Fall 1997
Superfund Cleanup Moves Forward
by Peter Strauss
The Silicon Valley Toxics Coalition continues to be active in monitoring the cleanup activities at the Moffett Field and Middlefield-Ellis-Whisman (MEW) Superfund sites in Mountain View. The contaminated groundwater plume from these sites extends nearly one mile from south of Highway 101 to the edge of the wetlands that border the salt water marshes of the San Francisco Bay. In 1993, SVTC was awarded a Technical Assistance Grant from the U.S. Environmental Protection Agency (EPA) to hire a Technical Advisor to assist us in this effort. SVTC established a Community Advisory Board (CAB), composed of residents from the impacted communities of Mountain View, Sunnyvale and Palo Alto, to advise us on the clean-up of both Moffett Field and the MEW sites. The U.S. Navy has a Restoration Advisory Board, known as a RAB, that provides the Navy with advice about the cleanup of Moffett Field. This group is composed of state and federal regulators, community members, including SVTC, and the main parties involved in the clean-up. However, the MEW companies, while having a representative on the RAB, do not fully participate in informational exchange.
Moffett Field Activities
Moffett Naval Air Station was taken over by NASA in July 1994 under the Base Realignment and Closure Act. The Navy, however, remains in charge of Superfund cleanup activities at Moffett Field. Because of concerns raised by both the CAB and the community members of the RAB, the largest landfill at Moffett is being capped in a manner that is equivalent to techniques required of municipal facilities. A smaller landfill is being excavated and consolidated into this bigger landfill. The treatment systems (i.e., air stripping and granular activated charcoal) have been designed.
Over the last year, we have focused our efforts on the cleanup of the landfills at the base, and the preparation of critical documents that must be completed before final plans are implemented. These documents include the Site-Wide Feasibility Study (SWFS) and the Site-Wide Ecological Assessment (SWEA).
The Site-Wide Ecological Assessment (SWEA) is the study that defines potential risks to flora and fauna at Moffett, and consequently defines the areas that need to be remedied. This has been an ongoing study that lasted about three years, and the results are still controversial. Both EPA and Cal/EPA are critical of the draft document. Their criticism focuses on conclusions in the SWEA. Essentially, the agencies believe that risks to ecological receptors (the plants and animals exposed to toxic chemicals) are understated by the Navy, thereby underestimating the amount of cleanup necessary at the site. This, along with a recently prepared Station-Wide Human Health Risk Assessment will define the areas that will require additional cleanup.
The SWEA focused on the wetland areas, which are the richest habitats. It also analyzed species such as the burrowing owl and the American kestrel. For surface water and sediment organisms, PCBs, pesticides, and metals appear to contribute risk in these areas, with PCBs and metals being the driving force. Species studied were the black-necked stilt, great blue heron, mallard duck and the salt harvest mouse (a federally endangered species). For upland areas, the kestrel and the burrowing owl were studied. Hazards for the great blue heron were the highest among the wetland species.
A number of remediation strategies activities were evaluated to mitigate the ecological and human health risks that were identified. For sediments, aside from institutional controls, the strategy is to excavate all sediments above a certain toxicity level, with treatment and backfilling (or off-site disposal) combined with capping sediments that are still in excess of certain levels. For the newly discovered landfill, only a multi-layer cap was considered. The multi-layer cap would be similar in design to the landfill north of the airstrip (OU1).
Nevertheless, the SWFS is the controlling document, and is not considered complete. It is prelude to the Record of Decision (ROD) for the entire site. This is an important document, and one where the community still has an opportunity for input.
MEW Activities
We have focused on reviewing measures at the three Superfund sites south of Highway 101, which are responsible for much of the contaminated water flowing beneath Moffett. The ROD was signed in 1989 and set cleanup standards for soils and groundwater. This ROD controls remediation activities for what is called the &qt;regional plume.&qt; Source control activities (pump and treat systems and slurry walls) act as barriers for containment migration. After our Technical Advisors commented, designs of the system to clean up the regional plume were modified and approved by the EPA in 1995-96. This area is the main source of contamination at Moffett. Until this is cleaned up, there will be a continued threat of contamination to the wetlands. There is substantial redevelopment of contaminated properties in the MEW area. It is SVTC's understanding that new owners such as Netscape, will not be responsible for cleanup, so long as they do not contribute to the contamination.
Since approval of the ROD, our focus has shifted to exploring regulatory initiatives that could influence the long-term cleanup. These include:
- the State Water Resources Control Board's "Containment Zone Policy" (which grants a waiver to cleaning up the groundwater at a site, so long as a negotiated boundary is established in which the contaminated groundwater is contained;
- EPA's granting of Technical Impracticability Waivers (where the polluter can demonstrate that additional cleanup is no longer economically or technically feasible); and,
- a push toward "natural attenuation" (where contamination is allowed to naturally breakdown and diffuse, thereby requiring no additional action except for monitoring) as a technical solution to groundwater cleanup.
This last initiative has been gaining strength in state regulatory circles, and it is SVTC's opinion that it could become the solution of choice. This is particularly bothersome after we learned that a similar strategy was adopted for petroleum contamination, only to find there are gasoline additives (like MTBE) in the groundwater that don't break down. At the very least, we should insist that before this strategy is adopted at any site, those proposing this alternative, demonstrate and verify that this biological breakdown is occurring.
Peter Straus is SVTC Technical Assistant whose services are made available to SVTC through an EPA Technical Assistance Grant.
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