2013-05-01_REVISION - M2002004 - Laserfiche WebLink

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fine- grained siliciclastic sediments (e.g. mudstone) due to shallower, higher energy water depths — resulting in purer lime muds than found in correlative strata in the surrounding regions of Huerfano, Fremont, and El Paso counties. 4. Existing overburden on the proposed Rio Grande surface mine lands ranges from 0.0 m to 10.0 m [yielding a +0.8:1 overburden ratio] greatly reducing the need for extensive blasting and removal of non - economic materials. "Overburden" includes the shale and unconsolidated materials above the mineable Fort Hays unit. Unconsolidated materials consists of an A soil horizon, an A -C subsoil horizon, and other materials above the shale. MINING Erosion and sedimentation control structures will be placed in watersheds prior to other mining and reclamation activities. Topsoil and subsoil salvage operations will commence after water control and treatment structures have been completed. The extraction of the Fort Hays Limestone will be conducted by an open pit operation. The maximum thickness of the unit exceeds 35 feet (refer to Exhibit C -4) with the actual thickness being variable due to depositional character, quality, and erosion. Mining activities will be conducted with two shifts per day based on an 8 -hour shift period with a six -day workweek. Surface mining operations will be limited to 10 hours per day between 6:00am and 9:00pm, and topsoil, subsoil, other unconsolidated materials, and shale removal will be limited to 8 hours per day between 7:00am and 7:00pm. Mining operations will use standard methods and equipment commonly used in limestone quarries. Mobile equipment will be used, such as (or the equivalent of) Caterpillar 623 scrapers, Caterpillar 988 front -end loaders, and 44 -ton rock trucks. Limestone required for the cement plant will be reduced in size by a mobile in -pit crusher and subsequently transported out of the pit and to the plant by covered conveyor. The crusher and conveyor will be extended as the mining face advances in each panel. The initial mining work described in the initial permit application and shown in Exhibit D -1 is complete. The areas Y1 through Y3 are mined and mining has moved into Y4. The southeast boundary line of panel 1 is slightly realigned. Mining will be conducted in a series of panels, oriented up the dip of the limestone. Each panel will be approximately 1,400 -feet wide, with its base approximately parallel to the strike of the limestone. The upslope length varies. Panel One, for the first five years of operation, will extend approximately 2,600 feet upslope. Panel Two, oriented parallel to Panel One, will be operated for the following ten years. Panel Three, oriented parallel to Panel Two, will be mined following the completion of Panel Two. This pattern will be repeated over the life of the mine. Stationary and /or mobile conveyors will extend to the southeast as each panel is opened. Within each panel, the conveyor will be extended to the east or west in the direction of the mining cut face. This extension will be through the mid - section of the panel. The m crusher and mobile conveyors may be moved several times a year to stay with the mining face. Because of the gradually decreasing thickness of the limestone in an up- gradient direction, the area disturbed for each year of mining will vary, gradually increasing upslope. In addition, the area mined each year will depend on the demand for Portland cement and any slight variations in the limestone. Figure D- 1 illustrates the area disturbed for each of the first 8 years of mining. Material above the limestone from the initial cut has been stored in an area south and south -east of mining year blocks 4 and 5, as noted on Exhibit D -1, and has been temporarily revegetated for stabilization. (Pre - stripped materials from the Year 6 operating block (not illustrated) will be stored above the Year 15 Technical Rev No 4 April 26, 2013 D -2