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' k''q KLEINFELDER <br /> * The screen length is reduced if an aqultard with a minimum thickness of 5 feet is <br /> encountered If an apparent aqultard is encountered, the well is usually terminated 1 to 2 feet <br />' into the aquitard Effort is made not to screen across two aquifers If confined aquifer <br /> conditions or high vadose zone contamination are encountered, the well screen is usually not <br /> set above the depth of first encountered groundwater Wells are usually not set in areas of <br />' suspected significant soil contamination <br />' • The PVC pipe and end caps are steam cleaned prior to installation <br /> 0 The annular space between the screen and the wall of the boring is backfilled with the <br /> 1 appropriate clean sand to approximately 2 feet above the top of the perforated sections <br /> Based on soil logs or a sieve test, modifications may be made regarding the size of sand to be <br /> used Installation of the sand may require that the sand be tremmied, using clean water <br /> 1 • A 3- to 5-foot bentonite plug is placed above the sand pack to provide a seal against surface <br /> water infiltration and to reduce the potential for cement grout to infiltrate into the 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 heads <br /> may b e e nclosed I n a w ater t fight c ement u tllity b ox s et flush t o t he g round s urface w hen <br /> located in a traffic area <br /> A-3.2 Mondorme Well Development <br /> The wells are developed to reduce the effects of drilling on the formation and to increase the <br /> effective hydraulic radius of the wells <br />' Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to <br /> set Each well Is first sampled with a clear disposable bailer to visually inspect for a hydrocarbon <br /> t layer or sheen If no product layer or sheen is observed on the water, the well is developed by <br /> surging, pumping, or bailing Surging along the screened interval of the well is performed to <br /> draw the sediment from the formation into the filter pack and the well, and to set the sand pack <br />' Development continues until the discharge runs relatively clear of fines Approximately 5 to 10 <br /> well volumes are generally removed from each monitoring well Discharge water is stored in 55- <br /> gallon drums and left on site for later discharge or disposal by the client, depending on laboratory <br /> results The drums are labeled with the date, well number, and a contact person and phone <br /> number <br /> A-3.3 Equipment Decontamination <br /> ' To reduce theP otential for cross-contamination between wells, developing equipment is washed <br /> in a trisodium phosphate or non-phosphate detergent solution and rinsed in distilled water o r <br /> steam cleaned prior to use in the next monitoring well <br /> i <br /> 1 <br /> 18748 T02/STO2R795 Page A-4 <br /> 02002 KEemfelder,Inc December 3, 2002 <br />