2018-02-09_GENERAL DOCUMENTS - C1994082

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Permit Number C-1994-082 Page 10 of 17 SPL uses an acreage-weighted value for vegetative cover and herbaceous productivity success determination based upon sampling of four main vegetation type reference areas. The four reference areas are the Aspen, Mountain Brush, Steep Mountain Brush, and Sagebrush reference areas. Based upon the pre-mining vegetation community distribution, the aspen community composed approximately 24.4% of the area, the mountain brush community composed approximately 48.9% of the mining area, the sagebrush community contributed approximately 24.0% of the area, and the steep mountain brush contributed 2.7% of the area. Cover Reclamation success for vegetative cover requires a summation of the weighted-average vegetative cover (based on the relative extent of primary pre-mine vegetation type contributions of total acreage) for allowable all-hit herbaceous cover derived from sampling in the approved reference area. Allowable all-hit herbaceous cover is determined from cover sampling in the Phase III reclaimed lands and the native reference area, with subtractions made for woody plants, noxious weeds, and cover of annual/biennial weeds in excess of 10% relative cover. The Phase III bond release area sample value will be no less than 90% of the cover success standard at 90% statistical confidence. SPL collects “all hit” vegetation data, but uses “first hit” data for reclamation success determination. All hit vegetation data did achieve sample adequacy. However, conversion to “first hit” cover resulted in the “first hit” vegetation data not meeting the adequacy calculations. The sample adequacy based on allowable all-hit herbaceous cover was achieved for vegetative cover for the 2012 and 2014 sampling of the SL-6 BRB-1 and three of the four reference areas, the exception being the mountain brush reference area. The mountain brush sample adequacy, based on all-hit allowable herbaceous cover, was not achieved for the mountain brush type in the reference area in both 2012 and 2014. The mountain brush community accounts for 48.9% of the reclamation cover standard. SPL utilized an alternative that used the upper 90% probability value of the mean. This alternative established a reliable estimate population variance. Having taken 21 samples in 2012 and 16 samples in 2014, the maximum possible values of the mean (with 90% confidence) were taken to represent the allowable herbaceous cover of the mountain brush type within the reference area. Based on the Division’s review, the Division accepts this sampling methodology for the following two reasons: 1) the upper limit of the possible values of the true mean was determined and used for the standard and 2) the reclaimed area cover value was 14.9% points greater than the standard in 2012 and 15% points greater in 2014. Allowable vegetative cover measured on BRB-1 in 2012 was 47.8 percent. The calculation of 90 percent of the 2012 cover standard was 32.9 percent. Vegetative cover on the reclaimed bond release block was successful for 2012. Allowable vegetative cover measured on BRB-1 in 2014 was 60.6 percent. The calculation of 90 percent of the 2014 cover standard was 48.8 percent. Vegetative cover on the reclaimed bond release block was successful for 2014.