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Clayton screens and casings used are in a contamipant-free condition when placed in the ground No thread lubrication is used, other than teflon tape, for connecting the casing segments. Wells extend at least 10 feet into the upj�er saturated zone, but do not extend through any clay layers greater than 5 feet that are below the shallow water table. Factory-slotted casing is used throughout and extends at least 2 feet above the permeable water-bearing zone The top of the well is solid casing. The annular space of the borehole is backfilled with washed, kiln-dried sand to a point at least 1 foot above the slotted screen A seal above the filter pack is formed by placing a 1- to 2-toot layer of bentonite pellets on top of the sand The bentonite pellets are moistened by pouring clean tap water down the hole so that they can expand and seal the annulus. A neat cement grout is placed above the bentonite seal and brought to the ground surface. Well casings are protected from surface contamination, accidental damage, and unauthorized entry or tampering with water-tight loclnng caps on the well casings The caps are usually surrounded by a concrete vault. Wells are clearly identified with a metal tag or other device where the following mformation is recorded- well number, depth to water, depth of well, casing data mcluding location of screened interval i ` The well seal in newly developed wells must set up for 48 to 72 hours prior to development Since development of the well can volatilize contaminants present, the well must also settle for at least 48 to 72 hours between development and the first purging/sampling incident. All monitoring wells are mttially developed to clean the well and stabilize sand, gravel, and i disturbed aquifer materials around the screened internal perforations Wells are developed f 41 by pumping (or bailing) and surging until water turbidity and specific conductance stabilize In some cases,where wells are installed in low permeability formations and the wells purge dry, the well is allowed to recover and is purged dry three times Clean tap water is introduced into the well if it does not rtcover rapidly enough. } Pending results by laboratory analysis, purge water from well development and sampling is placed Into DOT-approved drums, labeled with the name of the site, address,well number, 14 and left at the site. Uncontaminated water may be disposed of by the client. Water found to contain levels of contaminants above local or state action levels requires that the client dispose of it in accordance with hazardous waste requirements. At the client's request, we can assist witi, the disposal of contaminated purge water. �g To collect a representative sample of the groundwater, stagnant water within the well casing E and filter material must be purged and fresh aquifer water allowed to replace it. The water is I purged from the well by pumping or bailing at least three well volumes. Well volumes are calculated by measuring depth to groundwater to the nearest 0 01 foot upon arrival at the well before any purgmg has begun. Groundwater samples are collected only after purging has F $ � � 3