2008-12-04_PERMIT FILE - C1994082A ‎(4)‎

• Permit No: C1994082A
• IBM Index Class Name: Permit File
• Doc Date: 12/4/2008
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-12
• Media Type: D
• Archive: Yes

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Fe6rzrary 1999 Yoart Mine * 13-12 Drainage and Sediment CantralPlan •4

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TABLE 13-12.1
Yoast Mine Curve Numbers

Area
Condition
Cover Type' Hydrologic Hydrologic Soil Curve

Condition Grou : Numbed
Undisturbed
As en/Mountain Brush° Good >70%) B 30
Fair 30% - 70% B 4S
Good >70% C 41
Fair 30% - 70% C 57
Good >70% D 48
Fair 30% - 70% D 63
Stee Mountain BrushS Fair 0 - 70% B G7
Fair 0 - 70% C 77
Fair 0 - 70% D 83
Sa ebrush Good >70% B 35
Fair 30% - 70% B 51
Good >70% C 47
Fair 30% - 70% C G3
Good >70% D 55
Fair 30% - 70% D 70
Mesic Draina a Fair 30% - 70% C 81
Herbaceouss Good (>70% ~~ '`I
Herbaceous6 Fair 30% - 70% C 81
Herbaceouss Good >70% D 85
Herbaceous Fair 30% - 70°/, D 89
Western Wheat rasslAlkali Sa ebrush Fair 30% - 70% B 71
Western Wheat rass/Alkali Sa ebrush Fair 30% - 70% C 81
Western Wheat rass/Alkali Sa ebrush Fair 30% - 70% D 89
Rock Outcro Bare D 98
Disturbed'
Pit & Pre-Stri ed Bare C 91
Soil Bare B 86
Haul Road/Facili Area Bare D 91
Reclaimed Reve etated a Fair 30% - 70% B 71
Notes: 1) Undisturbed vegetation communities identified in baseline vegetation survey (ESCO Associates, 1993;
see Exhibit 10-1, Premining Vegetation Map)
2) Hydrologic soil group values adapted from Soils of Colorado, Loss Factors and Erodibility, Hydrologic
Groupings (SCS, 1983)
3) Curve number values adapted from Urban Hydrology for Small Watersheds (SCS, 1986)
4) Mountain brush and mixed brush [as labeled in Table 13-1] are the same vegetation community
5) Vegetation studies conducted by SCC did not identify any steep mountain brush communities with
"good cover"
li) Herbaceous cover type includes the pasture, rangeland, and meadow types identified in Table 13-1
7) These curve number values best describe the actual hydrologic response for these types of conditions
8) This HSG value was determined to best describe the hydrologic response by SCC and Division staff in
1999.
Montgomery Watron Mining Group * 165 S. Union Boulevard, Suite 460 * Lakewood Colorado 80228 * [phone]
TR-37
Revised (1R/IlA