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Ms. Anne P. Conner 6 10/9/2007 Pacific Gas&Electric Company 3.1 Shallow Zone Soil Sampling A total of ten shallow zone soil samples will be collected from five proposed locations within the Pond 3 boundary (Figure 1-2). Direct push technology' will be utilized to create an approximate 2-inch borehole with "dual tubes" to a total depth of 30 feet bgs. Soil samples will be collected from both native materials immediately below the pond backfill and at approximately 28 to 30 feet bgs. Samples in native materials immediately below the pond backfill will be analyzed only for chloride, sodium, sulfate, barium and pH, and samples collected from 28 to 30 feet will be analyzed for the following: • Chloride and Sulfate— EPA method 300.1 • pH — EPA method 150.1 • Total Metals — EPA method 6010/6020 Total metals will include CAM17 metals (Ag, As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, Ti, V, Zn) plus Al, Ca, Mn and Na. Direct push soil samples will be collected in thin-walled (acetate) sample tubes, with the ends covered by Teflon TM liners and secured with plastic caps. Samples will be stored in coolers with ice until shipment. Upon completion of soil sampling, each "dual tube" borehole will be utilized to construct a temporary 1-inch piezometer. Temporary piezometers will be constructed of 1-inch Schedule 40 polyvinyl chloride (PVC) blank casing and will extend from approximately one foot above ground surface to 25 feet bgs. A five foot section of 0.01-inch factory slotted PVC will be attached to the blank casing and will extend from 25 to 30 feet below ground surface (bgs). Filter pack sand (size #2/12 or equivalent) will be installed around the annulus of the piezometer to a depth of 24 feet bgs. 3/8-inch bentonite chips will then be placed to 23 feet bgs and hydrated. Cement grout slurry, including 5% bentonite powder, will be used to complete each temporary piezometer to the surface. Temporary piezometer construction details are provided on Figure 3-1. 3.2 Shallow Zone Groundwater Sampling Prior to sampling, each temporary piezometer will be developed. Piezometer development will consist of surging each piezometer (probably using a small-diameter bailer) for a period of between 15 and 30 minutes. Upon completion of surging a minimum of three well volumes will be purged (either with the small-diameter bailer or with a peristaltic pump) from each piezometer. More well volumes might be purged if groundwater clarity does not indicate low suspended solids. Purging will be slowed or stopped if the temporary piezometer is purged dry. Each temporary piezometer will then be allowed to stand for a minimum period of 72 hours prior to sampling. Low Flow/Micro-Purge groundwater sampling will be conducted for each temporary piezometer in accordance with SOP EI-FS111, Low Flow/Micro-Purge Well Sampling (Shaw, 2006e) or equivalent. In summary, a peristaltic pump will be used to purge each piezometer at a rate of 0.1 to 0.5 liters per minute (Umin). The purge rate will be adjusted such that it does not exceed the well recharge rate. During purging water quality 1 Although direct push is the preferred technology,in requesting bids from several drillers,they will have the option of proposing hollow-stem augers and California split-spoon samplers to meet the time constraints in which the work has been authorized for completion.