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t% Oto ft m -V c- p SOUTHWEST ESCAMBIA COUNTY STORMWATER MANAGEMENT PLAK/ 0 M 4r/ 4k 0 4c co u val FOR ESCAMBIA COUNTY WITH FINANCIAL ASSISTANCE FROM THE FLORIDA DEPARTMENT OF ENVIRONMENTAL REGULATION AND THE COASTAL ZONE MANAGEMENT ACT OF 1972 K: PREPARED BY BASWERVILLE BARRETT DAFFIN AND CARLAN, INC. DONOVAN AkCllJTEC-l*S ENGINEERS PLANNERN 0 ENGINEERS, WC. TABLE OF CONTENTS SECTION TITLE PAGE 1.0 INTRODUCTION PROJECT HISTORY 1-1 1.2 STUDY AREA DESCRIPTION 1-3 1.3 STUDY OBJECTIVES 1-8 1.4 SCOPE OF REPORT 1-10 2.0 INVENTORY 2-1 2.1 BASE MAP PREPARATION 2-1 .2.2 DRAINAGE STRUCTURE SURVEY 2-2 2.3 BASIN DELINEATION 2-8 2.4 TOPOGRAPHY 2-10 2.5 HYDROLOGIC DATA COLLECTION & REVIEW OF RELEVANT STUDIES 2-12 2.6 SOILS 2-18 2.7 LAND USE 2-22 2,7*1 EXISTING LAND USE, 2.7.2 FUTURE LAND USE 2-24 2.8 FLOOD MAP 2-26 3.0 PROBLEM AREA IDENTIFICATION 3-1 3.1 SOURCES OF INFORMATION 3-1 3.2 PUBLIC MEETING 3-2 3.3 PROBLEMS IDENTIFIED 3-3 TABLE OF CONTENTS SECTION TITLE PAGE 4.0 FUNDING OF STORMWATER MANAGEMENT 4-1 4.1 SPECIAL ASSESSMENT 4-1 4.2 AD VA LOREM TAX INCREASES 4-6 4.3 GRANTS 4-8 4.4 DEVELOPMENT IMPACT FEES 4-10. 4.5 STORMWATER AS A UTILITY 4-12 4.6 CONCLUSION 4-14 5.0 PROBLEM DESCRIPTIONS AND STRUCTURAL ALTERNATIVES EVALUATED 5-1 5.1 BRIDGE CREEK BASIN 5-1 5.2 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN 5-23 5.2.1 BAYOU GRANDE HEADWATERS NORTH 5-24 5.2.2 PLEASANT GROVE 5-30 5.3 GULF BEACH HIGHWAY 5-48 5.3.1 GRAND LAGOON SUBDIVISION 5-49 5*3*2 SEAGLADES AREA 5-@O - 5.3.3 QUINAVISTA AREA 5-65 5.3.4 TREASURE HILL 5-69 5.4 PERDIDO BAY RESORT AREA 5-74 5.4.1 DOUG FORD DRIVE 5-74 5.4.2 ARAPAHO DRIVE 5-80 5.4.3 ZUNI CIRCLE 5-83 5.5 PENSACOLA BEACH 5-84 5.5.1 FT. PICKENS ROAD 5-85 5.5.2 ENSENADA UNO 5-88 5.6 JONES SWAMP & GARCON SWAMP BASINS 5-94 TABLE OF CONTENTS SECTION TITLE PAGE 5.7 PARADISE BEACH 5-95 5.8 BRONSON FIELD BASIN 5-95 5.9 PERDIDO KEY/INNERARITY AREA 5-96 5.9.1 PERDIDO KEY 5-96 5.9.2 INNERARITY PENINSULA 5-98 5.10 TARKILN BAY 5-99 5.11 SANDY CREEK/WEEKLEY BAYOU BAS.IN 5-99 6.0 NON-STRUCTURAL RECOMMENDATIONS 6-1 6.1 GENERAL RECOMMENDATIONS 6-1 6.2 SPECIFIC RECOMMENDATIONS FOR SELECTED AREAS 6-9 LIST OF FIGURES FIGURE TITLE PAGE 1-1 STUDY AREA 1-5 1-2 SANTA ROSA ISLAND STUDY AREA 1-6 2-1 DRAINAGE STRUCTURE INVENTORY 2-3 2-2 MAJOR BASINS 2-27 2-3 TOPOGRAPHIC FEATURES & LOW LYING AREAS 2-28 2-4 SOILS MAP 2-29 2-5 EXISTING LAND USE 2-30 2-6 FUTURE LAND USE 2-31 2-7 FLOOD MAP 2-32 3-1 DRAINAGE PROBLEM AREAS 3-10 3-2 SANTA ROSA ISLAND PROBLEM AREAS 3-11 .5-1 DRAINAGE ALTERNATE NO. 1 BRIDGE CREEK BASIN 5-14 5-2 DRAINAGE ALTERNATE NO. 2 BRIDGE CREEK BASIN 5-15 5-3 DRAINAGE ALTERNATE NO. 1 BAYOU GRANDE HEADWATERS NORTH 5-15 5-4 DRAINAGE ALTERNATE NO. 2 BAYOU GRANDE HEADWATERS NORTH 5-36 5-5 DRAINAGE ALTERNATE NO. 1 PLEASANT GROVE 5-41 5-6 DRAINAGE ALTERNATE NO. 2 PLEASANT GROVE 5-42 5-7 GRAND LAGOON ALTERNATE NO. 1 5-56 5-8 SEAGLADES ALTERNATIVE 5-63 LIST OF FIGURES FIGURE TITLE PAGE 5-9 QUINAVISTA ALTERNATIVE 5-67 5-10 TREASURE HILLS ALTERNATIVE 5-72 5-11 DOUG FORD ALTERNATIVE 5-77 5-12 DRAINAGE ALTERNATIVE NO. 1 FT. PICKENS ROAD 5-92 5-13 DRAINAGE ALTERNATIVE NO. 2 FT. PICKENS ROAD 5-93 LIST OF TABLES TABLE TITLE PAGE 2-1 WETLANDS ANALYSIS 2-11 2-2 SOILS ANALYSIS 2-21 3-1 DRAINAGE PROBLEM AREAS 3-5 4-1 ALTERNATIVE COSTS 4-5 5-1 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 1 5-16 5-2 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 2 5-19 5-3 ALTERNATIVE EVALUATION FOR THE BRIDGE CREEK BASIN 5-22 5-4 COST ESTIMATE ALTERNATIVE NO. 1 BAYOU GRANDE HEADWATERS AND, BAYOU GRANDE BASIN 5-37 5-5 COST ESTIMATE ALTERNATIVE NO. 2 BAYOU GRANDE HEADWATERS - NORTH 5-39 5-6 ALTERNATIVE EVALUATIONS BAYOU GRANDE HEADWATERS - NORTH 5-40 5-7 COST ESTIMATE ALTERNATIVE NO. 1 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN 5-43 5-8 ALTERNATIVE EVALUATION PLEASANT GROVE 5-47 5-9 COST ESTIMATE ALTERNATIVE NO. 1 GRAND LAGOON 5-57 5-10 COST ESTIMATE ALTERNATIVE NO. 2 GRAND LAGOON 5-58 5-11 ALTERNATIVE EVALUATIONS GRANDE LAGOON SUBDIVISION 5-59 LIST OF TABLES TABLE TITLE PAGE 5-12 COST ESTIMATE - SEAGLADES AREA. 5-64 5-13 COST ESTIMATE - QUINA VISTA AREA 5-68 5-14 COST ESTIMATE - TREASURE HILL 5-73 5-15 COST ESTIMATE - DOUG FORD DRIVE 5-78 5-16 COST ESTIMATE - WEST END DOUG FORD DRIVE 5-79 5-17 COST ESTIMATE ARAPAHO DRIVE 5-82 .5-18 COST ESTIMATE ALTERNATIVE NO. 1 FT. PICKENS ROAD 5-89 5-19 COST ESTIMATE ALTERNATIVE NO. 2 FT. PICKENS ROAD 5-90 5-20 ALTERNATIVE EVALUATION FT. PICKENS ROAD 5-91 LIST OF EXHIBITS EXHIBIT TITLE PAGE 2-1 & 2-2 INFORMATION REQUIRED 2-5 2-6 BRIDGE SURVEYS 2-3 DIAGRAM SHOWING INFORMATION REQUIRED FOR BRIDGE SURVEY 2-7 3-1 DRAINAGE STUDY QUESTIONNAIRE 3-4 4-1 LETTER FROM DER 4-16 4-2 LETTER FROM DEPARTMENT OF 4-17 COMMUNITY SERVICES 5-1 5-2 PROCEDURE FOR THE EVALUATION OF STRUCTURAL ALTERNATIVES 5-2 & 5-3 6-1 CURRENT DER CRITERIA FOR WET DETENTION SYSTEMS 6-13 6-2 PLANT SPECIES SUITABLE AND SOMETIMES AVAILABLE FROM NURSERIES FOR LITTORAL ZONE PLANTINGS OF DETENTION PONDS 6-16 1.0 INTRODUCTION 1.1 PROJECT HISTORY Southwest Escambia County has a natural environment composed of coastal dunes, wetlands, bay and salt water marshes bor- dered by beautiful white sand beaches. The area is currently sparsely developed, but is already experiencing development pressures, particularly for residential com- munities. In 1972, the U. S. Congress passed the Coastal Zone Management Act, which provided funding assistance to coastal states, in order that coastal resource management plans could be developed. In 1985, the Escambia/Santa Rosa Coast Resource Management Committee adopted a Resource Management Plan for Escambia and Santa Rosa Counties. In that plan, recommendations were made that local governments adopt comprehensive stormwater management plans to address the quantity and quality of stormwater runoff in their jurisdictions. Escambia County has divided the coastal zone into study regions, the study area addressed in this report, being one of several of these regions. Honce, this study is funded in part by Escambia County along with federal funds made available under the Coastal Zone Management Act of 1972. This money was made avail able through the Florida Department of Environmental Regulations Office of Coastal Management. Escambia County contracted with Barrett Daffin and Carlan, Inc. and Baskerville-Donovan Engineers, Inc., a Joint Venture, to prepare a stormwater Master Plan for the study area. The fully executed agreement was received by the Joint Venture on June 1, 1987, and work on the project pro- ceeded shortly thereafter. On July 7, 1987, the Board of County Commissioners voted to amend the Contract to include revisions required by the office of Coastal Management of the Department of Environmental Regulation of the State of Florida. These modifications were necessary for the receipt of grant funds. The Joint Venture submitted a proposal to.the County to delete the development of a computer model for the study area and to instead develop more detailed alternatives for selected locations within the study area. This proposal was approved by the Commission on October 20, 1987. A public meeting was held on November 17, 1987 to report study findings and to solicit public input regarding 1-2 drainage problems and their solutions. Questionnaires were distributed to those citizens in attendance so that further study data could be obtained. There will be another public hearing at a regularly sche- duled meeting of the Escambia County Board of County Commissioners prior to adoption of the final report recom- mendations. 1. 2 STUDY AREA DESCRIPTION A portion of the study area is shown on Figure 1-1. The area is bounded on thenorth by U. S. 98, on the east by Fairfield Drive (S.R. 727), on the south by the Gulf of Mexico and on the west by the Alabama-Florida state line. The remainder of the study area is shown on Figure 1-2. This area includes that portion of Santa Rosa Island lying between the Gulf Islands National Seashore and Fort Pickens, known as Pensacola Beach. The study area is bounded by or includes several significant water bodies. On the east, there is Bayou Grande, on the north, Perdido Bay, on the west Tarkiln Bay and Perdido Bay and on the south, the Big Lagoon and the Gulf of Mexico. These waterbodies are rated as Class III waters as defined in Section 17.309 of the Florida Administrative Code. 1-3 There are several creeks within the study area, those being Jones Creek in thenortheast, Bridge Creek in the north central and Sandy Creek in the west central portion of the study area. Two large named swamps, Jones and Garcon, comprise parts of the study area. A small portion of Jones Swamp is located in the northeast corner and Garcon Swamp is located entirely within the south central section. Garcon Swamp's east-west dimension spans almost the entire area, while most of Jones Swamp is located east of the study area. There are numerous other low lying areas that are unnamed. In fact, north of old Gulf Beach Highway (C.R. 297) and east of Bauer Field Road (C.R. 293), over twenty (20) percent of the land area is comprised of.areas that would be classified as swamp. This large percentage is due to the great expanse of almost level terrain. With the exception of those areas imme- diately adjacent to the coastlines or bayous, the elevation range for the entire area is from around fifteen (15) f.m.s.l. to about thirty-three (33) f.m.s.l. Due to the flat terrain, rather impermeable soil formations have developed over most of the area, that support a seaso- nally high water table to within one (1) to two (2) feet of 1-4 two-, 0 14 w 0 C/2 tm ------ ----- cz: j------------- pl, P/ 8ALJFR @D. ------------- -------- --F ------------ ------- ------ t4 --------- ----- -- --- -------------- 4--------- - ------ ------ - COD -------- -- -- ------- tz L------ - ----4.......... ---- ---- ---------- ------------- tu LEGEND STUDY AREA BOUNDARY INTERCOASTAL WATERWAY .---SANTA ROSA ESCAMBIA COUNTY LINE ORASST POINT . ....... 0 141Y ,klx "'SiA, z k C OA STA t dop ft-ft SABINE POINT VILLA SASIP41 @LITTLK SABIN[ a Dr Quill PIIINSAC A BIAC 1,,BAYWATCH If the surface. This condition compounds stormwater runoff problems in the area., Major transportation.routes within the area have been placed .on fill sections ranging from two to six feet above natural grade. This allows positive drainage of the roadways and protects the pavement structure from high water tables encountered. The major routes in the area are: 1) Fairfield Drive (S R. 797) North-South route forms the eastern boundary of the study area. 2) U.S. 98 (S.R. 30). East-West route forms the western boundary of the study area. 3) Blue Angel Parkway (S R. 173) North-South route located in the eastern part of the study area. 4) Sorrento Road (S.R. 292) (Now Gulf Beach Highway) East-West route located in the central part of t1le study area. 5) Dog Track Road (C.R. 297) North-South route located in the central part of the study area. 6) Bauer Field Road (C.R. 293) Noxth-South route located in the western part of the study area. 1-7 7) Old Gulf Beach Highway (C.R. 297) East-West route that runs along coastal area south of Garcon Swamp. With the exception of Old Gulf Beach Hiqhway, all of the roadways have been@ constructed within the last ten (10), years and their construction has significantly impacted development.in the-area. On Pensacola Beach, the major roadways are the Ft. Pickens Road and Via DeLuna Drive. These roadways head west and east respectively shortly after crossing over the bridge adjoining Pensacola Beach and the peninsula at Gulf Breeze, Florida. 1.3 STUDY OBJECTIVES The primary objectives in the study were to develop alter- native stormwater management plans for the study area and evaluate each alternative based on technical, economic, A environmental, and social impacts associated with each. Based on evaluation of these alternatives, an optimum storm- water management plan is recommended for each of the twelve basins. The second objective was to evaluate funding for implemen- tation of the selected alternatives(s). The various funding sources considered were grants, special assessments, utility 1-8 charges, ad valorem taxation, and impact fees. Third, non-structural regulatory measures were investigated and recommendations made concerning future development in the area. Another objective was to develop a tool useful to Escambia County that guide s planners and engineers in making informed decisions regarding development in the area. Specifically, problem areas have been identified and observations made regarding ways to avoid the occurrence of similarproblems in the future. The final objective was to develop an implementation sche- dule for the selected alternative based on priority and funding availability. The objectives are addressed in this report at a level of detail commensurate with the limited timeframe and money appropriated to the task. Therefore, in some instances, A is recommended that more detailed studies be undertaken prior to implementation of certain elements in the plan. These recommendations are made only when implementation of the plan element.is impossible or risky with the amount of information-available. 1-9 1.4 SCOPE OF REPORT Generalized solution concepts are considered for the problem areas in each basin. Due to time constraints, these solu- tions will only be approximate solutions and-structure sizes used are based on calculations using methods suitable for approximating flows and volumes. Detailed solutions and the exact locations of drainage facilities will be determined in the design phases following the adoption of this report. It is not the intent of this report to lock-in on solutions based on factors such as parcel divisions, and solutions presented graphically do not consider the location of pro- perty lines or ownership. It is assumed that modifications to alignment will be necessary to implement some solutions and that these details will be addressed in the design and preparation of plans for these facilities. Therefore, this report will introduce various solution con- cepts and the approximate cost to implement each solution. The alternatives presented, unless otherwise stated, pro- vide a level of service for all storms up to and including a 25 year 24 hour storm. In analyzing funding sources, each source is discussed and pro and cons of each method are presented. No detailed ana- lysis is presented for every funding mechanism. Based on 1-10 approximate methods, each funding mechanism will be eva- luated as a revenue source and compared to th e capital requirements for the selected stormwater management.plan. 2.0 INVENTORY, 2.1 BA SE MAP PREPARATION Base maps for the study area were prepared utilizing U.S.G.S. quadrangle maps and aerial photographic maps. Most of the topographic information was taken from the quadrangle maps, including lakes, inlets, bayous, and streams. Some roadway information was also taken from those maps; however, this information was limited, due to the age of the aerials from which the quadrangle maps were prepared. After the base map was prepared, roadways, streets, lakes, ditches, and retention areas were added to the base through review of recent aerials. Street locations and names were taken from the latest wall maps prepared by Champion Corporation. However, after reviewing aerials flown in November of 1986, it was apparent that some of the streets shown were platted streets only and had not, as yet, been constructed. In other cases, some streets not shown had been constructed. Therefore; those recently constructed streets were added to the base map, while not yet constructed streets we re removed. In some instances, street names have changed several times in the past few years. The most recent names were used on 2-1 the maps, as indicated on the latest sources containing street names. Some verification of the information contained on the base maps by field observation was completed. However, not every street name or location was field verified. 2.2 DRAINAGE STRUCTURE SURVEY An inventory of existing drainage structures along the major transportation routes was conducted to aid in problem iden- tification and drainage basin delineation. Along these major routes, drainage structures were iden- tified and surveys conducted of the major structures along each roadway. These structures are shown on Figure 2-1. In some places, culverts are indicated, with no size shown. In these locations, culverts exist, but due to inac- cessibility their size was not determined. For instance, along Blue Angel Parkway, at the time reconnaissance was made., water stood above the tops of the culverts on both sides of the roadway, for more than half of the culverts along the parkway. This was not flowing water, but standing water. The culverts do not have a positive outlet at their constructed elevation. In any case, all of these culverts are expected to be thirty (30) inches in diameter.or less 2-2 gs 2-49' RCP VOIRIF AAR HW P-142-24' RCP SCALE: F 2OW A AL RESERV r:*2-36- RCP( BRONSON MTOU R R D I D 0 B A T el x I X CUMLY T TARN" SAY Is, CPR el BRIDGE , ( 0 3-6'XIO' /* ILATOU Box CUL lie 0 MANG RCP VVEIR 24' 2'X4, C xv ULV 2 000 24* RCP 24- 3-48' RCP 0. KEY E DRAM MMON 2 49 and possess no real significance at this time since they have no ability to transport stormwater. Major culvert and bridge locations were surveyed in detail,. including upstream, downstream, and roadway sections in accordance with the guidelines on Exhibits 2-1 thru 2-3 for bridge surv eys. These guidelines.were developed to obtain infomation useful in the hydraulic analysis of bridges in a format compatible with several co mmercial computer programs that assist in performing the analysis. In all, ten (10) culvert or bridge locations were selected for detailed survey. Analysis of these structures indicates that few,of them significantly restrict flow out of their respective basins, and that stricter controls exist at other points within the contributing basin(s). However, two structures may require future consideration, one being the bridge on old Gulf Beach Highway where it crosses Bayou Grande. The other is the 10' X 10' box culvert under Bauer Field Road at the Sandy Creek crossing. This structure is large enough, but due to water standing to half the height of the culvert, the effective area for conveying stormwater is significantly reduced. A wider structure may be required at this location at some point in the future. A new bridge on Old Gulf Beach Highway is not an immediate concern, but the bridge immediately upstream on Blue Angel Parkway has 2-4 :;D INFORMATIO] BRIDGE SURVEYS 1. Determine opening dimensions A, B, C, D (See attached sketch). 2. Determine bridge pier width - T (Attached sketch) as closely as possible determine pier shape by selecting appropriate shape from following list: Semi-circular nose & tail Twin cylinder piers with connecting diaphragm Twin cylinder piers without diaphragm Square nose & tail 3. Determine abutment side constriction lengths - LAR and LAL- 4. Determine the elevation of the bridge low chord on the upstream side of the bridge - ELLC (attached sketch). 5. Take cross sections at locations one through five as shown on the attached sketch: (1) Section one should be located approximately four times the length of the greater of the left or EXHIBIT 2-1 .right abutment constriction length as determined in Step 3 above. (2) Section two should be located at the immediate downstream face of the bridge. (3) Section three should be a roadway profile (normally centerline) if the roadway is super-elevated, shoot the high edge of the roadway. If a curb or barrier wall is adjacent to the upstream edge of the bridge, shoot the top of curb or wall elevation (ETHW) along the bridge span. Pick up roadway pro- file at each end of bridge. The roadway profile should extend each direction away from the bridge until the roadway elevation is 2 to 3 feet above the low point on the profile in the vicinity of the bridge. (4) Cross section four is located a distance upstream., from section two a distance equal to the bridge with (W, on attached sketch). (5) Cross section five should be located approximately a distance equal to the bridge opening A + B + C + D upstream of section four. (L5 on attached sketch). EXHIBIT 2-2 0-71 40 f IIILC@@- DIAGRAM SHOWING INFORMATION REQUIRED FOR BRIDGE. SURVEY significantly greater capacity to pass stormwater prior to overtopping. This could cause problems at the Old Gulf Beach Highway at some point in the future. Infrastructure renovation for old Gulf Beach Highway is an item that will be addressed in the future and bridge improvements at the Bayou Grande crossing should be considered at that time. 2.3 BASIN DELINEATION After base map preparation and drainage structure inventory, the task of determining the major basins in the study area was begun. The task was completed using aerial topographic maps with a 5' contour interval, furnished by Escambia County, and augmented by field investigation. These maps also have supplemental contours at 2.8 feet intervals. obviously, at this contour interval, and with the nearly level topography, it was difficult to determine the location of drainage A divides. The major streams and bayous were selected as the focal points for basin determination and drainage areas were determined for each of the major basins. The major basins within the area were determined to be as follows: 2-8 1) Jones Swamp 2), Bridge Creek/Herron Bayou 3) Bayou Grande Headwaters 4) Bayou Grande 5) Sandy Creek/Weekley Bayou 6) Garcon Swamp/Garcon Bayou 7) Tarkiln Bayou After these major drainage basins were determined, the remaining areas were defined based on their geographic and hydrologic relationship to each other. For instance, after delineating the area contributing runoff to Garcon Swamp, the coastal region south of Garcon Swamp Basin was lumped into one area even though there is no common focal point for the runoff from this area, as it is composed of many small basins which drain under and over Old Gulf Beach Highway (C.R. 297) to the Big Lagoon. These areas remaining after the major basins were named are as follows: 1) Coastal area south of Garcon Swamp (Old Gulf Beach Highway) 2) Bronson Field Basin 3) Paradise Beach Basin 4) Perdido Key and Innerarity Island 5) Pensacola Beach 2-9 All of these areas with the exception of Pensacola Beach, are shown on Figure 2-2. The land surface areas represented by these divisions are shown on Table 2-1, page 2-11. 2.4 TOPOGRAPHY As stated previously, the topography of the study area is represented by moderately sloping terrain in the immediate vicinity of the coast lines with a broad flat,coastal plain toward the interior. This plain is characterized by flat upland reaches which drain to low lying swamps that possess little or no positive gradient. In many areas, there is very little difference in elevation between the low areas and the surrounding areas that drain to it. Consequently, when the low areas fill up@ during storms, there is no hydraulic gradient available to drain the surrounding "upland" areas. Unless substantial fill is placed, most land surrounding these low areas will A flood. There are a number of man-made and natural lakes, but none of any size or storage capacity that would significantly impact the runoff in the basins. Between Old Gulf Beach Highway and-the Garcon Swamp Basin, there are numerous depressions and wet-weather ponds that fill up during heavy rains and flow out through natural ravines to the highway. 2-10 TABLE 2-1 WETLANDS ANALYSIS LOW-LYING OR SWAMPY % LOW-LYING BASIN NAME ARE.A, Mi. AREA, AC. AREAS, AC. OR SWAMP Bridge Creek/ 5.920 3790 896 23.6 Herron Bayou Bayou Grande 6.24 3990 615 15.4 Headwaters Bayou Grande 3.94 2522 76 3.0 Jones Swamp 1.96 1252 .387 30.9 Garcon Swamp/ 6.92 4426 1293 29.2, Garcon Bayou Sandy Creek/ 3.34 2137 237 11.1 Weekley Bayou Paradise .70 447 44 9.84 Beach Tarkiln Bayou 1.60 1021 196 19.2 Coastal Area 5.48 3509 421 12.0 South of Garcon Swamp Perdido Key & 6.88 4402 459 10.4 Innerarity Island Pensacola 5.18 3317 209 6.3 Beach Bronson 2.29 1467 115 7.8 This results in flow sheeting.over the highway in several locations during heavy rainfall. A prominent feature in the study area, due to its immense size and unusual shape is Garcon Swamp. This swamp is entirely self contained within a long narrow basin that feeds the swamp laterally along its entire length. The unu- sual characteristic is that for a swamp this size, there is not a significant basin at its head delivering surface runoff to the swamp. Lakes, streams, and swamps are shown on Figure 2-3. The approximate acreage of low lying areas within each basin is shown on Table 2-1. It is expected that the Garcon and Jones Swamp Basins would contain a considerable amount of swamp land, but also, relatively large percentages of the Bridge Creek Basin and Bayou Grande Headwaters contain swamp land. With the flat terrain and the prominence of low, wet areas, surface drainage of stormwater is difficult. 2.5 HYDROLOGIC DATA COLLECTION AND REVIEW OF RELEVANT STUDIES During the course of the study, a number of agencies were contacted regarding data they may have relevant to the study area. Unfortunately, very few historic records exist. 2-12 Out of all the agencies contacted, very little useful data was assimilated. The fo llowing agencies were contacted concerning information pertinent to the study area:. 1) U. S. Geological Survey Tallahassee, Florida 2) Escambia County Engineering, Planning and Road Operation Departments, Pensacola, Florida 3) Florida Department of Environmental Regulation Pensacola, Florida 4) Northwest Florida Water Management District Havana, Florida 5) U. S. Army C orps of Engineers Mobile District, Mobile, Alabama 6) Santa Rosa Island Authority Pensacola Beach, Florida 7) U. S. Department of the Interior U. S. Fish and Wildlife Service National Wetlands Research Center Slidell, Louisiana 8) Florida Department of Transportation Pensacola, Florida Chipley, Florida 9) City of Pensacola, Engineering Department 10) West Florida Regional Planning County Pensacola, Florida 11) U. S. Soil Conservation Service Pensacola, Florida The U.S.G.S. did not have any stream flow gages located in or in the vicinity of the study area. The closest available streamflow data was for Carpenter's Creek in the 2-13 eastern part of Pensacol a. Due to the great disparity in hydrology of the Carpenter's Creek basin compared to basins in the study area, it is unlikely that this gage can provide reliable parameters, even for a regional type analysis. However, limited streamflow data was obtained in case its use becomes necessary. An exhaustive search with other agencies revealed no sour,ce of streamflow data. The U.S.G.S. has provided groundwater data from observation wells. Although data was provided for a number of wells in the county, only two were considered applicable to the study area. The U.S.G.S. also provided a highwater survey for the coastal areas associated with Hurriane Frederick in 1979. Escambia County personnel cooperated in providing the bulk of the data collected. This included three of the studies .referenced previously, aerial topography at 1"=300' for the entire study area., as-built roadway plans for a number of ro ads in the study area and citizen complaint information" from the Road Operations Division. Also, land use maps were provided by the Planning Department. The Florida Department of Environmental Regulation has pro- vided information in the form of studies and knowledge of the study area, as well as feedback regarding drainage alternatives and their relationship to stormwater and wetland regulations. 2-14 The Northwest Florida Water Management District provided one of the studies reviewed 'concerning groundwater. The U.S. Army Corps of Engineers was contacted concerning tidal data. However, they felt better information would be available from the highwater survey provided by the U.S.G.S. The Santa Rosa Island Authority assisted by providing a guided tour of Pensacola Beach problem areas and emphasizing those areas considered critical. Wetlands and Ecosystem mapping for the study area was obtained from the U.S. Fish and Wildlife Service. The West Florida Regional Planning Council was very coopera- tive in providing maps used in the study. Finally, the U.S. Soil Conservation Service provided soils interpretive maps for Escambia County, useful in determining what types of development activities or restrictions exist in the study area due to existing soil types. The following previous study reports were reviewed that were directly or indirectly beneficial in accomplishing the objectives of this study. 1) 11master Drainage Plan Southwest Escambia County", 1981, Henningson, Durham and Richardson, Inc. 2-15 2) "Erosion Report, Problems & Solutions Escambia County, Florida", 1982, U.S. Department of Agriculture. 3) "Structural Controls Manual for Nonpoint Source Pollution", 1980, Henningson, Durham and Richardson. 4) An Assessment of Stormwater Management Programs" for the Florida Department of Environmental Regulation, 1985, Camp, Dresser & McKee 5) "Tri-State Hurricane Evacuation Study", 1986, Hazards Management Group, Inc. for U.S. Army Corps of Engineers, Mobile District 6) "Resource Management Plan, Escambia/Santa Rosa Counties", 1985, Baskerville-Donovan Enginers, Inc. for the Escambia/Santa Rosa Coast Resource Management Committee 7) "Stormwater Management Utility Report", 1986, Camp Dresser & McKee, Inc. for the City of Tallahassee, Florida 8) "Availability and Quality of Water from the Sand-and-Gravel Aquifer in Southern Santa Rosa County, Florida", 1982 NWFWMD Water Resources Special Report - 82-1 The Master Plan developed by Henningson, Durham, and Richardson, Inc. in 1981, dealt with some of the same areas as this study. Evidently, none*of the structural recommen-" dations in that study were ever implemented. Unfortunately, efforts to obtain field information utilized in that study were unsuccessful. That data would have proven to be a tre- mendous supplement to data obtained in this study. The recommendations outlined in that study were reviewed based on today's regulatory climatel and though some of the struc- 2-16 tural solutions in that report would be possible to imple- ment, others would be quite difficult. References 2-4 above were reviewed to investigate and eva- luate various methods to control stormwater runoff and ensure water quality. Some of the material in these references will be utilized later in the report in Section 6, when guidelines for new developments are presented. Reference 5 describes coastal flooding due to tidal surge associated with different category hurricanes (1-5). That report is very well done and informative. Since the flood data presented is associated with tidal surge due to wind and does not include the effects of heavy rainfall, it will not be repeated in this report. This report will address the effects of surface water runoff only. Some of the information in reference 7 will be utilized when stormwater funding sources are evaluated in Section 4. A Based on the extensive search for hydrologic data in the study area, it is apparent that a great need exists to implement a hydrologic data collection network for the area. Recording stream and rainfall, gages should be selectively placed in the area so that a historic data base can be developed. Another great need in the area is an extensive subsurface investigation and the placement of groundwater 2-17 monitoring sites.so that groundwater profiles can be deve- loped. 2.6 SOILS Soil structure significantly influences the drainage characteristics of an area, and the land lying within the study area is no exception. Although, nearly all of the soils are primarily sands or silty sands, there is signifi- cant variation in the ability of these soils to infiltrate stormwater. This variation is due primarily to the formation of the soil structure by nature. Those upland areas near the coast exhibit characteristics quite apart from soils lying within the interior of the study area. This variation is depicted graphically on Figure 2-4. Note that red shading denotes soils exhibiting good to excellent infiltration capabilities and that almost all of these soils are adjacent to coast lines. Blue shading depicts soils with very poor infiltration capabilities and is confined to low-lying swamps and marshes. These soils have a very high content count and have standing water much of the year. Toward the interior of the study area, there are vast expan- ses of soils with poor infiltration bordered by areas that have somewhat poor (yellow) infiltration capabilities. 2-18 Due to a high water table and level.terrain, many of those areas not shaded are subject to frequent flooding and are currently unsuitable for most uses. Those areas shaded yellow are also subject to frequent shallow flooding of limited duration. The primary factor contributing to the development of these low infiltration soil structures is the level terrain. These soils consist of a mixed textured sand with some orga- nic content to a depth of three to four feet. Below this, the material is chiefly composed of very fine textured sands or sandy silts that support a high water table. Consequently though the upper layers of soil are quite per- meable, there is very little available storage capacity in the soil structure to allow infiltration of stormwater. Therefore, surface inspection of these soils during dry weather can lead to erroneous conclusions regarding the -infiltration capabilities of these soils. Most of the soils along the coastal areas have very high permeability and depth to the water table is greater than six feet, in most cases. However, during periods of heavy extend rainfall, especially the area south of Garcon Swamp, the surface-runoff collects in isolated depressions and low areas, containing soils that have poor infiltration capabi- lities. These low areas fill up and overflow through 2-19 natural drainageways. This concentrated flow of water over- taxes the inadequate drainage system along Old Gulf Beach Highway, resulting in water flowing across the roadway at several locations. Therefore, here again, this is a case, where, flooding is occurring, due to the natural terrain, even though the majority of the soils in this case have good infiltration capabilities. This situation also occurs on Pensacola Beach. The soils on Pensaola Beach consist of deep deposits of coastal sand exhibiting excellent infiltration capabilities. However, for large rainfall amounts, surface runoff does occurr and this water collects in isolated low areas that quickly become saturated. In these areas water will stand for days without percolating into the ground. -Again, this will only occur with large rainfall amounts. Table 2-2 shows by drainage basin, the land areas and per- centages of the total land area in each basin, of the four@ soil infiltration capability groups depicted on Figure 2-4. The Bridge Creek/Herron Bayou Basin, for example, contains soils with very poor to somewhat poor infiltration capabili- ties over eighty-eight (88) percent of the.basin. The Bayou Grande Headwaters has very poor to somewhat poor infiltration for ninety-seven (97) percent of the soils in 2-20 TABLE 2-2 SOILS ANALYSIS Land Area Of Land Area of Land Area Land Area Soils With Good Soils With Of Soils Of Soils Basin Area To Excellent Somewhat Poor With Poor With Poor Name (Ac.) Infiltration Infiltration Infiltration Infiltration (Red) (Yellow) (No Color) (Blue) (AC.) % (AC.) % (AC-) % (AC.) % Bridge Creek/ 3789 465 12 1088 29 2158 57 78 2 Herron Bayou Grande 3994 130 3 1155 29 2606 65 103 3 Headwaters Bayou Grande 2522 403 16 680 27 815 32 623 25 Jones Swamp 1252 46 4 307 25 612 49 287 22 Bronson Field 1467 510 34 202 14 574 39 163 13 Paradise Beach 447 287 64 63 14 49 11 48 11 Garcon. Swamp/ 4426 877 20 699 16 1466 33 1384 31 Garcon Bayou Coastal Area 3509 2746 78 263 7 50 1 450 14 South of Garcon Perdido Key 4402 3814 87 141 3 32 1 415 9 Innerarity Island Sandy Creek/ 2237 611 27 700 31 825 37 101 5 Weekley Tarkiln 1021 115 11 101 10 501 49 328 30 Pensacola Beach 3317 2934 88 - - 383 12 the basin. Conversely, Perdido Key and Innerarity Island, have highly permeable soils covering eighty-seven percent of the land area. Only twenty percent of the Garcon Swamp - Garcon Bayou Basin has soils exhibiting good to excellent infiltration capabilities A definite correlation exists between the soil type in an area and the number and severity of drainage problems iden- tified. 2.7 LAND USE 2.7.1 EXISTING LAND USE Much of the study area is undeveloped at this time. As such, the opportunity exists to address many problems before they happen. Unfortunately, many of the developments that do exist are-' experiencing problems with stormwater runoff and waste water treatment and disposal. Most of the developments that do exist are residential. The greatest concentration of these residential developments is along the coastal areas. Some of the larger subdivisions are Perdido Bay, Grande Lagoon, and Seaglades. All of these 2-22 are located in the southern or western end of the study area, and are located on or near coastal water bodies. Recent trends show new residential developments along U.S. 98 and Dog Track Road toward the interior of tile study area. Commercial development is currently very light and distantly spaced. Most of these developments are single occupancy buildings such as convenience stores or repair shops. With the exception of Perdido Key, and Pensacola Beach, commer- cial strip development and shopping centers are almost non- existent. On Pensacola Beach, many of the developments are high-rise condominiums and specialty shops as would be expected for a resort community. There are also a sizeable number of single family residential areas on Pensacola Beach in close proximity to the commercial tourist developments. Many of these areas have year-round residents. It is important that new developments on the beach not impact these residential areas. Existing land uses, with the exception of Pensacola Beach, are shown on Figure 2-5. Note that two large government complexes, Sherman Field and Bronson Field are located within the study area. 2-23 Although these facilities exist in the area, they are not being considered in this study. 2.7.2. FUTURE LAND USE Escambia County is taking a major step toward managing growth in the study area by establishing zoning in southwest Escambia County. Zoning is not established for Pensacola Beach, since property on the beach is leased, not owned. The Santa Rosa Island Authority monitors development on Pensacola Beach. The effort to establish_zoning in the area will allow some control over development and enable better planning for facilities to serve the area. Figure 2- 6 is a preliminary map showing what zoning is anticipated for the area. Again, this map is subject to changes and revisions are forthcoming. Analyzing the various zoning categories present, it is apparent that a substantial portion of the study area will be zoned CN-Conservation. Under this zoning, County Commission Approval will be required for any uses other than wildlife sanctuarys, parks, or fire towers. since uses are not designated, any use is possible as long as County Commission Approval is obtained. The CN zoned areas were 2-24 established utilizing National Wetland Inventory maps pre- pared by the U.S. Department of the Interi or Fish and Wildlife Service. The CN designated areas basically follow the wetlands shown on these maps. Most of the CN designated lands lie in the Bridge Creek-Herron Bayou Basin, the Bayou Grande Headwaters, Jones Swamp, and Garcon Swamp. Noteably, these basins were deter- mined to have the greatest percentage of swamp land as indi- cated previously in Section 2.4. Most of the area not CN is designated as residential. Most of the residential areas will have light to medium density residential designations. Areas of commercial zoning are isolated and appear to coin- cide with existing commercial uses in the study area. Based on the zoning indicated, commercial development will be limited in the study area, and will have no significant A impact on stormwater runoff. Also, the areas designated for residential usage appear to be appropriately zoned. However, some of the new areas must utilize great care in managing stormwater when developed. 2-25 2.8 FLOOD MAP Figure 2.7 reflects the flood areas established by Stottler Stagg & Associates and GKY & Associates,,Inc., for the Federal Emergency Management Agency (FEMA). The figure is included herein 'to delineate the areas of expected flooding resulting from a 100-year storm event. A 100-year storm is expected to be equalled or exceeded on the average once in any 100-year period. Although the recurrence interval represents the long-term average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than one year are considered. The FEMA revised the Federal Flood Insurance Rate Map (FIRM) for Escambia County on August 19, 1987. The FIRM generally contains specific information on expected flood heights near the coastal and bay areas. The inland areas are less A detailed and usually depict only the expected flood area with no established flood heights. The FIRM was prepared for flood insurance'purposes and is used to establish minimum floor elevations for habitable buildings. It should be noted that the established flood elevations are a minimum. It is very possible to experience flood elevations in excess of the FIRM elevations due to inadequate stormwater controls. There are areas such as this that have experienced flooding which are not in a designated flood area. 2-26 LEGEND MAIN ROADS ----STUDY AREA BOUNDARY ------MAJOR BASIN BOUNDARY V BEACH saga** BR GE E B 0 N "@DGE B r57'1 HER PN BAYOU D.A. = 5.920 SO --- 4* 4f S @EK IVE B A@ I D.A. 2.06 N ------ ARKIN ------- ------ -- -------- w E 0000.11f 11 0 S 5000' ----------- PERDIDO BAY 1% womo 00 1A '000m m I I GARCON SWAMP BASIN oft D.A. 6.06 SQ. MI. _77- (10 P@ST!@cojq GO BIG -Bo W.10-01 GULF OF MEXICO LEGEND SWAMPS STREAMS FARADIS LAKES :$EACH DEPRESSIONS ISOLATED AND SWAMPS BAON Lr B MAJOR ROADWAY .. . . . . . . MAJOR BASIN BOUNDARY ui N Im 4E IWE E B Y D.A.'- 2.06 W E AR@6 7f- - - S too.... 1" 5000, - - - ................ PERDIDO BAY .............. .......... 1000 GARC ON . . .... . ........... ................ .... . T. := ................. .... Tr wool, BEAC looe@ .......... .... 1xv,00 BIG p. ........... .... Waco OF GV-y LEGEND RED-SOILS WITH GOOD TO EXCELLENT INFILTRATION CAPABILITIES YELLOW-SOILS WITH SOMEWHAT POOR INFILTRATION CAPABILITIES BLUE-SOILS WITH VERY POOR INFILTRATION CAPABILITIES (STANDING WATER) NO COLOR-SOELS WITH POOR INFILTRATION CAPABILITIES SURVEY NOT . @4, AVAILABLE N E in 95000' PERDIDO BAY Ar /0001@ or lo -BIG "ISO op GULF OF MEXICO LEGEND RES -RESIDENTIAL COM-COMMERCIAL RES IND -INDUSTRIAL AG -AGRICULMRAL INST-INSTMMONAL @O M GOV-. GOVERNMENT- BASIN BOUNDARY ----- ----- GO NNW. N w E ------ ---- ------------- j---- -- ------- S 5000' PERDIDO BAY com - --- --------------- RE ----------- com E L mi @RE GOV B\G V.@,GOOO GULF OF MEXICO LEGEND R-1 -SINGLE FAMILY 4 D. U. PER ACRE R-2 -SINGLE FAMILY 7 D. U. PER ACRE R-3 -1 & 2 FAMILY 10 D. U. PER ACRE R-4 -MULTI FAMILY 15 D. U. PER ACRE R-5 -URBAN RESIDENTIAL/OFFICE 20 D. U. PER ACRE 6 ------ ------- NEIGHBORHOOD 25 D.U. PER ACRE R-6 -COMMERCIAL TRANSITION - LIMIT TO 4000 S. F. BLDG. 00 RR -RURAL RESIDENTIAL 1 D.U. PER ACRE VMS C-1 -RETAIL COMMERCIAL ARR C-2 GENERAL COMMERCIAL - MAUS ID-1 -I.JGHT INDUSTRIAL - NON CUMULATIVE CN CONSERVATION - REQUIRES COUNTY COMMISSION APPROVAL - PERMITS WILDLIFE SANCTUARYS, PARKS, FIRETOWERS. R2 I CN A - - - - - - - - - - - - - - - - - - - - - RR RR 00 N ------- - - - - - - - - - - - - - N I R2 RR CN W E S 1" 5000' PERDIDO BAY CN CN R3 - - - - - - - - - - - - Cl ---------r Rl N I R2. IR Oo'l; G BIG Rl GULF OF mE)aco skyw SCAI F a 20OW U-S. MA AL RESERVJ TIM BRONSON FIELD R R D I D 0 T TARMUN XAT - - -- - - - --- /* NATOU looo 3.0 PROBLEM AREA IDENTIFICATION 3.1 SOURCES OF INFORMATION One of the major tasks in this study was to identify existing drainage problems.. Due to the large area involved, this was a difficult and time consuming process. To accomplish this, a number of sources were utilized. Those sources are as follows: 1) Interviews with personnel, Escambia County Engineering and Road Operations, to identify major flooding problem areas and obtain feedback con- cerning causes of flooding. 2) Field inspection of flooding occurring due to heavy rainfall of August 12-17, 1987. 3) Review floo ding complaint records from Escambia County Road Operations for the years 1960 - summer, 1987. 4) Field interviews with citizens: A number of citi- zens were contacted to discern the scope and nature of-the drainage problems experienced. 5) Interviews with personnel of the Florida Department 3-1 of Environmental Regulation to determine what areas were continuing'problems. 6) Interview and inspect drainage problem areas on Pensacola Beach with personnel of the Santa Rosa Island Authority. 7) Newspaper accounts of flooding in the study area associated with August, 1987 rainfall. 8) A public meeting was held on November 17, 1987 where citizen survey questionnaires were distri- buted and citizen input was received. 3.2 PUBLIC MEETING A questionnaire was distributed at the public meeting November 17, 1987 which addressed specifics regarding the type and frequency of flooding that had been experienced. This questionnaire is included here as Exhibit 3-1. The public meeting was held to brief the citizenship in the study area o n progress and findings of the study and to solicit public input regarding drainage problems and their solutions. Few areas, that had not already been identified, surfaced at the meeting, but valuable insight into how the citizenship viewed their problems was obtained. Many citizens felt that 3-2 an improved maintenance program for 'existing drainage faci- lities would alleviate their problems, while others felt that minor drainage improvements would significantly reduce the problems they experience. Many of the citizens felt that their drainage pr oblems 'have been compounded by roadway construction in their areas. Roadways cited have been Blue Angel Parkway (S.R. 173), Sorrento Road (S.R. 292) U.S. 98 (S.R. 30) and Old Gulf Beach Highway (C.R. 292). These complaints deserve con- sideration because of the widespread unanimity held by the citizens in the area. Due to the nature of,the area and the lack of historic data, citizen input has been the primary source for identification of drainage problems. 3.3 PROBLEMS IDENTIFIED Based on the information provided by the various sources, drainage problem areas were identified. The locations iden- tified a description of the problems(s) being experienced, and the probable causes(s) of the problems(s) are shown on Table 3-1. These locations and the type of flooding experienced are shown on Figures 3-1 and 3-2. 3-3 SOUTHWEST ESCAMBIA COUNTY DRAINAGE STUDY QUESTIONNAIRE RESPONDENT'S NAME: RESPONDENT'S PHONE: RESPONDENT'S ADDRESS: Circle approximate location of residence or business on attached map. Do not respond to this questionnaire unless you have legitimate interest(s) within the study area shown on the attached map. RETURN TO: Barrett Daffin and Carlan, Inc. ATTN: Mr. Wayne G. Newsome, P.E. f. 0. Drawer 12526 Pensacola, Florida 32573 Phone: (904) 433-5601 1. Have you ever experienced flooding in your present loca- tion? Yes No 2. What type(s) of flooding have you experienced? Check below. a) Severe yard flooding of extended duration b) Severe street flooding _ c) Flooding of business or residence 3. How many times have you experienced flooding to type(s) stated above? a) Severe yard flooding, time(s). b) Severe street flooding, _ time(s). c) Flooding of business or residence, time(s). 4. What date(s) do you recall flooding occurring? If you cannot remember exact date(s), give approximate date(s). If you have no idea, leave blank. EXHIBIT 3-1 TABLE 3-1 DRAINAGE PROBLEMS AREA Page 1 of 5 PROBLEM BASIN LOCATION DESCRIPTION PROBABLE CAUSE(S) Bridge Creek- U.S. 98 & Cessna Yard Flooding Inadequate Conveyance Herron Bayou Street Flooding Along U.S. 98 U.S. 98 & Skyhawk Yard Flooding Inadequate Conveyance Street Flooding Along & Under U.S. 98 U.S. 98 & Ferguson Flooding of Inadequate Conveyance Field Runway @ U.S. 98 U. S. 98 U. S. 98 & Aileron Street Flooding Inadequate Conveyance Yard,Flooding U. S. 98 Aileron South of Street Flooding Inadequate Movement of U. S. 98 Yard Flooding Water Through Low Area High Water Table - No Place to Drain U. S. 98 500' + Flooding of Apartments No Positive Outlet'For West of Aileron Street Flooding Stormwater Yard Flooding Dog Track Rd - East Yard Flooding Too Much Water For Side Just South of Roadside Ditch Lack of Entrance to Greyhound Channelization Upstream Race Track Yard Elevation Low Dog Track Rd - East Yard Flooding Inadequate Conveyance Side of Road 1250' Along & Under Dog Track Southeast of Tanton Road Road TABLE 3-1 DRAINAGE PROBLEMS AREA Page 2 of 5 PROBLEM BASIN LOCATION DESCRIPTION PROBABLE CAUSE(S) Bayou Grande Dog Track Road Severe Yard Flooding No Positive Outfall Headwaters East Side of Road Minimal Structural No Culvert Under Dog From 2550' + North- Flooding Track Road - Only Outlet west of Blue Angel Through 2-30" R.C.P. Parkway Culverts at Blue Angel Parkway - Which submerge During Heavy Rains Dog Track Road Severe Yard Flooding Too Much Water Being East Side - From Flooding of Barns Carried Down Dog Track Blue Angel Parkway & Utility Sheds Road - Inadequate Southeast 3250' Culvert Size Under Dog Track Road Approximately 2750' South of Blue Angel Parkway - Problem is Compounded by Under- Sized Driveway Culverts Sorrento Rd - 200' Yard Flooding Inadequate Maintenance West of Blue Angel of Roadside Ditch, Parkway Driveway Culvert & Culvert Under Roadway - Problem Has Been Addressed North Loop Road - Yard Flooding Inadequate, Undersized 400' West of Blue & Not Maintained Drain- Angel Parkway age Ditches 10360 Etheridge Drive Yard Flooding New Culvert Under Drive- 200-300' Wes@t of way Inadequate - Also South Loop Road Water Being Turned 900 - Roadside Ditch Inade- quate TABLE 3-1 DRAINAGE PROBLEMS AREA Page 3 of 5 PROBLEM BASIN LOCATION DESCRIPTION PROBABLE CAUSE(S) Bayou Grande South Loop Road - Yard Flooding Inadequate Facilities Headwaters West of Blue Angel High Water Table (continuedY Parkway West Side South Limited Structural Lower Floor of Garage Loop Road - Just Flooding - Yard Apartment Floods -,Asso- North of Etheridge Flooding ciated with Etheridge Drive Problem Discussed Above 9619 Sidney Road Severe Yard Flooding Inadequate Conveyance East of Blue Angel Garage Flooding Downstream - Inadequate North of North Loop Street Flooding Ditch Road Bayou Grande Robertson Road Yard Flooding Inadequate Drainag e Basin Water Quality System For Unpaved Road- Street Flooding way Maintenance For Roadway Washes Ditch Draining Sherman Field Needed Innerarity Unpaved County Roads Water Quality Erosion of Roadways Area Garcon Swamp Doug Ford Drive Street Flooding Inadequate Facilities/ Basin Inadequate Maintenance Arapaho Drive Street Flooding Inadequate Facilities/ Inadequate Maintenance Bauer Road North of Street Flooding Inadequate Facilities Bridge over Garcon Swamp TABLE 3-1 DRAINAGE PROBLEMS AREA Page 4 of 5 PROBLEM BASIN LOCATION DESCRIPTION PROBABLE CAUSE(S) Gulf Beach Treasure Hill Structural Flooding Inadequate Facilities Highway Street Flooding (Coastal Ai@ea South of Grand Lagoon North Structural Flooding Inadequate Facilities/ Garcon Point) Street Flooding Inadequate Maintenance Water Over Roadway Grand Lagoon South Street Flooding Inadequate Facilities Water Over Roadway Erosion of Roadway Chanteclaire Drive Structural Flooding Inadequate Facilities 30 Seaglades Private Property Inadequate Facilities Flooding Gulf Beach Highway Water Over Roadway At Inadequate Facilities Several Locations Sandy Creek Bauer Road Water Over Roadway Inadequate Facilities Basin Seratine Drive Private Property Inadequate Maintenance Flooding Bronson Field Wildwood Lakes Street Flooding Inadequat Facilities Basin Bauer Road Water Over Roadway Inadequate Facilities Pensacola Ft. Pickens i@oad Severe Street Flooding No Positive Outlet For Beach @ Baywatch Stor mwater TABLE 3-1 DRAINAGE PROBLEMS AREA Pag e 5 of 5 PROBLEM BASIN LOCATION DESCRIPTION PROBABLE CAUSE(S) Pensacola Via DeLuna Drive Structural Flooding No Positive Outlet For Beach Between Avendida 11 One Residence Yard Stormwater House is in (continued)' and Avendida 12 Flooding Low Area Between Via DeLuna Yard Flooding No Positive Outlet For and Maldonado Drive Stormwater End of Cul-De-Sac. Street Flooding No Drainage For Street Esenada Uno Yard Flooding o SCALEt P 2000' AVAL RESERVAriou BRONSON FIELD T RATOU R R D I D 0 A T SAY c 1@1 13 TAAKMN R&T lp A,S.C A, A.B.C C 4:r^ I 000 0. 110 DWE 0 LEGEND STRUCTURAL FLOODING. B STREET. FLOODING C FLOODING OfPRIVATE PROPERTY.'... ORA% SY POINT IL 4, U94 Y IS c go re c 0.4 2 t,4 SA I N I POINT A3 m VILLA SASINI LITTLI I A. cA VIATIll Ou D, Pl H SAC Co>t BIACm zBAYWAT H ---------- 4.0 FUNDING OF STORMWATER MANAGEMENT A major problem facing local governments today is finding a way to fund needed stormwater managment programs and drainage infrastructure renovations. Over the years, governments have learned that regulatory programs alone will not deal with the complex requirements of an effective stormwater management program. Those funding methods available are as follows: 1) Special assessments 2) Ad valorem tax increas es 3) Grants 4) Development impact fees 5) Stormwater as a utility All of the meth ods listed are legitimate revenue sources for stormwater management; however, each method has drawbacks" when it comes to implementation. 4.1 SPECIAL ASSESSMENT In the view of many, funding of drainage should be provided by those directly benefitting from the improvements. As will be shown, only the most minor improvements can be funded by 4-1 assessing only those who benefit directly from the improve- ment. Table 4-1 shows the total costs associated with alternatives developed in Section Five (5). The cost/acre figures shown are based on the total acreage drained by the improvements. This does not mean that all the acreage will benefit from the improvements. Some large tracts of low lying swamp land receive no drainage improvement, but do contribute runoff to the improvements. Therefore, an assessment based on total acreage drained in each area would range from $520.00 to $3,30 0.00/acre, with an average cost/acre equal to $1,500 per acre drained. The cost/acre figure from Doug Ford Drive is based on the acreage accessed by the roadway, not drainage area. At a cost/acre of $1,500.00, an owner of twenty (20) acres of undeveloped property would have to pay an assessment of $30,000.00. This is an exorbitant price to pay for property that may not even be developable. One solutio-n to this inequitable situation is to base the assessment on the number of parcels in a basin and charge every parcel the same, regardless of size. Again, this is 4-2 not equitable since owners of large-'tracts of land would not pay their fair share. Another choice would be to base the assessment on the imper- vious acreage of a parcel. In that case, if a parcel is not developed, no assessment is paid. The only problem with this solution is that probably less than twenty (20) percent of any of the larger areas is impervious. Therefore, the assessment value per acre would have to be at least five times the previous rate in order to fund the plan. If the average percentage of imperviousness is twenty percent (20), then the assessed value per impervious acre would be $7,500.00. If the average percentage of imperviousness is ten (10) percent, then the assessed value increases to $15,000.00 per impervious acre. For a typical single family home containing approximately 2700 square feet of impervious roof, parking, and drive, the one time assessment would be approximately $930.00. X This is not an unreasonable assessment for a house experiencing a drainage problem that will be solved using this money. But for those not experiencing drainage problems, or those not benefitting from the solution, it is still an exorbitant price to pay. However, if that resi- dence or business is in a basin or subbasin where problems are being experienced, then the runoff they contribute must 4-3 be dealt with by the downsteam owner'. Hence, it is not unreasonable to expect someone to pay a share of the solu- tion cost to a problem they are helping create. Even though this last assessment procedure seems to work well and would be fair to all involved, there is still a problem. Since the cost is based on acres drained, the line defining that acreage becomes an issue. For instance, in the Bridge Creek Basin there are 3790 acres lying in the study area. The acreage drained by all improvements pro- posed is only 1475 acres. In this case, people owning pro- perty on the west side of Dog Track Road would not be assessed, yet immediately across the road, those owners would be assessed because they are included in the area drained by the improvements. For this reason, it does not seem prudent to establish assessment as a means of funding stormwater improvements unless that assessment applies to everyone in a basin. A In the Bridge Creek Basin, for example, if everyone in the basin is assessed to help fund improvements, the cost/acre would drop from $2,350.00/acre to @914.00/acre- If imper- vious acreage is used in determining the required assessment rate and assuming ten (10) percent of the basin is imper- vious, then the cost/impervious acre would be $9,140.00. 4-4 TABLE 4-1 COST/ACRE COST/ACRE TOTAL TOTAL AREA DRAINED DRAINED COST COST BASIN DRAINED ALT. 1 ALT. 2 ALT. 1 ALT. 2 Bridge Creek 1475 $2,645 $2,350* $3,901,000 $3,465,000* Bayou Grande Headwaters North 730 937* 3,200 684,000* 2,330,000 South - Pleasant Grove 790 1,000* 1,781 797,000* Pensacola Beach Ft. Pickens 5 4,600* 8,800 23,000* 44,000 Ensenada Uno 3 8,000 - 24,000 - Coastal:Area South of Garcon (Old Gulf Beach Highway) Grande Lagoon 200 1,975 1,600* 395,000 320,000* Seaglades 30 1,166 - 35,000 - Quina Vista 250 520 - 130,000 - Treasure Hills 120 3,300 - 400,000 - Perdido Bay Resort Doug Ford 500 304 - 152,000 - Arapaho 73 lots 1,356 - 99,000 - Zuni Circle - - 15,000 - Selected Alternate Total $6,295,000.00 Say 6.3 million Therefore, the assessment to a typical 2,650 square foot residence would be around $556.00. Based on this analysis, it would seem advisable to establish assessment districts corresponding to the major basin deli- neations presented in this report. If this funding mechanism is considered, it is recommended in each major basin, an accurate estimate of the impervious area be obtained so that further evaluation of an assessment based on impervious area can be made. If an assessment, based on impervious area, is utilized, then accurate detemination of that area for each parcel must be made, Some of this information is available through the tax assessor's office, but updating may be required. 4.2 AD VALOREM TAX INCREASES The first step in analyzing ad valorem taxes as a funding source was to obtain sufficient tax and parcel information" to determine the study area tax base. This task was difficult and time consuming. Most of the information ws provided by Escambia County Engineering as xeroxed copies of tax rolls for those sections in the study area. Whether this information is the most recent was not known. 4-6 However, it does provide sufficient.information to get a general idea of how much tax increase in the study area would be required to fund the improvements. The total cost of stormwater improvements proposed for the study area is approximately 6.3 million dollars. If all of this money were borrowed on a fifteen year payback period at seven percent interest, the required annual income to meet the debt would be close to $900,000.00 per year. It is not known what interest rate would be available to the County, but seven (7) percent will be used here to demonstrate funding requirements. The current non-exempt tax base in the study area is approximately 245 million dollars. To fund the stormwater improvements in the study area, the tax rate must be increased from $16.00 per thousand dollars of non-exempt assessed value to $20.00 per thousand dollars of assessed value. Based on this tax rate, a typical home assessed at eighty thousand dollars with a twenty-five thousand dollar homestead exemption would experience an annual tax increase of two hundred twenty ($220.00) dollars. This would not be acceptable to many homeowners in,the area. Another problem with this funding source is insuring that 4-7 the increased revenue is earmarked for drainage improve- ments in the study area. There would probably be additional expenses required to set up an accounting system that would separate out those funds to be used for drainage improve- ments-in the study area. The advantage of this revenue source is that it will con- tinue to provide funding forever and will grow with develop- ment of the study area. The disadvantages are the inability to track the funds received from this source and the anticipated unpopularity this action would have with the taxpayers in the study area. 4.3 GRANTS During the course of this study, a number of agencies were contacted regarding grant funds that may be available to local governments to inact stormwater improvements and to upgrade the existing drainage infrastructure. The response received from almost every agency contacted was not optimistic. The fact is, there are very few funds available for funding stormwater improvements, and the State and Federal government is placing the burden of funding on local governments. Exhibits 4-1 and 4-2 are responses received from two of the 4-8 agencies contacted. Other agencies"contacted were the Florida Department of Transportation and the United States Environmental Protection Agency. West Florida Regional Planning was also contact@ed regarding any knowledge they may have of possible grant source s. The only somewhat positive response received is from the Department of Community Development in Escambia County (Exhibit 4-2). In this response, it is possible that some areas may qualify for limited funding of infrastructure improvements. The Florida Department of Transportation has small amounts of money available to counties through their maintenance Division. This money is generally intended for maintenance activities, but can be utilized to upgrade the existing infrastructure. However, funds are limited and many Coun- ties are vying for the money. Based on conversations with the F.D.O.T., the maximum money available would be two to" three hundred thousand dollars. In general, grants should not be considered a reliable pri- mary funding source. The monies simply are not there in sufficient quantity to implement a program. However, in some areas, money may be available, and can be used as a secondary funding source. 4-9 4,4 DEVELOPMENT IMP ACT FE ES To utilize impact fees on development as a primary funding source for implementation of the stormwater,management plan would probably not result in sufficient funds. The major problem with this singular funding source is that, although there is growth in the area, it may be a long time before enough new developments are started to begin to fund improvements. This means that it may take a number of years to implement solutions due to the lack of funds and the uncertainty always exists as to how much revenue can be expected. Another factor that limits this as a primary funding source is the large amount of acreage in the study area that simply cannot be developed because it is a swamp or wetland. In other words, the number of new developments are limited by the topography of the area. Consideration of impact fees on development as a secondary funding source is viable. This money could be used to augment funds obtained throQgh other sources. 4-10 Again, the primary disadvantages with this funding mechanism is the long time it would take to accrue funds and the uncertainty of when and how much revenue would be available t,-irough this source. 4-11 4.5 STORMWATER AS A UTILITY The current trend by many local governments is to approach funding of stormwater management by treating drainage as a utility, much like gas, water, or sewer is handled by municipalities. Under this funding mechanism, every user of the utility pays his fair share of the cost to operate the utility. In Exhibit 4-1, the recommendation is made to explore this option as a funding source. In fact, cities such as Tallahassee, Florida, have already implemented the utility fees to fund drainage projects.(1) This funding mechanism would need to be applied to the entire county, not just this study area. It should be accompanied by a stormwater master plan for the entire county. A In.Tallahassee, utility fee rates are based indirectly on the impervious area contributing stormwater runoff. The impervious area is used to determine the number of single- family unit equivalents to 265.9 square feet in Tallahassee and various other surveys conducted establish this value between 2600 and 2700 square feet. "Stormwater Mangement Utility Report for the City of Tallahassee", February 1986, Camp, Dresser & McKee, Inc. 4-12 The utility fee rate for a single family unit will need to be determined by further study of the number of single family units in the Escambia County versus revenue require- ments to fund stormwater management for the entire county. As a point of comparison, the most expensive alternative for the City of Tallahassee resulted in a graduated fee rate that increase over a five year period from $1.50/SFU/Month to @3.00/SFU/Month. It is anticipated that these numbers are within the range reasonably expected to fund a storm- water management program in Escambia County. The advantages of this funding source are as follows: 1) Fair and equitable contribution by each user of the utility. 2) Provides a reliable and continuous funding source. 3) Economic impact is low when compared to other A funding sources. 4) Funding is woven into a comprehensive master plan for the entire county. The disadvantages of this funding mechanism are as follows: 4-13 1) Requires development of a master plan for the entire county to determine where and when revenue will be spent. 2) County is obligated to provide the service to the user, as with other utilities. 3) Must be implemented countywide. 4) Additional study of this funding source is recom- mended prior to implementation. 4.6 CONCLUSION Based on the various funding mechanisms evaluated, the two primary sources of revenue are special assessments and stormwater as a utility. Secondary funding through grants is possible though available money will be limited. Also, secondary funding could be obtained by placing impact fees on development, b'ut revenue from this course is not likely to meet funding needs. If special assessment funding is implemented, it would reduce the impact to individual property owners, if the assessment is made against all property owners in a basin and is based on impervious area, rather than acreage. 4-14 If stormwater as a utility is implemented, it should be applied countywide and be incorporated into a countywide stormwater master plan. 4-15 STATE OF FLORIDA DEPARTMENT OF ENVIRONMENTAL REGULATION Ok BOB MARTINEZ TWIN TOWERS OFFICE BUILDING GOVERNOR 2600 BLAIR STONE ROAD TALLAHASSEE. FLORIDA 32399-2400 DALE TWACHTMANN SECRETARY E OF FLO November 19, 1987 BARIZET7- 7-- Mr. Wayne G. Newsome 1987 Barrett, Daffin and Carlan, Inc. NOV 2 01 .1 Post Office Drawer 12526 -T -2526 Pensacola, Florida 32573 Dear Mr. Newsome: This letter is in response to your letter of November 17 regarding grant funds for local government stormwater improvements. Please be advised that, at this time, there are no state or federal grant programs for such purposes. The state is considering a state revolving loan program to assist local governments and the 1987 Federal Clean Water Act does include some funding for stormwater implementation. However, the dollar amounts are small, the demands are great and implementation is down the road. In summary, local governments will need to develop local funding sources for upgrading their stormwater infrastructure. I strongly recommend the implementation of a stormwater utility in an expedient manner. A dedicated funding source such as the utility can be used for the development and implementation of a master stormwater management plan. Such a plan will be needed to meet the requirements of the 1985 Growth Management Act and Section 405 of the Clean Water Act which will require local governments to obtain NPDES stormwater permits beginning in 1989. Sincerely, Eric H. Livingston Environmental Administrator Nonpoint Source Management Section EHL/sps Protecting Florida and Your Quality of Life EX H IBIT 4- 1 BOARD OF COUNTY COMMISSIONERS ESCAMBIA COUNTY, FLORIDA 223 PALAFOX PLACE P.O. BOX 1591 PHILLIP M. (PHIL) WALTRIP PENSACOLA, FLORIDA 32597-1591 DISTRICT ONE TEL. (904) 436-5783 [SUNCOM) 682-5783 KENNETH J. KELSON DISTRICT TWO Department of Community Services WILLIE J. JUNIOR 1190 W. Leonard Street DISTRICT THREE Suite 3 MURIEL W. WAGNER Pensacola, FL 32501 DISTRICT FOUR (904)436-9342 GRADY ALBRITTON DISTRICT FIVE November 23, 1987 Mr. Wayne G. Newsome Barrett, Daffin and Carlan, Inc. P. 0. Drawer 12526 Pensacola, FL 32573-2526 Re: Stormwater Management Plan for Southwest Escambia County Dear Mr. Newsome: Per earlier phone conversations with your firm, Community Development Block Grant is the primary funding resource available to this Department for activities such as that noted above. Proects which assist low/moderate income families are generally eligible, however, the funding level is limited. As we discussed, staff is currently examining possible projects for next year which will incorporate the area being studied, however, a detailed survey will be necessary to document the low/moderate income standing of various neighborhoods within the study area prior to commitment of CDBG funds. When the Management Plan is complete, we will be glad to examine funding possibilities. Additionally, though currently unclear, other state and/or federal funding could become available in relation to the comprehensive plan and its related implementation. Should you have questions please call me at 436-9342. Sincerely, Randy Wilkerson Director Community Services RW/uh pc: Wayne Peacock Gary Bishop Pensacola Florida's First Place City EXHIBIT 4-2 5.0 PROBLEM DESCRIPTIONS AND STRUCTURAL ALTERNATIVES EVALUATED In this section, structural solutions will. be presented for the drainage problem areas identified in section 3.0. These problem areas will be provided with one or more solutions or alternatives. Alternatives are developed for each major basin in the study area, as described in Section 2.3. These alternatives for each basin are evaluated in five categorie s as outlined on Exhibits 5-1 and 5-2. The alternative obtaining the highest cumulative point total for those five categories is the preferred alternate for that ba sin. 5.1 BRIDGE CREEK BASIN The Bridge Creek-Herron Bayou basin is one of the larger basins delineated in the study area. The portion of the basin within the study area boundary totals 5.92 square miles or approximately 3790 acres. This basin is bordere(T on the north by U.S. 98 and extends to Bauer Field Road (C.R. 293) on the east and almost to Fairfield Drive on the east. The southern basin boundary adjoins the headwater for Sandy Creek and Bayou Grande. Most of the basin drains to Bridge Creek from the east side of Dog Track Road. Approximately three hundred and forty 5-1 PROCEDURE FOR THE EVALUATION OF STRUCTURAL ALTERNATIVES ECONOMIC IMPACT A. Construction Implementation Cost B. Anticipated Maintenance Cost (compute present value of maintenance based on 25 yr. design period, i = 8%) C. Evaluate cost/acre in the contributing drainage basin for which the solution will be effected. D. Assign points to each alternative, assigning the highest number to the alternative with least cost/acre. ENVIRONMENTAL EVALUATION (including water quality) 4. Alternative will have positive impact. 3. No change in environment 2. Alternative will result in temporary change in environmental quality with equal or improved con- ditions over a period of time. 1. Alternative will have adverse impact on environ- ment. LEVEL OF SERVICE PROVIDED 4. Alternative eliminates flooding for all frequen- cies up to a 25 year return interval storm. 3. Alternative eliminates flooding for more frequent events, flooding at a slightly reduced level for the less frequent storm events will still occur, however, the duration of flooding is significantly reduced. 2. Flooding level for most storms remain unchanged, however, flooding duration is reduced. 1. No change in flooding level or duration. EXHIBIT 5-1 @IV. DOWNSTREAM IMPACTS 4. Alternative will have positive downstream impacts both water quantity and quality. 3. Alternative results in no change in downstream water quantity or quality. 2. Alternative results in no adverse impact in water quantity downstream, but may adversely impact downstream water quality. 1. Alternative has adverse impacts both in water quantity and quality. *V. HUMAN ISSUES EVALUATION 1. Plan alleviates or eliminates structural flooding and damages and the human distress associated with flooding. 2. Plan alleviates distress caused by severe street flooding and the inability of people to enter and leave their home or business. 3. Plan alleviates distress and health hazards caused by extended duration yard flooding. 4. Plan does not require the relocation of residents or businesses in order to enact. 5. Plan is an attractive addition to the neigh- borhood. In order to avoid unfair weighing of the human issues category, each subcategory (1-5) under the human issues category will be assigned a value of (1-4) for each alter- native with the highest point rating indicating the highest degree of achievement in the subcategory described. The points for 'each subcategory will be totaled and divided by five (5) to obtain the relative point value for the human issues category for each alternative. EXHIBIT 5-2 acres drains north unde U.S. 98 to Herron Bayou. The remainder of the basin drains directly into Bridge Creek from the west side of Dog Track Road. This basin is sparsely developed with residential and com- merical concentration along U.S. 98 and Dog Track Road. As stated previous ly, almost,1/4 of the basin is swamp land and, with the exception of a narrow band bordering Bridge Creek, most of the land is level. Soils in the majority of the basin exhibit somewhat poor to poor infiltration charac- teristics and have a water table to within one to two feet of the ground surface much of the year. The major drainage problems occurring in the basin are along U.S. 98 and Dog Track Road, with less severe problems occurring on Aileron Drive. Those streets impacted by the flooding occurring along U.S. 98 are Cessna Drive, Skyhawk Drive and Aileron Drive. Flooding also occurs at the inter- section of Blue Angel Parkway and U.S. 98, and property on' the east side of Blue Angel Parkway experiences significant flooding. The flooding along Dog Track Road is almost exclusively con- fined to the eastern side of the roadway. A review of the aerial topographic maps along Dog Track Road indicates a significant water surface level change from one side of the 5-4 roadway to the other. This phenomenon can best be explained by analysis of the soil map, Figure 2-6. On the west side of Dog Track Road, the upland area surrounding Bridge Creek, consists of well drained soils with depth to the water table of ten feet or more. These soils are confined to a relati- vely small area, but the hydrology associated with these soils is significant since no significant flooding problems were identified in this area, even through a number of resi- dences are located there. Hence; the east side of Dog Track Road is in part experiencing more problems than the west side due to the predominant soils found there. Investigation reveals that the level of flooding occurring along Dog Track Road and U.S. 98 is primarily associated with inadequate longitudinal conveyance and undersized culverts under the roadways. This is not to imply that these roadways did not have proper drainage design. Many of the parcels adjoining the roadways are low and preventing these lots from flooding would be difficult, however, both roadways do not have the capability of adequately inter- cepting and transporting stormwater prior to significant flooding occurring. The installation of undersized side drain culverts along both roadways has compounded the problem. Problems occurring along Aileron Drive and other streets in 5-5 the area can be attributed to not having a positive outlet for stormwater. There are.swamp areas north and south of Aileron that fill up during heavy rains. Due to the minimal duration difference between the lots on Aileron and these low areas, stormwater tends to accumulate and drain off very slowly through t hese low areas that drain from east to west. There was only one location identified that experiences structural flooding. This flooding occurs to the first floors of several townhomes recently constructed off U.S. 98 approximately 500-600 feet west of Aileron Drive and U.S. 98. This flooding appears to be associated with the fact that the townhomes are constructed in a depression with no posi- tive outlet for stormwater. The units were constructed just above natural grade. There are four or five residences along Dog Track Road that experience severe yard flooding with water to within a few inches of entering their resi- dence, but to this point, no structural flooding has been identified. Two alternatives have been developed to address the worst flooding problems in the basin. One complication that deve- loped.in dealing with problem areas in the study area is the solutions developed must consider impacts outside the study 5-6 area. There are existing problems occurring on the north side of U.S. 96 and any solution to solving problems in the study area must not impact the area north of U.S. 98. Con- sideration was also given to existing development on the west side of Dog Track Road. Both alternatives developed consider and minimize downstream impacts. Alternative No. 1 for the Bridge Creek Basin is shown on Figure 5-1. This alternative takes a conveyance oriented approach to solve the problems. It involves upgrading all side drains on U.S. 98 from Blue Angel Parkway to a point 600 feet west of Aileron Drive at U.S. 98. Also, new cross drain culverts under U.S. 98 at Skyhawk Drive are proposed. Two additional culverts will be placed a lower elevation than the existing 36" R.C.P. under U.S. 98, 600 feet west of Aileron. To accommodate this increase in flow north of 98, and to insure that peak rates downstream are held at or below existing levels, a 35 ac. (11 5.7 ac-ft.) stormwater., detention/treatment facility will not only control peak rates of discharge, but will also provide pollutant removal and water quality enhancement. New culverts.are proposed under Ferguson Field to reestablish-the natural direction of water flow. Because stormwater has no positive outfall, a ditch has been constructed that takes the stormwater to U.S. 98. This com- 5-7 pounds the problems along U.S. 98. Therefore, it is recom- mended that this ditch be filled in when improvements are made west of Ferguson Field that will allow positive drainage to the west. It will still be necessary to construct a shallow swale to U.S. 98 along the east side of Ferguson Field past the subbasin divide shown on Figure 5-1. Flow conveyance improvements are proposed from the outlet of these culverts under Ferguson Field all the way west to Dog Track Road. This construction will basically follow the existing low area approximately 300 feet south of Aileron Drive. At Dog Track Road and Aileron Drive, new culverts constructed at a lower elevation than existing culverts will be required. Just east of Dog Track Road and Aileron Drive, a 10.5 acre stormwater treatment facility is proposed whi ch treats the first inch of runoff from the entire upstream contributing drainage area prior to discharging to the west side of Dog Track Road. This facility is proposed to pro- vide stormwater treatment commensurate with the level of treatment provided by the natural system. On the west side of Dog Track Road, due to easement restric- tions, it will be necessary to construct a paved ditch from Dog Track Road almost to Bridge Creek. This will make it possible to fit the ditch section in the fifty (50) foot easement and still convey the increased discharge from under Dog Track Road. The total cost to implement this alternative is estimated at 3.9 million dollars. This includes easement purchases, engineering and administrative costs, and a twenty percent contingency. The itemized cost tabulation for this alter- native is shown on Table 5-1. Alternative No. 2 for the Bridge Creek Basin is more storage oriented than Alternate No. 1 and does not involve any new construction under U.S. 98. A large channel on the south side of U.S. 98-is proposed and all side drains will be significantly enlarged. Existing cross drains under U.S. 98 will remain. These improvements are indicated on Figure 5-2. A large stormwater detention facility is proposed in Subbasin S. Positive gradient to this facilit'y will.be maintained by constructing a channel to the large private lake located near the southeast corner of the intersection of Dog Track Road and U.S. 98. The maintained level in this lake, based on inspection of aerial topographic maps is somewhere around 10.0 F.M.S.L. Constructing a wide flat channel to a point near this lake will allow the storage level fluctuation needed in the proposed detention facility, and still provide a positive gradient for the channel along U.S. 98. 5_9 It is anticipated that the proposed detention facility will not increase discharge rates to the private lake above what is existing now. Overflow discharge for the facility will be through the 2-30" culverts under U.S. 98, while normal flows will be directed west through the private,lake. Another detention facility located in subbasin No. 5 east of Ferguson Field will store and attenuate runoff for this area and direct any discharge out to U.S. 98. However, the rate of discharge from this area shall be significantly reduced. Construction along Dog Track Road is limited to a new low head pipe cross drain just south of the existing 2" x 8" box culvert. This cross drain must be turned north, just west of Dog Track Road and carried to the discharge point of the 2' x 8' box culvert located just south of the main entrance to the Greyhound racing track. This construction feature is the same for both alternates 1 and 2. It is anticipated that some regrading of existing ditches on the east side 6 ,f Dog Track Road in the vicinity of the new cross drain will be required to direct stormwater to the new culvert. Other construction common to both alternates involves the construction of a large channel n Subbasins 12 and 13 which will direct runoff to the existing triple three (3) foot by eight (8) foot box culverts under Dog Track Road.. This 5-10 channel will prevent the accumulation of large volumes of stormwater along the roadway by interception of the runoff prior to reaching roadside ditches. The cost for alternate two (2) is estimated at 3.5 million dollars and includes easement acquisition, engineering and administrative and anticipated maintenance costs. Maintenance costs were calculated by estimating annual main- tenance costs at current dollar value. The present worth of these annual costs were calculated over a twenty-five (25) year period at eight (8) percent interest. This present worth maintenance cost is included in the capital cost for each alternate. An itemized cost tabulation for this alter- nate is shown on Table 5-2. As stated at the beginning of this section, alternatives are evaluated utilizing a point system to indicate performance in five different categories. The points assigned to each A category for the two alternates considered in the Bridge Creek Basin are shown on Table 5-3. Based on this evaluation, the preferr ed alternate is the second alternative, which is the storage oriented solution. The evaluation points totals between the two alternates is so close that slight changes in estimated costs could make alternate No. 1 the preferred alternative under this eva- luation scheme. This is entirely possible since land costs constitute a considerable portion of the total cost and land. prices fluctuate dramatically depending on geographic loca- tion, the economy, etc. Land costs used in the estimates are based on current market listings for a small sample of the lots in the area and fluctuate radically with geographic location. For this reasonf it is apparent that either alternate could be selected. The recommended alternative, however, is alternate No. 2. It does not offer quite the level of service as alternate No. 1, but avoids the possibility of impacting the area north of the study area. The use of the large area adjacent to U.S. 98 to construct the detention facility may be a difficult feature to implement, and problems may occur in implementing the construction of the drainage channel toward the private lake at the southeast corner of U.S. 98 and Dog Track Road. If this situation does occur, it may still be possible to implement alternate No. 2 by expanding the detention faci- lity and relying solely on pumped discharge to another loca- tion. The storage volume required would probably be higher and no suitable pump discharge point exists nearby. Pump storage has been considered in the Bayou Grande Headwaters Basin discussed in Section 5.2. 5-12 If problems do develop in the implementation of alternate No. 2, then alternate No. 1 may be pursued. Neither alternative is expected to have any lasting impact on the environment. In fact, with the proposed stormwater treatment facilities, there should be some improvement in water quality. The proposed channels.are large enough and have such flat side slopes and longitudinal slopes that veloci ties will be very low and erosion minimal. These channels should provide a level of stormwater treatment com- parable to the natural drainageways existing. 5-13 AREA FOR STORAGE, Aw- - 3&0 Ar- DEPTH FOR STORAGE - 15 ft. STORAGE VoLL" 35 Ac. STORMWA P*OVM - 11&7 AC ft. DETENTION FACIIJ 400 L.F. 10' 81W PAV ED DI 2:1 &S. PAVED TO A DEPTH *--?OONST. 2150 LF. OF &S' AWL DEPTH OF e/W PAVED DITCH W1 ZI DITCH - 4,5' EASEMENT NOTH REOUIRM INSTALL NEW CLI LVERTS INSTALL (2) 3r R.C.P. IN ADDITION TO miN. UTECTIVE FLOw A@- M S.F.. UPGRADE E)GSTM 3e R.Cp. UK - EFFECTIVI (2) 30' R.C.P. UPGRADE OULVERTS7 nw= - PUR04ASE ONAL R /@W C H AMN 3:1 10, 9/w ON CONST. MIN. I 81W CHAN EL 30 &S. 3:1 S.S. AVG, 7H 4! 9)nTING LLAAJKE CONST. w R.C.1 . josooo illoill WAY wam to FILL E=. DITCH (2) 44r R.C.P. Di PMIOINT 10 CONST. 25' 91W DITCH IN TmcH W/3:1 S.S CONST. 10- 91WI CHANNEL AVrL DEPTH - V/30 S.& DEPTH - 4' 4 INSTALL CULVERTS UNDERR 00 ELD. UK oTEaroE AREA - 34 S.F. >: 00 MAX HW - &S 94TAL L io* . NEW CULVERT(S) AT LOWER ELEVATION MAINTAIN Joe NATURAL MIN. EWEC71VE .FLOW, AREA - 40 S.F. : STORAZE NEW S) MIN. EFFECTIVE AREA - 44 Sy'%,,,@ rx ILQ z REQUIRED 31r X W Rr-P.L MAINTAIN (7D :*A0 NATURAL STALL NEW CUL.VER T(S) AT STORAGE LOM ELEVATION EM MIN. EFFECTIVE FLOW AREA 44 @-j CONST. WET DEIE"ON TREATMENT FACILITY =5 AQFT ST. N T(S) AT WER rx r &I- MIN. FLOW -30 UPGRADE ExiST. DITCH To i(r 8/w 3:1 SA AVG. DEPTH 4! woo to to 40 CONIST. 3W 13 'IV CHANNEL. a: I S.S. m men 0,00 000 EASEMENT MOTH -- 7W as MR0 L3) Zol wx :::LEGEND T TO *00 REMAIN BASIN BOUNDARY ROADS PROPOSED DRAINAGE DrrCH INST S (2)_ JW R-Q-P. EXISTING DRAINAGE DITCH PROPOSED CULVERT maSTING CULVERT DRAINAGE FLOW ARROW B/Ir BOTTOM WM- ,H OF PROPOSE S.S. SME SL40PE OF PROPOSED D UPGRADE CULvvtlrS U.S. HWY. 98 3r M*L (2) 43X W R.C.Px- C-P. OONST. 20' 1 (2) 30- R.C.P. ;:n. 2v 9/w DITCH WA'L DITCH 3;1..&& CONST. 10` 1 (W/ - 30 M 3r R.C.P. Wo -3 M.m CONST. STORAGE TREATKENT FACIIJ *a 0 W - 75.0 AOL ft. Arl AREA - 20 4f (2) 44r R.C.P. caw. 10 13/w owmm 3:1 && AM DEPTH - 3.0 n % % J* ft. mm 100 00 40op PROPOSED WX W* kr-P.E. @ UPGRADE AND ENLARGE DOSTING ow. rx Ir Itca DITICHS TO 2W 3:1 && 10 40 400, ,144 so 'LE.GEND BASIN BOUNDARY PROPOSED DRAINAGE DITCH EXISTING DRAINAGE CULVERT 'BA BOTTOM WIDTH OF PROPOSED DITCH S.S SIDE SLOPE OF PROPOSED DITCH DRAINAGE FLOW ARROW TABLE 5-1 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 1 page 1 of 3 STORMWATER FACILITY ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL NORTH OF 98 Pond Excavation 106,480 C.Y. 4.50 .480,000.00 Berm Fill (Clay 4,550 C.Y. 6.00 27,300.00 500 Stabilization 144,000 S.F. 0.20 28,800.00 Flow Control Struct LUMP SUM 10,000.00 Paved Ditches 1-,500 S.Y. 20.00 190,000.00 Easements 36 A.C. 15,000.00 540,000.00 Subtotal $1,276,lbo-00 SUBBASIN #2 and #3 Upgrade Culverts - 42" R.C.P. 300 L.F. 66.00 20,000.00 (Blue Angel Parkway & 98) Upgrade Culverts 42" R.C.P H Cessna Dr.) 120 L.F. 66.00 8,000.00 New Culverts Under 48" R.C.P. (U.S. 98 @ Skyhawk) 160 L.F. 75.00 12,000.00 2 - 30" Culverts Under 30" R.C.P. (Ferguson Field @ U.S. 98) 500 L.F. 45.00 22,500.00 Upgrade Culverts 36" R.C.P. (Aileron & 98) 120 L.F. 50.00 6,000.00 Add Two Culverts - 36" Under 98, 500 w. Aileron 160 L.F. 50.00 8,000.00 Ditch Excav ation 10,000 C.Y. 5.00 50,000.00, TABLE 5-1 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 1 Page 2 of 3 STORMWATER FACILITY ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL Easements (20' Add- itional! R/W) 1.4 A.C. 50,000.00 70,000.00 Grassing 102,000 S.F. 0.06 6,000.00 SUBBASIN #5 Channel Excavation 13,000 C.Y. 5.00 65,000.00 4' X 8" R.C.B. @ Ferguson Field 250 L.F. 360.00 90,000.00 Grassing 137,500 S.F. 0.*06 8,000.00 Ul Subtotal 365,500.00 _j SUBBASIN #7 Ditch Excavation 3,000 C.Y. 5.00 40,000.00 New Culverts @ Rudder Lane 43" X 68" R.C.P.E. 120 L.F. 147.00 17,600.00 Grassing S.F. 0.06 4,500.00 Headwalls 2 Ea. 2,000.00 4,000.00 SUBBASIN #11 Replace Driveway 48" X 76" Culverts Private Drives 200 L.F. 178.00 35,600.00 Ditch Excavation 8,200 C.Y. 5.00 41,000.00 Pond Excavation 60,000 C.Y. 4.50 270,000.00 New Culverts @ Aileron & Dog Track Road 5' X 10' R.C.B. 110 L.F. 500.00 55,000.00 Grassing 93,100 S.F. 0.06 5,600.00 TABLE 5-1 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 1 Page 3 of 3 STORMWATER FACILITY ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL Plant Perimeter of Pond Wetland Species 28,000 S.F. 0.50 14,000.00 Paved DitcE West of Dog Track Road 5,900 S.Y. 20.00 118,000.00 Headwalls 4 Ea. 2,000.00 8,000.00 SUBBASIN #9 & #10 Purchase Natural Storage Areas 33 A.C. 8,000.00 264,000.00 38" X 60" Culvert Ln Under Dog Track & West Side of Dog Track 600 L.F. 120.00 72,000.00 co Junction Structure 1 Ea. 2,500.00 2,500.00 Headwalls I Ea. 2,000.00 2,000.00_ Subtotal 953,800.00 SUBBASIN #12 & #13 35' BW Channel Excavation 16,000 C.y. 5.00 80,000.00 Grassing 138,000 SI.F. 0.06 .8,300.00 Easements 4.0 A.C. 8,000.00 32,000-00 Subtotal. 120,300.00 MAINTENANCE (PW Over 25 Yr. Per) (All Subbasins) LUMP SUM 240,000.00 TOTAL 2.,956,000.00. + 10%- ENGINEERING & ADMINISTRATION 295,000.00 + 20% CONTINGENCIES, 650,000.00 GRAND TOTAL $3,901,000.00 TABLE 5-2 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 2 Page I of 3 ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL SUBBASIN #2 42" R.C.P. 300 L.F. $ 66.00 $19 800.00 Concrete Headwall, 2 Ea. 2,000.00 4,000.00 Subtotal $23,8ob.oo SUBBASIN #3 Channel Excavation 20,500 C.Y. 5.00 102,500.00 Qn 42" Culverts @ Cessna 120 L.F. 66.00 7,900.00 38" X 60" Culverts @ Skyhawk 120 L.F. 118.00 14,200-00 43" X 68" Culvert @ Ferguson Field 460 L.F. 147.00 67,600.bo 43" X 68" Culverts @ Algeron 120 L.F. 147.00 17,600.00 Channell Grassing 175,000 S.F. 0.06 10,500.00 Easements 2.4 A.C. 50,000.00 120,000.00 Subtotal $340,300-00 SUBBASIN #5 Pond Excavation 67,700 C.Y. 4.50 305,000-00 Grassing 609,840 S.F. 0.06 36,500-00 Outflow Control Structure 1 Ea. 5,000.00 5,000.00 Easement 14.0 A.C. 8,000.00 112,000-00 Subtotal $458,500.00 TABLE 5-2 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 2 Page 2 of 3 ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL SUBBASIN #6 & #8 Channel Excavation 19,800 C.Y. 5.00 99'.000.00 Pond Excavation 96,800 C.Y. 4.50 @435,600.00 Flow Control Structure 1 Ea. 10,000.00 10,000.00 Easements 25.5 A.C. 35,000.00 892,500-00 Subtotal $1,437,100.00 SUBBASIN #11 Ditch Excavation 3,100 C.Y. 5.00 15,500-00 Grassing 57,200 S.F. 0.06 3,400-00 Easements 1.8 A.C. 8,000.00 14,400.00- Subtotal $33,300-00 SUBBASINS #9.& #10 38" X 60" R.C.P.E. 660 L.F. 117.63 77,600-00 Junction Struct. 1 Ea. 2,500.00 2,500.00 Headwalls 2 Ea. 2,000.00 4,000.00 Grassing 13,200 S.F. 0.06 800.00 Subtotal $84,900-00 SUBBASINS #12 & #13 Ditch Excavation 13,700 C.Y. 5.00 68,500-00 Grassing 118,800 S.F. 0.06 7,100-00 Easements 3.8 A;C. 8,000.00 30,400-00- Subtotal 106,000-00, TABLE 5-2 BRIDGE CREEK BASIN COST ESTIMATE-ALTERNATE NO. 2 Page 3 of 3 ITEM QUANTITY UNITS UNIT PRICE SUB-TOTAL MAINTENANCE Lump Sum Subtotal 141,600.00 TOTAL 2,6251500.00 + 10% ENGINEERING 262,500.00 20% CONTINGENCIES 577,600.00 TOTAL $3,465,600.00 TABLE 5-3 ALTER NATIVE EVALUATION FOR THE BRIDGE CREEK BASIN Alternate Alternate No. 1 No. 2 Economic Impact 3 4 Environmental Evaluation 3 3 Level of Service Provided 4 3 Downstream Impacts 3 4 Human Issues Evaluation 3.6 3.6 TOTAL 16.6 17.6 5-22 5.2 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN The Bayou Grande Headwaters is the second largest defined basin in the study area. It comprises 6.24 square miles or 3900 acres. This basin is very similar to the Bridge Creek Basin, not only in size, but it is also hydrologically simi- lar. Like the Bridge Creek Basin, developmment is sparse and is limited to isolated'concentrations of residential development and distantly spaced singular commercial uses. In fact, this basin is more rural than the Bridge Creek Basin with the only sizable residential concentration being the Pleasant Grove community. The Bayou Grande Basin consists of that area cont ributing drainage laterally along the length of the Bayou Grande to the study basin limits. Commercial and residential develop- ment in this basin is much more intense than either Bridge Creek or the Bayou Grande Basin. This basin has a drainage area of 3.94 square miles or approximately 2500 acres. it., differs hydrologically from the headwaters in that the terrain is moderately sloped, not level. With the excep- tion of a large constructed drainage ditch draining a por- tion of Sherman Field, there are no sizable concentrations of stormwater, at least not in comparison to Bridge Creek or the Bayou Grande Headwaters. 5-23 tely for the north and south portions of the basin. Since the only identified problem in the Bayou Grande Basin is just east of Old Gulf Beach Highway in the Pleasant Grove area, alternative evaluation for this basin will be included with the Pleasant Grove evaluation in the Bayou Grande Headwaters. 5.2.1 BAYOU GRANDE HEADWATERS - NORTH The area experiencing the most drainage problems in the nor thern portion of the basin lies on the east side of Dog Track Road and extends north and south approximately 2500 3000 feet of the intersection of Dog Track Road and Blue Angel Parkway. Most of this area is low when compared to the roadway elevations and considerable acreage becomes inundated during heavy rain s. The area north of Blue Angel Parkway and east of Dog Track Road has no positive outlet due to the lack of a culvert under Dog Track Road. Although, two 30-inch culverts exist under Blue Angel Parkway, on the east side of the intersec- tion with Dog Track Road, these culverts were not designed to carry the stormwater from the northeast corner of Dog Track Road and Blue Angel Parkway. Hence, a substantial area has no drainage outlet at an elevation below flooding. The drainage area involved is somewhat difficult to deter- 5-24 mine due to the inability to evaluate the effect of the culverts under Blue Angel Parkway which have no positive outlet, with the exception of the 30 inch culverts at the intersection mentioned previously Topographic aerials indicate that three sets of culverts to the east of the intersection should direct some stormwater from Subbasin 15 north to Subbasin 16 as shown on Figure 5-3. However, the actual percentage has not been determined. In any event, it is estimated that approximately 300 acres total drainage area north and east of the intersection has no positive outlet. For this reason, when flooding does occur, the duration is on the order of five to six days, which is intolerable. On the south side of the intersection, significant yard flooding on the east side of Dog Track Road occurs. However, due to positive drainage through culverts under Dog Track Road, the flooding is of limited duration. Though several residences.experience severe yard flooding, much of the acreage inundated is cultivated range land. Three alternatives were developed to address flooding in this area. The first alternative involved improvements in the conveyance of stormwater from east to west under Dog Track Road. Also, ditches are proposed which will intercept stormwater before it gets to the roadway and direct it more 5-25 efficiently to the existing culvert'crossing locations. These improvements are shown on Figure 5-3. New culverts are proposed under Dog Track Road approximately 1250 feet northwest of its intersection with Blue Angel Parkway. Calculations indicate that an effective flow area of sixty (60) square feet would be required to safely pass the 25 year storm under the roadway. However, there are only three 36 inch culverts downstream under Blue Angel Parkway and unless these culverts are replaced, the capacity under Dog Trac k Road would be wasted. For this reason, a lower level of service at this location would appear to be an acceptable solution and three 36 inch culverts are pro- posed under Dog Track Road. On the south side of the intersection, interceptor ditches are proposed in Subbasins 15 and 17. In Subbasin-15, the existing culverts under Dog Track Road are left intapt. However, driveway culverts must be replaced, since they ac At to restrict flow. In Subbasin 17, a large ditch is proposed along the rear property lines of those parcels abutting Dog Track Road. This ditch will intercept much of the stormwater from the east and direct it perpendicular to the box culvert under Dog Track Road approximately 2600 feet south of the inter- 5-26 section with Blue Angel Parkway. At this location, it will be necessary to significantly increase the culvert size under Dog Track Road. Preliminary estimates show the need to construct two 4 foot X 8 foot box culverts in addition to the ex isting culvert of the same size. Cost estimates to make these 'improvements are shown on Table 5-4. The total cost to implement these improvements is approximately $684,000.00 or about $937.00 per acre drained. The second alternate considered for this area involves the construction of two large stormwater storage facilities, one with gravity discharge, the other with pumped discharge. The improvemments proposed as part of this alternate are shown on Figure 5-4. A twenty-one acre pumped storage area is required northeast of the intersection on the east side of Dog Track Road. The large size required is due to the large volume of runoff for the 25 year-24 hour design stor.p. Since pumping rates are small in comparison to gravity discharges, the large storage area is needed to prevent flooding of the residential lots along Dog Track Road. The pumping station proposed would consist of two 5,000 gpm pumps, along with one 5,000 gpm pump on standby. Since maintained water levels in the pump storage facility would have to be below existing groundwater levels, it would be 5-27 necessary to have a smaller 500 gpm pump to handle the constant groundwater inflow into the facility. A rather large 24" diameter force main would be required to handle the peak pump discharges. The large size was selected to reduce the total dynamic head by minimizing friction losses in the line. Also, proposed under Alternate 2 is a large stormwater detention facili ty on the east side of Dog Track Road and south of the intersection with Blue Angel Parkway. This facility will store stormwater prior to releasing it into a channel constructed perpendicular to Dog Track Road. With this controlled release of stormwater, enlarging the culverts under Dog Track Road becomes unnecessary. Cost estimates for this alternate are shown on Table 5-5. The total cost to implement this alternate is expected to be in excess of 2.3 million dollars or $3200/acre. This is a A significantly higher cost than Alternate 1. It is expected that Alternate 2, however, will provide a superior level of service, particularly for the area north of Blue Angel Parkway. The third alternate is actually a variation of Alternate 2. In this alternate, the excavated storage facility on the north side of the intersection is reduced to just a small sump area, one acre in size. Flooding in the northeast corner would still continue at a reduced level and have a much shorter duration. This is probably a good choice, since only five or six parcels are involved, and no struc- tural flooding has been identified. If the pumped discharge remains, but constructed.storage is virtually eliminated, then the total cost to implement Alternate 3 would be 1.24 million dollars or approximately $1700/ac. This cost is still 80 percent higher than Alternate 1 but only 53 percent of the cost of Alternate 2. The various alternatives for this area have been evaluated in five categories as shown in Table 5-6. Note that based.. on this evaluation, Alternate 2, the most costly alternative would be the preferred alternate. However, this is based on honest objective merits assigned to very general categories. For this reason, it is felt that th e evaluation procedures in this case, results in an erroneous choice for best selec- tion. Although economic impacts are evaluated in the proce- dure, there is no degree or scale applied to the evaluation process, other than the relative cost of an alternate. In other words, the procedure does not assign points in the economic category based on the actual cost of an alternate, but rather, its rank when compared to the other alternates 5-29 considered. Since Alternate 2 costs almost three and one- half times to implement versus Alternate 1, Alternate 1 should be selected based on economy alone. Therefore, the recommended alternative for Bayou Grande Headwaters - North, is Alternate 1. 5.2.2 PLEASANT GROVE The Pleasant Grove area is a small upland area on an extre- mely level plateau at elevation 17.5 F.M.S.L. to 19.5 F.M.S.L., surrounded on all sides by slightly lower swamps and wetlands. On the south, the South Loop Road follows an ill defined ridge separating the Bayou Grande Basin and Garcon Swamp. The plateau on the west side of Blue Angel Parkway is roughly 1500 to 2000 feet wide and slopes gra- dually toward the extreme western tip of Bayou Grande. This area has chronically experienced drainage problems through the years. However, most long time residents in the area indicate that conditions have deteriorated over the past few years. The area soils have somewhat poor to very poor infiltration capability and the water table is only a foot or two below ground level most of the year. Most problems identified have been related to severe yard flooding and minor street flooding. However, at least two 5-30 locations have experienced minor damages due to water entry into their residence. The locations that these problems have been identified is shown on Figure 3-1, in Section 3 of this report. Also identified and addressed here is street and yard flooding occurring on Robertson Road in the Bayou Grande* Basin. Two alternatives were developed for the Pleasant Grove and Robertson Road area. These alternates are based on slightly different approaches to dealing with the problems in the area. The second alternate introduces the use of underdrains and pumped storage, whereas,-the first alternate relys strictly on channelization and conveyance improve- ments. The first alternate is actually based on a master plan for the Pleasant Grove area developed by Escambia County Engineering. Since portions of this plan have been imple- mented, it is expeditious to utilize those improvements made, to the extent possible. Most of the changes proposed are related to expanded ditch sections and associated easement widths. However, two areas were identified that are still experiencing problems after 5-31 the improvements proposed in the master plan were imple- mented. The proposed improvements for Alternate 1 are shown on Figure 5-5. These improvements are numbered and annotated on the Figure... The changes proposed from the Escambia County Master Plan other than channel and easement sizes are enlarging a 24 inch R.C.P. to 30 inches under Etheridge Drive, and placing it such that it discharges do wnstream of the existing residential driveway on the north side of Etheridge. It is also recommended that the roadside ditch be paved from the discharge point of the proposed 30" culvert to the large drainage ditch which flows north from Etheridge Drive to a channel flowing west to east under the bridge on Blue Angel Parkway to Bayou.Grande- The other major change is the addition of a constructed channel north from Sidney Road to Bayou Grande (Reference Number 24, Figure 5-5). It is expected that there will be environmen- tal concerns associated with this construction, therefore a constructed treatment facility is proposed adjacent to Bayou Grande to treat runoff in accordance with F.A.C. 17-25 for the contributing drainage area. Cost estimates for Alternative 1 are shown on Table 5-7. The implementation cost for this alternate is $797,000 or approximately $1,000/acre drained. 5-32 This cost includes the construction of a roadside channel with outfall ditches and culverts on Robertson Road (Reference Numbers 35 thru 38, Figure 5-5). The roadside ditch proposed intercepts flow on the east side of Robertson Road and channelizes it to two proposed culvert locations, where outfall ditches to the Navy ditch draining Sherman Field will be constructed. The second alternate for Pleasant Grove departs from the partially implemented Escambia County Master Plan by pro- viding pumped storage areas adjacent to and north of South Loop Road on both sides of Blue Angel Parkway. Subsequent discharge from these facilities will be directed through the thirty foot F.D.O.T. easement running northeast from Blue Angel Parkway. These facilities are shown on Figure 5-6. The concept here is to reduce the area contributing drainage to the residents on North Loop Road while also lowering the water table elevation in the vicinity of the South Loop Road. To aid in this, perforated underdrains along the road right-of-way is proposed. Before this feature is imple- mented, further study of subsurface conditions is necessary. To accomplish a satisfactory evacuation of stored stormwater following a storm event, the total station pump capacity should be at least 4000 gpm. It is anticipated that desired 5-33 maintenance of water levels can be obtained by utilizing a smaller pump with capaci ty in the range of 500 - 800 gpm under the expected operating head conditions which will be less than 20 feet total dynamic head. Both pump storage facilities are about the same size with comparable pump capacities. The cost to implement Alternate 2 is estimated at 1.5 million dollars or approximately $1,781/acre drained. A comparison of the two alternates reveals that Alternate 2 is preferable in three out of the five evaluation cate- gories, hence, it achieved the hig hest point total in,the evaluation procedure. However, much of Alternate I is already in place and it is the least costly alternate. Alternate 2 comes closest to emulating natural drainage conditions that occurred prior to construction of Blue Angel Parkway and it is expected that some lowering of the water table on South Loop Road is possible. If funding is available, it is recommended that Alternate 2 be implemented, othewise, Alternate I will accomplish many of the same objectives, at a much lower cost. 5-34 4000 E)(IST (2) 24" R.C.P.. 04b 40, 000 .1olf CONST. 25' S/W DITCH loo 41, to loo MAINTAIN to NATURAL STORAGE INSTALL F.W. sm. ILQP. AW- I )EIPTH REPLACE E)OST. DRV4WAY CULVERTS W/ 4@x lcr 3-3r R.C.P BOX CULVER`rS CONST. 3w BW 011CH W/3c 1 Ss. CONST. WlDTH ID' 81U. AVQ. DEPTH -i PAVED CHANNEL EASEMENT WIDTH 'QUIRED W/2:1 S.S. 711. (l)-41r (1)4A Ir R.CjL m REMAIN ADD TWO (2) 41A Ir R.C.9L dowo as am* sawassous BAY woo -SO Ole to 10 4e Sol INS Oka= aw woo 100 -po '040 to C2 x to to REQUUtED (4) 5= GLPJA. PUMPS IN PARALLEL to 400 EXISTWO (2) W R.C.P. cam O/W MTM AT. orw (3) W q E)WnNO 4 41r Rr-P. R.C.P. =W. 2W D/W 04"WEL AT &I && AVQ DEPM f as SIX A.4 SIMMONS Saloom ma moo so small BA"Y TABLE 5-4 COST ESTIMATE ALTERNATE NO. 1 Page 1 of 2 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN BAYOU GRANDE HEADWATERS NORTH SUBBASIN #18 ITEM DESCRIPTION QUANTITY UNIT UNIT PRICE TOTAL Channel Excavation 11,500 C.Y. 5.00 58,000.00 36 In. Culverts Under Dog Track Road 180 L.F. 50.00 9,000.00 Grassing 105,000 S.F. 0.06 6,000.00 Easements - Ditch 3.13 AC. 8,000.00 25,000-00 Property Purchase Conservation 15.0 AC. 5,000.00 75,000.00 Subtotal $173,000.00 SUBBASIN #15 Channel Excavation 7,500 C.Y. 5.00 37,500.00 Paved Channel 1,960 S.Y. 20.00 .39,000.00 Replace Driveway Culverts w/41xlO' R.C.B. 60 L.F. 500.00 30,000.00 Grassing 60,000 S.F. 0.06 3,500.00 Easements 1.5 AC. 8,000.00 12,000.00 Subtotal $122,000.00 SUBBASIN #17 Channel Excavation 23,000 C.Y. 5.00 $11-5,000.00 New Culverts Under Dog Track Road 2-4'x8' R.C.B. 120 L.F. 400.00 48,000.00 TABLE 5-4 COST ESTIMATE ALTERNATE NO. 1 Page 1 of 2 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN BAYOU GRANDE HEADWATERS NORTH ITEM DESCRIPTION QUANTITY UNIT UNIT PRICE TOTAL SUBBASIN #17(continued) Grassing 199,800 S.F. 0.06 12,000.00 Easements 5.95 AC. 8,000.00 48,000.00 Subtotal $223,000.00 TOTAL (NORTH) 518,000.00 co 10% ENGINEERING & ADMINISTRATIVE 52,000.00 + 20% CONTINGENCIES 114,000.00 GRAND TOTAL (NORTH) $684,000.00 TABLE 5-5 COST ESTIMATE ALTERNATE NO. 2 BAYOU GRANDE HEADWATERS NORTH ITEM DESCRIPTION QUANTITY UNIT UNIT PRICE TOTAL SUBBASIN #16 Excavation - Pump Storage Facility 160,000 C.Y.. 4.00 760,000.00 Pumping Station 10,000 GPM 1 Ea. 250,000.00 250,000.00 24" Force Main 2,100 L.F. 35.00 74,000.00 Maintenance and Operating Cost Lump Sum 60,000.00 Channel Excavation 12,000 C.Y. 5.00 60,000.00 Grassing 200,000 S.F. 0.05 12,000.00 Easements 24 AC. 5,000.00 .120,000.00 Subtotal $1,336,000.00 SUBBASIN #17 Channel Excavation 14,000 C.Y. 5.00 70,000.00 Detention Facility Excavation 48,000 C.Y. 4.00 192,000.00 Control Structure Lump Sum 10,000.00 Grassing 150,000 S.F. 0.06 9,000.00 Sod (Detention Sides and Berm) 40,000 S.F. 0.20 8,000.00 Easements 28 AC. 5,000.00 140,000.00 Subtotal 429,000,00 TOTAL $1,765,000.00 + 10% ENGINEERING & ADMINISTRATION 177,000.00 + 20% CONTINGENCIES 388,000.00- GRAND TOTAL $2,330,000.00 TABLE 5-6 ALTERNATIVE EVALUATION BAYOU GRANDE HEADWATERS NORTH Alternate Alternate. Alternate No. 1 No. 2 No. 3 Economic Impact 4 3 Environmental Evaluation 2 3 3 Level of Service Provided 3 4 2 Downstream Impacts 2 3 3 Human Issues Evaluation 3.6 4 3.4 TOTAL 14.6 15.0 14.4 5-40 LEGEND ------- BASIN BOUNDARY N PROPOSED DRAINAGE DITCH -Ak , EXISTING ROADS vw@@lc EXISTING CULVERT s PROPOSED CULVERT B W:' BOTTOM WIDTH OF. PROPOSED DITCH 10:00, 3:1 S.,S.@'.3. TO. f SIDE SLOPE OF DITCH C.M.P., CORRUGATED METAL PIPE R.C. P.'. REINFORCED CONCRETE PIPE DRAINAGE FLOW ARROW @6 21 0 5.. 6 2 SSIDNE 6 2 2. 10 19 2 8 .8 12 .7 woo a f 3 13 6 51 an In I= am ET)IERIDGE' RD. mm. 0 +om.. 0000 16 DRAINAGE ALTERNATE PLEASANT GROVE A. PUMP STORAGE FACILITY 3' STORAGE OVER 10.0 AC. LE'GEND TOP OF STO .RAGE = 16.0 BOTTOM OF STORAGE = 13.0, ------- BASIN BOUNDARY PROPOSED DRAINAGE DITCH B. PUMP STORAGE FACILITY E)aSTING ROADS EXISTING CULVERT 30 ACRE-FT. PROPOSED CULVERT @C. STORMWATER@: PUMP -STATION B/W BOTTOM WIDTH OF PROPOSED DITCH 3: 1 S. S. 3' TO 1' SIDE SLOPE 'OF DITCH .2 2000 G.P.-M. PUMP C. M. P. CORRUGATED METAL PIPE _1720.00 G.:P.M. PUMP (STANDB.y R. C. P. REINFORCED CONCRETE PIPE 1-800 G.P.M. DRAINAGE FLOW ARROW STORMWATER TREATMENT FACIUTY 30" R.C.P CURB looo 21 5 6,. 2 SIDNEY R PA IN R 2 :)3 10 A: W EN AN 19 EXISTING. A 18 12 A /07 31 . :, * ... : ., S mom No 1 4 A L B A L Mw Mof 2 0@ A .0 ETHERIDGE R-6. 38 5 00 to I T R A @R T E AMI W@E'N' 0 R -M FACIUly 30 R_( CU@ A @PIN 38 DRAINAGE ALTERNATE* NO PLEASANT. GROVE TABLE 5-7 COST ESTIMATE ALTERNATE NO. 1 Page 1 of 4 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN SOUTH FIGURE REFERENCE ITEM UNIT NUMBER DESCRIPTION QUANTITY UNITS PRICE TOTAL 1 Channel Excavation 1,600 C.Y. 5.00 $ 81000.00 Grassing 48,000 S.F. 0.06 2,880.00 Easement 0.60 AC. 8,000.00 4,800.00 2 Ditch Paving 700 S.Y. 20.00 14,000.00 3 30" R.C.P. 100 L.F. 48.00 4,800.00 (Includes Pavement Replacement) 4 24" R.C.P. 40 L.F. 40.00 1,60-0.00 6 Channel Excavation 800 C.Y. 5.00 4,000.00 Grassing 30,000 S.F. .0.06 1,800.00 Easement 0.06 AC. 8,000.00 500.00 8 Channel Excavation 1,900 C.Y. 5.00 9,500.00 Grassing 35,000 S.F. 0.06 2,000.00 Easement 0.96 AC. 8,000.00 8,000.00 9 Channel Excavation 5,000 C-Y. 5.00 25,000.00 Grassing 75,000 S.F. 0.06 450.00 Easement 2.0 AC. 8,000.00 16,000.00 10 Channel Excavation 1,900 C.Y. 5.00 9,500.00 Grassing 22,880 S.F. 0.06 11,400.00 Easement 0.70 AC. 8,000.00 5,600.00 TABLE 5-7 COST ESTIMATE ALTERNATE No. 1 Page 2 of 4 @BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN SOUTH FIGURE REFERENCE ITEM UNIT NUMBER DESCRIPTION QUANTITY UNITS PRICE TOTAL 11 Channel Excavation 2,000 C.Y. 5.00 10,000.00 Grassing 20,000 S.F. 0.06 1,200.00 Easement 0.60 AC. 8,000.00 4,800.00 12 Channel Exc avation 2,900 C.Y. 5.00 14,500.00 Ln Grassing 30,600 S.F. 0.06 1,800.00 Easement 0.8 AC. 8,000.00 6,400.00 14 Channel Excavation 4,200 C.Y. 5.00 21,000.00 Grassing 46,000 S.F. 0.06 3,000.00 Easement 1.24 AC. 8,000.00 10,000.00 16 24" R.C.P. 40 L.F. 40.00 1,600.00 17 Channel Excavation 3,700 C.Y. 5.00 18,500.00 Clearing 0.9 AC. 2,000.00 1,800.00 Grassing 37,500 S.F. 0.06 2,250.00 Easement 0.9 AC. 5,000.00 4,500.00 20 36" R.C.P. 80 L.F. 50.00 4,000.00 21 Channel Excavation 5,000 C.Y. 5.00 25,000.00 Grassing 49,000 S.F. 0.06 3,000.00 Easement 0.96 AC. 8,000.00 8,000.00 22 Channel Excavation 2,500 C.Y. 5.00 12,500.00 Grassing 47,000 S.F,. 0.06 2,800.00 Easement 0.50 AC. 8,000.00 4,000.00 TABLE 5-7 COST ESTIMATE ALTERNATE NO. 1 Page 3 of 4 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN SOUTH FIGURE REFERENCE ITEM UNIT. NUMBER DESCRIPTION QUANTITY UNITS PRICE TOTAL 23 Pond Excavation 13,000 C.Y. 5.00 Landscaping Lump Sum 15,000.00 Easement 2.1 AC.. 20,000.00 42,000.00 24 Channel Excavation 3,300 C.Y. 5.00 16,500.00 Easement 0.96 AC 20,000.00 19,000.00 S.F. Grassing 42,000 0.06 2,500.00 26 36" R.C.P. 60 L.F. 50,00 3,000.00 27 24" R.C.P. 40 L.F. 40.00 1,600.00 28 & 29 Channel Excavation 1,900 C.Y. 5.00 9,500.00 Grassing 25,000 S.F. 1,500.00 Easement 0.60 AC. 8,000.00 5,000.00 30 Channel Excavation 2,000 C.Y. 5.00 10,000.00 Grassing 32,000 S.F. 0.06 1,900.00 31 Channel Excavation 4,300 C.Y. 5.00 7,000.00 Grassing 87,000 S.F. 0.06 5,000.00 Easements 2.2 AC. 8,000.00 18,000.00 33 18" R.C.P.@ 40 L.F. 30.00 1,200.00 35 Channel Grading 1,600 C.Y. 4.00 6,400.00 36 Purchase Additional R/W 0.32 AC. 8,000.00 3,000.00 TABLE 5-7 COST ESTIMATE ALTERNATE NO. 1 Page 4 of 4 BAYOU GRANDE HEADWATERS AND BAYOU GRANDE BASIN SOUTH FIGURE REFERENCE ITEM UNIT NUMBER DESCRIPTION QUANTITY UNITS PRICE TOTAL 37 24" R..C.P. 100 L.F. 40.00 4,000.00 38 Channel Excavation 1,000 C.Y. 5.00 5,000.00 Grassing 20,000 S.F. 0.06 1,200.00 Easements 0.5 AC. 8,000.00 4,000.00 Ln Maintenance Lump Sum 72,000.00 TOTAL 604,000.00 + 10% ENGINEERING & ADMINISTRATION 60,000.00 + 20% CONTINGENCIES 133,000-00 GRAND TOTAL $797,000.00 TABLE 5-8 ALTERNATIVE EVALUATION PLEASANT GROVE BAYOU GRANDE HEADWATERS - SOUTH Alternative Alternative One Two Economic Impact 4 1 Environmental Evaluation 2 4 Level of Service Provided 3 3 Downstream Impacts 3 4 Human Issues Evaluation 3.2 3.4 TOTAL 15.2 15.4 5-47 5.3 GULF BEACH HIGHWAY The area along Gulf,Beach Highway consists, for the most part, of fairly high ground with elevations ranging between 13 feet and 28 feet on the north side of the highway. This area is separated from Garcon Swamp basin by an ill-defined ridge line located between 600 feet and 2500 feet north of Gulf Beach Highway. The land slopes in a general southerly direction and there are several depressions which retain stormwater. Some of the depressions contain standing water for long periods of time and are mostly in undeveloped areas north of Gulf Beach Highway. There are many other depressions which pond water for fairly short periods of time and have caused varying degrees of flooding on private property. Since the soils are sandy and relativ ely permeable, the runoff from most moderate storms infiltrates the soil and percolates down to the water table. However, there has been some severe street flooding and some structural flooding caused by heavy storms after an extended rainy period. most of the problems have occured on the north side of Gulf Beach Highway. It seems that drainage across Gulf Beach Highway is not adequate to control the runoff which reaches the highway. Water has flowed over the highway on several occasions near most of the existing culvert crossings. 5-48 5.3.1 GRAND LAGOON SUBDIVISION The Grand Lagoon subdivision is located on Big Lagoon. it lies to the east of Big Lagoon,State Park and extends north across Gulf Beach Highway. This subdivision has experienced some street flooding and structural flooding in the past. The structural flooding has occured north of the highway and is a result of inadequate drainage capacity. There are several 24-inch culverts which drain south across Gulf Beach Highway. The culvert located near the western end of the subdivision (600 feet west of Ponte Verde Drive) drains into Big Lagoon,State Park. This culvert drains approximately 25 acres of the subdivision and it appears that there has been no maintenance of the downstream ditch in recent years. There is actually no place for the water to go once it flows past the culvert. A possible reason for the lack of maintenance may be the absence of a drainage easement through the State Park. Immediate measures should be taken by Escambia County to obtain an adequate drainage easement and construct an adequate stormwater outfall to provide some temporary relief. Even with proper maintenance of the outfall, the culvert appears to be undersized. The culvert is fairly high with very little cover. This causes water to back up onto private property before it can flow through the culvert. There has been some structural flooding near this culvert and water has crossed over Gulf Beach Highway. 5-49 The second culve-rt crossing in Grand Lagoon subdivision is located about-300 feet west of Grand Lagoon Boulevard. This location is approximately 1800 feet east of the previously mentioned crossing. There are two 24-inch culverts about 200 feet apart at this location. Stormwater flows through the culvert located closest to Grand Lagoon Boulevard and discharges into a grassed swale located 350 feet south of Gulf Beach Highway. The swale then carries the stormwater about 900 feet to another 24-inch pipe which carries the flow into the lake system of the subdivision. The flow from the second culvert on Gulf Beach Highway runs east along the south side of the highway and into a catch basin where it combines with the flow from,the first culvert. The combined area drained by these two culverts is approximately 25 acres. The drainage problems associated with these culverts are similar to the problems located to the west. There has been substantial, street and yard flooding north of the highway and at least one residence has been flooded. Again, it seems that the culvert capacity is not adequate to control the runoff. The third culvert crossing near Grand Lagoon subdivision is located 1200 feet east of Grand Lagoon Boulevard. There are two 24-inch culverts at this locatio n which drain approximately 50 acres of mostly undeveloped land north of the highway. The runoff flows south through the culverts and into a ditch which carries the water about 200 feet to a 5-50 30-inch pipe. This pipe.then carries the flow about 450 feet to the south where it discharges into Big Lagoon. Since t'here is litt le development north of Gulf Beach Highway at this location, there are no serious stormwater problems north of the road. However, it is suspected that water does cross over the highway. There is also a problem with structural flooding of a residence located on Chanticleer Drive south of Gulf Beach Highway. The 30-inch storm pipe runs under an auxiliary building on residential property which has experienced frequent and severe flooding. There are other stormwater problems located south of Gulf Beach Highway. The Grand Lagoon area has experienced significant street flooding. Water has crossed over Ponte Verde Drive at two culvert crossings which are part of the subdivision's internal lake system. The flow of water over the road was severe enough to actually wash out the roadway at the culvert crossing nearest to Grand Lagoon Boulevard.., The problems south of Gulf Beach Highway are compounded by the runoff coming from the north. Any measures taken to relieve the flooding north of Gulf Beach Highway should be designed to route the stormwater around the lake system in order to reduce the stormwater problems located south of the highway- 5-51 Drainage Alternatives Alternative I Alternative "I" consists of the installation of a stormwater collection system along the north side of Gulf Beach Highway and discnarge to a Boat Basin which is connected by a dredged canal to Big Lagoon. This alternative includes stormwater piping sufficient to carry the runoff generated by a 25-year design storm. Approximately 3000 feet of pipe would be required along the north side of the highway and approximately 800 feet of pipe would be necessary to connect the system to the Boat Basin. most of the improvements can be placed within the right of way of Gulf Beach Highway and Grand Lagoon Boulevard. An easement will be required from Grand Lagoon Boulevard to the Boat Basin. A The approximate construction cost for Alternative "I" is estimated to be $395,000. This results in a cost of $3,950 per acre for the drainage area located north of Gulf Beach Highway. When the area of the subdivision located south of the highway (which will also benefit) is figured in the cost per acre drops to $1,975. A large portion of the area is developed and consists mostly of one-third acre single-family lots. If the area was totally developed with single-family homes, the cost per residence would be approximately $987. 5-52 Direct stormwater discharge to surface waters can have a significant impact on water quality. Many surface pollutants such as silt, heavy metals and fertilizers are transported by stormwater during the first one-half inch of rainfall. However, in this case, the impact will be less severe since the area's sandy soils will absorb the first one-ha lf inch of rainfall from a normal storm. Runoff from the area only occurs during storms after a relatively wet p eriod when the water table is near the ground surface. Therefore, the pollution content of the runoff has already been reduced by recent rains which carried the pollutants into the soil. For these reasons the environmental impact of Alternate I is estimated to be slight. Alternative II Alternative "II" consists of the same general routing as Alternative "I" but, instead of sizing the piping to handle the peak runoff, Alternative "II" will utilize perforated pipe to control the watertable. By controlling the watertable, a significant amount of storage volume is made available within the soil above the watertable. This can significantly reduce the peak rate of r unoff and as a result the piping size can be reduced. The basic difference between this alternative and Alternative "I" is that the piping is perforated and wrapped with a 5-53 filter fabric to-keep the soil from@entering the pipe. The piping would also be placed deeper in the ground to obtain the greatest amount of storage in the soil above the pipe. AS in Alternative "I", stormwater inlets will be installed to collect the runoff which will occur during severe storms and provide access for inspection and maintenance of the piping The Escambia County Soil Survey indicates that the existing soil consists mostly of the Leon Series. This type of soil is very permeable and its characteristics are suitable for the use of underdrains. However, the design of an underdrain system requires specific soils information and it is difficult to estimate the piping size requi,red and the performance of the system without adequate soil testing. Hence, the construction cost of this alternative is difficult to estimate. For the purpose of this report we have assumed that each pipe size, estimated in Alternative "I", can be reduced between six to twelve inches. This will result in a total construction cost of approximately $320,000 which iv a $75,000 savings over Alternative "I". The resulting cost per acre is $1,600 and the cost per lot is $800. Since the "first-flush" of runoff will be absorbed by the dewatered soil, to some degree, the environmental impact of this alternative will be less than Alternative "I". 5-54 Alternative Selection AS shown in the Alternative Evaluation Table Alternative "II" received the highest rating. This is due to its lower cost, slight environmental impact, the ability to control flooding and provisions for future extension. Alternative "I" has a rating below Alternative "Il" due to its higher cost, environmental impact and its inability to be extended. 5-55 TRE* ASURE HILL GRAND LA( _j ld LL) '14 Cl OUI"TIN LONGWOOD DR C3 7- > 0 -i ui co cr BEC TROA RD > LL Lil :3 I (D > cr -i 4 rr w co .4 0: Ln w 0 a,, Ln J .4 C:) X _7= CL I _j 0 le > in i5 cr- V) _j cr V) (D W M a) z p L) > 0 0 C.2 cr D r ui CD o\jf- z :3 V) NEW CULVERTS 7 cr PoNrc NEW GRASSED SWALE--/ NEW PIPING SYSTEM v Ld NEW DETENTION POND '@-,-NEW'STORMWATER C7- c OUTFALL w BIG LAGOON-'- STATE PARK Z a Q- V L ' C"o qR @0>. IBCCTFR @V, TABLE 5-9 COST ESTIMATE ALTERNATE I GRAND LAGOON SUBDIVISION Unit Item Description Quantity Unit Price Total 36" RCP 1,500 L.F. $48.00 $72,000 4211 RCP 1,100 L.F. $60.00 *66,000 48" RCP 450 L.F. $77.00 $34,650 54" RCP 800 L.F. $92.00 $731600 Drainage Structures 12 EA $1,500 $18,000 Road Crossings 2 EA $12,000 $24,000 Driveway Replacement 480 S.Y. $20.00 $ 9,600 Sod 8,000 S.Y. $ 2.50 $20,000 Easement Lump Sum $10,000 Subtotal $327,850 20% Contingency $65,570 TOTAL $393,420 SAY $395,000 5-57 TABLE 5-10 COST ESTIMATE ALTERNATIVE II GRAND LAGOON SUBDIVISION Unit Item Description Quantity Unit Price Total 24" RCP 1,500 L.F. $29.00 $43,500 36" RCP L.F. $50.00 $77,500 48" RCP .800 L.F. $79.00 $63,200 Drainage Structures 12 EA $1,500 $18,000 Road Crossings 2 EA $12,000 $24,000 Driveway Replacement 480 S.Y. $20.00 $ 9,600 Sod 8,000 S.Y. $ 2.50 $20,000 Easement Lump Sum $10,000 Subtotal $265,800 20% Contingency $53,160 TOTAL $318,960 SAY $320,000 5-58 TABLE 5-11 ALTERNATIVE EVALUATION GRAND LAGOON SUBDIVISION Alternative I Alternative II Economic 3 4 Environmental Impact 2 3 Level of Service 4 4 Human Issues 4 5 TOTAL 13 16 5-59 5.3.2 SEAGLADES AREA The terrain in parts of Seaglades subdivision consist of the highest land in the stu dy area with elevations ranging up to 45 feet above sea level. The highest ground is located south of Gulf Beach Highway in the central portion of the subdivision. The area north of the highway slopes from an elevation of approximately 28 feet in the northwest section to the southeast where the elevation of Gulf Beach Highway is about 15 feet. Except for some residences along the highway, the northern area is undeveloped. It appears that a subdivision was planned for this area since there is a network of cleared rights of way. However, the area is not well drained, there is standing water in many of the rights of way and no development has taken place. The drainage area totals over 100 acres and the runoff crosses Gulf Beach Highway through a 48-inch culvert which discharges into a private pond located about 300 feet south of Gulf Beach Highway. The 48-inch culvert seems adequate to handle thd stormwater runoff'from the area. The culvert is also low enough to drain the undeveloped area. A collection system could be extended fromthe 48-inch culvert to facilitate adequate stormwater controls. Assuming that the unimproved rights of way have not been dedicated to the County, it would be the developer's, or property owner's responsibility to construct an adequate stormwater collection and treatment system. 5-60 The runoff south,of Gulf Beach Highway is routed through several private ponds and eventually discharges into Big Lagoon. There is also additional runoff from a large area east of Seaglades which flows over Gulf Beach Highway and enters the lake system. Some flooding south of Gulf Beach Highway has been occurring due to the great amount of discharge to the lake system. The connecting drainageways between the lakes are also inadequate to control the runoff. One solution could be to construct an overflow swale from one of the upstream ponds. This would require a swale approximately 400 feet in length and it would discharge to Big Lagoon. The environmental impact of a relief swale should be slight since the runoff is from undeveloped areas and erosion of downstream drainageways will be reduced. In order to c*ontrol the runoff which presently crosses Gulf Beach Highway, the existing 18-inch pipe and its discharge to the lake system should be upgraded. A grassed swale approximately 500 feet in length will be needed. A The total construction cost for the improvements is estimated to be $35,000. This cost does not include easement acquisition since it is assumed the property owners will grant easements in exchange for the drainage benefits they receive. Based on a total of 30 acres located south of Gulf Beach Highway that would benefit from the improvements, the cost pe-r acre is $1,166. 5-61 There is also one depressed area on the south side of Gulf Beach Highway west of Flamingo Street that does not drain properly. The area holds water for long periods after extended heavy rains., The owner of the residence who is most affected, has found it necessary to pump standing water out of his yard after heavy rain. A solution to the problem would require approximately 700 feet of pipe in order to drain the water to Big Lagoon. There is no structural flooding and it would be possible to install a relatively small pipe. This pipe would not be designed to carry the peak flow, but it would drain the area and greatly reduce the duration of the yard flooding. The estimated cost for this construction including easements through the adjacent property is $35,000. 5-62 SEAGLADES cr c EXISTING 481 RCP uj -1 Y. EXISTING DEPRESSION GULF BF-ACvj Hw Ln ?I C.R. 29 N 'W CULVERT I (D m W fn 1 0 00 FLAMINGO ST NEW PIPING NEW GRASSED LA GOO TABLE 5-12 COST ESTIMATE SEAGLADES AREA AREA 1 Unit Item Description Quantity Unit Price Total 101, PVC 700 L.F. $ 9.00 $ 6,300 Structures 4 EA $1,400 $ 5,600 Sod 700 S.Y. $ 2.50 $ 1,750 Easements Lump Sum $15,000 Subtotal $28,650 20% Contingency $ 5,730 TOTAL $35,380 SAY $35,000 AREA 2 Unit Item Description Quantity Unit Price Total 48" RCP 48 L.F. $78.0.0 $ 3,744 Headwalls 2 EA $1,500 $ 3,000 Swales (Grading) 4,500 C.Y. $ 5.00 $22,500 Grassing 5,000 S.Y. .$ 0.-30 $ 1,500 Subtotal $30,744 20% Contingency $ 6,148 TOTAL $36,892 SAY $37,000 5-64 5.3.3 QUINAVISTA AREA most of the development in the Quinavista area is located along-Gulf Beach Highway with scattered development extending as much as 1200 feet north of the Highway. There is also several hundred acres of undeveloped land located between Gulf Beach Highway and Garcon Swamp. This land is fairly high with elevations averaging about 25 feet. The land slopes gradually to the south toward Gulf Beach Highway and there are several depressions which contain standing water during wet periods. Runoff from the area is usually not a problem since the sandy soils absorb much of the rainfall. The stormwater problems occur (as in other areas along Gulf Beach Highway) during heavy rains after an extended wet period. At present there is not a well defined stormwater collection system. Some land owners are taking measures to divert the runoff around their property which causes problems for adjacent properties. The stormwater facilities along Gulf Beach Highway are also inadequate. The existing A culverts are undersized and water flows over the Highway during severe rains. There are two existing culvert crossings on Gulf Beach Highway in the Quinavista area that should be upgraded. One is located at Casa Maria Lane and the other is about 850 feet to the west. Each culvert drains over 100 acres and a stormwater collection system is needed to transport the runoff through the developed areas. A simple grassed channel 5-65 would be sufficient and should be constructed to run directly north past the existing development and then turn in a general east-west direction. The east-west channel would serve to collect the runoff which sheet flows to the south. Several drainage easements would be required through private property for construction and maintenance purposes. Once the runoff is collected and routed past Gulf Beach Highway a concrete lined channel should be constructed to Big Lagoon. The terrain south of Gulf Beach Highway drops quickly and the resulting steep channel slope would create a water velocity which could easily erode an unprotected channel. Since the recommended system will inter-cept runoff from wooded areas without creating new discharge points, the system should have little impact on the environment. The improvements may actually benefit the environment by controlling the runoff across the developed areas thereby reducing erosion of unpaved roads and rights of way in the area. The construction cost including easement acquisition is estimated to be approximately $130,000. Since the improvements will serve approximately 250 acres, the resulting cost per acre is $520. 5-66 6-S ajnBTa LA rn cl fA (A CASA MARIA LN C*j rn A 0 rn 'po z 0 BERTHA ST TABLE 5-13, COST ESTIMATE QUINAVISTA AREA Unit Item Description Quantity Unit Price Total 48" RCP 148 L.F. $80.00 $11,840 Headwalls 4 EA $1,500 $ 6,000 Concrete Ditch 1,500 S.Y. $18.00 .$27,000 Swales (Grading) 6,000 C.Y. $ 5.00 $30,000 Structures 2 EA $2,000 $ 4,000 Grassing 16,000 S.Y. $ 0.30 $ 4,800 Easements 2.5 Acre $10,000 $25,000 Subtotal $108,640 20% Contingency $21,728 TOTAL $130,368 SAY $130,000 5-68 5.3.4 TREASURE HILL The Treasure Hill area consists of over 100 acres of developed land.' most of the area is relatively flat and slopes south toward Gulf Beach Highway. There is no well defined drainage system w ithin the subdivision. Most of the roads are not paved and in some cases the roads have been built up with red clay to a point that thenatural overland stormwater flow is blocked. There are also some naturally depressed areas. one such area is located 200 feet to 300 feet north of Gulf Beach Highway. This ar ea is fairly long and runs parallel to Gulf Beach Highway between Statler Avenue and PleateaU Road. Another low area is located at the southeast corner of Cambria Drive and Beckstrom Road. The area along the north side of Gulf Beach Highway near Cambria Drive is also low. All of these areas contain standing water for long periods after heavy rains. Since there are no drainage culverts across Gulf Beach Highway, the runoff is forced over the roadway near Cambria Drive. At least one business and several residences are severely affected by flood waters. There are also many graded roads which become impassable due to standing water. A solution to the problem requires construction of some type of stormwater collection system. many of the low areas can be drained by placing culverts under the roads within the 5-69 subdivision and grading swales between existing lots. An underground piping system may also be necessary. Based on the limitedinformation presently available, it appears the piping system should begin on Arrowhead Road and run west to Medina Road. Since the piping will run perpendicular to the existi ng roads, many drainage easements across private property will be needed. A total of 1,800 feet of pipe will be required to reach Medina Road and stormwater inlets should be placed on each of the four roads that will be crossed. Grass swales will also be needed to collect the stormwater in areas west of Medina Road and north on Cambria Street. Since the collected runoff will contain pollutants from the developed area, it must be treated in some manor prior to discharge to Big Lagoon State Park. Adequate treatment is of special concern due to sediment from the clay roads within Treasure Hill and the impact on the sensitive wetland areas located south of Gulf Beach Highway. It is recommended that a stormwater detention facility be constructed north of Gulf-'- Beach Highway between Cambria Drive and Medina Road.. This location seems suitable since it is presently undeveloped and is several feet lower in elevation than the surrounding property. Once the runoff is treated it can be discharged by pipe across Gulf Beach Highway and into Big Lagoon State Park. According to County Orthographic Aerial contour maps, there is a natural drainage way located 900 feet south of Gulf Beach Highway. 5-70 The construction cost for the recommended stormwater system is estimated to be approximately $395,000. This results in a cost per acre of approximately $3,300. 5-71 GRAND LAC TREASURE HILL > -i co w w C', (X OU14TIN 10 LONGWOOD DR cr 8ECX3T RD > L, n LL m m Lrl > n uJ W w ca (x M (D cr -Z w uj C) NJ 0- ui 7- >- z -1 0 L) 0 CD > z 0 GLO 0 0 D NEW CULVERTS V) cr 0 cr lz PojVr NEW GRASSED SWALE NEW PIPING SYSTEM NEW DETENTION POND NEW STORMWATER cr OUTFALL a: w BIG LAGO STATE PARK z 0 Q. 0 v 7 n LLJ :a R E 1 PONO NEW STORMW@ OUTFALL @i TF DON STA TABLE 5-14 COST ESTIMATE TREASURE HILL Unit Item.Description Quantity Unit Price Total 24" RCP 96 L.F. $28.00 $ 2,688 3011 RCP 148 L.F. $38.00 $ 5,624 36" RCP 1,200 L.F. $48.00 $57,600 42" RCP 700 L.F. $60.00 $42,000 48" RCP 550 L.F. $77.00 $42,350 54" RCP 200 L.F. $90.00 $18,000 Headwalls 8 EA $ 1,200 $ 9,600 Inlets 12 EA $1,500 $18,000 Concrete Flume 1 EA $2,000 $ 2,000 Pond Underdrains 1,600 L.F. $20.00 $32,000 Road Crossing Lump Sum $10,000 Grading 1,500 C.Y. $ 5.00 $ 7,500 Pond Excavation 7,000 C.Y. $ 5.00 $35,000 Grassing 6,000 S.Y. $ 0.30 $ 1,800 Easements 3 Acre $15,000 $45,000 Subtotal $329,162 20% Contingency $65,832 TOTAL $394,994 SAY $395,000 5-73 5.4 PERDIDO BAY RESORT AREA Perdido Bay Resort consists of approximately 500 acres of mostly developed property. Approximately 270 single-family lots and several higher density residential areas have been developed around an 18-hole golf course. The golf course was constructed with an internal lake system that serves as an outfall for the stormwater from most of the surrounding development. The terrain is fairly flat a nd except for the lake system there is not an extensive drainage system. The roadways, with curb and gutters, were constructed at very slight grades, and curb inlets are used to route the runoff into shallow storm pipes which connect individually to the lake system or Perdido Bay. many of the inlets and culverts are in need of maintenance. Proper maintenance, such as cleaning inlets, pipes and outfall ditches, should be performed immediately. The soils in the area consist mostly of Rutledge Sand which has poor natural drainage characteristics. 5.4.1 DOUG FORD DRIVE Doug Ford Drive serves as the o nly entrance road to Perdido Bay Resort. It is reported that during heavy rains the road becomes impassable due to several feet of water over the road. many complaints regarding inadequate drainage have been received. The situation is not just a minor 5-74 inconvenience when the need for adequate hurricane evacuation is considered. It is very possible that rains and high tides associated with an approaching hurricane could cut off the only evacuation route for Perdido.Bay Resort. Upon review of the situation it was discovered that approximately 100 acres of undeveloped land located north of Doug Ford Drive drains south to the roadway. In addition, a large part of the Clubhouse parking lot drains onto Doug Ford Drive. Since the drainage facilities on Doug Ford Drive consist of only one inlet and a 24-inch pipe, it is apparent that improved stormwater controls are needed. Three locations for improvements are recommended. The first location is at the intersection of Doug Ford Drive and Sorrento Road. The existing 24-inch culvert under Doug Ford Drive should be replaced with a culvert having sufficient capacity to handle the runoff carried by the swale along the west side of Sorrento Road. A The second area needing improvement is at the existing curb inlet on Doug Ford Drive. This facility should be upgraded to not only handle the runoff from the roadway, but also the runoff coming from the 100 acres of land located to the north. The improvements required could consist of a grassed swale along the north side of Doug Ford Drive to collect the runoff, an adequate culvert under the road and a grassed swale running south to Bayou Garcon. Based on preliminary 5-75 runoff calculations a 54-inch diameter culvert would be necessary. A suitable easement to Bayou Garcon would also be required. The third recommended location for improvement is near the west end of Doug Ford Drive at the intersection with Shoshone Drive. The stormwater reaching this location is generated by the Clubhouse parking area and Shoshone Drive. Since this runoff will carry contaminants from developed areas, it will be necessary to provide treatment of the stormwater in order to meet State water quality standards. Treatment could be obtained by construction of a stormwater detention pond located south of Doug Ford Drive. A limited amount of stormwater piping and inlets would also be necessary to collect the runoff and route it to the pond. Discharge from the pond could be accomplished through a grassed swale running south to Bayou Garcon. The construction cost for the upgrading of the culverts on' Doug Ford Drive is estimated to be approximately $54,000. This cost combined with an estimated $98,000 cost for improvements at the west end of Doug Ford Drive totals $152,000. It is roughly calculated that Doug Ford Drive provides access to approximately 500 acres of developed land. This results in a total cost per area of $304.00 for the recommended improvements to Doug Ford Drive. 5-76 NEW DISCHARGE PIPE NEW UNDERDRAINS PEIRDID.0 1B A Y 00 -vo lp 4- NEW PIPING Ld 0 LA 0 x LA .0- NEW NEW PIPING SYSTEM NEW STORmWATER DOL'G FORI) DETENTION POND PERDIDO '"DAY RXESOIR T IDAYOU - GAIRCO.N. TABLE 5-15; (7 0.9 T FS T I M 1\1.'F@ UUUU FURD DRIVE Unit Item Descripton Quantity Unit Price Total 42" RCP 150 L.F. $59.00 $ 8,850 5411 RCP 48 L.F. $92.00 $ 4,416 Road Replacement Lump Sum $ 6,000 Headwalls 4 EA $2,0 00 $ 81000 Grading 3,000 C.Y. $ 5.00 $15,000 Grassing 9, 000 S.Y. $ 0.30 $ 2,700 Subtotal $44,966 20% Contingency $ 8,993 TOTAL $53,959 SAY $54,000 5-78 TABLE 5-16 COST ESTIMATE WEST END OF DOUG FORD DRIVE Unit Item Description Quantity Unit Price Total 24" RCP 600 L.F. $28.00 $16,800 36" RCP 300 L.F. $48.50 $14,550 Inlets 5 EA $1,500 $ 7,500 Pond Excavation 6,000 C.Y. $ 5.00 $30,000 Sod 2,000 S.Y. $ 2.60 $ 5,200 Outlet Structure Lump Sum $ 4,000 Grading 600 C.Y. $ 5.00 $ 3,000 Grassing 1,500 S.Y. $ 0.30 $ 450 Subtotal $81,500 20% Contingency $16,300 TOTAL $97,800 SAY $98,000 5-79 5.4.2 ARAPAHO DRIVE Arapaho Drive is a residential street located at the south end of Choctaw Avenue in Perdido Bay Resort. Severe street flooding occurs along Arapaho Drive on a regular basis. It appears that the worst flooding occurs on the northern portion of the road about 400 feet east of Choctaw Avenue. There is a stormwater inlet on each side of the street at this location which drains by pipe into the golf course lake system. The water elevation of the lake system is determined by several control structures throughout the golf course. it would be possible to lower the lake elevation and increase the drainage cap acity of the stormwater system. But, this would be objectionable to many residents and it would not solve the problem. The problem is due mostly to the low elevation of Arapaho Drive and the long route of stormwater flow to Bayou Garcon. The lowest point on Arapaho Drive is approximately four feet above mean sea level. In order to obtain sufficient slope on a drainage system, a more direct route to a positive outfall is necessary. This could be accomplished by installing a piping system from Arapaho Drive directly to Perdido Bay which is located about 800 feet to the west. This approach would relieve the flooding problems, but the water quality of the Bay could be degraded by a new direct stormwater discharge. Therefore, a method to limit the discharge of pollutants to the Bay is needed. 5-80 Water quality could possibly be preserved by constructing the inlets to the new storm system six inches or more above the existing inlets. By doing this the runoff pattern during light and medium rains would be unchanged. The new system would function only during heavy rains to control the level of flooding. The discharge from the new system would be relatively pollution free since. the "first-flush" of runoff (which carries the majority of pollutants) would be dire cted into the golf course lake system. The construction cost for such a system is estimated to be approximately $99,000. It is also estimated that 73 lots would benefit. This includes all the lots on Arapaho Drive, Maya Court and the lots on Choctaw Avenue up to Navaho Drive. The resulting cost per lot is, therefore, $1,356. 5-81 TABLE 5-17 COST ESTIMATE ARAPAHO DRIVE Unit Item Description Quantity Unit Price Total 36" RCP 1,100 L.F. $50.00 $55,000 Drainage Structures 4 EA $2,000 $ 8,000 Driveway Repair 1 20 S.Y. $20.00 $ 2,400 Road Patching Lump Sum $ 2,000 Easements Lump Sum $15,000 Subtotal $82,400 20% Contingency $16,480 TOTAL $98,880 SAY $99,000 5-8? 5.4.3 ZUNI CIRCLE Zuni Circle is a 300-foot residential cul-de-sac street. located within Perdido Bay Resort. The problem on Zuni Circle is due more to groundwater than stormwater.' The watertable is above the curb most of the year. This creates a slight flow of water over the curb and water continuously stands in the gutters. The high watertable is also causing the road to deteriorate much faster than other roads in the area. The most feasible way to solve the problem seems to be by installing underdrains along both sides of the road with an outfall directly to Perdido Bay located 200 feet to the west., The estimated cost for this work is $15,000 and would benefit the six lots located on the street. it will also be a benefit to Escambia County due to decreased road maintenance. 5-83 5.5 PENSACOLA BEACH In Section 3, five problem locations were identified for Pensacola Beach, reference Figure 3-2. These areas were as follows: 1) Ft. Pickens Road, severe and extended duration flooding of the roadway near Baywatch and Boardwalk Condominiums. 2) Minor parking lot flooding, businesses west side of causeway on Little Sabine. 3) One residence on Via DeLuna between Avendida II and Avendida 12 has experienced flooding in the past. 4) Yard flooding on Maldonado Drive, one block south of Via De Luna. 5) Street flooding, frequent and severe on Ensenada Uno, a cul-de-sac. Of the five problems listed, solutions were developed for two of the problem areas, Ft. Pickens Road and Ensenada Uno. The second problem listed above was to such a minor nature, that it should not be included in a study of this scope. The third problem listed above would appear to be confined 5-84 to one residence, which is built in,'a depression with respect to everything around it. Since only one residence is involved, it did not seem appropriate to address.that problem in this report. A solution for this problem would, on the surface, involve a great deal of expenseand would probably involve pumped discharge and a long and expensive force main to some point where gravity discharge is feasible. Problem area four would appear again to mainly effect one residence. Since the structure on this lot is on pilings, there is no danger of structural flooding. The yard flooding is again due to the lot being located in a depressed area with respect to everything around it. 5.5.1 FT. PICKENS ROAD The severe street flooding on Ft. Pickens Road presents a traffic hazard during most heavy rainfalls. It seems that no roadway drainage exists to take stormwater away from the pavement. Sand has built up along the edge of pavement pre- venting water from leaving the pavement. The road grade goes through a sag curve in front of Baywatch and Boardwalk Condominiums. It is this location where stormwater collects and reaches a depth of two to three feet in the travel lane. 5-85 Alternative one involves the construction of a drainage swale along the north side of Ft. Pickens Road between the pavementledge and the parking lot for Boardwalk Condominiums. This swale will take runoff from the roadway and provide discharge through percolation of water stored to a depth of 0.5 feet. Water above this elevation will be discharged via a paved concrete swale to a point approximately 450 feet north of the center,line of Ft. Pickens Road, and 100 feet south of Santa Rosa Sound. This paved swale would be constructed through the landscaped area between the paved parking lots of Baywatch and Boardwalk Condominiums. The paved swale section proposed would be a V-section five foot wide with a 5:1 side slope. The cost tabulation for this alternative is shown on Table 5-18. A The second alternative for this location involves construc- tion and expansion of the grasses swale proposed in alternate one. This alternative would provide a means of discharging stormwater should it not be pssible to obtain gravity discharge.- The swale area is expanded to provide storage of the first one-half inch of runoff from the contributing drainage area, estimated to be 50 acres. 5-86 After this volume is filled, the pump s would cut on and evacuate detention storage provided in the pond. Under this option, the pumps would not always be able to evacuate stored stormwater as fast as it is entering, therefore, some. temporary minor flooding is possible, although not likely except during extreme events. The pumped stormwater will be discharged through a six (6) inch diameter force main and discharged into the boat basin in Lafitte Cove, four hundred and fifty (450) feet to the northeast of the proposed detention/retention swale. The tabulated cost estimate for alternate two is shown on Table 5-19. Compared to the first alternate, this alternate at $44,000.00 is almost double the estimated cost of alternate number one, which costs $23,000.00. The pumped storage alternate two does provide an environme'n- tal improvement over alternate one at a slightly reduced level of service. Maintenance and operations cost for the pumping station were not included in the cost estimate, but is expected to be around five thousand ($5,000.00) dollars annually. The point evaluation for these two alternates is shown on 5-87 Table 5-19. Based on the evaluation, alternate one is the preferred solution. 5.5.2 ENSENADA UNO The problem here is again severe steet flooding of extended duration. Basically the street has no place to drain. All yards along the east and of the cul-de-sac street have been filled to well above road grade. There does not appear to be a simple solution to this problem. It is recommended that an oversize inlet be placed at the low point on the cul-de-sac and a small submersible pump with float controls be placed in the inlet. Discharge will be pumped through a 3 or 4 inch force main along Via De Luna to a large private lake approximately 1050 feet east of the cul-de -sac. Additionally, 6-inch diameter perforated pipe should be extended fifty to seventy five feet from the inlet to maximize the infiltration of stormwater. The only other option is the construction of a gravity storm sewer. However, there does not appear to be anywhere to drain by gravity without disturbing one or more residences on the steet. Also, a gravity drain to the Sound may prove difficult to construct without providing some sort of treat- ment prior to discharge. 5-88 TABLE 5-18 COST ESTIMATE ALTERNATE ONE PENSACOLA BEACH FT. PICKENS ROAD Item Description Quantity Units Unit Price Total Swale Excavation 900 C.Y. 5.00 4,500.00 Paved Swale 250 S.Y. 35.00 8,750.00 Remove Existing Pavement 60 S.Y. 3.30 200.00 Relocate Dumpster Pad 16 S.Y. 50.00 800.00 Sodding 15,000 S.F. 0.20 3,000.00 TOTAL $17,000.00 20% ENGINEERING & ADMINISTRATION 3,500.00 + 20% CONTINGENCIES 4,500.00 GRAND TOTAL $25,000.00 TABLE 5-19 COST ESTIMATE ALTERNATE TWO PENSACOLA BEACH FT. PICKENS ROAD Item Description Quantity Units Unit Price Total Swale Excavation 1600 C.Y. 5.00 8,000.00 Pump Station and Wet Well 2-250 GPM Pumps Lump Sum 15,000.00 6" P.V.C. Force Main 450 L.F. 10.00 4,500.00 Ln 1@ Sodding 15,000 S.F. 0.20 3,000.00 CD Pavement Removal and Replacement 30 S.Y. 10.00 300.00 TOTAL $31,000.00 20% ENGINEERING & ADMINISTRATION 6,000.00 + 20% CONTINGENCIES 7,000.00 GRAND TOTAL $44,000.00 TABLE 5-20' ALTERNATE EVALUATION PENSACOLA BEACH FT. PICKENS ROAD ALTERNATE ALTERNATE NO. 1 NO. 2 Economic Impact 4 2 Environmetal Evaluation 2 4 Level of Service Provided 4 3 Downstream Impacts 2 3 Human Issues Evaluation 3.8 3.2 15.8 15.2 5-91 z -A -ROSA @''.-'SOUND 0 co Ld w CONSTRUCT 450 L. F. c/) PAVED SWALE - 5.0'ft- < WIDE. 10.0' EASEMENT REOUIRED. BOARDWALK CONDOMMUMS fz Ez LAFITTE COVE z o BAYWATCH P777,7777 11171 z CONSTRUCT 90oo C. - F. RETENTION SWALE. RETENTION AREA FORT PICKENS z ROAD PORTSIIDE cn 0 L.L Im -i it D CD cn GUIF 0 F MEXICO E N. I'm z -:@-.SOUND, SANTA ROSA 0 w 0 CONSTRUCT PUM w BOARDWALK STATION & WET W U) CONDOMINIUMS 2 - 250 GPM PUM oa LAFIT COVE < EM 0 z -7 o BAYWATCH V771 -7= FT17=11A z CONSTRUCT 180 00 C. F. RETENTION FACILITY. FORT 0 PICKENS ROAD z CONSTRUCT 6.0 PORTSIDE P.v.c. FORCE h U) 0 im LL ir _j D 0 to GULF -.OF MEXICO The pumped discharge option seems to be the best solution for this location. The total cost of this solution is estimated to be twenty-four thousand dollars ($2,400.00). 5.6 JONES SWAMP AND GARCON SWAMP BASINS Only a small portion of Jones Swamp lies in the study area and no significant problems were identified in this study. There are significant problems associated with the swamp further east outside of the study area. No structural measures are proposed in the basin. The Garcon Swamp Basin is entirely located within the study area, but to this point is substantially undeveloped. The Perdido Bay Resort west of Bauer Field Road is in the Garcon Bayou Basin and drainage problems.were identified in that area and solutions are addressed in Section 5.4. However, east of Bauer Field Road (C.R. 293) there were no problems identified within the Garcon Swamp Basin. Potential problems are addressed by the non-structural measures recommended in Section 6.1. 5-94 5.7 PARADISE BEACH Most of the residential development in Paradise Beach is along Perdido Bay and Highway 98 (Lillian Highway). There is no central drai nage system. Most of the runoff flows overland into the Bay or is collected by roadside swales which discharge into the Bay. Due to the relatively high land and short outfall distance to the Bay, no stormwater problems are apparent'. There is a large undeveloped area located south of Highway 98 which currently drains through a 48-inch culvert under the, Highway. Future development of this area will require adequate stormwater planning in order to meet County regulations and not adversely'impact the nearby surface waters. 5.8 BRONSON FIELD BASIN A Bronson Field is an abandoned U.S. Navy Air Base. A major portion of the surface runoff from the Base is collected by a relatively large ditch along the south property line. This ditch is connected to Perdido Bay and in recent years it has been extended to the northeast to assist in the drainage of Wildwood Lakes subdivision. Wildwood Lakes is located east of Bauer Road and has an internal lake system which connects to the Bronson Field ditch through two 36-inch culverts under Bauer Road. All the streets within the subdivision are known 5-95 to flood for a short period to a depth of 6 to 9 inches during extremely heavy rains. However, it seems that the developers anticipated the situation and constructed all the homes well above street level. Water has also crossed over Bauer Road during some of the most severe rains. Due to the minor and infrequent nature of the flooding, no improvements are recommended. 5.9 PERDIDO KEY/INNERARITY AREA 5.9.1 PERDIDO KEY Historically, there has been very little runoff from the largely undeveloped lands on Perdido Key. The loose white sand on the Key has excessive natural drainage due to the rapid permeability of the soil. The voids within the soil provide space for the storage of infiltrated rainfall. As much as one-third of' the total soil volume above the water table is void and available for stormwater storage. As a-i result only areas with a high water table produced stormwater runoff on the Key before extensive development began in the late 19701s. The majority of the recent development has been along Perdido Key Drive. There is no defined stormwater system along the roadway and as individual projects were developed, individual stormwater systems were constructed. most, if not all the systems utilize the high infiltration rate of the natural 5-96 soil. In general, stormwater is directed from impervious areas to pervious areas where the runoff infiltrates the soil and percolates down to the water table. This method is effective as long as the percolation areas do not become "blinded' by fines, oils or other foreign material. It is also necessary to have sufficient storage volume in the soil above the watertable. Since there is no discharge to surface waters, this method resul ts in very little pollution of surface waters. Since the majority of properties on Perdido Key are waterfront and well drained, a stormwater master plan is not needed for these areas. However, there is a fairly large and mostly undeveloped interior area in the Gulf Beach Heights Subdivision. A portion of this area outfalls into Old River through 3-48" RCP's under River Road. The area is characterized by remnants of sand dunes with fairly high ridges and long low areas between the ridges. The lower areas contain standing water most of the year. Except for the area which outfalls into Old River, most of the low areas drain to the east through culverts under Perdido Key Drive. Most of the low areas contain wetland vegetation and will be protected from filling to some degree by the United States Army Corps of Engineers and the Florida Department of Environmental Regulation wetland regulations. Since the low areas act as natural drainage ways during heavy storms, it is important that they are preserved and not filled during the development of the area. 5-97 5.9.2 INNERARITY PENINSULA The Innerarity area is approximately five miles long and about one-half-mile wide, at the widest point. it is bordered on the north by Perdido Bay and on the south by the intracoastal waterway. The soil, for the most part, is sandy and well drained. The stormwater system consists mostly of roadside swales with no central well defined collection system. Due to the relatively short distance of overland flow to the adjacent surface waters there seems to be no serious problem with flooding caused by stormwater runoff. However, there are some slightly depressed areas with a high water table in which some ponding of stormwater was observed. This ponding seems to be of short duration and no structural flooding was discovered. It appears that periodic maintenance of the existing roadside ditches could eliminate some of the ponding problems. The quality of the stormwater runoff in the Innerarity are-a is of special concern. There are many unpaved clay streets which run perpendicular to the shoreline. Runoff flows along these streets carrying suspended clay particles and silt directly into the nearby surface waters. Measures should be taken to stabilize the roads and control the discharge of pollutants. 5-98 5.10 TARKILN BAY The Tarkiln Bay area is almost entirely undeveloped. The land around Tarkiln Bayou consists mostly of low wetland areas. There is a large area of high ground located to the west of Tarkiln Bayou on Perdido Bay. This area is highest along the Bay and slopes gradually toward the Bayou. Due to the pristine nature of Tarkiln Bayou and the surrounding area, special care should be taken during its development. 5.11 SANDY CREEK/WEEKLEY BAYOU BASIN The Sandy Creek Basin is mostly undeveloped east of Bauer Road. The land is fairly flat with wetland areas separating areas of higher elevation. It will be important during the development of this area that the existing wetland areas and associated drainageways are preserved. Some of this area is classified as a flood zone according to the Federal Emergency Management Agencies Flood Insurance Rate Map. The flood elevations have not heen determined and it is recommended that future developments establish a safe building elevation based on detailed stormwater ca lculations. The Weekley Bayou area is located west of Bauer Road and is mostly developed with single-family residences. The land is relatively high and slopes toward Weekley Bayou. -Some minor stormwater problems occur in this area. It seems that most 5-99 problems can be resolved with routine maintenance of the existing roadside ditches 5-100 6.0 NON-STRUCTURAL RECOMMENDATIONS 6.1 GENERAL RECOMMENDATIONS During the course of this study, a number of factors, not attributable to natural causes, have been identified that are perceived by residents in the area as causing or contr--*- buting to drainage problems ex perienced. Some of these fac- tors are more apparent than oth ers, but most possess some degree of validity. Those factors that have been determined to contribute the most to drainage problems in the area are as follows: 1) Inadequate or no maintenance of the existing drainage network of pipes and ditches. 2) Construction of roadway embankments (fill sections). 3) New developments and the associated increase in stormwater runoffs. 4) Alterations of drainage by adj acent property owners who fill or excavate on their property. 5) Stormwater improvements to relieve problems in one area that create new problems in another area. 6-1 6) Inadequately sized driveway culverts. 7) Sediment deposition into streams, bayous, and yards caused by unstabilized roadways or ditches. All of the above concerns can be addressed by aggressive and comprehensive maintenance and regulatory programs. General maintenance recommendations that apply to the entire study area are as follows: 1) Clear and remove weeds, brush, beaver dams, and trees from major drainage channels (D.A. > 30 Ac.) at least twice annually. 2) Inspect major channels a minimum of once a year for sediment accumulation and remove by dredging if necessary. 3) Clean and mow roadside ditches at least three times per year, including cross drains and driveway A culverts. 4) Where easements do not exist for maintenance of drainage facilities, pursue obtaining easements, even if it means condemning property. Maintenance is too critical to area drainage not to have ease- ments for that purpose, particularly with the large number of open ditches. 6-2 It is anticipated that an increase in road operations staff will be nece ssary to accomplish this level of maintenance and those costs have been included in the analysis of struc- tural alternatives in Section 5.0. Regarding new roadway construction in the study area, an important factor must be considered in their design and construction. Since most of the area is vi rtually level, stormwater will tend to build up in layers on the land and flow in sheets toward an outlet. When the sheets reach a roadway in a fill section, the roadway ditch, or in most cases., the property adjacent to the roadway becomes a con- centration point for tremendous volumes of water. Since the ditches are so flat, normal roadway ditch sections will not suffice. In fact, there are areas adjacent to Dog Track Road that flood to depths of two to three feet and cover fifty (50) to seventy-five (75) acres. Two options exist to deal with this problem. One option i's to construct an extensive longitudinal conveyance system on the upstream side of the roadway. To do this would require additional right-of-way and unusally large ditch sections and large, low head driveway culverts or bridges. Even this will not work if cross-drain culverts do not have a positive outlet. 6-3 A second option that may have a higher initial cost but would be much less expen sive over the long term would be to provide longitudinal collection channels along the rear pro- perty lines of the property abutting the upstream side of the roadway and provide lateral channels.to carry stormwater through ''cross-drain culverts perpendicular to the roadway. This solution would require more planning effort and higher property acqu isition costs, but would provide a safer, more efficient method of collecting and transporting stormwater from one side of the roadway to the other. The obvious advantage is the absence of large, deep ditches immediately adjacent to the roadway and subsequently the need for large expensive driveway culverts to enable access to the roadway. Another advantage to this solution is the ability to space large cross drains further apart, rather than have the bat- tery of culverts existing under the major roadways in the area. Most of these culverts do little but equalize water A levels from one side of the road to the other, since no positive outlet exists particularly along Blue Angel Parkway and Sorrento Road. If it is expected that development along a roadway will be limited or prohibited, then these two options are not needed except in those areas where development exists prior to roadway construction. 6- 4 In these areas, it may be necessary to alter the drainage design concept to preven t adverse impacts to existing deve- lopments along the roadway. Even though new developments effect stormwater runoff in terms of water quality and quantity, existing ordinances, if properly enforced should deal effectively with new develop- ments to minimize any adverse impacts. Escambia County's Stormwater Management and Conservation Ordinance No. 86-32 deals effectively with the rate and quality of stormwater leaving new developments. Review of this ordinance reveals that developers are required to control the rate of runoff from their project sites to predevelopment levels for up to the critical dura- tion 25 year design storm. This duration is determined by computing the peak site discharges associated with various duration events. The event that produces the largest volume or highest rate of net stormwater runoff (post-development' less pre-development) is the critical duration event. Also, developers are required to retain onsite a volume of water equivalent to the first inch of runoff to remove pollutants and suspended solids by preventing discharge of this stormwater into surface waters and requiring evacuation of this stored stormwater by percolation, evaporation, or evapotranspiration. 6-5 it is this area of the ordinance that needs expanding to include other methods of treating stormwater runoff. Due to the high water tables in most of the study area, recovery of the retention volume within a reasonable period of time is highly unlikely. For this reason, alternate treatment methods should not only be allowed, but be encouraged, for those areas with soil types not conducive.to infiltration. The Florida Department of Environmental Regulation currently allows detention with filtration, "wet" detention, and wetland discharge as alternate methods of meeting stormwater discharge water quality requirements. It is recommended that Escambia County should encourage the use of "wet" detention facilities for stormwater treatment. These faci- lities have demonstrated treatment efficiencies equivalent to other methods and pollutant removals of phosphorus, nitrogen, and some metals actually exceed that of other treatment methods.(2) A These facilities have a permanent pool or volume of water with flat littoral shelfs above the permanent pool. Gravity draw down of this littoral zone is allowed after a specified period of detention. These facilities have the advantage that they can become attractive additions to a development due to their natural appearance and functioning. (2) "An Assessement of Stormwater Management Programs", December, 1985, Camp, Dresser & McKee 6-6 current DER criteria for these facilities are listed on Exhibit 6-1. Recommended wetland species, that are required planting for the littoral shelf around the perimeter of the permanent pools are listed on Exhibit 6-2. One drawback to utilizing this treatment method is the ina- bility to process these facilities under the general permit requirements of F.A.C. 17-25. Instead, these facilities must be constructed under the construction permit require- ments of F.A.C. 17-25, a more rigorous technical and admi- nistrative procedure. This could act as a deterrent to widescale use by developers. Another area where E scambia County must intensify enfor- cement procedures is in the area of single family construc- tion activities on individual lots. Grade changes made on one lot can seriously impact a neighboring lot. For this reason, some review procedure must be implemented which eva- luates the impact of individual lot construction. This is" particularly important since ditching or filling of the level terrain in the study area can modify the hydrology of an entire watershed. This same type of review should also include minor drainage improvements, ditch maintenance, roadway grading activities, and driveway pipe installations by Escambia County Road 6-7 Operations. An engineering evaluation of the impact of any construction by Road Operations personnel should be made to insure that the improvements made do not impact other areas in the drainage basin or significantly alter existing drainage patterns in the area where improvements are made. A fragmented approach to solving localized drainage problems should be avoided. This review process would apply only to new construction where grade changes are necessa ry, not nor- mal maintenance activities such as cleaning ditches and storm sewers. This maintenance should not include grade change changes in ditches that change the direction of flow or introduce new stormwater into a system. Roadway fills for graded unpaved roads should utilize materials native to the area where the construction is taking place. The intro- duction of material containing a substantial percentages of fines, such as clays and silts, to an area predominantly sand should be avoided, unless it is determined by the County Engineer that native materials do not provide the structural stability required for the roadbed. This is important, since the introduction of fines may clog or blind native soils and reduce their ability to infiltrate stormwater.. Also, significant grade changes in road grading operations should be avoided, unless an engineering eva- 6-8 luation of the anticipated grade change is made. No change in the existing drainage system should ever be a part of road maintenance activities. If it is anticipated that changes to the road drainage system are required, then an engineered plan should be prepared for that purpose. In no instance, should driveway culverts be installed without an engineering evaluation of the culvert size(s) required to safely pass expected flows in the ditches. This evaluation is necessary to insure that improperly sized culverts do not impede the flow of stormwater and either cause or increase flooding of private. property. 6.2 SPECIFIC RECOMMENDATIONS FOR SELECTED AREAS The recommendations made in Section 6.1 apply to all basins within the study area. However, speci-fic recommendations for particular areas are needed due to problems inherent to an area. For those areas, new guidelines or particular emphasis of some of the general recommendations is required. For instance, in Section 5.1, in the analysis of alter- natives for the Bridge Creek Basin, areas are shown on Figure 5-1 where maintenance of natural storage is required. It is recommended that these areas be purchased 6-9 the wetland area. The Florida Department of Environmental, Regulation has strict guidelines outlining the use of wetlands to treat both point and non-point source discharge into wetlands. No roadway should be proposed across the swamp which would impede the flow through the swamp or alter natural flow velocities. Since the slow methodical movement of water through the swamp is a key feature to the pollutant removal efficiency of the swamp, channelization of stormwater in the swamp or signi ficantly restricting the flow area should not be allowed. Much of the coastal area south of the Garcon Swamp Basin and north of Gulf Beach Highway remains undeveloped. New deve- lopments in this area should consider two factors. First, the existing infrastructure along Old Gulf Beach Highway is inadequate to handle existing flows. Therefore, any new developments north of Old Gulf Beach Highway should consid'6r the capacity of the system along and unde r the highway in designing the detention facilities required by ordinance to serve their developments. For this reason, the discharge from the development should in many cases be less than pre- development-due to restrictions downstream. Developments in this area should also consider that there 6-10 are numerous depressions in this area which fill during storms and flood large areas to depths of two (2) to four (4) feet. Flood elevations can be controlled with proper design of a drainage system which controls the rate of discharge, but allows evacuation of stormwater early enough in a storm so that massive accumulation of stormwater is prohibited. Another area where potential problems exist is Pensacola Beach. It is recommended that future developments on the Beach be required to meet Escambia County's Stormwater and Conservation Ordinance No. 86-32 in designing stormwater management facilities to serve developments. Due to the tremendous capability of natural soils on the beach to per- colate stormwater, there has been too much reliance on the soils to handle large amounts or stormwater without gravity outfalls. Future developments should consider providing drainage systems which meet all regulatory requirements, but have the capability of gravity discharge of overflow storm- waters. All of the problems occurring on Pensacola Beach are due to the absence of a drainage system that provides discharge of stormwater when the native soils are saturated and cannot intake surface runoff as fast as it is being received.. If existing stormwater ordinances are enforced and surface 6-11 discharge capabilities are provided, future problems can be avoided. The recommendations made in this section and Section 6.1, if followed, will greatly aid in the management of existing problems and the prevention of future stormwater quantity or quality problems. 6-12 CURRENT DER CRITERIA FOR WET DETENTION SYSTEMS a) 1" of runoff storage above level of permanent pool. b) This volume to be bled down at a slow rate. No more than 1/2 volume to be discharged in first 60 hours following an event. c) Volume in the permanent pool must provide for a resi- dence time of at least 14 days. This volume may be determined by estimating 3.83% of annual average runoff. A more empirical approach sometimes used is calculated by taking 2 inches times the impervious acreage in the project plus 1/2 inch times the pervious acres. d) A littoral shelf should be provided by extending and gently sloping the sides of the facility (6:1 or flatter) out to a point 2-2.5 ft. below the water's surface. e) No more than 70% open water is recommended. The A remaining 30% (i.e., littoral shelf) typically is established with aquatic vegetation. A layer of muck (6" recommended) may be incorporated into the littoral area to promote establishment of wetland vegetation. Planting of native aquatic plant species is highly recommended. Lining the bottom and sides of these faci- EXHIBIT 6-1 lities with a la yer of organic material such as much appears to be an attractive alternative when potential groundwater contamination problems are apparent.. f) A mean depth of 3-10 ft. should be planned for the per- manent pool. g) Inlet structures should be designed to minimize tur- bulence in the pond. Baffles are the most commonly used structures for such purposes. Inlets should not be located in close proximity to the outlet so as to pre- vent short circuiting. h) Facilities that are potential sources for oil and grease contamination must include a skimmer or other mechanism to prevent these substances from leaving the facility. i) Erosion and sediment control BMP's must be used to retain sediment on site during construction. BMP's must be shown on the design plans and the engineer must pro@_ vide instructions'for proper 0 & M. j) Preferably, pretreatment in the form of landscape reten- tion areas or perimeter swales is incorporated into the stormwater management system to provide infiltration and treatment of the first half inch of runoff to prevent the wet detention lake from eutrophying. A credit EXHIBIT 6-1 against the required wet detention storage volume may be provided depending upon the amount of stormwater infiltrated. A dual pond system (see attached) is pre- ferred and easily designed and constructed. DER is currently in the process of developing a list of suitable plant material and sources of supply for appropriate native aquatic vegetation. Contact Keith McCarron (904) 487-1779, Suncom 277-1779 for information. EXHIBIT 6-1 PLANT.SPECIES SUITABLE AND SOMETIMES AVAILABLE FROM NURSERIES FOR LITTORAL ZONE PLANTINGS OF DETENTION PONDS* COMMON NAME SCIENTIFIC NAME American elml Ulmus americana Arrowhead Saggiteria, lancifolia Banana water lilY2 Nymphaea mexicana Black guml Nyssa biflora Bulrush Scirpus spp. Button-weed Diodia virginiana Buttonwoodl Cephalanthus.occidentalis Carolina willowl Salix caroliniana, Coinwort Hydrocotyle umbellata Cypressl Taxodium spp. Cinnamon fern Osmunda cinnamomea Day flower Commelina. diffusa Floating hearts2 Nymphoides aquatica Frog's-bit Limnobium spongia Hat pins Eriocaulon decangulare Iris Iris hexagona. Knotweed (Smartweed) Polygonum spp. Lizard tail Sarurus cernuus Loblolly bayl Gordonia lasianthus Maidencane Panicum hemitomon Pickerelweed Pontederia cordata Popashl Fraxinus caroliniana Redbayl Persia palustris Red maplel Acer rubrum Rushes Eleochris spp. Sawgrass Cladium jamaicense Sedges Cyperus spp. Southern cutgrass Leersia hexandra Soft rush Juncus effusus St. John's wort Hypericum fasciculatum Swamp bayl Magnolia virginiana. Swamp lilY2 Crinum americanum Virginia willowl Itea virginica Wax myrtlel Myrica cerifera White water lily Numphaea odorata Yellow eyed grass Xyris spp. Yellow pond lilY2 Nuphar luteum other species may be suitable and may be used with approval 1 = Tree or shrub; more suitable for higher elevations 2 = more suitable for deeper water (i.e. greater than 1-2. feet) EXHIBIT 6-2 US Department of Commerce EOAA Coastal Services Center Library 2234 South Robson Avenue Charleston, SC 29405-2413 001 3575