2011-05-17_PERMIT FILE - M2011001

• Permit No: M2011001
• IBM Index Class Name: PERMIT FILE
• Doc Date: 5/17/2011
• Doc Name: Second Adequacy Review
• From: DRMS
• To: Lafarge West, Inc.
• Email Name: PSH
• Email Name: AJW
• 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]
I&Y 17, 2011
Mr. Todd Ohliheiser
?(afarge west, Inc.
10170 Church Ranch Way, Suite 200
Westminster, Colorado 80021
RE: Lafarge West, Inc.; File No. M-2011-001
Iverson Mine; 112c Permit Application Second Adequacy Review
Dear Mr. Ohliheiser,
COLORADO
D I V I S I ON Of
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
Loretta Pineda
Director
The Division of Reclamation, Mining and Safety (Division) has reviewed the content of the Lafarge West,
Inc. (Lafarge) 112c permit application adequacy response dated April 29, 2011 for the Iverson Mine, File
No. M-2011-001, and submits the following comments. The Division is required to make an approval or
denial decision no later than July 25, 2011 therefore; a response to the following adequacy review
concerns should be submitted to the Division as soon as possible.
Questions #1-15 were answered satisfactorily by the Applicant in the April 29, 2011 response.
16. Portions of the proposed mine site lie within the 100-year flood plain of the Cache la Poudre River. In
the event of a significant flood event (100-year flood or greater) it is likely the proposed pit will be
captured by the Cache La Poudre River. Wherever mining will occur within 400 feet of the river
channel, a flood analysis and flood control plan must be evaluated and submitted. This would include
pit side armoring, river side armoring, inflow and outflow channels, or other appropriate measures.
Accordingly, the Division requests the Applicant provide the flood elevations(s) to be expected under a
"worst case" flooding scenario and specific mitigation measures that will be implemented to minimize
the potential for any offsite impacts.
The potential for "berms" around gravel pits to be damaged during floadirrg-"isc n etas m t e
1987 Urban Drainage and Flood Control District (UDFCD) Publication "Technical Review Guidelines for
Gravel Mining Activities within or Adjacent to 100-year Floodplains." Strips of native ground or
constructed fill between the stream and the gravel pit, and generally aligned with the flow direction of
the stream are referred to in the UDFCD document as riverside berms. Riverside berms are proposed
in the Iverson Mine application, which may be prone to erosion during a flood event. The required
inflow/outflow structures are intended to mitigate possible slope failure during flood events for these
berms. The Iverson Mine is outside of the political boundaries of the UDFCD, but the technical
floodplain factors that led to the formation of the UDFCD guidance still apply and will be used to
review the adequacy of the flood mitigation structures proposed for the site. Additionally, the site and
surrounding area have a history of flooding as demonstrated by the flooding event last summer which
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