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' ► F A'J f; T CONDOR EARTH TECHNOLOGIES INC. A'IC 3) PH 2: 04 L. 188 Frank West Circle ' Suite I L. August 28, 2002 Stockton, CA 95206 (209) 234-0518 FAX (209) 234-0538 4+ David and Marianne Warwick 5730 Bennett Valley Road Santa Rosa, CA 45404 Re: Underground Storage Tank Closure at 640 N. San Joaquin Street, Stockton, California L' Condor Project No. 3572D Dear Mr. and Mrs. Warwick: Lr This letter report describes closure of an underground storage tank (UST) including the investigation leading to identification of the UST and results of soil sampling associated with the closure. This work Lw was conducted by Condor Earth Technologies, Inc. (Condor) at the property located at 640 N. San Joaquin Street, Stockton, San Joaquin County, California. The site location is shown in Figures I and 2, attached. The work was performed for Mr. and Mrs. Warwick. L. Background On May 23, 2002, buried fuel pipes at the site were traced by a line locating service from the east side of L• the Heritage Square building, through the building basement, to the north side of the building along E. Park Street. The fuel pipes appeared to terminate in the sidewalk along the south side of the street. A backhoe was used to confirm the location of the fuel pipes north of the building. Within the first two feet, L. potential fill and monitor pipes were encountered (see Figure 3). The monitor pipe contained a bamboo rod that was removed and found to be coated by approximately six to 12 inches of a black viscous petroleum product at its base. On May 24, 2002, a UST at an approximate depth of eight feet below 160 ground surface (bgs) was partially excavated at this location north of the Heritage Square building. On June 27, 2002, the UST was further excavated. No staining, odors, or other signs of contamination were noted in the excavated soil above the UST. The tank diameter was measured to be five feet and the length to be 10 feet. The approximate volume of the UST is 1,500 gallons. The suction and return pipes were disconnected from the UST and the portions continuing beneath the basement of the Heritage Square building to the south were capped and left in place. The fill pipe was excavated approximately L. nine feet north of the UST into the sidewalk along the south side of E. Park Street where a former remote fill connection was identified. The horizontal portion of the fill was removed for disposal. The vertical portions of the fill pipe and the monitor pipe were capped and left attached to the UST to allow the UST closure to take place without re-excavation. The UST was pressure-washed and triple-rinsed and the rinsate removed and transported off site for disposal by American Valley Waste Oil, Inc. The excavation was backfilled with the clean excavated material and the fill and monitor pipe locations marked for later L. identification. ENVIRONMENTAL GEOLOGICAL ENGINEERING GEOTECHNICAL http://www.condorearth.com L.