Hydraulic and solute-transport properties and simulated advective transport of contaminated ground water in a fractured rock aquifer at the Naval Air Warfare Center, West Trenton, New Jersey, 2003

Abstract

Volatile organic compounds, predominantly trichloroethylene and its degradation products, have been detected in ground water at the Naval Air Warfare Center (NAWC), West Trenton, New Jersey. An air-stripping pump-and-treat system has been in operation at the NAWC since 1998. An existing groundwater flow model was used to evaluate the effect of a change in the configuration of the network of recovery wells in the pump-and-treat system on flow paths of contaminated ground water. The NAWC is underlain by a fractured-rock aquifer composed of dipping layers of sedimentary rocks of the Lockatong and Stockton Formations. Hydraulic and solute-transport properties of the part of the aquifer composed of the Lockatong Formation were measured using aquifer tests and tracer tests. The heterogeneity of the rocks causes a wide range of values of each parameter measured. Transmissivity ranges from 95 to 1,300 feet squared per day; the storage coefficient ranges from 9 x 10-5 to 5 x 10-3 ; and the effective porosity ranges from 0.0003 to 0.002. The average linear velocity of contaminated ground water was determined for ambient conditions (when no wells at the site are pumped) using an existing groundwater flow model, particle-tracking techniques, and the porosity values determined in this study. The average linear velocity of flow paths beginning at each contaminated well and ending at the streams where the flow paths terminate ranges from 0.08 to 130 feet per day. As a result of a change in the pump-and-treat system (adding a 165-foot-deep well pumped at 5 gallons per minute and reducing the pumping rate at a nearby 41-foot-deep well by the same amount), water in the vicinity of three 100-to 165-footdeep wells flows to the deep well rather than the shallower well.

Hydrogeologic Framework of Fractured Sedimentary Rock, Newark Basin, New Jersey

“…Joints, faults, and partings are generally not open so the strata have exceptionally low hydraulic conductivity and transmit little water. Strata within 75 m of land surface have a wide range of hydraulic conductivity (Lewis-Brown et al 2006). The lithostatic pressure progressively decreases with shallow depths.…”

Estimating Effective Porosity in Bedrock Aquifers

“…This was shown by a pumping test in a carbonate aquifer in Ontario (Canada) that gave a specific yield of 4 × 10 −4 , where three well-to-well tracer tests gave a geometric mean effective porosity of 7 × 10 −4 (Worthington et al 2012). Similarly, five pumping tests in mudstone, siltstone and sandstone in New Jersey gave a specific yield of 5 × 10 −3 , and three tracer tests gave a geometric mean effective porosity of 1 × 10 −3 (Lewis- Brown et al 2006).…”

“…Near‐surface fracture porosity in bedrock aquifers is often substantially higher than at depth due to fracture enlargement, principally by weathering (Figure 4b). This occurs for instance in shales and sandstones (Gburek et al 1999; Lewis‐Brown et al 2006), in crystalline rocks (Lachassagne et al 2011), and in carbonate rocks (Rushton and Chan 1976; Allen et al 1997). The higher dissolution rates for carbonate minerals than for silicate minerals often results in dissolution to depths more than 100 m, and greater focusing of flow into channels.…”

Specification of Matrix Cleanup Goals in Fractured Porous Media

“…Aqueous phase concentrations within the fractures were evaluated at z = 1, 10, and 100 m. Figures 2 and 3 illustrate the agreement between the two models. An extensive description of the hydrogeology of the NAWC site and its surroundings is presented by Lewis-Brown et al (2003), Lacombe (2000), and Lacombe et al (2010). The input parameters in this study are utilized for purely illustrative purposes.…”

“…The input parameters in this study are utilized for purely illustrative purposes. An extensive description of the hydrogeology of the NAWC site and its surroundings is presented by Lewis-Brown et al (2003), Lacombe (2000), and Lacombe et al (2010). A fracture pore water compliance level of 5 μg/L was selected consistent with the conventional maximum contaminant level (MCL) established for TCE by the United States Environmental Protection Agency (USEPA 2009).…”