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In order to achieve the above goals, which are a reasonable and practical basis for judging successful <br /> reclamation, Trapper Mine proposes an effective cover standard designed such that soil loss due to rill <br /> and sheet erosion will not exceed four tons per acre per year., This is an acceptable soil loss erosion rate <br /> below what has occurred on premine areas and is the basis for our proposed technical standard for <br /> cover. The majority of the topsoils being used for reclamation at Trapper Mine have a T value <br /> (maximum soil loss permissible under Soil Conservation Service Criteria on an annual basis) of five tons <br /> per acre per year. Additionally, the proposed limit is less than the weighted average T value of 4.33 <br /> Tons/ANr, Table 4.4-5. The proposed limit is conservative and site specific to Trapper Mine. <br /> Trapper won't propose a historic standard for herbaceous cover. The data is extremely variable and the <br /> resulting lower confidence limits are too low to provide an acceptable level for erosion control, the <br /> primary purpose for cover, Table 4.4-4. <br /> The proposed effective standards for range sites A, B, and C were calculated using the LISLE. The <br /> calculation and resulting numeric cover standards are shown on Table 4.4-1. <br /> Effective cover to meet the standards will utilize a combination of herbaceous cover and litter cover. A <br /> historic average percent litter factor was calculated from 1979 and 1985 cover data, Table 4.4-2. To <br /> obtain the level of herbaceous cover required by the standard, the historic average percent litter factor is <br /> multiplied times the needed effective cover and the result is subtracted from total effective cover <br /> required by the standard. For example, let us say 50% effective cover is necessary to result in not <br /> exceeding 4 tons/A/yr, the calculation would then proceed as follows: <br /> (50% effective cover)(.372 avg % litter factor) Table 4.4-2 = 18.6% litter <br /> (50% effective cover- 18.6% litter) = 31.4% herbaceous cover. <br /> Thus, in this case the effective cover reclamation standard would be no less than 31% actual herbaceous <br /> cover and no more than 19% actual litter cover. Actual litter cover may exceed 19% but only 19% actual <br /> litter cover could be used to meet the standard. <br /> Based upon an analysis of potential soil erosion, Table 4.4-1, the proposed effective cover standards will <br /> not result in excessive postmine soil erosion. <br /> 4-102 <br /> Revision: i - I <br /> Approved: <br />