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sn't critical to the CRDA-1 monitoring, which DMG will verify with its hydrologist. <br />II. Cameo Refuse Disaosal Area 2 <br />CRDA-2 is located on the west/northwest side of Interstate 70 across the highway from <br />the main mine facilities area, and on the north side of the canyon access road. Its <br />MSHA identification number is 1211-CO-09-03012-02. Construction began in 1985. <br />The total disturbed area associated with the pile, access road, ditches and pond is <br />about 32 acres. In accordance with section 4.09.1(13), CRDA-2 doesn't have an <br />underdrain because it isn't located in a drainage or in an area with springs or seeps. <br />The pile currently is in use. <br />Approved design parameters for CRDA-1 incude: 2.5h:1v maximum slope steepness <br />(s 40%, or 21 ° 49'); constructed in layers 2 feet thick or less compacted to 90% of <br />maximum dry density; benches 10' wide (according to the permit narrative; Exhibit 53 <br />shows a bench width of 15'); and lifts constructed on 30' intervals above the first lift, <br />which has a maximum height of 50 feet. The approved depth of non-toxic, non- <br />combustible cover soil is 24 inches based on field trials. Bench inslopes are to be <br />graded at 2% to 5%, and benches are to be graded to the side collection ditches at 2% <br />to 5% as well. The top of the fill also is to be graded at 2% to 5%, but not to drain over <br />the outslope. According to volume 1 of the mine plan, the outslopes of the fill are <br />considered the faces between benches. When each new bench is constructed, the <br />rough construction face below it will be "completed" by grading to final configuration. <br />One complete bench and outslope (final graded, but not covered) will be maintained <br />between the active fill area and lower covered areas. Placement of cover soil on an <br />area will be finished within a year of final grading of a second bench and outslope <br />above a completed area to avoid contaminating cover soil down slope. <br />Runoff controls for the CRDA-2 area include two collection ditches, a permanent <br />diversion, and five culverts. The east and west collection ditches (Exhibit 53, cross <br />sections J-J) were designed with trapezoidal cross-sections to handle runoff from 100- <br />year, 24-hour precipitation events. For collection ditch grades of about 3%, the permit <br />calls for a bottom width of 3', an unspecified top width estimated at 7.12 feet, a depth of <br />11", and 2h:1v side slopes. Ditch sections with grades of about 33% are to be <br />constructed with a bottom width of 3', an unspecified top width estimated at 9.34', a <br />depth of 17", and 2h:1 v side slopes. Design capacity for the west collection ditch is <br />27.6 cubic feet-per-second (cfs), and the east collection ditch's design capacity is 28.6 <br />cfs. Drainage from these ditches is routed to pond 10, which has a design capacity to <br />hold runoff from a 10-year, 24-hour event. The permanent diversion ditch (Exhibit 53, <br />cross section G-G) north of CRDA-2 was designed to have a top width of 18', a bottom <br />width of 4', a total depth of 3.5' including 1' of freeboard, a 1 % gradient, a trapezoidal <br />profile, and 2h:1 v side slopes. Design capacity is 75 cfs. A single 30" diameter <br />corrugated metal pipe (CMP) culvert is designed to convey drainage from the east <br />6 <br />