SITE INFORMATION AND CORRESPONDENCE

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.� 4 Hf1MICK-f-IfAMEA Mr. Verrill M. Norwood 13 January 1997 Page 2 A phased approach is proposed to assess the vertical extent of the VOCS in groundwater. A deep soil boring will first be drilled to characterize the soil stratigraphy beneath the ponds and determine if a confining layer separates the shallow aquifer from deeper aquifers. If a confining layer is present, the bottom of the shallow aquifer would represent the vertical extent of contamination and additional investigation would be limited to one monitoring well screened below the confining layer. If the shallow aquifer is very thick and lacks a continuous base, additional investigations would focus on monitoring of intermediate zones within the shallow aquifer. SHALLOW MONITORING WELL CONSTRUCTION AND SAMPLING Monitoring Well Design Four monitoring wells will be installed at the approximate locations shown on Figure 1. The wells will be 2-inch PVC casing with locking caps and will be completed above grade. The new wells will designed to match the existing wells and will be screened over the interval of 13 to 23 feet below the ground surface. Well screens will be fabricated with 0.020-inch factory cut slots. The annual space around the well screen will be filled with No. 3 sand which will extend three feet above the well screen. A three-foot bentonite seal will be placed above the gravel pack. The remaining annular space will be filled with a neat cement grout. The well will be completed in a vault with a locking cap. The well locations will be surveyed and tied in to the existing well network. Well Installation Borings for the wells will be drilled by hollow stem auger methods using 8-inch diameter augers. Soil samples will be collected from each borehole at five-foot intervals, beginning at the ground surface for logging and analytical purposes. Samples will be collected by advancing the auger to a point immediately above the desired sampling depth interval and then driving a modified California split-spoon sampler lined with three brass tubes into the undisturbed soil. The sampler will be driven using a 140-pound hammer with a 30-inch free-fall drop, in accordance with ASTM Standard Method D1586-84, "Penetration Test Split Barrel Sampling of Soil." Blow counts will be recorded in six-inch intervals for every sampling event. To minimize the potential for cross-contamination, all augers and associated equipment will be cleaned with a high-pressure hotwater washer prior to drilling each boring. The split-spoon sampler, associated sampling equipment and brass sample tubes will be cleaned with a trisodium phosphate wash and rinsed with water prior to collecting each soil sample.