Laserfiche WebLink
New Horizon North Mine <br />Pond Design Memo <br />Introduction <br />There are several erosion and sedimentation control measures available for areas disturbed by coal mining <br />operations. Sedimentation ponds have been the most widely used and are required by federal regulations. <br />Sedimentation ponds are typically the last measure to provide sediment removal and meet the effluent limitation <br />before the runoff leaves the permit area. Thus the design of sedimentation ponds is based upon the pond's ability <br />to achieve specific effluent limitations. The Colorado Division of Reclamation, Mining, and Safety (DRMS) design <br />criteria are intended to prevent, to the extent possible, additional contributions of suspended solids outside of the <br />permit area and to achieve water quality standards. <br />In this memo, the design methodology and parameters are presented. The SEDCAD program was used for the <br />design of ponds and ditches. <br />Site Selection <br />The pond locations are selected considering the following factors: <br />1. Sedimentation ponds must be constructed in locations where it will be possible to direct or divert all <br />surface water runoff from disturbed areas into ponds through the life of mining operation <br />2. Topography of the mine site <br />3. Major sources of sediment <br />4. Accessibility of the sedimentation pond <br />5. Availability of construction material <br />6. Direction of mining <br />In most cases, the availability of suitable sites will be controlled by the topography of the mine site. The proposed <br />locations of the three ponds are based on the topography of the mine site. Ponds NHN -001, NHN -002 and NHN - <br />003 are near natural drainage paths. However, all require collection ditches to route flow from all disturbed areas <br />to the ponds. <br />Data Requirements <br />Hydrology <br />Hydrological information required to design a sedimentation pond includes the peak inflow rate and the runoff <br />volume for the design storm event. <br />The design storm precipitation data for the New Horizon North mine are the same as those used for the NH -2 <br />mine pond design. The data was obtained from the NOAA Precipitation Frequency Atlas Volume III — Colorado, <br />1973. Design data is as follows: <br />• 10 -year, 24 -hour — 2.0 inches <br />• 25 -year, 24 -hour — 2.4 inches <br />• 100 -year, 24 -hour — 3.0 inches <br />