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Section No 6 <br /> Revision No 1 <br /> Date January 13, 1992 <br /> Page 40 of 55 <br /> ■ For coarse non-uniform water-bearing zones, UC >5 0, use a <br /> multiplier of or _near nine, maintaining a UC <2 5 for- the gravel <br /> pack -- --_ _ <br /> The thickness of the gravel pack will be no less than 2-inches and no <br /> greater than the radius of the casing <br /> Prior to installing the filter pack materials, a calculated volume of <br /> material needed to fill the annular space to a desired level will be <br /> obtained Dry gravel pack material may be placed by free-fall with the HSA <br /> The HSA will be slowly removed as -the gravel pack material fills the annular <br /> s <br /> space The position of the pack will be periodically verified using a <br /> weighted sounding device or staff If sand bridges occur within the HSA, the <br /> bridge will be broken by washing the pack material down the augers using <br /> formational or deioni.zed water <br /> For-the-deeper-wells-drilled-using-rotary-wash_methods,_the-filter pack v --- <br /> material is placed at the desired depth by gravity feed through a pipe <br /> (tremie method) . Prior to installing the filter pack, the drilling fluid <br /> will be thinned to facilitate well construction A tremie pipe with a <br /> minimum I D of 2 inches will be used for filter pack materials with UC <2 5 <br /> Larger diameter tremie pipes will be used for coarse-grained filter pack <br /> materials or materials that have a UC >2 5 Formational or deionized water <br /> will be poured along with the gravel to prevent bridging The distribution <br /> of the gravel pack will, be checked regularly using a weighted measuring <br /> device or the tremie pipe itself The tremie pipe will be slowly raised as <br /> the gravel pack material fills the annulus <br /> 6-40 <br />