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., <br />ID~ RUG 16'95 <br />• <br />DIVISION OF MINERALS AND GEOLO( <br />Oepar[meel of Natural Rewwces <br />7313 Sherman 5[., Room 215 <br />Uenver, CGI0rad0 80207 <br />Vhons: (3071 8663567 <br />F •R: l7Gll 632.8106 <br />RATS: 3rir 15, <br />1995 <br />T0: Berha3n Keffalaw <br />FR~I'4: Jim Pendleton <br />R8: CRBSS0N MINE Tec <br />li) Und®rdr yer <br />(Z) Carlton Tailiaga <br />{PQrmit No: <br />Spec Revisions <br />Ror Ron4r <br />Govo•nor <br />I~rnt{ S. LorlslraA <br />Eut~~ivx Oirencr <br />hlichrd B. long <br />Olvislon Dlreclo• <br />9aqunnca <br />Lift Thickness Iacreaae <br />M-80-244) <br />in rssponse to your request, I have; (1) reviewed the two <br />spoci.fication modification requests received from John Hardaway of <br />CC&VG, (~) participated in a teleconference with Bruce Humphries, <br />,john Hardaway, Dave Kidd and Terry Manziac, and (3) reviewed John <br />Iie.rdawdy'e supplemental submittal concerning the Underdrain Layer <br />Sequence proposal. <br />!1) "Revisi.on to Underdrain Sequence to Improve Protection of <br />Vnderdrainrl: <br />Golder Associates originally specified a poorly-sorted, <br />relatively Open matrix, 12-inch minus material for uee.ae the <br />underdrain layer. This was then overlain by a select <br />structural material (3-inch minus) as a Filter layer, overlain <br />in sequence by a geotextile and VLDPE geomembrane aandwi.clL, <br />finally overlain by a protective select structural fill <br />material. Ae I understand CC&VG's revleion proposal they <br />desire to amend this sequence to move the geotextile down one <br />layer, placing it immediately over the 12-inch mirue <br />underdrain material and immediately below the first la}•er of <br />the 3-inch minus select EatxL)ctural fill. This places the 80- <br />mil VLDPE in direct conl'act with the select structural fill <br />material. <br />During the ].954 construction o~ Phase 1 of the heap leach pad <br />a problem was encountered with oversize in the 3-inch minus <br />select structure] fill material. CC~VG proposes to rectify <br />this problem by screening the select structural fill material <br />to ensure compliance with the 3-inch minus size limitation. <br />&'urther, earlier thin year CC&VG simplified the spec <br />pertaining to the underdrai.n material to state only that the <br />954 No.003 P.O1 <br />v <br />~-raTF of coLo~o <br />