NAVFAC Washington Chooses Bacteria to Decontaminate Groundwater and Soil on Washington Navy Yard

Photo By Matthew Stinson | Wells were installed in the footprint of Buildings 46 and 67 on Washington Navy Yard to decontaminate soil and groundwater. Well heads are temporarily recessed and buried to prevent damage during construction. Here, a rotosonic drill rig drills injection wells in Building 67.  

DC, UNITED STATES

06.09.2021

Story by Matthew Stinson 

Naval Facilities Engineering Systems Command Washington

The Naval Facilities Engineering Systems Command (NAVFAC) Washington environmental team, in partnership with Public Works Department Washington, investigated and expeditiously staged a remediation plan for contaminated legacy soil and groundwater on the Washington Navy Yard (WNY). The remediation plan will utilize bacteria to decontaminate soil and groundwater in the footprints of Buildings 46 and 67, the future Operational Archives and Repository Complex for Naval History and Heritage Command.

Buildings 46 and 67 are historic structures on WNY. Built in 1840 and 1899 respectively, they served many uses over the past century and a half, including as the Navy brig used to hold the co-conspirators of the Lincoln assassination, an industrial manufacturing space for naval guns, and most recently as an art gallery. But it was their past industrial history in the mid-20th century that likely resulted in a highly concentrated area of soil and shallow groundwater contamination with the degreasing solvents tetrachloroethene (PCE) and trichloroethene (TCE) underneath the buildings.

On Aug. 5, 2021, NAVFAC Washington broke ground on the project to renovate Buildings 46 and 67. The project, budgeted at $41 million, consists of a multi-faceted complex that will house the Navy’s Operational Archives, the Department of the Navy Library and Rare Book Room, Navy Art Collection, and the Underwater Archeology Conservation Laboratory. In October 2020, the construction contractor discovered contamination beneath a crawl space on site and characterized the soil and groundwater for disposal and dewatering in preparation for installation of a new micropile foundation for these historic buildings.

NAVFAC Washington Environmental was quickly notified and realized the ramifications of this finding. It was both the likely source of a known large plume of PCE and TCE that was being characterized in the deep groundwater in that part of WNY and a potential source of vapors that could cause indoor air issues in the new building. Over the winter, the environmental team from NAVFAC Washington Core combined efforts with Public Works Department Washington Environmental and Facilities Engineering teams, along with contractors CH2M and Grunley Construction, to tackle the issue all while maintaining renovation efforts.

NAVFAC was able to pinpoint the continuing contaminated source as the soil around two former concrete parts-cleaning tanks, situated in an unused and forgotten crawl space. The tanks had been abandoned in place and covered over with a concrete slab. The source area of the concentrated contamination was soon to be covered by the renovated building and revert to a crawl space, leaving just a six-week window from mid-January until the end of February to take action without significantly delaying the project.

The Navy and their contractors first evaluated and dismissed excavating the contaminated soil because the necessary excavation depth of 12 feet seriously risked undermining the foundations of the walls of the historic buildings, and any elaborate shoring plan would take much too long to design and implement. Thermal treatment, which would heat the ground to a boil to remove contamination through vaporization, was evaluated as an option, however there were reservations about the effects of such high temperatures on the structural integrity of the newly installed micropile foundation. The Navy ultimately decided on the approach of biological remediation.

Biological remediation required drilling a series of injection wells throughout the contaminated soil and groundwater zone in the former crawlspace of the building. These wells will then be used to inject material such as vegetable oil and bacteria that are specifically acclimated to break down PCE and TCE into harmless by-products. The vegetable oil is used by the bacteria as food to exponentially increase their population. Injection well installation was completed March 1, allowing the renovation contractor to resume work with minimal delay. The actual injection will be initiated later this year once the heavy construction in the contaminated portion of the building is completed. Mitigation measures, including vapor barriers and a sub-floor ventilation systems to prevent vapors from migrating from the soil and groundwater into the new building is being integrated into the design of the building floor slab.

Teamwork and clear communication between the various NAVFAC teams and their contractors allowed for the successful implementation of the plan to address contamination and to protect human health and the environment. Lastly, this effort minimized immediate cost impacts to the project while saving the Navy considerable costs over the long term.

By Paula Gilbertson

• Date Taken: 06.09.2021
• Date Posted: 06.09.2021 13:23
• Story ID: 398491
• Location: DC, US