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The Division finds the subsidence control plan, as presented by Powderhorn Coal Company within the <br />permit application document, to be in compliance with the subsidence-related regulations of Rules <br />2.05.6(6) and 4.20. <br />On October 31, 2007 the Division issued a proposed decision to approve a Release from Liability of <br />Areas Overlying Underground Workings (SL-3). Upon final approval of SL-3, reclamation liability <br />would be released on approximately 7,294 acres of the permit area, which currently (November 9, <br />2007) encompasses 10,310 acres. Over 2000 acres of land underlain by Permit C-81-041 underground <br />workings are included in the area of proposed liability release; remaining lands proposed for release <br />were neither undermined nor affected by surface disturbances or facilities associated with Permit C- <br />81-041. Please refer to the Division's October 31, 2007 Proposed Decision and Findings document <br />for SL-3, for further details. <br />XIH. Operations on Alluvial Valley Floors <br />The permittee's alluvial valley floor investigations in Section 2.06.8 of Tab 21, Volume 6, of the <br />application have been reviewed for compliance. <br />There are three separate areas where alluvial valley floors must be assessed: <br />1. The surface facilities area and adjacent areas at the Roadside North and South Portals, and <br />Unit Train Loadout (UTL); <br />2. The Cottonwood/Rapid Creek drainages and adjacent areas which will be undermined by <br />the Roadside mine; and <br />3. The Colorado River Alluvial Valley Floor. <br />Drainages in the North Portal mining area are characterized by steep sided canyons with deeply <br />incised channels, limited areas of alluvial deposition, and no flood irrigated or subirrigated agriculture. <br />Headwaters for these drainages are at relatively low elevations in the Book Cliffs, and the streams <br />exhibit intermittent or ephemeral flow regimes. Insufficient surface water availability and saline soils <br />eliminate Coal Creek, Jerry Creek and their tributaries from alluvial valley floor consideration. <br />Drainages in the bookcliffs with characteristics similar to those in the permit area are not typically <br />developed for irrigated agriculture (OSM, June, 1985 "Reconnaissance Maps to Assist in Identifying <br />Alluvial Valley Floors, West-Central Colorado"). <br />Potential AVF areas within and adjacent to the permit area are addressed below. See Tab 21 of the <br />application for further information. <br />Facilities Area <br />The permittee identified approximately 500 acres of land within the reconnaissance study area that <br />meet the geomorphic criteria for alluvial valley floors. This land is located adjacent to the Colorado <br />River. The permittee noted, on Exhibit 33 of the application, that a portion of this land is subirrigated <br />and a portion was historically flood irrigated. <br />Permit Revision No. 4 51 February 3, 2009