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 Operating Plan Climax Molybdenum Company
Version: R1 Permit M -1977 -493
PMP event, plus five days worth or 43 acre -feet of seepwater inflow from the 1 Dam, Robinson
Dam, and 4 Dam seepage collection systems, plus two days worth, or 88 acre -feet, of diverted
inflow from the Tenmile Tunnel throughout the year. To meet these criteria, the surcharge
storage requirement is 387 acre -feet. This volume of surcharge storage capacity can be
achieved by setting the upper operating limit for Robinson Lake at an elevation of 10,885 feet.
This level is five feet below the control crest of the emergency spillway on Robinson Dam.
During the period from April 15 through July 15 which corresponds to the time frame when
high snowmelt can occur, Climax will maintain an additional allowance for five days worth, or
191 acre -feet, of the 100 -year snowmelt runoff from the entire Robinson Lake drainage basin
including the area above the Chalk Mountain Interceptor. During this period, the total surcharge
storage requirement would then be 578 acre -feet. This volume of surcharge storage capacity
can be achieved by setting an upper operating limit for Robinson Lake at an elevation of 10,882
feet. This level is eight feet below the control crest of the emergency spillway.
6.0 FACILITY MONITORING AND CONTROL SYSTEMS
6.1 Robinson Lake
Visual monitoring of Robinson Lake is performed routinely by Climax personnel. When the
construction of the Robinson Lake Pump Station is completed and the facility brought online, it
will operate as the main level control for Robinson Lake. A water level indicator will be installed
to continuously monitor the water level within Robinson Lake. The water level indicator will be
connected telemetrically to the mill control room to provide immediate notification should water
levels exceed set points for high water action levels.
6.2 Robinson Lake Pump Station
The Robinson Lake Pump Station will be the primary facility to remove water from Robinson
Lake. This pump station pumps water from the lake to the mill facilities. The pump station has
a nominal pumping capacity of 10,000 gpm with two pumps running. A third pump is installed
as a backup during normal operating conditions and could be used to evacuate additional water
from Robinson Lake if needed. Pressure indicators on the intake and discharge sides of the
pumps will control operation of the pumps and will also be tied to automated alarms to warn of
upset conditions. As with the other pump stations at Climax, the pump station pressure alarms
will be connected telemetrically to the mill control room to provide immediate notification should
intake or discharge pressures exceed certain set points or pump upsets occur.
The pump station is also equipped with instrumentation to monitor pump operating status,
temperature, and vibration as well as discharge flow rate. These parameters will be relayed to
and monitored at the mill control room.
6.3 Robinson Dam
Robinson Dam is considered to be a jurisdictional dam by the Dam Safety Branch of the
Colorado State Engineer's Office (SEO) and must therefore meet the dam safety and inspection
requirements of the SEO's "Rules and Regulations for Dam Safety and Dam Construction." The
Dam is inspected regularly by Climax personnel and generally once per year by SEO personnel.
A total of nine piezometers are located in the Robinson Dam embankment. Seven piezometers
are located along the dam crest for monitoring phreatic water levels in the embankment. Five of
the dam crest piezometers are full- depth, that is, they extend from the dam crest down to the
EPP — Appendix D
August 2011 4