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3. Species diversity -Reclaimed areas will achieve a standard of three grasses. one <br />forb and one shrub with relative cover values greater than three percent. The <br />combined relative importance will not exceed 8~ percent and no one species will <br />contribute greater than 40 percent relative importance. <br />Seasonal variety requirements will be waived since the proposed species will <br />support the proposed post-mining land use. <br />Woody plant density -The live stem success standard will be 250 stems per acre <br />on dry sites and 750 stems per acre on wet sites with at least one shrub having a <br />minimum relative cover value of three percent. <br />New Horizon Mine 2: <br />Cover -The success standazd for irrigated pasture is 71.8% live vegetation cover, <br />based on a 1987 vegetation baseline study conducted within the original New <br />Horizon Mine 2 area. Cover sampling conducted in 1999 within representative <br />imgated pasture azeas in the PR-OS revision azea indicated only slightly higher <br />cover levels (mean cover 76.8%), despite growing season precipitation which <br />was 177% of normal during 1999, prior to sampling. The original cover standazd <br />will be sufficient to control erosion, and will remain in effect for the Mine 2 azea, <br />including the PR-OS revision azea. Successful cover establishment will be <br />demonstrated when live vegetation cover is not less than 90% of 71.8%, with 90 <br />percent statistical confidence. <br />The success standazd for dryland pasture is based on a cover comparison with a <br />new dryland pasture reference azea established in 1999, which is described in <br />Section 2.04.9, with location shown in Attachment 2.05.4(2)(e)-2. The new <br />reference azea more closely represents the proposed postmine vegetation than the <br />sagebrush reference area previously utilized. The new reference azea supports <br />established introduced dryland pasture grasses on BLM managed land in the <br />permit area vicinity. Successful cover establishment will be demonstrated when <br />live vegetation cover on the reclaimed area is not less than 90% of the reference <br />azea cover, with 90% statistical confidence. <br />A cover success standazd for irrigated hayland is not applicable because <br />revegetation success is only dependent on production. <br />2. Production -The production success standard for irrigated hayland in the New <br />Horizon 2 area is a technical standazd based on a combination of permit azea <br />landowner estimates, NRCS evaluation, and landowner production records for <br />1987 and 1999, for alfalfa hayland first cutting production. Yield estimates and <br />records for the permit area landowners, and a June, 1998 letter from the NRCS <br />supportive of a production standard of 1.84 tons/acre/year, for 1~` cutting irrigated <br />27 <br />