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0 • Radial distribution and migration of contaminants was assumed in selecting the . proposed boring locations Please Note AGI may change the boring locations as site conditions warrant, however, all changes in locations and/or depth will be approved by the County inspector prior to implementation of the change An example of field conditions that would warrant a change in location would be excessively high concentrations detected at 10, 15, and 20 feet in TH-2 would prompt adding a boring further east of TH-2 to find the lateral plume boundary. 40 Methods The following sections will describe in detail the methods to be employed in implementing this workplan 4.1 Bonng Methods The bonngs Anll be advanced using a CME 75 ng, or equivalent, with a six inch or larger diameter hollow stem continuous flight auger in accordance %nth ASTM Method D 1452-80 for soil investigations and sampling by auger bonngs The augers will be steam cleaned prior to drilling each boring. The lithology and other pertinent data will be recorded on a field boring log in accordance with Method D 2488-84 for visual description and identification of soils Cuttings and other spoil from the bonngs Anil be placed in appropriate D O T. approved 55-gallon drums until verified, with analytical results, whether or not the soil is contaminated If the material is contaminated, a written plan will be submitted by the facility operator to the County for their approval before treatment and/or disposal occurs Disposal will be the responsibility of the Facility operator and occur within 90 slays of completion of drilling Backfilling of any boring in which contaminants are found or suspected or not found %rill occur by pouring a bentonite cement slurry. 4.2 Soil Sampling Soil samples will be collected through the auger in 2-inch diameter brass sleeves driven in a split spoon sampler by a 140 pound hammer with a 30-inch drop in accordance with ASTM Methods D1586-84 for split-barrel sampling of soil and D1587- 83 for thin-walled tube sampling of sods. The brass sleeves and sampler will be steam cleaned prior to each use Soil samples will be driven at depths of 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 feet in each boring depending on total depth The blow counts, recovery, and lithology will be recorded on the field logs Lithology will be described by an experienced environmental geologist under the direct supervision of a California Registered Geologist in accordance with ASTM procedure D2488-84 (Standard Practice for 5of12