Hydrogeologic Characterization of the Washington Navy Yard

WRD PROJECT #: MD123
PROJECT CHIEF: Ferrarri, Mathew
BEGIN DATE: 01-January-1998
END DATE: 30-September-1998

Customers currently supporting the project:

U.S. Navy, Washington Yard

Problem

Site 71 at the Washington Navy Yard in the District of Columbia is an area that contained 13 underground storage tanks that ranged in size from 4,000 to 10,000 gallons. It was originally used as a fuel storage facility, where fuels were distributed to other operations and users through underground pipelines. It was also used as a staging area for refueling vehicles and other transport equipment. It is now paved over and used as a parking lot. Nine of the tanks, which contained waste oil, diesel fuel, and gasoline, have been removed and the other four tanks, which had unknown contents, were closed in place. There are four separate areas of contamination -- one is from leaks from the underground storage tanks and the other three are due either to spillage during refueling activities or leaks in underground pipelines. The Navy has proposed a Corrective Action Plan for a pump-and-treat system that would utilize engineered, enhanced bioremediation, but they recognize that a more complete understanding of the hydrogeology is needed for effective design of the actual treatment system.

Objective #1

Provide preliminary characterization of the ground-water-flow system at Site 71.

Approach: Construct a conceptual model and a two-dimensional, steady-state numerical model using MODFLOW. The model will be calibrated using existing data. The head match may be somewhat crude and there may be a larger percent error compared to what would be possible if more funding was available to construct a "finer-tuned" model. However, this model will meet the Navy's short-term needs because it will simulate the general characteristics of the hydrogeologic system. An Administrative Letter Report that provides a summary of the results of the modeling effort will be published.

Objective #2

Determine the effects of tidal loading on ground-water-flow directions and velocities, on residence time of the plume, and on mass transport from the plume into the Anacostia River.

Approach: Using SUTRA (Saturated Unsaturated Transport), develop a theoretical one-dimensional stream-tube model that is oriented perpendicular to the Anacostia River. Long-term transport will be simulated. Simulations will be run under a natural gradient (no tidal loads) and with tidal loads. Simulate direction and magnitude of flow under these two conditions. Simulate solute transport under these two conditions. Provide recommendations on what would be required to make the theoretical models more realistic.

Objective #3

Provide evaluation of the OPTECH tidal study concerning tidal influences at the Washington Navy Yard and the Anacostia Naval Air Station.

Approach: This will include an evaluation of the existing data, identification of data gaps, an evaluation of whether the data were properly used and plotted, a discussion of conclusions that can be drawn from the existing data, and recommendations for further work, if necessary.

Objective #4

Determine if the Survey's BIOMOC model could be used to help anticipate the reactions that will occur with the proposed treatment system, used in the design the pump-and-treat system and enhancements, and used to help manage the system once it is operational.

Approach: Discuss the feasibility of using BIOMOC with Barbara Bekins, a co-author of the model. If so, develop a short proposal to do this.

Objective #5

Provide technical input on bioremediation aspects of the Corrective Action Plan for Site 71.

Approach: After studying the Corrective Action Plan, meet internally to evaluate it. Compile comments and meet with representatives from the Navy.