2018-08-08_PERMIT FILE - C1982056 ‎(17)‎

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 8/8/2018
• Section_Exhibit Name: EXHIBIT 08 TAB 1 SEDIMENT CONTROL PLAN
• Media Type: D
• Archive: No

Table 2
SEDIMENTATION POND E DESIGN CALCUALTIONS
(Continued)
SPILLWAY DESIGN SUMMARY:
- Depth of flow is 0.5 ft.
- Velocity of flow is 5.2 fps
- Bottom of spillway is 1.5 ft below top of dam
- Width of spillway is 13.2 ft across bottom
- Side slopes are lv: 2h
- Gradient of spillway is 3%
EMERGENCY SPILLWAY CALCULATIONS:
Broad -crested Spillway Design:
(Applied Hydrology and Sedimentology for Disturbed Areas: Barfield,
Warner, Haan: 1981)
Q = 26.3 cfs
Maximum velocity 5.2 fps
2v:lh sideslopes
n = 0.04
Slope = 0.03 ft/ft
Hec = 0.75 Fig 4B.14
Hp = 0.86 Fig 4B.1
Q' = 0.544(g) 1(Hec)3/2b
Q' = 0.544 (32.2)1(0.75)3/2(100) = 201
Q = 26.3 = Q'(1.5b + 2 Hec)/150
b = 13.2'
Q = 201 (1.5b + 2(0.75))/150
Thus, Q of 26.3 is less than Q of 28.5, and spillway is adequately designed.
Spillway is 13.2 ft. width across the bottom. Depth of spillway is 1.5 ft.
minimum. Will need to riprap emergency spillway.
*NOTE: Although required sediment storage is .58 rather than original
determination of .64, the dewatering orifice will remain at the relative
elevation of 51.8 feet.
- 8-10 - Revised 10/11/88