GENERAL37809

• Permit No: M1977215
• IBM Index Class Name: General Documents
• Doc Date: 11/24/2003
• Doc Name: Response to USFS Assessment
• From: Homestake Mining Company
• To: USFS
• Media Type: D
• Archive: No

Mr. L. Dobson
11/14/03
Page 2 of 7
Regrading and placement of a vegetative soil cover on the facility.
9360 waste rock facility
Construction of a cutoff structure above the facility and replacement of the old metal bypass
culvert with a new FIDPE pipe to route upstream flows in Windy Gulch through the facility
without resulting in contact with the waste rock.
Construction of a lined overflow channel on the facility.
Regrading and placement of a vegetative soil cover on the facility.
Lower tailings facility
Regrading of the embankment.
Placement of a vegetative soil cover over the entire facility area.
As a result of these additional reclamation activities, much of the descriptive information in the PA
concerning the 9700 and 9360 waste rock facilities and the lower tailings facility is incorrect and does
not reflect conditions that existed as of the date SAIC issued the PA.
2. The PA does not accurately discuss the purpose and status of the existing adit plug. The plug was
designed and installed to eliminate seasonal flow (occurring during Spring melt) that was observed
from the 9360 adit portal as a result of inflow into the adit from the Creede Formation contact. The
purpose of the plug was to ensure that seasonal seepage would either remain within the Creede
Formation or flow back info the deep mine pool via the underground workings.
When the adit plug was installed the water level in the deep mine pool was unknown. Thus, a
contingency was built in to allow water pressure behind the plug [o be reduced if increased pressure
build-up was observed. A pressure threshold of 11 psi (25 ft of water) was chosen because the
geometry of the underground workings indicated that any water buildup beyond this level would flow
back into the deep mine pool from the 9360 adit area. This threshold was chosen simply as an indicator
as to whether the deep mine pool was building up to a level above the plug, not as an indicator that
pressure was building at which the plug would fail. Subsequent to installation of the plug, the water
level in the deep mine pool has been measured and shown to range in elevation from approximately
9237 feet to 9246 feet. Thus, the deep mine pool level is well below the plug elevation, which is at an
elevation of approximately 9360 Feet.
The adit plug was monitored for over two years since its installation and has performed according to
design specifications. As a result, final closure of the 9360 adit was conducted in accordance with
Technical Revision 7 to the Colorado DMG Mine Reclamation Permit and provisions in the USFS
Operating/Reclamation Plan addressing [he 9360-adi[ work.
3. The PA appears to assume the shallow flow from surface water in the Windy Gulch alluvial
materials to be groundwater. Flow data presented in the Windy Gulch Assessment (Water Management
Consultants, Inc. (WMCI) report, dated December, 1999) indicate that there is generally a slight net
loss of flow in Windy Gulch from the upper weir at the Bachelor Road to the tower weir near Willow
Creek. The Windy Gulch Assessment concludes that "Windy Gulch is a losing stream through its
middle and lower reaches." Thus, the so-called "groundwater" described in the PA is, in fact, surface
water that is flowing in the alluvial deposits along Windy Gulch.
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