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Peabody Sage Creek Mine — Sump Design Report <br />1.0 Introduction <br />This design report presents the designs for the Upper and Lower Sumps associated with the <br />operational phase of the Peabody Sage Creek Mine. The sumps are designed to control <br />runoff and sediment loads from the South Surface Facilities Area. The locations of the two <br />(2) sumps are shown on Map 2.05.3 M4, Drainage and Sediment Control Plan. <br />Two (2) sumps were designed to allow the collection of coal fines and sediment during the <br />different phases of the mining operations. The two sumps will serve not only as sediment <br />traps but also as pre- treatment structures to control/minimize the delivery of coal fines <br />downstream to Pond 002. Initially, the Lower Sump will serve as the primary collection <br />point for coal fines. Once the southern-most coal handling pad becomes active, then the <br />Upper Sump will serve as a collection point for coal fines. Both ponds are designed and will <br />be constructed using similar methods. <br />2.0 Embankment and Excavation <br />The embankments for both sumps will be homogeneous earthen filled structures. Borrow <br />source material used to construct the embankments, will come from the underground mine <br />portal area or, in the case of the Upper Sump, from within the area of the impoundment. <br />Lower Sumn: This structure will be constructed first, to control runoff and sediment from <br />the initial disturbance associated with construction. Ultimately, the structure will serve not <br />only as a sediment trap but also as a pre- treatment structure to control/minimize the delivery <br />of coal fines downstream to Pond 002. <br />The embankment height, as measured from the ground surface of native material to the <br />invert of the emergency spillway will be approximately 10 feet. The top of the width of the <br />embankment crest will be approximately 15 feet; embankment outslope and inslope will be <br />2H:1 V and 3H:1 V, respectively. A compacted keyway, 5 feet deep by 10 feet wide, will be <br />constructed into natural material below the embankment. See Map 2.05.3 -E2.E, Lower <br />Sump Design, for additional details and configuration. <br />Upper Sump: The embankment height, as measured from the ground surface of native <br />material to the invert of the emergency spillway will be approximately 10 feet. The top of <br />the width of the embankment crest will be approximately 15 feet; embankment outslope and <br />inslope will be 2H:1 V and 3HA V, respectively. A compacted keyway, 5 feet deep by 10 <br />feet wide, will be constructed into natural material below the embankment. See Map <br />2.05.3 -E2.D, Upper Sump Design, for additional details and configuration. <br />3.0 Design Analysis <br />This sump system was designed to meet or exceed the applicable design and performance <br />requirements of the Regulations of the Colorado Mined Land Reclamation Board for Coal <br />Mining. Specifically, the designs adhered to the following requirements. <br />• Provide for an adequate sediment storage volume and periodic sediment removal. <br />TRO1 -10 2.05.3- E2.E -1 2/11 <br />