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17 East Pit topsoil test holes was 17.1 inches. The average topsoil replacement depth for the 12 <br />West Pit topsoil test holes was 16.9 inches. The average topsoil replacement depth for the 5 <br />Section 16 Pit topsoil test holes was 17.9 inches. While the East Pit and West Pit topsoil <br />replacement depth averages were approximately one inch below the required depth of 18 inches, <br />the Division finds that this is still acceptable. Following topsoil replacement there is a certain <br />amount of compaction that takes place and a small amount of soil loss due to wind and water <br />erosion is expected. The topsoil replacement depths in the East Pit and West Pit were 95% and <br />94% of the required replacement depth, respectively. The Division finds that the topsoil in the <br />Phase II Bond Release areas of the East Pit, West Pit and Section 16 Pit has been replaced in <br />accordance with the approved plan in the permit. <br />Revegetation <br />The 28 reclamation blocks, totaling 432.7 acres, included in the Partial Phase II Bond Release <br />SL-04 are EP028, EP029, EP030, EP031, EP032, EP033, EP034, EP035, EP036, EP037, EP038, <br />EP039, EP040, EP041, EP042, EP043, EP044, WP003, WP004, WP005, WP006, WP007, <br />WP008, WP009, WPO10, WPO11, S 16010, and S 16014. Seventeen of the reclamation blocks <br />are located at the East Pit and account for 365.89 acres. Nine of the reclamation blocks are <br />located at the West Pit (the West Pit Fill) and account for 49.44 acres. Two of the reclamation <br />blocks are located in the Section 16 Pit and account for 17.37 acres. The locations of the <br />reclamation blocks are shown in Exhibit 2 - Phase lI Bond Release Map in the SL-04 <br />application. These reclamation blocks were seeded between 1996 and 2003. The seed mix used <br />on the reclamation blocks is included in the SL-04 application in Tables 2.05-7 and 2.05-8. The <br />post-mining land use for the Phase II Bond Release area is rangeland, as defined by Rule <br />1.04(71)(c). <br />The Colowyo Mine uses two reference areas for the comparison of success of their reclamation <br />blocks. The reference areas are the sagebrush reference area (established in 1981) and the <br />mountain shrub reference area (established in 1980, which is further separated into a mesic <br />aspect and a xeric aspect). Success standards are based on a weighted average of the premining <br />vegetation communities in each reclamation block (as shown on Maps 3 and 4). <br />Permit Page 4.15-16 states that the "...herbaceous cover of the revegetated area will be <br />considered adequate for final bond release if it is not less than 90% of the herbaceous cover as <br />determined from the reference areas with a 90% statistical confidence utilizing a standard <br />students statistical t-test comparison of the means." <br />The reclamation blocks contained in SL-04 were sampled in 2006, 2007, 2008 and 2009 in <br />accordance with the vegetation monitoring plan, detailed on Permit Page 4.15-1. Sample <br />adequacy was determined using the Cochran formula. Both the sampling plan and the sample <br />adequacy determination are acceptable to the Division. <br />Colowyo sampled all of the reclamation blocks that were included in the Partial Phase II Bond <br />Release SL-04 in both the 2006 and 2007 sampling years. Data collected at all of the transects <br />Proposed Decision and Findings of Compliance 2 May 2011 <br />Partial Phase I/II Bond Release SL-04 Page 9