EPA has been asked to investigate tetrachloroethylene (PERC) contamination in Hyattsville (Chillum), Maryland and Washington, District of Columbia. PERC contamination was discovered during an on-going investigation of a gasoline-products release from a service station located in Hyattsville near the Chillum Perc property. The site under investigation includes a dry cleaning facility and a residential community. The dry cleaning facility is located in Maryland and is immediately adjacent to the Washington, DC border. Groundwater flow flows from Maryland into Washington, DC, and one or more plumes of groundwater containing PERC may be present beneath the local residential community.
A. January 20, 2003: EPA, START utilized a Geoprobe® direct-push device to advance hollow, carbon-steel drive rods at an angle beneath basement slabs of two residential structures. Geoprobe® Post-Run Tubing™ techniques, in which certified-clean Teflon™ tubing was placed through the rod string after it had been advanced to the desired sampling depth and retracted approximately 6 to 12 inches, were used as part of the sample collection process. The tubing was attached to a stainless steel end fitting, flanged on one end and reverse-threaded on the other, and subsequently threaded into a disposable drive point located at the bottom end of the drive rod string to create a vacuum. A vacuum pump was used to purge air from the tubing and collect samples in one-liter Tedlar bags. Three samples (including one field replicate) were collected and forwarded via courier to Southwest Research Institute, in San Antonio, Texas.
B. February 3, 2003: EPA, START returned to the site to collect an additional three active soil vapor samples from beneath the basement slabs of two residential structures using methods identical to those used on January 20, 2003. Three samples (including one field replicate) were collected and forwarded via courier to Southwest Research Institute.
C. March 17, 2003: EPA, START attended a Executive Committee meeting at LaSalle Elementary School (in the vicinity of the site) to discuss activities and analytical results of active and passive soil vapor samples. Individual resident personal privacy was maintained at all times. Letter reports containing active soil vapor analytical results were hand-delivered to the owners of the four properties from which samples were collected. In addition, EPA offered to privately explain the concentrations reported in the letter reports to the individual property owners.
D. March 27, 2003: Letter reports containing passive soil vapor analytical results were forwarded via certified mail to the owners of the 29 properties from which samples were collected.
E. April 10, 2003: EPA forwarded START Technical Direction Document (TDD) to begin expanded scope of work in the residential area located south of the Chillum PERC property.
F. April 11-12, 2003: EPA and START traveled to the site to prepare for placement of SUMMA™ canisters in four residences. On April 11, 2003, EPA and START interviewed the owner of one residence who granted written access, discussed indoor air sampling rationale and procedures, and inspected indoor areas for potential household vapor sources. The owner of a second residence granted access and was interviewed on April 12, 2003. All identified potential household vapor sources were temporarily removed from indoor areas. Two of the residences at which EPA planned to place SUMMA™ canisters could not be reached to gain access for this sampling event.
G. April 14-15, 2003: EPA and START traveled to the site to place SUMMA™ canisters in the two residences from which access had been granted. On April 14, 2003, the SUMMA™ canisters were placed in unventilated basement areas at least 24 hours after removal of all identified potential household vapor sources. The sample was collected using a 24-hour, continuous-flow regulator affixed to the canisters. The canisters were forwarded to Datachem Laboratories, in Cincinnati, Ohio for analysis of volatile organic compounds (VOCs) by EPA Method TO-15.
H. April 18, 2003: EPA verbally contacted the two residents from whose property indoor air samples were collected to inform them of the preliminary analytical results received from the laboratory.
A. The expanded scope of work includes but is not limited to the installation of "nested" permanent soil vapor implants and pre-packed one-inch microwells, sampling of soil vapor using active techniques, and sampling and laboratory analyses of groundwater, sump water (where present), tap water, and indoor air (using SUMMA™ canisters). In addition, the Emergency Response Team's (ERT) Trace Atmospheric Gas Analyzer (TAGA) will be utilized to conduct real-time screening of specific individual homes and analyze active soil vapor samples. Sampling locations will be selected based on a risk-based assessment of previously collected data. The expedited sampling event conducted on April 14-15, 2003, during which SUMMA™ canisters were placed in the homes of two residences is also part of this most recent scope of work. The two residences were selected based on an exeedances of the short-term soil screening level for PERC in soil vapor samples collected from beneath the basement slabs. Though no analytical data were collected from the adjoining residences of each duplex at which a short-term exceedence was encountered, EPA and START will collect samples from these residences since the each side of the duplex shares the same basement slab. Field exercises are planned for July/August, 2003.
B. Attend public meetings and prepare presentations of completed, on-going, and planned activities in response to the PERC release.
C. Prepare sampling and analysis plan for expanded work.
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