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REV03100
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REV03100
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Entry Properties
Last modified
8/25/2016 1:00:53 AM
Creation date
11/21/2007 9:06:12 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1983058
IBM Index Class Name
Revision
Doc Date
10/28/1994
Doc Name
ADEQUACY REVIEW TR 7 FINAL RECLAMATION PLAN TWIN PINES MINE PN C-83-058
From
DMG
To
LAWRENCE G WHITE PE
Type & Sequence
TR7
Media Type
D
Archive
No
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Ivlr. Lawrence G. White, P.E. -4- October 28, 1994 <br />2. These pile locations should be shown on a permit document map or figure. Please provide <br />this, if it is not already in the permit document. <br />3. Please specify the reclamation plan for the topsoil pile locations. <br />Drainage/Sediment Control <br />1. Please commit to the placement of additional silt fences along the hillslopes which will be <br />exposed when the Lewis Gulch fill is removed. <br />2. Please verify that any flow emanating from the cobblestone check structure will be directed <br />to the bench pond, and not down the access road. Note: The cobblestone structure may <br />not ultimately be approved. Refer to number 9 below. <br />3. The refuse pile and refuse pile road ditch/swale configurations have been previously <br />reviewed and approved, as indicated in my previous memorandum of December 1, 1993 <br />(Berry to Smith). I assume that the plans have not changed since that time. Is this correct? <br />4. The proposed drainage control plan for the upper bench may require revision, depending <br />upon the resolution of the issue discussed at Dumber 9 (Backfilling and Grading) above. <br />5. Detail A (T'P-5) indicates an 18-inch culvert in the cobblestone check strocture, but the text <br />(proposed page 8'~ indicates a 12-inch culvert. Please clarify. Note: Refer also to <br />pumber 7 below. This culvert may not ultimately be approved. <br />6. Specific small area exemption demonstrations will need to be derived for any reclaimed <br />areas (excluding the road) not draining to a sediment pond. Typically, this can be done <br />using the SEDCAD software, when heavy mulching and silt fences are approved. We will <br />assist in this process, if desired. <br />Specific mine site locations of concern are the slopes left following Lewis Gulch fill <br />removal, the backfilled area along the road (adjacent to the Lewis Gulch fill), the topsoil <br />pile locations, and any other areas not draining to a sediment pond. <br />Please provide the demonstrations which comply with Rule 4.05.2(3), and/or advise us if <br />assistance is desired. <br />7. Based upon our calculations, we agree that the upper bench will experience a peak flow of <br />about 10 or 11 cubic feet per second (cfs) during the 10-year, 24-hour event. Our calcula- <br />tions indicate, however, that the proposed 18-inch culvert is too small to safely pass this <br />flow. Any flow larger than this would certainly cause a failure. Please propose an alter- <br />nate plan, which might include a riprapped, open channel flow from the upper bench to the <br />lower bench. <br />
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