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60 <br /> (- VAT <br /> �., <br /> A S S O C I A T E S I N C <br /> 2.0 WELL INSTALLATION ACTIVITIES <br /> Monitoring well installation activities were completed in accordance with ATC's Additional <br /> Subsurface Investigation Workplan, dated October 18, 2004. A drilling permit application was <br /> submitted to the San Joaquin County Environmental Health Department and Underground <br /> Service Alert was contacted to allow time for utility companies to identify underground lines, <br /> pipes, or cables that could be affected by the drilling activities. <br /> r <br /> 2_1 Hollow Stem Auger Drilling Activities <br /> On January 10 and 17, 2005, an ATC geologist supervised the installation of two monitoring <br /> wells (MW7 and MW8) to depths of approximately 20 feet bgs. A site plan showing the locations <br /> of the wells is included as Figure 2. Woodward Drilling, California License C57 710079, installed <br /> the wells utilizing a hollow stem auger drill rig. Soil samples were collected from the boreholes of <br /> the wells at five foot intervals in stainless steel sampling tubes for lithological logging purposes. <br /> The cored samples and drill cuttings were visually characterized for soil type, moisture content, <br /> and evidence of petroleum hydrocarbons. A photo ionization detector (PID) was used as a field- <br /> screening device for the detection of petroleum hydrocarbon vapors in drill cuttings and cored <br /> -- samples. The ATC field geologist logged drill cuttings and soil samples in general accordance <br /> with the Unified Soil Classification System. Descriptions of soil types encountered, sample <br /> collection intervals, and PID screening results are included on the boring and well construction <br /> logs contained in Appendix A. Drill cuttings were temporarily stored on site in 55-gallon DOT <br /> approved steel drums. <br /> 2_2 Site Geology and Hvdrogeolou <br /> The subsurface material encountered during the drilling activities generally consisted of asphalt <br /> L <br /> underlain by.inorganic clay to approximately 6.5 feet below ground surface (bgs). Sandy silt and <br /> inorganic silt were encountered from 6.5 to 11.5 feet bgs in borings MW7 and MW8, <br /> respectively. Poorly graded sands were encountered from approximately 11.5 to 21.5 feet bgs in <br /> both boring locations. Groundwater was generally encountered at approximately 10 feet bgs. <br /> 2.3 Well Construction Details <br /> Monitoring wells MW7 and MW8 were constructed with 10 feet (surface to 10 feet bgs) of blank <br /> 2-inch Schedule 40 PVC casing and 10 feet of slotted (0.010-inch slots) 2-inch Schedule 40 PVC <br /> well screen. The annulus of the screened portion of each monitoring well was backfilled with a <br /> #2/12 sand filter pack from approximately 8 to 20 feet bgs. Approximately two feet of bentonite <br /> L - pellets were placed on top of the upper filter pack and hydrated to form an annular seal. Cement <br /> grout was placed on top of the bentonite and the wells were each completed at grade with a <br /> SAEnviromenta1\17861-G1over\REP0RTS\2005QMR1 andwelIinstal lreport.doe 3 <br /> V <br />