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San Joaquin County Environmental Health Division Project 2267-E <br /> December 29, 1999 Page 2 <br /> BACKGROUND DATA <br /> It is our understanding that a Standard Oil Service Station operated from the late 1960's <br /> until December 1980 on the approximately 0 7 acre site (APN 139-250-05) east of the 11 <br /> story office building at 242 N Sutter Avenue, see Plate 1 for the approximate locations of <br /> the pump islands (Sanborn Map, 1972) Upon closure of this service station in 1980, the <br /> underground storage tanks were removed from the site (County Building Inspector's <br /> Card) We do not know exactly where the removed underground storage tanks were <br /> located, however, it is our opinion that they were in the northeast corner of the property, <br /> in close proximity to the pump islands <br /> A small service station consisting of four 550 gallon underground storage tanks was also <br /> apparently located on this site, according to the 1950 Sanborn Map, see Plate 1 Based on <br /> aenal photographs and other information, it appears that this facility operated from the <br /> 1940's until February 1960, when the underground storage tanks were abandoned and <br /> filled with sand We are not aware of any reported petroleum contamination of tli� soil or <br /> groundwater at this site, which is currently asphalt-paved and being used as a parking lot <br /> for the office building at 242 N Sutter Avenue <br /> A Unocal Service Station (Site No 1181, File No P98-188) located on the northwest <br /> corner of East Miner Avenue and California Street, continuously occupied this parcel at <br /> 437 East Miner Avenue, approximately 100 feet north of the subject property, from 1922 <br /> until its closure in 1992 This service station was remodeled in 1967, and two leaking, 45 <br /> year old, 1,000 gallon gasoline tanks and a 550 gallon waste oil tank were remoNed from <br /> the southwest corner of the site These tanks were replaced by two new 10,000 gallon <br /> tanks and a 280 gallon waste oil tank that were relocated in the western portion of the <br /> site, see Plate 1 and Appendix A Soil samples from under the removed tanks were not <br /> tested for petroleum hydrocarbon contamination at the time of their removal Subsequent <br /> field studies and monitoring wells, installed in 1994, showed that there is significant <br /> contamination beneath the underground storage tanks that were removed in 196;, with <br /> . total petroleum hydrocarbon concentrations up to 19,000 ppm TPH-gas and 140 ppm of <br /> c �asra as <br /> tsska <br /> arx 31 n°a <br /> HYDRO-GEO CONSULTANTS,INC <br />