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MEMORANDUM _ CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY P&OMN 3443 Rouser Road, Suite A Phone: (916)ZSS-3000 Sacramento, CA 95827.3098 CALNET: 8-494-3000 TO: Wendy L. Cohen 1 FROM: Joel M. Weiss Senior Engineer Engineering Geologist DATE: 16 February 1994 SIGNATURE: SuBjEcr. CONTAMINATION AT CINTRA GROUP PROPERTY, TRACY, SAN JOAQUIN COUNTY Background In February 1993, San Joaquin County officials notified the Board that contamination was present at the above-referenced site. The site is approximately 100 feet north of an abandoned oil pipeline which runs beneath the Southern Pacific Railroad right-of-way. A line of 19 borings were drilled parallel and north of the suspect pipeline as part of a January 1993 site assessment. All borings were drilled to a depth of five feet below ground surface (bgs) except for SB-11 which was drilled to 15 feet bgs to collect a water sample. Four select soil samples from three different borings were analyzed for total petroleum hydrocarbons ('IPED as oil and grease, and benzene, toluene, ethylbenzene and xylene (BTBX). The soil sample from SB-11 was taken at 10.5 feet bgs while the other_three samples were taken from 5.5 feet bgs. These analyses all came back as non-detectable. . The ground water sample, however, revealed 13 ppb toluene, 3.4 ppb ethylbenzene, and 22 ppb xylene. The ground water table is approximately 11 feet bgs. Cintra has requested closure of the case based upon the fact that shallow ground water in the Tracy area is not suitable for domestic or agricultural purposes, and also the fact that the concentrations encountered in the ground water here are nearly all below State secondary MCls. Comments Since ground water has been degraded, the site should.not be closed. Soil samples may be non- detectable simply because they were taken at shallow depths. It is unknown how deep the pipeline is buried. Sharon Young of RESNA said in a 1 February 1994 telephone conversation that the other soil borings (there were 19 total) were not analyzed because there was no physical sign of contamination. The ground water gradient needs to be determined (Le. install three wells). The Belconte-North site on the south side of Byron road has shown soil contamination. Four monitoring wells on that site have shown a southwest gradient. If the gradient is correct, then contamination from the pipeline onto the Cintra Group Property would probably only be through upgradient dispersion phenomena. The McCormack property, also south of Byron Road, also has an ongoing contamination cleanup project underway. Cintra should coordinate with Belconte-North and McCormack, and 'change their analysis of TPH from the 5520 E/F method to the modified 8015 method. JMW:jmw/ldj