MOUNTAIN VIEW, CA
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Teledyne Semiconductor has operated as a semiconductor manufacturer at this 1-acre site since 1962. In 1982, Teledyne reported to the California Regional Water Quality Control Board (CRWQCB) that soil and groundwater were contaminated with solvents from an underground solvent storage tank. The State inspected the site and found that contaminants had migrated north of the site and affected approximately 50 private domestic wells. Furthermore, contaminated groundwater that migrated north from another NPL site, Spectra-Physics, Inc., merged with the contaminated plume of the Teledyne site. The two firms are cleaning up the sites jointly. These sites are among the 28 sites in the South Bay Area of San Francisco. Facilities at these sites have used a variety of toxic chemicals, primarily chlorinated organic solvents, which have contaminated a common groundwater basin. Although the sites are listed separately on the NPL, the EPA intends to combine cleanup activities at some of the sites as part of an area-wide approach to the contamination. The site is located in a densely populated, urban area. Approximately 189,000 people live within a 3-mile radius of the site. The distance from the site to the nearest residence is 200 feet.
What Has Been Done to Clean Up the Site?
The parties responsible for the environmental cleanup (Potentially Responsible Parties) have been conducting soil and groundwater cleanup activities for over 30 years. Groundwater extraction and soil vapor extraction have removed thousands of pounds of VOCs from both groundwater and soil. Over the last several years, a new cleanup method was tested and evaluated to speed up the groundwater cleanup. This evaluation is known as a Revised Focused Feasibility Study (Revised FFS),and is a major milestone for the Site. EPA and the Regional Water Board are close to completing their approval of the FFS, pending public comments. Approving the Revised FFS will pave the way to officially changing the cleanup plan for the Site from groundwater extraction to the bioremedia-tion remedy. The new method uses bioremediation - a process whereby microorganisms found naturally underground are stimulated with nutrients to clean up the contamination groundwater. This new cleanup method has greatly improved groundwater quality across the former Teledyne property and has the potential to greatly reduce the time it will take to reach the cleanup goals in the impacted areas. We will issue a public comment fact sheet to invite your comments within the next few months.
EPA has conducted several five-year reviews of the site’s remedy. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that EPA could not determine the protectiveness of the remedy until it conducts a vapor intrusion assessment.
Additionally, the most recent five-year review (reviews that ensure that the remedies put in place protect public health and the environment) concluded that EPA could not determine human health protectiveness of the remedy until it conducts a vapor intrusion assessment. There is some limited potential for VOCs in groundwater to move as vapors through soil under a building, pass through cracks and other openings in the foundation or flooring, and then enter the indoor air. This process is known as vapor intrusion. To determine if vapor intrusion is occurring at levels unacceptable to the EPA, the EPA and Regional Water Board have been working with the Potentially Responsible Parties to conduct indoor air testing in homes and businesses over the TCE plume from the Site that might be affected (See Fact Sheet Figure 3 – Indoor Air Sampling Study Area). The process for testing TCE in indoor air is not disruptive and involves placing a small sampling device inside a home (such as on a shelf) and underneath the building in the crawlspace and left untouched for one to two weeks. There is no cost to owners or tenants for the sampling.
What Is the Current Site Status?
The Fourth Five-Year Review was completed in Sept. 2014, concluding that the vapor intrusion indoor air investigation needs to be completed before a “protectiveness determination” can be made. The following issues and recommendations were identified in the report:
- The performance of the selected remedy in the Record of Decision, groundwater extraction and treatment, has declined and new remedial actions are being investigated.
Recommendation – Complete a Record of Decision Amendment or prepare an Explanation of Significant Differences selecting new remedial actions and including updated institutional controls.
- The Five-Year Review vapor intrusion evaluation indicated that the subsurface-to-indoor air pathway is a concern at the site.
Recommendation – Continue to monitor and provide mitigation for vapor intrusion, including step-outs to lower concentration areas of the shallow TCE groundwater plume.
The Five-Year Review further stated the following:
A protectiveness determination of the remedy at the Teledyne Semiconductor and Spectra-Physics, Inc. Joint Superfund Sites cannot be made at this time until further information is obtained. Additional vapor intrusion assessments must be conducted to determine if indoor air pathways are complete. When unacceptable levels are encountered in a particular building, mitigation plans are developed and implemented to ensure that levels of volatile organic compounds (VOCs) in indoor air are protective. It is expected that these actions will take approximately two years to complete, at which time a protectiveness determination can be made. To be protective in the long-run, a new remedy should be selected due to the declining effectiveness of the existing remedy.