SITE INFORMATION AND CORRESPONDENCE

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*ftwo� %.001 Le UIINICXj—IIRNfI LO Ms. Linda Turkatte 6 May 1992 Page 3 each analyzed for Total Petroleum Hydrocarbons as gasoline (TPH-G), and benzene, toluene, ethylbenzene, and xylenes (BETX). TPH-G and BETX were all below the laboratory's limit of detection for these compounds. These results were forwarded to the local Air Pollution Control District by Elder Engineering in their letter of 22 November 1991. The letter requested an exemption from the District's Rule 409.9 governing emissions from decontamination of soil to allow the stockpiled soil to remain covered onsite until the Spring when the soil would be spread next �,. to the excavation. The Air Pollution Control District indicated that the stockpiled soil was exempt from the provisions of Rule 409.9 and that no permit would be required for the proposed actions. Since petroleum hydrocarbons were not detected in the stockpiled soil, �.. it is proposed to proceed with spreading the soil in the pasture next to the tank site this Spring. BACKFILLING OF EXCAVATION Based on the absence of petroleum hydrocarbons in the samples from the excavation sidewalls, verbal permission to backfill was obtained from Ms. Turkatte while she was at the site during the excavation that was conducted on 4 November 1991. The Department's only additional requirement was the stipulation that a Backfill Excavation Certificate be supplied by Teichert. A copy of the requested certificate is attached to this letter along with a copy of the loading ticket for the crushed rock used for backfilling the excavation. CONCLUSIONS two The results of laboratory analysis of samples collected from the sidewalls after the furthest limits of excavation were completed (samples EX-1, 3, 4, 5, 7, 8, 9 and 10) indicate that, 4w except for one sample, hydrocarbon concentrations are below method detection levels. The one sample where petroleum hydrocarbons were detected (sample EX-3), the concentration was 1.3 mg/Kg. The residual levels of petroleum hydrocarbons as indicated by sample EX-3 present little potential for impacts to groundwater since groundwater is estimated at a depth of 100 feet below the ground surface in the vicinity of the tank excavation. This is based on groundwater measurements obtained from a well located on the property that is within 400 feet of the tank site. According to Mr. Russ Taylor of the East Bay Municipal Utility District (209-368-1475), the depth to groundwater was measured at 65 feet in April, 1991. Since the top of the well is approximately 35 feet below the tank site, groundwater is at �., an approximate depth of 85 feet below sample EX-3. Based on this evaluation, there does a.