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E.rhibrt D <br />along the western shoreline of the seasvay, documented from abundant stratigraphic <br />evidence (in Colorado, Wyoming, Montana, and Utah) "buffered" the offshore regions of <br />the Western Interior (=central limestone-dominated belt) from river-born plumes of fine- <br />grained detritus. <br />3. The position of the proposed Rio Grande surface mine on the Trans-Continental Arch <br />basement structure (actively uplifred during the Late Cretaceous) provided additional <br />condensation of sediments during the deposition of the Fort Hays Member, and effective <br />bypass or removal of fine-grained siIiciclastic sediments (e.g. mudstone) due to <br />shallower, higher energy water depths -resulting in purer lime muds than found in <br />coeval beds in the surrounding regions of Huerfano, Fremont, and El Paso counties. <br />4. Existing overburden on the proposed Rio Grande surface mine lands ranges from 0.0 m <br />to 10.0 m [yielding a +0.8:1 overburden ratio] greatly reducing the need for extensive <br />blasting and removal ofnon-economic materials. <br />MINING <br />The extraction of the Ft. Hays Limestone unit will be conducted by an open pit operation. <br />The total thickness of the unit exceeds 30 ft with the actual thickness being variable due <br />to depositional character, quality, and erosion. Mining activities will be conducted with <br />two shifts per day, based on an 8-hour shift period with asix-day work week. Surface <br />• mining operations will be limited to 10 hours per day between 6:OOam and 9:OOpm, and <br />topsoil and overburden removal will be limited to 8 hours per day between 7:OOam and <br />7:OOpm. Mining operations will use standard methods and equipment commonly used in <br />limestone quarries. Mobil equipment will be used, such as (or the equivalent of) one <br />Caterpillar 623 scraper, one Caterpillar 988 front-end loader, and one 44-ton rock truck. <br />An 8-acre box cut (1200 ft long x 300 ft wide x an average 45 ft deep) will initiate the <br />operation and be connected to the adjacent plant by an excavated earth incline (51 ft wide <br />x 700 ft long). This initial opening will remain open and contain the primary crusher and <br />conveyance system, mostly below the normal surface elevation. Overburden and soil <br />from this initial cut will be stored in apre-determined area and revegetated for <br />stabilization. The highwalls at the northern edge and the sides of the earthen incline will <br />be permanently stabilized with slopes not exceeding 70 percent. Final highwalls will be <br />sloped 4H:1 V and stabilized to prevent erosion. Erosion and sedimentation controls, such <br />as impoundments, silt fencing, and diversion ditches, will be established to prevent soil <br />erosion and siltation of nearby streams. <br />Mining of the limestone and up to 6 ft of bottom sandstone will continue from this box <br />cut in a southerly direction as shown in Exhibit C-2. Production panels will be <br />established along strike, or about N49°W. The dimension of weekly panels must be at <br />least 24-ft wide by 600-ft long. There aze, regardless of the thickness of the limestone <br />layers, approximately 7,000 to 15,000 cubic yards of limestone to be removed in the <br />weekly panels. The limestone to be removed is covered by an unconsolidated layer from <br />0 to 40-ft deep. The yearly panel dimension will be approximately 450-ft wide by an <br />average of 1500-ft long by 30 ft of thickness (plus 1 fr to 6 ft of bottom sandstone) to <br />AppExhibitsA.T-APPQ I80)RevB/January 17,2002 D_'Z <br />