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Soil Investiga•and Background Groundwater Monitorinoell Installation Workplan <br /> January 17,2007 <br /> C A M B R I A <br /> land application as the preferred treatment option in order to ensure consistent permit compliance <br /> (EBMUD,2005b). <br /> 2005 Camanche Infiltration Rate Study: On November 16 and 17,2005,URS Corporation(URS) <br /> completed a site evaluation that included infiltration testing, using a double-ring infiltrometer in <br /> accordance with American Society for Testing and Materials (ASTM) Test Method D 3385-03; <br /> measuring the inundation thickness of the soil material underlying the area of the test;and collecting <br /> soil samples for moisture analysis. An analysis of the cation exchange capacity of representative <br /> samples was also performed,using U.S.Environmental Protection Agency(EPA)Method 6010. The <br /> objective was to assess the feasibility of disposing waste water from the Camanche Dam Powerhouse, <br /> ® to a proposed infiltration/evaporation pond to be located to the west of the powerhouse. Additional <br /> results are presented in URS's March 2006 Camanche Infiltration Rate Study-Summary Report <br /> (URS,2006). <br /> 2006 ApplicationlReport of Waste Discharge: On April 27, 2006, the District submitted the <br /> ApplicationlReport of Waste Discharge (RWD) for land application of the powerhouse's effluent <br /> based on EBMUD's December 22,2005 Implementation Plan and Time Schedule for Complying with <br /> the Final Copper Effluent Limitations(EBMUD, 2006). <br /> Geology and Hydrogeology <br /> The site is located at the base of the west-facing flanks of the Sierra Nevada Foothills. The area is <br /> characterized by northwest-southeast trending low-lying hills and valleys,which are highly dissected <br /> by local tributaries. Geologic units underlying the site consist of natural levee and channel deposits <br /> associated with the Mokelumne River.The deposits are an amalgamation of sediment that was eroded <br /> and carried downstream from the Siena Nevada.Geologic units within the vicinity of the site include <br /> the Turlock Lake, Mehrten, and Valley Springs Formations. According to URS's November 2005 <br /> investigation,shallow excavations within the proposed pond area showed subsurface conditions to be <br /> relatively consistent with increasing depth.Surface soils consisted of approximately 6 to 10 inches of <br /> fill with varying amounts of clay,silt, and sand with some cobbles and metal debris.Underlying the <br /> fill,materials encountered to 61/2 feet(the maximum depth explored)consisted primarily of clayey silt <br /> with very fine to fine sand and a few sub-rounded pebbles. A detailed description of the site and <br /> regional geology can be found in URS' March 2006 Camanche Infiltration Rate Study Summary <br /> Report. <br /> The site is located withinthe Eastern San Joaquin Subbasin defined by the aerial extent of <br /> unconsolidated to semi-consolidated sedimentary deposits that are bounded by the Mokelumne River <br /> 3 <br />