ARCHIVED REPORTS_XR0003138 - Laserfiche WebLink

Home Browse Search

KLEINFELDFR A-3 GROUNDWATER WELL INSTALLATION ' A-3,1 Monitoring Well Construction ' 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 ' 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 5 feet above to 15 feet below first groundwater The screen length is reduced if an aquitard with a minimum thickness of 5 feet Is encountered If an apparent aqultard 1s encountered, the well is usually terminated 1 to 2 feet into the aqultard Effort 1s made not to screen across two aquifers If confined aquifer conditions or high vadose zone contamination are encountered, the well screen 1s ' 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 clea,ied 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 of the sand may require that the sand be tremmied, using clean ' water • A 3- to 5-foot bentonite plug Is placed above the sand pack 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 cementfbentonite grout • The wells are secured in an aboveground or underground locking stovepipe The well heads ' may be enclosed in a water tight cement utility box set flush to the ground surface when located In a traffic area 1 20-4439-01 E01/2000R726 Page A-4 Copynght 2000 Klemfelder, Inc October 16 2000 1