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• sampling was 43.9 percent (Table 1, Appendix 22-1). This value will become the success <br /> criteria value and will be compared to the vegetative cover values for the newly <br /> revegetated areas where Rule 4.15.10 applies. The two areas will be comparable when the <br /> vegetative cover values for the newly revegetated areas are at least 90 percent of the <br /> cover value determined from the 1988 cover sampling (43.9 percent) with 90 percent <br /> statistical confidence. <br /> Production. A technical standard as opposed to use of the reference area is proposed for <br /> the revegetation success standard for production. This standard is to be based on the <br /> potential productivity of the dominant soils present on the Nucla Mine permit area. <br /> Potential productivity values have been determined by the Soil Conservation Service (SCS) <br /> and are included in the soil survey of Western Montrose and San Miguel Counties presently <br /> being published. The more detailed Nucla Mine Soil Survey (Tab 9) identified the Shavano <br /> and Persayo soils as the most prevalent and information on potential productivity from the <br /> SCS survey was correlated with these soils. The potential productivity of the Shavano and <br /> Persayo series was taken from the most recent Soil Survey Interpretation Sheets (SCS Form <br /> 5) from the SCS soil survey noted above. The Shavano series occupies approximately 73 <br /> • percent of the affected area and has a potential production in favorable years of 500 <br /> lbs/acre. The Persayo series occupies the remaining 27 percent and has a potential <br /> production in normal years of 250 lbs/acre. <br /> The production standard for reclaimed areas is as follows. All dryland pasture areas and <br /> the rangeland areas receiving ten (10) inches of topsoil will have acceptable herbaceous <br /> production when the production value determined for the reclaimed areas is not less than <br /> 90 percent of 500 lbs/acre with 90 percent statistical confidence. The 500 lbs/acre value <br /> is to be used for these areas because Shavano soils will provide the majority of the <br /> replaced topsoil. The remaining reclaimed areas (excluding any yet to be reclaimed <br /> pre-taw areas or areas previously mined and reaffected by current operations as specified <br /> in 4.15.10) will be compared to the potential productivity for the Persayo soils at 250 <br /> lbs per acre. Herbaceous production for these areas will be considered acceptable when it <br /> is not less than 90 percent of 250 lbs per acre with 90 percent statistical confidence. <br /> As specified in 4.15.10, previously mined areas reaffected by current mining operations <br /> need not be evaluated for production. Exhibit 22-1 "Postmine Vegetation Map - Nucla Mine" <br /> illustrates the areas reclaimed as dryland pasture, as rangeland receiving ten (10) inches <br /> of topsoil, and as other reclaimed rangeland areas. <br /> 22-12 Revised 07/25/91 <br />