ARCHIVED REPORTS_THIRD QUARTER 2014 GROUNDWATER MONITORING REPORT

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URS Mr. Durin Linderholm Page 2 of 10 Regional Water Quality Control Board—Central Valley Region ' October 30, 2014 ' Groundwater monitoring wells were installed to assess the extent of groundwater impacts. Monitoring wells MW-1-BP, MW-2-BP, and MW-3-BP were installed in 1987. Monitoring wells MW-4-BP through MW-10-BP were installed in 1988. Monitoring wells MW-11-BP through MW-15-BP were installed in 1994. Monitoring wells MW-16-BP through MW-18-BP were installed in 1995. Monitoring wells MW-1-BP, MW-5-BP, MW-6-BP, and MW-9-BP are used to monitor petroleum and chlorinated solvent-impacted groundwater at the site on a quarterly basis. ' In 2003, the Regional Water Quality Control Board issued Cease and Desist Order No. R5-2003-0066 to DVI for exceeding stormwater discharge effluence limits, most notably for chlorinated solvents. Part ' of the order required the repair of broken storm drain pipelines identified previously as receiving infiltration of impacted groundwater. Emergency repair of the storm drain pipes was conducted in 2004. Sewer pipe rehabilitation was completed by January 2005. ' A groundwater remediation system was installed in accordance with URS' Operation and Maintenance Manual Addendum, dated June 9, 2005. The system utilizes a groundwater pump installed in well MW-6, two liquid-phase granular-activated carbon vessels, a holding tank, and a sprinkler discharge ' system. The system was installed and started on August 4, 2005. The groundwater treatment system was shut off for the winter in October 2005. The system was restarted in early April 2007, and operated for 4 months. ' On November 16 and 17, 2004, URS drilled and installed five 2-inch-diameter groundwater monitoring wells (MW-19-BP through MW-23-BP) adjacent to the sewage treatment plant ponds. These wells are ' used to monitor potential groundwater quality impacts related to the sewage treatment plant ponds. On March 27, 2008, groundwater monitoring well MW-11 was decommissioned (destroyed) to make way for the new sewage treatment plant. Monitoring wells MW-I-STP through MW-4-STP, from the sewage treatment plant, and MW-19-SP through MW-24-SP, from the sewage ponds, are now used as part of the burn pit investigation. ' On March 30, 2011, URS drilled and installed two groundwater monitoring wells (MW-24-BP and MW-25-BP), to serve as transition wells for the emulsified oil substrate(EOS)pilot test. ' On April 19, 2011, groundwater monitoring well MW-23-SP was destroyed due to previous damage. URS drilled and installed MW-23R-SP at approximately 10 feet from the original well location. ' In April 2011, URS completed pilot test activities. Thirty injection point locations were installed from south of monitoring well MW-6-BP, located in the former burn pit, to south of MW-5-BP. At each injection location, approximately 165 gallons of EOS-diluted solution (at a 10-to-1 ratio of potable water to EOS) was injected into the subsurface from approximately 7 to 23 feet below ground surface (bgs) (Figure 5). After completing the EOS injections, the injection borings were destroyed using bentonite slurry. 1 OSACDATA01\DisCzPIIuc6\Wpmcass\CDCR\Dmel VOCadums IIsum0un(Bum PWDVI-BP-3QA 14 Rc m.doc