DEVELOPMENT AND APPLICATION OF A GROUNDWATER FLOW MODEL OF THE CROUCH BRANCH AND MCQUEEN BRANCH AQUIFERS, CHESTERFIELD COUNTY, SOUTH CAROLINA

Chesterfield County is located in the northern part of South Carolina and adjacent to the North Carolina border and lies on the Fall Line, the geologic boundary between the Atlantic Coastal Plain (ACP) and Piedmont physiographic provinces. Between 2000 and 2010, the population in Chesterfield County increased from 42,768 to 46,734 people (U.S. Census Bureau, 2012). Associated with this population growth was an increased demand for domestic, public, industrial, and agricultural water supplies.

Much of Chesterfield County is served by a public supply utility, whose sole sources of water are the ACP Crouch Branch and McQueen Branch aquifers (Campbell and Coes, 2010). The average annual groundwater use is approximately 2 million gallons per day from 11 production wells. The future holds potential for the construction and operation of new industries in Chesterfield County that would require a substantial increase in the demand for high-quality water. Impacts of these proposed increases in withdrawals on existing groundwater and surface-water resources of the area are unclear.

The objective of the investigation is to develop a groundwater flow model that can be applied to facilitate management of the water resources in Chesterfield County. Better management practices would help achieve sustainability of the water resources and minimize the potential for excessive groundwater-level declines and potential adverse impacts on surface-water resources. In addition, a better understanding of the relation between groundwater contaminated with ethylene dibromide, dibromochloropropane, and radium, and their sources and transport will provide guidance on the fate of these contaminants with respect to potable water supplies. A particle-tracking code is used to generate advective water-particle pathlines and their associated time of travel based on the groundwater flow simula­tions. The particle tracking program computed three-dimensional flow directions and time of travel using imaginary particles in a backtracking mode from the production wells to identify recharge areas. Results from the particle tracking simulations could be used, along with knowledge of the identified groundwater contaminates, to guide the placement of future wells.