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US <br /> ' Ms. Kathleen Amaru Page 3 <br /> Regional Water Quality Control Board—Central Valley Region <br /> ' July 31, 2009 <br /> oxidant demand(SOD)which is considered to be a much more realistic and complete gauge of the <br /> oxidant demand than COD or BOD. <br /> ' On March 27, 2008, groundwater monitoring well MW-11 was destroyed to make way for the new <br /> sewer treatment plant. <br /> On May 5,2008,RWQCB requested a passive soil gas survey be conducted in the former Bum Pit area <br /> to determine if sewer lines are acting as a conduit for the migration of impacted groundwater. <br /> SITE ASSESSMENT ACTIVITIES <br /> ' To assess if stormwater/sewer lines are acting as a conduit for the migration of impacted groundwater, <br /> URS installed 50 passive soil gas modules in the area of the former Bum Pit. <br /> Utility Clearance <br /> Underground Service Alert(USA)was contacted a minimum of 48 hours prior to beginning work at the <br /> site. On April 30,2009,URS met with DVI personnel with knowledge of the stormwater/sewer lines <br /> and other underground utilities to aid in the selection of the 50 passive soil gas locations. <br /> Permitting <br /> The San Joaquin County Environmental Health Department did not require a permit for soil borings less <br /> 1 than 3 feet below ground surface (bgs). <br /> Project Health and Safety <br /> A site-specific health and safety plan(HASP)was prepared and made available on site during field <br /> activities. The plan was reviewed by URS field personnel before the start of field activities. <br /> ' Passive Soil Gas Location Selection <br /> ' A total of 50 locations were selected(Figure 1)to assess if stormwater/sewer lines may be acting as a <br /> conduit for impacted groundwater. The locations were chosen in the former Burn Pit area and continued <br /> north along the stormwater/sewer lines to the old sewage treatment plant using a grid pattern to cover <br /> ' the most area as possible. The locations were placed to straddle the sewer lines to assess VOC <br /> concentrations in the soil gas. If the sewer line is acting as a preferential conduit,then higher VOC <br /> concentrations would be expected along the sewer lines. <br /> Installation <br /> On April 30 and May 4, 2009, 50 passive soil gas modules were installed from the former Burn Pit area <br /> ' north to the old sewage treatment plant.A 1.5-inch-diameter screw hand auger or an electric rotary <br /> ' rAWp...1tESDIDVI-Born Pk1N9 Passive SG\P.&i SoilG S.,Re,n.dec <br />