2014-04-22_REPORT - M1990057

• Permit No: M1990057
• IBM Index Class Name: REPORT
• Doc Date: 4/22/2014
• Doc Name: Drainage report
• From: Union Milling Company, LLC
• To: DRMS
• Email Name: TC1
• Media Type: D
• Archive: No

Flatirons, Inc. - Surveying & Engineering
designed and evaluated for capacity and stability conditions. The channel capacity is
defined by the 100 -year, 24 -hour storm. The minimum required freeboard is 0.5 feet, or
one half the velocity head, whichever is greater. This means that whenever the velocity
head is greater than 1.0 feet, the open channel freeboard will be defined by the velocity
head. Likewise, whenever the velocity head is less than 1.0 feet, the open channel
freeboard is 0.5 feet.
Freeboard in the contact channels (berm, West TSF, and East TSF) is 0.5 feet. Freeboard
in the diversion channels (Upper and East) and the TSF Spillway channel is also 0.5 feet.
The freeboard for the Upper and East diversion channels is 0.6 feet and 0.7 feet,
respectively. The freeboard for the TSF Spillway channel is 0.8 feet.
Riprap will be installed in open channels having velocities greater than 5.0 feet per second.
A non -woven geotextile fabric will be placed under the riprap and secured by anchor
trenches. 10 -inch riprap (d50) will be installed in all ditches requiring a riprap lining in
addition to the TSF Spillway Chute channel.
Open channel calculation sheets and a riprap calculation sheet can be found in Appendix B.
Open Channel Summary
Description
Ditch
Depth*
(ft)
Design
Peak Q100
(cfs)
Max. Water
Depth **
(ft)
Max.
Velocity * **
(fps)
Velocity
Head * **
(ft)
Upper Diversion
2.0
10.4
1.4
6.5
0.6
East Diversion
2.0
15.3
1.3
5.5
0.5
Berm Contact
1.0
0.6
0`4
4.8
0.4
West TSF Contact
1.0
0.4
0.3
4.3
0.3
South TSF Contact
2.0
0.8
0.4
1.9
0.6
TSF Spillway
Channel
2.0
11.4
1.2
4.7
0.3
TSF Spillway
Chute
1.0
11.4
0.1
4.7
0.3
Table 3
*See Map D2 titled Drainage Details for section detail in back pocket of report.
** Based on design channel with a manning's n of 0.045 and the minimum channel slope.
** *Based on design channel with a manning's n of 0.018 for the maximum earth -lined
channel slope, or a manning's n of 0.035 for maximum riprap -lined slope.
Union Mill 12 March 5, 2014