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2 �� Cardno® Well Destruction Report ATC Former Cheaper Store No.37 Shaping the Future December 12,2013 contain detectable concentrations of petroleum hydrocarbons. A sensitive receptor survey was conducted within a 2,000-foot radius of the site. Groundwater monitoring well (MW-4)was installed north of the former USTs on April 19, 1988. In late April 1988, the open excavation associated with the former USTs was expanded by excavating petroleum- impacted soils above the groundwater. An additional 350 to 400 cubic yards of soil were removed from the former UST excavation between April 25 and 28, 1988. The results of the laboratory analyses of the soil samples collected from the sidewalls of the enlarged excavation indicated that low concentrations of petroleum hydrocarbons remained in the soils at the south and southeastern portion of the excavation. Free floating product was measured in well MW-4 by Parker Environmental Services (PES) during September 1992. A passive, selective membrane skimmer to recover the floating product was installed in MW-4 on February 11, 1993. Soil borings BH-1 through BH-7 were advanced at the site to depths of approximately six to seven feet bgs on February 26, 1993. Soil borings B-8 through B-21 were advanced and four additional groundwater monitoring wells (MW-5 through MW-8)were installed at the site to evaluate the lateral extent of impacted groundwater between July and October 1995. In a letter dated April 11, 2002, the EHD indicated that up-gradient groundwater monitoring wells MW-2 and MW-3 could be reduced to annual groundwater monitoring and that the lateral and vertical extent of soil contamination remained undefined. On September 11 and 12, 2003, a 500-gallon UST that had contained used oil was excavated and removed from the site by Walton Engineering, Inc. Petroleum hydrocarbons and metals were detected in a soil sample collected at the base of the UST from a depth of approximately seven feet bgs. Refer to Grayland Environmental's Underground Storage Tank and Fuel Dispenser Removal Report, dated October 16, 2003, for more information. On October 14, 2004, two cone penetration testing (CPT) borings were advanced at the site to depths of approximately 80 feet bgs to evaluate the vertical extent of groundwater beneath the site. Petroleum hydrocarbons and MTBE was detected in the soil and groundwater samples collected from the CPT boring locations. In August 2008, a sensitive receptor report was completed by ATC. In this report, ATC concluded that sensitive receptors located east and south of the site were not generally at risk and that the water supply wells observed in the vicinity of the site were judged not likely to be impaired based on proximity to the site. This report also concluded that the contaminant plume had not yet been fully defined to the north in the shallow water-bearing zone. In a letter dated June 22, 2009, the EHD directed that reduced groundwater monitoring be implemented at the site in response to the adoption of Resolution No. 2009-0042 by the State Water Resources Control Board (SWRCB). They directed the collection and sampling of groundwater samples from wells MW-1, MW-4, MW-5, and MW-8 be conducted semi-annually and from all other wells at the site biennially.Additionally, the EHD granted ATC's request to discontinue analyzing groundwater samples collected from the site for di-isopropyl ether(DIPE), ethyl tertiary- butyl ether(ETBE), 1,2-dichloroethane(1,2-DCA), and 1,2-dibromoethane(EDB). On January 22, 2010, a soil boring (SB-6)was advanced to the first encountered groundwater to evaluate the lateral extent of the impacted groundwater northwest of the source area. Two discrete grab groundwater samples (HP-1 and HP-2)were collected using a hydropunch sampling tool in the vicinity of CPT-2. HP-1 was advanced to an approximate depth of 45 feet bgs and HP-2 was advanced to an approximate depth of 70 feet bgs. MTBE was the only analyte of interest detected in the groundwater sample collected from SB-6. None of the analytes of interest were detected in the groundwater samples collected from HP-1 and HP-2. www.cardnoatc.com