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EXECUTIVE SUMMARY

This plan was developed in response to the extended drought of 2001 through 2003. Accordingly, the County Board of Supervisors determined that a comprehensive evaluation of the groundwater resource was warranted. Stafford County is faced with a high rate of growth and considerable residential development pressure. This trend is in balance with a developing commercial and industrial sector. Recreational use of the land in the form of golf courses has placed additional pressures on the groundwater resource. This Plan was prepared in an effort to evaluate and the groundwater resource and propose management strategies to protect both quantity and quality of the resource.

The primary source of data in this plan was existing Virginia Department of Health (VDH) well logs from individual wells serving single family wells. A total of 1669 well records were collected from various hardcopy sources, scanned into a digital format, condensed into a database and successfully georeferenced onto a Countywide Geographic Information System (GIS) platform. From the outset of the project it was determined that this Plan would be supported by a companion web page that would provide an interactive platform for the data and access to the data by interested parties. That website has been compiled is currently available.

Stafford County is characterized as having three distinct geological units, trending from west to east; the Piedmont Crystalline Bedrock System, the Fall Zone (or Coastal Plain Aquifer recharge zone) and the Coastal Plain System. In general these systems are geologically unique from one another and have very distinct characteristics. The Piedmont system is dependent on fractures for groundwater production, yield and recharge. The Coastal Plain system is described as an eastwardly thickening wedge of sediments that is dependent on precipitation recharge and porosity of sands and gravels for storage. The Fall Zone is an area where a thin veneer of Coastal Plain sediments overlies a highly faulted crystalline bedrock, and is generally the area of outcrop (and resulting recharge) of the Coastal Plain aquifers.

The Coastal Plain shallow wells are constructed in the uppermost, or water table, aquifer; typically the Aquia. These wells are quite susceptible to impacts from surface water contamination as there is no impermeable confining layer between the surface and the water table. On the contrary these wells are typically sited in the most permeable zone possible, typically sands and clays. These wells, however, are not as susceptible to influence of pumping from deeper wells in the Middle Potomac Aquifer. The Middle Potomac is confined by a thick layer of clay. This confining unit limits the vertical connection between the two aquifers and functions as a 'ceiling' to the pumping dynamics of the Middle Potomac. Therefore, Coastal Plain shallow wells are susceptible to surface impacts, but largely unthreatened by deep pumping.

Shallow, or bored, wells in the Piedmont region are typically completed in the residual soils over bedrock, or saprolite. Saprolite wells are often protected from surface impacts by a well developed and continuous clay subsoil layer. They are, however susceptible to both drought and pumping from deeper wells, (EGGI, 1996). Both drought and deep pumping impacts are a function of the hydrogeologic setting of the Piedmont. The saprolite layer functions as a storage unit for the underlying bedrock fractures. Therefore, in time of drought and deep pumping, the saprolite storage is drawn upon at a rate that exceeds recharge and often the shallow wells are impacted. Accordingly, Piedmont shallow wells can be generally characterized as being less vulnerable to surface impacts and more susceptible to drought and deep pumping conditions.

Current groundwater use is largely residential in nature. The vast majority of wells service single family homes. Applying a worst case perspective production from the aquifers beneath Stafford County could range between 3.2 and 5.3 million gallons per day in the near future. This compares with conservative estimate of between 31 to 43 million gallons a day being available in the Coastal Plan and Piedmont systems combined.

Future residential groundwater use has been estimated at between 2.22 million and 4.6 million gpd in the year 2007 assuming an estimated rate of growth of 5 percent per year. Similarly, in the year 2012 residential demands could be estimated at between 2.83 and 5.85 million gpd, with a combined six month peak range of 4.43 to 7.45 million gpd when agricultural and golf course demand estimates are included. It is important to note that drought conditions often occur during summer months that correspond with agricultural and golf course demand. Golf course development will likely be the primary factor in increased nonresidential demands, with agricultural uses comprising a smaller portion of the increased demand.

Stafford County relies on two reservoirs to supply treated, domestic water to Stafford’s residents and businesses. A third reservoir is in the planning stages. The County’s water supply network is oriented to existing development primarily within the Route 1/I-95 corridor. Gradual expansion of the water system, and in-filling areas that have currently been by-passed, may be one tool the County can use to influence the location of new development in the County. In such a case, protecting wells within close proximity to the existing water lines may be less of a priority than protecting wells far removed from the water system. To address this issue, the County could consider a differential requirement for testing of new wells, or could even require new development within a defined distance from the existing water lines to connect to public water supplies. As well, the most difficult wells to replace, that is, community wells or wells serving public purposes, could be identified and ranked as to their potential vulnerability and cost of replacement. For those wells with high vulnerability and high cost of replacement, wellhead protection zones could be defined, with rigorous standards for new development aimed at protecting the public water resource. Weaker controls could be defined for low vulnerability/high replacement cost wells.

It is no accident that the developed areas in Stafford and counties to the north and south tend to cluster along a north south line where the Coastal Plain meets the Piedmont - the "fall line." Complicating the picture for groundwater management, the fall line is also the zone where the eastward sloping aquifers of the coastal plain rise to the surface - what we term the aquifer recharge area. Thus, historic development trends, modern infrastructure development, and public services all converge to focus the greatest potential for economically important industrial development within an area that is highly vulnerable to contamination, and an important element of groundwater management within the coastal plain.

Because Stafford’s public water infrastructure effectively serves most areas within the aquifer recharge zone, protection of well yields within the area may be of a lower priority since water service can be extended to replace failing or at-risk wells. Of greater importance, may be protecting the ability of the recharge zone to absorb water, and preventing the introduction of pollutants into the downward sloping aquifers. Minimizing stormwater runoff through the use of infiltration BMPs has already been addressed by Stafford’s adoption of a Storm Water Management Ordinance.

The Stormwater Management Ordinance has focused on protecting the waters receiving streams within the County and of the Bay from pollutants carried by stormwater runoff. One strategy of the Ordinance is to minimize runoff by maintaining the ability of the land to absorb stormwater... a strategy that is quite consistent with the need to protect aquifer recharge capabilities. A second element of groundwater management in the area, however, should be to minimize the potential for pollution to enter the groundwater resource. Pollutants introduced in this area have the potential to contaminate the deep aquifers to the east within and beyond Stafford County. Effective measures for managing pollution potential would include: first, identifying existing sources of potential pollution and ensuring that essential spill prevention and cleanup measures are in place; and second, using an overlay zoning district to ensure that site plans for new development incorporate adequate pollution prevention measures. For some highrisk, high-hazard uses, adequate prevention designs are not available and disallowing those uses might be the most feasible control strategy.

It should be noted that the Stafford County Groundwater Resource Protection Plan (GKY, 1994), which is discussed in detail in Section 3. 3.1 of this Plan, presents guidelines for protecting groundwater quality as development occurs. These strategies are organized as function of groundwater vulnerability as described in the study. Many of the guidelines are very appropriate and are reiterated below in some instances. As the DRASTIC study and its recommendations have been formally accepted by the County in the form of a Resolution, it is suggested that the County revisit those recommendations when compiling future guidelines or ordinances. The following strategies are meant to augment those recommendations and provide the County with a broad range of strategic possibilities.

It is apparent the County has a valuable and robust resource in its groundwater reserves. The vulnerability of the resource can be generalized as quantity in the Piedmont and quality in the recharge zone and coastal plain. To address these issues and provide adequate and reasonable protections and ordinance could be drafted that requires:

• Conditional Use Permits or Special Exceptions for certain proposed land uses within the Fall Zone.
• Conditional Use Permits or Special Exceptions for certain proposed land uses within a prescribed radius of 1,000 feet from existing and proposed community water supply wells.
• Performance of hydrogeologic testing and modeling of proposed groundwater withdrawals equal to or greater than 300,000 gallons per month. This would include both individual well withdrawal and cumulative well withdrawal from residential subdivisions based on an assumed average of 400 gallons per day per well (subdivisions of greater than 25 lots). Adoption by reference of the Virginia Department of Environmental Quality Groundwater Withdrawal Permitting requirements should be considered.