SR0082695 - Laserfiche WebLink

Home Browse Search

Site Investigation Work Plan Deuel Vocational Institution(DVI), Tracy, California Introduction burn pit location is variably covered with asphalt,grass,and soil. The primary land use surrounding DVI is agricultural. A Union Pacific Railroad track runs along the northwest boundary of the DVI property. 1.4.2 Previous Investigations In October 1985,water samples were collected from the agricultural drainage ditch downstream from the DVI stormwater discharge. Elevated levels of chlorinated solvents were detected in the water samples, particularly PCE and TCE. Additional sampling and analysis of the project site was conducted in 1986,to identify the source of the impacts. The test results concluded that introduction of chlorinated solvents into the stormwater drainage system was occurring in the northern stormwater drainage subsystem. Further soil and groundwater sampling confirmed the burn pit as the source area of the chlorinated solvents. Groundwater monitoring wells were installed to assess the extent of the groundwater impacts. Monitoring wells(MW)MW-1-BP,MW-2-BP, and MW-3-BP were installed in 1987. MW-4-BP through MW-10- BP were installed in 1988.MW-11-BP through MW-15-BP were installed in 1994. MW-16-BP through MW-18-BP were installed in 1995. In 2003,the San Francisco Bay RWQCB issued Cease and Desist Order No. R5-2003-0066 to DVI for exceeding stormwater discharge effluent limits,most notably for chlorinated solvents. Part of the order required repair of broken storm drain pipelines, identified previously as receiving infiltration of affected groundwater. Emergency repair of the storm drainpipes was conducted in 2004. Sewer pipe rehabilitation was completed by January 2005. A groundwater remediation system was installed, in accordance with URS's Operation and Maintenance Manual Addendum, dated June 9,2005. The system uses a groundwater pump that was installed in MW-6,two liquid-phase granular-activated carbon vessels, a holding tank, and a sprinkler discharge system. The system was installed and began operation on August 4, 2005. The groundwater treatment system was shut off in October 2005 for the winter. 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-23-13P), 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. MW-I-STP through MW-4-STP from the sewage treatment plant and MW-19-SP through MW-24-SP from the sewage treatment ponds now are 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-25-13P),to serve as transition wells for an emulsified oil substrate (EOS)pilot test. On April 19,2011, groundwater monitoring well MW-23-SP was destroyed because of previous damage. URS drilled and installed replacement monitoring well MW-23R-SP approximately 10 feet from the original well location. In April 2011,URS completed an in situ bioremediation pilot test at the project site. Thirty EOS injection points were installed from south of MW-6-BP (in the former burn pit)to south of MW-5-13P. At the location of each injection, approximately 165 gallons of EOS solution was injected at approximately 7- 1-2