SITE INFORMATION AND CORRESPONDENCE

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• March 11,2010 Page 2 of 2 Eric Mar 3032 E. Waterloo Road, Stockton, CA being approximately 1,000 feet further down-gradient may be at risk. Much uncertainty attends this concern, but the EHD believes you should be informed. Groundwater extraction (GWE) was initiated on the subject site in May 2003 to remove COCs from groundwater. According to the latest remediation report, between May 2003 and December 2009, GWE has removed an estimated 11,243 pounds of TPHg, 620 pounds of benzene and 1,180 pounds of MTBE from groundwater. Soil vapor extraction was initiated on the subject site in December 2006, and since then an estimated 32,814 pounds of TPHg have been removed from soil in the vadose zone. Despite the removal of approximately 44,000 pounds of TPHg from soil and groundwater, the dissolved concentrations of TPHg and other COCs have not declined significantly in the core area wells. The EHD has been informed that Well #75 has been regularly monitored for MTBE since August 1996 with no detection of the compound. Chemicals variously detected in the well water include tetrachloroethylene, trichloroethylene, 1,2 dichloropropane. You stated that Well #75 would be sampled and analyzed for volatiles, including MTBE, in the near future, and that you would provide the analytical results to the EHD, which will be greatly appreciated. As more information is developed regarding the subject site plume and its potential to impact Well #75, the EHD will keep you informed. You may contact Nuel Henderson at (209) 468-3436 or by email at nhendersonsicehd.com if you have any questions. Sincerely, -4140//t.i Nuel C. Henderson, Jr., PG Adrienne Ellsaesser, REHS Engineering Geologist Acting Program Coordinator c: James Barton, PG - CVRWQCB - 11020 Sun Center Dr. #200, Rancho Cordova, CA 95670 William Little, PG — AGE —837 Shaw Road, Stockton, CA 95215 Joe Spano, PE — CDPH DDWEM-31 East Channel St., Rm 27, Stockton, CA 95202 Eric Mar Letter 0310