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8. Updated narrative regarding subsidence monitoring was provided as requested. <br />Item Resolved. <br />New Items <br />9. During the most recent mine site inspection, it was noted that recent storm flows <br />had resulted in minor erosion along segments of the permanent ephemeral channel <br />extending downstream from the sandstone ledge ("waterfall") immediately <br />upstream of the reclaimed explosives bunker site, downstream to the culverted <br />crossing of Haul Road 4, and then down to Coal Creek. Cobble channel lining <br />was undercut and bypassed in several locations, and in one location flow had <br />escaped the channel for a short distance (near the rock ledge corner just upstream <br />from the old concrete structure). This segment of channel has been affected by <br />mining and reclamation activity, and flows are elevated above historic levels due <br />to the fact that the east wing of the CRDA-2 upper diversion diverts flow from <br />several small watersheds into the channel upstream of the reclaimed explosives <br />bunker site. Apparently, a drainage design was never developed and incorporated <br />into the permit for this channel. <br />Please provide appropriate model based designs for this channel segment, <br />consistent with the approach that has been employed for previously <br />approved permanent ephemeral channels, that will meet the applicable <br />requirements of Rule 4.05.3 and 4.05.4. <br />10. The Divisions RN-OS reclamation cost estimate update was previously sent to you <br />under cover letter dated September 17, 2007. We reiterate our advisement <br />regazding the renewal cost estimate and associated bond increase. Unless <br />acceptable justification supporting a lower liability amount is provided, a <br />bond rider or replacement bond will need to be submitted to bring the total <br />bond amount to at least $2,233,045.00, before RN-5 can be approved. <br />Please respond to these items at your eazliest convenience, and within 30 days or receipt <br />of this letter of possible, to ensure that a renewal decision can be issued in a timely <br />manner. Please contact me if you have any questions. <br />Sincere <br />Daniel T. Mathews <br />Environmental Protection Specialist <br />C: Denver File <br />