2009-05-19_REVISION - M1977285 ‎(31)‎

• Permit No: M1977285
• IBM Index Class Name: REVISION
• Doc Date: 5/19/2009
• Doc Name: EPP ‎(AM-03)‎ Att. P: Drainage; Att. Q: SWMP Repair; Att. R: Rock & Soil Characterization ‎(part 10)‎
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM3
• Email Name: RCO
• Media Type: D
• Archive: No

Section 6
Sunday Mine
Table 6-2 Input Values for Channel 1 Ca aci Anal sis

Channel 100-yr Q
cfs S
ftNt
n z
ft/ft b
ft
1 19.61 0.01.6 0.035 3 0
The calculated channel depth and flow velocity of Channel 1 are shown in Table 6-3.
CDM recommends adding 2-feet of freeboard to the calculated flow depth to account
for potential channel overtopping. The design depth of 3.5 feet is recommended for
Channel 1.
Table 6-3 Calculation Summary for Channel 1

Channel h
ft Freeboard
ft Design Depth
ft V
ft/sec
1 1.29 2 3.29 3.90
CDM used the UDFCD Drainage Criteria manual and calculated flow velocities to
determine the appropriate channel lining for Channels 1(UCFCD 2005). UDFCD
recommends flow velocity be less than 5 ft/sec for grass-lined channels and less than
12 ft/sec for riprap channels (UDFCD 2005). Based on UDFCD recommendations, a
Manrtng's n value of 0.003 was selected for design calculations, to check the capacity
of grass-lined channels. Based on these criteria, CDM recommends a grass-lined
channel for Channel 1 since the flow velocity is less than 5 ft/ sec.
• 6.4.2 Berm Design
CDM designed earth berms to capture surface water runoff from Basins 2 through 7.
Runoff in Basins 2 trough 5 will be captured by a berm along the crest of the WRA.
Runoff in Basins 6 and 7 will be captured and routed to proposed catchment basins
(refer to Exhibit E-1). The berms and catchment basins were designed to contain
runoff from the 100-year, 24-hour storm event. The point precipitation frequency
estimate for the 100-year, 24-hour storm, obtained from NOAA Atlas 14, Volume 1 for
Colorado (NOAA 1973) is 3.0 inches. CDM used the SCS runoff equation to estimate
runoff from the 3.0 inches of rainfall. The SCS runoff equation is:
_ P - 0.2SY
Q (P+0.8S)
where
Q = runoff (in)
P = rainfall (in)
S = potential maximum retention after runoff begins (in)
•
6-3
OA64988. Denison%Task Order 1 . Sunday Mines Drainage StudyAspoffinel Repor0final Sunday Mines Dratropa Repod_05=6.doc