2022-04-04_PERMIT FILE - M2022013 ‎(38)‎

• Permit No: M2022013
• IBM Index Class Name: Permit File
• Doc Date: 4/4/2022
• Doc Name Note: Exhibit G - Flood Control Mitigation Plan
• Doc Name: Application
• From: Varra Companies, Inc.
• To: DRMS
• Email Name: RDZ
• Email Name: MAC
• Media Type: D
• Archive: No

Two Rivers Gravel Pit Mine
Riverside Berm Failure Analysis
and Flood Control Mitigation Plan
' ' ' January 22,2020
TWO RIVERS
FILL TIME ESTIMATES
CENTRAL PIT
Inc GW Inflow Rate- GW Inflow Rate- River Inflow- Cummulative Elevation
Pit Depth Pit Elev Pit Vol Volume GW Inflow Rate Ave Ave HG Time Ave River Inflow Total Inflow Inflow Volume Inflow Volume (ft)
(af) (af) (af/day) (af/day) (af/hr) (hr) (cfs) (af/hr) of/hr (af) (af)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (14) (15)
0 4688.0 5,665 0 459 5,158 215 48 12,600 1,041 1,256 15068 27856
10 4678.0 4000 1,665 2,633 5,158 215 36 10,300 851 1,066 12788 20455
20 4668.0 2300 1,700 4,443 5,158 215 24 9,000 743 958 7667 12029
30 4658.0 600 1,700 6,252 5,158 215 16 4,000 330 545 4363 8064
5,158 215 12 3,000 248 463 3702 6743
5,158 215 10 2,000 165 380 3041 4396 4682.0
32 4656.0 0 600 9,858 5,158 215 8 1,500 124 339 1355 1868 4667.0
5,158 215 4 500 41 256 512 748 4660.0
5,158 215 2 250 21 236 236 459 4657.5
5,158 215 1 100 8 223 223 223 4657.0
5,158 215 0 0 0 4656.0
NOTES
(1) Pit depth increments arbitrarily chose 10 ft. Pit depth from Joby analysis: (C:\DATA\Flow Tech nologies\Projects -FT\Varra\FT1910 -Two Rivers\H&H\GW Inflow-Joby).
(2) Based on (1). Based on (1). El 4688 from Existing Topo,fn =C:\DATA\Flow Tech nologies\Projects-FT\Varra\FT1910 -Two Rivers\Drawings\Existing Topo.pdf.
(3) From Brad Jones email 10/26/19, "update on individual extraction volumes." Email file also in, C:\DATA\Flow Tech nologies\Projects-FT\Varra\FT1910 -Two Rivers\H&H\Pit
Volume, Fill Time\Two Rivers. Max volume computed from cubic yards, and other volumes extrapolated.
(4) (4) minus (3).
(5) From Joby analysis: (C:\DATA\Flow Technologies\Projects-FT\Varra\FT1910 -Two Rivers\H&H\GW Inflow -Joby). Mid-values extrapolated.
(6) Average of 459 and 9,858. Average because no way of knowing inflow at times and water surface elevations of inflow HG, so average of high and low is reasonable.
(7) (6) converted to of/hr so fill times can be computed in hours per(12).
(8) & (9) From, C:\DATA\Flow Tech nologies\Projects -FT\Varra\FT1910 -Two Rivers\H&H\WinDAM C Inflow HG.
**Note. It is assumed that 2/3 inflow floodplain HG enters Central Pit.
(10) (9)*0.0826.
(11) (7) +(10)
(12), (13) Fill time for use in comparing fill time with head cut depth. However, it doesn't give pit water surface elevation.
(14) From, "TWO RIVERS DESIGN HYDROGRAPHS (WINDAM C INPUT HGs) FOR REPRESENTATIVE HEADCUT AT BIG THOMPSON SIDE AND SOUTH PLATTE SIDE PITS."
(14, (15) Cumulative volume for use in obtaining elevation from elevation-storage curve ((2), (3)).
pg. 30