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2013-10-31_REVISION - M1977284 (3)
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2013-10-31_REVISION - M1977284 (3)
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Last modified
6/15/2021 2:28:46 PM
Creation date
11/7/2013 8:47:52 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977284
IBM Index Class Name
REVISION
Doc Date
10/31/2013
Doc Name
Drainage Design Plan Mineral Joe Mine
From
Cotter
To
DRMS
Type & Sequence
AM1
Email Name
TC1
SJM
Media Type
D
Archive
No
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Whetstone <br />Associates4 Technical Memorandum <br />To: Stephanie Mitchel (DRMS) 4148B <br />Glen Williams (Cotter Corporation (N.S.L.)) <br />From: Susan Wyman, P.E., P.G. (Whetstone Associates) <br />Date: October 31, 2013 <br />Subject: Response to DRMS Second General Stormwater Comments <br />Permit Number M -1977 -284, Mineral Joe Mine <br />The Division of Reclamation, Mining and Safety (DRMS) prepared comments on the February 26, <br />2013 Drainage Design Plan for the Mineral Joe Mine in a memorandum from Tim Cazier to <br />Stephanie Reigh dated March 22, 2013. The Drainage Design Plan was submitted as part of Cotter <br />Corporation (N.S.L.) (Cotter) response to Adequacy Review #1 to the Mine Permit Application M- <br />1977 -284, Mineral Joe Mine. The March 22, 2013, DRMS comments are in italics below and <br />Cotter's responses are in bold. <br />The hydrologic method and analyses are very well presented with assumptions stated and <br />substantiated. Sections 1.2 through 2.2.3 and 3.0 through 5.1 exemplify what is expected of <br />hydrologic /runoff analyses for EPPs. <br />SCANNED <br />Cotter response: Comment noted. <br />2. Page 5, section 2.3.1. Trapezoidal channels were assigned side slopes of 1.5H.•1 V or 2H.•1 V. <br />Based on the photographic evidence presented in Figure 9 (p. 25), these values may be <br />appropriate for the channels as constructed. However, steep side slopes are unstable and <br />prone to sloughing that can lead to channel blockage and failure when constructed in <br />erodible material. These channels require modification in design and construction (if <br />already in place). The DRMS requires channel side slopes be no steeper than 3H.•I V, unless <br />it can be demonstrated that the specific material will be stable under the design flow at <br />2.5H.• I V. <br />a. Please redesign these channels as appropriate <br />b. Please commit to constructing /improving these channels to meet the redesigned <br />configuration to be approved by the DRMS. <br />Cotter response: The existing channels were surveyed in May 2013 to verify the side <br />slope ratios, local bed slope, conveyance capacity, and stability of the Upper, Middle, <br />and Lower Diversion Structures. The survey results are presented in Attachment 4 of <br />the revised Drainage Design Plan (DDP), and indicate that the average slide slope ratios <br />are 2.0:1, 4.8:1, 3.4:1, and 3.1:1 for the UDS, MDS, LDS -E and LDS -N, respectively. <br />Additional stormwater runoff modeling was performed to evaluate channel capacity <br />and stability based on these existing side slope ratios. Additional runoff modeling was <br />Whetstone Associates, Inc. <br />104 W Ruby Avenue ♦ Gunnison, Colorado 81230 • Phone 970 - 641 -7471 ♦ Fax 970 - 641 -7431 <br />
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