REP24235

• Permit No: C1981044
• IBM Index Class Name: Report
• Doc Date: 3/3/1988
• Doc Name: 1987 MINE INFLOW STUDY internal memo
• From: MLRD
• To: GREG SQUIRE
• Permit Index Doc Type: Hydrology Report 1987
• Media Type: D
• Archive: No

III IIIIIIIIIIIIIIII
STATE OF COLOIZnvv
Roy Romer, Governor
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Director
DATE: March 3, 1988
T0: Greg Squire
FROM: Jim Stevens JGS
RE: Eagle Mine (Permit No. C-81-044) 1987 Mine Inflow Study
I have reviewed the above referenced study. As a result of the sealing off of
even more of the mine during 1987 and changes in the drainage system within
the mine this study now covers relatively few of the significant specific
sources of the inflow to the mine. Only a total of 84 qpm of inflow was tied
by the study to specific sources or areas of the mine while an average
apparent mine inflow of 564 qpm was calculated for 1987 using the metering of
the mine water discharge.
Since there is so significant a lessening of the relationship between the
annual inflow study and the apparent actual inflow, I am agreeable to
approving Empires proposal to discontinue the study until, and only in the
event of, the apparent annual average inflow; as measured by the metering of
the mine water discharge, exceeds the operator's predictions by ?0% or more.
I have discussed this with Larry Damrau together with which series of annual
inflow predictions should be used as a basis of the calculation and how the
accuracy of the metering could be confirmed. The metering was found to be
faulty in the past so some provision rtlust he made to assure its future
dependability.
I am proposing that the estimates of mine inflow predicted by the Jacob-Lohman
method contained in Table 75, p. 2.06.6-11 of the permit application be used
as the basis of the calculations for "excessive inflow". These estimates
appear closer to the actual inflow experienced in the past and are the more
conservative of the two series of predictions made by the operator: I don't
think the mine should consider using the Jacob-Lohman predictions a hardship.
The inflow predicted for 1987 by this method is 28% larger than that actually
experienced, i.e.780 v 564 qpm, which is a substantiTushicn. In order for
the 1987 inflow to have been "excessive" i.e.20% greater thar~ prediction, it
would have had to be 936 qpm or 66% greater than that actually experienced.
In regard to establishing the accuracy of
meter should be tested annually by either
Division could accept. Even a record of
etc could provide a means of checking any
water.
the mine discharge metering, the
a firm or some method that the
the hours the pumps operated daily
variations in the metered volume of
/bca
5757E
423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]