ARCHIVED REPORTS_NOTICE OF INTENT FOR INSTALLATION, OPERATION AND MAINTENANCE OF AN OZONE INJECTION GROUNDWATER REMEDIATION SYSTEM

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1 ' The site-related groundwater monitoring wells are completed in at least two separate saturated sand ' lenses referred to in past documents as the shallow zone (MW-1 through MW-7, GWX-1 and VX-1), the intermediate zone (MW-8, MW-10 and MW-12) and the deep zone (MW-9, MW-11 and MW-13). Based on our review of the site hydrogeology, the intermediate zone is the same saturated sand lens as ' the shallow zone but with the wells screened at the base of the sand lens rather than across the top of the lens. The well construction details for the above listed wells are presented in Table 3. On July 17, 2007, we performed a soil vapor survey(SVS) at the Site that included direct-push vapor borings VP-1 through VP-24. We presented the results of the SVS in our October 12, 2007, report ' entitled Soil Vapor Survey and Human Health Risk Evaluation Report (SVS Report). On December 21, 2007, the Central Valley Regional Water Quality Control Board (CVRWQCB) ' cormnented that the risk evaluation did not include a Tier II risk assessment on TPH and that the maximum naphthalene laboratory method reporting limit (MRL) needed to be used in the risk ' evaluation rather than the standard practice of assuming one-half of the MRL. On July 2,2008, we submitted a Revised Human Health Risk Evaluation (HHRE)per December 21,2007, ' and February 5, 2008, directives from the CVRWQCB. The results of the revised HHRE show that there is not an excess carcinogenic or non-carcinogenic risk to human health under either a residential ' or comtnercial land use scenario due to the presence of potential contaminants of concern (PCOCs) in soil and groundwater beneath the Site. Based on the revised HHRE results, we concluded that no additional site investigation activities appear warranted for the Site. ' On October 13, 2008, we submitted the Third Quarter— 2008 Groundwater Monitoring Report and SVE, AS and Ozone Injection Pilot Testing Workplan (Workplan) to the CVRWQCB. The Workplan was conditionally approved by the CVRWQCB in a letter dated October 29, 2008. The CVRWQCB ' agreed with our Workplan's recommendation to decrease the sampling interval for wells hffA through MW-13 in a February 24, 2009, directive. The updated groundwater sampling program calls for analysis of TPHg, benzene, toluene, ethylbenzene, total xylenes (BTEX), fuel oxygenated ' compounds (FOCs) including methyl tert-butyl ether (MTBE), tert-butanol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether(ETBE)and tert-amyl methyl ether(TAME), 1,2 dichloroethane(1,2-DCA), ' naphthalene and ethanol in accordance with the following table: Well)ED Quarterly' Semi-Annual Annual 2"a and 4`h Quarters only) 4`h Quarter onl MW-1, GWX-1 MW-3 X MW-2 X MW-4 through MW-13, VX-1 X Project No.59183-06-02 -2- July 2,2009