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• equipment used to move the material in place, several techniques will be used to replace <br /> spoil materiel at the Yoast Mine. Some spoil placement will be accomplished usi ng cast <br /> blasting. Some replacement will be conducted using scrapers end draglines. Final <br /> contouring of the spoil surface will be conducted using dozers and scrapers. The overall <br /> hydraulic conductivity of the spoil should be higher than t he conductivity of the <br /> surrounding undisturbed materiel comprising the shallow aquifers, regardless of the method <br /> of replacement. <br />The hydraulic character of the spoil will also be affected by the texture of the material <br />after it is replaced. Although the spoil will exhibit increased porosity, the degree of <br />particle sorting is decreased and the material will have amore homogeneous texture. <br />Differences in horizontal and vertical permeability that were present in the compacted and <br />stratified undisturbed material will decrease as a result of the less sorted, more <br />homogeneous texture present within the replaced spoil material. Vertical permeability <br />within the spoil will depend on the degree of interconnected porosity rather than <br />fractures present in the compacted layers of the overburden. The poorer sorting of <br />particle sizes in the spoil should not impede the vertical flow of water any more than <br />impedance produced by compacted layers and variable degrees of vertical fracturing within <br />undisturbed material. <br />Analysis of premi ning soils at Yoast indicates that Che soils generally display sloe to <br />moderate rates of infiltration (see Tab 9, Soils). Replaced topsoil is projected to <br />display a more even mixture of moderate infiltration rates. Sometimes infiltration rates <br />in topsoiled spoils are less than the infiltration rates in undisturbed soils. Three <br />years of monitoring seem to suggest that infiltration rates in replaced spoil at the <br />Seneca 11 Mine are unchanged or slightly increased since recharge has occurred at a <br />greater rate than normal for the area. Though [he topsoil is compacted somewhat during <br />placement, deep ri ppin9 and disking operations will enhance infiltration rates and prepare <br />the soil for seeding. Regrowth of vegetation will induce retention of soil moisture and <br />enhance infiltration chile preventing surface runoff. <br />In conclusion, the mining and reclamation activities planned for Yoast will not diminish <br />the horizontal and vertical permeabi lilies of adjacent, undistrubed geologic units <br />(overburden and coal). Ground water flow into and out of These adjacent units will be <br />controlled by the undisturbed permea bifities and secondary porosities of the Compacted <br />15 Revised 03/01/95 <br />