1987-12-01_PERMIT FILE - C1981017 (107)

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June 17, 1987 Ms. Candace Thompson Hydrologist Mined Land Reclamation 1313 Sherman Street, Room 423 Denver, CO 80203-2273 Re: TR-08, Sutey Expansion, File No. C-81-017 Dear Ms. Thompson: The following discussion is in response to your adequacy review letter dated May 13, 1987. The location of the new pond, intake, vegetation reference area and topsoil piles have been accurately shown on Map 2 of 2. Cutoff collars will not be used for the new sediment pond because we are planning to use the existing 48" CMP that now runs under the road for the diversion ditch. In other words, the new pond will be built around this culvert. This culvert has been in existence for several years and has shown that it does not leak around the outside of the pipe. The snow runoff index used in the USLE was obtained from the book, "Applied Hydrology and Sedi mentol ogy for Disturbed Areas" , 19B1 , Barfield, Warner and Haan, page 316. This factor takes into account the effect of spring thaws. The factor PD-,., is precipitation in inches from December to May. I used precipitation data for the last 10 years to obtain our PD-m. Due to our sometimes large spring runoff , all new ponds and ditches in Coal Basin will be designed with this factor. From Map 2 of 2, Drainage Area III is shown as an outslope of the final pile configuration. As you will note, all runoff from this area will flow down the slope to the West Collection Ditch. The 1% arrow was drawn in the wrong direction for Areas VI and VII. It should be drawn to the west and has been changed on Map 2 of 2. Runoff Area VI will flow down the outslope to the edge of Runoff Area VII. Then runoff from both areas will flow westward to the West Collection Ditch. Therefore, no new runoff will flow to the East Collection Ditch and the existing ponds. 97