FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

KLEINFELDER 13-3 GROUNDWATER WELL INSTALLATION 13-3.1. Monitoring* Well Cunstrrictirin Construction details for shallow groundwater monitoring wells are as follows: • The well casing are 2- or 4-inch inside diameter. flush threaded .point, schedule 40 PVC i pipe • The Nvells are constructed in R- or l0-inch diameter borings. • Well screen sections are perforated with 0.010- or 0.020-inch factory-cut slots. • The wells are generally screened [.'rom 5 feet above to 15 feet below first ground,,vater. The screen length is reduced if an aquitard with a minimum thickness of 5 feet is encountered. if an apparent acluitard is encountered, the well is usually terminated i to 2 feet into the aquitard. Effort is made not to screen across two aquifers. If confined aquifer Conditions or high vadosc 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 oFsuspected significant soil contamination. • The PVC pipe and end caps ai-e 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 to be used. Installation ofd Ehe sand may require that the sand be tremmied. using clean water. • A 3- to a-moot bentonite plug is placed above the sand pact: to provide a seal against surface water infiltration and to reduce the potential for cement grout to infiltrate into the water. • The remaining annular space is filled to the surface with cement/bentonite grout. • The wells are secured in an aboveground or underground locking stovepipe. Tile well heads may be enclosed in a water tight cement utility box set flush to the ground surface when located in a traffic area. B-3.2 Monitoring Well Development The wells are developed to reduce the effects of drilling, on the formation and to increase the effective hydraulic radius of the wells. 20-2864-02.E03/2019RO32 Page B-4 Copyright 1998. Klein'CILICr_ 1110. January 14, 1999