bridge 30'x6' -955 Unnamed road, 2-18" S. of SR 4 -960 Unnamed road, 10'x3' Box Culvert N. of SR 4 -965 SR 89 3-18" 09 JUNIPER CREEK -005 West Fork & off 4'x8' Box Culvert of 87 & 87-A -010 SR 399 & Juniper 2-10'xIO' Box Culvert Creek -015 SR 178 Bridge 250' -905 SR 87-A 1-2411 -910 SR 399 1-3611 -915 SR 399 8'x4' Box Culvert -920 SR 87 1-48" 10 MARE BRANCH -005 SR 164 Bridge 100' -010 Blackjack Creek Bridge 70' off 164 -015 Off of SR 164 Bridge 50' -020 N. off of 178 Bridge 40' -025 SR 178 & Mare 3-10'x6' Box Culverts Bridge -030 SR 89 & Mare Bridge 20'x3' to water Bridge -905 SR 164 1-2411 -910 SR 164 1-3011 -915 SR 178 1-3011 Continued SANTA ROSA -12- BASIN 06: COLDWATER CREEK BASIN (concluded) SUBBASINS: LOCATION NO./SIZE/TYPE 10 MARE BRANCH (concluded) -920 SR 178 8'xl2' Box Culvert -925 SR 89 1-30" -930 SR 89 1-30" -935 SR 89 1-24" -940 SR 89 10'x8' Box Culvert -945 SR 89 8'xlO' Box Culvert -950 SR 89 1-30" -955 SR 89 8'xlO' Box Culvert 11 COBB BRIDGE -005 West Fork & SR 399 4-8'x12' Box Culvert -010 SR 4 U -015 Off 89 U 12 WEST FORK COLDWATER CREEK -005 SR 197 & Cobb Creek 1-36" -010 SR 197 1-36" -015 SR 4 4'x8' Box Culvert -020 SR 4 Bridge 70' -025 SR 87-A U -030 SR 197 U Ilk- -035 Sr 197 U -905 SR 87-A 3'x8' Box Culvert -910 SR 4 1-24" -915 SR 4 2'x3' Box Culvert BASIN 07: BIG JUNIPER CREEK BASIN SUBBASINS: 01 BIG JUNIPER CREEK -005 Big Juniper Wood Bridge being replaced & unnamed road w/10'x400' -010 West of Juniper on Wood Bridge 25'x4'+ unnamed road SANTA ROSA -13- BASIN 07: BIG JUNIPER CREEK BASIN (continued) SUBBASINS: LOCATION NO./SIZE/TYPE 01 BIG JUNIPER CREEK (concluded) -905 Unnamed road 1-36" CMP -910 Unnamed road 1-3611 CMP 02 ALLIGATOR CREEK No identified structures 03 JUNIPER CREEK -005 Unnamed road U at Maria Brook 04 SWEETWATER CREEK -005 SR 191 Bridge 215'x2l' -010 SR 191 & Pittman 4-36" CMP Creek -905 SR 191 1-30" CMP -910 SR 191 1-36" CMP -915 SR 191 2-30" CMP 05 HOG PEN BRIDGE -005 SR 4 5'x3' Box Culvert -905 SR 4 4'x4' Box Culvert -910 SR 4 1110' 06 JUNIPER CREEK -005 SR 4 & Big Juniper Bridge 300'x28' Creek -010 SR 191 Bridge 175'x4' -015 SR 191 Wood Bridge 75'xIO' -020 Turkey Creek Wood Bridge 40'xIO' & unnamed road -905 SR 191 2-18" -910 SR 191 2-18" -915 SR 191 12'x2' Box Culvert -920 SR 191 8'x4' Box Culvert -925 SR 191 1-30" Continued SANTA ROSA -14- BASIN 07: BIG JUNIPER CREEK BASIN (concluded) SUBBASINS: LOCATION NO./SIZE-/TYPE 07 BIG JUNIPER CREEK -005 SR 191 9'x3' Box Culvert -010 SR 191- 2-3611 -015 SR 191 2-10'x6' Box Culvert -905 SR 191 1-36" -910 SR 191 1-36" -915 SR 191 12'x2' Box Culvert -920 SR 191 1-4211 -925 SR 191 2-36'1 -930 SR 191 1-48" -935 SR 191 1-3011 08 SWEETWATER CREEK -005 SR 4 Bridge 375'x18' -010 SR 4 4'x3' Box Culvert -905 SR 4 2-2411 -910 SR 191 2-7'x4' Wood Box Culvert -915 SR 191 1-361, CMP 09 SWEETWATER CREEK -905 SR 191 2-3611 10 SWEETWATER CREEK No structures identified 11 SWEETWATER CREEK No structures identified BASIN 08: YELLOW RIVER BASIN SUBBASINS: 01 YELLOW RIVER -005 SR 87 & Palmer Bridge 0.9 miles Slough -905 SR 184 2-24" -910 SR 184 & SR 87 2-24" -915 SR 8 1-30" CMP Continued SANTA ROSA -15- BASIN 08: YELLOW RIVER BASIN (concluded) SUBBASINS: LOCATION NO./SIZE/TYPE 02 YELLOW RIVER -905 SR 184 2-6011 CMP -910 SR 184 1-8411 CMP -915 SR 8 2-24" CMP -920 SR 8 1-4811 CMP -925 SR 8 2-24" CMP -930 SR 8 2-24" CMP -935 SR 8 2-24" CMP 03 BOILING CREEK No structures identified 04 YELLOW RIVER -905 SR 8 2'-7'x4' Box Culvert -910 SR 8 1-36" CMP -915 SR 8 1-3011 Cmp 05 GARNIER CREEK -005 SR 8 6'x5' Box Culvert -905 SR 8 2-30" CMP -910 SR 8 1-3611 CMP -915 SR 8 6'x4' Box Culvert BASIN 09: EAST BAY RIVER BASIN SUBBASINS: 01 EAST BAY RIVER -005 East Bay River East Bay River Bridge & SR 87 260'x121 to Water 02 EAST BAY RIVER No structures identified SANTA ROSA -16- BASIN 10: SANTA ROSA SOUND BASIN SUBBASINS: LOCATION NO./SIZE/TYPE 01 ENGLISH NAVY COVE No structures identified 02 ORIOLE BEACH -005 SR 191 32'xlO' Bridge & Oriole Beach -905 SR 30 1-30" -910 SR 30 1-36" -915 SR 30 1-3611 -920 SR 191 3-36" -925 SR 191 3-36" -930 SR 30 1-36" -935 SR 191 2-3011 -940 SR 191 2-24'1 -945 SR 191 1-4811 -950 SR 191 8'x6' Box Culvert 03 WILLIAMS CREEK -905 us 98 6'x5' Box Culvert -910 US 98 10'x6' Box Culvert -915 US 98 6'x3' Box Culvert -920 us 98 2-10'x8' Box Culvert -925 us 98 8x8l -930 US 98 1-30" -935 US 98 1-36" -940 US 98 6'x3' Box Culvert -945 us 98 6'x3' Box Culvert -950 US 98 8'x2' Box Culvert -955 US 98 8'x2' Box Culvert -960 US 98 1-36" -965 us 98 1-30" -970 SR 19 2-36" -975 SR 19 2-24" 04 NAVARRE -905 SR 30 5'x4' Box Culvert -910 SR 30 36" CMP & -915 SR 30 10'x3' Box Culvert -920 SR 30 1-36" CMP -925 SR 30 1-30" CMP Continued SANTA ROSA -17- BASIN 10: SANTA ROSA SOUND BASIN (concluded) LOCATION NO./SIZE/TYPE 04 NAVARRE (concluded) -930 SR 30 1-30" CMP -935 SR 30 1-36" CMP & 36" Pipe Culvert -940 SR 30 1-36" Pipe Culvert -945 SR 30 2-30" Pipe Culvert -950 SR 30 1-36" CMP -955 SR 30 1-36" CMP -960 SR 87 1-3011 SANTA ROSA 9 I i I- C APPENDIX B mmmmmm@ AF B -9 APPENDIX B- I SUMMARY OF CURRENT IDENTIFIED CIP PROJECTS --------------------------------------------------------------------------------------- -------------------------------------------------------------- PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST -------------------------------------------------------------------------------------------------------------------------------------- Escambia River- Basin --------------------- 1 01-05 1.5 miles west of S-164 and Structure Flooding 4 $30, ekelO 8-197 intersection 2 61-05 1.3 miles west of S-164 and Ditch Erosion 1 45 $3,400 S-I'37 intersection 3 01-05 Sandy Hollow, 0.6 miles west Ditch Ercosir.r. 1 46 $11, 700 of S-197 4 01-06 Camors Road & and of E ros i or. 4 Z_ 1 $81,500 existing pavement 5 01 _Q%6 inilas went of High School No Dr-ainage Uutlot 2 43 *5,400 ------------ BASIN SUBTOTAL 132, Q100 Escambia River Coastal Basin ---------------------------- 6 02-01 Charles Street. 0.5 iniles Low Are& - Periodic Flooding 3 33 $30, 600 east of S-I'37 7 02-01 Hamilton Lane Yard/Street Flooding 6 6 $6,700 a 02-01 Floridatown Area Yard/Streat Flooding 7 7 1300, 000 9 02-01 Todd Estates Road Flooding 3 30 $25. elee I el 02-02 Trout Bayou -Howard Circle Yard/Street Flooding 6 9 $7,700 It o2-ei2 Ang i a Dr, i ve Yard/Street Flooding 6 1 el $10,300 - No Side Ditches 12 02-02 Dolphin Road @ R&Ughtor. Road Side Dit ches f' I c-od 3 28 13, 7!fO 13 eta -el.? Pearson Road Side Ditches Flc-c-d and 3 36 s 3 7, soo dc, not Drair. 14 0;:,-02 tic-liday Lane and Rauqhtoro Road frotersertic-ro Floods 5 14 $4,475 -- - ---------------- ----------------------------------- ---- ------- ---- -- - ----------- ----------------------- ------ -- - - - - - ------ - - - ---- - PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ Pored Creek Basin ---------- 7 ----- 15 03-ell Santa Villa Area Yard/Street Flooding 7 6 $437,500 16 03-02 Luther Fowler Road Road Flooding 5 $40,700 fOrifith to Evergreen) 17 03-05 Church on 9-164 Church &red Cemetery Flooding 9 $4, 2" ----------- BASIN SUBTOTAL 0482,400 --------------------------------------------- ------------------------------------------------------- 0 PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCAIIDN DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ East Day Cc-astal Basir, ---------------------- is 04-01 Highland Wood S/D Street Floc-dirog 3 25 $10,750 19 04-01 Hurgaria Estates Street Flooding 3 29 $24,500 20 04-01 S-191, 2 miles South Road S-191 Floods 5 15 $43,975 of Whitaker Bayou 21 04-01 S-191, 3 miles south Rrad 5-191 Floods 5 17 $23, 400 of Whitaker Bayou 22 04-01 Dickerson City Inadequate Ditches and 3 35 $34,975 Culverts 23 04-01 Hwy. 191-C Water Standing ir, Ditches and 3 24 *7,600 Discharge affected by Tidal Flue. 24 04-02 Levore Street Flooding - Ditches do not 3 37 $313,610 Dr-a i re 25 04-03 Word Basin Road Sedimerst Build up ors 5 16 $18,750 US-87 frorn Adjoining Clay Road 26 04-08 Holley Pit Road Clay Rood Flooding 3 34 $33, 000 27 04-09 Clay Circle F I ood i ng 3 26 $13, 800 28 04-09 East Day Heights S/D Road and Yard Flooding 3 31 $25,875 29 04-10 Coral Strip Parkway Pond &red Road Flooding 3 33 050,000 30 04-10 Whisper Day Blvd. Flooding 3 38 $40,000 31 04-10 Rosa Del Villa No Drainage Systern 2 44 $21,500 32 04-10 Day Ridge Estates Strur-tUre/Yard Flooding 5 *32,500 33 04-10 Dal Alex Estates Structure/Road/Property 3 $20,250 ------------- BASIN SUDTOrnL $404,685 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ Blackwater River Basin ---------------------- 34 05-01 I:aat Milton in existing S/D Street Flooding 5 19 $59,000 35 05-03 East of Hwy. 137 and Hwy. 91B Road Flooding 5 20 $59,625 Intersection ----------- BASIN SUBTOTAL $118,625 Coldwater Crook Basin --------------------- 36 06-09 Hall Road, east of Hvoy. 164 Erosion around Drainage Pipe 1 47 $12,000 Could Undermine High"ay 37 06-09 H"y. 4 & Jordan Road Structure Flooding a $6,325 ----------- BASIN SUBTOTAL $18,325 Yellow River Basin ------------------ 38 08--04 Shangralm S/D Erosion in Drainsum Ditch 3 40 $55, 5(be ----------- BASIN SUBTOTAL $55,500 East Bay River Basin -------------------- 39 09-01 Navarro East S/D Roadway Intersection Floods 3 22 $5, 5eke ----------- BASIN SUBTOTAL $5,500 PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------- ---------------------------------------------------------------------------------- Santa Rosa Sound Basin ---------------------- 40 10-02 Villa East S/D Street/Lot Flooding 6 12 044, 000 41 10-02 Woodlore S/D Streat/Lot Flooding 6 11 030,000 42 10-02 Savannah Estates Strwet/Lot Flooding 6 13 *1 1 1, 43 10-02 Villa Varlyaw Road Flooding 3 42 *94,000 44 10-02 Blue Horron Cove Road Flooding 3 41 *64,500 4n 10-02 Laurel Drive Street and Pond Flooding 3 32 030, !SO@ 46 10-04 Janot Street and Nina Street Flooding 3 27 016,750 47 10-04 Bandwro S/D Road Flooding 3 23 06,875 ----------- BASIN SUBTOTAL *397,625 ORAND TOTAL COST $3v5559685 *This project is included in FDOT budget APPENDIX B-2 SUMMARY OF POTENTIAL FUTURE CIP PROJECTS CIP Structure Predesign Number Number Description of Work Cost Escambia River Basin 1. 0101-925 Add Parallel 8'x3' Box Culvert $ 30,400 2. 0101-930 New Twin 48" Culverts 22,600 3. 0101-980 New Parallel 8'x4' Box Culvert 34,500 Basin Subtotal $ 87,500 Escambia Bay Coastal Basin 4. 0201-905 New Twin S'x4' Box Culverts $55-000 5. 0201-910 New Twin 48" Culverts 22:600 6. 0201-915 New Twin 48" Culverts 22,600 7. 0201-930 Add Parallel 54" Culvert 18,500 8. 0201-945 New Triple 60" Culverts 48,900 9. 0201-980 New Triple 54" Culverts 41,300 1 g. 0202-915 New Triple 54" Culverts 41,300 Ill. 0202-960 New 40' Bridge 64,800 Basin Subtotal $315,000 Pond Creek Basin 12. 0302-915 Add Parallel 48" Culvert $ 14,200 East Bay Coastal Basin 13. 0401-105 New 40' Bridge $ 64,800 14. 0401-950 New Twin 5'xlO' Box Culverts 77,000 Basin Subtotal $141,800 Blackwater River Basin 15. 0501-020 Add Parallel 60" Culvert $ 22,500 16. 0501-930 New 48" Culvert 14,200 17. 0501-945 New 5'xlO' Box Culvert 47,700 Basin Subtotal $84,400 tm:SR2/MM 8-2 APPENDIX B-2 (Continued) CIP Structure Predesign Number Number Description of Work Cost Coldwater Creek Basin 18. 0601-910 New Twin 4'xB' Box Culverts $ 55,000 19. 0601-915 New Twin 4'x8' Box Culverts 55,000 20. 0601-920 New Twin 4'x8' Box Culverts 55,000 Basin Subtotal $165,000 Yellow River Basin 21. 0802-905 New Twin 4'x8' Box Culverts $- 55,000 22. 0802-905 New 60' Girder Bridge log,000 Basin Subtotal $163,000 Santa Rosa Sound Coastal Basin 23. 1002-945 New Twin 54" Culverts $ 29.1600 COUNTY-WIDE TOTAL: $1,000,500 tm:SR2/MM 8-3 APPEADIX B-3 SUMMARY OF REVENUE NEEDS FOR PROGRAM IMPLEMENTATION ------------------------------------------------------------------------------------------------------------------------ Program Calendar Identified Repair and Operations I Strategic Potential Total Year Year CIP Replacement Mai ntenance Basin Future CIP Funding Projects Costs Costs Studies Projects Required --------------------------------- -------------------------------------------------------------------------------------- 1988 sm, on $25, ON $ 1215. ON $352, ON 1389 $2&7, w $25, ON $130, ON S357,@W 3 1990 $2021, ON $30, ON $135, ON $75, @N $442, ON 4 1991 $,-&J, we $35, NO $140, ON S75,@OO s4s" ON 5 1992 sm, ON $49, ON $145, ON $75, M $462, M 6 1993 sm,m $45, ON $150, see $75, ON $472, ON 7 1994 $,n2, ON $50, NO S155,900 $75, ON $482, ON 8 19ri s 2w, @@@ $55, ON S 160, ON $755, ON $492, w 9 19% sm" on $65, ON $165, M $50. ON sws, ON I@ 1997 $,-R, on $75, W $170, NO $50, ON $497, M It 1998 $85, ON S 1 75, ON $5@, ON $115. ON $425, ON 12 1999 $95, @OO S180'em $50. ON $115, ON $440,0e@ 1 3 2W S 105, ON $I 8-J, ON $50, ON $1 1 51 0@0 S455,0@0 1 4 2001 $120, W $190, on $50, NO $115'em $475, ON I f 2@02 $135, ON $ I 9-J, we $50, ON $115, M $495, M 1 6 2903 $150, OM $200, NO $115,@m $465, @00 1 7 21004 $165, M S2005, ON $115, ON $485, @@@ I 8 2005 $180,000 $210, ON $115, ON $5055, ON 1 9 110% von, on $21 5, ON $115, ON $530. ON J 20 2@07 $220,00 $22@, me $115, ON $5555, ON ------------------------------------------------------------------------------------------------------------------------ Total Funds Required $2, 020, ON $1,9N'm $3,450,900 $8", on $1, I5@, ON $9, 320, OM Percent of Total Need 101.67% 20.39% 37. 02-1% 8.56% 110.34% 1 00. on 0 C APPENDIX C AF , :cD -0 I SANTA ROSA COUNTY STORMWATER MANAGEMENT ORDINANCE PRELIMINARY DRAFT OCTOBER 16, 1987 Article I OVERVIEW 1.01 TITLE This Ordinance shall be known as "The Stormwater Management Ord,inance of Santa Rosa County, Florida." 1.02 AUTHORITY This Ordinance is adopted pursuant to the General Laws of the State of Florida, and all provisions and sections contained herein shall be construed as having been adopted in the interest of public health, safety and general welfare of the people of Santa Rosa County, Florida. 1.03 SCOPE This ordinance amends and supplements the following ordinances: 1. (Subdivision Ordinance) 2. (Zoning Ordinance) 3. (Building and Building Regulations Ordinance) 4. (Plumbing Ordinance) tm: SANTA ROSA: J 1-1 1.04 INTENT It is the intent of this Ordinance to allow landowners reasonable use of their property while protecting surface and groundwater resources of Santa Rosa County by insuring that stormwater run-off peak rates and pollution loads after development should approximate existing- pre- development conditions and that precautions are taken to prevent erosion, sedimentation, flooding and water pollution. 1.05 JURISDICTION The area subject to this Ordinance shall be the unincorporated area of Santa Rosa County, Fl orida and all discharges entering the County's system(s) originating in areas outside the unincorporated area of the County. tm:SANTA ROSA:J 1-2 Article II DEFINITIONS For the purpose of this ordinance, the following definitions shall apply:.-. 2.01 Adverse Impacts - any modifications, alterations or effects on a feature or characteristic of water or flood prone lands including their quality, quantity, hydrodynamics, surface area, species composition, living resources, aesthetics or usefulness for human or natural uses which are or potentially may be harmful or injurious to human health, we lfare, safety or property, to biological productivity, diversity, or stability or which unreasonably interfere with the enjoyment of life or property, including outdoor recreation. The term includes secondary and cumulative as well as direct impacts. 2.02 Applicant - person applying for or one granted a permit to proceed with a project (may be used synonomously with developer and owner). 2.03 Channel - a natural or artificial watercourse of perceptible extent, with a definite bed and banks to confine and conduct continuously or periodically flowing water. Channel flows thus is that water which is flowing within the limits of the defined channel. 2.04 Coastal High Hazard Zone - area(s) subject to high velocity waters, including but not limited to, hurricane wave wash, designated on Federal Insurance Rate Maps as Zones VI-30. tm:SANTA ROSA:K 2.05 Critical Duration - means, for a given frequency, the duration storm event (between I-hour and 10-days) that results in the largest Stormwater discharge peak rate and/or net stormwater volume to be stored (post- improvement runoff less pre-improvement runoff). 2.06 Detention - storm runoff collected and stored for a short period of time and then released at a rate much less than the inflow rate. 2.07 Developer - any person who acts in high own behalf or as the agent of an owner of property,and engages in alteration of land or vegetation in preparation for construction activity. 2.08 Development - any Iaction in preparation or construction activity which results in an alteration of either land or vegetation. 2.09 Development Permit - permit issued by the County which is needed before any development operations can be started (including clearing, grubbing, grading, dredging, filling, excavation, or any other development operations). 2.10 Discharge - volume of fluid per unit time flowing along a pipe or channel from a project, site, stormwater management facility, basin, discharge or outfall point. 2.11 Stormwater Management - a general term applied to the removal of surface or subsurface water from a given area either by gravity or by pumping, tm: SANTA ROSA: K 11-2 commonly applied herein to surface water (may be used synonomously with drainage). 2.12 Stormwater Management System - the surface and subsurface system for the removal of water from the land, including both the natural elements of streams, marshes, swales and ponds, whether of an intermittent or continuous nature, and man-made elements which include culverts, ditches, channels, storage facilities, and the storm sewer system. 2.13 Elevation height -in feet above mean sea level references to the USC&GS (N.O.S.). 2.14 Engineer means a Professional Engineer registered in Florida pursuant to the provisions of Chapter 471, Florida Statutes, who as appropriate is competent in the fields of hydraulics, hydrology, stormwater management of stormwater pollution control. 2.15 Erosion - the general process whereby soils are moved by flowing surface or subsurface water. 2.16 Facility - means all man-made or natural features within a development project or the County's right-of-way or easement including, but not. limited to curbs, gutter, swales, ditches, canals, channels, culverts, pipes, retention areas and detention areas. Facility thus includes but is not limited to anything sto,rmwater will run on or through. tm: SANTA ROSA: K 11-3 2.17 Flood - a temporary rise in the level of rivers, streamsi watercourses, ponds and lakes which results in inundation of areas not ordinarily covered by water. 2.18 100-Year Flood - a flood which has the statistic'al probability of occurring once every 100 years or having a one (1) percent chance of occurring each year. 2.19 Flood Plain - the land adjacent to a watercourse or body of water which has been or may be-covered by flood water including but not limited to the 100-year flood. 2.20 Flood Prone Lands - lands which are subject to being covered by water (1) including the flood plain associated with the 100-year flood, (2) those lands delineated as the Coastal High Hazard Zone, and (3) those lands *frequently subject to inundation by storms with design frequencies of 5- years to 25-years due to frequent small localized flooding problems. 2.21 Flood-Proofing - a combination of structural provisions, changes, or adjustments to properties and structures subject to flooding primarily for the reduction of elimination of flood damages to properties, water and sanitary facilities, structures, and contents of building. 2.22 FloodwU - the normal channel of a watercourse and the adjacent land areas that must remain unobstructed to convey the regulatory flood tm: SANTA ROSA: K 11-4 discharge without raising flood elevations above specified levels as determined in Article IV. 2.23 Hydrologic and Hydraulic Study - an engineering study to determine rates, volumes, and distribution of storm runoff, to evaluate the performance of designed stormwater facilties, and to analyze the effect of development project discharge on the County's and/or other private downstream watercourses and water bodies. 2.24 Impervious Surface @-- a surface which has been compacted or covered with a layer of material so that it is highly resistant to infiltration by water. It includes surfaces such as compacted sand, shell material, lime rock, or clay, as well as most conventionally surfaced streets, roofs, sidewalks, parking lots and other similar structures. 2.25 Obstruction - any dam, wall, wharf, embankment, levee, dike, pile, abutment, projection, excavation, channel rectification, bridge, conduit, culvert, building, wire, fence, rock, gravel, refuse, fill, structure, or matter in, along, across, or projecting into any channel, watercourse, or flood plain area which may impede, retard, or change the direction of the flow of water, either in itself or by catching or collecting debris carried by such water, or that is placed where the flow of water might carry the same downstream to the damage of life or property. 2.26 Predeveloped Conditions - tho se conditions which existed before any individual, firm, corporation, government agency, business trust, estate, tm: SANTA ROSA: K H-5 trust, partnership, association, two or more persons having a joint or common interest, or any other legal entity initiated any development or construction activity which results in an alteration of land or vegetation. 2.27 Project - the particular structures, pavements and improvements to a site proposed by applicant on a particular land area which may be part of a common plan of development and shall include the subdivision of land. 2.28 Receiving Bodies of Water - any water bodies, watercourses or wetlands into which surface water flow either naturally, in man-made ditches, or in a closed conduit system. 2.29 Retention - storm runoff collected and stored with no direct surface water release after the storm runoff has ended. 2.30 Runoff - amount of stormwater from which flows from a catchment area past a given point over a certain period. It is total rainfall, less infiltration and evaporation losses. 2.31 Sediment - fine particulate material, whether mineral or organic, that is in suspension or has settled in a water body or watercourse. 2.32 Site Plan - the plan required to acquire a development, construction, building or stormwater permit which shows the means by which the developer will conform with applicable ordinances and provide the flow tm: SANTA ROSA: K 11-6 attenuation and water quality treatment required in this Stormwater Management Ordinance. 2.33 Storage Facility Study - engineering study to determine if retention and/or detention storage facilities are needed to control storm--runoff from a development, evaluate the proper size, and determine their resultant impact on flow attenuation and/or water quality treatment. 2.34 Subdivide - the division of lands comprising one acre or more in total size into lots, blocks, parcels, tracts or other portions, however designated, so as to comprise three (3) or more such to the acre, or, the division of lands into lots, blocks, parcels, tracts or other portions, however designated, so as to provide for or necessarily require the establishment or extension of streets, alleys, or other rights-of-way. 2.35 Swale - a manmade trench which: (a) has a top width-to-depth ratio of the cross-section equal to or greater than 6:1, or side slopes equal to or greater than 3 feet horizontal to I foot vertical; (b) contains contiguous areas of standing or flowing water only following a rainfall event; and, (c) is planted with or has established vegetation suitable for soil stabilization, stormwater treatment, and nutrient uptake; and (d) is designed to take into account the soil ero dibility, soil percolation, slope, slope length, and drainage area so as to prevent erosion and reduce pollutant concentration of any discharge. tm: SANTA ROSA: K 11-7 2.36 Watercourse - any natural or artificial channel , ditch, canal , stream, river, creek, waterway or wetland through which water flows in a definite direction, either continuously or intermittently, and which has a definite channel, bed, banks or other discernible boundary. 2.37 Water Body - any natural or artificial pond, lake, reservoir or other area which ordinarily or intermittently contains water and which has a discernible shoreline. 2.38 Watershed - means the region draining or contributing water to a common outlet, such as a stream, lake or other receiving area, or, the drainage area that contributes to a point under consideration. 2.39 Wetland - land that is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of vegetation typically adopted for life in saturated soil conditions. tm:SANTA ROSA:K 11-8 Article III STATEMENT OF OBJECTIVES The following are the adopted objectives of stormwater management for the purposes of this Ordinance. 3.01 Protect human life and health. 3.02 Minimize public a n-d private property damage resulting from erosion, sedimentation, flooding and excessive maintenance requirements. 3.03 Regulate use of flood plains for development, fill, dumping, storage of materials, structures, buildings, utilities, or any other work which acting alone or in combination with other existing or future uses will increase flood heights and velocities, upstream or downstream from proposed use, by obstructing flows and reducing storage. 3.04 Regulate development which may, when acting alone or in combination with other developments, create a demand for public investment in flood- control works by requiring protection against flood damage at the time of initial construction and afterwards. 3.05 Ensure, as far as possible, an efficient stormwater management system that will not result in excessive public or private moneys being used for maintenance and replacement of portions of the system. tm:SANTA ROSA:L III-1 3.06 Ensure that the design of the stormwater management system will be consistent with good engineering practice and design. 3.07 Provide temporary and permanent erosion and sediment control measures to protect individuals occupying land adjacent to the downstrealu from proposed developments from being damaged by sediment originating from within or because of the proposed development. 3.08 Control flood plain uses to be consistent with approved land use plans for the flood plain areas and coordinated with plans for the total community to prevent flooding while recognizing that natural fluctuations in water levels are beneficial. 3.09 Provide for development of areas with minimum adverse effects to the natural environment. 3.10 Encourage wise use of the County's economic and fiscal resources through reducing capital expenditures for flooding proofing and storm drainage systems where feasible by routing runoff through swales or other natural retention/detention systems to increase stormwater infiltration, settle suspended solids and remove pollutants. 3.11 Discourage development in areas subject to flooding problems. 3.12 Encourage economical uses and designs in flood plain areas. tm: SANTA ROSA: L 111-2 3.13 Provide a means of placing potential owners, builders, developers, and the general public on notice of existing and potential flood hazards. 3.14 Utilize existing channel capacity for flood flows before using on-site storage or other structural measures. 3.15 Utilize appropriate public open space for both open space uses (parks, recreational uses, etc.) and the temporary storage of excess storm waters. 3.16 Keep the drainage system as natural and aesthetically pleasi ng as possible. 3.17 Develop a comprehensive stormwater management plan for the County to handle storm runoff safely and efficiently. 3.18 Provide for public awareness of the flooding potential. 3.19 Develop interagency relationships with other federal, state, regional, and local governmental units involved in stormwater management in order to solve stormwater problems which cross County boundaries. 3.20 Protect, restore and maintain the chemical, physical and biological quality and quantity of ground and surface water. 3.21 Facilitate recharge of groundwater systems. tm: SANTA ROSA: L 111-3 3.22 Protect, restore and maintain natural salinity levels in estuarine areas. 3.23 Protect, restore and maintain the natural habitats of fish and wildlife and prevent damage to wetlands. 3.24 Ensure the attainment of these objectives by requiring approval and implementation of stormwater management plans for all activities which may have adverse impacts on community waters. tm:SANTA ROSA:L 111-4 Section TV FLOODPLAIN MANAGEMENT 4.1 ESTABLISHMENT OF FLOOD PRONE LANDS CLASSIFICATIONS 4.1.1 Application of this Section - This section applies to the following three general caregories of flood prone lands: (1) All of that area inside the 100-year flood contour elevations; (2) All of that area inside the delineated Coastal High Hazard Zone; and (3) Lands within the County which are subjected to frequent inundation due to topographic contour characteristics when subjected to storms with 5- year to 50-year recurrence intervals. 4.1.2 Delineation of Flood Prone Lands - The recommended procedures to be followed in order to determine the appropriate elevations of the 100-year flood plain, Coastal High Hazard Zone, and other categories of flood prone lands are outlined and discussed in the County's Stormwater Engineering Manual. In addition, this manual lists all approved reports and maps relating to flood prone areas. 4.1.3 Warnings and Disclaimer of Liability - The degree of regulation required by this ordinance is considered to provide a reasonable level of flood protection and is based on engineering and scientific methods of study. Larger floods may occur or flood heights may be increased by man-made or natural causes, such as congested channels and bridge openings constricted by debris. This ordinance does not imply or guarantee that areas outside the delineated flood prone lands or land uses permitted within such a district will be free from flooding or flood damages. This ordinance shall not create liability on the part of the Santa Rosa County or any officer or employee thereof for any flood damages that result from reliance on this ordinance or any administrative decision lawfully made thereunder. tm:SANTA ROSA:M IV-1 4.2 FLOOD PLAIN DISTRICT USES 4.2.1 Permitted Uses - Within the flood plain district the following uses are permitted with the exception that none of these uses, when acting alone or in combination with other uses, are to be allowed to affect adversely the capacity of the channels or floodways 6f any tributary to the main stream and/or the main stream, drainage ditch, or any other drainage facility or system, or in any way affect the free flow of flood waters. This must be documented by appropriate engineering plans and studies as discussed in the County's Stormwater Engineering Manual. Specific uses which- are not permitted in each of the four categories of the flood prone lands classification are specifically listed in the Stormwater Engineering Manual. Determinations of land use suitability will be made.-by the Stormwater Management division. The following list of uses is not intended to be all inclusive but only to given typical examples. a) Agricultural uses such as general farming, pasture, grazing, outdoor plant nurseries, horticulture, truck farming, forestry, and wildcrop harvesting. b) Industrial commercial uses such as loading areas, parking areas, airport landing strips, and other nonstructural uses. c) Private and public recreation uses such as golf courses, tennis courts, driving ranges, archery ranges, picnic grounds, swimming areas, parks, wildlife and nature preserves, target ranges, trap and skeet ranges, hunting and fishing areas, bicycle, hiking and horseback riding trails. 4.2.2 Special Permit Uses - The following uses which involve structures (temporary or permanent), fill, cut, or storage of materials or equipment may be permitted only upon application for a special use permit. Details on such permits are given in Article VI of this tm:SANTA ROSA:M IV-2 ordinance. These uses are also subject to the provisions of Section 4.2.3 which applies to all flood prone lands special-permit uses. The following list of uses is not intended to be all inclusive: a) Uses or structures accessory to open space or Special Permit Uses. b) Circuses, carnivals and similar transient amusement enterprises. c) Drive-in theaters, road-side stands, signs and billboards. d) Extractio.n of sand, gravel and other materials. e) Marinas, boat rentals,, docks, piers, wharves. f) Railroads, streets, bridges, utility transmission lines and pipe lines. g) Storage yards for equipment, machinery or materials. h) Supports for structures (excluding fill) where the flood level of the structure is above the 100-year Flood Contour Elevation but the supports are within the flood plain area. 4.2.3 Standards for Flood Prone Lands Special Permit Uses - The County's Stormwater Manager shall establish appropriate standards and design criteria for designated uses of Flood Prone Lands which shall be promulgated in the County's Stormwater Engineering Manual. The stormwater manager shall annually review and revise the Stormwater Design Manual as required to meet the intent of this Ordinance and accommodate state-of-the-art procedures for stormwater management. tm:SANTA ROSA:M IV-3 Article V NONCONFORMING USES 5.1 A structure or the use of a structure or premises which was lawful abefore passage or amendment of this ordinance but which is not in conformity with the provisions of this ordinance may be continued subject to the following conditions: a) No such use shall be expanded, changed, enlarged, or altered in a way which increases its degree of nonconformity. b) The cumulative alterations, additions and/or repairs to any nonconforming structure shall exceed 25 percent of its value at the time of its becoming a nonconforming use, unless the structure is permanent changed to a conforming use. c) If such use is discontinued for 6 consecutive months, any future use of the building premises shall conform to this ordinance. d) If any nonconforming use or structure is destroyed by any means, including fire, wind damage and floods, to an extent of 25 percent or more of its value at the time it became nonconforming, it shall not be reconstructed except in conformity with the provisions of this ordinance. e) Uses which become nuisances under conditions of prevailing ordinances shall not be entitled to continue as nonconforming uses. f) Except as provided in Section 5.1, any use which has been permitted as a special permit use shall be considered a conforming use. tm: SANTA ROSA:N V-1 g Any alteration, addition, or repair to any nonconforming structure which would result in substantially increasing its flood-damage potential is prohibited. h) The County shall prepare a list of those nonconforming uses which have been flood-proofed or otherwise adequately protected in conformity with Section 10.3.5 (1) - (5). This list shall be presented to the Board which may issue a certificate to the owner stating that as a result of these corrective measures such uses are in conformity with the provisions of this ordinance. i) If the restrictions placed ort a particular use change (e.g., lowering of the 100-year Flood Contour Elevation), a certificate will be issued to the owner stating that as a result of these measures sucK use is in conformity with the provisions of this ordinance. tm:SANTA ROSA:N V-2 Article VI STORMWATER IMPROVEMENTS 6.1 IMPROVEMENTS REQUIRED If the required hydrologic and hydraulic studies reveal that the proposed development would cause increased flood stages so as to increase the flood damages to existing developments or property, or increase flood elevations beyond the vertical limits set for the delineated flood prone lands, then the development permit shall be denied unless one or more of the following requirements are met: a) On-Site Storage - Provide on-site storage for the increased volumes of stormwater that results from the proposed development, and provide a release mechanism to limit the storm runoff peak rate and timing from the storage facility to that which would have been expected from the development site under natural or predeveloped conditions for all design floods which have an adverse effect on existing drainage, up to and including the 100-year flood. Limit the 100-year flood runoff peak from the development so that the vertical limits of the flood prone lands are not exceeded. b) Off-Site Storage - Provide or contribute appropriate funds for the construction of off-site storage facilities that will control storm runoff so that the limits of the flood plain district are not exceeded and upstream and downstream property is not damaged by increased storm runoff. In using off-site storage, an engineering tm: SANTA ROSA: 0 VI-1 study must be done to show that property located between the proposed development and the storage facilities will not be damaged by increased runoff. c) Ipprovements of Existing Drainage System - Improve or contribute funds to improve the existing drainage system, without @ausing damage to upstream and downstream property or increase flood elevations beyond the vertical limits set for the delineated flood prone lands, to safely accommodate the increased runoff from the proposed development. Care must be exercised in utilizing this option so that the natural environment of the existing drainage system is not unduly harmed. 6.2 COST OF DRAINAGE IMPROVEMENTS The following requirements will determine the appropriate contribution of drainage improvement costs resulting from the proposed development. 6.2.1 If all the proposed drainage improvements are contained within and are solely for the benefit of the proposed development, then the total cost of these improvements will be borne by the developer of the proposed development. 6.2.2 If some of the proposed drainage improvements are not contained within the proposed development but are necessitated by and accrue benefits solely to the proposed development then the total costs of these improvements will be borne by the developer of the proposed development. tm: SANTA ROSA: 0 VI-2 6.2.3 If off-site drainage improvements are required as the result of more than one development then the costs of these improvements will be proportional among the developers benefited. Computation procedures for prorating the drainage costs will be determined by the 6.2.4 If a developer wants to develop a portion of an area draining to a proposed off-site drainage improvement, before this improvement is constructed, he may use either of the following options: a) Construct the proposed off-site drainage improvement which will serve the entire area draining to this facility, or b) Provide the funds along with othger benefitted parties for the construction of this drainage facility in lieu of constructing the facility providing that stormwater manager supports this approach. This will allow the developer to proceed with the improvements of his land without damaging the properties of others (assuming, if option B is selected, the County constructs the drainage facility before improvements are made). The County will endeavor to collect, on pro-rata basis, any excess funds plus interest expended by this developer beyond his proportionate share of the cost of such improvements from future properties within the watershed served by such drainage improvements when such properties are development within a period of ten years from the date that the drainage tm: SANTA ROSA: 0 VI-3 improvements are financed or constructed. These funds plus interest, if collected, will be turned over to the initial developer or his assigns. 6.2.5 If the County chooses to provide drainage facilities, the cost of these facilities will be prorated and assessed as a development cost when and if development occurs on the affected lands within a ten year period. tm:SANTA ROSA:O VI-4 Article VII EROSION AND SEDIMENTATION CONTROL 7.1 EROSION AND SEDIMENT CONTROL PLANS Proposed temporary and permanent erosion and sediment control plans shall be submitted with each application for a development permit. These plan shall specify in detail the erosion and sediment control measures to be used during all phases of clearing, grading, filling, construction, and permanent development and accurately describe their, proposed operation. These erosion and sediment control measures shall apply to all features of the construction site, including street and utility installations as well as to the protection of individual lots. In addition, these plans shall be in accordance with the latest specifications and recommendations as outlined in the County's Stormwater Engineering Manual. 7.2 INSTALLATION OF MEASURES No clearing, grading, excavating, filling or otherwise disturbing natural terrain will be permitted until County approved erosion and sediment control measures have been installed except those operations needed to install these measures. All erosion and sediment control measures shall be continuously maintained during the construction phase of the development. tm:SANTA ROSA:P VII-1 Article VIII MAINTENANCE OF STORMWATER MANAGEMENT SYSTEMS 8.1 MAINTENANCE REQUIREMENT The installed system(s) required by this Ordinance shall be maintained by the owner except that the County may select certain systems for County maintenance. The selection of critical areas and/or structures to be maintained by the County shall be recommended to the Board of County Commissioners by the County Engineer. All areas and/or structures to be maintained by the County must be dedicated to the County by plant or separate instrument and accepted by the Board of County Commissioners. The system(s) to be maintained by the owner shall have adequate easements to permit the County right-of-entry to inspect and if necessary, to take corrective action if the owner fails to maintain the system(s). If the owner fails to maintain his system(s), the County Engineer shall give the owner written notice of the nature of corrective action required. If the owner fails, to take corrective action, within thirty (30) days from the date of the notice, the Board of County Commissioners may take the necessary corrective action and place a lien on the property of the owner to recover the costs thereof. 8.1.1 Owner Maintenance - Any portion of the drainage system, including on-site and off-site storage facilities, that is constructed by the developer will be continuously maintained by the owner or owners sub sequent in title of the affected lands unless it is officially accepted by the Board of County Commissioners for County maintenance. In addition, where debris or sediment has accumulated tm: SANTA ROSA: Q VIII-1 in such a manner as to interfere with the free fl-ow of water or adequate functioning of drainage facilities, the Stormwater Management Division shall require the owne r of such properties to clear and remove the debris or obstruction to permit the drainage system to function efficient. 8.1.2 County Maintenance of Private Property at Owner's Expense After notice and reasonable diligent efforts to have the owner of the property remove the debris or obstruction, County forces are hereby authorized to enter upon such drainageways and clear or remove the debris or obstructions. The cost thereof shall be charged to the owner of the property where said debris and/or obstruction was generated. The County shall not charge such costs to the owners where the debris or obstruction within the drainageway. was not generated from his own property or caused by the owner's neg ligence or action. 8.1.3 County Maintenance - The County will maintain County stormwater management facilities according to a planned maintenance schedule to be established by the County's stormwater manager. If it cannot be determined from what property the debris or obstruction was generated, or if the debris or obstruction was not caused by anyone's negligence or action, then the County will arrange for its removal. tm:SANTA ROSA:Q VIII-2 Article IX SUBDIVISION PLATS 9.1 Proposed tentative and final subdivision plats located contiguous- to or within the flood plain district shall not be approved except in accord with the following requirements: 9.1.1 100-Year Flood Contour Elevation - Each plat shall contain a notation clearly stating the 100-Year Flood Contour Elevation as approved and accepted by the'Stormwater Management Division. This elevation shall be designated on the plat by a heavy contour line. 9.1.2 Flood Prone Lands Delineation - Each plat shall contain a notation clearly identifying each of the four categories of the flood prone lands classification where present as determined by the Stormwater Management Division. These areas shall be designated on the plat by suitable shading and contour designation. 9.1.3 Minimum Lot Area Above 100-Year Flood Contour - No lot shall be approved which has less than 7,000 square feet above the level of the 100-Year Flood Contour Elevation. 9.1.4 Drainage Easement - Where a proposed subdivision is transversed by a watercourse, drainageway, canal or stream, appropriate dedication or suitable easement provisions shall be made to accommodate stormwater and drainage through and from the proposed subdivision. Said dedication or easement shall conform substantially with the lines of said watercourse and be of sufficient width or construction, or both, as to be adequate for providing both access and maintenance. tm: SANTA ROSA: R IX-1 The speci f ic details pertaining to the size and extent of dedications or easements are contained in the County's Stormwater Engineering Manual. tm:SANTA ROSA:R IX-2 WORKSHOP REVIEW DRAFT NOVE14BER 1987 Article X PERMITS 10.1 GENERAL STORMWATER MANAGEMENT PERMIT 10.1.1 Activities Requiring a General Stormwater Management Permit No person may" subdivide or make' any change in the use of land or construct or change the size of a structure except as exempted in Section 10.2, without first obtaining a General Stormwater Management Permit from the Department. The following activities may alter or disrupt existing stormwater runoff patterns and, unless exempted by Section 10.2, will require a General Stormwater Management Permit prior to initiation of a project: a) Clearing and/or drainage of land prior to construction of a project; b) Clearing and/or drainage or non-agricultural land for agricultural purposes; c) Converting agricultural land to non-agricultural uses; d) Subdividing land; tm: SANTA ROSA: S X-1 WORKSHOP REVIEW DRAFT NOVENBER 1987 e) Changing the use of land causing a change in natural flow patterns or predevelopment conditions; f) Construction of a structure or substantial alteration size of one or more structures; g) Altering the shoreline or bank of any surface.waterbody; h) Altering of any ditches, dikes, terraces, berms, swales, or other water management facility; i) Redevelopment of a previously developed property. 10.2 ACTIVITIES REQUIRING SPECIAL USE PERMITS 10.2.1 Application for Special Use Permit - Any use listed in this ordinance as requiring a special use permit may be allowed only upon application and issuance of a Special Use Permit by the Board of County Commissioners (hereafter referred to as the Board). 10.2.2 Procedure to be Followed by the Board in Passing on Special Use Permits - Upon receiving an application for a Special Use Permit the Board shall, prior to rendering a decision thereon: a) Require the applicant to furnish as much of the following information as is necessary for determining the suitability of the particular site for the proposed use: tm: SANTA ROSA: S X-2 WORKSHOP REVIEW DRAFT NOVE14BER 1987 (1) Plans showing the nature, location, dimensions, and elevation of the lot, existing or proposed structures, fill, excavation, storage of materials, flood-pr-oofing measures and the relationship of the above to the location of the channel and flood plain district. (2) A typical cross-section showing the channel of the stream, elevation of land areas adjoining each side of the channel, cross-sectional areas to be occupied by the proposed development, 100-Year Floor Contour Elevation, and flood prone lands delineation. (3) Plans showing elevations or contours of the ground; delineated flood prone lands, pertinent structures, fill or storage elevations; size, locations and spatial arrangement of all proposed and existing structures on the site; location and elevations of streets, water supply, sanitary facilities; photographs showing existing land uses and vegetation upstream and downstream, soil types and other pertinent information. (4) A profile showing the slope of the bottom of the channel or flow line of the stream. (5) Specifications for building construction and materials, flood-proofing, filling, dredging, grading, channel improvement, storage of materials, water supply, and sanitary facilities. tm:SANTA ROSA:S X-3 WORKSHOP REVIEW DRAFT NOVEMBER 1987 b) Transmit a copy of the above information to the Stormwater Management Division for their review and comment. c) Based upon the technical evaluation of the Sto-rmwater Management Division, the Board shall determine the specific flood hazard at the site and shall evaluate the suitability of the proposed use in relation to the flood hazard. 10.2.3 Factors Upon Which the Decision of the Board Shall be Based - In passing upon application for special use permits, the Board- shall consider all relevant factors specified in other sections of this ordinance and: a) An evaluation to show that the proposed use will not reduce the capacity of the floodway or increase flood heights beyond those allowed in this ordinance. b) The danger that materials may be swept into other lands or downstream. c) The proposed water supply and sanitation systems and the ability of these systems to prevent disease, contamination, and unsanitary conditions. d) The importance to the community of the services provided by the proposed facility. e) The requirements of the facility for a waterfront location. tm: SANTA ROSA: S X-4 WORKSHOP REVIEW DRAFT NOYENBER 1987 f) The availability of alternative locations not subject to flooding. g) The compatibility of the proposed use with existing development and development anticipated in the near future. h) The relationship of the use to the comprehensive plans and flood prone lands management programs for the County. i) The safety in times of flood of access of ordinary and emergency,.vehicles to the property. j) The expected heights, velocity, duration, rate of rise, and sediment transport of the flood waters expected at the site (if the Board feels this information is nee'ded). k) Such other factors as are relevant to the purpose of this ordinance. 10.2.4 Time for Acting on Application - The Board shall act on an application in the manner described within days from receiving' the application, except when additional information is required by the Board or the Stormwater Management Division to prepare recommendations. The Board shall render a written decision within 60 days from the receipt of such information. 10.2.5 Conditions Attached to Special Use Permits - Upon consideration of the factors listed above and the purposes of this ordinance, the Board shall request the Stormwater Management Division to prepare tm: SANTA ROSA: S X-5 WORKSHOP REVIEW DRAFT NOVEMBER 1987 specific conditions (as required) for the Permit and may attach such conditions to the granting of special use permits or variances as it deems necessary to further the purposes of this ordinance. Following are some examples of such restrictions: a) Modification of waste disposal and water-supply facilities. b) Limitations on periods of use and operation. c) Imposition, of operational controls, sureties and deed restrictions. d) Requirements for construction of channel modifications, dikes, levees an-d other protective measures. e) Flood-proofing measures consistent with the standards and specification for flood-proofing contained in the County's Stormwater Engineering Manual. 10.3 ACTIVITIES ELIGIBLE FOR EXEMPTION FROM PERMITS Any development which will not increase the peak discharge rate, the volume of runoff or deposit additional pollution materials beyond the boundaries of the development shall be exempted from the requirements of this Ordinance. In addition, the following structures and activities are also exempted. tm: SANTA ROSA: S X-6 WORKSHOP REVIEW DRAFT MOVE14BER 1987 a) Single-family residences and their customary accessory structures, provided they are not parts of larger developments. b) Farming activities on agricultural lands, including the farming on forest management lands, assessed under provisions of section 193.461, Florida Statutes of farming activities which are conducted in accordance with a Soil Conservation Service Conservation Plan, or forestry activities conducted in accordance with the Florida Division of Forestry's Silviculture Best Management Practice Manual (latest edition). c) Maintenance work on existing mosquito and arthropod drainage structures for public health and welfare purposes. d) Maintenance, alteration or improvement of an existing structure which will not change the rate, volume or pollution load of stormwater runoff from the site on which that structure is located. e) Construction of any structure or addition to an existing structure creating one thousand square feet or less of new impervious surface. f) Construction or improvements in compliance with the Subdivision Regulations of Santa Rosa County, Ordinance No. as amended provided that: (1) Stormwater management provisions for the subdivision were previously reviewed and approved for a General Stormwater Management Permit; tm: SANTA ROSA: S X-7 WORKSHOP REVIEW DRAFT NOVEMBER 1987 and (2) The development is constructed in acco'rdance wi th. the stormwater management provisions approved on the final plat and approved construction plans which the development' s General Stormwater Management Permit was issued. g) Emergencies requiring immediate action to prevent material harm or danger to persons when obtaining a permit is impractical and would cause undue hardship in protection of property from fire, violent storms, hurricanes or other hazards. A report of the emergency action shall be made to the County's Stormwater Manager as soon as practicable. Any project which qualified as an exemption pursuant to this section will be required to submit a Certificate of Exemption Application, which provides the basis of the exemption, that is signed and sealed by a Registered Engineer. The Stormwater Management will review the application and issue within 21 calendar days of the receipt of a completed applicat.ion, a Certificate of Exemption for all projects meeting the exemption critiera requirements of this Ordinance. tm:SANTA ROSA:S X-8 WORKSHOP REVIEW DRAFT NOVEMBER 1987 10.4 PERMIT APPLICATION PROCEDURES 10.4.1 Preliminary Permit Application Any persons proposing to make any change in the size of any structure or th euse of land:--or to construct a new structure, except as exempted in Section 10.1.2, when in doubt as to whether a Standard Permit Application is necessary, may furnish a completed preliminary application form to the Stormwater Management Department. No fee shall be charged for a preliminary application. The preliminary application form must be filed by the owner/applicant or his/her agent and shall contain the following elements. a) a location map and an aerial photo with contours outlining the project boudaries. b) a statement and sketch expressing the intent and scope of the proposed project. c) a legal description of the property. 10.4.2 Review - The preliminary application shall be reviewed by the County Engineer. Within ten (10) working days after submission of the complete preliminary application, the County Engineer will notify the applicant that either the project is approved, is exempt, or that a permit application must be filed for the project for either a General Stormwater Management Permit or a Special Use Permit. if tm: SANTA ROSA: S X-9 WORKSHOP REVIEW DRAFT NOVEMBER 1987 the county Engineer determines that a permit application must be filed the following considerations shall apply: a) whether the proposed project is exempt. b) whether the proposed project appears to increase the rate or volume of run-off from the existing site. c) whether there are other criteria which would require a General Stormwater Management Permit Application or a Special Use Permit Application. 10.4.3 General Stormwater Management - If a General Permit Application is required for the project, the applicant shall furnish to the Stormwater Management Department five (5) copies of the following: a) Completed General Stormwater Management Permit Application. b) Stormwater Management Plan as described in the Stormwater Engineering Manual. c) Applicable permit fee. d) e) Any other information which the applicant or the County Stormwater Manager believes is reasonably necessary for an evaluation of the proposed development. tm: SANTA ROSA: S X-10 WORKSHOP REVIEW DRAFT NOVEMBER 1987 10.4.4 Special Use Permit Application - If a Special Use Permit is required for the project, the applicant shall furnish to the Stormwater Management Department five (5) copies of the following: a) completed Special Use Permit Application. b) Stormwater Management Plan as described in the Stormwater Engineering Manual. c) Applicabl'e Permit fee. d) e) f) Any other information which the applicant or the County Stormwater Manager believes is reasonably necessary for an evaluation of the proposed development. 10.4.5 Complete Application Required - The County Engineer shall ascertain the completeness of the permit application within five working days of receipt. If there are deficiencies, he shall notify the applicant that further processing of the Standard Permit Application is held in abeyance until the application is complete. 10.4.6 Permit Application Approval Considerations - In approving or denying a Permit Application the County Engineer shall consider the following factors: tm: SANTA ROSA: S X-11 WORKSHOP REVIEW DRAFT NOVEMBER 1987 a) The characteristics and limitations of the soil at the proposed site; b) The existing topography of the proposed site and the extent of topographical changes after development; c) The existing vegetation of the proposed site,and the extent of vegetational changes after development; d) The existing hydrology of the proposed site and the impact of the propo-sed alterations on the existing hydrology; e) The impact the proposed project will have on the natural recharge capabilities of the site; f) The impact the proposed project will have on downstream water quantity and quality and specifically the potential for downstream flooding conditions; g) The plans and specifications of structures of devices the applicant intends to employ for on-site water retention, detention, erosion control and flow attenuation; h) The effect the proposed water retention or detention structures will have upon mosquito and arthropod breeding habitats. i) Conformity of Stormwater Management Plan to the requirements of this Ordinance and the Engineering Procedures and criteria of the Stormwater Engineering Manual. 10.4.7 Permit Review Period - Within ten (10) working days after submission of the completed Permit Application package, the Stormwater Manager tm: SANTA ROSA: S X-12 WORKSHOP REVIEW DRAFT NOVEMBER 1987 shall approve, with or without specified conditions or modification, or reject the proposed Plan and shall notify the applicant accordingly. If the Stormwater Manager has not rendered a decision within ten (10) working days after Plan submission, he shal inform the applicant of the status of the review process and the anticipated completion date. If the Plan is rejected or modified, the Representative shall state the reasons for rejection or modification.@ If the applicant feels aggrieved due to rejection, or modification or delay, he may request a hearing before 'the Santa Rosa County Board of Adjustment and Appeals pursuant to Section 12 of this Ordinance. 10.5 PERMIT FEES If authorized by the Board of County Commissioners, a permit fee may be collected at the time the Application Package is submitted. The permi t fee should reflect only the cost of administration and management of the permitting process. The Board of County Commissioners may establish by resolution, a pro rated fee schedule based upon the relative complexity of the project. The fee schedule may be amended from time to time by resolution of the Board of County Commissioners. Notice of intent to adopt or amend such a resolution shall be published in a newspaper of general circulation in the County at least fifteen (15) days prior to adoption, excluding Sundays and legal holidays. Where work for which a permit is required by the Ordinance is commenced prior to obtaining said tm: SANTA ROSA: S X-13 WORKSHOP REVIEW DRAFT NOVEMBER 1987 permit, the fees herein specified shall be tripled. The payment of such triple fees shall not relieve any persons from fully complying with the requirements of this Ordinance in the execution of the work, nor from any other penalties prescribed herein. tm:SANTA ROSA:S X-14 WORKSHOP REVIEW DRAFT NOVEMBER 1987 Article XI VIOLATION AND PENALTY 11.1 VIOLATIONS Any person, firm or corporation violating any of the provisions of this ordinance shall be deemed guilty of an offense and upon conviction thereof shall be punished as provided by (cite local law section regarding fine, jail time, or both). Each day's continuance.- of a violation shall be considered a separate offense. The owner of any lands or parts thereof, where anything in violation of this ordinance shall be placed or shall exist, and any person who may have assisted in the commission of any such violation, shall be guilty of a separate offense. In any case in which any land is or is proposed to be used in violation of this ordinance or adopted amendment, the County Attorney may, in addition to other remedies provided by law, institute injunction, abatement or any appropriate action or actions to prevent, enjoin, or abate unlawful use. In addition, upon a finding by the Stormwater Management Division that any provisions of this ordinance has been violated, all development and building permits issued to the violator will be suspended until the violation has been corrected to the satisfaction of the Stormwater Management Division. tm:SANTA ROSA:T U-1 WORKSHOP REVIEW DRAFT NOVEMBER 1987 11.2 ENFORCEMENT The County Administrator or his duly authorized representative shall be the Enforcing Officer. If the Enforcing Officer determines --that a project is not being carried out in accordance with the approved Plan or if any project subject to this Ordinance is being carried out without a permit, he is authorized to: a) Issue written notice to the applicant specifying the nature and location of the alleged noncompliance; with a description --of the remedial actions necessary to bring the project into compliance within three (3) working days. Upon request, if weather or other mitigating circumstances prevent timely compliance, the County Representative may extend this three-day compliance period. b) If remedial action is not completed within the compliance period, issue a Stop-Work-Order directing the applicant to cease and desist all or any portion of the work which violates the provisions of this Ordinance. The applicant shall then bring the project into compliance or be subject to immediate revocation of his permit and to penalties set forth in Section 11.1. Any order issued pursuant to subparagraphs a) or b) above shall become final unless the person or persons named herein requests, in writing, an appeal hearing before the Santa Rosa County Board of Adjustment and Appeals no later than fourteen (14) days including Sundays and holidays, tm:SANTA ROSA:T XI-2 WORKSHOP REVIEW DRAFT NOVEMBER 1987 after the date the Stop Work Order is served. Failure to act in accordance with the Order after receipt of written notice shall be grounds for revocation of the Permit. 11.3 INSPECTIONS The owner shall arrange with the County Engineer for scheduling the following inspections: a) Erosion and Sediment Control Inspection: as necessary to -ensure effective control of erosion and sedimentation. Prior to land clearing control measures shall be installed and stabilized between any waters and any areas to be cleared. b) Bury Inspections: prior to the burial of any underground drainage structure. c) Final Inspection: when all work including installation of all stormwater management system facilities has been completed. After inspecting the work the enforcement officer shall approve it or notify the applicant in writing of any failure to comply with the requirements of the approved Permit. Any portion of the work which does not comply shall be corrected within 72 hours by the applicant, or be subject to the penalty provisions of Section 11.1. tm: SANTA ROSA:T XI-3 WORKSHOP REVIEW DRAFT NOVE14BER 1987 11.4 PLAN ADHERENCE The applicant shall be required to adhere to the Plan as approved and permitted. Any changes or amendments to the Plan must be approvedw-by the Stormwater Management Department in accordance with the procedures set forth in Section 10 above. After completion of the project, the County shall require a signed and sealed State of Certification by a Registered Engineer that the project complies with the approved pl ans and speci f i cati ons. Applicant shall grant access to the project to the County so that necessary inspections can be completed in order to ascertain the compliance of the project with the requirements of this Ordinance. tm:SANTA ROSAJ XI-4 WORKSHOP REVIEW DRAFT NOVEMBER 1987 Article XII APPEALS 12.1 In case of dissatisfaction with an act or determination in the exercise of the authority granted herein to the County Departments charged with the administration- of this ordinance, any person, firm or corporation shall have the right to appeal to the County Commission. 12.2 BOARD OF ADJUSTMENTS AND APPEALS a) Makeup of the Board. There is hereby established a Board to be called the "Board of Adjustments and Appeals", whose members shall be appointed by the Board of County Commissioners which shall consist of: the County Attorney or his designee, the County Engineer, the County Planner, the County Building Official, a member of the Association of General Contractors of Northwest Florida, a member of the Home Builders Association of West Florida, a member of the insurance industry, a member-at-large from the construction industry, and an engineer. The County Attorney and County Planner shall be ex-officio, non-voting members of the Board of Adjustments and Appeals. b) Term of office for appointed members shall be two years from date of appointment by the Board of County Commissioners. In the event an tm:SPECS31:U XII-1 WORKSHOP REVIEW DRAFT NOVEMBER 1987 appointed member is unable to serve his full term of office, the Board of County Commissioners shall nominate the representative for the unexpired portion of the term. c) Four members of the Board shall constitute a quorum to make a recommendation to the Board of County Commissioners for varying any provisions of this Ordinance or in modifying an order of the County Engineer. Not less than four affirmative votes shall be r equired for each action. No Board member shall act in a case in which he has a personal interest. d) The Board of Adjustments and Appeals may adopt their own rules and regulations for administrative procedures within the framework of the intent of this Ordinance. The Board of Adjustments and Appeals shall hear any appeal from a decision of any administrative official enpowered under this Ordinance, and shall make recommendations on the appeal to the Board of County Commissioners. tm:SPECS31:U XII-2 WORKSHOP REVIEW DRAFT NOVEMBER 1987 Article XIII BONDING 13.1 The Bonding requirements for subdivision and site plans shall include a cash escrows guarantee which would assure the County that emergency flood and erosion control measures could. be taken by the County at the developer's expense if he did not initiate such action within such period as determined by the Stormwater Management Division. The amount of such bond will be determined by the Stormwater Management Division and will be held by the County until all drainage and erosion control meaures have been accepted by the County. tm:SANTA ROSA:V XIII-1 WORKSHOP REVIEW DRAFT NOVEMBER 1987 Article XIV RELATIONSHIP TO OTHER ORDINANCES AND CHANGES 14.1 REPEAL OF CONFLICTING ORDINANCES The following ordinances or parts thereof are hereby repealed: 14.2 REVISION AND AMENDMENT This Ordinance may be revised, amended or repealed by the the Board of County Commissioners at a regular or special meeting called for such purpose in accordance with the general law. tm:SANTA ROSA:W WORKSHOP REVIEW DRAFT NOVEMBER 1987 Article XV EFFECTIVE DATE In accordance with Section 15.66(2), Florida Statutes, a. certified copy of this Ordinance shall be filed with Florida Department of State by the Clerk of the Board of County Commissioners within ten (10) days after enactment by said Board and shall take effect upon receipt of official acknowledgement from that office that this Ordinance has been filed. PASSED AND ADOPTED by the Board Of County Commissioners of Santa Rosa County, Florida, this day of 1987. Board of County Commissioners Santa Rosa County, Florida CHAIRMAN ATTEST: BY: (SEAL) tm:SANTA ROSA:X XV-1 ANTA ROSA C v UNTY ORMWATER ENGINEERING TECHNICAL MANUAL 00<0 . ......... . . ... . ..... .. ...... ........................ ... .......... . .. .... . ... ... . .......... .. .... .. .... .......... .. ......... .......... .......... .. ........... ......... .... ... . ........ .......... ................ TOM. A. MAT ...... ........... .. ... . ... . ......... .... .................. .. ....... . ......... .. ................... ............ . . ...... . .... . . ............ . ..... AwW:4-'-* . ....... ...... .. .. ...... DECEMBER 1987 epared By: C=Tm Emn= In Association With: MCI SANTA ROSA COUNTY COMPREHENSIVE STORMWATER DEVELOPMENT PLAN TABLE OF CONTENTS SECTION TITLE PAGE 1 INTRODUCTION 1.1 Background 1-1 1.2 Purpose and Scope 1-1 1.3 Authorization 1-2 2 DATA COLLECTION AND DRAINAGE FACILITY INVENTORY 2.1 General 2-1 2.2 Regulations 2-1 2.3 Drainage Facility Inventory 2-3 2.4 Stormwater Atlas 2-4 2.5 Hydrologic Data 2-5 2.6 Hydraulic Data 2-6 2.7 Historical Flooding 2-6 3 GOALS, OBJECTIVES AND POLICIES 3.1 Philosophy 3-1 3.2 Specific Goals, Objectives and Policies 3-2 4 BASIN CHARACTERIZATION 4.1 Basin Delineation 4-1 4.2 Basins Assessment 4-2 4.2.1 Escambia River Basin 4-3 4.2.2 Escambia Bay Coastal Basin 4-4 4.2.3 Pond Creek Basin 4-5 4.2.4 East Bay Coastal Basin 4-6 4.2.5 Blackwater River Basin 4-7 4.2.6 Coldwater Creek Basin 4-8 4.2.7 Big Juniper Creek Basin 4-9 4.2.8 Yellow River Basin 4-10 4.2.9 East Bay River Basin 4-11 4.2.10 Santa Rosa Sound Coastal Basin 4-12 4.3 Drainage Problem Overview 4-13 4.4 Problem Ranking Methodology 4-15 4.5 Problem Summary and Prioritization 4-18 tm: SANTA ROSA-2:BB TABLE OF CONTENTS (Continued) SECTION TITLE PAGE 5 DEVELOPMENT OF DESIGN STORM 5.1 General 5-1 5.2 Design Storm Concept 5-1 5.3 Design Storm Components 5-2 5.3.1 Rainfall Frequency 5-2 5.3.2 Rainfall Duration 5-5 5.3.3 Rainfall Volume 5-6 5.3.4 Rainfall Distribution 5-7 6 FACILITIES ASSESSMENT 6.1 Capacity and Demand Calculations 6-1 6.2 Facility Capacity Analysis 6-1 6.3 Facility Demand and 6-2 Residual Capacity Analysis 7 DEVELOPMENT AND COSTING OF DRAINAGE SOLUTIONS 7.1 General 7-1 7.2 Service Level Definitions 7-1 7.3 Service Level Attainment 7-3 7.4 Analysis of Basin Performance 7-4 8 IMPLEMENTATION PROGRAM 8.1 General 8-1 8.2 Capital Needs Assessment 8-1 8.3 O&M Needs Assessment 8-4 8.4 Implementation Program 3-4 8.5 Program Financing 8-8 APPENDIX A: Drainage Structure Inventory A-1 APPENDIX B: Capital Improvement Program Projects B-1 APPENDIX C: Stormwater Management Ordinance C-1 tm:SANTA ROSA-2:BB 0 Z, .I-- -) C SECTION SE( ONE@ -0 Section 1 INTRODUCTION 1.1 BACKGROUND The County of Santa Rosa has retained Johnson/Creekmore/Fabre (J/C/F) and Post, Buckley, Schuh & Jernigan, Inc., (PBS&J), to prepare the County's Comprehensive Stormwater Development Plan. Funding is being provided by the State of Florida through a grant from the Department of Environmental Regulatio administered by the Department of Community Affairs, Division of Resource Planning and Management. The recently enacted Chapter 9J-5 F.A.C. outlines the minimum criteria requirements of the Local Government Comprehensive Plans and Determination of Compliance Act (Chapter 163, F.S.). The Act generally requires, with respect to stormwater, that an appraisal of a municipal entity's existing system be made, and, based upon projections of future land use, an assessment of future needs. In conjunction with this assessment, Chapter 9J-5 requires that a capital improvement plan be devised with funding means for the necessary stormwater construction improvements. 1.2 PURPOSE AND SCOPE The purpose of this study is to create a plan which will generally meet the minimum requirements of State's Comprehensive Plan, commonly called the tm: SANTA ROSA: 5 Growth Management Act, with regard to stormwater and also provide a vital ongoing planning and implementation tool for satisfying Santa Rosa County's stormwater needs. The work tasks break down into four categories. They are 1) goals, objectives and policies, 2) a stormwater ordinance, 3) existing drainage facility inventory and 4) an assessment of drainage problems including solutions, priorities, costing and implementation incorporating a capital improvements funding program. The scope of this study is county-wide with regard to goals and ordinances but is generally limited to developed portions of the county with regard to problem assessments listed above. 1.3 AUTHORIZATION The Board of County Commissioners of Santa Rosa County, Florida approved and the contract for a Comprehensive Stormwater Development Plan dated January 16, 1987. tm:SANTA ROSA:5 1-2 0 - CSECTION TWO-) 00. --- I Section 2 DATA COLLECTION 2.1 GENERAL To obtain an overview of the existing environments in Santa Rosa County, as much data was readily av.ailable was obtained and reviewed. This included published reports on climatological data, topography and terrain -mapping, roadway network maps, FEMA flood maps and local stormwater management regulations. 2.2 REGULATIONS Two state entities are responsible for stormwater/surface water regulations within Santa Rosa County. The Northwest Florida Water Management District (NWFWMD) is primarily concerned with surface water management. NWFWMD requires permits to construct works which may: 0 Divert or impound water and which are 25 feet or more in height from the natural bed of the watercourse. 0 Will have ari impounding capacity of 100 acre-feet or more; will remove water from a water body with an impounding capacity of 100 acre-feet or more by means of levees, fills, or canals. tm: SANTA ROSA: 9 2-1 0 Which reroute, restrict, or alter a stream which drains an area exceeding five square miles. All other surface water management works are either exempt or have been issued Z-- general permits. The rules of NWFWMD have been the least complex and most limited of all the water management districts within the State. The Department of Environmental Regulation (DER) regulates stormwater runoff and its impact on receiving waters through Chapter 17-25 F.A.C. The DER requires as a minimum that the discharges of new stormwater sources design discharges to attain certain treatment levels and notify the Department 30 days prior to construction activities. There are exemptions from this rule which involve small residential projects and agricultural and silvicultural activities. The Florida Department of Transportation (FDOT) has recently promulgated a comprehensive drainage criteria manual pursuant to Chapter 14-86 F.A.C. which must be adhered to for new development or redevelopments that discharge into or through State road rights-of-way. The FDOT manual outlines policies, facilities design criteria and procedures and hydraulic theory which is to be used for the regulation or analysis and design. The United States Environmental Protection Agency (EPA) has general regulatory purview for water quality in streams, lakes and estuaries throughout the State. EPA has developed the National Pollutant Discharge Elimination System (NPOES) for regulating point source discharges through monitoring and tm: SANTA ROSA: 9 2-2 permitting. In the last few years EPA has been bringing the NPDES permitting process to bear on stormwater discharges and, in the future, this program may well dictate the extent of attenuation and treatment required from stormwater discharges in the County. Santa Rosa County does have a Flood Plain Management Ordinance (75-04) which regulates development of low-lying flood hazard areas as its primary objective. This ordinance, however, is construction specific and does not deal with attenuation of new stormwater flow which can produce increased flooding levels. This is an area of concern that currently lacks regulation. Part of the intent of this study is to develop quantities for a more comprehensive stormwater management ordinance. 2.3 DRAINAGE FACILITY INVENTORY A Drainage Facility Inventory was conducted to help assess drainage problems within the county. Location, condition and capacities of the over .430 stormwater structures were documented. This inventory concentrated on major conduits due to the limited funds available for field work. Major structures were defined as conduits of 30" diameter (or equivalent) in size or larger. J/C/F, through published mapping, identified conduit locations and then field verified each structure and determined its size. If a pipe met the size criterion it was recorded and assigned a structure number. All field verified structures were located on a general highway map which comprises the base sheets of the stormwater atlas. tm: SANTA ROSA: 9 2-3 2.4 STORMWATER ATLAS The County was divided into ten basins and 67 subbasins using USGS 7.5' quadrangle maps to determine drainage basins and subbasins. Each basin was given a name based on its proximity to a major waterbody or conveyance and each subbasin was likewise named for its major watercourse. In some instances two or more subbasins are identified by the same name but have different numbers assigned. The next step was to convert each field assigned structure number into a discrete nomenclature so its loction could be readily identified. A seven digit number was assigned'to each structure in the following style: Structure Number AABB-CDD AA - Denotes Basin BB - Denotes Subbasin; C - is a qualifier where 0-8 denotes the structure is on a major watercourse and 9 denotes a structure on a non-defined watercourse; and DD - Denotes the structure number, usually by increments of five. Using this numbering system, the drainage atlas was completed which divided the County into six map sheets disregarding the drainage divides. Superimposed on these map sheets were the drainage divides with structure locations identified. Appendix "A" contains a copy of the drainage atlas. tm:SANTA ROSA: 9 2-4 2.5 HYDROLOGIC DATA Three primary sources were drawn upon for hydrologic data collection. They are the USDA Soil Conservation Service (SCS), the U.S. Geological Survey and (USGS), the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA). The SCS published a comprehensive document entitled Soil Survey, Santa Rosa County, Florida (1980) which identifies, by aerial interpretation and field investigation, the types of soils present within the County and presents their engineering properties. This documents presents valuable data with rega -rd to runoff and ground water recharge. The USGS, in addition to publishing one inch = 2000 feet scale quadrangle maps with five foot interval contours, collects and publishes water resource data for Santa Rosa County. Volume four, the Northwest Florida Edition of the Water Resources Data, Florida, Water Year 1985, has recorded information on seven wells and two stream gaging stations (Escambia River and Big Cold Water Creek). No lake gaging stations are presently monitored by the USGS in Santa Rosa County. Lastly, NOAA is responsible for monitoring and documenting climatological data with published data for stations located in Pensacola and Milton. Information includes temperature and precipitation presented by normals, means and extremes. tm: SANTA ROSA: 9 2-5 2.6 HYDRAULIC DATA The primary source of hydraulic data is the Federal Emergency Management Agency's Flood Insurance Study for Santa Rosa County. The study, published in 1985, addresses flood problems in the County's extensive riverine and coastal areas. Flood profiles were determined for the Escambia, Yellow, Blackwater and East Bay Rivers. This study was incorporated into the Flood Plain Management Ordinance. 2.7 HISTORICAL FLOODING Santa Rosa County does not have a formal flood complaint tracking system. Major flood events, particularly hurricanes, have been generally documented. As for more frequent flooding, the County Road Department has identified areas which are particularly susceptible to flooding. These areas are attributed to alteration of drainage patterns and inadequate treatment of runoff due to development. tm:SANTA ROSA:9 2-6 0 .L@ SECTION THREE ("'OSEC - 0 I Section 3 GOALS, OBJECTIVES AND POLICIES 3.1 GENERAL - GOALS PHILOSOPHY Santa Rosa County's population is average in number when compared with other counties. in Florida and is one of the larger in physical size although it ranks fifteenth statewide. A significant portion of the County will remain undeveloped due to the controlled public ownership associated with the Backwater River State Forest and the numerous military bases. Population growth in the County is predicted to continue at the average state growth rate. This would indicate that tax base cannot be expected to provide significant additional funding in the future without a significant millage rate increasd and would therefore impact goal development and attainment. The County will have to develop methods to control and direct growth with a minimum of expenditure of funds. The goals formulated in this Section take that into consideration along with the fact that even though state-of-the-art methods can be implemented in Santa Rosa County in the same fashion that they are used in metropolitan population centers with vastly greater funding sources, the County cannot expect to replicate their stormwater management programs with their current revenue base. tm: SANTA ROSA: 11 3-1 The stormwater needs for Santa Rosa County can be broken into three components stemming from the protection of the health, safety and welfare of the public. The three areas are flooding, pollution and funding to prevent or mitigate the first two. Pollution is addressed in this report from the perspective of stormwater runoff only. Two other water pollution sources that must be addressed by the County and State are wastewater and industrial/commercial. 3.2 SPECIFIC SUPPORTING GOALS Goal I: Protect people and property from the hazards of flooding. Objective I-A: Assure the health, safety and welfare of the public from both direct and indirect effects of uncontrolled flooding. Policies: 0 Prohibit any development activity that would potentially endanger lives and/or have an adverse effect on property, water discharge quality or quantity, or valued environmental systems as a result of alteration of existing structures and natural drainage systems. tm: SANTA ROSA: 11 3-2 0 Assure that designated natural drainage corridors are maintained in an open and unobstructed conditioti in order to conserve their function and prevent flooding. 0 Require developers of industrial sites, subdivisions and PUD's to provide stormwater retention systems to minimize flooding (and non-point source pollution). 0 Assure that flood plain uses are consistent with approved land use plans for the flood plain areas and are coordinated with plans for the total community. 0 Regulate use of flood plains for development, fill, dumping, storage of materials, structures, buildings, utilities, or any other work which acting alone or in combination with other existing or future uses will increase flood heights and velocities, upstream or downstream from proposed use, by obstructing flows and reducing storage. Discourage development in areas subject to flooding problems. 0 Regulate development which may, when acting alone or in combination with other developments, create a demand for public investment in flood- control works by requiring protection against flood damage at the time of initial construction and afterwards. tm: SANTA ROSA: 11 3-3 0 Ensure that the design of the drainage system will be consistent with good engineering practice and design through the adoption and periodic updating of a comprehensive,drainage criteria and procedures manual. 0 Utilize existing channel capacity for routing flood flows before@`using on-site storage or other structural measures to provide treatment and flow attenuation. 0 Provide for public education of the causes and potential for flooding. 0 Provide a means of placing potential owners, builders, developers--, and the general public on notice of existing and potential flood hazards. 0 Administer the FEMA regulatory program requirements of local communities and adopt the FIRM flood plain and floodway delineation mapping in the absence of site specific study mapping. Goal II: Minimize the adverse impacts of stormwater runoff on the surface and groundwater resources of Santa Rosa County. Objective IIA: Take all necessary action to protect all waters and specially designated waters. As Santa Rosa County has been afforded special water quality protection by virtue of Outstanding Florida Waters (O.F.W.) designations to the Blackwater River and the Gulf Islands National Seashore and Aquatic Preserve (A.P.) status to Yellow River Marsh and Fort Pickens State A.P., all reasonable efforts should be made tm: SANTA ROSA: 11 3-4 to continue cooperation toward, and enforcement of, the intent of these designations. Pol icies: 0 Prevent stormwater runoff from degrading water quality below those levels prescribed by statute, rule and regulation. 0 Prevent sewage or industrial effluent from degrading water quality as above. Objective II-B: P@otect the fish and shellfish environments of the sound, bays, estuaries, and waterways of the County, and as far as practicable, adjoining counties. Policies: 0 Create through ordinance proscriptive laws to regulate water degradation. 0 Implement enforcement program. 0 Cooperate with Escambia and Okaloosa Counties to assure area-wide compliance. 0 Require that stormwater runoff be treated to reduce the load of pollutants carried into receiving waters. tm: SANTA ROSA: 11 3-5 0 Protect and maintain natural salinity level in estuarine areas. Objective II-C: Protect the functions of natural groundwater quality and recharge. Lal_ Policies: 0 Discourage development practices which create over-drainage of land and soil. 0 Encourage on-site detention and/or retention facilities in upland areas. Objective II-D: Protect the functions of natural drainage systems. Policies: 0 Regulate land use and development to protect natural drainage systems. 0 Protect natural resource systems which attenuate runoff quantity and/or quality. 0 Mandate that all new development or redevelopment not adversely impact water quality. 0 Encourage development which beneficially impacts natural features and resources including preservation of storage capacities. tm: SANTA ROSA: 11 3-6 0 Maintain all natural drainage systems in as natural a condition as possible. 0 Provide for development of areas with minimum adverse effects to the natural environment. Goal III: Develop the full potential of the existing stormwater system and system financing methods and explore new financing avenues. Objective III-A: Remedy existing facility deficiencies. Policies: 0 Define suitable levels of service criteria. 0 Identify existing problems. 0 Prioritize identified problems. 0 Implement C.I.P. program with funding. 0 Ensure, as far as possible, an efficient drainage system that will not result in excessive public or private moneys being used for maintenance and replacement of portions of the system. tm: SANTA ROSA: 11 3-7 0 Minimize public and private property damage resulting from erosion, sedimentation, flooding and excessive maintenance requirements. 0 Require temporary and permanent erosion and sediment control measures to protect individuals occupying land adjacent to and downstream from proposed developments from being damaged by sediment originating from within or because of proposed development. Objective III-B: Mai.ntain existing facility capacities. Policies: 0 Determine existing capacities of all major conveyance systems. 0 Devise, develop and revise, as necessary, a suitable O&M criteria and work program to maintain the existing facilities in optimum conditions. 0 Implement program. Objective IiI-C: Coordinate up-grading and expansion of major facilities to meet the adopted level of service standards and to provide for future needs. tm: SANTA ROSA: 11 3-8 Pol icies 0 Identify current facility needs to meet the adopted level of service standard. 0 Identify future facility needs. 0 Prioritize identified facility needs. 0 Implement C.I.P. program with funding. 0 Reduce capital expenditures for flood proofing and storm drainage systems where feasible by routing runoff through swales or other natural retention/detention systems to increase stormwater infiltration, settle suspended solids and remove pollutants. Objective III-D: Encourage developer participation in upgrading deficient drainage systems as impacted by their projects. Policies: 0 Publish an assessment of problem areas within the County. 0 Set standards for participation in joint developer/County projects to provide suitable outfalls for new development and maintenance of suitable conveyance in existing facilities. tm: SANTA ROSA: 11 3-9 Objective III-E: Coordinate stormwater management programs with other public works projects to derive the maximum use from budget dollars. Policies: 0 New road projects should incorporate suitably detailed drainage studies using appropriate evaluation methods to ensure the proper sizing of new and replacement structures, demonstration of both upstream and downstream impacts, and site specific delineation of flood plain boundaries. 0 The Planning Department should work with public works in zoning and land use matters to det@rmine whether certain areas have adequate drainage facilities or are part of or need to be part of future drainage projects. tm:SANTA ROSA:11 3-10 0 f @ I SECTION FOUR - 4@ I Section 4 BASIN CHARACTERIZATION 4.1 BASIN DELINEATION One of the initial steps in reviewing and establishing the physical setting for all basins involves the careful evaluation and interpretation of the topographic features of each basin. The topography of the basins in Santa Rosa County is such that'smaller, well defined subbasins can be identified. These subbasins are formed by a combination of natural and man-made features which include ridges, depressions and highways. The procedure generally used for the delineation of watersheds involved successive stages of basin identification and refinement. It is a procedure best begun on a large scale where major basin divides are identified by the reach of the tributary water courses. Once the major basin divides are determined, the process of identifying and delineating the smaller tributary basins, which further subdivide the major basins, requires assessment of natural topographic features and manmade improvements. The discretization of individual major and minor subbasins requires detailed examination may also require field investigations in the study area. The nature and physical characteristics of the watersheds within the County have been altered during the last century through man's attempt to utilize and control available water resources. Benefits of these works are improved tm:SANTA ROSA-2:AA 4-1 public health and safety and the avail a bil ity of water related 1 ivel i hoods for the citizens for Santa Rosa County. 4.2 BASIN ASSESSMENT The basin planning assessment is intended to provide a comprehensive overview of the ten basins in Santa Rosa County. The evaluation covers such topics as physical setting, basin and subbasin delineations and drainage complaints. The discussions of physical setting provides an overview of he general patterns and direction of drainage in the subbasins and basins. Review of drainage complaints discussed with County staff and investigated in the field is addressed and recurring chronic problems are reviewed and categorized. J/C/F made an assessment of problem areas, within the urban areas, which resulted in the identification of 47 different problem areas. The probl ems ranged from lack of adequate drainage systems to erosion. In some cases the problems involve structure flooding. Of the 47 identified areas, twelve are clustered on the west end of the peninsula near Gulf Breeze. Other locations with general problems are the Floridatown and Dickerson City areas. The majority of the problems exist in the southern portion of the County where land development activities have been historically focused. The remaining problem areas are scattered throughout the County and range from coastal to inland water course flooding, again mostly caused by inadequate systems. Other problems may exist throughout the County but have not been tm:SANTA ROSA-2:AA 4-2 recorded by County staff. This observation is particularly valid in the State forest and other military bases. Sections 4.2.1 through 4.2.10 provides an overview through a basin by basin discussion. 4.2.1 Escambia River Basin The Escambia River Basin is located in the western portion of Santa Rosa County and the river forms the county line between Santa Rosa and Escambia Counties. The river originates in Alabama and approximately one-mile south of Florida-Alabama state line. The Conecuh River and Escambia Creek join to form the Escambia River. The river flows south and enters the Gulf of Mexico through Escambia and Pensacola Bays. The river flows approximately 57 miles through Santa Rosa County and the basin covers approximately 4,200 square miles of which only 10% is located in Florida. Of the some 420 square miles located in Florida only 38% or approximately 160 square miles are in Santa Rosa County. The average flow of the river is 6,500 cfs; however, the flow rate is highly variable. During periods of low flow, a saltwater wedge penetrates as much as 8 miles upstream. The basin is divided into six (6) subbasins which have the following characteristics: tm:SANTA ROSA-2.AA 4-3 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) MI) WIDTH STRUCTURES ESCAMBIA RIVER BASIN** 01-01 25.27 25.27 8.0** 3.2 17 01-02 20.34 20.34 4.0** 5.1 11 01-03 33.52 33.52 7.0** 4.8 4 01-04 25.92 25.92 10.0** 2.6 10 01-05 29.77 29.72 4.0** 7.4 -0- 01-06 25.23 25.23 3.0** 12 SUBTOTAL 160.1 *Average width of channel bottom. **Cumulative upstream area and basin extends beyond Santa Rosa County. The Escambia River Basin is very rural in nature with very low intensity land use, which is primarily forest and agriculture. Portions of the towns of Jay and Pace are located within this basin. 4.2.2 Escambia Bay Coastal Basin The Escambia Bay Coastal Basin is located in the southwestern portion of Santa Rosa County and is the point of inflow for the Escambia River into Escambia Bay. This coastal basin is 40.5 square miles in size and is divided into two (2) subbasins of 18.28 and 22.23 square miles. The basin is divided into two (2) subbasins which have the following -characteristics: tm:SANTA ROSA-2:AA 4-4 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) MI) WIDTH STRUCTURES ESCAMBIA BAY COASTAL BASIN 02-01 18.28 18.28 4.0 4.6 ,;,-24 02-02 22.23 22.23 3.5 6.4 32 SUBTOTAL 40.5 *Average width of channel bottom. The Escambia Bay Coastal Basin is the most urban in nature with single family residential being the predominate land use. Additionally there are areas of medium and medium-high density residential, planned business, a small area of federal and some agricultural lands. The town of Pace is the primary population center in this basin. 4.2.3 Pond Creek Basin The Pond Creek Basin is located in the west-central part of Santa Rosa County and is 99.6 square miles in size. The basin is completely contained in Santa Rosa County and flows south for approximately 20 miles before entering Blackwater Bay just below the town of Milton. The average flow in Pond Creek, at a point approximately 10 miles upstream from its mouth, is 79.6 cfs. The basin is divided into five (5) subbasins which have the following characteristics: tm:SANTA ROSA-2:AA 4-5 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) (MI) WIDTH STRUCTURES POND CREEK BASIN 03-01 13.35 99.58 5.0 2.7 14 03-02 15.00 86.23 3.5 4.3 9 03-03 33.19 71.23 6.0 5.5 ---21 03-04 20.25 38.04 3.0 6.8 4 03-05 17.79 17.79 2.0 8.9 6 SUBTOTAL 99.6 *Average width of channel bottom. Land use in the Pond Creek Basin is fairly evenly divided between agriculture and single family residential uses with some small areas of medium density residential and commercial . 1,2,1 last lay Coastal Basin The East Bay Coastal Basin is located in the south central and southeastern part of Santa Rosa County. The basin fronts on Blackway Bay, East Bay and a small subbasin which is in the extreme southwest fronts on Pensacola Bay. This coastal basin is 90.1 square miles in size and is divided into eleven (11) subbasins which range in size from 2.64 square miles up to 21.76 square miles. The following table lists the basins and subbasin characteristics: tm:SANTA ROSA-2:AA 4-6 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED (SQ MI) AREA (SQ MI) (MI) WIDTH STRUCTURES SUBBASIN EAST BAY COASTAL BASIN 04-01 16.31 16.31 3.0 5.4 .-14 04-02 2.64 2.64 1.0 2.6 5 04-03 7.62 7.62 1.0 7.6 3 04-04 3.35 3.35 1.5 2.2 9 04-05 4.07 4.07 1.3 3.1 -0- 04-06 5.99 5.99 2.0 3.0 -0- 04-07 7.46 7.46 4.0 1.9 -0- 04-08 21.76 21.76 4.0 5.4 6 04-09 12.57 12.57 2.2 5.7 17 04-10 4.59 4.59 0.4 11.5 3 04-11 3.69 3.69 NA NA -0- SUBTOTAL 90.1 *Average width of channel bottom. The East Bay Coastal Basin is heavily urbanized with single family and medium density residential being the primary land uses. In the southeastern portion of the basin, four subbasins include large sections of the Eglin Wildlife Management Area in their land uses. 4.2.5 Blackwater River Basin The Blackwater River Basin originate north of Bradley, Alabama and the Blackwater River flows south approximately 58 miles before entering Blackwater Bay in Santa Rosa County. The river flows through portions of Santa Rosa and Okaloosa Counties draining about 860 square miles of which 109.2 square miles are in Santa Rosa County. The average discharge of the Blackwater River is approximately 400 cfs, at a location some 35 miles upstream of the mouth. Groundwater provides the principle source of water in this system. Salt water encroachment has been reported six tm-SANT'A ROSA-2:AA 4-7 miles upstream from the mouth of the river. Major tributaries of the Blackwater River include Big Juniper Creek, Coldwater Creek and Pond Creek. The basin is divided into seven (7) subbasins which have the following characteristics: CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ-MI) (MI) WIDTH STRUCTURES BLACKWATER RIVER BASIN** 05-01 19.66 109.17 4.0 4.9 13 05-02 21.97 21.97 7.5 2.9 16 05-03 8.09 89.51 3.5 2.3 2 05-04 13.42 59.45 3.5 3.8 3 05-05 23.56 46.03 7.0** 3.4 6 05-06 9.60 22.47 3.0** 3.2 -0- 05-07 12.87 12.87 8.0** 1.6 2 SUBTOTAL 109.2 *Average width of channel bottom. **Cumulative upstream area and basin extends beyond Santa Rosa County. Land use in the Blackwater River Basin is divided between state lands, agriculture and single family residential. The lower end of the basin contains medium density residential, some planned business and industrial areas and the City of Milton. 4.2.6 Coldwater Creek Basin The Coldwater Creek Basin is located in central and north-central Santa Rosa County and is the largest basin with 232.3 square miles. Coldwater Creek is tributary to the Blackwater River and has an average flow of 533 cfs as recorded 3 miles upstream from its junction with the Blackwater River. The basin is divided into twelve (12) subbasins which range in size from 5.42 square miles to 32.31 square miles in size. The twelve subbasins have the following characteristics: tm:SANTA ROSA-2:AA 4-8 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) (MI) WIDTH STRUCTURES COLDWATER CREEK BASIN** 06-01 9.70 232.27 3.0 3.2 9 06-02 5.42 222.57 2.0 2.7 -0- 06-03 6.55 6.55 2.5 2.6 1 06-04 18.87 210.68 3.5 5.4 2 06-05 32.31 80.12 10.0 3.2 7 06-06 20.33 20.33 7.0** 2.9 -0- 06-07 27.48 27.48 7.0** 3.9 1 06-08 28.84 111.61 6.0 4.8 18 06-09 18.12 18.12 7.5 2.4 7 06-10 25.17 64.65 5.0 5.0 17 06-11 16.69, 38.48 1.0 16.7 3 06-12 22.79 22.79 8.0** 2.8 10 SUBTOTAL 232.3 *Average width of channel bottom. "Cumulative upstream area and basin extends beyond Santa Rosa County. Land use in the Coldwater Creek Basin is primarily agriculture and state lands (Blackwater River State Forest) with some single family residential in the south end of the basin and in the north around the town of Jay. In the north end of the basin there are three (3) small areas designated as commercial land use. 4.2.7 Big Juniper Creek Basin The Big Juniper Creek Basin is located in north east Santa Rosa County and is 131.9 square miles in size. Big Juniper Creek is tributary to the Blackwater River and has an average flow of 220 cfs at a point 8.3 miles upstream from its junction with the Blackwater River. The basin is divided into eleven (11) subbasins which range in size from 4.81 square miles to 19.62 square miles in size. The eleven (11) subbasins have the following characteristics: tm:SANTA ROSA-2:AA 4-9 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) (MI) WIDTH STRUCTURES BIG JUNIPER CREEK BASIN** 07-01 4.81 131.87 3.0 1.6 4 07-02 10.85 10.85 6.0 1.8 -0- 07-03 10.74 116.21 3.0 3.6 1 07-04 17.33 105.47 3.5 5.0 5 07-05 6.77 37.98 1.5 4.5 3 07-06 11.59 31.21 2.0 5.8 9 07-07 19.62 19.62 8.0** 2.5 10 07-08 12.83 50.16 2.5 5.1 5 07-09 11.37 37.33 2.2 5.2 1 07-10 11.25 25.96 3.0 3.8 -0- 07-11 14.71 14.71 6.0** 2.5 -0- SUBTOTAL 131.9 *Average width of channel bottom. **Cumulative upstream area.and basin extends beyond Santa Rosa County. Land use in this basin is agriculture and state lands (Blackwater River State Forest) and would not be expected to change anytime in the near future. 4.2:8 Yellow River Basin The Yellow River Basin originates in Covington County, Alabama and flows southward for approximately 92 miles emptying into Blackwater Bay in south-central Santa Rosa County. The Yellow River Basin drains roughly 860 square miles located in Santa Rosa County. The rate of flow for the Yellow River (40 miles above the mouth) averages 1,500 cfs. The basin is divided into five (5) subbasins which have the following characteristics: tm:SANTA ROSA-2:AA 4-10 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ MI) AREA (SQ MI) (MI) WIDTH STRUCTURES YELLOW RIVER BASIN" 08-01 25.84 118.64 7.0 3.6 4 08-02 16.67 93.60 2.0 8.3 7 08-03 28.55 28.55 8.0** 3.6 -0- 08-04 25.61 48.38 4.0 6.4 3 08-05 22.77 22.77 5.0** 4.6 4 SUBTOTAL 118.6 *Average width of channel bottom. "Cumulative upstream area and basin extends beyond Santa Rosa County. Land use in the Yellow River Basin is primarily forest, federal lands, agriculture and preservation lands and in the lower end of the basin, some areas-of single family residential use. 4.2.9 East Bay River Basin The East Bay River Basin is located in the southeastern corner of Santa Rosa County and is 19.4 square miles in size making it the smallest basin in the County. The East Bay River flows west from the Okaloosa County line approximately 4.5 miles before emptying into the east bay. The basin is divided into two (2) subbasins which have the following characteristics: tm:SANTA ROSA-2:AA 4-11 CHANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SQ-MI) AREA (SQ MI) NO WIDTH STRUCTURES_ EAST BAY RIVER BASIN** 09-01 7.22 19.42 2.5 2.9 09-02 12.20 12.20 2.0** 6.1 -0- SUBTOTAL 19.4 *Average width of channel bottom. **Cumulative upstream area and basin extends beyond Santa Rosa County. The primary land use in this basin is federal lands (Eglin Wildlife Management Area) and some large are'a's of single family residential and some small areas of medium density residential, commercial and industrial. 4.2.10 Santa Rosa Sound Coastal Basin The Santa Rosa Sound Coastal Basin is the southern most basin in Santa Rosa County. The basin fronts on Santa Rosa Sound and includes a small portion of the City of Gul f Breeze whi ch i s 1 ocated on the west end of the bas i n. The basin is 22.5 square miles in size making it one of the smallest in the County. The basin is divided into four (4) subbasins which have the following characteristics: tm:SANTA ROSA-2:AA 4-12 HANNEL NUMBER OF BASIN/ AREA UPSTREAM LENGTH AVERAGE* INVENTORIED SUBBASIN (SO MI)_ AREA (SQ MI) (MI) WIDTH STRUCTURES SANTA ROSA SOUND COASTAL BASIN 10-01 1.68 1.68 NA NA _O_ 10-02 8.72 8.72 0.5 17.4 11 10-03 8.90 8.90 2.0 4.5 15 10-04 3.19 3.19 1.0** 3.2 12 SUBTOTAL 22.5 *Average width of channel bottom. **Cumulative upstream area and basin extends beyond Santa Rosa County. The Santa Rosa Sound Coastal Basin is very urban in nature with single family residential being the single largest land use. There is also medium density and medium-high density residential as well as strip commercial. 4.3 DRAINAGE PROBLEM OVERVIEW As with most counties, Santa Rosa has specific drainage problems that have been created by any of a number or combination of reasons. Overdevelopment, urbanization without adequate drainage system upgrading, undersized systems, tidal surges, poorly maintained systems and inappropriate construction in flood plain and flood prone areas are problem sources. Flooding needs to be characterized by severity level and frequency where adequate records are available. It is both impractical and exorbitantly expensive to design drainage systems to eliminate or prevent all flooding so it becomes necessary for the government to develop public policy of establishing a standard which describes how much flooding is acceptable. This can be done through defining levels of service. Levels of stormwater service are determined using four basic criteria tm:SANTA ROSA-2:AA 4-13 which are hazard to human life, structure flooding/damage, roadway flooding and yard flooding. Typically, loss of life is associated with severe storm events and js usually related to hurricanes. With the advanced warning systems and evacuation administered through the National Weather Service and the Federal Emergency Management Agency, this high cost can be significantly reduced through use of preventative measures. Temporary evacuation is the best means of dealing with severe coastal flooding. , This is not to say, of course, that sudden and severe freak events (no name storms) will not occur without warning, but prudent construction such as minimum elevations, anchoring and flood proofing will mitigate such damage. For more common storm events, urban flooding may be divided into severity levels: Water contained within gutters or swales, water flooding right of way inhibiting or prohibiting transportation, water flooding yards and lastly water within buildings (structure flooding). Loss of life is always used as a criteria since i-t is not acceptable, nor are hazards such as potable water sources being contaminated from stormwater flooding. Rural flooding is usually viewed differently than urban flooding because the value of rural property and structures is not as great and the consequences are usually .not as intolerable. Rural citizens tend to take a more philosophical viewpoint and see flooding as a perennial occurrence. ANO tm:SANTA ROSA-2:AA 4-14 4.4 RANKING METHODOLOGY On a whole, the drainage problems in the County are not particularly severe, extensive in areal extent or large in magnitude. Only four areas have reported structure flooding. Individual flooding problems are summarized in Table 4-1. Flooding problems were broken down into seven categories which helped determine the ranking system as follows: Nature of Problem Number of problems Erosion 5 Inadequate*(undersized) System 8 No Outfall 19 No Drainage Systems 11 Tidal Flooding 3 Sediment Build-Up 1 The level of severity of a flooding problem must be considered when developing a ranking system. Structure flooding generally receives the highest severity level with minor erosion representing the least severe problem. Table 4-2 ranks the relative severity level of nine different categories of problems. The ranking system rationale is based on a combination of cost and ease of correction. After that, each rank can be further prioritized based upon such variables as passibility of roadways (by road classification) and value of properties protected. tm:SANTA ROSA-2:AA 4-15 TABLE 4-1 SUMMARY OF IDENTIFIED FLOODING PROBLEMS ------------------------------------------------------------------------------------------------------------------------------------ PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUSBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------- Escambia River Basir, -------------------- 1 01-05 1.5 miles west of S-164 and Structure Flooding 4 $30,000 S-197 intersection 2 01-05 1.3 mil&% west of S-164 and Ditch Erosion 45 $3,400 S-197 intersection 3 01-05 Sandy Hollow, 0.6 miles west Ditch Erosion 46 $11,700 of S-197 4 01-06 Camors Road @ end of Erosion 4 21 $81,500 existing pavement 5 01-or. 2 miles west of High School No Drainage Outlet 2 43 $5,400 ----------- BASIN SUBTOTAL $132,000 Escambia River Coastal Basin ---------------------------- 6 02-01 Charles Street. 0.5 miles Low Area - Periodic Flooding 3 33 $30,600 east of S-197 7 02-01 Hamilton Lane Yard/Street Flooding 6 a $6, 700 02-01 Floridatowre Area Yard/Street Flooding 7 7 $ 1, 800, 000 02-01 Todd Estates Road Flooding 3 30 $25,000 10 02-02 Trout Bayou -Howard Circle Yard/Street Flooding 6 9 $7,700 11 02-02 Angia Drive Yard/Street Flooding 6 10 $10,300 - No Side Ditches 12 02-02 Dolphin Road @ Raughtor, Road Side Ditches Flood 3 24, $18,750 13 02-02 Pearson Road Side Ditches Flood and 3 36 $37,500 do riot Drain 14 02-OL- Holiday Lane arid Raughtor, Road Inter5ection Floods 5 14 $4,475 BASIN SUBTOTAL $1,941,025 ------------------------------------------------------------------------------------------------------------------------------------ PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ Pond Creek Basir, ---------------- 15 03-01 Santa Villa Area Yard/Street Flooding 7 6 $437,500 16 03-02 Luther Fowler Road Road Flooding 5 le $40, 700 (Orifith to Evwrgrwer,) 17 03-05 Church ors 5-164 Church and Cemetery Flooding 9 1 $4,200 ----------- BASIN SUBTOTAL $48-2,400 ------------ a ---------------------- ----------------- ----------------------------------------- 0 --- PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCA7 I ON DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ East Day Coastal Basin ---------------------- 18 04-01 Highland Wood S/D Street Flooding 3 25 $10,750 19 04-01 Hungaria Estates Street Flooding 3 29 $24,500 20 04-01 S-191, 2 Failes south Road S-191 Floods 5 15 $a,-375 of Whitaker Bayou 21 04-01 S-191, 3 tailes south Road 5-191 Floods 5 17 $23, 400 of Whitaker Bayou 22 04-01 Dickerson City Inadequate Ditches and 3 35 $34,975 Culverts 23 04-01 Hwy. 191 -C Water Standing in Ditches and 3 24 $7, 800 Discharge affected by Tidal Fluc. '@4 04-02 Lavon Street Flooding - Ditches do not 3 37 $38, 6 lei Dra i n 25 04-03 Ward Basin Road Sediment Build up ort 5 16 $18,750 US-87 frorn Adjoining Clay Road 26 04-08 Holley Pit Road Clay Road Flooding 3 34 $33,000 27 04-09 Clay Circle Flooding 3 26 $13, SOO 28 04-09 East Bay Heights S/D Road and Yard Flooding 3 31 025,875 29 04-10 Coral Strip Parkway Pond and Road Flooding 3 39 $50,000 30 04-10 Whimper Day Blvd. r I ood i ng 3 38 $4(A, 0OC4 31 04-10 Rosa Del Villa No Drainage System 2 44 $21,500 32 dge Estates St ruc t ure/ Yard Flooding 5 $32,500 04 - IQ' Bay Ri 33 04-10 Bal Alex Estates Stt-ucture/Road/Property 3 $20, 25UA BASIN SUBTOTAL $404,685 ----------------------------------------------------------------------------------------------------------------------------- ------ PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUBBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ Blackwater River Basin ---------------------- 34 05-01 hast Milton in existing S/D Street Flooding 5 19 $59,000 35 05-03 East of Hwy. 67 and Hwy. 90 Road Flooding 5 20 $59, 625 Intersection ----------- BASIN SUBTOTAL $118,625 Coldwater Crook Basin --------------------- 36 06-09 Hall Rood, east of Hwy. 164 Erosion around Drainage Pipe 1 47 $12,000 Could Undermine Highway 37 06-09 Hwy. 4 0 Jordan Road Structure Flooding 8 2 $6,325 ----------- BASIN SUBTOTAL $18,325 Yellow River Basin ------------------ 38 08-04 Shangrals S/D Erosion in Drainage Ditch 3 40 $55,500 ----------- BASIN SUBTOTAL $55,500 East Day River Basin -------------------- 39 Navarre East S/D Roadway Intersection Floods 3 22 $5,500 BASIN SUBTOTAL $5,500 ----------- a --------------- --------------------------------------------------------------------------------------------- PROBLEM BASIN/ PROBLEM PRELIMINARY ESTIMATED NUMBER SUSBASIN LOCATION DESCRIPTION SEVERITY PRIORITY COST ------------------------------------------------------------------------------------------------------------------------------------ Santa Rosa Sound Basin ---------------------- 4e( 10-02 Villa East S/D Street/Lot Flooding 6 12 044,000 41 10-02 Woodlore S/D Street/Lot Flooding 6 it $30,000 42 10-02 Savannah Estates Street/Lot Flooding 6 13 $111,000 43 10-02 Villa Venyae Road Flooding 31 42 094,000 44 10-", Blue Herron Cove Road Flooding 3 41 $64,500 45 10-02 Laurel Drive Street and Pond Flooding 3 32 030,500 46 10-04 Janet Street and Nina Street Flooding 3 27 $16,750 47 10-04 Bandero S/D Road Flooding 3 23 *6,875 ----------- BASIN SUBTOTAL 10397,625 GRAND TOTAL COST $3,555,665 TABLE 4-2 SEVERITY LEVEL SUMMARY Severity Number of Level Description of Problem Problems 9 Public Institution Structural Flooding 1 8 Privately Owned Structural Flooding 4 7 Neighborhood Non-Structural Flooding 2 6 Street and Yard Flooding 6 5 Major Street and Intersection Flooding 7 4 Major Erosion/Sedimentation 1 3 Minor Street Flooding 21 2. Closed Basin Flooding or Nuisance Tidal Flooding 2 1 Minor Erosion/Sedimentation 3 tm:SANTA ROSA-2:AA 4-17 Erosion is critical because of the potential loss of property and improvements inherent to it. Inadequate or undersized systems presume adequate right-of- way which otherwise would take money and time to acquire and therefore can be less expensive and more quickly remedied than the situations of either no outfall or drainage system which presumes right-of-way easement acquisition. Tidal problems are typically most difficult to correct because they involve low-lying land. In some instances, (one-way) flap gates can be installed but these types of solutions.,are subject to expensive maintenance problems and tampering by property owners. 4.5 PRIORITIZATION The County's main drainage problems have been identified, characterized and must be prioritized. The County should review the problems in aggregate and decide to what extent they wish to act to remedy them over a finite time period. tm:SANTA ROSA-2:AA 4-18 0 1@- I%- SECTION FIVE . 0 I Section 5 DEVELOPMENT OF DESIGN STORM 5.1 GENERAL The usual analytical methodology adopted for the design of stormwater management facilities is to evaluate the flooding conditions that would be caused by selected critical rainstorms. The same critical rainstorms are used to evaluate land use changes due to development within a basin. Because it serves as one of the major yardsticks for quantifying runoff rates and volumes, the rainstorm database is one of the most important factors- in a stormwater master planning program. Consequently, selection of the critical design storm(s) requires careful evaluation. 5.2 DESIGN STORM CONCEPT A synthetic design storm consists of a rainfall hyetograph (plot of rainfall intensity vs. time) which is based upon the characteristics of a number of historical rainstorms. The key assumption of the design storm approach is that the frequency of occurrence of the design storm and the calculated runoff peak are identical. For example, it is assumed that a 25-year design storm will produce a 25-year peak runoff event. This assumption is critical because of the difficulty in ascribing a frequency of occurrence to a rainstorm synthesized from portions of several historical storms, the importance of antecedent soil moisture conditions and initial lake levels in determining watershed response to a given rainfall event, and the statistical non- tm: SANTA ROSA: Y 5-1 homogeneity of rainfall and runoff data. However, the synthetic design storm concept is a theoretical method that continues to be the most widely used approach to stormwater management planning and drainage facility design. 5.3 DESIGN STORM COMPONENTS The four facets which define a particular design storm are (1) the frequency of occurrence, (2) the storm duration, (3) the total volume of rainfall for the particular frequency and duration; and (4) the temporal distribution of that amount over the storm duration. 5.3.1 Rainfall Frequency Stormwater planning studies have relied upon a range of design storm return periods (recurrence intervals), depending upon the area and the nature of the stormwater problem. For example, alternatives used within this region include design storms with 2-year, 5-year, 10-year, 25-year, 50-year, and 100-.year return periods. The 100-year flood event, which is the standard for FEMA's Federal Flood Insurance Program, is normally too stringent for a stormwater management master plan. Because it is such an infrequent and extreme event, the 100-year flood usually cannot be managed with traditional urban runoff controls. In the Santa Rosa County, it is likely that the majority of the streamflow peak and streamflow volume during the 100-year flood event are contributed by both urban and non-urban land uses during the frontal-type storms (i.e., long tm: SANTA ROSA: Y 5-2 duration and moderate rainfall intensity) which produce most 100-year events. Consequently, it is recommended that the stormwater master planning study should not rely upon a 100-year design storm as a performance standard for structural stormwater management facilities. Nonstructural stormwater management alternatives such as floodplain management and regulatory policies should be evaluated on the basis of 100-year flood flows and it is recommended that the runoff control facilities designed for less extreme rainstorms should be tested with the 100-year design storm to ensure that the recommended runoff control plan does not aggravate the 100- year flood conditions. Presently, Santa Rosa County uses the 100-year - flood elevation to determine minimum acceptable floor elevations for new development. Floodplain development regulations should also require that loss of storage and conveyance capacity within the 100-year floodplain, as the result of development activities, be compensated for by providing off-setting storage within the floodplain. Similarly, the 50-year flood is also a rather extreme event which is likely to require extremely expensive control measures. The only facilities which are typically designed for a 50-year event are the Santa Rosa County and FOOT bridges and stream crossings. The 50-year high-water mark for small land- locked lakes may also be used as a sound standard for defining the floodplain in these basins. The 25-year design storm tends to be the most commonly used "extreme" event for stormwater facility design in Florida, Santa Rosa County drainage tm: SANTA ROSA: Y 5-3 regulations should stipulate its use in design of external subdivision drainage facilities and detention basins. The justification typically given for selecting the 25-year event for stormwater facility design is that it is more conservative than the 10-year design storm typically used for local storm sewer design, but less conservative than the 50- and 100-year events which would require more expensive runoff control measures that would be used infrequently. Based upon a recent Army Corps of Engineers study of nation- wide flood damage data compiled by the Federal Insurance Administration (FIA), additional justification for selecting the 25-year flood event is now available. Using generalized relationships between flood depth and damages for different types of property and generalized elevation-frequency relationships for different severities of flood hazard, the significance of different flood return periods was evaluated, This study concluded that the average annual flood damages within the 25-year floodplain are very high, typically up to ten times greater than the damages associated with the incremental area between the 25-year and 100-year floodplains. This conclusion suggests that a 25-year design event is both a reasonable and defensible upper limit for a stormwater management facility design. The 5- and 10-year storm events are appropriate design events for the design of closed storm sewer systems in urbanized drainage basins and subdivisions. The proposed stormwater regulations for Santa Rosa County stipulate the use of the 5-year design storm for both evaluation and design of these type of urban stormwater management facilities. tm: SANTA ROSA: Y 5-4 The 2-year flood event, generally described as the "mean annual flood", is typically equivalent to an open channel bankfull flow condition which will govern the cross-sectional area of the incised channel. If future development increases the 2-year flow, the stream channel will eventual-ly be eroded until it reaches an equilibrium condition with a conveyance capacity equivalent to the 2-year flow. Thus, comparisons of pre-and post-development 2-year flows can be used to evaluate potential stream channel erosion impacts of future development. 5.3.2 Rainfall Duration From various studies of past major rainfall events that have occurred in the southeastern portion of the United States, and in the northwest portion of Florida in particular, it is apparent that a large portion of the total rainfall of most major storms occurs within a 24-hour period. Water Management District regulations, excluding the NWFWMD, typically stipulate the use of a 25 year/24 hour duration design storm event for the design of stormwater detention ponds for new development. This requirement is dictated by the need to address the total volume of runoff from a design storm event of given frequency in the design of such facilities. Santa Rosa County stormwater regulations should be consistent with Water Management District regulations in this aspect. From the design, perspective for stormwater conveyances such as ditches, inlets, storm sewers, and culverts, it is the peak rate of runoff that is the critical design factor, not the total volume of runoff. Hence a shorter tm: SANTA ROSA: Y 5-5 duration storm event can be utilized in the evaluation and design of these facilities. A 6-hour duration design rainfall is recommended for Santa Rosa County. In accordance with the design criteria for hydrologic studies which mandatelt that the duration of the design rainfall should be approximately equal to or greater than the time of concentration of the basin, a 6-hour duration should be sufficient for any application within the County for determination of design peak flow rates. 5.3.3 Rainfall Volume Water Management Districts, excluding the NWFWMD, typically approve the use of the Department of Commerce's Technical Paper No. 40 as a reference for the design storm rainfall volume within the state. FDOT's new Drainage Manual (1987) utilizes this reference in addition to the more recent NOAA Technical Memorandum NWS HYDRO-35 "five to 60-Minute Precipitation Frequency for the Eastern and Central United States" publication to develop its set of rainfall intensity-duration-frequency (IDF) curves. Table 5-1 presents an appropriate set of IDF curves and design rainfall volumes for use within the County. These IDF curves were derived from these sources specifically for the Santa Rosa County. tm: SANTA ROSA: Y 5-6 5.3.4 Rainfall Distribution Peak runoff rates for a small (less than 100 acres in size and less than 30- minute time- of-concentration) urban drainage basin can be determined using the Rational Method. This method requires only a design rainfall intensity .-which corresponds to the time-of-concentration at the design point for the specified design return period. Table 5-1 presents a set of -rainfall intensity- duration-frequency (IDF) relationships for Santa Rosa County to be used in the Rational Method. Since the Rational Method generates design peak flow rates, it is inappropriate to develop design storm hydrographs or determine runoff volumes. For these purposes, or for large basins (greater than 100 acres in size or longer than 30-minute time-of-concentration) an alternate methodology which uses unit hydrograph theory must be used. This method requires a design storm hyetograph which distributes a design storm rainfall volume over its duration at discrete time steps. Tables 5-2 and 5-3 present dimensionless design storm distributions for the design 24-hour and 6-hour duration storm events, respectively. An example of a 24-hour storm distribution, listed in 30-minute increments, is the SCS Type II Florida - Modified Distribution; it is required for use in the design of stormwater detention and retention ponds per SWFWMD regulations. The 6-hour storm distribution is broken down into smaller, 10-minute time tm: SANTA ROSA: Y 5-7 TABLE 5-1 RAINFALL INTENSITY, IN/HR (VOLUME, IN.) RETURN PERIOD, YEARS DURATION 2-YR 5-YR 10-YR 25-YR 50-YR 100-YR 5-min 6.60 (0.55) 7.45 (0.62) 8.15 (0.68) 9.10 (0.76) 9.95 (0.83) 10.80 (0.90) 10-min 5.70 (0.95) 6.45 (1.07) 7.10 (1.18) 8.00 (1.33) 8.70 (1.45) 9.50 (1.58) 15-min 4.90 (1.22) 5.55 (1.39) 6.10 (1.53) 6.90 (1.73) 7.55 (1.89) 8.20 (2.05) 20-min 4.30 (1.43) 5.00 (1.67) 5.50 (1.83) 6.35 (2.18) 7.00 (2.33) 7.60 (2.53) 30-min 3.55 (1.75) 4.20 (2.10) 4.70 (2.35) 5.40 (2.70) 6.00 (3.00) 6.55 (3.30) 45-min 2.80 (2.10) 3.35 (2.50) 3.70 (2.80) @4.35 (3.25) 4.85 (3.65) 5.30 (4.00) I-hr 2.35 (2.35) 2.85 (2.85) 3.20 (3.20) 3.75 (3.75) 4.15 (4.15) 4.55 (4.55) 1.5-hr 1.80 (2.70) 2.25 (3.40) 2.50 (3.75) 2.90 (4.35) 3.20 (4.80) 3.55 (5.35) 2-hr 1.50 (3.00) 1.90 (3.801 2.10 (4.20) 2.40 (4.80) 2.70 (5.40) 2.95 (5.90) 3-hr 1.10 (3.30) 1.40 (4.20) 1.60 (4.80) 1.80 (5.40) 2.05 (6.10) 2.25 (6.70) 4-hr 0.90 (3.60) 1.15 (4.60) 1.30 (5.20) 1.52 (6.10) 1.70 (6.80). 1.90 (7.60) 6-hr 0.68 (4.08) 0.87 (5.25) 1.00 (6.00) 1.17 (7.00) 1.30 (7.80) 1.45 (8.70) 9-hr 0.51 (4.60) 0.66 (5.95) 0.75 (6.75) 0.88 (7.90) 1.00 (9.00) 1.10 (9.90) 12-hr 0.42 (5.10) 0.54 (6.50) 0.62 (7.50) 0.73 (8.80) 0.81 (9.70) 0.91 (10.9) 18-hr 0.31 (5.60) 0.41 (7.40) 0.46 (8.30) 0.55 (9.90) 0.62 (11.2) 0.69 (12.4) 24-hr 0.25 (6.00) 0.33 (7.80) 0.38 (9.10) 0.45 (10.7) 0.50 (12.0) 0.57 (13.6) SOURCES: (1) NOAA Technical Memorandum NWS HYDRO-35, FIVE TO 60 MINUTE PRECIPITATION FREQUENCY FOR THE EASTERN AND CENTRAL UNITED STATES, 1977. (2) Technial Paper No. 40, RAINFALL FREQUENCY ATLAS OF THE UNITED STATES FOR DURATIONS FROM 30 MINUTES TO 24 HOURS AND RETURN PERIODS FROM I TO 100 YEARS, 1961. (3) STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION, DRAINAGE MANUAL, VOLUME 2, PROCEDURES, 1987. tm:SANTA ROSA:Z TABLE 5-2 DESIGN STORM RAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TaTAL TIME, HRS. 24-HOUR RAINFALL 24-HOUR RAINFALL 0.0 0.000 0.000 0.5 0.006 0.006 1.0 0.012 0.006 1.5 0.019 0.007 2.0 0.026 0.007 2.5 0.034 0.008 3.0 0.042 0.008 3.5 0.050 0.008 4.0 0.059 0.008 4.5 0.068 0.009 5.0 0.078 0.010 5.5 0.088 0.010 6.0 0.099 0.011 6.5 0.110 0.011 7.0 0.122 0.012 7.5 0.135 0.013 8.0 0.149 0.014 8.5 0.164 0.015 9.0 0.180 0.016 9.5 0.200 0.020 10.0 0.224 0.024 10.5 0.253 0.029 11.0 0.289 0.036 11.5 0.343 0.054 12.0 0.593 0.250 12.5 0.689 0.096 13.0 0.731 0.042 13.5 0/763 0.032 14.0 0.789 0.026 14.5 0.811 0.022 15.0 0.829 0.018 15.5 0.844 0.015 16.0 Q.858 0.014 16.5 0.871 0.013 17.0 0.883 0.012 tm: SANTA ROSA: Y 5-9 TABLE 5-2 (Continued) DESIGN STORM RAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TOTAL TIME, HRS. 24-HOUR RAINFALL 24-HOUR RAINFALL 17.5 0.894 0.011 18.0 0.905 0.011 18.5 0.915 0.010 19.0 0.925 0.010 19.5 0.934 0.009 20.0 0.943 0.009 20.5 0.951 0.008 21.0 0.959 0.008 21.5 0.967 0.008 22.0 0.974 0.007 22.5 0.981 0.007 23.0 0.988 0.007 23.5 0.994 0.006 24.0 1.000 0.006 TOTAL 1.000 tm: SANTA ROSA: Y 5-10 TABLE 5-3 DESIGN STORM RAINFALL DISTRIBUTION I 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION ACCUMULATED INCREMENTAL,;.- FRACTION OF TOTAL FRACTION OF TOTAL TIME, HRS. 6-HOUR RAINFALL 6-HOUR RAINFALL 0 0.000 0.000 0.17 0.010 0.010 0.33 0.020 0.010 0.50 0.030 0.010 0.67 0.041 0.011 0.83 0.053 0.012 1.00 0.065 0.012 1.17 0.078 0.013 1.33 0.092 0.014 1.50 0.107 0.015 1.67 0.123 0.016 1.83 0.140 0.017 2.00 0.159 0.019 2.17 0.181 0.022 2.33 0.209 0.028 2.50 0.244 0.035 2.67 0.290 0.046 2.83 0.370 0.080 3.00 0.559 0.189 3.17 0.672 0.113 3.33 0.732 0.060 3.50 0.772 0.040 3.67 0.803 0.031 3.83 0.828 0.025 4.00 0.848 0.020 4.17 0.866 0.018 4.33 0.882 0.016 4.50 0.897 0.015 4.67 0.911 0.014 4.83 0.924 0.013 5.00 0.937 0.013 5.17 0.949 0.012 5.33 0.960 0.011 5.50 0.971 0.011 .5.67 0.981 0.010 5.83 0.991 0.010 6.00 1.000 0.009 TOTAL 1.000 tm: SANTA ROSA: Y 5-11 increments, and should be used to generate design peak flows and hydrographs for applications on which the smallest drainage subbasin being analyzed has a time-of-concentration less than 30 minutes. The 6-hour duration design storm distribution was derived by the methodology originally employed by the SCS to derive the Type II Florida-Modified distribution. This procedure, as documented in "Interim Runoff Procedure for Florida", SCS Florida Bulletin Number 210-1-2, utilizes the rainfall volumes listed -in NWS publications HYDRO-35 and TP-40 to obtain a set of design storm rainfall increments for a storm of given recurrence interval and duration. These discrete rainfall increments are arranged in the design storm by placing the largest increment in the middle of the storm event distribution. The second largest increment is placed after the first and the third largest is placed before the first. Alternating the remaining rainfall amounts continues in the same manner until the entire storm distribution is completed. tm:SANTA ROSA:Y 5-12 0 1.,w- . I C SECTION IX A@ SE 7SIX@ -9 I Section 6 FACILITIES ASSESSMENT 6.1 CAPACITY AND DEMAND CALCULATIONS The assessment of the ability of stormwater facilities ability to meet the defined service levels, as previously discussed, requires an analysis of the facility capacity and an estimation of peak flow (demand) for the primary drainage systems within Santa Rosa County. By a comparison of the two, it can be determined whether specific drainage facilities are of sufficient ca@-pacity to meet the designated service level or whether an upgrade is necessary to satisfy the expected demand. 6.2. FACILITY CAPACITY ANALYSIS Storm drainage facility capacity is a complicated technical parameter that is difficult to assess at a planning level. An accurate engineering determination requires a detailed hydraulic analysis of each element of the stormwater conveyance system including physical parameters of size, slope, elevation, roughness, and cross section area. Many of these parameters were unknown for Santa Rosa County and were estimated from USGS 7.5' quadrangle ma ps. For the purpose of this analysis, critical drainage facilities within the County were identified and capacities were calculated assuming as limiting tm: SANTA ROSA: KK 6-1 conditions. The resulting capacity estimate for each drainage critical facility is summarized in Table 6-1 by basin. 6.3 FACILITY DEMAND AND RESIDUAL CAPACITY ANALYSIS The estimation of a design peak flow (demand) at a given storm drainage facility was calculated using the Rational Method, a ppro pri ate basin characteristics and local experience Methodology. The residual facility capacity is calculated by subtracting the estimated demand (peak flow) from the estimated capacity for each facility. A positive residual valve indicates that the facility has adequate capacity while a negative valve indicates that the facility is unable to pass the basin/subbasin demand. This methodology was modified somewhat in order to estimate future demands. Recognizing that under "Pre-/Post" match regulation schemes some increase in runoff will occur due to infill, gentrification, and redevelopment incentives, a method to recognize this phenomena was employed. Generally, increased land use intensity was recognized as "Net 10V increase. However, as the degree of land use intensity changes, so does the net change for future conditions. Engineering judgement of basin development potential was used to assess flows under future conditions assuming a "net 10V concept. Table 6-2 presents the estimated demands and residual capacities for individual facilities for current conditions by basin. Table 6-3 presents the same information estimated for future conditions. tm:SANTA ROSA:KK 6-2 Table 6-1 SUMMARY OF STRUCTURE CAPACITY FOR CRITICAL DRAINAGE STRUCTURES UPSTREAM STRUCTURE STRUCTURE DRAINAGE STRUCTURE NUMBER DESCRIPTION AREA CAPACITY (ACRES) (CFS) --------------------------------------- --------------------- BASIN 01 - ESCAMBIA RIVER BASIN 0101-925 8' x 3' box culvert 240 115 0101-930 Twin 309 RCP 70 30 0101-940 Triple 360 RCP 55 69 0101-945 Tvin-8' x 4' box culverts 200 300 0101-950 Twin 480 RCP 22 lee 0101-955 Twin 309 RCP 17 28 0101-980 8' x 4' box culvert 300 145 0101-985 8' x 4' box culvert 130 145 BASIN 02 - ESCAMBIA BAY COASTAL BASIN 0201-905 Triple 489 RCP 220 138 0201-910 Twin 360 RCP lee 43 0201-915 2.5' x 3.5' CMAP '70 28 0201-930 Twin 541 RCP 140 128 0201-945 Triple 361 RCP 200 66 0201-980 Single 480 RCP 210 50 0202-915 Triple 240 RCP 176 24 0202-960 10' x 6' box culvert 735 430 BASIN 03 - POND CREEK BASIN 0302-915 Twin 480 RCP 129 1" 0302-920 12' x 14' box culvert 4" 12" 0302-925 Twin 10' x 3' box culvert 160 280 BASIN 04 - EAST BAY COASTAL BASIN 0401-105 3' x 10' box culvert 702 150 0401-205 8' x S' box culvert 386 430 0401-945 Twin 42* RCP 69 68 0401-950 10' x 3' box culvert 425 156 0404-005 Triple 421 x 608 CHP 154 150 0404-920 Triple 780 RCP 320 540 0409-975 12' x 4' box culvert 169 275 Env56/2 6-3 Table 6 -1 SUMMARY OF STRUCTURE CAPACITY FOR CRITICAL DRAINAGE STRUCTURES (CONTINUED) UPSTREAM STRUCTURE STRUCTURE DRAINAGE STRUCTURE NUMBER DESCRIPTION AREA CAPACITY (ACRES) (CFS) ------------------------------------------------------------- BASIN 05 - BLACKWATER RIVER BASIN 0501-020 Twin 60R-CHP 279 is@ 0501-930 362 x 24* box culvert 18 15 0501-945 7' x 2' box culvert 96 50 BASIN 06 COLDWATER CREEK BASIN 0601-020 12' x 4' box culvert 224 310 0601-905 12' x 4' box culvert 320 310 0601-910 Twin 6' x 3' box culvert 205 136 0601-915 Triple 361 RCP 205 69 0601-920 8' x 2' box culvert 256 68 BASIN 07 BIG JUNIPER CREEK BASIN (no critical structures) BASIN 08 YELLOW RIVER BASIN 0802-905 Twin 609 CHP 600 180 0802-910 Single 840 CHP 1200 210 BASIN 09 EAST BAY RIVER BASIN (no critical structures) BASIN 10 SANTA ROSA SOUND COASTAL BASIN 1002-920 Triple 369 RCP 68 69 1002-925 Triple 360 RCP 34 66 1002-945 Singlo 489 RCP 89 50 1002-950 8' x 6' box culvert 154 300 Env56/2 6-4 Table 6-2 SUMMARY OF FACILITY CAPACITY, DEMAND AND RESIDUAL CAPACITY FOR CURRENT CONDITIONS FOR CRITICAL STRUCTURES CURRENT STRUCTURE STRUCTURE STRUCTURE CURRENT RESIDUAL NUMBER DESCRIPTION CAPACITY DEMAND CAPACITY (CFS) (CFS) (CFS) ------------------------------------------------------- 7------------------ BASIN 01 - ESCAMBIA RIVER BASIN 0101-925 8' x 3' box culvert 115 192 -77 0101-930 Twin 300 RCP 30 71 -41 0101-940 Triple.361 RCP 69 53 16 0101-945 Twin 8' x 4' box culverts 300 2" lee 0101-950 Twin 489.RCP lee 21 79 0101-955 Twin 300 RCP 28 15 13 0101-980 S' x 4' box culvert 145 240 -95 0101-985 8' x 4' box culvert 145 139 15 BASIN 02 - ESCAMBIA BAY COASTAL BASIN 0201-905 Triple 480 RCP 138 202 -64 0201-910 Twin 360 RCP 43 84 -41 0201-915 2.5' x 3.5' CHAP 28 56 -28 0201-930 Twin 540 RCP 12a 168 -40 0201-945 Triple 360 RCP 66 2M -142 0201-980 Single 48* RCP 50 168 -118 0202-915 Triple 240 RCP 24 155 -131 0202-960 10' x 6' box culvert 430 646 -216 BASIN 03 - POND CREEK BASIN 0302-915 Twin 480 RCP in 120 -20 0302-920 12' x 14' box culvert 12" 442 758 0302-925 Twin 10' x 3' box culvert 286 128 152 BASIN 04 - EAST BAY COASTAL BASIN 0401-105 3' x 19' box culvert 156 618 -468 0401-205 S' x 8' box culvert 439 340 90 0401-945 Twin 426 RCP 68 61 7 0401-950 10' x 3' box culvert 156 374 -224 0404-005 Triple 428 x 609 CHP 150 135 15 0404-920 Triple 7ag RCP 549 282 258 0409-975 12' x 4' box culvert 275 147 128 Env5612 6-5 Table 6-2 SUMMARY OF FACILITY CAPACITY, DEMAND AND RESIDUAL CAPACITY FOR CURRENT CONDITIONS FOR CRITICAL STRUCTUES (CONTINUED) CURRENT STRUCTURE STRUCTURE STRUCTURE CURRENT RESIDUAL NUMBER DESCRIPTION CAPACITY DEMAND CAPACITY (CFS) (CFS) (CFS) ------------------------------------------------------------------------- BASIN 05 - BLACKWATER RIVER BASIN 0501-020 Twin 600 CMP 189 245 -65 @501-930 360 x 240 box culvert 15 33 -19 0501-945 7' x 2' box culvert 50 154 -104 BASIN 06 - COLDWATER CREEK BASIN 0601-020 12' x 4' box culvert 319 243 67 0601-905 12' x 4' box culvert 318 2a2 2a 0601-910 Twin 6' x 3' box culvert 136 1" -44 0601-915 Triple 369 RCP 69 1" -111 0601-920 8' x 2' box culvert 68 225 -157 BASIN 07 - BIG JUNIPER CREEK BASIN (no critical structures) BASIN 08 - YELLOW RIVER BASIN 0802-905 Twin 601 CMP 1" 528 -348 .0802-910 Single 840 CHP 219 1056 -846 BASIN 09 - EAST BAY RIVER BASIN (no critical structures) BASIN 10 - SANTA ROSA SOUND COASTAL BASIN 1002-920 Triple 369 RCP 69 60 9 1002-925 Triple 366 RCP 66 41 25 1002-945 Single 481 RCP 56 107 -57 1002-950 8' x 6' box culvert 308 154 146 Env56/2 6-6 Table 6 -3 SUMMARY OF FACILITY CAPACITY, DEMAND AND RESIDUAL CAPACITY FOR FUTURE CONDITIONS FOR CRITICAL STRUCTURES FUTURE STRUCTURE STRUCTURE FUTURE RESIDUAL NUMBER DESCRIPTION DEMAND CAPACITY (CFS) (CFS) --------------------------------------------------------- BASIN 01 - ESCAMBIA RIVER BASIN 0101-925 8' x 3' box culvert 221 -106 0101-930 Twin 301 RCP 74 -44 0101-940 Triple 361 RCF 61 8 0101-945 Twin 8' x 4' box culverts 210 90 0101-950 'Twin 489 RCP 23 77 0101-955 Twin 30F RCP 16 12 0101-980 8`x 4' box culvert 276 -131 0101-985 8' x 4' box culvert 150 -5 BASIN 02 ESCAMBIA BAY COASTAL BASIN 0201-905 Triple 489 RCP 212 -74 0201-910 Twin 361 RCP as -45 0201-915 2.5' x 3.5' CMAP 59 -31 0201-930 Twin 541 RCP 176 -48 0201-945 Triple 360 RCP 218 -152 0201-980 Single 489 RCP 176 -126 0202-915 Triple 240 RCP 171 -147 0202-960 10' x 6' box culvert 678 -248 BASIN 03 - POND CREEK BASIN 0302-915 Twin 481 RCP 126 -26 0302-920 12' x 14' box culvert 464 736 0302-925 Twin 10' x 3' box culvert 141 139 BASIN 04 - EAST BAY COASTAL BASIN 0401-105 3' x 10' box culvert 649 -499 e401-205 a' x 8' box culvert 357 73 0401-945 Twin 422 RCP 64 4 0401-950 10' x 3' box culvert 411 -261 0404-005 Triple 422 x 600 CHP 149 2 0404-920 Triplo 780 RCP 310 230 0409-975 12' x 4' box culvert 169 106 Env5612 6 -7 Table 6 -3 SUMMARY OF FACILITY CAPACITY, DEMAND AND RESIDUAL CAPACITY FOR FUTURE CONDITIONS FOR CRITICAL STRUCTURES (CONTINUED) FUTURE STRUCTURE STRUCTURE FUTURE RESIDUAL NUMBER DESCRIPTION DEMAND CAPACITY (CFS) (CFS) --------------------------------------- --------------- BASIN 05 - BLACKWATER RIVER BASIN 0501-020 Twin 600 CHP 257 -77 0501-930 369 x 240 box culvert 36 -22 0501-945 7' x 2' box culvert 169 -119 BASIN 06 COLDWATER CREEK BASIN 0601-020 12' x 4' box culvert 255 55 0601-905 12' x 4' box culvert 296 14 0601-910 Twin 6' x 3' box culvert 189 -53 0601-915 Triple 361 RCP 189 -120 0601-920 8' x 2' box culvert 236 -168 BASIN 07 BIG JUNIPER CREEK BASIN (no critical structures) BASIN 08 - YELLOW RIVER BASIN 0802-905 Twin 600 CHP 554 -374 0802-910 Single 849 CHP 1162 -952 BASIN 09 - EAST BAY RIVER BASIN (no critical structures) BASIN 10 - SANTA ROSA SOUND COASTAL BASIN 1002-920 Triple 369 RCP 78 -9 1002-925 Triple 360 RCP 55 11 1002-945 Single 480 RCP 139 -89 1002-950 S' x 6' box culvert 193 108 Env56/2 6-8 0 z I E SECTIONS EN @ E G @ DN I Section 7 FACILITY NEEDS ANALYSIS 7.1 GENERAL Only in the recent past has stormwater service been likened to highway capacities by defining levels of service with the performance of stormwater management systems being ranked on a relative continuum from good to bad for a given design storm. This section examines the concept of service levels for stormwater management systems, recommends specific service level definitions and assesses both existing and anticipated future levels of service attainment for the County's current system. 7.2 SERVICE LEVEL DEFINITIONS The selection of appropriate performance criteria is a policy issue which has significant budget consequences. If criteria are selected which are too conservative the cost of solutions to existing drainage problems become overly expensive. Conversely, if the selected criteria are too lax, the resultant system does not meet the intended level of service. Clearly a policy issue which must be resolved is the appropriate level of service. Good performance for a rural system might be defined as minor street flooding while bad performance may be defined as structure flooding. It is fair to say that every portion of every service area does not require the highest level of service at all times for all events. Many areas can tolerate a limited amount of street or yard flooding if it does not last very long and is not frequently ex peri enced. tm: SANTA ROSA: KK 7-1 Santa Rosa County experiences flooding from a variety of rainfall events. The degree of severity of flooding by its impacts: roadway flooding, yard flooding or structure flooding. Four service levels were defined based upon these severity classifications: 0 Service Level A: Ditch Flow Only 0 Service Level B: Street Flooding 0 Service Level C: Street and Yard Flooding 0 Service Level D: Street, Yard and Structure Flooding While these definitions seem rather simplistic, they represent a classification system that facilitates evaluation of overall system performance and the prioritization of funding for stormwater management system construction, 0 & M and development. The individual service levels are defined functionally in terms of the performance criteria for the stormwater management system. The development of service level criteria involves a compromise between an academic approach and the availability of usable data for cross-section profiles of the roadway, right-of-way, yard and finish floor of structures. The proposed performance criteria for each service level utilize available topographic and aerial photographic information in conjunction with functional criteria definitions which are valid in most instances: 0 Service Level A: Water Contained Within Ditches No flooding of major roadways, minor roadways, yards or structures. The hydraulic grade line (free water surface) is generally at or below the inlet throat. tm: SANTA ROSA: KK 7-2 0 Service Level B: Water Contained Within Right-of-Way Flooding of major roadways is limited to the outer lane but does not prevent travel, i.e., limited duration flooding of minor streets, flooding of yards generally limited to the right-of-way but no flooding of structures. The hydraulic grade line is at or slightly above the inlet throat. 0 Service Level C: Water contained Within the Front Yard Flooding of major roadways precludes the use of outer lane and travel in inner lanes is possible but difficult, prolonged flooding of minor streets which precludes travel, flooding of front yards up to the front face of the structure but no flooding of the structure. The hydraulic grade line is significantly above the inlet. 0 Service Level D: Structure Flooding Extensive flooding of streets, yards and structures for prolonged periods. Clearly, the existence o.f Service Level D conditions represent a stormwater manager's nightmare and is never an acceptable design condition. However, virtually any system may suffer Service Level D performance if subjected to a severe enough rainfall event. It is recommended that these definitions be reviewed by the County staff and then formally adopted as a basis for setting stormwater service levels, throughout the County. 7.3 SERVICE LEVEL ATTAINMENT Specific quantitative levels of service have not been adopted for drainage facilities in Santa Rosa County. Consequently, it is not possible to evaluate performance of individual facilities against specific quantitative standards. The foregoing general service levels definitions for Service Level A-D are tm: SANTA ROSA: KK 7-3 recommended for adoption by the County. However, until they are formally adopted, the definitions will be used for discussion purposes. Service Level attainment can be estimated for each facility based on the residual capacity estimated in Section 6 for both current and future conditions. Criteria used in attributing service level attainment, in the absence of detailed site-specific studies and adopted service level criteria, are briefly summarized as follows: Service Level A: Passes the estimated peak flow Service Level B: Capacity shortfall for the estimated storm is wit-hin 50% of estimated capacity Service Level C: Capacity shortfall for the design storm is between 50% and 110% of estimated capacity Service Level D: Capacity shortfall for the design storm exceeds 110% of estimated capacity Estimated service levels for each of the critical structures preveiously analyzed in Section 6 are summarized in Table 7-1 for both current and anticipated future conditions. 7.4 ANALYSIS OF BASIN PERFORMANCE The evaluation of estimated service levels for critical structures under current conditions indicates that the County can expect to attain Service Level A in approximately 43 % of its primary facilities with about 43 % of tm: SANTA ROSA: KK 7-4 Table 7-1 SUMMARY OF SERVICE LEVEL ATTAINMENT FOR CRITICAL STRUCTURES FOR CURRENT AND FUTURE SERVICE DEMANDS ESTIMATED ESTIMATED STRUCTURE STRUCTURE CURRENT FUTURE NUMBER DESCRIPTION SERVICE SERVICE LEVEL LEVEL ------------------------------------------------------------- BASIN 01 - ESCAMBIA RIVER BASIN 0101-925 80 x 31 box culvert C C 0101-930 Twin 300 RCP D D 0101-940 Triple 361 RCP A A 0101-945 Twin 8' x 4' box culverts A A 0101-950 Twin 481 RCP A A @lei-955 Twin 301 RCP A A alai-980 8' x 4' box culvert C C 0101-985 8' x 4' box culvert A B BASIN 02 - ESCAMBIA BAY COASTAL BASIN 0201-905 Triple 489 RCP B C 0201-910 Twin 368 RCP C C 0201-915 2.5' x 3.5' CHAP C C 0201-930 Twin 540 RCP B B 0201-945 Triple 360 RCP D D 0201-980 Single 480 RCP D D 0202-915 Triple 240 RCP D D e202-960 10' x 6' box culvert C BASIN 03 - POND CREEX BASIN 0302-915 Twin 480 RCP B B 0302-920 12' x 14' box culvert A A 0302-925 Twin 10' x 3' box culvert A A BASIN 04 - EAST BAY COASTAL BASIN 0401-105 3' x 10' box culvert D D 0401-205 8' x S' box culvert A A 0491-945 Twin 421 RCP A A 0401-950 10' x 3' box culvert D D 0404-005 Triple 420 x 606 CHP A A 0404-920 Triple 780 RCP A A 0409-975 12' x 4' box culvert A A Env56/2 7-5 Table 7-1 SUMMARY OF SERVICE LEVEL ATTAINMENT FOR CRITICAL STRUCTURES FOR CURRENT AND FUTURE SERVICE DEMANDS (CONTINUED) ESTIMATED ESTIMATED STRUCTURE STRUCTURE CURRENT FUTURE NUMBER DESCRIPTION SERVICE SERVICE LEVEL LEVEL ------------------------------------------------------------- BASIN 95 - BLACKWATER RIVER BASIN 0501-020 Tvin 601 CHP B B 0501-930 360 x 240 . box culvert. D D 0501-945 7' x 2' box culvert D D BASIN 06 COLDWATER CREEK BASIN 0601-020 12' x 4' box culvert A A 0601-905 12' x 4' box culvert A A 0601-910 Tvin 6' x 3' box culvert B B 0601-915 Triple 361 RCF D D 0601-920 8' x 2' box culvert D D BASIN 07 BIG JUNIPER CREEK BASIN (no critical structures) BASIN 08 YELLOW RIVER BASIN 0802-905 Tvin 609 CHP D D 0802-910 Single 848 CHP D D BASIN 09 EAST BAY RIVER BASIN (no critical structures) BASIN 10 SANTA ROSA SOUND COASTAL BASIN 1062-920 Triple 369 RCP A 6 1002-925 Triple 360 RCP A A 1002-945 Single 481 RCP D D 1002-950 8' x 6' box culvert A A Env56/2 7-6 the facilities falling below Service Level B. Table 7-2 summarizes service level attainment for current conditions by basin. Table 7-3 presents service level attainment results for critical structures by basin for future conditions. The County should expect to obtain Servicell-evel A in about 38 % of its facilities which represents a 12 % decrease due to growth. Service will drop below Service Level B for approximately 48 % of its facilities. tm:SANTA ROSA:KK 7-7 TABLE 7-2 SUMMARY OF SERVICE LEVEL ATTAINMENT FOR CURRENT LAND USE CONDITIONS Service Level - Number of Basin A B C D Systems 1. Escambia River 5 a 2 1 62.50 a.@@ 25.00 12.58 2. Escambia Bay Coastal a 3 2 3 0.00 37.59 25.08 37.50 3. Pond Creek 2 1 0 a 3 66.67 33.33 8.00 0.86 4. East Bay Coastal 5 9 9 2 7 71.43 0.00 9.00 28.57 5. Blackwater River I 1 0 2 3 0.09 33.33 6.80 66.67 6. Coldwater Creek 2 1 a 2 5 40.00 28.00 0.80 46.80 7. Big Juniper Creek 0 0 0 S. Yellow River 0 2 2 0.00 @. so 0.00 189.89 9. East Bay River 18. Santa Rosa Sound 3 0 4 75.00 0.00 6.00 25.06 COLKTY TOTAL 17 6 4 13 49 42.50 15.90 11L 00 32.58 7-8 Table 7 -3 SUMMARY OF SERVICE LEVEL ATTAINMENT FOR FUTURE LAND USE CONDITIONS Service Level Number of Basin A B C D Systems 1. Escambia River 4 1 2 1 8 50.00 12.50 25.00 12.50 2. Escambia Bay Coastal 0 1 4 3 8 0.00 12.50 50.90 37.59 3. Pond Creek 2 1 1 0 3 4. East Bay Coastal 5 9 9 2 7 71.43 S.W 6.08 28.57 5. Black*ater River I I 1 2 3 6.06 33.33 8.06 66.67 6. Coldwater Creek 2 1 0 2 5 40.89 20.80 0.00 40.00 7. Big Juniper Creek 0 a a a 0 0 0 8 a 8. Yellow River 0 0 8 2 2 0.00 a@ 0.00 9. East Bay River a 0 a 0 0 0 0 a a 18. Santa Rosa Sound 2 1 a 1 4 50.00 25.00 0.00 25.00 COLKrY TOTAL 15 6 6 13 40 37.50 15.88 15.80 32.50 7-9 0 .0 ( SECTION EIGHT S E C allTD .* I Section 8 FUNDING NEEDS AND IMPLEMENTATION PROGRAM 8.1 GENERAL This section evaluates Santa Rosa County's overall funding needs, develops a plan to implement the program over the next 20 years, and reviews funding mechanisms needed to provide the funds for the program. 8.2 CAPITAL NEEDS ASSESSMENT The results of the County-wide drainage planning study has been the identification of a number of specific Capital Improvements Program (CIP) projects and the need to conduct basin specific studies to identify the cause of and solution for future problems indicated by the facilities analysis. A total of forty-seven individual activities were identified to solve current, recurring problems which require the expenditure of approximately $3,555,685 of capital funds for new or upgraded facilities. This figure includes one project which is in the FDOT budget. When this one capital expenditure is removed, it reduces the CIP needs to $1,755,685. The individual activities are summarized in Table 4-1 found in Section 4. Additionally, twenty-three potential future CIP projects were identified and are shown in Table 8-1. Both of these tables (Table 4-1 and 8-1) are also shown in Appendix B of this report. The largest expenditure for the current recurring problems is $437,500 and is found in the Pond Creek Basin while the Big Juniper Creek Basin requires no immediate expenditure. tm:SR/2MM 8-1 TABLE 8-1 SUMMARY OF POTENTIAL FUTURE CIP PROJECTS CIP Structure Predesign Number Number Description of Work Co-st Escambia River Basin 1. 0101-925 Add Parallel 8'x3' Box Culvert $ 30,400 2. 0101-930 New Twin 48" Culverts 22,600 3. 0101-980 New Parallel 8'x4' Box Culvert 34,500 Basin Subtotal: $ 87,500 Escambia Bay Coastal Basin 4. 0201-905 New Twin 8'x4' Box Culverts $ 55,000 5. 0201-910 New Twin 48" Culverts 22,600 6. 0201-915 New Twin 48" Culverts 22,600 7. 0201-930 Add Parallel 54" Culvert 18,500 0201-945 New Triple 60" Culverts 48,900 0201-980 New Triple 54" Culverts 41,300 0202-915 New Triple 54" Culverts 41,300 0202-960 New 40' Bridge 64000 Basin Subtotal $315,000 Pond Creek Basin 12. 0302-915 Add Parallel 48" Culvert $ 14,200 East Bay Coastal Basin 13. 0401-105 New 40' Bridge $ 64,800 14. 0401-950 New Twin 5'xlO' Box Culverts 77,000 Basin Subtotal $141,800 Blackwater River Basin 15. 0501-020 Add Parallel 60" Culvert $ 22,500 16. 0501-930 New 48" Culvert 14,200 17. 0501-945 New S'xlO' Box Culvert 47,700 Basin Subtotal $ 84,400 40 tm:SR2/MM 8-2 TABLE 8-1 (Continued) CIP Structure Predesign Number Number Description of Work Cost Coldwater Creek Basin 18. 0601-910 New Twin 4'x8' Box Culverts $ 55,000 19. 0601-915 New Twin 4'x8' Box Culverts 55,000 20. 0601-920 New Twin 4'x8' Box Culverts 55,000 Basin Subtotal $165,000 Yellow River Basin 21. 0802-905 New Twin 4'x8' Box Culverts $ 55jOOO 22. 0802-905 New 60' Girder Bridge 108,000 Basin Subtotal $163,000 Santa Rosa Sound Coastal Basin 1002-945 New Twin 54" Culverts $ 29,600 COUNTY-WIDE TOTAL: $1,000,500 tm:SR2/MM 8-3 8.3 O&M NEEDS ASSESSMENT Proper O&M is the keystone to keeping existing facilities in their peak operational condition. Unfortunately the County's budget for stormwater related O&M activities is only approximately $ 50,000 annually and the res@lts of this limited budget are readily apparent. A very brief analysis of the County's major ditches, major culverts and key structures suggests a recurring need for programmed maintenance. Based on typical unit production rates, it would appear that an O&M budget allocation of $125,000 for first year maintenance rising to $220,000 in the year 2007 would allow maintenance of these facilities once per year. 8.4 IMPLEMENTATION PROGRAM The implementation program developed for Santa Rosa County consists of strategies for capital expenditures, annual O&M funding, continuing R&R expenditures and strategic basin-wide studies as well as an integrated funding needs assessment and a 20-year plan to solve the County's problems. 8.4.1 Capital Expenditures Strategy The expenditure 'program established for capital construction projects focuses on prioritized projects and seeks to complete all of the identified projects within a ten year period. Allowing 15% of the construction cost for survey, tm:SR2/MM 8-4 studies and designs, the annual expenditure required to achieve this program is $202,000 per year ove r the first ten years of the. program. The order of the projects within the current CIP list is based on the severity of the problem as estblished in Section 4. The severity and preliminary priority ranking are shown in Appendix 3-1, Summary of Current Identified CIP Projects. A second and major capital expenditure consideration is the repair and/or replacement (R&R) of existing facilities as they reach the end of their service life and begin to fail. The average service life of concrete and corrugated metal culverts has been estimated at 30-60 years depending upon their method of manufacture, protective coatings, installation procedures- and service environment. Recognizing that some of the facilities in the County have been in service since the 1940's, the County must be prepared to begin replacing and repairing these facilities as they fail. The @ounty should conduct a conditions survey in 1988 and 1989 to ascertain the general condition and remaining service life of its primary and secondary drainage facilities. Based upon this survey, the County should prioritize replacement and repair projects to prevent catastrophic system failures. Funding at $50,000 should be developed for the survey during the first two years. Upon completion of the survey, appropriate funding should be allocated for system improvements. For the purposes this study , the initial R&R funding in year 3 has been established at $30,000 and allowed to grow, of an tm:SR2/MM 8-5 annual rate to $220,000 by the year 2007. This growth rate seeks to compensate for the increasing rate of facilities replacement as the County's systems age. 8.4.2 Strategic Basin Studies Strategy Evaluation of service level degradation due to the impact of growth on undersized and inadequate structures indicate that the number of facilities falling below Service Level B standards will not increase significantly, changing from 22 to 23. The high number of critical structures already falling below Service Level C standards indicates that the County should initiate a series of comprehensive basin modelling studies to identify problems and select the best and most cost effective solutions. These studies should begin in the third year of the program and should be undertaken in the following basin order: Priority Basin Study Date Study Cost 1 Escambia Bay Coastal 1990,1991 $150,000 2 Escambia River 1992, 1994 $150,000 3 Blackwater River 1995,1996 $150,000 4 Coldwater Creek 1997, 1998 $100,000 5 Yellow River 1999 $ 50,000 6 East Bay Coastal 2000 $ 50,000 7 Santa Rosa Sound 2001 $ 50,000 8 Pond Creek 2002 $ 50,000 tm:SR2/MM 8-6 Also indicated is the year(s) the study should be undertaken and 'a very rough estimated current cost to evaluate the basin. Some studies, due to the size and complexity of the basins, will be very expensive and complicated and will take more time to complete. The County should monitor in each basin the year before the studies are conducted in order to have appropriate rainfallz--and runoff data to conduct the hydrologic and hydraulic simulations. 8.4.3 O&M Strategy Assuming that major facilities are maintained on a five year cycle and that the maintenance of minor systems is approximately twice as expensive.- but accomplished on a 10 year cycle, the County's annual O&M expenditure would be approximately $125,000 which is about two and one*-half times the current annual expenditure of $50,000. In order to achieve an adequate O&M funding program, the strategy used in this study is to raise the annual O&M funding level from its current level to the needed level of about $125,000. Thereafter, the O&M funding level would be raised at the rate of $5,000 yearly for twenty-five years to $ 220,000, which reflects the increasing O&M funding required to maintain the new facilities which are being constructed through the CIP construction projects., 8.4.4 Implementation Plan As discussed in the foregoing sections, the capital construction funding for both identified current CIP projects and unidentified future CIP projects, tm:SR2/MM 8-7 combined with the continuing need for annual O&M activities and an increasing need for R&R projects must be scheduled over a reasonable program implementation period. The results of this scheduling effort is the implementation plan. This study has evaluated the County's current and anticipated future needs for the next 20 years in an effort to develop a viable program. Utilizing the strategies described in Sections 8.4.1 through 8.4.3 as the basis, a long-term implementation plan was developed for Santa Rosa County. Table 8-2 summarizes planned expenditures in each area. These projections do not consider many of the daily activities already accomplished by the County's current stormwater management program. Overall, the County should try to pursue a real growth rate in its stormwater program of 2% to 5%. Inflation has not been considered in the foregoing analysis. Table 8-3 summarizes the difference in costs if a 5% continuous inflation rate is applied over the 20 years of the program. 8.5 PROGRAM FINANCING The County's stormwater management program must develop a stable and reliable financing program if it is to be successful and solve Santa Rosa's current and future stormwater problems. tm:SR2/MM 8-8 Table 8-2 SUMMARY OF STORMWATER FUNDING NEEDS Program Calendar Identified Repair and Operations Strategic Potential Total Year Year CIP Replacement Maintenance Basin Future CIP Funding Projects Costs Costs Studies Projects Required 1 1988 $282, M $25, M $125, WO mo, M Af 1989 $292, ON $25, ON $1387 on $357, ON 3 1990 sm'w $39, M $135, ON $75, NO W2, M 4 1991 s"k, M $35, M $140, W $75, NO $452, ON 5 1992 sm'm so, M $145, ON $75,000 $462, ON $75, WO $472, M 6 1993 sm'w $45, on $150, M 7 1994 sm'Ne $50, M $155, ON $75.W $482, ON 8 1995 $2&2, W $55, ON $160. ON $75, M $492, NO 9 19% sm'm $65, NO $165, ON $50, NO $482, NO 1@ 1997 $202, W $75, W $170, NO $50, M $497, ON 11 1998 $85, ON $175,M $50, ON $115. ON $4,05, NO 12 1999 $95.000 $188,M $50, ON $115 w. $440, ON 13 2ON 105, No s 185, ON $50, M $1151088 $455. NO 14 2081 $128,W8 $198, M $50, M $115,0W $475, ON 15 2002 $135, ON t 195, M s5a, On $115, M $4955. ON 16' 2003 $150, ON $2w, ON $115,N@ $465,000 17 2w $ 165, NO $M. ON $115, NO $485. ON 18 2M $188, On $210, NO $115,000 $5055. ON 19 2w vu, On $215, ON SIMON $530, ON 08 sm'w sm'w $115,M $555, NO 2007 --- - - - - - ---------- - -- - --------- Total Funds Required $2, M, W $1,9n,M $3,456, ON s8ft, On $1, 150, ON $9,3200, ON Percent of Total Need 21.67% 20.39% 37.82% 8.58% 12.34% IN.00% 8-9 Table 8-3 SUMMARY OF STORMWATER FUNDING NEEDS ASSUMING CONTINUING 5% INFLATION (To be prepared when Table 8-2 has been finalized and reviewed by Santa Rosa Staff) 8-10 There are several alternatives that are available to cities and counties in Florida to find a stormwater management program. These include: Revenue for Annual OperationExpenses 0 General Fund 0 Drainage Utility Service Charges Fundings for Major Capital Improvements 0 General Obligation Bonds Repaid by Property Taxes 0 Revenue Bonds Repaid by Utility Service Charges 0 Utility Tax Revenues 0 Community Development Block Grant Funds .Fundings for New Development Services 0 Plan Review Fees 0 On-site System Inspection Fees 0 Impact Fees 0 System Development Charges 0 In-lieu of Construction Charges 0 Latecomer Fees Funding for Special Services 0 Local Improvement Districts 0 Utility Local Improvement Districts 0 Special-Purpose Taxing Districts Unfortunately, only the stormwater utility and bonding programs are capable of providing adequate funding to completely meet the County's long-term needs for stormwater facilities. tm:SR2/MM 8-11 3 6668 14101 3633