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.y "f Claytart - E�'1'IHOY.StENTAL CONSULTANTS screens and casings used are in a contaminant-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 upper saturated zone, but do not extend through any clay layers greater than S 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-foot 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 5-an 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 „ authorized entry or tampering with water-tight locking caps on the well casings. The caps are usually ssurrounded by a concrete vault. Wells are clearly identified with a metal tag or other device where the following information is recorded: well number, depth to water, depth of well, casing data including Iocation of screened interval. The well seal in newly developed wells must set up for 48 to 72 hours prior to development. i 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 initially developed to clean the well and stabilize sand, gravel, and disturbed aquifer materials around the screened internal perforations. Wells are developed by pumping (or bailing) and surging until water turbidity and specific conductance stabilize: In some cases,where wells are installed iLrl low permeability formations and the wells purge ' dry, the well is allowed to recover er and is purged dry three times. Clean tap water is introduced into the well if it does not°recover 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, iE 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 i dispose of it in accordance with hazardous waste requirements. At the client's request, we can assist with the disposal of contaminated purge water. ... ........... a � To collect a representative sample of the groundwater,stagnant water within the well casing € and filter � material must be burped and fresh aquifer water allowed to replace it. The water is purged from the well by pumping or bailing at least three well volumes. Well volumes a-e calculated by measuring depth to groundwater to the nearest 0.01 Fant upon arrival at the well before any purging has begun. Groundwater samples are collected only after purging has 3 am"dnv