SITE INFORMATION AND CORRESPONDENCE

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Working to Restore Nature 3164 Gold Camp Drive, Suite 200 Rancho Cordova, CA 95670 Phone: (916) 852-6690 Fax: (916) 852-6688 November 4, 1993 Mr. Chuck Carmel ARCO Products Company P.O. Box 5811 San Mateo, California 94402 Subject: Evaluation of the Depth to Groundwater Beneath ARCO Station No. 6100, 25775 South Patterson Pass Road, Tracy, California. Mr. Carmel: At the request of ARCO Products Company (ARCO), RESNA Industries (RESNA) collected depth-to-water measurements in the water-supply well at the subject site. The purpose of the work was to evaluate whether groundwater beneath the site is within the interval of soil affected by gasoline hydrocarbons. The location of the site is shown on Plate 1, and the location of the water-supply well is shown on Plate 2. On August 24, 1993, after the well was turned off for approximately 1/4 hour, a technician from RESNA measured the depth to water in the water-supply well to the nearest 0.01 foot by lowering the probe from a Solinst water-level indicator through the access plug on top of the well casing cover. The water level was 58.51 feet below the access plug. The technician also monitored three vapor extraction wells to check for the presence of groundwater; groundwater was not detected in the three wells. Well construction measurements and depth to water measurements are shown on Table 1. The site is relatively flat with an approximately 2-1/2 foot change in elevation. The depth to the first saturated unit (depth to first encountered groundwater) beneath the site is not known. The depth to first encountered water is not indicated on the Department of Water Resources driller's log for the water-supply well (June 26, 1969); however, the log does indicate that the depth to water after development was 100 feet below surface grade (bsg). During RESNA's drilling operations at the site, groundwater was not encountered; 0830mar 300416