1986-09-19_REVISION - C1981012 (4)

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n~chartl D. Lamm Governor DEPARTMENT OF NATURAL RESOURCES David H. Gelches, Executive Director MINED LAND RECLAMATION DI\ DAVID C. SHELTO N, Director DATE: November 14, 1986 T0: Jeff Deckler FROM: Randy Price ~~" ~Qf RE: NEW ELK MID-TERM REVIEW, TECHNICAL REVISIONS 06 AND 09, NEW ELK MINE, PERMIT N0. C-81-012 I have reviewed the portion of the New Elk permit application pertaining to surface hydrology. The information submitted in the permit application was inadequate for determining peak run-off and culvert sizing for areas within the permit area and for undisturbed areas draining into the permit area. The following are inadequacies that I have found in the application: 1. A map delineating the drainage basins referenced i.n Table 20 was not included in the application. Undisturbed areas draining to the Diversion ditch were also not included in the sediment and surface water control plan Maps 13 and 14. I was unable to verify the exact acreage used in Table 20. A map of appropriate scale should be submitted delineating the contributing drainage areas referenced in Table 20. The drainage basins should also be outlined on surface water maps and identified by numbers that should correspond to the numbers in Table 20. I have reviewed the soil types and vegetative cover in drainage areas 9, 10, 11, 18, 26, 27. In the permit application these areas have been given a curve number of 72. Given the soil type and vegetative cover a CN of 72 is not justified. For Area 27, the Allen Mine permit application Volume II, Exhibit 12, page 9 stated that the Ponderosa Pine-Oak reference areas had a average cover of 4.1 percent. The soil in Area 27 are classified in the permit as a Fuera-Dargol-Varner complex. The soil has a predominately D hydrologic classification. Based on the vegetative cover and soils classification, a CN of 72 can not be supported. New Elk Mine must submit data on vegetation and soils to support a CN of 72 for Area 9, 10, 11, 18, 26 and 27; or based on the current soils and vegetation recalculate the CN number. Should the CN number change, the peak discharge values for these areas should be recalculated and Table 20 revi sed. Areas 9, 20 and 23 were recalculated for peak discharge using the given CN numbers and the peak discharges were higher than those in the permit 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567