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RULE 4 PERFORMANCE STANDARDS <br /> <br />South Taylor – Rule 4, Page 8 Revision Date: 7/21/25 <br /> Revision No.: MR-267 <br /> <br /> <br />completed until such a time as the fills themselves develop and are constructed to meet PMT compliance. <br />This activity will be logically sequential in that they will be developed from the bottom up. <br />Colowyo will follow the Shannon & Wilson recommendation for excavation as described in Exhibit 21. <br />A controlled underdrain in accordance with the Shannon & Wilson recommendations will be placed in the <br />natural drainage bottom from the head to the top of the fill, The harder, available sandstones obtained from <br />the mining operation will be selectively handled and placed in at least a 24 foot wide by 8 foot high <br />configuration to serve as the underdrain before covered by spoil material. The natural spoil sorting which will <br />occur by utilizing the thicker lifts recommended by Shannon & Wilson will be sufficient to protect the drain <br />from clogging above the geotextile fabric. <br />Lift thicknesses up to 100 feet thick is acceptable and will be utilized to construct the fill. This method of <br />spoil placement also enhances the construction of a free draining layer of spoil material at the base of the fill. <br />Experience at Colowyo provides evidence that the natural sorting process which occurs while dumping in <br />higher lifts is sufficient to create this drain. Inspection and documentation of this natural sorting is <br />recommended and will be conducted by Colowyo. See the Inspection Plan section for additional details. <br />INSPECTION PLAN <br />During construction of the East Taylor and West Taylor Fills, Colowyo will provide the following <br />information in certified reports as required by Rule 4.09.1(11). <br /> <br />1. Inspections will be conducted at least quarterly during the construction period and during the <br />following specific construction periods. <br /> <br /> a. removal of topsoil and organic material <br /> b. placement of underdrain system <br /> c, installation of surface drain system <br /> d. placement of fill material to insure that the largest rocks are reaching the bottom of the dump <br />face and that the formation of voids that adversely affect mass stability are prevented and <br /> e. revegetation <br /> <br />The purpose of the inspections is two fold. First, these inspections will document and certify that the <br />construction plan is being followed. Secondly, during the above phases of the construction, a key emphasis of <br />all inspections will be to implement routine contingencies as situations warrant. For example, perhaps a <br />section of underdrain should be reworked, or the spoil dump raised to provide optimum gravity spoil sorting. <br />Inspections and implementation of contingencies during these critical phases of fill construction will be a <br />routine but very important component of fill inspections. <br /> <br />2. Each certified inspection report will be provided to the Division within two weeks after each required <br />inspection. Each report will certify that the fill has been constructed as specified in the minimum <br />design approved by the Division. The reports will include a description of any appearances of <br />instability, structural weakness and other hazardous conditions observed during the inspection. <br /> <br />3. Certified reports addressing the underdrain system will include color photographs taken during and <br />after construction, but before the underdrain is covered with spoil. <br />