2024-09-16_GENERAL DOCUMENTS - C1981028

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Page 7 Confidence Interval test. Herbaceous Production. Reclaimed areas will be considered successfully reclaimed if the total herbaceous production on the reclaimed area(s) is not less than 90 percent of the total herbaceous production value from the equation: y = 0.4666x2.1405 (where x is the cumulative September – July precipitation at the mine) with 90 percent statistical confidence using a one tailed Student’s t or Confidence Interval test. Species Composition. Reclaimed areas will be considered successfully reclaimed if the species composition of any reclaimed area is such that there are at least four perennial grass species. No one component of the above species should compromise greater than 40% relative cover nor less than 3% relative cover. Any perennial grass species (native or introduced) may be used in the calculation of species composition except for those species defined as noxious by the Colorado Department of Agriculture. Post-Mining Land Use The approved post-mining land use is the same as the pre-mine land use of rangeland (as discussed in Section 2.05.5 of the PAP) for the SL-12 area. Protection of the Hydrologic Balance Consideration of a Phase III bond release application must assess compliance with the Probable Hydrologic Consequences section of the PAP (Section 2.05.6), namely whether offsite impacts and material damage have been prevented. III. OBSERVATIONS AND FINDINGS CEC sampled vegetation in August 2021 and 2022. These samples showed that each sampled area passed the Total Vegetation Cover, Herbaceous Production, and Species Composition standards for each year. The data showed a high frequency of warm season grasses, which is consistent with the time of year that the site was sampled. Rob Zuber, Brock Bowles, and Joel Renfro with the Division inspected the site on June 25, 2024. Weather conditions were dry prior to and during the inspection. Very little new growth was observed during this inspection and many of the previous year’s grasses were dormant. Some of the species observed include sand bluestem, prairie sandreed, sand dropseed, and redroot amaranth. Other desirable species such as common sunflower, sand sagebrush, and prairie ground cherry were also present. The only State-listed noxious weed species observed was cheatgrass. Since warm season grasses were shown to be more dominant in the vegetation data of the application, the Division conducted a follow-up inspection on August 6, 2024. Conditions on site remained hot and dry, and the sandy soil appeared dry as well. The Division observed new growth of warm season grasses during this second inspection, especially in Area 31. The observed warm-season grasses included sand bluestem, sand dropseed, and prairie sandreed. The new growth grasses found during this inspection