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Acceptable production will be achieved when the production value determined for the appropriate <br />irrigated pastureland reclaimed areas is not less than 90 percent of the 1.50 tons per acre with 90 <br />percent statistical confidence. <br />The success standard for cover is based on the level of premining ground cover (live vegetation) <br />determined from the 1987 and 1999 baseline studies conducted within the New Horizon 2 study <br />area (see Section 2.04.10). The average live vegetation cover determined from the 1987 study was <br />71.8 percent. In 1999 the average live vegetation cover was 76.8 percent. These values represent <br />long term established perennial vegetation, reflecting a reasonably constant value because of <br />historic irrigation and management. The difference in vegetative cover is attributable to the <br />difference in precipitation levels. As referred to earlier, 1999 was a very wet year during the 1999 <br />growing season and the winterof 1998-1999 was mild. NRCS climate data forthe San Miguel basin <br />indicates that precipitation is currently 177% of normal. NOAA data, current through April of 1999 <br />(Sec. 2.04.10, Tables 2.04.10-1 and 10-2) indicates a dry mild winter with a large increase in <br />precipitation for April. While the data is not available for May through August this trend of higher <br />than normal was verified by local residents in the Nucla area. Fluctuations in vegetative cover are <br />relatively small because irrigation has eliminated much the precipitation variation from yearly <br />fluctuations normally encountered in the semi-arid climate in the Nucla area. Some fluctuation in <br />live canopy cover is expected as precipitation effects areas inadequately covered by flood irrigation <br />and the resultant effect would be to suppress or promote vegetative cover uniformly over a pasture. <br />Temperature fluctuations have the same relative effect. During colder more severe climate years <br />vegetative cover would be suppressed or promoted with the respective severity or mildness of the <br />climate for a particular year. At the high levels of production achievable under properly managed <br />irrigated pasture, and specified in the production standard, the vegetation and ground coverwill be <br />more than adequate to meet the requirements of 4.15.1(2)(b). Since 1999 was an abnormal year <br />climatologically, the success standard for cover will be 71.8 percent ground cover for both the <br />orginal permit and the proposed permit expansion area. The ground coverforthe reclaimed areas <br />will be considered acceptable when the live vegetation cover, as specified above, are not less than <br />90 percent of these values with 90 percent statistical confidence. <br />Drvland Pasture Tvoe. Areas reclaimed to the dryland pasture type occupy locations where the <br />Pinon-Progresso loams complex (1987), soil map units 98C, 986, and 98H (1999), and sagebrush <br />vegetation types occurred prior to mining (see Section 2.04.9 and 2.04.10). Some of these <br />(Revised 7/2005) 2.05.4(2)(e)-21 <br /> <br />