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� J f k4 KLEINFELDER i B-3 TEMPORARY GROUNDWATER WELL INSTALLATION B-3.1 Temporary Monitoring Well Construction Construction details for shallow temporary groundwater monitoring wells are as follows: j The well casing are 2- or 4-inch inside diameter, flush threaded joint, schedule 40 PVC pipe. • The wells are constructed in 8-or 10-inch diameter borings. • Well screen sections are perforated with 0.010- or 0.020-inch factory-cut slots. • The wells are generally screened from first. groundwater to 10 feet below first groundwater. The screen length is reduced-if an aquitard with a minimum thickness of S feet is encountered. If an apparent aquitard is encountered, the well is usually terminated 1 to 2 feet into the aquitard. Effort is made not to screen across two aquifers. If confined aquifer conditions or high vadose zone contamination are encountered, the well screen is usually not set above the depth of first encountered groundwater. Wells are usually not set in areas of suspected significant soil contamination. } • The PVC pipe and end caps are steam cleaned prior to installation. • The annular space between the screen and the wall.of the boring is backfilled with'-the appropriate clean sand to approximately 2 feet above the top of the perforated sections. Based on soil logs or a sieve test, modifications may be made regarding the size of sand a to be used. Installation of the sand may require that the sand be,tremmied, using clean water, B-4 GROUNDWATER MEASUREMENTS B-4.1 Water Level Measurements Water level measurements are made in the wells prior to purging and sampling the wells. ` Measurement protocol is as follows: I 1.. The water level probe is decontaminated in a trisodium phosphate or non-phosphate detergent wash, followed by a distilled water rinse, prior to use in each well. 2. Water level measurements are made using a conductivity-based water-level meter. Depth-to-water is generally measured from a surveyed mark on the north rim of the PVC well casing. r f 4 20-YP8-l 61/2018P 179 Page B-3 �" { © ]998, Kleinfelder, Inc. June 22;'1998 r