Selected Tasks in Support of Hydrogeologic Characterization of Ft. Detrick, near Frederick, Maryland

WRD PROJECT #: MD148
PROJECT CHIEF: Phelan, Daniel
BEGIN DATE: 01-July-1998
END DATE: 30-September-2001

Customers currently supporting the project:

U.S. Army Corps of Engineers, Baltimore District

Problem

Ft. Detrick is the Army's primary site for research, development, and testing of biological warfare agents. It is located in a valley underlain by limestone and the ground-water flow system may include both epikarstic and deeper, diffuse flow. ICF Kaiser has been characterizing the site hydrogeology. Work by the USGS should result in increased understanding of this complex flow system. Three of the tasks will be performed at Robinson Spring, which is located east of the base boundary, and appears to be a regional ground-water discharge point. High levels of TCE and PCE have been measured intermittently at this spring.

Objectives

1. Determine how the discharge of Robinson Spring varies over time. Attempt to distinguish epikarstic flow from the deeper, diffuse flow system.
   
2. In the area near the eastern boundary of Area B, find the location and orientation of the geologic structure that separates the Cambrian limestone from the Triassic bedrock.
   
3. Perform two regional seepage measurements in streams surrounding Area B of Fort Detrick to determine which sections of streams are gaining or losing water. This effort will define areas where ground water is discharging to streams in order to locate the best sampling sites to monitor for discharge of potentially contaminated ground water.

Approach

1. Install a weir and a continuous discharge recorder at Robinson Spring. This will enable us to determine how the discharge of the spring varies over time. A hydrograph will be constructed and, if there is enough range in discharge, hydrograph separation techniques will be used to distinguish epikarstic flow regimes from the deeper, diffuse flow system.
   
2. Use the azimuthal square-array direct-current resistivity method to determine location and orientation of the geologic structure that separates the Cambrian and Triassic bedrock.
   
3. Choose approximately 60 sites along streams to measure discharge, specific conductance, pH, and temperature. Perform the synoptic measurements during a period of late summer base flow, and spring base flow. Using the data, identify sections of the streams that are gaining and losing flow, and identify sites to monitor for discharge of potentially contaminated ground water. The late summer measurements were made in 2000, and the spring measurements will be made in 2001.