Spring 2000
Can Moffett Ever Be Mended?
by Peter Strauss
The Silicon Valley Toxics Coalition continues to be active in monitoring the cleanup activities at the Moffett Federal Airfield (MFA) Superfund site in Mountain View. The contaminated groundwater plume from this and other adjacent sites extend nearly one mile from south of Bayshore Highway to the edge of the wetlands that border the salt water marshes of the San Francisco Bay. The Navy is nearing the end of the planning process for the cleanup of the site, and several important documents will be up for review and comment, followed by a public hearing. These include the Draft Station-Wide Proposed Plan and the Draft Station-Wide Record of Decision. Dates will be announced.
Moffett Naval Air Station was taken over by NASA in July 1994 under the Base Realignment and Closure Act (BRAC). The Navy, however, remains in charge of Superfund cleanup activities at MFA. Progress to date includes: capping of the largest landfill; operating groundwater treatment systems (i.e., air stripping and granular activated charcoal) for both the east side and the west side; and, operating the “regional groundwater treatment system” (so named because it treats groundwater that has migrated beneath MFA from sources south of the site, collectively known as the MEW Superfund site). Although there are several remaining pieces to the cleanup puzzle, the one that we feel is most important is the Station-Wide Plan. This focuses on the northern-most portion of Moffett, and takes account of channels and drainage systems that for years have fed into these once tidal wetlands. Contaminants include PCBs, metals (such as lead), and pesticides. The major concern is the effect that these residual contaminants will have on wildlife and the Bay Ecosystem.
Over the past two years, we have focused our efforts on making sure that the Navy plans to cleanup these contaminants so as not to harm ecological receptors (the plants and animals exposed to toxic chemicals). We took the position in comments on the underlying documents that the Navy understated the risks that these contaminants pose, thereby underestimating the amount of cleanup necessary at the site. We also do not believe that the remaining contamination should control future land-use; therefore we wanted the Navy to assume the most conservative (health-protective) scenarios. We are concerned that at some future time, the owner of the facility will decide to stop using the runways and the drainage system will no longer be needed. At that time, we would like for the future owner to re-establish the once tidal wetlands at the northern end of MFA. Because Cargill now maintains a series of levies for its salt ponds at the northern end of the base, the wetlands are presently fed by freshwater. However, the ecosystem contains hardy plants that tolerate high salt content such as pickleweed and the endangered species known as the salt-water harvest mouse.
The Navy agreed with us to use conservative ecological assumptions, but based its land-use scenario on keeping the freshwater wetlands. This has the effect of requiring a lesser amount of cleanup of PCBs, because no fish are present in the fresh water (and therefore birds will not be exposed to fish with high contaminant levels). The Navy has also taken the position that the PCBs and pesticides and metals are co-located, so that extracting sediments containing PCBs over a certain amount will also remove these contaminants. The Navy has not provided us with convincing evidence to support this assumption. The regulators have asked that the Navy institute an ecological monitoring plan to detect if the remedy is effective. We have yet to see this plan.
Peter Strauss is SVTC's Technical Adviser through
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