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I have made a few cryptic comments regarding certain of the revision items, below. Can you pass this <br />memo along with a copy of our revision order letter and a copy of the application to the reviewers you <br />select? Once we have issued a decision on the revision, I will need one of the copies returned to me, and <br />the other to Johanna. <br />Thanks for your help. <br />1. ok <br />2. ok <br />3. p.31i ok. Check deleted tables against tables 12-1 and 12-2. <br />4. Updates look ok, but need to review more thoroughly. <br />5. Looks ok, but need to review more thoroughly. <br />6. CRDA-1 crowned design looks ok; pretty close to existing centigumtion. <br />CRDA-2 design has been modified to provide for upland diversion ditch immediately above the <br />pile; difl'ering from the current ditch located higher on the slope by having a more uniformly steep <br />gredient (2.5%). Operator states that the channel will be below the level of the refuse, <br />approximately 10 feet below at the outlets, and that this design will minimize the risk of runoff <br />overtopping the channel and eroding the pile. <br />However, in central portions of the ditch, the channel would apparently be only 2 feet deep, and 10 <br />or I 1 feet wide at the [op. Based on what we saw occur due to cloudburst and resultant debris <br />flow at Fruita Mine, I would still be concerned that similar flooding would fill in the upland ditch <br />at locations where the steep ephemeral drainages are intercepted with mud and boulders up to the <br />size of small cars, and (lows would then proceed across the 2% slope of the fill, eroding gullies on <br />the outslope. Opemtor did not propose a modified crowned or mounded top of pile topography to <br />provide for a more substantial topographic barrier to minimize the potential Cor large scale erosion <br />of the refuse pile outslopes in the event of flooding, debris deposition, and ditch Cailure. <br />Not clear to me whether entire length of ditch would be in native ground, or whether portions of <br />the ditch at either end would be located wholly or partially on refuse. If so, what are the <br />implications? <br />Operator indicates that material from ditch excavation would be used for non toxic refuse cover. <br />Documentation of chemical/physical suitability would need to be provided. Soils exposed at the <br />east end of the pile appear to be sodium affected heavy clays, not suitable for use as cover soil. <br />7. ok. <br />8. ok for now. Probably need to review after midterm cost estimate completed. <br />9. Comments anyone? <br />10. BLM is still pondering the culvert question. <br />11. Ok. <br />