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Section No 6 <br /> Revision No 1 <br /> Date January 13, 1992 <br /> Page 37 of 55 <br /> ■ depth of installation, <br /> ■ the presence of chemicals in the subsurface, <br /> ■ the method of installation, <br /> ■ the primary and secondary use of the well <br /> Prior to installation, all well casing string and caps will be <br /> thoroughly steam-cleaned. The well casing materials will be inspected by the <br /> field geologist to ensure that the casing is free of grease, paint, tape, <br /> glue, and other foreign materials All casing strings and caps will be <br /> measured prior to installation Casing string lengths will be recorded in <br /> the well construction log When possible, flush threaded well casing <br /> materials will be used to facilitate field assembly No glues or solvents <br /> shall be used to connect the casing strings Prior to installation, the <br /> field geologist will review the available lithologic data and determine the <br /> interval within the water-bearing unit to be screened The total depth of <br /> the borehole and water level measurements will be measured and recorded prior <br /> to installing the casing The slot size for the well screen will be selected <br /> after the gravel pack is specified from field sieve analyses (described <br /> below) The slat size will be small enough to hold out between 80% and 90% <br /> of the gravel pack, depending on the uniformity of the gravel pack <br /> For wells constructed using HSA drilling methods , 2-inch casing will be <br /> constructed in HSA of at least 6-inches I D , and 3- to 4-inch casing will be <br /> constructed in an HSA of at least 8-inches I D Wells with a diameter <br /> greater than 4 inches will be constructed using rotary wash methods The <br /> screen and casing will be suspended from the ground surface such that the <br /> screen interval is adjacent to the desired interval to be monitored The use <br /> 6-37 <br />