2011-03-01_REVISION - M1981185 ‎(21)‎

• Permit No: M1981185
• IBM Index Class Name: REVISION
• Doc Date: 3/1/2011
• Doc Name: Memorandum ‎(CN-01)‎ Stormwater comments
• From: Tim Cazier
• To: Wally Erickson
• Type & Sequence: CN1
• Email Name: WHE
• 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
COLORADO
D IV Is 10 N OF
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
To: Wally Erickson
From: Tim Cazier, P.E. 1 1
Date: March 1, 2011
Loretta Pineda
Director
Re: May Day & Idaho Mill Complex - General Stormwater Comments, Permit
No. M-1981-185 / CN-01
The May Day & Idaho Mill Complex area is in an area characterized by steep slopes, exposed
road cuts and fill, and limited space for stormwater controls. 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 Rule 3.1.6(1).
1. The Table SWMP 1 and Tables SWMP A through M comprise 97 pages. There is no
narrative describing the general approach to stormwater control, hydrologic analyses,
purpose or design of hydraulic structures or rationale as to why drainage basins are
delineated as shown in Figure SWMP-2. Please provide a narrative (possibly including
an additional figure) describing the rationale used for hydrologic parameters (such as
curve number selection and precipitation depths) and analysis methods (e.g.,
nomographs, TR-55, etc.) drainage basin delineation and hydrologic routing method (if
used) or combined drainage basins (if hydrologic routing was not used), and a discussion
on hydraulic structure design criteria such as Manning's roughness, riprap sizing, and
freeboard estimates; debris basin design; culvert design/analyses; energy dissipation;
diversion channel placement and design; erosion protection; etc.
2. There are drainage structures depicted on Figure SWMP-1 that have no descriptions,
details, or design/sizing calculations. For example, other than labeling several "debris
basins" along existing access roads in Figure SWMP-1, there is nothing else in the
SWMP describing their purpose, how they will be sized, design rationale, or how they
will be constructed. Please provide a narrative, design rationale and construction details
or sketches for all BMPs shown on Figure SWMP-1.
3. There are several BMPs (e.g., Temporary Stream Crossings, Storm Drain Inlet
Protection, Outlet Protection, and Stabilized Construction Entrance/Exit) from the
Caltrans Stormwater Quality Handbooks presented after Table M, Augmentation Pond
Construction Runoff Control, that are not shown on Figures SWMP-1 or SWMP-2 and/or
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines