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J. H. KLEINFELDER & ASSOCIATES <br /> File: 5-1008-21/12 :337 <br /> Revised: July 8, 1986 <br /> Page 4 <br /> It is proposed that monitoring wells at the ._ site be <br /> installed by means of the casing hammer/dual tube reverse <br /> circulation air rotary drilling procedure . Advantages of this <br /> drilling system include: <br /> o Control of potential caving sediments, since a casing <br /> is advanced as the hole is drilled; <br /> o Improved stratigraphic control, as there is a real-time <br /> return of cuttings, not diluted with side-wall slough <br /> from above; <br /> o Water yield information is available for the interval <br /> at the bottom of the casing. <br /> o The air rotary drill rig is equipped with an apparatus <br /> which filters the air from the compressor down to one <br /> micron. <br /> WELL CONSTRUCTION <br /> The materials proposed for the construction of the <br /> monitoring wells are: <br /> A. Well Casings and Screen <br /> 1 . Approximately 120 feet to 130 feet of 4-inch <br /> diameter PVC, threaded, Schedule 40 <br /> 2 . 40-45 feet of 4-inch diameter PVC slotted screen, <br /> threaded, Schedule 40, 0. 02-inch slot size. <br /> 3 . A 4-inch diameter PVC top and bottom caps. <br /> 4 . Four-foot steel locking security covers. <br /> The casing and screen shall be joined by flush threaded <br /> joints. No glues or solvents will be used in joining <br /> the casing sections. <br /> B. Filter Sand/Gravel Pack <br /> The filter space shall be _packed with a sand backfill <br /> to a depth two feet above the screened section. Filter <br /> pack design will be relatively compatible with the <br /> screen sizing and materials encountered. It has been <br /> determined that #2 , #3 sands are suitable and <br />