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z RAN c S I*-ri MA ME .`e.:.x`-i Y-'' _• :"..sur r' •moi. 6 foot-tt[ick seal of hcntonite peilets t.; placed aLive the sand pool:. 1`1,c wcil then is grouted vith bentonite ccsnent slurp' or neat ;c;nent. Tram the top of tl[e hentonve s:ai to the surface. t irountiwater monitonng wells commoniy are cnmpietcd below grade and prorectetf with:?water M tj2ht locking cover. A typical Weil construction is illustrated on i=iLure A 1. i ltc top of casing l i'OC) is surveyed by a licensed sur.°evor, and all depths to water are measured in relation to the surveyed marc: on the TOC. hlonitoc-ing Well Development- Groundwater monitoring .yells ars.: developed by surging, hailinc, or pumping until clout. r;.iatively sediment-free water is produced from the well. The length of development time varies. depending upon field conditions. Development water is contained in 55-gallon barrels, which are stored temporarily on site until disposal. GROUND V,kTER SAMPLING Prior to cotiecting a sample of groundwater from a well, the well is purged by removing three or more well volumes of water, using either a pump or a bailer. A well volume is defined as the amount of groundwater in the well casing and the sand paol. in the an space surrounding the casing, assuming a sand porosity of 35 percent. The pH and electrical conductivity of the water are measured periodically during the purging. When these parameters become relatively stable, it is assumed that fresh formation water has entered the well casing. The groundwater sample is obtained with a teflon or disposable bailer equipped with a bottom-emptying valve. To release water from the bailer with minimal aeration, the protrusion on t� bottom-ei'tprying de-ice actuates the bottom check valve and regulates the flow into the r sample bottle. The sample bottles are obtained preclearied from the analytical laboratory, and.it is specific with respect to size and material to the type of analysis to be performed. The bottle is carefully filled to the very top, in order to create a positive meniscus,and sealed with teff - tvi dally cap (septa). These precautions aid in eliminating air from tate sample. The sample inspected to ensure that no air bubbles remain within. Depending on the type of chemical analysis required,samples are preserved with acid and/or they are cooled to 4 degrees Celsi,A'S. Samples then are labeled,stored,and awspont cl in cooled ice chests to the analytical laboratory within the permissibl: holding time. QUALITY ASSURANCE PIAN ndlircr are essential uaEty of samples. Proper proper collection and ha gcollection and handling trocedures isressc tial to venom the in gri y documentation of sample co of the data.