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Reconnaissance Groundwater Sampling er from each borehole will be sampled ush or drill rods or hollow stem Groundwater using p d p k auger as temporary casing in the uppermost aquifer. Depth to groundwater measurements t the nearest one-one hundredth of one foot from existing rade and also will be made o g g , checked for the presence of separate phase product. Please note that in uncased boreholes water levels may not equilibrate due to the length of time open. Each groundwater sample will be carefully collected with a clean disposable bailer and poured into the appropriate laboratory prepared container with minimum cavitations and headspace. Each water sample will be labeled, logged onto a chain-of-custody form, and placed in a chilled ice chest on crushed ice. Data Review for Monitoring Well Placement Once the chemical data is reviewed, locations for monitoring wells will be selected. These well locations will be sent to the PHS-EHD representative for comment prior to installation. Wright had initially anticipated three (3) monitoring wells to be installed in our initial work plan dated Decembe1999. The field data from both assessments will be used to select the number of wells or more) as needed for adequate site coverage. n Monitoring Well Installation � The monitoring wells will be cased with Sch. 40 PVC ceasing, threaded together; glues will not be used. The slotted interval will be a 0.020 inch wide slots, and the annular space around the slots will be backfilled with a 2/12 sizee sand. Previous experience has shown this to be a reliable well design in fine graii]ed and stratified depositional environments. Final well design will be modified to the site-specific conditions encountered in-the borehole during drilling. Once the aquifer strata has been defined, the casing will be lowered to the bottom of the borehole, leaving a slotted interval above the occurrence of groundwater to observe for floating product. The sand pack will be placed to a point about two feet above the slots. A bentonite seal will be placed atop the sand pack, and a cement grout seal placed atop the bentonite using a tremie line, filling from the bottom to top of the borehole. A traffic rated wellhead access box and security device will complete the wellhead. i Monitoring Well Sampling and Development The monitoring wells will be developed to remove the drilling muck, grade the sand pack and provide a more complete hydraulic ' connection to the aquifer. A well development log will be kept of the well volumes removed until the water becomes clear and the amount of sand pumped is minimal. The well will be allowed to recover for at least 72 hours prior to sampling. The well casing will be surveyed to a known datum to accurately measure groundwater elevation contours. i Well Casing Elevation Survey The monitoring well casing elevations will be surveyed to a known elevation datum so t accurate'groundwater elevations and flow gradient can be measured. :a M&M Builders Supply 4 10/16/2000 Wright Project No. 4669 p