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• EXECUTIVE SUMMARY <br />Colorado Westmoreland, Inc., with the assistance of Hydro- <br />Geo Consultants, conducted a hydrologic investigation in the area <br />of the proposed new mine portal. Opening of new mine entries is <br />planned from a cross-valley cut-and-fill bench in the central <br />portion of East Roatcap Creek. <br />The surface water hydrology investigation consisted of the <br />installation of a stream gaging station, flow monitoring, <br />hydrologic analysis for the construction site and conceptual <br />design of hydraulic structures. These structures will consist of <br />a corrugated steel pipe (CSP) culvert on East Roatcap Creek <br />underneath the fill, a sedimentation pond, a perimeter ditch, and <br />bench and haul road drainage ditches. The principal hydraulic <br />structure of the site, a 48-inch CSP culvert approximately 640 <br />feet long, was designed to pass flows resulting from a 10-year, <br />24-hour precipitation event with no head, from a 100-year event <br />with a head of 1 foot, and a 500-year peak flow with a head of 2 <br />feet at the inlet structure. <br />Diversion ditches were designed to minimize runoff into the <br />• disturbed areas. A sedimentation pond will be constructed at an <br />early stage of excavation to prevent surface water pollution <br />during construction as well as during the life of the portal <br />bench. <br />The design of the proposed portal bench, hydraulic <br />structures and sediment source control measures such as silt <br />traps and revegetation of the fill slopes are based on sound <br />engineering practice which will limit the potential for erosion <br />and sediment loads carried by runoff. Therefore, the impact of <br />the proposed portal bench on the local surface water drainage <br />patterns will be insignificant. <br />The ground water hydrology investigation consisted of the <br />construction of fourteen (14) piezometers and monitoring wells in <br />the area of the proposed portal bench. Five of the installed <br />wells were tested for permeability in the colluvial and coal <br />strata. Ground water in the study area occurs in the colluvial <br />sediments along East Roatcap Creek and in the coal and sandstone <br />strata of the bedrock. Both colluvium and coal have low <br />permeability and, therefore, are not considered significant water <br />bearing strata. Low permeability and poor water quality limits <br />the potential of ground water usage for irrigation, stock or <br />potable purposes. <br />. The proposed portal bench is located in an area where <br />the saturation of colluvial sediments is limited and, therefore, <br />the impact of the construction on the local ground water flow and <br />quality would not be significant. The "D" coal seam is saturated <br />i <br />