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MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916)255-3000 Sacramento, CA 95827-3098 CALNET:8-494-3000 To: Wendy L. Cohen `' From: John D. Moody Senior Engineer W er R ource Co trol ngineer DATE: 26 July 1995 SIGNATURE: Subject: WORK PLAN FOR PHASE II REMEDIAL INVESTIGA N, R URAL CALIFORNIA HOUSING COMMISSION, MOUNTAIN VIEW TOWNHOMES SITE, TRACY, SAN JOAQUIN COUNTY I have reviewed the 29 June 1995 work plan entitled Work Plan for Site Assessment, Old Valley Line, Mile Post 215, prepared by Emcon for the next phase of remedial investigation at the Mountain View Townhomes site. For background purposes, I have also reviewed the 5 June 1995 report of the initial investigation entitled Observations and Soil Sampling During Removal of Crude Oil Pipelines, Mountain Vie iv Totivnhomes Site, prepared by Raney Geotechnical. My comments on the work plan, along with a site summary, are presented below. SITE SUMMARY The site is a three-acre vacant lot at 413 Mount Diablo Boulevard in Tracy, as shown in Attachment 1. Petroleum contaminated soil was discovered at the site when Chevron Pipeline Company (CPL) removed two abandoned crude oil pipelines from the site in May 1995. CPL removed the pipelines at the request of the Rural California Housing Commission (RCHC), which plans to develop the site as a low income housing project. The pipelines, which CPL refers to as the Old Valley Line, were used from the early 1900s through the 1950s to transport crude oil from the Elk Hills oil fields near Bakersfield to the San Francisco Bay area (the same pipeline crosses the Dividend property also near Tracy). Raney Geotechnical, consultant for the RCHC, observed the excavation operations and noted several possible leaks along the section of pipeline removed. Raney also identified seven areas along the former pipeline easement where the soil showed indications of petroleum hydrocarbons. CPL then removed the most visibly affected soil with a backhoe, and Raney obtained soil samples from the excavations. The samples were analyzed for total petroleum hydrocarbons (TPH) by EPA Method 8015. RESULTS OF INITIAL INVESTIGATION The results of the initial soil sampling by Raney showed high concentrations of TPH remaining in Areas 2 and 4 shown in Attachment 2. After further excavation and re-sampling, results from Area 4 showed TPH up to 6,150 mg/kg at the water table at 24 feet below ground surface (bgs), while Area 2 showed close to nondetectable levels (1 mg/kg) at 12 feet bgs. The ground water was not sampled. Raney also took soil samples from stockpiles at Area 7 and analyzed the samples for TPH by EPA