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tk%j KLEINFELOER <br /> • The screen length is reduced if an aquitard 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 aqultard 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 />' • 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 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 /> • 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 />' 0 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 be enclosed in a water tight cement utility box set flush to the ground surface when <br /> located in a traffic area <br /> A-3 2 Monitoring 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 /> 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 the potential for cross-contamination between wells, developing equipment is washed <br /> in a trisodium phosphate or non-phosphate detergent solution and rinsed in distilled water or <br /> steam cleaned prior to use in the next monitoring well <br /> A-3.4 Well Survey <br />' 18748 T02/STO3R081 Page A-4 <br /> ©2003 Klemfelder, Inc January 23,2003 <br />