SITE INFORMATION AND CORRESPONDENCE_FILE 1

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i � r MEMORANDUI, T CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Antonia Vorster FROM: Michael Higgins Senior Engineer Associate Engineer DATE: 8 October 1991 SIGNATURE: SUBJECT: DIVIDEND DEVELOPMENT SITE, TRACY, SAN JOAQUIN COUNTY I have reviewed Toxic Technology, Inc. 's (TTI) 15 August 1991 Remediation Workplan (workplan) and the 22 July 1991 Report of Findings (report) of the site investigation for the Dividend Development Company property in Tracy. The report describes the polluted soil and ground water, in addition to free product floating on the ground water in one monitoring well (MW), discovered at the site. The workplan proposes to excavate and remove the polluted soil to a nearby area where TTI will reduce the pollutant concentrations via biotreatment. Based on these data, TTI has concluded the source of the pollution is the adjacent pipeline right-of-way now owned by Santa Fe Pacific Pipeline Partners, Ltd. (SFPPP) . (To my knowledge, SFPPP is not addressing the polluted soil and ground water in this section of the pipeline right-of-way at this time.) During the site investigation, TTI sampled the soil profile at increasing depths in seven boreholes which they subsequently converted to ground water monitoring wells (NW) . Soil samples from the unsaturated zone of five of the seven boreholes contained substantial concentrations of fuel components. Sampling and analysis also detected free product and dissolved fuel components in the monitoring well (MW-2) closest to the suspected pollutant source. The sampling and analysis indicated that the pollution is probably largely confined to the unsaturated zone and the free product is localized to an area immediately adjacent to the MW-2. The polluted soil appears to be confined to an area within a 200-foot radius north from the junction of the northern boundaries of the pipeline and freeway rights-of-way. The workplan is deficient as follows: 1. The workplan must address the removal of free product from the capillary fringe and the ground water. 2. The workplan should describe how TTI will determine they have excavated all the polluted soil . A method whereby one might assess the excavation's necessary extent would require that the soil is excavated to the pollution's visible extent. This limit could be estimated where discolored and/or stained soils, or oil sheens on the ground water in the bottom of the excavation, were no longer visible. Subsequently, a statistically valid number of soil samples and/or ground water samples from the excavation's sides and bottom would be obtained and analyzed for the pollutants. When the pollutant concentrations at the limits of the excavation are below analytical detection limits, all the polluted soil has been removed.