PERMFILE53867

• Permit No: M1977004
• IBM Index Class Name: Permit File
• Doc Date: 8/31/1984
• Doc Name: Response to Adequacy
• From: Homestake
• To: DMG
• Media Type: D
• Archive: No

-2-
Please also note that we are issuing a revised copy of Supplemental
Report S-2 dealing with the hydrology and erosion control measures for
reclamation. During review of data and calculations related to the hydrology,
an error in the areas used to evaluate run-off from catchment was discovered.
The result of this error has been to increase the calculated peak flow rates.
The revised report contains the corrected areas and recalculated peak flow
rates. The ditches and channels to be constructed at reclamation are
designed for ease of construction and maintenance-free operation. The
re suiting channel capacity was as much as ten times the initial calculated
peak flow values. The recalculated flow rates are still considerably less
than the channel capacities provided for in the design. Accordingly, no
revision of the design of the ditches has been made necessary.
The following item was raised in the Colorado Division of Water Resources
Letter of April 9, 1984.
Item: Homestake Mining Company should seek water rights to store run-off
from the basin in the South Pit and in the sedimentation reservoir. If
Homestake wishes to store water during periods of river administration,
a plan of augumentation is necessary.
Response: The question as to whether col]ection of surface water run-off
or accumulation of ground water and subsequent detention in reclaimed
mine pits, which would result in some additional evaporative losses,
constitutes a beneficial use of water for which a water right is required,
is not clear in Colorado law. If it becomes appropriate and, to the extent
that Homestake might adversely affect the availability of surface water to
downstream water users during the period of time the South Lake is filling,
provisions could be made as necessary to protect the other water users.
As is explained in Supplemental Report S-2, the available dead storage of
the lake is about 1,115 acre feet. The average annual yield of the Indian
Creek watershed was reported in our 1977 application as 3,640 acre feet.
Further compensating against adverse impacts or downstream flows is the
fact that the drainage area into the lake will be reduced 200 acres prior
to breaching the Crown Ditch and about 500 acres after breaching the ditch.
This area is a small portion of the 9.1 square mile drainage area of Indian
Creek and the 32.1 square mile drainage area of Marshall Creek upstream of
the confluence with Indian Creek. Thus Homestake does not anticipate adverse
effects on water uses during the gradual filling of the South Pit lake. In
addition, ground water will contribute to the inflow, thus lessening the
effect on surface water even more. Home stake's existing water rights at
the Pitch Mine would be sufficient to protect any senior appropriators in
the Gunnison Basin. However, it would be premature to formalize any plan
of augumentation or exchange until the law has been clarified, and until a
determination has been made as to the amounts of water involved and the
timing of flows.
Once the South Pit lake is filled, essentially continuous flow is
anticipated to be maintained based on ground water inflow into the lake,
precipitation, and seasonal run-off. It is important to explain that the
amount of water that could be evaporated from the lake surface would be
sma71, especially when compared to the water yields of the affected water-
sheds. The average annual net evaporative loss for the mine area is about
4.5 inches. The maximum surface area of the lake plus the sedimentation