Future
Federal Office Building Site
Washington, D.C.
CGS was retained by Greenhorne & O’Mara, Inc. to
assist its
US Government client in developing a contaminated parcel of land in a
prime downtown Washington, DC location for a federal office building.
The Site was contaminated with petroleum from leaking underground
storage tanks (USTs). CGS performed a Risk Assessment according to
District of Columbia Risk- Based Decision Making (RBDM) policy and
USEPA Risk Assessment Guidance for Superfund (RAGS) to evaluate
potential risks to human health from subsurface contamination. The Risk
Assessment was utilized to establish remedial endpoints and determine
whether institutional controls were required for the proposed Site
development. CGS designed a series of institutional control measures
that were incorporated into the engineered design of the building. CGS
prepared a Corrective Action Plan (CAP) based on the risk assessment,
and provided oversight during CAP implementation. Soil excavation
activities for the building subsurface structures were monitored to
segregate soil requiring disposal at a permitted facility, and to
ensure that the remedial endpoints were achieved.
Excavation proceeded until all
soil
with benzene concentrations exceeding the remedial endpoint was removed
laterally and vertically. During the Corrective Action, 78,800 tons of
contaminated soil was removed. A dewatering system removed and treated
over 43 million gallons of groundwater from the Site during the
remediation project. CGS conducted a post-excavation ground-water
investigation, which indicated that benzene concentrations in
groundwater were below the remedial endpoint calculated in the CAP. CGS
worked on behalf of the US Government to successfully expedite
components of the Corrective Action when unforeseen circumstances
inherent in older urban settings were encountered. Through innovative
problem-solving, the Corrective Action implementation proceeded, CGS
minimized the need for budget increases, and a No Further Action/Case
Closure status was authorized by the District of Columbia.
Groundwater Treatment System |
Contaminated Soil Excavation |
Excavation for Building
Foundation |
|
Former UST Area after Remediation |
ADDITIONAL PROJECT
SUMMARIES:
