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k'■ KLEI_FE LDER Monitoring Well Installation and Surveying Three (3) monitoring wells will be installed at the locations shown on Plate 2. The proposed well locations have been selected to address groundwater conditions in the estimated upgradient and downgradient locations to the pipeline spill. One well is proposed upgradient and two down-gradient of the spill area. Based upon available information, we anticipate groundwater in the vicinity of the project site to be present at a depth of approximately 40-45 feet bgs with a groundwater flow direction to the north- northeast. The soil borings will be drilled with a truck mounted drill rig equipped with 8-inch hollow stem augers. During advancement of the soil borings, soil samples will be collected at five-foot intervals for lithologic classification and possible laboratory analysis. Lithologic classification will be based on the Unified Soil Classification System (USCS). All ' equipment used in the drilling and installation procedures will be cleaned and/or decontaminated as described in Attachment B. Soil cuttings generated from the drilling ' operation will be contained in 55-gallon drums or removed offsite as part of the excavation and removal action. If the soil is left in drums, the soil will be evaluated prior to potential disposal by the client. Kleinfelder proposes to analyze two (2) soil samples from each boring. The first soil sample will be collected at 10 feet bgs. The second soil sample will be collected just above estimated first encountered groundwater. After collection, the soil samples will be labeled, logged on a chain-of-custody, and immediately stored in an iced cooler. The samples will be analyzed as described in Section 6.5. tFollowing completion of the drilling, a 2-inch diameter PVC well will be installed in the borings. The soil borings will be advanced approximately 10 feet into groundwater. ' The wells will be constructed with Schedule 40 PVC, a 15 foot long 0.010 inch screened section surrounded by and covered by a sand filter pack (#2/12), 3 foot thick bentonite transition seal above the filter pack, and grouted to the surface with a neat cement mixed with no more than 3% to 5% bentonite powder to retard the heat of hydration and limit the possibility of damaging the PVC casing. The wells will be finished with a locking pressure cap situated within a monument or flush style well vault (depending on ' surface conditions). See proposed Monitoring Well Installation Diagram (Plate 5). Once the monitoring wells have been installed, the top of each well will be surveyed (by a licensed surveyor) so that depth to groundwater measurements in the wells can be converted to groundwater elevations used to assess groundwater gradients. The wells will be surveyed relative to a local benchmark. If a local benchmark is not available near the site, the wells will be surveyed relative to an onsite, assumed benchmark with an assigned elevation. The wells will be surveyed as described in Attachment B Section A- 3.4 44843.T04/STO5R1333/DH:ly Page 11 of 17 ©2005 Kleinfelder, Inc. October 25, 2005