SITE INFORMATION AND CORRESPONDENCE 1995-2004

Home Browse Search

James L. Tjosvold, P.E. April 22, 1997 Page 2 contained hydrocarbons in the groundwater and one boring outside the substation yard upgradient of Area II; and 3) the installation of a B Zone well along El Dorado Street (MW- 26). Based upon field observations in Area II, it was determined that additional A and B Zone wells were not needed. Soil borings were analyzed for PNAs, TPH-diesel, TPH-gasoline and BTEX(Area II soils were also analyzed for chlorinated solvents). In addition, three soil samples from Area I(one from Source Area 2 and two outside source areas) were analyzed by DI WET for PNAs and TPH-diesel and by TCLP for TPH-gasoline and BTEX. Hydropunch samples were taken from the A Zone and the B Zone during the drilling of the new B Zone well (MW-26). These samples were analyzed for PNAs, TPH-diesel, TPH-gasoline and BTEX. The analytical results for this soil and groundwater investigation were sent to the agencies on February 9, 1997. Quarterly groundwater monitoring was conducted in December, 1996. The results of this groundwater monitoring was submitted to the agencies on January 31, 1997 in the "Quarterly Monitoring Report, PG&E Stockton Former MGP Site, Fourth Quarter, 1996". II. Activities Performed During Current Ouarter: The analytical results of the December, 1996 soil and groundwater investigation were submitted to DTSC and the RWQCB on February 9, 1997 in a technical memorandum. The results of the December, 1996 investigation can be summarized as follows: the results from Area I soil borings were used to further define the vertical and horizontal extent of Source Areas 1 and 4 and to refine the VLEACH model; the results from the Area H soil borings indicate that no constituents of concern(PNAs, TPH, BTEX or chlorinated solvents) are present in these soils, and therefore, these soils are not a potential source of the constituents of concern found in the groundwater; the results of the DI WET and TCLP demonstrated that the less mobile PNAs (including all the carcinogenic PNAs) do not leach out of the soil and that the more mobile PNAs barely leach out (e.g. less that 0.1% of the total PNAs present in the soil actually leach out under these tests); and finally, based upon the results of the newly installed groundwater monitoring well along El Dorado Street, the extent of PNAs in Zone B groundwater appears to be at or near El Dorado Street. These results of this December, 1996 investigation were discussed with DTSC and the RWQCB during a February 11, 1997 conference call. During the conference call, it was agreed that further soil and groundwater investigation of the site is not needed at this time and that PG&E can complete the FS process.