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RPR 20 '94 03:51PM OCDEI•J PROJECTS ENVIRONMENTAL DPT P.7/10 geotextile fabric for additional sediment filtering ability. 3. 'The well will be screened a minimum of ten (10) feet below the groundwater surface. if an apparent aquitard is encountered, the well will be terminated 1 to 2 feet into the aquitard. Efforts will be made not to screen across two aquifers. If confined aquifer conditions or high vadose zone contamination are encountered,the well screen will not be set above the depth of first encountered groundwater. 4 The well will be screened from the bottom of the well to a depth of approximately five (5) to ten (10) feet above the groundwater surface to accommodate future fluctuations in ground water elevation and to permit installation of sufficient sanitary and surface seal to prevent surface water infiltration. 5. The PVC pipe and end cap will be, steam cleaned prior to installation. 6. The filter media used to pack the annulus adjacent to the well screen will be selected so as to be able to adequately filter out sediment after sufficient well development has occurred. The annular space between the screen and the wall of the boring will be backfilled with the appropriate clean Ione Star Industries 0130 or 2/12 Monterey sand to approximately 2 feet above the top of the perforated sections. The well screen will also be wrapped in geotextile to provide additional filtering. Based on soil logs or a sieve test, modifications may be made regarding the size of sand to be used. Installation of the 0/30 sand may require that the sand be tremmied, using clean water- In this event, a sample of the tremie water will be collected, unless the source is thought to be clean_ 7. A 3- to 5-foot bentonite plug will be placed above the sand pack to provide an annular seal against surface waxer infiltration and to reduce the potential for cement grout to infiltrate into the water. 8. The remaining annular space will be filled to the surface with tremmied cementlbentonite grout (surface seal) to the surface. 9. The well will be secured in a below-ground locking stovepipe and the well head enclosed in a water-tight utility box set flush to the ground surface. Mom—ftoring,Well Development The new well will be developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the well. The monitoring well will be developed 24 to 48 hours after its installation to allow the grout to set Additionally, the existing wells may be redeveloped az necessary. 2