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Clayton <br /> Im RU"gF%til <br /> _.. [li.til[11IF5 <br /> 6.3 QUARTERLY GROUNDWATER SAMPLING - APRIL 1991 <br /> On April 25, 1991, Ms Hutson requested one additional quarterly water sampling of <br /> monitoring well MW-3B before she would recommend site closure to the Regior-A <br /> Water Quality Control Board. <br /> On May 2, 1991, Clayton conducted the additional quarterly water sampling of <br /> monitoring well MW-3B This task was conducted to assess groundwater for possible <br /> contamination from the hydrocarbons detected in the surrounding soils <br /> r <br /> The groundwater sample was analyzed by the following methods <br /> • E-PA Method 5030/8015-8020, for gasoline and BTEX <br /> • 17-.PA Method 3510/8015, for TPH as diesel fuel <br /> EPA Method 4181, for TRPH <br /><` Standard Method 5520F, for TPH <br /> Analytical results revealed gasoline, BTEX, diesel, TPH, and TRPH were below <br /> a <br /> "-" detection levels. <br /> 6.4 ADDITIONAL SOIL INVESTIGA71ON CONCLUSIONS <br /> The oil and grease, diesel, and hydrocarbons that were detected in MW-3B at 4 feet <br /> bgs were not detected in the soil samples taken from any of the five boreholes. These <br /> constituents do not leach easily from sods, and analysis of groundwater samples from <br /> MW-3B did not reveal detectable concentrations. Based on the hatted extent of the <br /> constituents demonstrated by analysis of soil samples from the surrounding boreholes, <br /> Clayton recommended no further soil remediation at the subject site. Moreover, in a <br /> letter to the RWQCB dated July 16, 1991, the SJC/EHD recommended site closure, <br /> corroborating with Clayton. <br /> Orchard Supply Hardware requested that SJC/EHD recommend site closure to the <br /> RWQCB. The letter from SJC/EHD to the RWQCB recommending site closure is <br /> presented in Appendix B. <br /> F <br /> 7.0 REFERENCES <br /> x3, Leaking Underground Fuel Tank (LUFT) Field Manual- Guidelines for Site <br /> �- Assessment, Cleanup, and Underground Tank Closure, May 1988. State of California <br /> t LUFT Task Force. <br /> Marshack, J.B., 1990. A Compilation of Water Quality Goals, Staff Report of the <br /> California RWQCB Central Valley Region <br /> 5 <br /> Regional Board Staff Recommendations for Initial Evaluation and Investigation of <br /> Underground Tanks, Revised November 1989. North Coast, San Francisco Bay, and <br /> Central Valley regions of the California State Water Quality Control Board <br /> 11 <br /> r 315060L"p <br /> St <br />