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URS <br /> ' Ms.Kathy Amain Page 2 of 9 <br /> Regional Water Quality Control Board—Central Valley Region <br /> ' April 30,2014 <br /> Groundwater monitoring wells were installed to assess the extent of groundwater impacts. Monitoring <br /> wells MW-1-BP, MW-2-BP, and MW-3-BP were installed in 1987. Monitoring wells MW-4-BP <br /> through MW-10-BP were installed in 1988. Monitoring wells MW-11-BP through MW-15-BP were <br /> installed in 1994. Monitoring wells MW-16-BP through MW-18-BP were installed in 1995. Monitoring <br /> wells MW-1-BP, MW-5-BP, MW-6-BP, and MW-9-BP are currently used to monitor petroleum and <br /> chlorinated solvent-impacted groundwater at the site on a quarterly basis. <br /> ' In 2003, the Regional Water Quality Control Board issued Cease and Desist Order No.R5-2003-0066 <br /> to DVI for exceeding stormwater discharge effluence limits, most notably for chlorinated solvents. Part <br /> ' of the order required the repair of broken storm drain pipelines identified previously as receiving <br /> infiltration of impacted groundwater. Emergency repair of the storm drain pipes was conducted in 2004. <br /> Sewer pipe rehabilitation was completed by January 2005. <br /> A groundwater remediation system was installed in accordance with URS' Operation and Maintenance <br /> Manual Addendum, dated June 9, 2005. The system utilizes a groundwater pump installed in well <br /> MW-6, two liquid-phase granular-activated carbon vessels, a holding tank, and a sprinkler discharge <br /> ' system.The system was installed and started on August 4,2005.The groundwater treatment system was <br /> shut off for the winter in October 2005. The system was restarted in early April 2007, and operated for 4 <br /> months. <br /> ' On November 16 and 17, 2004,URS drilled and installed five 2-inch-diameter groundwater monitoring <br /> wells (MW-19-BP through MW-23-BP) adjacent to the sewage treatment plant ponds. These wells are <br /> ' used to monitor potential groundwater quality impacts related to the sewage treatment plant ponds. <br /> On March 27, 2008, groundwater monitoring well MW-11 was destroyed to make way for the new <br /> sewer treatment plant. <br /> Monitoring wells MW-I-STP through MW4-STP, from the sewage treatment plant, and MW-19-SP <br /> through MW-24-SP, from the sewer ponds,are now being used as part of the burn pit investigation. <br /> On March 30, 2011, URS drilled and installed two groundwater monitoring wells (MW-24-BP and <br /> MW-25-BP),to serve as transition wells for the emulsified oil substrate(EOS)pilot test. <br /> On April 19, 2011, groundwater monitoring well MW-23-SP was destroyed due to previous damage. <br /> URS drilled and installed MW-23R-SP at approximately 10 feet from the original well location. <br /> In April 2011, URS completed pilot test activities. Thirty injection point locations were installed from <br /> south of monitoring well MW-6-BP, located in the former burn pit, to south of MW-5-BP. At each <br /> ' injection location, approximately 165 gallons of EOS-diluted solution(at a 10 to 1 ratio of potable water <br /> to EOS) was injected into the subsurface from approximately 7 to 23 feet below ground surface (bgs). <br /> The injection borings were destroyed using bentonite slurry. <br /> 1 <br /> ' HAWprocu TDCR\Dmcl Voceliom i kution(B=Pk)IDVI-BP-IQM 14 Rc n.d <br />