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The standard for production in Reclaimed Irrigated Pastureland was converted to a reference <br />area by TR -58, approved in 2009. The justification and data for this change can be seen in the <br />revision (TR -58) submittal. <br />4.5.1 Irrigated Pastureland Reference Area Soil Production Factors <br />Jim Boyd, the local NRCS representative, reviewed the capability of all soils in the reference <br />area and in the reclaimed area and assigned a relative factor to each of these soils. This letter <br />is included in Attachment 2.05.4(2)(e) -11. As can be seen from the letter, some soils are more <br />productive than others. The soil types are based on the USDA - NRCS Soil Survey of San <br />Miguel Area, which was compiled in the field from 1978 to 1984. The report was published in <br />1986. This survey can be obtained on the internet at <br />http:/ /offices. usda.gov/ scripts /ndISAP1.dII /oip_public /USA_map. <br />Assignment of a relative production factor to each soil type allows for the calculation of an <br />acreage weighted relative production factor for the entire reference area, and for an entire <br />irrigated pastureland bond release block(based on the soil types in the bond release block <br />prior to mining). <br />The table below shows how the weighted average production factor for the reference area is <br />calculated. The same procedure is used to calculate a weighted average production factor for <br />an irrigated pastureland bond release block. Narrative following the table explains how the <br />weighted average factors are used to adjust the reference area sample mean for bond release <br />comparisons. The adjustment procedure elevates the production success standard in <br />situations where premining soils were potentially more productive than reference area soils, <br />and lowers the standard in situations where premine soils were on average potentially less <br />productive than reference area soils. <br />(Revised: PR -06) 2.05.4(2)(e) - 24 <br />