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Ge010g0tTCek94(rs/nc. • • Page ' Work Plan George's Service Project No.425.2 August 14,2002 50-Foot Well The monitoring well will be constructed using 2.0-inch diameter PVC casing with flush threads. A short screen (2.5-feet in length) will be used. A#3 sand filter pack will surround and extend two feet above the 0.020 inch screened interval. A weighted bentonite pellet seal will be installed. A surface seal of neat cement grout (augmented with< 4% bentonite) will be installed via a tremie pipe. The well will be secured with a locking watertight cap encased in flush mounted traffic rated well box. b OU S 1( S) b�j rS 1' u d' Construction details are as follows: 6�P��`s Well o. Dia./Tl) Green Slot Sand PackTrans. Seal Grout Seal san -surrace 1 This is approximately the same construction as MW-102 and MW-107. Figure 3 is a schematic of monitoring well construction. ' After the well sealing materials have set (>24 hours) the well will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The well will be purged and groundwater samples collected no sooner than 48 hours 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. ' The top of casing measuring point and the "X" and "Y" coordinates for the new wells will be surveyed as required under AB-2886. 2.2 Groundwater Monitoring The groundwater in the new wells will be sampled no sooner than 48 hours after well development. This plan calls for one year of monitoring on a quarterly basis. As suggested ' in the July 10, 2002 letter, the monitoring frequency of MW-105, MW-107 and MW-202 should be dropped to annually. Depth to water measurements should remain quarterly in these wells. Quarterly groundwater samples will also continue to be collected from three r ' domestic wells associated with the site; 1600A Durham Ferry Rd., 1697 Durham Ferry Rd., and 31448 Highway 33. The following is a procedure for the sampling of groundwater from the wells: Before sampling is attempted each well will be sounded for depth to water and then a clear disposable bailer will be used to determine if floating product is present. The well will be purged of at least 3 well volumes of stagnant water using either a submersible pump or a Waterra purging system. Purging will continue until the temperature, conductivity, and pH of the groundwater has stabilized (<10% variation between three readings) indicating that ' formation water representative of aquifer conditions is entering the well. These water quality parameters are measured at intervals of each well volume purged. A stainless steel or disposable plastic bailer will be used to collect each sample. Care will be taken to minimize sample agitation from the initial filling of the bailer to the transfer of the sample to the VOA vial. Once the sample container is filled and capped, the bottle will be inverted, tapped, and checked for head space bubbles. The sample container is identified 1