2024-11-04_PERMIT FILE - M2024056 ‎(6)‎

• Permit No: M2024056
• IBM Index Class Name: Permit File
• Doc Date: 11/4/2024
• Doc Name: Application
• From: Asphalt Specialties Co., Inc
• To: DRMS
• Email Name: NCG
• Email Name: JLE
• Email Name: EL1
• Media Type: D
• Archive: No

pitside slope during flood events. These structures are of a design approved for use by the Mile
High Flood District. Details of the inflow/outflow structure are shown on Map F-2.
6.2. Disturbed Area Runoff
During all stages of mining, there is enough water storage capacity to contain the 5-year and
100-year 24-hour storm events and prevent erosion from surface water discharge. The
expected rainfall from these events at the Evans Site is provided in Table G-2 below.
Table G-2. Area Storm Events (from NOAA2)
Event Probability Event Rainfall
(inches)
100-YR 24-HR 4.74
The peak runoff was generated from these values for the three drainage basins during all
stages of mining. Pre-mine, mining, and reclamation conditions are delineated on the Drainage
Map. The discharge volumes from these storm events are calculated in Appendix G-1 at the end
of this exhibit. Table G-3 summarizes the runoff volumes and storage volumes for each
drainage. All drainage calculations were made using the Rational Method identified in the Mile
High Flood Control District.
Table G-3. Drainage Calculations
Drainage Basin Runoff& Destination
Drainage Phase of Area Runoff 100-YR 24- Detention Discharge Flow
Basin Operation (ac) Coefficient HR Runoff Capacity Rate(gpm)*
(ac-ft) (ac-
ft)***
1 Baseline 39.8 0.23 1.41 N/A 0
Mining 0.37 2.64 500+ 1000-3000**
Reclamation 0.59 4.21 43 0
Reclamation 0.23 1.41 N/A 0
Alternative
2 Baseline 120 0.22 4.42 N/A 0
Mining 0.4 8.60 2000+ 1000-3000**
Reclamation 0.7 16.75 156 1 0
Reclamation 0.21 4.21 N/A 0
Alternative
*The discharge flow rate is calculated from the peak discharge of the 100-Yr 24-Hr storm event.
**Discharge flow rate is variable and controlled during mining as all discharges are pumped from the pit
***Detention Capacity calculated in CAD as volume in pit or volume above water storage.
2 National Oceanic and Atmospheric Administration
Evans Mining Resource
October 2024 G-4 1:1Lewicki ik Associates