|From:||Lenny Siegel <email@example.com>|
|Date:||28 Dec 2004 00:22:13 -0000|
|Subject:||[CPEO-MEF] El Toro and the potential for vapor intrusion|
EL TORO AND THE POTENTIAL FOR VAPOR INTRUSION Lenny Siegel December 27, 2004 In January, 2005, large portions of the former El Toro Marine Corps Air Station go up for sale. Because El Toro is a "Superfund" National Priorities List site, with significant trichloroethylene contamination, I have been asked whether I consider vapor intrusion a risk either to the redevelopment plans or to the people who will live on or otherwise use the property after transfer from federal ownership or control. After reviewing a series of documents and visiting the base, I have concluded that indoor air contamination is unlikely to be a problem at El Toro because the land known to be contaminated with TCE is planned for open space. Furthermore, the potential for vapor intrusion should not impact the property auction because the TCE-contaminated sites have been carved out of the sale parcels - they are being offered for lease. Still, the Navy and regulatory agencies could take steps, such as air sampling and the imposition of vapor-intrusion-specific institutional controls, to enhance the level of protection for future residents and users of the property. El Toro consists of nearly 5,000 acres of land in Orange County, California. It was the Marines' principal jet fighter base on the west coast. When El Toro was approved for closure in 1993, Orange County initially planned to convert it into a commercial airport. However, residents of adjacent communities objected, and they eventually won the political battle. El Toro will be split among a federal enclave, a "Great Park," and residential and commercial development. For the Navy, El Toro represents an innovative, though not unprecedented approach to base closure property disposition. Instead of transferring lands to a reuse authority and completing a series of public benefit conveyances, it has divided the non-federal portion of the base into four sale parcels. In cooperation with the General Services Administration, it will auction those parcels on the open market. It will be the responsibility of the buyers to make land available for public benefit uses, as prescribed in the city of Irvine's planning documents. See http://www.heritagefields.com/ for details. The sale plan has national significance, not only as a precedent for future sales - though it follows a smaller sale at nearby Tustin Marine Corps Air Station - but because it could generate more than $1 billion in revenues. The Navy plans to use that money to fund its Base Realignment and Closure activities, including environmental cleanup. However, El Toro does not follow the Navy's model for privatization of cleanup. Because the base is relatively far along in the cleanup process, the Navy will retain management of the cleanup even after property transfer. El Toro has two major volatile organic compound (VOC), primarily TCE, source areas: Site 16 and Site 24. Both have contamination of soil, soil gas, and "shallow" groundwater, but in this case "shallow" is more than 150 feet deep. Site 24 is the source of a three-mile-long off-post plume, but fortunately the plume dives under a shallower water-bearing zone as it leaves the property, thus posing no threat of vapor intrusion to neighboring residents. The Navy has removed significant quantities of VOCs from both sites using soil vapor extraction. It is treating the off-post plume (from Site 24) in cooperation with local water districts. The selected remedy for Site 16 is monitored natural attenuation with institutional controls. In June 2004, the Navy's contractor, Bechtel Environmental, completed a technical memorandum evaluating indoor air risk above Sites 16 and 24. Using soil gas measurements and standard modeling calculations, Bechtel and the Navy concluded: "Total cancer risks at Sites 16 and 24 using both U.S. EPA and Cal/EPA toxicity criteria for residential and industrial scenarios are acceptable, or fall with the 10^-6 to 10^-4 risk range that may be acceptable depending on site-specific and other factors considered appropriate for risk management decisions." Among the detailed findings, they found, "The estimated cancer risk for a hypothetical resident adult exposed to indoor-air COPCs [chemicals of potential concern] at Site 16 for 350 days a year over 30 years was quantified at 3.2 x 10^-6 (using U.S. EPA criteria) and 5.7 x 10^-8 (using Cal/EPA criteria)." It also concluded, "The estimated cancer risk for a hypothetical resident adult exposed to indoor-air COPCs at Site 24 for 350 days a year over 30 years was quantified at 7.8 x 10^-6 (using U.S. EPA criteria) and 1.3 x 10 ^-8 (using Cal/EPA criteria)." The provisional U.S. Region 9 EPA criterion for TCE is significantly more stringent that the promulgated California level. In my view, those numbers - placing cancer risk above one in a million using U.S. EPA's 2001 draft toxicity assessment - are neither cause for panic nor reassuring enough to simply dismiss the potential for vapor intrusion. That is, the modeled levels of TCE in air are high enough that more sampling, including indoor and outdoor air, should be conducted. Evidence elsewhere shows that the model often both underpredicts and overpredicts air concentrations, so levels that even approach the health standard should trigger sampling. I do not, however, consider the potential for vapor intrusion at El Toro to be a showstopper. The Navy has carved out, from the sale parcels, the most contaminated areas, including Sites 16 and 24 as well as buffer zones or at least 300 and 500 feet, respectively. Those properties will be leased and conveyed only after remedies are in place. Of course, the lease properties are slated for reuse and will be open to the public. Still, the risk of indoor air exposures is minimal because no residences will be built in those areas. The site 24 carve-out will include an "Open Space - Exposition Center," and "Open Space - Sports Park," and an Orange County "Institutional" use. I don't know exactly what types of structures those entail, but I assume the people won't be in those areas around the clock or even for long-term full-time work. That is, the marginal risk that might be present will be mitigated by the absence of structures. To reinforce that assumption, I believe that the current land use plan should be reinforced with enforceable institutional controls. Structures in VOC-contaminated areas should be prohibited or restricted. Restrictions could include the type and duration of use, or a requirement to install inexpensive passive mitigation elements - such as impermeable slab liners - during construction. There should be continuing monitoring to ensure that the restrictions remain in place as long as the contamination is present Furthermore, in the absence of sampling, I am concerned that emissions from these plumes might generate, as I believe has happened in my own community, an outdoor toxic cloud that could be a source of continuing low-level exposures in nearby areas slated for housing or, since it's already in place, the California State University-Fullerton campus annex near Site 16. Based on the limited data that is available, I doubt that there is a serious problem, but in the absence of actual air sampling I'm not prepared to tell students or prospective residents that everything is OK. As I've argued elsewhere, outdoor air contamination from subsurface sources can't be resolved through mitigation , but it may be a reason to modify remedial strategies to accelerate removal or degradation of soil or groundwater contamination. Finally, some members of the local community, as well as consultants for the city of Irvine, have argued that the Navy and the regulatory agencies may have missed other important sources of contamination on the 5,000-acre base. I have seen no evidence that this is true, but given the experience at other closing bases being switched from industrial to residential use, I think it's likely that more problems will be found when demolition, excavation, and construction occur. At that point, it will be necessary to evaluate whether any of those new sources pose a risk of vapor intrusion. Given the Navy's long history of professional investigation at El Toro, I don't expect any new source to be as large as Site 24 or even Site 16. In summary, I am not satisfied with the Navy's outright dismissal of vapor intrusion - to indoor or outdoor air - as a risk at El Toro. I think it's unlikely to be a serious problem, but I believe air sampling is necessary before ruling it out. The entire situation seems to be saved by the reuse plan and the division of the property between sale and lease parcels. The sections most likely to be sources of VOC vapors are not being sold, and they are not planned for continuous human presence. Measures, such as institutional controls, should be implemented to keep it that way. -- Lenny Siegel Director, Center for Public Environmental Oversight c/o PSC, 278-A Hope St., Mountain View, CA 94041 Voice: 650/961-8918 or 650/969-1545 Fax: 650/961-8918 <firstname.lastname@example.org> http://www.cpeo.org _______________________________________________ Military mailing list Military@list.cpeo.org http://www.cpeo.org/mailman/listinfo/military
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