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I , Page 6 MONITOR WELL INSTALLATION Upon completion of drilling on 30 April and 1 May, 1992, boreholes B-1 through B-3 were reamed to remove all slough material and were converted to monitor wells MW-4 through MW-6, respectively The wells were constructed with two-inch diameter Schedule 40, factory threaded ' and slotted polyvinyl chloride (PVC)casing A slot size of 0 020 inches was selected based on the knowledge that the predominant soil type in this area is fine sands and muds The slotted interval extends from 30 feet below ground surface to 45 feet below ground surface The annular space ' around the 0 020 inch slotted sections of casing was packed with Lonestar#3 sand (LS#3 = 15 mm) as filter material, from the bottom of the borehole to 29 feet below ground surface, for MW-4 and MW-5 The slotted interval extends from 25 feet below ground surface to 40 feet below ' ground surface The annular space around the 0 020 inch slotted sections of casing was packed with Lonestar#3 sand(LS#3 = 15 mm) as filter material, from the bottom of the borehole to 24 ' feet below ground surface for MW-6 Well completion logs are included in Appendix B A bentonite seal was placed in MW-4 from 27 feet below ground surface to 29 feet below ground surface, in MW-5 from 28 feet below ground surface to 29 feet below ground surface, in MW-6 from 23 feet below ground surface to 24 feet below ground surface The bentonite was hydrated with detonized water The remaining space from the bentonite seal to the surface was completed with neat cement grout The well casing was fitted with a locking well cap to prevent tampering A flush-mounted, traffic-rated Christy box was cemented in place over the well, and slightly above grade, to prevent infiltration by soil and surface runoff 1 1 100 Shoreline Hwy, Suite 295 B - Mill Valley, CA 94941 - (415)381-6456 FAX (415) 389-0423