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Geological Technics Inc. Page 3 Bank of Stockton-Western Lift Remedial Feasibility Study-Work Plan Project#358.3 . September 28,1995 monitoring. The remainder of this section discusses the installation of these two wells. 2.1. Well Installation ' To further investigate the extent of gasoline range petroleum hydrocarbon contamination in the soil and groundwater environments, and to serve as a pilot ' BV/SUES facility, Geological Technics Inc. proposes to install two dual purpose wells (VEW-1 and VEW-2) in the down-gradient direction from the over-excavated tank pit. The wells will be used both for vapor extraction pilot testing as described ' in the sections below. The water gradient has been calculated by Geological Audit to be about 0.0015 foot per foot on a NE bearing. Therefore monitoring well VEW-1 is proposed to be installed about 25 feet to the northeast of the pit a and VEW-2 is proposed to be about 15 to 20 feet further down gradient. ' The well borings will be drilled using a 10 inch diameter hollow stem auger rig operated by V&W Drilling (C57# 710678). Soil cuttings will be placed in 55-gallon drums and sealed until characterized. Wells VEW-1 & 2 will be constructed using 4.0 inch diameter PVC casing with flush threads. The screened interval in VEW-1 and 2 will extend from 10 feet below the lowest known water table to 15 feet above the highest known water table. Groundwater is expected to be located at about 35 to ' 40 feet below grade. A #3 sand filter pack will surround and extend two feet above the 0.020" screened interval. Before installing the bentonite seal, the well will be surged to assure proper filter pack installation. A granular bentonite transition seal will be installed and hydrated. A surface seal will be achieved by pumping a neat cement grout (augmented with < 4% bentonite) via a tremie tube. The wells will be secured with a locking watertight cap encased in flush mounted traffic rated well box. After the well sealing materials have set (>48 hours) the wells will be developed (using mechanical surging and pumping, or bailing methods) until clear water is obtained. The well will be purged and groundwater samples collected after well development. All development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged. ' 2.2 Soil Sampling Procedure Soil samples will be collected for geological and analytical evaluation. Continuous ' coring will be performed in VEW-1, and samples will be collected at 5 foot intervals in VEW-2. A boring log providing sediment description using the U.S.C.S. and field observations will be maintained by a registered geologist. The well VEW-1