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� 1 Isch Memajen (smrasser.a„m, fW&uft•.rommthK AXH2016 • Labomlory analyses conducted m determine concentmtions of SVO(: pPAHs, and PCBs in subsurface soil and PCBs in ground water (Section 3.4), and • Quality assurmree/quality control (Section 3.5). 3.1. Borehole Drilling As discussed in the Work Plan, the 150 R x 200 ft study area boundaries shown in Figure 8 rc determined based on the known and potential locations or the Eastern GSA debris burial trenches identified through: • Analysis ofhislorical aerial photographs. • Information presented in previous reports documenting investigations conducted in the debris burial trench area (ix , SWRL [1mcb, Wade or al, 1991). • Data form previously drilled and sampled brochures and ground water monitor wells. • Data and information from the 1990 test pit excavation and sampling effort (Wade cc a1., coati). Based on this information, there was a high level or confidence that the perimeter of the Eastern GSA debris burial trench study area shown in Figure 8 were accurately located. q e Work Plan specified that a total ofewelve borehoks would be drilled and sampled within the study area including: Six burehogs in the known debris burial trench locations. Five brochures in the locations or the 19N tact pits where metal coupon VOC soil contamination was encountered. One additional borehole heated betwcen two debris burial trenches and two own pits. "Pro regulatory agencies concerned that this approach would result in the highest probability of detecting SVOC, PAH, and PCB contamination, if present, in subsurface suil in the debris burial trench area. The drilling ofilue burcholes in the Eastern GSA debris burial trench study area was initiated on September 22, 2014 and was completed on September 29, 2014. In addition to the toque ceramics specified in the Work Plan, one additional borehole (B-EGSA-3M9A) was drilled in the Test Pit 5 location as the drive sampler was obstructed by a rubber like material encountered at 6.5 R bgs in borehole B-EGSA-3029, that prevented deeper sampling (Figure 9). Therefore, the rig moved 5 ft laterally and borehole II-EGSA-3029A was drilled and sampled to 15 ft bp. All other botcholes were located as proposed in the Work Plan. Figure 8 presents the location of the 13 boieholes from which subsurface soil samples were collected and analyAd. All Nurtures were located within the boundaries of the debris burial reach study arms. The borehole locations were located using a Irimble Pathfinder 14o XR Global Positioning System (OPS) deviaa The borelwles were drilled in accordance with LLNL drilling-related SOPS with a Rhino MST Imek-mounted hollow item auger rig to a diameter of 6 inches (in) and a maximum depth