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Dan Hernandez - 4 - July 7, 1989 <br />CONCLUSION <br />A comparison of the soil loss conditions evaluated in this assessment of the <br />Snyder Quarry amendment area indicates the lowest rate is produced with a low <br />canopy cover of mixed trees and shrubs. This condition is that proposed by <br />MLRD. Increasing the tree cover but removing the shrub component reduces the <br />protection provided by the low cover and increases soil loss. This is noted <br />in the condition described as "forested". With a reduction in canopy cover <br />and no shrub component, a slightly higher soil loss is produced. This <br />condition is evident in that proposed as Condition 3. <br />The significant reduction in soil loss under all three reclaimed conditions <br />over the existing condition is attributable largely to the reduction in <br />slope. This is achieved by Creation of the benches during mining. Although <br />highwalls are also produced, these will contribute little sediment to the <br />drainageway. Sediment originating from the highwalls will be deposited at <br />their base during the first few years after mining. Soil loss after mining is <br />less than one half the estimated natural erosion. <br />It must be recognized that these soil loss estimates are generalized in nature <br />and do not reflect actual values over small areas. If locations exist where <br />vegetation is Clumped together, either grass or shrubs, lesser rates of <br />erosion would be likely. Similarly, bare areas likely to occur in the first <br />few years of vegetation establishment will produce relatively higher rates of <br />erosion. <br />The relative differences between the three (3) conditions considered in this <br />assessment are small. All three produce a little over 2 tons per acre per <br />year of soli loss. An overstory of trees or shrubs will produce reduced rates <br />over grass cover alone. Inclusion of a low shrub component in addition to <br />trees tends to produce a lesser overa ll soil loss. The only measure to offer <br />significant reductions, although not specifically evaluated in this assessment <br />would be to increase the percentage of grass cover beyond the natural 60~ <br />cover noted at the site. <br />JTD(yjb <br />cc: Bruce Humphries <br />Steve Renner <br />7841E <br />