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disposition Drums of equipment decontamination nnsate and purge water were also stored at the site pending sample analysis Disposal of these wastes will be the responsibility of the owner, but Environeering, Inc will provide guidance and assistance with waste disposal arrangements • 3.3 Well Construction and Development Monitoring well MW-4 was constructed in one (1) of the soil bonngs The monitoring well was cased with 2-mch diameter threaded, factory-slotted and blank Schedule 40 PVC casing pipe The perforated interval in the well (27 ft to 50 ft bgs ) consists of slotted casing with 0 020-inch wide by 1 5-inch long slots, with 42 slots per foot A threaded PVC cap was secured to the bottom of the casing, no solvents or cements were used The well casing was purchased pre- cleaned, and arrived at the site still stored in its original plastic wrapping After setting the casing inside the hollow-stem auger, #3 filter sand was poured into the annular space between the well screen/casing pipe from the bottom of the bore hole (50 ft bgs) to 2 feet • above the top of the well screen (25 ft bgs ) The sand was placed slowly and the filling process was checked frequently with a weighted measuring tape to prevent bridging and creation of void spaces in the filter pack A 2-foot thick bentonite plug, constructed of bentonite chips, hydrated in place, was set above this filter material to prevent cement grout from entering the filter pack A neat cement-grout rruxture was placed into the annular space from the top of the bentonite plug within two feet of the surface A traffic-rated flush-mount well vault was installed around the wellhead, which was set with concrete After the sand pack was installed and prior to setting the bentonite seal, the well was thoroughly developed by surging for 10 minutes and purging 20 gallons to remove residual drilling material (grout cement) and native silt and clay from the filter pack Following construction, the well was • then allowed to settle and equilibrate for at least 72 hours, prior to further purging and sampling . All purged water was contained in DOT-approved 55-gallon drums, was properly labeled and was temporarily stored onsite, pending laboratory analysis r 3.4 Well Purging and Groundwater Sampling t The water level in the monitoring well was measured prior to surging and purging on 7 • Environeering,Inc Project No 00-01108 6