2014-01-22_REVISION - M1990057

• Permit No: M1990057
• IBM Index Class Name: REVISION
• Doc Date: 1/22/2014
• Doc Name: Amendment 01 Adequacy review no. 4
• From: DRMS
• To: Union Milling Company, LLC
• Type & Sequence: AM1
• Email Name: MAC
• Email Name: TAK
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
MEMORANDUM
To: Michael Cunningham
From: Tim Cazier, P.E. A
Date: January 21, 2014
Re: Leadville Mill— Permit No. M- 1990 -057 /AM-01
Stormwater Comments
COLORADO
DIVISION OF
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
Loretta Pineda
Director
The Division of Reclamation, Mining and Safety (DRMS) engineering staff has reviewed the
November 26, 2013 responses to Adequacy Review No. 1 for the Leadville Mill. The following
comments are posed to ensure adequate engineering analyses and design practices are
implemented to eliminate or reduce to the extent practical the disturbance to the hydrologic
balance expected by the mining operation with respect to water quality and quantity in
accordance with Rules 3.1.6(1), 6.3.3(2)(c) and 7.3.1. Please note, as this site is a designated
mining operation (DMO), compliance with Rule 7.3.1 is applicable, thus requiring certified
designs and specifications for engineered elements associated with the environmental protection
plan (EPP). It should be noted that the SWMP required for The Colorado Dept. of Public Health
and Environment (CDPHE) is somewhat different from what the DRMS requires for DMOs.
Hydrologic Analysis:
1. No formal storinwater analysis is provided in the adequacy response. However, the
methodology and pertinent assumptions are discussed, and a "site- wide" result for the
100 -year, 24 -hour design peak flow is reported. The method utilized is simple enough
and the site small enough, that the DRMS was able to readily check the result. If based
on other comments below, the Operator deems it necessary to split out the hydrologic
analyses; the DRMS will require a formal analysis be presented. If the Operator splits
out the hydrologic analyses, the following should be provided:
a. Maps delineating contributing subbasins to each diversion and sediment pond.
b. Rationale for runoff estimation parameters (presumably SCS/NRCS curve
numbers). This should include ground cover rationale, and weighted area
calculations as well.
c. 100 -year, 24 -hour peak flow calculations /analyses for each diversion channel
and/or pond spillway.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines