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VII. Disposal of Excess Spoil -Rule 4.09 <br />The Permit is found to be in compliance with Rule 4.09. Information on excess spoil waste can <br />be found in Sections 2.05 and 4.09 of the Permit. <br />Colowyo Mine currently has three approved excess spoil fills: Streeter, West Pit, and Section 16. <br />Overburden material from the irritial box cut for beginning the East Pit was placed in the Streeter <br />valley fill: Now complete, Streeter Fill contains approximately 54 million cubic yazds of excess <br />spoil fill. Capacity of the West Pit fill is 16.5 million cubic yazds and capacity of the Section 16 <br />fill is 1.5 million cubic yards. <br />Specific information on the Streeter.Fill can be found in.Exhibit 12 of the Pemut and in Section <br />B, Item V of t11e original findings document. Specific information on the West Pit and Section 16 <br />fills is presented in Exhibit 19 of the Permit and in the files for revision PR-Ol. The fills meet the <br />regulatory definition of valley fills and therefore must, meet the regulatory requirements of Rules <br />4:09.1 and 4.09.2. <br />In this regazd, the Division approved the fills as disposal azeas for excess spoil [Rule 4.09.1(1)]. <br />The Division approved fill designs. These designs aze found in Exhibit 19 of the Pemut. <br />Constuction approved was by end dumping excess_spoil material in 50= to 100=foot horizontal <br />lifts. Prior to construction of the fills,. all topsoil was removed. fromthe areas as wetl as clay <br />subsoils beneath the: toe of the.. West Pit"fill.-Rohk underdrains are canstrueteil in natural drainage <br />bottoms from the toes to the heads of the fills. The fills aze completed with 3hav outslopes and <br />with 12-foot-wide terraces constructed at approximately 100-foot intervals. Topsoil replacement <br />and seeding completes the reclamation. A series o€ servey its and groundwater . <br />piezometer wells aze monitored 4uarterly, with results reported to the Division. <br />Based upon the geotechnical analyses prepared by CTLThompson Inc. (September 5, 1991 and <br />Apri127, 1992) and submitted by the Operator and based upon monitoring data from the Streeter <br />Fill at the Colawyo Mine; the Division found that the proposed WesE Pit and Seetio$16 excess <br />spoil fills were designed incompliance with the requirement of Rule 4:09.2. Specifically, the fills <br />were designed to attain static safety factors in excess of 1.5; material densities will be adequate to <br />prevent mass movement; end dumped lift placement and gravity segregation of spoil materials <br />will preclude the formation of deleterious vaidswith~ the.filLs;• an3 na corrtaminatiog of the rock <br />unclerdrains would occar [Rule 4.09.1(2)]. <br />The use ofvegetation and organic material as mulch or as' an amendment to topsoil to control <br />erosion, promote growth, or increase moisture retention was approved [Rule 4.09.1(4)]. The <br />locations of the excess spoil fill disposal azeas were approved [Rule 4.09.1(6)}. The use of <br />terraces in order to control erosion and enhance stability was approved [4.09.1(9)]. <br />VIII. Coal Mine Waste Banks -Rule 4.10 <br />Colowyo has no coal processing waste banks. <br />October 21, 2002 36 <br />