2011-02-23_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 2/23/2011
• Doc Name: Ground Water Review ‎(Memo)‎
• From: Tom Kaldenbach
• To: Janet Binns
• Type & Sequence: PR3
• Email Name: JHB
• 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]
MEMO
COLORADO
D IV IS I ON OF
RECLAMATION
MINING
SAFETY
DATE' February 23, 2011 John W. Hickenlooper
Governor
FROM: Tom Kaldenbach `fie- Mike King
Executive Director
To: Janet Binns Loretta E. Pineda
Director
Re: Colowyo Mine (C-1981-019), PR-3, Ground Water Review
The following comments can be forwarded to the operator. (Additional review comments on ground
water topics have previously been provided to you by Kent Gorham and Rob Zuber.)
1. Please add a notation to Table 2.04.7-42 explaining the meaning of the abbreviation "ND".
2. Please add to Section 2.05.6(3)(b(iii) a calculation of annual seepage of spoil water into the
downdip pitwalls of both pits, using the Darcy equation for flow through a porous medium. The
equation is Q = KA(h/l), where Q is volume of flow per unit time, K is hydraulic conductivity,
and h/1 is the hydraulic gradient (USGS Ground Water Manual, 1977, page 20). Please use in the
calculations a hydraulic gradient of 0.1 ft/ft, based on a representative 6-degree bedding plane dip
in the area (hydraulic gradient = tangent of 6 degrees = 0.1).
3. Please revise the prediction of spoil spring discharges to the surface (Section 2.05.6(3)(b(iii)) to
reflect the requested calculations of annual pitwall seepage.
4. The DRMS will complete its review of the proposed hydrologic monitoring plan after receiving
the requested calculations of pitwall seepage and spoil spring discharges.
5. The groundwater lab parameter table in Section 4.05.13 indicates several metals will be analyzed
for the "total dissolved" concentration, rather than the "dissolved" concentration. When analyzing
a sample for the "total dissolved" concentration, will particulates of the constituent be removed
from the sample before performing the analysis?
6. In the groundwater lab parameter table in Section 4.05.13, please change the analysis for iron
from "total" to "dissolved". Although DRMS Rule 2.04.7(1) specifies analysis for "total" iron in
baseline data collection, the standards for iron in the Basic Standards for Groundwater (Colorado
Water Quality Control Commission Rule 41) are for the "dissolved" concentration.
Office of Office of
Mined Land Reclamation Denver • Grand Junction Durango Active and Inactive Mines