2022-10-20_HYDROLOGY - M1977493

• Permit No: M1977493
• IBM Index Class Name: Hydrology
• Doc Date: 10/20/2022
• Doc Name: Spill Report Response
• From: Climax Molybdenum
• To: DRMS
• Email Name: LJW
• Email Name: THM
• Media Type: D
• Archive: No

Mr. Lucas West, DRMS
Page 3 of 3
October 10,2022
route/convey water to the Mayflower Clear Pond (also lined) via gravity. The event that this
submittal covers occurred adjacent to the Mayflower Clear Pond emergency spillway. The two
Mayflower Seepage Collection Ponds and the Mayflower Clear Pond are concrete-lined basins
intended to store Mayflower TSF seepage water until it can be pumped back to the Mayflower TSF
operating pool. None of the three ponds described have secondary containment, rather they are
impermeable basins. The pump-back pipeline also does not have secondary containment. Under
emergency flow conditions, the Mayflower Clear Pond has a concrete emergency spillway that
routes water to a drainage that eventually leads to Tenmile Creek.
The purpose of the Mayflower Clear Pond is to serve as an equalization basin. Water in Mayflower
Clear Pond is pumped to the Mayflower TSF via the Mayflower Seepage Pump-back System,
consisting of a redundant pump system and buried pipeline. The average flow of seepage into the
Mayflower Seepage Collection Ponds and the Mayflower Clear Pond since 2015 is approximately
1,100 gallons per minute (gpm). Mayflower Clear Pond is normally operated at a nominal depth of
6.5 feet and is maintained through level monitoring instrumentation. Mayflower Clear Pond has a
total capacity of 5.9 million gallons and has remaining capacity of 2.2 million gallons when the level
is at 6.5 feet. At the average inflow rate, the pond has approximately 31 hours of capacity until the
water level would reach the emergency spillway (at 9.33 feet).
Mayflower Clear Pond has 4 electric pumps to convey water back to the Mayflower TSF operating
pool; in normal operations two of the four pumps are in operation and a third operates when flow
rates are higher (e.g., runoff season). The fourth pump is a spare. There are also a series of
instruments that function to monitor critical elements of the system including a level instrument,
flow meter and pressure gauge. Alarms exist for the Mayflower Clear Pond level, flow rate and the
pump-back pipeline pressure. Alarms report to the main water operations control room in the
Property Discharge Water Treatment Plant (PDWTP). The pump-back system also has emergency
generator power should an electricity power outage occur.
As described above, Climax is committed to completing an engineering study and submitting a TR
for the preferred option from that study.
Please contact me at [phone] if you need additional information.
Sincerely,
;F�EL:I 1�5�
Eric Detmer, PE
Chief Environmental Engineer
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