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Task 63 FY 90 Final Work Product Stafford County Ground Watel, ocqq rqo@ Resource Protection Program x loraphy 9 rill Net Pc-- roe a t7i azer C @ M Araulic (A) coniuczivity @ M \ xM \000MMM Prepared for: County of Ste@fford Staff, ord, VA By: GKY and Associates, Inc. Springfield, Virginia FINAL REPORT December 31, 1991 TD 403 .S73 lound Water Resource Protection ProVam was funded, in part, by the Vi@giili tz 1991 f on the Environment's Coastal Resources Management Prograin through NrA90A.4-H-CZ796 of the National Oceanic andAtinospheric Administration fie Coastal Zone Man'agement Act of 1972, as amended. Received by: Council on the Environment STAFFORD COUNTY GROUND WATER RESOURCE PROTECTION PROGRAM JAN 29 1992 Prepared for: County of Stafford 1300 Courthouse Road P.O. Box 339 Stafford, VA 22554-0339 Prepared by: GKY and Associates, Inc. 5411-E Backlick Road Springfield, VA 22151 (703)642-5080 U.S. DEPARTMENT OF COMMERCE NOAA COASTAL SERVICES CENTER 2234 SOUTH HOBSON AVENUE CHARLESTON , SC 29405-2413 December 31, 1991 Property of CSC Library TABLE OF CONTENTS Page COVER PAGE ............................................................... i TABLE OF CONTENTS ........................................................ ii LISTS OF TABLES AND FIGURES .............................................. iv SECTION 1. INTRODUCTION ................................................. 1 PURPOSE .............................................................. I BACKGROUND ........................................................... 1 SECTION 2. GROUND WATER ................................................. 3 COUNTY GROUND WATER RESOURCES ................. ...................... 3 GROUND WATER COMTAIMINATION .......................................... 3 SECTION 3. METHODOLOGY ................................................... 5 DRASTIC OVERVIEW ..................................................... 5 Depth to Water .................................................... 7 Net Recharge ....................................................... 7 Aquifer Media ..................................................... 7 Soil Media ........................................................ 7 Topography ........................................................ 8 Impact of the Vadose Zone ......................................... 8 Hydraulic Conductivity ............................................ 8 The DRASTIC Parameters ............................................ 9 DRASTIC RANKING SYSTEM ............................................... 10 DRASTIC MODEL ........................................................ 17 SECTION 4. DATA COLLECTION AND RATING DEVELOPMENT ....................... 18 DEPTH TO WATER ....................................................... 18 NET RECHARGE ......................................................... 18 AQUIFER MEDIA ........................................................ 18 SOIL MEDIA ........................................................... 19 TOPOGRAPHY ........................................................... 19 IMPACT OF THE VADOSE ZONE MEDIA ...................................... 19 HYDRAULIC CONDUCTIVITY ............................................... 20 SECTION 5. RESULTS ...................................................... 21 STUDY SUMMARY ........................................................ 21 SPREADSHEETS ......................................................... 21 SURFER ............................................................... 21 MAPPING DRASTIC RESULTS .............................................. 22 ii TABLE OF CONTENTS (continued) Page SECTION 6. GROUND WATER RESOURCE PROTECTION OVERLAY AREAS ............... 24 GUIDELINES FOR LOW GROUND WATER POLLUTION POTENTIAL AREAS ............ 24 GUIDELINES FOR MODERATE GROUND WATER POLLUTION POTENTIAL AREAS ....... 25 GUIDELINES FOR HIGH GROUND WATER POLLUTION POTENTIAL AREAS ........... 26 GLOSSARY ................................................................. 27 REFERENCES ............................................................... 28 APPENDIX A: DRASTIC DATA BASE ........................................... 30 APPENDIX B: GEOGRAPHIC DISTRIBUTION OF DRASTIC PARAMETER RATINGS ........ 43 LIST OF TABLES No. Page 1. Assigned Weights for DRASTIC Features ....... ...... 11 2. Ranges and Ratings for Depth to Water ................................ 12 3. Ranges and Ratings for Net Recharge... *'**** ......................... 14 4. Ranges and Ratings for Aquifer Media *'***** ........................... 14 5. Ranges. and Ratings for Soil Media ..................................... 15 6. Ranges and Ratings for Topography ................... :**'****''* ... -* 15 7. Ranges and Ratings for Impact of the Vadose Zone Media ................ 16 8. Ranges and Ratings for Hydraulic Conductivity ......................... 16 LIST OF FIGURES No. Page 1. DRASTIC Parameter Schematic ........................................... 6 2. DRASTIC Overlay Scheme .............. * .................................. 13 3. Depth to Water (D) Rating ............................................. 44 4. Net Recharge (R) Rating ............................................... 45 5. Aquifer Media (A) Rating ............................................... 46 6. Soil Media (S) Rating ................................................. 47 7. Topography (T) Rating ........ : ........................................ 48 8. Impact of Vadose Zone (1) Rating ...................................... 49 9. Hydraulic Conductivity (C) Rating ..................................... 50 10. Composite DRASTIC Index Rating ........................................ 51 iv SECTION I INTRODUCTION PURPOSE The purpose for developing a Ground Water Resource Protection Program as a part of the Shoreline Area Management Plan component of the Stafford County Comprehensive Plan is to assist the Board of Supervisors and Planning Commission in making land use decisions. The data, maps, and recommendations from this document will be used in determining a potential development's impact on the County's ground water resources and to provide recommendations which can mitigate any potential degradation identified. Development must proceed in a manner that is not detrimental to the County's ground water resources. In July 1988, Section 15.1-446.1 of the Code of Virginia (1950), was amended to add ground water protection as an item that. local governments should consider when evaluating land use proposals. A growing awareness of the vulnerability of ground water to pollution, especially from development, has led the County to seek a coordinated effort to protect ground water resources. Residential, commercial, and industrial uses rely heavily on ground water to supply a portion of their needs. Indeed, in many areas of the County, ground water is the only feasible source of water. This Ground Water Resource Protection Program was funded, in part, by the Virginia Council on the Environment's Coastal Resources Management Program through grant #NA90AA-H-CZ796 of the National Oceanic and Atmospheric Administration under the Coastal Zone Management Act of 1972 as amended. BACKGROUND Stafford County is located in the northeast region of Virginia approximately fifty-six (56) miles north of Richmond and forth (40) miles south of Washington, D.C. The County is bisected by 1-95, which is also the' approximate dividing line between the two physiographic regions (Coastal Plain and Piedmont) which define the surface features of the County. Currently, the County draws its public water supply from two impoundments, Abel Lake and Smith Lake, that rely, in large part, upon ground water recharge. In addition, approximately one-half of Stafford County residents rely on private wells recharged by ground water supplies. These recharge areas need to be identified and strategies developed to ensure a safe and adequate water supply for the County. Stafford County is a predominantly rural locality experiencing the pressures of suburban development from the Fredericksburg and Northern Virginia.areas. The 1990 decennial census documented a fifty-one (51) percent growth rate in the County from 1980-1990 from 40,470 to 61,236. This has resulted in a greater need to ensure that the development which occurs is planned in a way that protects the County's ground water resources. This Ground Water Resource Protection Program is the first step towards ensuring that as development occurs, specific strategies are implemented to protect the County's ground water resources. 2 SECTION 2 GROUND WATER COUNTY GROUND WATER RESOURCES Stafford County is in the position of having ground water reserves; however, this supply is a dynamic resource intimately connected with and affected by general land use activities. Ground water is generally recharged through water percolating through the soil or through direct resupply by surface water in areas where ground water aquifers outcrop at the surface. The quantity and quality of the water that reaches the ground water aquifers depends on the amount and type of topography, vegetation, soils, land use, and underlying bedrock. That ground water is naturally cleansed of pollution as it moves through the soil is a common misconception. Although soil has the capacity to filter and absorb pollutants, many pass through the soil layer. Increasing the amount of pollutants entering the soil will lessen the soil's ability and capacity to filter pollutants. In addition, stream, marsh, and wetland environments and the sensitive wildlife habitats they support are preserved by ground water during dry periods. In Stafford County, a large surface recharge area for the Potomac aquifer is located along, and generally parallel to, 1-95. This recharge area is located at the fall line (the dividing line between the Coastal Plain and Piedmont Physiographic Regions). This aquifer provides an important water resource to residents in the eastern part of the County and for residents in King George County. Other aquifers that are within the County include: the Piedmont in the western part of the County, the Chickahominy/Piney Point and the Aquia in the southeastern section of the County, and the Potomac in the central and northern portions of the County. Residential, commercial, and industrial land uses, if improperly developed, can have an adverse impact on the County's ground water resources. This Ground Water Resource Protection Program provides recommendations that can assist'in protecting ground water resources while still providing for growth and development. GROUND WATER CONTAMINATION Ground water pollution is caused by a variety of substances originating from many different activities. In general, pollutants enter ground water through the following pathways: 1) improper application of fertilizers, pesticides, and other water soluble products on the land surface; 2) runoff frdm development 3 sites; 3) leakage from landfills, underground storage tanks, and improperly operating septic systems; 4) improper storage and disposal of toxic substances; 5) the burial in the ground of inorganic (man-made) substances or organic substances that nave been chemically treated; 6) the injection of materials into the ground; and 7) the leaching of pollutants from the soil or bedrock. After release on the land surface, the pollutant may infiltrate downward through the soil. If the volume of pollutant is not great, the pollutant may be attenuated. If the pollutant is not completely attenuated, it may later be flushed toward the water table by infiltrating precipitation or additional amounts of pollutant. The majority of pollutants will generally travel in the direction of ground water flow at a velocity slightly less than that of the ground water. The attenuation process includes mechanisms which reduce the velocity of the pollutant through processes such as dilution, dispersion, mechanical filtration, volatilization, biological assimilation and decomposition, precipitation, sorption, ion exchange, oxidation-reduction, and buffering and neutralization. The degree of attenuation which can occur is a function of 1) the time that the pollutant is in contact with the material through which it passes, 2) the grain size and physical and chemical characteristics of the material through which it passes, and 3) the distance which the pollutant has traveled. In general, for any given material, the longer the time the pollutant takes to move through the material and the greater the distance of the movement, the greater the effects of attenuation. In a similar manner, the greater the surface area of the material through which the pollutant passes, the greater the potential for sorption of the pollutant and, hence, for attenuation. The greater the reactivity of the material through which the pollutant passes, the greater the potential for attenuation. Any combination of these processes may be active depending on the hydrogeologic conditions and the characteristics of the pollutant. It is therefore necessary to have a general idea of these processes and whether they are active. The effectiveness of dilution and attenuation processes is largely determined by 1) the rate and loading of the applied pollutant, 2) the characteristics of the pollutant, and 3) the physical and chemical characteristics of the area. Ultimately, it is these factors which control the ground water pollution potential of any area. The rate and loading factor is generally of site-specific character. However, it is the physical properties characterized by the hydrogeologic characteristics of the area that determine the extent to which the attenuation'mechanisms may have the potential to be active. Because it is neither practical nor feasible to obtain quantitative evaluations of these intrinsic mechanisms from a regional perspective, it is necessary to look at the broader physical parameters which incorporate the many processes. This is accomplished under the DRASTIC methodology. Each of the DRASTIC parameters includes various mechanisms which will help to evaluate the vulnerability of ground water to pollution. When this is coupled with an understanding of the hydrogeology of the area, the result will be a clearer image of the potential for pollutant travel and attenuation. 4 SECTION 3 NETHODOLOGY DRASTIC OVERVIEW The DRASTIC (Aller, et al., 1987) model was used to evaluate ground water pollution potential in Si-afTo-rd County. This section discusses the DRASTIC methodology and how it was applied in this study. DRASTIC is a methodology for evaluating the relative ground water pollution potential of an area through the application of an environmental component rating system. This rating system allows for the assessment of the vulnerability of an area to ground water contamination based on various hydrogeologic parameters. DRASTIC was developed by the National Water Well Association under the sponsorship of the Environmental Protection Agency. The following discussion is largely taken from the DRASTIC documentation (Aller, et al., 1987). DRASTIC is an acronym that represents the most important physical characteri sti cs, ei ther al one, or i n combi nati on, for determi ni ng suscepti bi 1 i ty to ground water contamination. The DRASTIC factors represent measurable parameters for which data is generally available from a variety of sources without detailed reconnaissance. D - Depth to Water; R - (Net) flecharge; A - Aquifer Media; S - Soil Media; T - lopography (Slope); I - Impact of the Vadose Zone Media; and C - Conductivity (Hydraulic) of the Aquifer. These factors, as shown in Figure 1, form the acronym, DRASTIC, for ease of reference. While this list is not all inclusive, these factors, in combination, were determined to include the basic requirements needed to assess general pollution potential. 5 Pre cipltat4om Topography (T) to Water (0) 0 V Ol/ IV INEEM11\', Hydraulic Coniuct4vity (C) Figure 1 DRASTTC Parameter Schematic 6 Depth to Water Depth to water is important primarily because it determines the depth of material through which a pollutant must travel before reaching the aquifer, and it may help to determine the contact time with the surrounding media. In general, there is a greater chance for attenuation to occur as the depth to water increases because deeper water levels imply longer travel times. The ranges in depth to water as defined in the DRASTIC system have been determined based on what are considered to be depths where the potential for ground water pollution significantly changes. Net Recharge The primary source of ground water typically is precipitation which infiltrates through the surface of the ground and percolates to the aquifer. Net recharge represents the amount of water per unit area of land which penetrates the ground surface and reaches the water table. This recharge water is thus available to transport a pollutant vertically to and horizontally within the aquifer. In addition, the quantity of water available for dispersion and dilution of the pollutant in the vadose zone and in the saturated zone is controlled by this parameter. Recharge-water, therefore, is a principal vehicle for leaching and transporting solid or liquid pollutants to the water table. The greater the recharge, the greater the potential for ground water pollution. This general statement is true until the amount of recharge is great enough to cause dilution of the pollutant, at which point the ground water pollution potential ceases to increase and may actually decrease. This phenomena has been acknowledged but the ranges and associated ratings do not reflect the dilution factor. Aguifer Media Aquifer media refers to the consolidated or unconsolidated material which serves as an aquifer (such as sand and gravel or limestone). An aquifer is defined as a subsurface rock unit which will yield sufficient quantities of water for use. Water is contained in aquifers within the pore spaces of granular and clastic rock and in the fractures and solution openings of non-clastic and non- granular rock. The media that water must flow through is an important control (along with hydraulic conductivity and gradient) in determining the time available for attenuation processes such as sorption, reactivity, and dispersion to occur. The aquifer medium also influences the amount of effective surface area of materials with which the pollutant may come in contact within the aquifer. In general, the larger the grain size and the more fractures or openings within the aquifer, the higher the permeability and the lower the attenuation capacity of the aquifer media. Soil Media Soil media refers to that uppermost portion of the vadose zone characterized by significant biological activity. Soil is commonly considered the upper weathered zone of the earth which averages a depth of six feet or less from the ground surface. Soil has a significant impact on the amount of recharge which can infiltrate into the ground and, hence, on the ability of a pollutant to move 7 vertically into the vadose zone. The presence of fine-textured materials sucn as silts and clays can decrease relative soil permeabilities and restrict pollutant migration. Moreover, where the soil zone is fairly thick, the attenuation processes.of filtration, biodegradation, sorption, and volatilization may be quite significant. Thus, for certain land surface practices, such as agricultural applications of pesticides, soil may have the primary influence on pollution potential. In general, the pollution potential of a soil is largely affected by the type of clay present, the shrink/swell potential of that clay, and the grai n si ze of the soi 1 . In general , the 1 ess the cl ay shri nks and swel 1 s and the smaller the grain size, the less the pollution potential. The quantity of organic material present in the soil may also be an important factor particularly in the attenuation of pesticides. Organic matter is typically contained in the surface layer of the soil and composed of undecayed plant and animal tissue, charcoal, and" various humic compounds. The organic content of the soil generally decreases with depth from the surface. Topography As used here, "topography" refers to the slope and slope variability of the land surface. Topography influences the likelihood that a pollutant will run off or remain on the surface in one area long enough to infiltrate. Slopes which provide a greater opportunity for pollutants to infiltrate will be associated with a higher ground water pollution potential. Topography influences soil development and therefore has an effect on pollutant attenuation. Topography is also significant because gradient and direction of flow often can be inferred for water table conditions from the general slope of the land. Typically, steeper slopes signify higher ground water velocity. Impact of the Vadose Zone The vadose zone is defined as that zone above the water table which is unsaturated or discontinuously saturated. The type of vadose zone media determines the attenuation characteristics of the material below the typical soil horizon and above the water table. The media also controls the path length and routing, thus affecting the time available for attenuation and the quantity of material encountered. Hydraulic Conductivit Hydraulic conductivity refers to the ability of the aquifer materials to transmit water, which in turn, controls the rate at which ground water will flow under a given hydraulic gradient. The rate at which the ground water flows also controls the rate at which a pollutant moves away from the point at which it enters the aquifer. Hydraulic conductivity is controlled by the amount and interconnection of void spaces within the aquifer which may occur as a consequence of intergranular porosity, fracturing, and bedding planes. For purposes of this model, hydraulic conductivity is divided into ranges where high hydraulic conductivities are associated with higher pollution potential. 8 The DRASTIC Parameters From the discussions on the DRASTIC parameter, it is apparent that there is overlap between the various parameters. The depth to the water, for example, affects the quantity of material that will be encountered by a pollutant moving downward toward an aquifer. The thicker the vadose zone in a given setting, the greater the effect may be upon the degradation, retardation, or attenuation of the pollutant. However, in considering the impact of the vadose zone, degradation, retardation, and other significant attenuation processes are all varied according to the nature of the materials present and their condition within the vadose zone. If, for instance, the vadose zone is moderately fractured granite, the materials within the vadose zone will have only a slight impact on most pollutants entering the vadose zone. The protection provided will be a function of depth and the failure of critical fractures to interconnect. If, however, the vadose zone is comprised of unfractured glacial till, it can be anticipated that consumptive sorption will be moderately high; infiltration will be moderately low; retardation will be significant; and with any substantial thickness of till , considerable time will be required for most pollutants to penetrate the till. Thus it can be seen that the overlapping consideration of degradation, retardation, and attenuation within the context of both depth to water and impact of the vadose zone is useful in the comparative evaluation of sites. Net recharge determines, on an annual basis, the quantity of water from precipitation that is available for vertical transport, dispersion, and dilution of a pollutant from a specific point of application. Net recharge exemplifies how some parameters can have both positive and negative effects. For example, greater recharge typically means more rapid transport of a pollutant and therefore less time for attenuation. However, in this situation, dilution is also greater, thereby exerting a positive influence because the concentration of an introduced pollutant will be lessened. It is also evident that a thick unsaturated zone, with a layered sequence of bedded and fractured shales, sandstones, and limestones, can have a profound impact on all three of the same factors (transport, dispersion, dilution) that are of primary importance to net recharge. Topography and soil media also influence net recharge. Topography has site- specific influence which determines whether the capacity for recharge is high or low at a given point. The permeability of the surface soils has a similar impact. However, the nature of the surface soil materials has an additional impact upon potential pollutant attenuation, consumptive sorption, route length and direction, and time available for penetration. In addition to its direct influence upon recharge, topography exerts a significant influence upon soil thickness, drainage characteristics, and profile development. For example, in high slope areas, wind and rain are more likely to erode the soil surface, diminishing the soil thickness. High slopes also result in faster runoff, allowing less time for infiltration to occur. In addition, topography usually bears a predictable relationship to hydraulic gradient, and 9 direction of probable pollutant movement under water table conditions, with a consequent impact on dispersion and dilution. The upper portion of the vadose zone exerts influence on the type of soils developed on the surface. The vulnerability of an aquifer to a given pollution event varies in response to the nature of the materials in the vadose zone including but not limited to: grain size, sorting, reactivity, bedding, fracturing, thickness, and sorptive character. In general, finer grain-size materials, i.e., clays and silt, have lower hydraulic conductivity and greater capacity for the temporary and long-term attenuation of pollutants. if expandable clay minerals are present, the sorptive capacity is further enhanced. If a material is even moderately cemented, then grain size and sorting may be less s.ignificant than the degree of cementation. If the material in the vadose zone is reactive to the pollutant, or soluble in it, then there may be two different effects. First, the pollutant may be retarded (a positive effect) or second, the solution of the vadose zone material may actually increase permeability and allow subsequent introduction of pollutants to pass through more quickly with less retardation (a negative effect). In the case of reactive pollutants, the importance of secondary by- products must be considered. It is here that the risks associated with gaseous phase transport are most likely to have an impact on ground water. The thickness of the vadose zone and the degree of fracturing and frequency of bedding planes in the vadose zone all impact upon the tortuosity, route length, dispersion, and consequent travel time that is required for a pollutant to move through the vadose zone. This is not only of time-delay importance but also is important as the control of contact time for reactions to occur. The vadose zone, including the surficial soil, is also of great importance as the zone where most of the biologic activity occurs. There are natural organisms found in this zone that break down many polluting substances into secondary by-products, both harmless and harmful. For many chemicals, these reactions are very poorly understood, if at all, but it is known that with sufficient time, the eventual results are generally beneficial. Among the best known of these processes at present are the bacterial fixation of iron and the bacterial breakdown of non-chlorinated hydrocarbons under natural conditions. Both of these processes occur in the vadose zone and in the aerobic portion of shallow aquifers. The hydraulic conductivity, with the gradient of the aquifer beneath a site, influences the rate of movement of an introduced pollutant away from the point of introduction. In conjunction with hydraulic gradient, conductivity also controls the direction of movement. These are, in turn, affected with regard to dispersion, by grain size, bedding, fracturing, and tortuosity. DRASTIC RANKING SYSTEM A numeric ranking system to assess ground water pollution potential has been devised using the DRASTIC factors. The system contains three significant parts: weights, ranges, and ratings. 10 i7-71 I @"- Each DRASTIC factor has been evaluated with respect to the other factors to balance the relative importance of each factor in determining an area's susceptibility to ground water pollution,. Each DRASTIC factor has been assigned a relative weight ranging from 1 to 5 as. shown in Table 1. Those DRASTIC factors with a weight of 5 have the greatest impact on whether or not an area is susceptible to ground water contamination. Those with a weight of 1 have the least impact. Table 1. Assigned Weights for DRASTIC Features Feature Weight Depth to Water (D) 5 Net Recharge (R) 4 Aquifer Media (A) 3 Soil Media (S) 2 Topog aphy (T) I Impact of the Vadose Zone Media (1) 5 Hydraulic Conductivity of the Aquif2L_LC) 3 Each DRASTIC factor has been divided into the appropriate ranges or significant media type and then assigned a rating. The rating is based on the relative pollution potential impact of the range or media type given the factor being evaluated. The range for each DRASTIC factor has been assigned a rating which varies between 1 and 10 (Tables 2 - 8). The higher the rating, the higher the factor's contribution to the pollution potential. This information was not modified from the recommendations in the DRASTIC handbook. This system allows the determination of a numeric value for an area by using an additive model. This number provides a representative value of the relative potential susceptibility to pollution of an area. The equation for determining the DRASTIC Index is: PAW +RRRJ + M., + SRSW + TRTW + IR1W + CA =Pollution Potential where: R rating W- weight The DRASTIC model was used to evaluate ground water pollution potential on a grid cell basis. The County was divided into 557 grid cells with a unit length of 3,500 feet (grid cell area = 281 acres). Ratings were determined for each hydrogeologic parameter for each grid cell. The DRASTIC Index was then computed using the aforementioned equation in an overlay scheme as shown in Figure 2. Once a DRASTIC Index has been computed, it is possible to identify areas which are relatively more likely to be susceptible to ground water contamination. The higher the DRASTIC Index, the greater the ground water pollution potential. The DRASTIC Index provides only a relative evaluation tool and is not designed to provide absolute answers such as pollutant loadings to aquifers and resulting ground water pollutant concentrations. Table 2. Ranges and Ratings for Depth to Water Weight: 5 Depth to Water ("D") Range (feIet) Rating 0 5 10 5 15 9 15 30 7 30 50 5 50 75 3 75 - 100 2 100+ 1 12 Variable Weight GridCell 3 Rating Codes 2 Z 5 '1101, 3 -"' 6--,7' 3 9 A 3 @,@ @6@6 Z"-- 2 @1 S 2 @5@3 5 ,"- @6@6 @4@2 C 3 DRAST7C Index Figure 2 DRASTIC Overlay Scheme 13 NII Tabl e 3. Ranges and Ratings for Net Recharge Weight: 4 Net Recharge ( IIRII) (inches/year) ange Rating 0 2 1 2 4 3 4 7 6 7 10 8 10+ 9 Table 4. Ranges and Ratings for Aquifer Media Weight: 3 Aquifer Media ("A") Range Rating Typical Rating- Massive Shale I - 3 2 Metamorphic/Igneous 2 - 5 3 Weathered Metamorphic/Igneous 3 - 5 4 Glacial Till 4 - 6 5 Bedded Sandstone, Limestone and 5 - 9 6 Shale Sequences Massive Sandstone 4 - 9 6 Massive Limestone 4 - 9 6 Sand and Gravel 4 - 9 8 Basalt 2 - 10 9 Karst Limestone 9 - 10 10 14 Tabl e 5. Ranges and Ratings for Soil Media Weight: 2 Soil Media ("S") Range Rating Thin or Absent 10 Gravel 10 Sand 9 Peat 8 Shrinking and/or.Aggregated Clay 7 Sandy Loam 6 Loam 5 Silty Loam 4 Clay Loam 3 Muck 2 Nonshrinking and Nonaggregated Clay I Table 6. Ranges and Ratings for Topography Weight: 1 Topography ("T") (Percent Slope) Range T Rating 0 2 10 2 6 9 6 12 5 12 18 3 18+ 1 15 Tabl e 7. Ranges and Ratings for Impact of the Vadose Zone Media Weight: 5 Impact of the Vadose Zone Media ("I") Range Rating Range Typical Rating Confining Layer 2 1 Silt/Cl,ay 2 - 6 3 Shale 2 - 5 3 Limestone 2 - 7 6 Sandstone 4 - 8 6 Bedded Limestone, Sandstone, Shale 4 - 8 6 Sand and Gravel with Significant 4 - 8 6 Silt and Clay Metamorphic/Igneous 2 - 8 4 Sand and Gravel 6 - 9 8 Basalt 2 - 10 9 Karst Limestone 8 - 10 10 Table 8. Ranges and Ratings for Hydraulic Conductivity Weight: 3 Hydraulic Conductivity ("C") (GpD/ft2) Range Rating 1 100 1 100 300 2 300 700 4 700 1000 6 1000 2000 8 2000+ 10 16 DRASTIC MODEL DRASTIC was developed using four major assumptions: 1. the pollutant is introduced at the ground surface; 2. the pollutant is flushed into the ground water by precipitation; 3. the pollutant has the mobility of water; and 4. the area evaluated using DRASTIC is 100 acres or larger. In evaluating specific project impacts, there may be special conditions which would need to be more fully evaluated. For example, the methodology assumes that a pollutant will start at the surface, enter the soil, travel through the vadose zone, and enter the aquifer much like water. However, a pollutant may have unique chemical and physical properties which would restrict movement into ground water-. A pollutant may be denser than water and exhibit travel characteristics different from water. Further, a disposal method which injects pollutants directly into ground water negates many of the natural attenuation mechanisms assumed in the methodology. In this particular case, DRASTIC does not provide an accurate assessment of ground water pollution potential. In assuming areas of 100 acres or larger, the DRASTIC method attempts to evaluate ground water pollution potential from an area-wide perspective rather than a site-specific focus. For example, in an area of fractured rock, ground water flows in a general direction. However, ground water flow at any one site will be directly controlled by fracture orientation. In this scenario, exact direction of pollutant movement is controlled by a site-specific characteristic. Generally, however, the pollutant would still flow in a general direction. 17 SECTION 4 DATA COLLECTION AND RATING DEVELOPMENT This section describes the data collection activities, interpretations, and assumptions used in developing DRASTIC parameter ratings. Relevant references are cited. The detailed data base is included as Appendix A while maps showing the distribution of DRASTIC parameter ratings are included in Appendix B. DEPTH TO WATER The primary source of data on depth to water is the logs for approximately 1,300 wells within the County. The Virginia Water Control Board (VWCB) has compiled the well logs and entered the data into the EPA STORET data base. This data was downloaded to microcomputer and manipulated in order to develop the rating by grid cell. Powell and Abe (1985) and Meng and Harsh (1988) provided supplemental information on depth to water. A very shallow (0 - 5 feet) depth to water was assumed for wide, flat river and overbank areas. This shallow depth was also assumed for swamps. Much of the Piedmont has a rating of 7 (depth to water of 15 - 30 feet) but the Coastal Plain varies greatly in rating. NET RECHARGE Net recharge information was collected from numerous sources, including Aller, et al . (1987), Hamilton and Larson (1986), Harsh and Laczniak (1990), O'Brien anTGere (1991), Weston (1976), and Wagner, et al . (1988). These references indicate that, in general, net recharge is betweer@-7 and 10 inches per year (rating of 8) in the Piedmont, and over 10 inches per year (rating of 9) in the Coastal Plain. Further refinements were made in the Piedmont, to account for the impact of topography. In high slope areas, water moves faster along the surface, providing less time for infiltration. Also, higher slope areas tend to have larger outcroppings of impermeable solid rock, since weathered material is easily transported away with wind and runoff. A net recharge of 4 - 7 inches per year (rating of 6) was used for areas with slopes between 12 and 18 percent, and a net recharge of 2 - 4 inches per year (rating of 3) was used where slope is greater than or equal to 18 percent. In the Coastal Plain, 'the soil , vadose zone, and aquifer media is predominantly sand and silt, so topography has less impact on recharge- AQUIFER MEDIA VWCB well data, along with Meng and Harsh (1988), were used to delineate the various aquifers within the County. Meng and Harsh (1988) also describe the aquifer media, as do the following references: Commonwealth of Virginia (1963, 1971, and 1980), Mixon, et al. (1989), Mixon and Newell (1977), Mixon (1990), Pavlides (1976 and 1990), Powell and Abe (1985), Weston (1976), and Wagner, et 18 al . (1988). The Piedmont is predominantly weathered granite and gneiss, which correspond to the weathered metamorphic/igneous DRASTIC range (rating of 4). Fresh unweathered rack is exposed in high slope areas (assumed to be greater than or equal to 12 percent), corresponding to the metamorphic/igneous DRASTIC range (rating of 3). The Coastal Plain is predominantly sand and gravel. A rating of 8 was applied to.the Potomac Aquifer, and 7 to the Aquia and Chickahominy/Piney Point aquifers. This difference in ratings accounts for the higher attenuation (lower hydraulic conductivity) in the Potomac, which could be caused by the size and orientation of clay lenses in the sand and gravel. SOIL MEDIA Soil characteristics were derived from the County Soil Survey (Isgrig and Strobel, 1974). Representative cores were reported for the various soil classifications. These cores were, in turn, used to develop DRASTIC ranges. The Coastal Plain soil media is sandy loam (rating of 6), and the sandy loam stretches into a small section of the southeastern Piedmont. The majority of the Piedmont has a clay loam (rating of 3) soil media. The soil media was assumed to be thin or absent (rating of 10) in high slope areas (slopes greater than or equal to 12 percent). This is consistent with the Soil Survey and is a reasonable assumption because soils erode to a far greater extent in high slope areas where they are carried away by runoff and wind. TOPOGRAPHY Percent slope was determined by evaluating the Stafford County topographic map (U.S. Geological Survey, 1974). Steep slopes form the flood boundary for parts of Aquia Creek, Accokeek Creek, Potomac Creek, Long Branch, and the Rappahannock River. Extremely flat areas can also be found, particularly in some river overbank areas and around Widewater Beach. IMPACT OF THE VADOSE ZONE MEDIA A number of resources were used to derive the vadose zone media in the Piedmont, including Aller, et al. (1987), Mixon (1990), Pavlides (1976), Powell and Abe (1985), and Wagner, et al. (1988). The vadose zone media in the Piedmont is predominantly sand and gravel with significant silt and clay (rating of 5). In high slope areas (where slope is greater than or equal to 12 percent), the vadose zone media is assumed to be metamorphic/igneous (rating of 4) since high erosion leaves exposed bedrock. The vadose zone media in the Coastal Plain was derived from Aller, et al. (1987), Meng and Harsh (1988), and Weston (1976). The vadose zone in the Coastal Plain is also sand and gravel with significant silt and clay, although there is far more sand in the Coastal Plain vadose zone than in the Piedmont. A rating of 7 was used for the Potomac Aquifer, and a rating of 6 was used for the Aquia and Chickahominy/Piney Point Aquifers. As with the aquifer media rating, this difference accounts for the higher attenuation (lower hydraulic conductivity) in the Potomac, which could be caused by the size and orientation of clay lenses in the vadose zone. 19 HYDRAULIC.CONDUCTIVITY Hydraulic conductivity was derived from Harsh and Laczniak (1990) and Hamilton and Larson (1986). Hydraulic conductivity in the Piedmont is approximately 50 gallons per day per square foot (gpd/ ft2), corresponding to a rating of 1. In the Coastal Plain, 2 the Aquia Aquifer has a hydraulic conductivity of approximately 110 gpd/ft (rating of 2), the Chickahominy/Piney Point Aquifer has a hydraulic conductivity of approximately 90 gpd/ ft2 (rating of 1), and the Potomac Aquifer has a hydraulic conductivity of approximately 400 gpd/ ft2 (rating of 4). These values are not site-specific since conductivity can vary substantially within any of the aquifers present. Rather, these values are typical of the aquifers and are derived from very limited well pump tests and modeling studies. 20 SECTION 5 RESULTS STUDY SUNNARY The ratings discussed in Section 4 form the basis for the composite DRASTIC index. The sum over the seven DRASTIC parameters of the product of the rating and the weight determine the index value as described in Section 2. These values were determined for each of the grid cells, as shown in Figure 8, and range from 90 to 179. In the Piedmont, the DRASTIC Index values generally range from 100 to 130, while in the Coastal Plain, values range from 130 to 179. The fall line separates the two regions and is easily distinguished by the sharp break in DRASTIC values between the Piedmont and the Coastal Plain. The Coastal Plain has higher composite DRASTIC values, which is associated with greater pollution potential, because the sand and gravel in the soil, vadose zone, and aquifer media facilitate chemical transport as opposed to the metamorphic/igneous formations of the Piedmont. Within the Coastal Plain, the DRASTIC Index values are generally lower in the Aquia and Chickahominy/Piney Point Aquifers than in the Potomac Aquifer because of the increased attenuation provided by the aquifer and vadose zone media in these two aquifers. These results match very well with general DRASTIC ratings developed in the Prince William County study (Wagner, et al ., 1988) of 111 to 119 in the Piedmont and 127 to 182 in the Coastal Plain. SPREADSHEETS Spreadsheets were developed to store grid cell data and determine ratings. The spreadsheets are presented in Appendix A. The first two columns specify the Virginia grid location of the center of each grid cell . The third and fourth columns specify the depth to ground water and corresponding D rating for the grid cell , respectively. The regional aquifer system - Piedmont (P) or Coastal Plain (C) - is included in col.umn five. Column six specifies the net recharge rating, R. Column seven includes the specific aquifer - Piedmont, or, within the Coastal Plain, the Aquia, Chickahominy/Piney Point (CH/P), or Potomac Aquifer. The aquifer media rating, A, and the soil media rating, S, are specified in columns eight and nine, respectively. The mean percent slope and corresponding topography rating, T, are included in columns ten and eleven, respectively. The impact of the vadose zone media rating, 1, is specified in column twelve. The hydraulic conductivity (gpd/ft2 ) and corresponding rating, C, are specified in columns thirteen and fourteen, respectively. The final column presents the composite DRASTIC Index for the individual grid cells. SURFER SURFER (Golden Software, Inc., 1987) is a powerful software tool which can create two- and three-dimensional graphics. SURFER was used to assist in 21 interpreting data collected for this project. Much of the well data downloaded from the EPA STORET data base were mapped in various ways to assist in data collection. SURFER was used to map the locations of the wells and the observations (such as depth to water) at the wells. SURFER was also used to create surface (topographic) maps of depth to water to assist in data interpolation. The figures presented in Appendix B were created with SURFER, and are examples of mapping observations (ratings) at sampling locations (grid cells). Engineering judgment and literature review, along with the graphics created with SURFER, contributed to the development of the spreadsheets previously described. MAPPING DRASTIC RESULTS The following presents the methodology for preparing the Ground Water Pollution Potential Map of Stafford County. The DRASTIC Index values were grouped into 3 ranges: less than 125; 125 to 149; and 150 and greater. These three ranges co 'rrespond to low, moderate, and high relative ground water pollution potential, respectively. Three ranges were chosen to enhance the map's utility as a general policy tool for ground water protection. Each of these ranges has an associated shading pattern. The grid cells were shaded according to the range within which their associated index values fall. Shading boundaries were smoothed 'to more accurately and aesthetically present the physical situation. The County boundary was also mapped. The index values themselves are not included on the map since the shading indicates a general range. The reason these values are not mapped is that the methodology is qualitative; quantitative comparisons of index values can lead to misapplication of results. Grid cell tick marks and the corresponding Virginia grid location are included on the four sides of the map, which was drafted on reproducible mylar. The map was created on a 1:36,000 scale, which directly overlays on the Stafford County planning maps. 22 SECTION 6 GROUND WATER RESOURCE PROTECTION OVERLAY AREAS The goal of this Ground Water Resource Protection Program is to identify the relative ground water pollution potential of land areas throughout the County and to provide guidelines for protecting ground water quality as development occurs. In order for the County to protect the quantity and quality of its ground water resources, an overlay scheme is proposed. The purpose of the overlay is not to place undo restrictions on future development, but rather to support land use decision making by focusing. data gathering and analysis efforts in those regions which are potentially most susceptible to ground water contamination. A further objective is to collect well data countywide to support the evaluation of ground water resources as a possible supplement in responding to projected water supply shortfalls. Through the application of the DRASTIC methodology, ground water pollution potential has been evaluated throughout the County. The resulting pollution potential (DRASTIC) index values have been grouped into three categories which correspond to areas of low, moderate, and high susceptibility to ground water pollution. These categories form the basis for the ground water protection overlay guidelines. The guidelines detailed below account for the ground water contamination risks associated with certain land uses and how these risks must be managed according to the ground water pollution potential of a given area. However, developments should analyze their impact relative to each individual DRASTIC parameter as well as implementing strategies that address the overall recommendations of the appropriate overlay area. GUIDELINES FOR LOW GROUND WATER POLLUTION POTENTIAL AREAS Those areas identified as being the least susceptible to ground water pollution are generally located west of 1-95 in the Piedmont Physiographic Region and impacting the Piedmont Aquifer. The depth to water is generally greater than 15 feet with a net recharge of 7-10 inches per year. The aquifer media is generally weathered metamorphic and igneous rock with the predominant soil media being clay and sandy loam. These soil types relate to a low hydraulic conductivity as they do not have a great ability to transmit water to the water table. However, some isolated gravel areas are present that would be capable of effectively transmitting water to the water table. The percent slope varies greatly throughout this overlay area. The guidelines for areas of low susceptibility to ground water pollution are as follows: Discourage the location of landfills and dumps unless they are developed in such a manner as to ensure the protection of ground water resources. 23 Discourage the location of industrial waste disposal sites. Encourage the replacement of older underground storage tanks in a manner and timeliness that is not detrimental to the economic potential of small business owners. Recommend mining operations utilize stormwater Best Management Practices (BMPs) to prevent ground water degradation. Recommend that the storage of petroleum, fertilizer, pesticide, and other toxic substances occur only in containers specifically designed and maintained for these activities. Provide educational opportunities for the storage and application of pesticides, fertilizers, and other toxic materials for agricultural, commercial, industrial, and golf course use. Establish a well- monitoring program to collect data from community residential wells and commercial and industrial wells on the following parameters: average yield, elevation of water table, and monitoring results for: silica, iron, manganese, calcium, magnesium, sodium, potassium, bicarbonate, sulphate, chloride, fluoride, nitrate, total dissolved solids, specific conductance (micromhos), pH, fecal coliform bacteria, hardness as CaC03; for new wells, include the following parameters: static water level (unpumped level -measured), stabilized measured pumping water level, stabilized yield, time to stabilized yield, water zones. for commercial and industrial wells, include pollutants associated with the particular land use. GUIDELINES FOR MODERATE GROUND WATER POLLUTION POTENTIAL AREAS Those areas identified as being moderately susceptible to ground water pollution are generally located in the central and southeastern portions of the County in the Coastal Plain Physiographic Region and impacting the Aquia and @Chickahominy/Piney Point Aquifers. The depth to water is greater than 15 feet with a net recharge of greater than 10 inches per year. The aquifer media is generally sand and gravel with soils varying from sandy loams to gravel. In general, these soil types will transmit water at a higher rate (moderate hydraulic conductivity) than the areas of low pollution potential. The percent slope varies greatly throughout the overlay area. Additional guidelines are recommended for areas of moderate ground water pollution potential as follows: 24 All guidelines listed under low pollution potential areas. Encourage the use and continued maintenance of BMPs for all land uses designed in such a manner so that outlets are not directing infiltration at points were ground water contamination could occur. Prevent runoff from impervious areas to be directed at points where ground water contamination could occur. Provide vegetated buffers for runoff from impervious. Encourage clustering of developments with the preservation of large undisturbed open areas. Preserve existing vegetation during site development to increase the filtration of pollutants prior to water entering the soil. Regulate the concentration of animals in order to provide additional filtration of nutrient-rich runoff that may degrade ground water quality. Encourage developments to disturb only the area necessary for the desired use and limit the amount of runoff from the site. Improve land management practices which encourage the use of alternative materials, including the use of non-toxic materials, that support infiltration on the developed site in the appropriate area. Encourage public sewer connections for all land uses except: recreational (active and passive); agricultural; low intensity commercial (local markets) and industrial (warehouse); and low density residential (>1 acre lots). Encourage the continued periodic maintenance of individual sewage disposal systems to provide for maximum treatment of wastewater. Design public sewage treatment systems using best available technology that provides for maximum treatment of wastewater. Provide educational opportunities for the storage and application of pesticides, fertilizers, and other toxic materials for all land uses. GUIDELINES FOR HIGH GROUND WATER POLLUTION POTENTIAL AREAS Those areas identified as being the most susceptible to ground water pollution are generally located along the fall line. -The band of land area runs parallel to and inclusive of 1-95 and Jefferson Davis Highway (US-1) through the County. In addition, the land area which would include the Aquia Harbor subdivision and the entire Widewater area from 1-95 to the peninsula is 25 171 identified as a high ground water pollution potential area. This area generally relates to the Coastal Plain Physiographic Region impacting the Potomac Aquifer. The depth to water varies ranging from less than 5 feet to 30 feet with a net recharge of greater than 10 inches per year. The aquifer media is sand and gravel. This soil type relates to a high hydraulic conductivity which provides for rapid transmission of water (and thus pollutants) to the water table. The percent slope varies throughout the overlay area. Additional guidelines are recommended for areas of high ground water pollution potential as follows: - All guidelines listed in the low and moderate polluti on potential areas. - Discourage the establishment of automobile junkyards and salvage operations. Discourage the establishment of quarries, gravel pits, and other surface mining operations. - Discourage the development of landfills and dumps. - Discourage the establishment of confined feedlots for livestock. - Develop more stringent controls for wastewater spray irrigation operations. - Develop more stringent controls for underground and above ground storage of petroleum, pesticide, fertilizer, and other toxic materials. - Encourage public sewer connections for all land uses except: recreational (active and passive); agricultural ; and very low density residential (>3 acre lots). 26 GLOSSARY Aquifer - A waterbearing stratum of rock, sand, or gravel that has the property of transmission. Attenuate - To reduce the severity of (concentration and/or volume of pollutant, in this case). Clastic - Made of fragments of pre-existing rocks. Dilution - The action of diminishing in concentration. Dispersion - The process of dissipating. Hydraulic Conductivity - The ability of the aquifer materials to transmit water. Igneous - Rock formed by the solidification of molten magma. Metamorphic Rock which has been changed by pressure, heat, and water, resulting in a more compact and more highly crystalline condition. Net Recharge The amount of precipitation which infiltrates through to the water table. Tortuous - Marked by repeated twists, bends, or turns. Vadose Zone The zone above the water table which is saturated or discontinuously saturated. 27 REFERENCES 1. Al 1 er, Li nda, et al ., 1987. DRASTIC: A Standardi zed System for Eval uati ng Ground Water P-ollution Potential Using Hydrogeologic Settings. EPA/600/2- 87/035. 2. Commonwealth of Virginia, 1963. Geologic Map of Virginia, Division of Mineral Resources. 3. Commonwealth of Virginia, 1971. Mineral Resources of Virginia, Division of Mineral Resources. 4. Commonwealth of Virginia, 1980. Geology of Oak Grove Core, Division of Mineral Resources. 5. Commonwealth of Virginia, 1987 (revised 1990). A Ground Water Protection Strategy for Virginia, State Water Control Board. 6. Golden Software, Inc., 1987, SURFER. 7. Hamilton, Pixie A., and Larson, Jerry D., 1986. Hydrogeology and Analysis of the Ground-water Flow System in the Coastal Plain of Southeastern Virginia, U.S. Geological Survey. 8. Harsh, John F., and Laczniak, Randall J., 1990. Conceptual ization and Analysis of Ground-Water Flow System in the Coastal Plain of Virginia and Adjacent Parts of Maryland and North Carolina. Professional Paper 1404-F, U.S. Geological Survey. 9. Isgrig, Dan, and Stroebel, Jr., Adolph, 1974. Soil Survey of Stafford and King George Counties, Virginia. Soil Conservation Service. 10. Meng, Andrew A., III and Harsh, John F., 1988. Hydrogeologic Framework of the Virginia Coastal Plain. Professional Paper 1404-C, U.S. Geological Survey. 11. Mixon, Robert B., and Newell, Wayne L., 1977. Stafford Fault System: Structures Documenting Cretaceous and Tertiary Deformation along the Fall Line in Northeastern Virginia. Geology. 12. Mixon, Robert B., 1990. Geologic Map of the Coastal Plain Part of the Joplin Quadrangle, Stafford and Prince William-Counties, Virginia. Open File Report 90-550, U.S. Geological Survey. 13. Mixon, Robert B., et al., 1989. Geologic Map and Generalized Cross Sections of the CoasFa_l Tlain and Adjacent Parts of the Piedmont, Virginia. Miscellaneous Investigations Series Map 1-2033, U.S. Geological Survey. 28 14. O'Brien & Gere, 1991. Comprehensive Water Supply Study, Stafford County, Virginia. 15. Pavlides, Louis, 1976. Piedmont Geology of the Fredericksburg, Virginia, Area and Vicinity. U.S. Geological Survey. 16. Pavlides, Louis, 1990. Geology of Part of the Northern Virginia Piedmont. Open File Report 90-548, U.S. Geological Survey. 17. Powell, John D., and Abe, Joseph M., 1985. Availability and Quality of Ground Water in the Piedmont Province of Virginia. Water Resources Investigations Report 85-4235, U.S. Geological Survey. 18. U.S. Geological Survey, 1974. Stafford County, Virginia, County Map Series (Topographic). 19. Wagner, Terry D., et al., 1988. DRASTIC: A Demonstration Mapping Project; Botetourt, Carroll, Henrico, Middlesex, Prince William, and Rockingham Counties, Virginia. 20. Roy F. Weston, 1976. Areawide Waste Treatment Management Plan; Volume IV- Geology and Ground Water Resources.. Rappahannock Area Development Commission. 29 I I I I I I APPENDIX A I DRASTIC DATA BASE I i I I I I i I I 1 30 1 1 STAFFORD COUNTY GROUNDWATER PROTECTION STUDY SOUTH OF VA 269500 OCTOBER 18,1991 REGIONAL A S T I c DRASTIC VA GRID VA GRID AQUIFER RECHARGE MEAN IMP. HYDRAULIC E-W N-S DEPTH SYSTEM RATING AQUIFER SOIL SLOPE VADOSE CONDUCT. ------- ------ - ----- 2317000 213500 45 5 C 9AQUIA ----------- 7-------- 6-------- 9-------- 5-------- 6------ 110 --------2------ 135 2320500 213500 45 5 C 9AQUIA 7 6 1 10 6 110 2 140 2324000 213500 45 5 C 9AQUIA 7 6 4 9 6 110 2 139 2327500 213500 45 5 C 9AQUIA 7 6 4 9 6 110 2 139 2331000 213500 40 5 C 9AQUIA 7 6 9 5 6 110 2 135 2334500 213500 35 5 C 9AQUIA 7 6 4 9 6 110 2 139 2310000 217000 40 5 c 9AQUIA 7 6 4 9 6 110 2 139 2313500 217000 40 5 C 9AQUIA 7 6 1 10 6 110 2 140 2317000 217000 45 5 C 9AQUIA 7 6 1 10 6 110 2 140 2320500 217000 50 5 C 9AQUIA 7 6 1 10 6 110 2 140 2324000 217000 40 5 C 9AQUIA 7 6 4 9 6 110 2 139 2327500 217000 35 5 C 9AQUIA 7 6 1 10 6 110 2 140 2331000 217000 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2334500 217000 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2306500 220500 35 5 C 9AQUIA 7 6 4 9 6 110 2 139 2310000 220500 35 5 C 9AQUIA 7 6 4 9 6 110 2 139 2313500 220500 40 5 C 9AQUIA 7 6 1 10 6 110 2 140 2317000 220500 40 5 C 9AQUIA 7 6 4 9 6 110 2 139 2320500 220500 40 5 c 9AQUIA 7 6 4 9 6 110 2 139 2324000 220500 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2327500 220500 20 7 C 9AQUIA 7 6 4 9 6 110 2 149 2331000 220500 20 7 C 9AQUIA 7 6 4 9 6 110 2 149 2306500 224000 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2310000 224000 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2313500 224000 35 5 C 9AQUIA 7 6 9 5 6 110 2 135 2317000 224000 35 5 C 9AQUIA 7 6 4 9 6 110 2 139 2320500 224000 25 7 C 9AQUIA 7 6 4 9 6 110 2 149 2324000 224000 20 7 C 9CH/P 7 6 4 9 6 90 1 146 2327500 224000 20 7 C 9CH/P 7 6 4 9 6 90 1 146 2331000 224000 20 7 C 9CH/P 7 6 9 5 6 90 1 142 2303000 227500 30 7 C 9POTOMAC 8 6 1 10 7 400 4 164 2306500 227500 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2310000 227500 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2313500 227500 35 5 c 9AQUIA 7 6 9 5 6 110 2 135 2317000 227500 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2320500 227500 30 7 C 9CH/P 7 6 4 9 6 90 1 146 2324000 227500 15 9 C 9CH/P 7 6 4 9 6 90 1 156 2327500 227500 20 7 C 9CH/P 7 6 9 5 6 90 1 142 2331000 227500 20 7 C 9CH/P 7 6 4 9 6 90 1 146 2299500 231000 50 5 C 9POTOMAC 8 6 4 9 7 400 4 153 2303000 231000 60 3 c 9POT014AC 8 6 4 9 7 400 4 143 2306500 231000 40 5 c 9AQUIA 7 6 1 10 6 110 2 140 2310000 231000 45 5 C 9AQUIA 7 6 4 9 6 110 2 139 2313500 231000 40 5 C 9AQUIA 7 6 4 9 6 110 2 139 2317000 231000 30 7 C 9AQUIA 7 6 9 5 6 110 2 145 2320500 231000 25 7 C 9CH/P 7 6 4 9 6 90 1 146 2324000 231000 20 7 c 9CH/P 7 6 4 9 6 90 1 146 2327500 231000 20 7 C 9CH/P 7 6 4 9 6 90 1 146 REGIONAL A S T C DRASTIC VA GRID VA GRID AQUIFER RECHARGE E-W N-S DEPTH MEAN IMP. HYDRAULIC SYSTEM RATING AQUIFER SOIL SLOPE ----------------------------------------------- ---------------------------------------------------------------------------------------- VADOSE CONDUCT. 2331000 231000 40 5C 9 CH/P 7 6 9 5 6 90 1 132 2278500 234500 25 7P 3 PIEDMONT 3 10 18 1 4 50 1 100 2299500 234500 70 3c 9 POTOMAC a 6 9 5 7 400 4 139 2303000 234500 40 5C 9 POTOMAC 8 6 4 9 7 400 4 153 2306500 234500 40 5C 9 AQUIA 7 6 4 9 6 110 2 139 2310000 234500 45 5C 9 AQUIA 7 6 4 9 6 110 2 139 2313500 234500 55 3C 9 AQUIA 7 6 9 5 6 110 2 125 2317000 234500 45 5C 9 AQUIA 7 6 9 5 6 110 2 135 2320500 234500 45 5c 9 CH/P 7 6 4 9 6 90 1 136 2324000 234500 25 7c 9 CH/P 7 6 4 9 6 90 1 146 2327500 234500 25 7c 9 CH/P 7 6 9 5 6 90 1 142 2331000 234500 50 5c 9 CH/P 7 6 9 5 6 90 1 132 2334500 234500 50 5C 9 AQUIA 7 10 15 3 6 110 2 141 2275000 238000 25 7P 3 PIEDMONT 3 10 18 1 4 50 1 100 2278500 238000 25 7P 3 PIEDMONT 3 10 18 1 4 50 1 100 2292500 238000 70 3P 8 PIEDMONT 4 6 9 5 5 50 1 104 2296000 238000 70 3c 9 POTOMAC 8 6 4 9 7 400 4 143 2299500 238000 50 5C 9 POT014AC 8 6 1 10 7 400 4 154 2303000 238000 35 5C 9 POTOMAC 8 6 9 5 7 400 4 149 2306500 238000 35 5C 9 AQUIA 7 6 4 9 6 110 2 139 2310000 238000 35 5C 9 AQUIA 7 6 4 9 6 110 2 139 2313500 238000 45 5C 9 AQUIA 7 6 4 9 6 110 2 139 2317000 238000 40 5c 9 cm/P 7 6 4 9 6 90 1 136 2320500 238000 25 7C 9 CH/P 7 6 4 9 6 90 1 146 2324000 238000 15 9C 9 CH/P 7 6 9 5 6 90 1 152 2327500 238000 25 7c 9 CH/P 7 10 15 3 6 90 1 148 2331000 238000 35 5C 9 AQUIA 7 10 15 3 6 110 2 141 2334500 238000 50 5C 9 AQUIA 7 10 15 3 6 110 2 141 2271500 241500 25 7P 8 PIEDMONT 4 6 9 5 5 50 1 124 2275000 241500 25 7P 8 PIEDMONT 4 6 9 5 5 50 1 124 2278500 241500 25 7P 8 PIEDMONT 4 6 9 5 5 50 1 -124 2282000 241500 25 7P 3 PIEDMONT 3 10 18 1 4 50 1 100 2285500 241500 30 7P 6 PIEDMONT 3 10 15 3 4 50 1 114 2289000 241500 45 5P 8 PIEDMONT 4 6 9 5 5 50 1 114 2292500 241500 65 3P 8 PIEDMONT 4 6 4 9 -5 50 1 108 2296000 241500 35 5C 9 POTOMAC 8 6 9 5 7 400 4 149 2299500 241500 25 7C 9 POTOMAC 8 6 9 5 7 400 4 159 2303000 241500 25 7C 9 POTOMAC 8 6 4 9 7 400 4 163 2306500 241500 35 5C 9 AQUIA 7 6 4 9 6 110 2 139 2310000 241500 45 5c 9 AQUIA 7 6 4 9 6 110 2 139 2313500 241500 45 5c 9 AQUIA 7 6 4 9 6 110 2 139 2317000 241500 45 5C 9 CH/P 7 6 4 9 6 90 1 136 2320500 241500 25 7C 9 CH/P 7 6 9 5 6 90 1 142 2324000 241500 35 5C 9 CH/P 7 10 15 3 6 90 1 138 2327500 241500 30 7C 9 CH/P 7 10 15 3 6 90 1 148 2331000 241500 25 7C 9 AGUIA 7 10 15 3 6 110 2 151 2334500 241500 55 3C 9 AQUIA 7 10 18 1 6 110 2 129 2257500 245000 35 5P 6 PIEDMONT 3 10 15 3 4 50 1 104 2261000 245000 35 5P 6 PIEDMONT 3 10 15 3 4 50 1 104 2268000 245000 35 5P 8 PIEDMONT 4 6 9 5 5 50 1 1% 2271500 245000 35 5P 6 PIEDMONT 3 10 15 3 4 50 1 104 D REGIONAL R A S T C DRASTIC VA GRID VA GRID AQUIFER RECHARGE MEAN IMP. HYDRAULIC E-W N-S DEPTH SYSTEM RATING AQUIFER SOIL SLOPE VADOSE CONDUCT. ---------------------------------- ---------------------------------------------------------------------------------------------------- 2275000 245000 25 7 P 8 PIEDMONT 4 6 4 9 5 50 1 128 2278500 245000 25 7 p 8 PIEDMONT 4 6 9 5 5 50 1 124 2282000 245000 25 7 P, 8 PIEDMONT 4 6 9 5 5 50 1 124 2285500 245000 20 7 p 8 PIEDMONT 4 6 9 5 5 50 1 124 2289000 245000 25 7 p 8 PIEDMONT 4 6 4 9 5 50 1 128 2292500 245000 60 3 P 8 PIEDMONT 4 6 4 9 5 50 1 108 2296000 245000 so 5 c 9 POTOMAC 8 10 15 3 7 400 4 155 2299500 245000 40 5 c 9 POTOMAC 8 6 9 5 7 400 4 149 2303000 245000 25 7 c 9 POTOMAC 8 6 9 5 7 400 4 159 2306500 245000 30 7 c 9 AQUIA 7 6 4 9 6 110 2 149 2310000 245000 50 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2313500 245000 60 3 c 9 AQUIA 7 6 9 5 6 110 2 125 2317000 245000 40 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2320500 245000 30 7 C 9 CH/P 7 10 is 3 6 90 1 148 2324000 245000 40 5 C 9 CH/P 7 10 15 3 6 90 1 138 2327500 245000 25 7 c 9 CH/P 7 10 15 3 6 90 1 148 2331000 245000 25 7 c 9 AQUIA 7 10 15 3 6 110 2 151 2334500 245000 30 7 C 9 AQUIA 7 10 15 3 6 110 2 151 2257500 248500 25 7 P 6 PIEDMONT 3 10 15 3 4 so 1 114 2261000 248500 30 7 P 6 PIEDMONT 3 10 15 3 4 2264500 248500 35 50 1 114 5 p 8 PIEDMONT 4 3 4 9 5 50 1 112 2268000 248500 40 5 p 6 PIEDMONT 3 10 15 3 4 50 1 104 2271500 248500 45 5 p 6 PIEDMONT 3 10 15 3 4 50 1 104 2275000 248500 30 7 p 8 PIEDMONT 4 6 9 5 5 50 1 124 2278500 248500 25 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 2282000 248500 25 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 2285500 248500 15 9 p 8 PIEDMONT 4 6 4 9 5 50 1 138 2289000 248500 20 7 P 8 PIEDMONT 4 6 1 10 5 50 1 129 2292500 248500 45 5 P 8 PIEDMONT 4 6 9 5 5 50 1 114 2296000 248500 45 5 P 8 PIEDMONT 4 6 9 5 5 50 1 114 2299500 248500 so 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2303000 248500 35 5 c 9 POTOMAC 8 6 9 5 7 400 4 149 2306500 248500 35 5 c 9 AQUIA 7 10 15 3 6 110 2 141 2310000 248500 35 5 c 9 AQUIA 7 10 15 3 6 110 2 141 2313500 248500 25 7 C 9 AQUIA 7 10 15 3 6 110 2 151 2317000 248500 25 7 C 9 AQUIA 7 10 15 3 6 110 2 151 2320500 248500 25 7 c 9 CH/P 7 10 15 3 6 90 1 148 2324000 248500 25 7 c 9 CH/P 7 6 4 9 6 90 1 146 2327500 248500 25 7 c 9 CH/P 7 6 1 10 6 90 1 147 2331000 248500 25 7 C 9 AQUIA 7 6 1 10 6 110 2 150 2334500 248500 25 7 C 9 AQUIA 7 6 1 10 6 110 2 150 2257500 252000 25 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2261000 252000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2264500 252000 35 5 P 6 PIEDMONT 3 10 15 3 4 50 1 104 2268000 252000 35 15 P 6 PIEDMONT 3 10 15 3 4 50 1 104 2271500 252000 35 5 P 8 PIED14ONT 4 6 9 5 5 50 1 1% 2275000 252000 35 5 P 8 PIEDMONT 4 6 9 5 5 50 1 114 2278500 252000 20 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 2282000 252000 15 9 P 8 PIEDMONT 4 6 9 5 5 50 1 134 2285500 252000 15 9 P 8 PIEDMONT 4 6 4 9 5 50 1 138 2289000 252000 25 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 REGIONAL A S T C DRASTIC VA GRID VA GRID AQUI FER RECHARGE E-W N-S DEPTH SYSTEM RATING AQUIFER MEAN IMP. HYDRAULIC ------------------------------ SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------------------------------------------------------- 2292500 252000 25 7 P 8PIEDMONT 4 6 4 9 5 50 1 128 2296000 252000 25 7 P 8PIEDMONT 4 6 4 9 5 50 1 128 2299500 252000 35 5 C 9POTOMAC a 6 9 5 7 400 4 149 2303000 252000 30 7 C 9POTOMAC 8 6 9 5 7 400 4 159 2306500 252000 35 5 C 9AQUIA 7 6 9 5 6 110 2 135 2310000 252000 40 5 C 9AQUIA 7 10 15 3 6 110 2 141 2313500 252000 50 5 C 9AQUIA 7 6 4 9 6 110 2 139 2317000 252000 5 10 C 9AQUIA 7 6 1 10 6 110 2 165 2320500 252000 5 10 c 9CH/P 7 6 1 10 6 90 1- 162 2324000 252000 5 10 c 9CH/P 7 6 9 5 6 90 1 157 2327500 252000 30 7 C 9CH/P 7 10 18 1 6 90 1 146 2331000 252000 30 7 C 9AQUIA 7 10 18 1 6 110 2 149 2334500 252000 30 7 C 9AQUIA 7 10 18 1 6 110 2 149 2338000 252000 35 5 C 9AQUIA 7 10 15 3 6 110 2 141 2341500 252000 30 7 C 9AQUIA 7 6 9 5 6 110 2 145 2345000 252000 25 7 C 9AQUIA 7 6 4 9 6 110 2 149 2254000 255500 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2257500 255500 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2261000 255500 30 7 P 6PIEDMONT 3 10 Is 3 4 50 1 114 2264500 255500 30 7 P 6PIEDMONT 3 10 15 3 4 50 1 114 2268000 255500 20 7 P 8PIEDMONT 4 3 9 5 5 so 1 118 2271500 255500 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2275000 255500 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2278500 255500 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2282000 255500 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2285500 255500 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2289000 255500 30 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 2292500 255500 35 5 P 8PIEDMONT 4 6 4 9 5 50 1 118 2296000 255500 40 5 C 9POTOMAC 8 6 4 9 7 400 4 153 2299500 255500 30 7 C 9POTOMAC 8 6 9 5 7 400 4 159 2303000 255500 30 7 C 9POTOMAC 8 10 15 3 7 400 4 165 2306500 255500 40 5 C 9AQUIA 7 10 15 3 6 110 2 141 2310000 255500 5 10 C 9AQUIA 7 6 1 10 6 110 2 165 2313500 255500 50 5 C 9AQUIA 7 6 9 5 6 110 2 135 2317000 255500 40 5 C 9AQUIA 7 6 9 5 6 110 2 135 2320500 255500 40 5 C 9CH/P 7 10 15 3 6 90 1 138 2324000 255500 40 5 C 9CH/P 7 10 18 1 6 90 1 136 2327500 255500 40 5 C 9AQUIA 7 10 18 1 6 110 2 139 2331000 255500 40 5 C 9AQUIA 7 10 18 1 6 110 2 139 2334500 255500 40 5 C 9AQUIA 7 10 18 1 6 110 2 139 2338000 255500 45 5 C 9AQUIA 7 10 18 1 6 110 2 139 2341500 255500 5 10 C 9AQUIA 7 6 4 9 6 110 2 164 2345000 255500 30 7 C 9AQUIA 7 6 4 9 6 110 2 149 2254000 259000 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2257500 259000 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2261000 259000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2264500 259000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 lis 2268000 259000 20 7 P 8PIED14ONT 4 3 4 9 5 50 1 122 2271500 259000 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2275000 259000 25 7 P 8PIEDMONT 4 6 9 5 5 so 1 124 2278500 259000 25 7 P 8PIEDMONT 4 6 9 5 5 50 1 124 REGIONAL R A S T I C DRAST I C VA GRID VA GRID AQUIFER RECHARGE MEAN I MP. HYDRAULIC E-W N-S DEPTH SYSTEM RATING AQUIFER SOIL SLOPE VADOSE CIONOWT. --------------------------------------------------------------------------------------------------------------------------------------- 2282000 259000 25 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 2285500 259000 25 7 P 8 PIEDMONT 4 6 9 5 5 50 1 124 2289000 259000 35 5 P 8 PIEDMONT 4 6 9 5 5 50 1 114 2292500 259000 35 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2296000 259000 45 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2299500 259000 45 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2303000 259000 5 10 C 9 POTOMAC 8 6 4 9 7 400 4 178 2306500 259000 5 10 C 9 AQUIA 7 6 4 9 6 110 2 164 2310000 259000 45 5 C 9 AQUIA 7 10 15 3 6 110 2 141 2313500 259000 45 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2317000 259000 40 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2320500 259000 40 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2324000 259000 40 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2327500 259000 40 5 C 9 AQUIA 7 10 15 3 6 110 2 141 2331000 259000 40 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2334500 259000 5 10 C 9 AQUIA 7 6 4 9 6 110 2 164 2338000 259000 5 10 C 9 AQUIA 7 6 4 9 6 110 2 164 2341500 259000 35 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2345000 259000 30 7 C 9 AQUIA 7 10 15 3 6 110 2 151 2250500 262500 25 7 P 3 PIEDMONT 3 10 is 1 4 50 1 100 2254000 262500 25 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2257500 262500 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2261000 262500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2264500 262500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2268000 262500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 Ln 2271500 262500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 262500 25 7 P 8 PIEDMONT 4 3 1 10 5 50 1 123 2278500 262500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 262500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2285500 262500 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2289000 262500 40 5 p 8 PIEDMONT 4 6 9 5 5 50 1 114 2292500 262500 45 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2296000 262500 5 10 C 9 POTOMAC 8 6 4 9 7 400 4 178 2299500 262500 35 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2303000 262500 20 7 c 9 POTOMAC 8 6 9 5 7 400 4 159 2306500 262500 40 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2310000 262500 35 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2313500 262500 35 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2317000 262500 25 7 C 9 AQUIA 7 6 9 5 6 110 2 145 2320500 262500 30 7 C 9 AQUIA 7 6 9 5 6 110 2 145 2324000 262500 40 5 c 9 AQUIA 7 6 9 5 6 110 2 135 2327500 262500 40 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2331000 262500 40 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2334500 262500 45 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2338000 262500 50 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2341500 262500 35 5 C 9 AQUIA 7 10 15 3 6 ilo 2 141 2247000 266000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2250500 266000 25 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2254000 266000 25 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2257500 266000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2261000 266000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 REGIONAL A S T C DRASTIC VA GRID VA GRID AQU I FER RECHARGE MEAN E-W N-S DEPTH SYSTEM RATING AQU I FER SOIL SLOPE IMP. HYDRAULIC --------------- ------------------------------------------- VADOSE CONDUCT. 2264500 266000 25 7 P 8 PIED14ONT 4 3 9 5 5 50 1 118 2268000 266000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2271500 266000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2275000 266000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2278500 266000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2282000 266000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2285500 266000 35 5 P 6 PIEDMONT 3 10 15 3 4 50 1 104 2289000 266000 40 5 P 6 PIEDMONT 3 10 15 3 4 so 1 104 2292500 266000 45 5 P 3 PIEDMONT 3 10 18 1 4 50 1 90 2296000 266000 45 5 P 6 PIEDMONT 3 10 15 3 4 50 1 104 2299500 266000 35 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2303000 266000 30 7 C 9 POTOMAC 8 10 15 3 7 400 4 165 2306500 266000 30 7 C 9 AQUIA 7 6 9 5 6 110 2 145 2310000 266000 35 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2313500 266000 35 5 C 9 AQUIA 7 6 9 5 6 110 2 135 2317000 266000 30 7 C 9 AQUIA 7 10 15 3 6 110 2 151 2320500 266000 45 5 C 9 AQUIA 7 10 15 3 6 110 2 141 2324000 266000 35 5 C 0 AQUIA 7 10 15 3 6 110 2 141 2327500 266000 35 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2331000 266000 35 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2334500 266000 25 7 C 9 AQUIA 7 10 18 1 6 110 2 149 2338000 266000 25 7 C 9 AQUIA 7 6 1 10 6 110 2 150 STAFFORD COUNTY GROUNDWATER PROTECTION STUDY NORTH OF VA 269500 OCTOBER 18, 1991 D REGIONAL R A S T I C DRASTIC VA GRID VA GRID AQUIFER RECHARGE MEAN IMP. HYDRAULIC E-W N-S DEPTH SYSTEM RATING AQUIFER AQ. MEDIA SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------------------------------------------------------------------------------------- 2247000 269500 20 7 P 6PIEDMONT 3 10 15 3 4 50 1 114 2250500 269500 20 7 p 8PIEDMONT 4 3 9 5 5 50 1 118 2254000 269500 20 7 P 8PIEDMONT 4 3 9 5 5 so 1 118 2257500 269500 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2261000 269500 20 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2264500 269500 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2268000 269500 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2271500 269500 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2275000 269500 25 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2278500 269500 30 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2282000 269500 30 7 p 8PIEDMONT 4 3 9 5 5 50 1 118 2285500 269500 35 5 P 6PIEDMONT 3 10 is 3 4 50 1 104 2289000 269500 45 5 P 6PIEDMONT 3 10 15 3 4 50 1 104 2292500 269500 50 5 P 6PIEDMVT 3 10 is 3 4 50 1 104 2296000 269500 50 5 c 9POTOMAC a 10 is 3 7 400 4 155 2299500 269500 45 5 C 9POTOMAC 8 6 9 5 7 400 4 149 2303000 269500 40 5 c 9POTOMAC 8 6 9 5 7 400 4 149 2306500 269500 40 5 c 9POTOMAC a 6 9 5 7 400 4 149 23100,00 269500 40 5 C 9AQUIA 7 6 9 5 6 110 2 135 2313500 269500 40 5 C 9AQUIA 7 10 15 3 6 110 2 141 2317000 269500 40 5 C 9AQUIA 7 10 15 3 6 110 2 141 2320500 269500 30 7 C 9AQUIA 7 10 15 3 6 110 2 151 2324000 269500 30 7 c 9AQUIA 7 10 18 1 6 110 2 149 2327500 269500 25 7 c 9AQUIA 7 10 18 1 6 110 2 149 2331000 269500 20 7 c 9AQUIA 7 10 18 1 6 110 2 149 2334500 269500 20 7 c 9AQUIA 7 10 is 3 6 110 2 151 2338000 269500 20 7 C 9AQUIA 7 6 1 10 6 lio 2 150 2341500 269500 20 7 C 9AQUIA 7 6 1 10 6 110 2 150 2247000 273000 20 7 P 8PIEDMONT 4 3 9 5 5 50 1 lie 2250500 273000 20 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2254000 273000 20 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2257500 273000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2261000 273000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2264500 273000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2268000 273000 30 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2271500 273000 30 7 P 8PIEDMONT 4 3 9 5 5 50 1 118 2275000 273000 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2278500 273000 25 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2282000 273000 20 7 P 8PIEDMONT 4 3 4 9 5 50 1 122 2285500 273000 30 7 P 6PIEDMONT 3 10 15 3 4 50 1 114 2289000 273000 40 5 P 3PIEDMONT 3 10 18 1 4 50 1 90 2292500 273000 45 5 P 3PIEDMONT 3 10 18 1 4 50 1 90 2296000 273000 40 5 c 9POTOMAC a 10 15 3 7 400 4 155 2299500 273000 40 5 c 9POTOMAC a 6 9 5 7 400 4 149 2303000 273000 55 3 c 9POTOMAC a 6 9 5 7 400 4 139 2306500 273000 65 3 C 9POTOMAC 8 6 9 5 7 400 4 139 2310000 273000 65 3 C 9POTOMAC a 6 9 5 7 400 4 139 2313500 273000 50 5 C 9AQUIA 7 6 9 5 6 110 2 135 D REGIONAL R A S T C DRAST I C VA GRID VA GRID AVAJIFER RECHARGE MEAN IMP. HYDRAULIC E-W N-S DEPTH SYSTEM RAT I NG AQU I FER SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------------------------------------------------------------------------------------- 2317000 273000 55 3 C 9 AQUIA 7 6 9 5 6 110 2 125 2320500 273000 45 5 C 9 AQU I A 7 10 15 3 6 110 2 141 2324000 273000 45 5 C 9 AQUIA 7 10 18 1 6 110 2 139 2327500 273000 20 7 C 9 AQUIA 7 10 18 1 6 110 2 149 2331000 273000 is 9 C 9 AQUIA 7 10 18 1 6 110 2 159 2334500 273000 15 9 C 9 AQUIA 7 6 4 9 6 110 2 159 2338000 273000 15 9 C 9 AQUIA 7 6 4 9 6 110 2 159 2247000 276500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2250500 276500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2254000 276500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 ila 2257500 276500 35 5 P 8 PIEDMONT 4 3 9. 5 5 50 1 108 2261000 276500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2264500 276500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2268000 276500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 276500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 276500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2278500 276500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2282000 276500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2285500 276500 40 5 P 6 PIED14ONT 3 10 15 3 4 5D 1 104 2289000 276500 35 5 P 6 PIEDMONT 3 10 15 3 4 50 1 104 2292500 276500 30 7 P 8 PIEDMONT 4 3 9 5 5 56 1 118 2296000 276500 30 7 P 8 PIED14ONT 4 6 9 5 5 50 1 124 2299500 276500 30 7 C 9 POT014AC a 6 9 5 7 400 4 159 2303000 276500 50 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2306500 276500 60 3 C 9 POTOMAC 8 6 9 5 7 400 4 139 2310000 276500 60 3 C 9 POTOMAC 8 6 9 5 7 400 4 139 co 2313500 276500 45 5 C 9 POT014AC 8 6 9 5 7 400 4 149 2317000 276500 40 5 C 9 POT014AC 8 10 15 3 7 400 4 155 2320500 276500 40 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2324000 276500 70 3 C 9 POT014AC 8 10 15 3 7 400 4 145 2327500 276500 25 7 C 9 POTOMAC 8 6 9 5 7 400 4 159 2331000 276500 15 9 C 9 POTOMAC 8 6 1 10 7 400 4 174 2334500 276500 20 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2338000 276500 25 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2250500 280000 20 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2254000 280000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2257500 280000 35 5 P 8 PIEDMONT 4 3 4 9 5 50 1 112 2261000 280000 25 7 P 8 PIEDMONT 4 3 4 9 5 so 1 122 2264500 280000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2268000 280000 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 280000 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 280000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2278500 280000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2282000 280000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 1% 2285500 280000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2289000 280000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2292500 280000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2296000 280000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2299500 280000 30 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2303000 280000 35 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2306500 280000 40 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 REGIONAL A S T I C DRASTIC VA GRID VA GRID AQUIFER RECHARGE E-W N-S DEPTH 14EAW IMP. HYDRAULIC SYSTEM RATING AQU I F ER SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------------------------------------------------------------------------------------- 2310000 2BU000 45 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2313500 280000 35 5 C 9 POTOMAC 8 10 15 3 7 400 4 Iss 2317000 280000 35 5 c 9 POTOMAC a 6 9 5 7 400 4 149 23ZO500 280000 40 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2324000 280000 60 3 C 9 POTOMAC 8 10 15 3 7 400 4 145 2327500 280000 20 7 C 9 POTOMAC 8 6 4 9 7 400 4 163 2331000 280000 20 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2334500 280000 25 7 C 9 POTOMAC a 6 1 10 7 400 4 164 2338000 280000 25 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2247000 283500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2250500 283500 25 7 P 6 PIEDMONT 3 10 is 3 4 so 1 114 2254000 283500 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila 2257500 283500 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila 2261000 283500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2264500 283500 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila 2268000 283500 35 5 P 8 PIEDMONT 4 3 4 9 5 50 1 112 2271500 283500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 283500 25 7 P 8 PIED14ONT 4 3 4 9 5 50 1 122 2278500 283500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 283500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2285500 283500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2289000 283500 30 7 P 8 PIED14ONT 4 3 9 5 5 50 1 118 2292500 283500 25 7 P a PIEDMONT 4 3 9 5 5 50 1 118 2296000 283500 25 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2299500 283500 35 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 2303000 283500 40 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 2306500 283500 40 5 C 9 POTOMAC 8 3 9 5 7 400 4 143 2310000 283500 40 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2313500 283500 20 7 C 9 POTOMAC 8 10 15 3 7 400 4 165 2317000 283500 25 7 C 9 POTOMAC 8 10 15 3 7 400 4 165 2320500 283500 30 7 c 9 POTOMAC 8 6 4 9 7 400 4 163 2324000 283500 5 10 c 9 POTOMAC 8 6 9 5 7 400 4 174 2327500 283500 15 9 C 9 POTOMAC 8 10 18 1 7 400 4 173 2331000 283500 20 7 C 9 POTOMAC 8 6 9 5 7 400 4 159 2334500 283500 20 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2338000 283500 25 7 C 9 POTOMAC 8 6 1 10 7 400 4 164 2250500 287000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2254000 287000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2257500 287000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila 2261000 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2264500 287000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2268000 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 287000 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 287000 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2278500 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2285500 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2289000 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2292500 287000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2296000 287000 15 9 P 8 PIEDMONT 4 3 9 5 5 50 1 128 2299500 287000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila REGIONAL R A S T I DRASTIC VA GRID VA GRID AQU I FER RECHARGE MEAN IMP. HYDRAULIC E-W N-S DEPTH SYSTEM RATING AQUIFER SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------- ----------------------------------------------------------------------------- 2303000 287000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2306500 287000 35 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2310000 287000 40 5 C 9 POTOMAC 8 3 9 5 7 400 4 143 2313500 287000 30 7 C 9 POT014AC 8 6 4 9 7 400 4 163 2317000 287000 20 7 C 9 POTOMAC 8 6 9 5 7 400 4 159 2320500 287000 5 10 C 9 POTOMAC 8 6 4 9 7 400 4 178 2324000 287000 15 9 C 9 POTOMAC 8 10 18 1 7 400 4 173 2327500 287000 20 7 C 9 POTOMAC 8 10 18 1 7 400 4 163 2331000 287000 20 7 C 9 POTOMAC 8 10 18 1 7 400 4 163 2334500 287000 15 9 C 9 POT014AC 8 10 15 3 7 400 4 175 2247000 290500 35 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 2250500 290500 35 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 2254000 290500 30 7 p 8 PIEDMONT 4 3 9 5 5 50 1 118 2257500 290500 20 7 P 8 PIEDMONT 4 3 9 290500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2261000 5 5 50 1 118 2264500 290500 15 9 p 8 PIEDMONT 4 3 4 9 s 50 1 132 2268000 290500 25 7 p 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 290500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2275000 290500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2278500 290500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 290500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2285500 290500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2289000 290500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2292500 290500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2296000 290500 20 7 P 8 PIEDMONT 4 3 9 5 5 so 1 118 2299500 290500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 C3 2303000 290500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2306500 290500 25 7 p 6 PIEDMONT 3 10 15 3 4 50 1 114 2310000 290500 35 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2313500 290500 35 5 C 9 POTOMAC 8 6 9 5 7 400 4 149 2317000 290500 25 7 C 9 POT014AC 8 6 9 5 7 400 4 159 2320500 290500 5 10 C 9 POTOMAC 8 6 1 10 7 400 4 179 2324000 290500 20 7 C 9 POT014AC 8 10 18 1 7 400 4 163 2327500 290500 35 5 C 9 POT014AC 8 10 18 1 7 400 4 153 2331000 290500 20 7 C 9 POTOMAC 8 10 18 1 7 400 4 163 2334500 290500 20 7 C 9 POTOMAC 8 6 9 5 7 400 4 159 2338000 290500 20 7 C 9 POTOMAC 8 6 4 9 7 400 4 163 2250500 294000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2254000 294000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2257500 294000 10 9 p 8 PIEDMONT 4 3 9 5 5 50 1 128 2261000 294000 15 9 P 8 PIEDMONT 4 3 9 5 5 50 1 128 2264500 294000 15 9 P 8 PIEDMONT 4 3 4 9 5 so 1 132 2268000 294000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 294000 30 7 P 8 PIED14ONT 4 3 4 9 5 50 1 122 2275000 294000 15 9 P 8 PIEDMONT 4 3 4 9 5 50 1 132 2278500 294000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 294000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2285500 294000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2289000 294000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2292500 294000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2296000 294000 20 7 P 8 PIED14ONT 4 3 4 9 5 50 1 122 REGIONAL A S T C DRAST I C VA GRID VA GRID AQUIFER RECHARGE MEAN IMP.' HYDRAULIC E-W N-S DEPTH SYSTE14 RAT I NG AQU I FER SOIL SLOPE VADOSE CONDUCT. --------------------------------------------------------------------------------------------------------------------------------------- 2299500 294000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2303000 294000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2306500 294000 20 7 P 6 PIEDMONT 3 10 15 3 4 50 1 114 2310000 294000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2313500 294000 35 5 c 9 POTOMAC 8 3 9 5 7 400 4 143 2317000 294000 5 10 C 9 POTOMAC 8 6 4 9 7 400 4 178 2320500 294000 25 7 C 9 POTOMAC a 6 9 5 7 400 4 159 2324000 294000 20 7 C 9 POTOMAC 8 10 15 3 ;r 400 4 165 2327500 294000 25 7 C 9 POTOMAC 8 10 18 1 7 400 4 163 2331000 294000 20 7 C 9 POTOMAC 8 10 18 1 7 400 4 163 2334500 294000 25 7 C 9 POTOMAC a 10 15 3 7 400 4 165 2338000 294000 25 7 c 9 POT014AC 8 6 4 9 7 400 4 163 2254000 297500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2257500 297500 20 7 P 8 PIED14ONT 4 3 9 5 5 50 1 Ila 2261000 297500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2264500 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2268000 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2278500 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2282000 297500 25 7 P 8 PIEDMONT 4 3 4 9 5 so 1 122 2285500 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2289000 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2292500 297500 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2296000 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2299500 297500 30 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2303000 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2306500 297500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2310000 297500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2313500 297500 35 5 c 9 POTOMAC 8 3 9 5 7 400 4 143 2317000 297500 5 10 c 9 POTOMAC 8 6 1 10 7 400 4 179 2320500 297500 35 5 c 9 POTOMAC 8 6 9 5 7 400 4 149 2324000 297500 35 5 c 9 POTOMAC 8 6 9 5 7 400 4 149 2327500 297500 15 9 C 9 POTOMAC 8 10 15 3 7 400 4 175 2331000 297500 15 9 c 9 POT014AC a 10 18 1 7 400 4 173 2334500 297500 15 9 c 9 POTOMAC 8 10 18 1 7 400 4 173 2338000 297500 20 7 c 9 POTOMAC 8 10 15 3 7 400 4 165 2257500 301000 30 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2261000 301000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2264500 301000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2268000 301000 20 7 p 8 PIEDMONT 4 3 4 9 5 50 1 122 2271500 301000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2278500 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2282000 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2285500 301000 20 7 P 8 PIEDMONT 4 3 4 9 5 so 1 122 2289000 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2292500 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2296000 301000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2299500 301000 35 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 2303000 301000 45 5 P 8 PIEDMONT 4 3 9 5 5 50 1 108 REGIONAL A S T I c DRASTIC VA GRID VA GRID AQUIFER RECHARGE MEAN E-W N-S DEPTH IMP. HYDRAULIC SYSTEM RATING AQUIFER SOIL SLOPE VADOSE CONDUCT. ----------------- ------ .................... -------------------- ------------- --------- ------------------------------------- 2J06500 301UOO 55 3 P 8 PIEDMONT 4 3 9 5 5 50 1 98 2310000 301000 60 3 P 6 PIEDMONT 3 10 15 3 4 50 1 94 2313500 301000 55 3 P 8 PIEDMONT 4 3 9 5 5 50 1 98 2317000 301000 50 5 c 9 POTOMAC 8 3 9 5 7 400 4 143 2320500 301000 35 5 C 9 POTOMAC a 10 15 3 7 400 4 155 2324000 301000 45 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2327500 301000 45 5 C 9 POTOMAC 8 10 15 3 7 400 4 155 2331000 301000 15 9 C 9 POTOMAC 8 10 15 3 7 400 4 175 2334500 301000 15 9 C 9 POTOMAC 8 10 18 1 7 400 4 173 2261000 304500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2264500 304500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 Ila 2268000 304500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2271500 304500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 304500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2278500 304500 20 7 P 8 PIEDMONT 4 3 4 9 5 so 1 122 2282000 304500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2285500 304500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2320500 304500 30 7 c 9 POTOMAC 8 6 9 5 7 400 4 159 2324000 304500 30 7 C 9 POTOMAC 8 6 9 5 7 400 4 159 2264500 308000 20 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2268000 308000 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2271500 3080oo 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2275000 308000 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2320500 308000 25 7 C 9 POT014AC 8 10 15 3 7 400 4 165 2324000 308000 25 7 C 9 POTOMAC 8 10 15 3 7 400 4 165 2264500 311500 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2268000 311500 25 7 P 8 PIEDMONT 4 3 9 5 5 50 1 118 2271500 311500 20 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 2320500 311500 25 7 C 9 POTOMAC 8 10 15 3 7 400 4 165 2324000 311500 25 7 C 9 POTOMAC 8 6 4 9 7 400 4 163 2268000 315000 25 7 P 8 PIEDMONT 4 3 4 9 5 50 1 122 I I I I I APPENDIX B' I GEOGRAPHIC DISTRIBUTION OF DRASTIC PARAMETER RATINGS I I I I I I I I I I I 1 43 1 2240000 2254000 2268000 228200D 2296000 2310000 2324000 2338000 2352000 -136000 325500 Z25500 -'15000 - 1@-000 --04500 -C)4-500 7 'A, 7 5 I\A- 9 9. 7 7 7 7 7 7 T 29401111 294-000 7' 7 T 7 7 7 7 7 7, 5 283500 7 7 5 7 7 17 7 7 5 5 5 5 -773000 --7 27-5000 7 7 f-\ V I 7 7 7 7 7 7 7 7 7 2-62500 1 4 262500 7 7 13 5 15 15 s 1 31 7, 7@7 5 7 16 5 " i 5 1) 5 1011013 '1 1\7 17 L4@ - I 252000 1 \ i - 252C,00 7 7 7 7 -1 7' 241500 7, 7 241500 131000 - - - 231000 5 7 220500 2205, FT 0000 2240000 22-54000 2-268000 @-82000 2296000 2310000 2324000 2338000 2352000 Fiqure 1 Depth to Water (D) Rating 44 2240000 2254000 2268000 2282000 2296000 2310000 2324000 2338000 2352000 336000 3360M 325500 325500 315000 - m/ 315000 304500 - S 304500 294000 294000 283500 283500 273000 9 27,3000 262500 262500 4,1 252000 252000 241500 241500 231000 231000 220500 220500 210000 210000 2240000 2254000 Z268000 2282000 2296000 2310000 2324000 2338000 2352000 Figure 4 Net Recharge (R) Rating 45 9t buLled (V) ?LP@W A@4pbV c ajn6Lj ODOZgCZ DOORCCZ OC)O*ZC-Z 0000 12Z 00096Z-17 ooozgz7 00029Z7- ODC)-VgZ7 OGDOVZ7 000 L z 0000 L D09OZZ OD90ZZ DIDO@N 000 2z 009 Itz 009 Ltlz _jv z + Dooz9z oooz-- t t 109- ; : + 4. DOOL'LZ OOOC LZ tt tt t I tt t V D0922z OOS227 7, t t tt t Doo,v6z OD0*6Z t t tt T t tt t Xgtoz +1 0 0 90 tl t i 0099Z2 ooggz@-' D009N 0009c2- ODOM:z DOOKU oootzu ooooli7 00096zz o0oz:Kz 00029zz ODOvs;zz OoDot,27 L t 6LJLJP@ (S) ajn5L2 ODOZ9CZ 0002CCZ 000* Z'2Z OOCIOtC@--' 00096Z7 Cloozezz 00029-@f7l oootl@jzz ooootz:- DOW L Z 'J-@ @- I I I I @ I I I I I I I I ODOCILZ 0090zz 009ozz 000 L@:z CIDOL2Z 1R cj@ 1@ POLW s I I II--, I C@ 009 L -0 z 0'[ ( L C 1 9 ip c I I I I @L c L I. 9L s L $ 9 01 + +c Ic CICIL CIL c L`-@ L cIc c L c Ict CILT 1 9 CL C@c@ I I I C L c t CL CL CIL L qLc L c LC1 I, -0 L-) 0 LCIL L C L 5 D09Z:9Z7 oogzsz C.L 91 oil c L @-J-cKqL cI. OL CL cL c L c L qI, 9L 9L 6T-c T- cLc L c I, c191 01, cl CI I 0002LZ OD02LZ 1@ql t IqL CL cl 0 1 qL CL L Ecl OR -i C I lC I, c L IqL L T c D0922Z 2 CL C109cez c Lc@ Z jqi 9L CIL CIL cT I' LCL oil, 1. c L C DOO-o6z CID0*6z 91 CT-T CL T @@l cl 01 009*0@ DOO 0009L- C1099zc CINGZ2 0009C2 - - - CID092c O0CZ9CZ COCIPM 000*Z@7 0QOD1i7 00096ZZ OCCIZ827 00029ZZ CIOCItSZZ OODOtZZ C -L Ead 2240000 2254000 2268000 2282000 Z296000 2310000 2324000 2338000 2352000 336000 --136000 325500 25500 I 15000 3 15000 704500 I I 294000 994000 110 283500 5 5 's 5 9 283500 Kib do 1) 5 @VlLl 3 1 15 273000 273000 3 262500 262500 5 3 s 3 3 5 S 5 3 10)1 252000 252000 @z L 241500 241500 10 231000 231000 0 s 9 ?20500 s 220500 1 101) 10 2, 0000 - 210000 2240000 21540111) Z2611011C 221121101) 2296000 231011011 23240DO 23311000 2357-0011 Figure 7 Topography 5 I -L LJ (T) Rating 48 1-240000 2254000 2268000 4-1282000 2296000 2,310000 2324000 2338000 2352000 7-36000 336000 21l 7 325500 325500 315000 315000 5 1 Yk-7 5 5; 1 iA 304500 -104500 5, i V 5 3 5 5 5 5 rl 294000 294000 7 '477 7 7 233500 5' 7 7 7 283500 5 7 7' 7@ 41 27,3000 "(5 5 s 1 273000 5, 6 262500 5 s 7 (1 262500 i 4. 4 5 @5 5 5 7 6 1 ix 4 5 E5 S-i 252000 252DOO 4 4 4 7 7 7 6 i 5 241500 5, 241500 j 3-s'si3 I 231000 231000 220500 220500 210000 1 -T r--@ 210000 2240000 2254000 2-268000 2282000 2296000 231C)OOD 2324000 2338DOO 2352000 Figure 9 Impact of Vadose Zone g (1) Rati n 6-1 At 49 2240000 2254000 2268000 2282000 2296000 2310000 2324000 2338000 2352000 336000 335000 325500 325500 3115-000 315000 -04500 304500 i A I "s-- 1 44,-/ 4' 4 4 294000 i V i i i 4- 4' 294000 4 4 4 4- 283500 283,500 i Q.. /73000 @-\ 273000 I I 1 4 + 2 4- 4 4- 262500 262500 2 -2 r@, 252000 252000 F34 241500 241500 231000 231000 220500 2 220500 210000 210000 2240000 2254000 2268000 2282000 2296000 2310000 2324000 2338000 2352000 Figure 9 Hydraulic Conductivity (C) Rating 50 2 2240000 2254000 2268000 2282000 2296000 2310000 2324000 2338000 2352000 336000 336000 325500 325500 315000 315000 I 4al IIAo 111$ 112212 118 1aJ2 I Z2 12@2 112 2 a @04500 - I ' 304500 - 'yo I li2 I i2 in 112 118 1 8 1 S_L22 1@ 1 6 ll@ -8 68 116 /1) 93 1 @/l 5@1 1' 15 1,13 !W1 IS 118 122 1122 122 1@ 122 1 2 t _!2 1 f' a 1 1 112 1 - 1,13 1' 294000 I"d 118 ILI 12; 8132 122 122 1 12 122 Iz2 112 122 1 2 122 in 112 14 IL8@ 1.2 1 a 10ll@ 1i3 1113 1., ly, I 1 294000 I i I I I I @841 IS lia 1 5 Iji8 Ii2 112 1JB 122 1:2 1 21;2 1;8 12 d8 1 8 1 8 114 1$5 10 IN 111,Ls 1Z143 IM i I i2 a Ila IS I@ I i@'8 142 1212 1 J@; 122 112 121211 8 Ila 1 8 in 1@1 1 13 153 1:'9 113 1,13 1@3 1113 1-5 @ I 283500 $)1 4 118 1 8 1212 1 1@8 111 z122 122 122 112.L 8118 1 8 1 4 M 10 1L 10 1115 llis 163 I-p4 13lig 104@ 283500 )1 4 1 81 2 122 122 122 122 1 aI'S 1 41 4 114 Ila 1 8 1J4 1 -9 114 149 115 14o 1! 15 1% 1 Q-44 144 4 Ia @, a I a10 1aI t2 -1 ZZ 122 1 51 81 a104 134 Ila 1;4 IL), 1 Is 1.19 1 19 1L 1 Z 1! 15 1 -Z 1 @4 6 1 Q 139 If9 Iz 135 1 7_73000 1 a 1 a1 5 118 1 18 122 1 JS 1 @2 122 1 211@ 9@ -M '5 ILI 1 i9 1@ 111@1 1 273000 I I@ I a I is I B Ila I li a 1212 12211 B1@2 1 8104 1 JA 41 @ 5 1.9 1 .9 149 135 111 1 1 151 11.9 1Q1 - Q 1411 0\1 So I I 11 ; ; I i \ I 1111 1 4 1 41 8 12.2 J'8 118 J8 1 12 1 81 41,14 4. Il4 90 1(4 156 116 1+5 1 @6 135 1 1 1+1 1 .1 1. a1@ 1 1 41 9 122 Ila Ila 122 113 122 IS Ila 1 14 1 Is 173 1 .9 1S9 1. z 125 1@5 1 115 IJ5 in 1@ 9 t g I d 262500 262500 1 1ii2 .4 1 4 I@ 4 11'4 1 .9 1 ja 1 9 1 13 114 14.1 135 IM 1. 51.19 1, 11M V , 1 151 1 81! U I@a Ila J2I1 14 ii i i i 1 8 114 1114 116 1 i14 It4 1:4 124 t 411* Ile I v 1 z 11.1 165 li5 1 6 1:6 116 1z9 1.39 139 119 1 4 1 91W 14.1 1 i9 I@ 5 IS2 157 1@6 \1 4104 1;* l14 114 I@ A1@ 118 124 118 128 149 IS I. .9-L 9 111 1 Alai 252000 252000 114 114@@04 112+ t4 114 118 1_@_' + 1 4 1+9 1 ig 141 1+1 151 I@ 1 14 IL 4@ @7, o SO 1 1 14 X@4 /14 104 1 @@5 1 4114 124 12, 8 1 e 1$-5 49 1! 19 1 L 115 115 1.5 1 45 1 18 1 IS V I 1@ 241500 1ix 114 124 1 W, 1 4 114 Ila 1, Is 1'. @q 1 i3 139 139 im iss 1 .2 IL 1L8 I@ 1 129 24.1500 4-r, 0 vA I g 139 1 L), 1 9 116 14 112 1, 1 A 1, 1! i3 13S I i9 1 5 1 a 14 116 1 2J2 1@1 231000 IW 1 .3 I@Q 1 ;9 119 1 5 IN 1-6 10 1 2 231000 i 1 @14 1 19 1 .9 135 1 9 1.5 156 421 .9 1 .9 ik 1 9 1.9 46 144 '220,500 J@Q 1-0 11.0 1 59 1 @o 14,g 1 +Ig I @g 220500 9 Ila 1 .0 1 9 2@0 1 9 210000 - 210000 22400DO 2254000 Z268000 2282000 2296000 2310000 23240DO 2338000 2352000 Figure 10 Compo site DRASTIC Index Rating 51 DATE DUE GAYLORD No. 2333 PRINTED IN U.S.A. 116668 1 .107 7257