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' k" KLEINFELDER <br /> • The screen length is reduced if an aquitard with a minimum thickness of 5 feet is <br /> encountered If an apparent aquitard 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 />' • The annular space between the screen and the wall of the boring is backfilled with the <br /> p g <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 />' a 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 Monitorin?_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 tnsodium phosphate or non-phosphate detergent solution and rinsed in distilled water or <br /> steam cleaned prior to use in the next monitoring well <br /> 28209 T03 /ST03R1312 Page A-4 <br />' ®2101 Klemfelder, Inc September 22,2003 <br />