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Stanfield & Moody Property Evaluation November 8, 1989 Page #2 contamination is encountered. Both driven samples and auger returns will be screened in the field for hydrocarbon contamination using thin layer chromatography. All samples retained for chemical analysis will be properly labeled and placed in an iced cooler for transport to the laboratory. Chain-Of-Custody protocol will be maintained on all samples retained for chemical analysis . The temporary wells will be constructed of two inch diameter, schedule 40 , PVC blank casing and 0 . 02 slot screens. Typically, five feet of perforated casing will extent above the existing static water level to detect any floating product that may be present. The perforated casing will be extended below the static water level into the water bearing unit to a depth of feet below the static water level . The annular space between the perforated casing and the boring wall will be sand packed with Lapis Luster #1c sand (see Figure 2) to a level two feet above the top of the screened interval . Due to the ephemeral nature of the monitor wells no grout will be emplaced until the well is abandoned. Four inch diameter pvc temporary casing may be used to stabilize the hole until abandonment. The well will be abandoned after ground water sampling has been performed, about twenty four hours after drilling. All well casing will be pulled and the boring backfilled by tremming in a cement/ bentonite grout containing no less that 1034 pounds of cement and no more than 50 pounds of bentonite per cubic yard of grout. Bentonite is added to reduce shrinkage cracks in the grout seal . 2) WELL DEVELOPMENT The wells will be briefly developed to improve hydraulic continuity with the native soil . Development will be performed using pumping, bailing and/or surging of the wells. The volume of all water extracted during development will be recorded along with regular pH measurements. Development will be continued until the wells produce little or no fine sediment and pH readings have stabilized. 3) GROUND WATER SAMPLE COLLECTION Prior to the collection of ground water samples each well will be tested for the presence of free floating product. The well will then be purged. Normal purging will consist of the removal of between three to five casing volumes of water. In the event of slow recovery, the well will be completely evacuated of one casing volume and the sample taken after recovery. Both purging and sampling will be performed using a Teflon bailer cleaned prior to sampling with laboratory-grade detergent and triple rinsed with distilled water.