2025-05-14_PERMIT FILE - M2025025

• Permit No: M2025025
• IBM Index Class Name: Permit File
• Doc Date: 5/14/2025
• Doc Name: Application
• From: Minewater LLC
• To: DRMS
• Email Name: ERR
• Email Name: ZTT
• Email Name: EL1
• Media Type: D
• Archive: No

Time of concentration for each basin ranges from 1500 to 2500 ft, based on the range of distances from
the top of area ridges to the bottom of the gulch. Based on these standard drainage basins, the
following 10-YR, 24-HR event peak flows were determined using the Rational Method.
Table G-1. Standard Basins and Peak Flows
Standard Basin Size 10-YR,24-HR Peak Flow(CFS)
5-acre 9.85
10-acre 19.70
20-acre 39.40
30-acre 56.58
40-acre 75.44
50-acre 90.48
The standardized drainage basins provide peak flows that standard diversion structures can be
designed around. Each waste pile will have a diversion structure installed uphill of it to route local runoff
around it while mining and reclamation is occurring. Map C-2 and C-2A detail these structures. The
hydrologic design basis can be found in Appendix G-1. Diversion structures of the following depths will
handle a corresponding flow:
Table G-2. Uphill Diversion Structure Depth vs. Flow Capacity
Depth(ft) Flow Capacity(CFS)
1.5 23.2
2.0 50.0
2.5 90.6
3.0 147.4
Note: Design figures in Appendix G-1 show diversion structure sizing calculations.
When a waste pile is selected for cleanup, its uphill drainage basin size will be determined and it will be
assigned to a standard basin size at least as big as the drainage measured. Using this standard basin
size, the peak flow can be used to determine the depth of the diversion structure that said waste pile
requires. Therefore, the diversion structures shown on Map C-2 and C-2A will have varying depths
depending on the waste pile being mined.
Stormwater control structures will be installed on the downhill end of the waste pile and at the crest of
the waste pile slope. Mining will typically be conducted from the top of a waste pile downward, to
minimize the amount of waste pile disturbed at any time, and to provide a working surface for
excavation equipment. The stormwater control structure along the edge of the active working surface
will thus contain any stormwater runoff from the active area until it evaporates. See Map C-2 and C-2A
for details of these structures.
3. Water Consumption
Water consumption at the operation will be for the purpose of dust control only. Given the handling of
Potentially Acid-forming Material as part of waste pile excavation, water will not be sprayed on the
London Mountain Clean Up
April 2025 G-2 11 Lewicki&Associates