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CLEARWATER G R O V t' I N C Enmronmenta! Sermces De coon of Well NIW-5.111stallatiogof Wells—MW-5. MW-7&MW-8 Deve o mens and Survey As mentioned earlier, well MW-5 was damaged during recent resurfacing activities Field observations indicate that approximately several feet of the uppermost part of well casing and protective box were damaged, however, the well casing and borehole remain accessible Monitonng well MW-5 will be destroyed by overdnlling and grouted with cement properly Monitoring well MW-5 will be re-installed just southeast of its previous location (Figure 2) The new location of MW-5 and locations for proposed monitoring wells MW-7 and MW-8 will delineate southeast section of this plume Prior to drilling, Clearwater will prepare site specific Health and Safety Plan for drilling activities Prior to conducting and dnlling, the site will be marked by Underground Service Alert (USA) to identify utilities leading to the site Appropriate well installation permits will be obtained prior to the start of fieldwork All fieldwork will be conducted in accordance with Clearwater's Field Protocols (attached) A hollow-stem auger truck mounted dell-ng will be used accomplish drilling and well Installation Clearwater personnel will supervise a C-57 licensed dnller in these activities The boring will be advanced to a depth of 36 feet bas for soil sample collection,the well will be constructed to a total depth of 25 feet bgs The lower t f feet of these borings will be filled and sealed with clay pellets The wells will be constructed of clean, flush-threaded, PVC well materials Well screen, with 0 02-Inch perforations, will extend from 25 feet bgs to 5 feet bgs, and blank casing will be extended to ground surface A filter pack of Lonestar . #3 sand will extend from the bottom of each boring to one foot above the screened interval The filter pack will be sealed by a two-foot layer of hydrated bentonite The remaining annular space will he filled with cement and a tamper-resistant box will be concreted in place over the wellhead Proposed well construction details are shown on Figure 3 The wells will be developed by surging and bailing Development will involve the removal of water from each well until such time that it is relatively free of sediment, and pH, temperature, and conductivity parameters have stabilized It is anticipated that the water volume removed will not exceed ten saturated casing volumes Augers will be steamed cleaned between use Rinseate and soil cuttings will be stored on-site in labeled 55-gallons drums pending future removal and disposal CIearwater will survey the top of casing elevation for the new wells relative to a permanent benchmark, accurate to within ±0 01-feet Groundwater Monitorm2 Following installation of new monitoring wells, Clearwater recommends continued monitoring and sampling of groundwater at the site for the next several quarters to further evaluate trends in residual dissolved-phase contaminant levels and potential variability in seasonal hydrogeologic conditions All sampling will be performed in accordance with Clearwater's Field Protocols(attached) Clearwater recommends the following sampling schedule Ms Lon Duncan 4 November9 1999