Multi-Party Superfund Site
Northern California
At a high-profile, multiple responsible party Superfund site in Silicon Valley, our client’s site has been subjected to rigorous vapor intrusion (VI) evaluation requirements and considerable community and media scrutiny. Weiss recently implemented requirements stemming from a VI-specific Record of Decision (ROD) Amendment issued in 2010, including building surveys and employee interviews, several rounds of indoor air sampling under varying conditions, and sealing foundation slab penetrations that were identified as potential conduits for VI. Based on our evaluation, the site qualifies as a “Tier 3A” site, meaning no engineered remedy is required for VI. Weiss will develop a long-term monitoring program for United States Environmental Protection Agency (USEPA) Region 9 approval.
The positive results of this VI evaluation are primarily due to the aggressive groundwater remediation performed at this site, including a multi-stage enhanced in situ bioremediation (ISB) program initiated in 2005. These efforts and the VI assessment bring this site closer to monitored natural attenuation (MNA) status than any other within the large multi-party plume. Our client has received positive publicity from local and national media for our work at this site.
Since late 2013, Weiss has been working closely with the USEPA to develop and implement a supplemental soil gas and indoor air sampling program to monitor the effects of ISB in site groundwater on trichloroethene (TCE), vinyl chloride, and methane in indoor air. Heightened concern about potential effects of TCE on fetuses in the first trimester makes short-term increases in indoor air TCE during ISB of special concern. Being the first ISB project in the area, this sampling program will likely form the basis for future projects at other sites.
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