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UPage 3 of 7Mr. Robert Trommer Comments on CUF Site Closure Recommendations for Various Sites March 3,2010 Claim No. 3484 - 2360 East Street, Tracy This site is in the closure process needing only monitoring well destruction. The EHD is awaiting the permit applications for the yell destructions and anticipates site closure in one to three months. Claim No. 679 - 5814 E.Charter Way, Stockton This site is in the closure process needing only monitoring well destruction. The EHD anticipates site closure in one to three months. Claim No. 7709 - 2969 Loomis Road. Stockton . As the EHD commented in May 2009 to the CUF five-year review closure recommendation, there are several factors that lead the EHD to consider closure of this site to be premature at this time. Those factors are as follows: • All eight monitoring wells have groundwater above the wells screened intervals (as much as twenty feet in MW-1). There appears to be a correlation between depth-to-water and concentrations detected in groundwater from the monitoring wells - as depth-to- groundwater increase, diesel concentrations also increase. • The EHD is concerned about the sudden drop in diesel concentrations reported in groundwater collected from MW-4, MW-5, and MW-7 in April 2008. The significant decrease coincides with a change in laboratories. During the October 28, 2008, sampling event, groundwater samples collected from MW-5 and MW-7 were sent to two different laboratories, and the results from the two laboratories were significantly different. The verification laboratory reported diesel at 2,210 micrograms per liter (ug/L) in MW-5 and 7,480 ug/IL in MW-7, while the laboratory that had been detecting markedly lower concentrations reported diesel at 580 ug/L in MW-5 and 620 ug/L in MW-7. • Based on the soil contaminant mass for diesel estimated.to be approximately 27,000 gallons (168,000 pounds) at the end of 2005, our department believes it prudent to try to remediate the diesel contamination prior to closing this site, especially since a light sheen continues to be reported in monitoring MW-4 and MW-5. Three dual-phase extraction wells with well screens that intersect the groundwater table were installed on the site in January 2010, but have not been developed or sampled as of yet. Considering that the characterization of shallow groundwater has not yet been completed and that an estimated 168,000 pounds of diesel is believed to be impacting soil and no remediation has yet been attempted, the EHD believes it would be beneficial to attempt some site remediation, reduce the contaminant mass and potential toxicity to microorganisms, and accelerate the return to background conditions. Claim No. 8509 - 1207 S. Aurora Street, Stockton This site is in the closure process needing only monitoring well destruction. The EHD anticipates site closure in one to three months. Comments on CUF Site Closure Recommendations 0310.doc