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<br />The application should be revised to include consideration of regrading to <br />achieve lesser channel gradients. Where restoration of pre-mine gradients <br />would alleviate the need for structural controls, the stabilization plan <br />should include such regrading as necessary to achieve those gradients. <br />The remaining comments in this section are more narrowly focused technical <br />concerns relating to the channel stabilization plan as proposed. <br />Two areas previously identified by the WET report as having characteristics <br />that lead to channel instability have not been addressed. These areas are <br />9/10-1 and 9/10-1 (51E). Another channel segment not addressed is one <br />identified by the Division in a letter of December 12, 1986 to CYCC. This <br />segment is designated as 9/10-3. These three segments should be addressed <br />by the operator as to how stabilization will be effected, or if no <br />stabilization is proposed, justification needs to be presented. <br />The design for channel stabilization presented is, as stated in the report, <br />"based on the assumption that only sound, durable rock will be utilized in <br />construction of riprap channel linings." As channel stability can only be <br />achieved with sound, durable rock the following commitment will need to be <br />included in the application or it will be stipulated if 'the revision is <br />approved. <br />ROCK TO BE USED FOR RIPRAP IN CHANNELS WILL MEET THE REQUIREMENTS FOR <br />DURABLE ROCK AS DETERMINED BY APPROPRIATE FIELD AND LABORATORY TESTING. <br />APPROVAL OF THE ROCK TO BE UTILIZED MUST BE GIVEN BY THE DIVISION PRIOR TO <br />PLACEMENT. <br />Appropriate testing for rock durability is detailed in Surface Mining Water <br />diversional Design Manual, Section 8, by the OSM. <br />As with any engineered structure, certification that the as-built channel <br />meets the design criteria is required. The following commitment will need <br />to be included in the application or will be stipulated if the revision is <br />approved. <br />THE COMPLETED CHANNEL SEGMENTS WILL BE CERTIFIED BY A PROFESSIONAL ENGINEER, <br />EXPERIENCED IN CHANNEL DESIGN AND CONSTRUCTION. THE CERTIFICATION WILL <br />