SITE INFORMATION AND CORRESPONDENCE

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- h MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3440 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Wendy L. Cohen FROM: Joel M. Weiss Senior Engineer Engineering Geologist DATE: 16 February 1994 SIGNATURE: SUaJECT: SOIL CONTAMINATION AT THE MCCORMACK PROPERTY, TRACY, SAN JOAQU N COUNTY The site is approximately 100 feet south of an abandoned oil pipeline which runs beneath the Southern Pacific Railroad right-of-way. As part of a 1993 site assessment, seven borings were drilled near the northern boundary of the site with Byron Road. One sample was taken from each boring at approximately six feet below ground surface (bgs). Boring'SB-1 was drilled to a depth of 10 feet bgs to collect a ground water sample. Two borings had obvious soil contamination and were not sampled. Two other soil borings showed total petroleum hydrocarbons as oil and grease (TPHOG) concentrations of 730 and 140 mg/kg as well as detectable concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX). Three soil samples showed non-detectable levels for both TPHOG and BTEX. The ground water sample was clean,.and the ground water table is approximately seven feet bgs: The Belconte-North property is just east of the site. Soil contamination also has been discovered there, and the gauging of four ground water monitoring wells on that property has revealed a southwest gradient. On the McCormack property, the lateral extent of soil contamination is defined except to the northeast area towards Byron Road and the pipeline. The vertical extent of contamination has not been addressed. A ground water sample should be taken southwest of the soil plume. A work plan should be submitted for soil remediation. Future analyses should include TPH by the modified 8015 method. JMW:j mw/Idj