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h4 K L E I N F L L D E R <br /> A-3 GROUNDWATER WELL INSTALLATION <br />' A-3 1 Monitoring Well Construction <br />' Construction details for shallow groundwater monitoring wells are as follows <br /> • The well casing are 2- or 4-inch inside diameter, flush threaded joint, schedule 40 PVC <br />' pipe <br /> • The wells are constructed in 8- or 10-inch diameter borings <br />' • Well screen sections arep erforated with 0 010- or 0 020-inch factory-cut slots <br /> • The wells are generally screened from 5 feet above to 15 feet below first groundwater <br /> The screen length is reduced if an aquitard with a minimum thickness of 5 feet is <br /> encountered If an apparent aquitard is encountered, the well is usually terminated 1 to 2 <br /> ' feet into the aquitard Effort 1s made not to screen across two aquifers If confined <br /> aquifer conditions or high vadose zone contamination are encountered, the well screen is <br /> usually not set above the depth of first encountered groundwater Wells are usually not <br /> set in areas of suspected significant soil contamination <br /> • The PVC pipe and end caps are steam cleaned prior to installation <br /> The annular space between the screen and the wall of the boring is backfilled with the <br /> appropriate clean sand to approximately 2 feet above the top of the perforated sections <br /> Based on soil logs or a sieve test, modifications maybe made regarding the size of sand <br /> to be used Installation of the sand may require that the sand be tremmied, using clean <br /> ' water <br /> A 3- to 5-foot bentonite plug is placed above the sand pack to provide a seal against <br /> surface water infiltration and to reduce the potential for cement grout to infiltrate into the <br /> water <br /> ' . The remaining annular space is filled to the surface with cement/bentonite grout <br /> The wells are secured in an aboveground or underground locking stovepipe The well <br /> ' heads may be enclosed in a water tight cement utility box set flush to the ground surface <br /> when located in a traffic area <br /> ' 20-4439-01 E02/201 1 8355 Page 4 of 9 <br /> Copyright 2001, Kleinfelder, Inc April 2,2001 <br /> 1 <br />