2011-08-08_REVISION - M1977493 ‎(40)‎

• Permit No: M1977493
• IBM Index Class Name: REVISION
• Doc Date: 8/8/2011
• Doc Name: EPP- Robinson Lake Operating Plan.
• From: Climax Molybdenum
• To: DRMS
• Type & Sequence: TR18
• Media Type: D
• Archive: No

Robinson Lake Surcharge Storage Capacity
Elevation
(feet)
Depth Below
Spillway (feet)
Surcharge Storage
Capacity (acre -feet)
10,890
0
0
10,889
1
81
10,888
2
161
10,887
3
240
10,886
4
319
10,885
5
397
10,884
6
474
10,883
7
549
10,882
8
628
10,881
9
698
10,880
10
771
•
Robinson Lake Operating Plan Climax Molybdenum Company
Version: R1 Permit M -1977 -493
Facility (TSF) water pool can be released through the Tenmile Decant and water from the
Mayflower TSF water pool can be reclaimed using a future pump barge. Both of these facilities
discharge into the Tenmile Tunnel. Fresh water from Supply Canal No. 2 can also be
discharged into the Tenmile Tunnel. Inside the tunnel, bulkhead valves can be operated to
direct water toward the south to Robinson Lake or toward the north to the Mayflower TSF.
These valves are hydraulically actuated and controlled by a hydraulic pump located on the
ground surface above the tunnel bulkhead.
2.5 Robinson Lake Surcharge Storage Capacity
In 2008, 2010, and early 2011, Climax conducted a project to remove sediment from within
Robinson Lake. The modified lake contours were partially surveyed in 2010. Climax intends to
conduct a bathymetric survey of the lake in 2011. The 2010 survey data was coupled with data
from a 2006 aerial survey to determine the currently available surcharge storage capacity in
Robinson Lake. The spillway control crest lies at an elevation of 10,890. Robinson Lake has
the following surcharge storage capacities for the incremental water levels for the top ten feet
below the spillway crest.
EPP — Appendix D
3.0 NORMAL OPERATING CONDITIONS
Figure 1, attached, presents the drainage basins tributary to Robinson Lake under normal
operating conditions when no extreme flood events are occurring. For this condition, the Chalk
Mountain Interceptor collects unimpacted runoff and snowmelt from the northeast side of Chalk
Mountain and conveys it around the Climax facilities for release either into Eagle Park Reservoir
or into the upper Eagle River basin. As shown on Figure 1, the area below the Chalk Mountain
Interceptor can be partitioned into three distinct drainage basins consisting of approximately 54
acres tributary to Chalk Mountain Reservoir, 218 acres tributary to the Warren's Pump System,
and 152 acres directly tributary to Robinson Lake. Chalk Mountain Reservoir and the Warren's
Pump System lie within the overall Robinson Lake basin so that the total 424 acres together are
tributary to Robinson Lake. Water that is discharged through the spillway on Chalk Mountain
Dam and water that overflows Warren's Pump System flow directly into Robinson Lake.
During 100 -year snowmelt conditions, the 1 -day rate of snowmelt runoff tributary to Warren's
Pump System would be about 3,330 gpm. Under normal operating conditions, this water, along
with the 1 Dam seepage of up to about 1,000 gpm, would be pumped by the Warren's Pump
August 2011 2