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_ t i 1 Mr. Robert Trommer Page 5 of 7 I Comments on CUF Site Closure Recommendations for Various Sites March 3, 2010 With a favorable report, the EHD should be able to start closure process and estimates,final closure will be achieved in six to nine months. Claim No. 14118 - 444 Mossdale Road, Lathrop Closure for this site is delayed'. due to problems with the vapor intrusion evaluation. The consultant utilized soil data for the evaluation ignoring some highly impacted samples and overestimating the distance of the samples used from the existing building. No justification for a 'safe' distance between impacted soil and an existing building was .provided. As stated above for another site, the EHD would like to close this site and believes it should be closed, but as .vapor intrusion has been identified at the State level as a potential health issue that must be addressed before closing a site, the EHD has been attempting to exercise due diligence by acquiring defensible data that demonstrates that the health risk posed by potential vapor intrusion from: residual contamination is at or below an acceptable level. The EHD expects this site may be closed in three to six months. Claim No. 14328 - 1501 W. Charter-Way The closure :process for this site has been initiated, and notification documents for the CVRWQCB are in preparation. The site monitoring wells will need to be destroyed. The EHD estimates three to six months will be required to. complete the closure process for this site. Claim No. 14349 - 517 W. Fremont Street, Stockton In the 2008 CUF letter, the CUF recommended initiation of groundwater remediation. In 2009, the CUF recommend site closure although no remediation had been conducted. The EHD had directed implementation of groundwater remediation. and set several dates that were not complied with. To date, there 'las been no attempt at active remediation. The plume of impacted groundwater on the, site is delineated, but the EHD believes the contaminant concentration; in well MW-3 to be too high for closure consideration without remediation. Benzene was present in MW-1 in June 2009 at 4,600 pg/L, TPHg was present at 23,000 pg/L, and 1,2-dichloroethan (1,2-DCA),at 63 lag/L. The EHD has approved a work plan to install and test a soil vapor extraction (SVE) well and an in-situ air sparge (IAS) well. As no remediation has yet been attempted on this site, the EHD believes it would be very beneficial to make such an attempt and reduce the contaminant mass and accelerate the return to applicable water quality goals. Claim No. 14353 - 3400 Newton Road Stockton xr This site has an approved work plan(approved by EHD letter dated July 29, 2009) to conduct a soil vapor extraction test on monitoring wells MW-1. and MW-8, which the EHD expects will address soil underlying the former tank pit impacted by methyl tent-butyl ether (MTBE) at concentrations as high as 5.2 milligrams per kilogram (mg/Kg). Groundwater in MW-1 becomes impacted when groundwater elevation rises into the well and encounters impacted soil currently in the vadose zone. Groundwater in the surrounding wells is usually not impacted; however there is a domestic well on the site approximately 134 feet from the former tank pit. The EHD believes for very little expense the MTBE mass in soil can be reduced which will greatly reduce the probability that the on-site domestic well will become impacted during a period of high j groundwater elevation and the site is no longer monitored. On January 29, 2010, the CUF changed the priority class of the site from Class "C" to Class "B." The EHD anticipates that this will relieve the delay of work on this site and enable the test to be Comments on CUF Site Closure Recommendations 0310.doc