WORK PLANS - Laserfiche WebLink

Home Browse Search

Coyner Property Page 4 Tank Closure Report Project 103.5 August 21,1996 There is a domestic water well on the Property that is in active use_ It lies in excess of 250 feet northwest (probably up-gradient) of all three former tanks. 3.4 Hydrocarbon Distribution in the Soil Based on the laboratory results, a small amount of gasoline was released from tank 2, and a small amount of diesel was released from tankl. The complete vertical and horizontal extent of the impacted soil is not known, but based on the levels reported from the confirmation samples, it seems unlikely that it extend very much below the tank pit bottoms or that groundwater was impacted. 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 Conclusions I. Of the three UST's which were formerly located on the Property, one was found to have impacted the soil sufficiently to cause the County PHS/EHD to deny final closure. The denial was based on a leaching potential estimate for xylene as described in the State LUFT Manual, 2. The Iaboratory analysis of the soil sample from beneath the tank of concern, indicates that non detectable levels of Total Petroleum Hydrocarbons (TPH-G) and three of the four BTEX compounds were present. The only hydrocarbon detected was xylene of which 11 parts per billion (ppb) were found. This low level of contamination suggests residual impacted soil does not pose a significant threat to the groundwater. Moreover, the nearest domestic water well is in excess of 250 feet from the former tank site. 3. The nearest domestic water well is more than 250 feet away and in an up gradient position. In the event that groundwater were to be impacted by hydrocarbons, it seems very unlikely that drinking water would be materially degraded. 4. Based on the groundwater monitoring results from the nearby Gilley's site, it appears that the depth to groundwater under the former leaking tank is greater than 50 feet (actually 63 ft BGS) rather than the less than less than 50 feet which was assumed in the leaching potential assessment. If the correct groundwater level were input to the leaching potential table, it appears the level of BTEX which was left in the soil would meet the LUFT Manual guidelines for site closure. 5. Recent research by Lawrence Livermore National Laboratory, and guidelines adopted by the State and LOP regulators indicate that shallow soil contamination by motor fuels Phase One Environmental Inc. 2937 Veneman Ave.,#B240 Modesto,CA 95356 (209)569-0293