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93 11117 12.37 S X16 B73 ISSI DvMATiC 1l <br />TIA FAX - ATT: JDM <br />._ oYr~u-TEC twTeRf~ Mello <br />TO: Flle -1Nyoming Fuel, February, 1881 <br />FROM: DEH <br />DATE: 17 November 1993 <br />SUBJECT: Review of 1991 shaft pre-grouting In regard to a current leakage <br />--G~Oi---C----~3---C-~--Ca-----Ci-~--SCO---~3 <br />to January 1981, DEH was provided with geological and hydrological Information from <br />Lakewood and asked to propose a pregroutlng plan for the kx:ation of ttte scheduled <br />raise boro job. DEH verbaly proposed a grouting opsratkxt from top b bottom I.e. drill <br />and grout In stages, extending the depth of each hots only after each waterbssring <br />horizon Is treated fie cUent vetoed this metfxxi on the baste of coat and reques~d a <br />proposal In which the holes would be drilled to tuY depth and grouted to stagq from the <br />bottom up, using packers. The client then Bedded to do ttte groutlrtg with their own <br />personnel plus a local driller who normally did their ~ocpkxation work. but, untorttx><atey, <br />had no grouting experience. Dynatec provided a high shear grout mboer, a paddle miter <br />and a grout pump, plus the eeMcea of DEH t0 observe and advise ~tln0 Fuel's <br />engineer, who was In charge of the operation. <br />Records Indicate that 3 hobs were drilled to total depth before DEH was scheduled m <br />arrive on site. Water acceptance tests were run on one Or more of these holes. All water <br />acceptance in these tests appeared to be assodated with the coal seams, In partlCUlar, <br />the seams at depths 108, 214 and 360 feet. <br />Attempts to grout with padksre were urtakxxesshil dw m padcere being Inadvertently <br />grouted in at depth and lost In 2 holes. Ths dedelon was then made by the cUsnt to <br />simply pump grout IrtDo each of the 3 holes from surface untll the kz~toff pressure was <br />reached. This procedure, at best, would possibly seal Off one horizon In the vldniry of <br />the injected holes. <br />With regard to the present problem, the t 981 experience indicates that the water Inflow <br />in 1'he shag could be origlnetlnp hom one Or several of the Coal seams, with those at <br />depths 108, 214 and 380 feet being the most suspect. <br />