BROCKMAN, ALLEN R., and GEORGE E. HARLOW, JR.,* U.S. Geological Survey, Richmond, VA

ABSTRACT: The Shallow Aquifer System at the Naval Surface Warfare Center, Dahlgren Laboratory, Dahlgren, Virginia

In 1992, the U.S. Geological Survey began a 3-yr study of the hydrogeology at the Naval Surface Warfare Center Dahlgren Laboratory (NSWCDL) at Dahlgren, Virginia. The purpose of the study was to determine the altitude of the top, thickness, extent, water level, and hydraulic conductivity of the aquifers and confining units within 220 ft of land surface.

A literature review indicated that one unconfined aquifer (the Columbia aquifer) and one confined aquifer (the Aquia aquifer) were up to 200 ft deep at the NSWCDL, but a preliminary analysis of electric and natural-gamma geophysical logs collected during the study identified another confined aquifer (the Chickahominy-Piney Point aquifer, between the Columbia and Aquia aquifers) not indicated in the literature. The presence of this aquifer at the NSWCDL was confirmed by analysis of split-spoon core samples.

The shallow aquifer system at the NSWCDL includes three aquifers and two confining units; they are, from the uppermost downward, the Columbia aquifer (10 to 28 ft thick), the Calvert confining unit (20 to 45 ft thick), the Chickahominy-Piney Point aquifer (16 to 31 ft thick), the Nanjemoy-Marlboro confining unit (75 to 143 ft thick), and the Aquia aquifer (thickness exceeds 23 ft). None of the wells penetrated to the base of the Aquia aquifer.

AAPG Search and Discovery Article #90995©1993 AAPG Eastern Section Meeting, Williamsburg, Virginia, September 19-21, 1993.