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E I f <br /> 25 April,2000 <br /> AGE-NC Project No 96-0232 <br /> Page 3 of 4 <br /> i <br /> S <br /> horizontal extent of MTBE-impacted ground water southwest of the site, proposed multi-level screen <br /> intervals will be placed between 10 and 20 feet bsg,between 40 and 50 feet bsg,between 95 and 105 <br /> feet bsg and between 130 and 150 feet bsg r <br /> All multi-level monitoring wells will be installed utilizing a B-95 truck-mounted,fhollow-stem drill ng.and <br /> S-inch O D`hollow-stem augers Cuttings generated dunng drilling activities will be placed on plastic <br /> sheeting and covered Rinseate will be contamenzed in properly labeled DOT-approved 55-gallon drums, <br /> and stored on-site in an area lacking public access t <br /> , <br /> Each multi-level well will be single-completed as ground water monitoring wells utilizing l 7-inch diameter <br /> I^ polyethylene(outer)tubing The inner tubing consists of multiple /s-inch diameter teflon tubes partitioned <br /> into separate chambers Each multi-level well casing will be fabricated at the factory with the proposed <br /> I perforated intervals, a stainless steel, 0 02-inch screen will be wrapped around each perforated area of the <br /> tubing Additional multi-level design literature is contained in Appendix B <br /> J After deploying the multi-level well casing in the hollow,,tem boring,a filter pack material consisting of pre- <br /> washed#212 Lonestar sand will be added through the augers to approximately two feet above each screened <br /> interval A bentonite seal (pell plug-coded bentonite pellets) will be placed between filter pack intervals to <br /> I minimize the potential for cross contamination into the screened section of the well The bentonite seal will <br /> be formed by pouring bentonite pellets into the annulus and allowing them to settle on the filter pack The <br /> remaining annular space from the uppermost screen interval will be filled to the ground surface with a <br /> I portland cement grout The grout mixture will consist of Type I/II portland neat cement and not more than <br /> 6 gallons of water per 94-pound sack of cement The grout will be placed by pumping through tremir_ie pipe <br /> A grouting inspection will be scheduled with RWQCB/PHS-EHD personnel A proposed well construction <br /> diagram is depicted in Figure 6 <br /> Installation of six (6)muni=level ground water wells should'be a more cost effective means to conduct the <br /> ongoing investigation rather than installing single completions for every clustered well area as originally <br /> Iproposed AGE anticipates the following reductions as a result of installation of multi-level wells <br /> 1 Drilling time due to the reduction of twenty-three (23) soil borings reduced to six (6) soil borings, <br /> 2 Well materials (i a sand bentonite, well casing, well vaults, grout, etc ) <br /> 3 AGE staff time as a result of the reduced drilling time <br /> 4 Regulatory permitting fees (i e encroachment fees) <br /> 5 _ Well,development time <br /> 6 Monitoring well purging time t i <br /> 7 Amount of purged ground water disposal <br /> S, <br /> t f ! Adianced GcoEnviranmental Inc <br /> w _ <br /> ii Fr <br /> , , I <br /> i <br />