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Mr Robert Trommer Page 7 of 7 Comments on CUF Site Closure Recommendations for Various Sites March 3, 2010 Claim No. 17042 - 15406 S. Tracy Blvd, Tracy This site has persistent moderate TPHg , and low ethylbenzene and xylenes contaminants in one well , MW-4. Wells toward the north, east and south are not impacted; there are no delineating wells toward the west. A domestic well is located approximately 135 feet southwest of MW4. In November 2009 limited groundwater extraction (GWE) was implemented utilizing MW-4. Approximately 15, 000 gallons were extracted from the well . Since then the well has been monitored monthly; concentrations were reduced, but may be rebounding - The consultant plans to complete the rebound testing with the March sampling event and then prepare a report of findings. The plume appears to be of limited extent, except toward the west, which is not characterized. Significantly impacted soil has not been encountered on the site There does not appear to be a significant contaminant mass present, but the contaminants are persistent and there is a domestic well to protect. The EHD will issue a directive to prepare a site closure summary report, addressing plume delineation and evaluation of vapor intrusion and health risk issues, threat to the domestic well, and other site closure concerns. If a favorable report is received, the EHD anticipates site closure in nine to twelve months- Claim No. 17179 - 15 E. Grant Line Road, Tracy Dissolved contaminant concentrations have declined to levels suitable for site closure consideration The consultant has recently obtained grab groundwater samples to complete the lateral and vertical delineation of the site, and the results are pending . The EHD will direct completion of a vapor intrusion evaluation . Upon receipt of the results of the recent grab groundwater investigation and the vapor intrusion evaluation, the EHD will initiate the site closure process if warranted by the additional information. The EHD anticipates site closure may be obtained in six to twelve months. Summary The EHD will be moving these sites to closure as rapidly as possible. The EHD has responded previously to the CUF on these sites in response to the five-year reviews and the annual updates. Direct comments from the CUF technical staff on the concerns expressed on the more problematic sites above are requested (specifically Claim Nos. 8431 , 7709, 11775, 141180 14349, 14353, 15211 , 15890, and 17042) - An EHD representative is available to meet with your technical staff if that would be helpful If you need more information to complete your evaluation of these cases, please contact Nuel Henderson, Engineering Geologist, at (209) 468-3436, or nhendersonna.sicehd . com . Sincerely, Nuel C. Henderson, Jr. , PG Adrienne Ellsaesser, REHS Engineering Geologist Acting Program Coordinator i Comments on CUF Site Closure Recommendations 0310.doc