HomeMy WebLinkAboutWPO201400028 Calculations 2014-06-03 •
TEMPORARY SEDIMENT BASIN DESIGN DATA SHEET
(with or without an emergency spillway)
Project Pantops Corner
Basin#1 Location: Center of Site
Total area draining to basin: 5.07 acres
Basin Volume Design
Wet Storage:
1. Minimum required volume = 67 cu. yds. x Total Drainage Area(acres).
67 cu. yds. x 5.07 acres = 340 cu. yds.
2. Available basin volume= 352 cu. yds. at elevation 360
(From storage - elevation curve)
3. Excavate cu. yds. to obtain required volume*.
*Elevation corresponding to required volume = invert of the dewatering orifice.
4. Available volume before cleanout required.
33 cu. yds. x 5.07 acres= 167 cu. yds.
5. Elevation corresponding to cleanout level = 358.3
(From Storage - Elevation Curve)
6. Distance from invert of the dewatering orifice to cleanout level = 1.7 ft
(Min. = 1.0 ft.)
Dry Storage:
7. Minimum required volume = 67 cu. yds. x Total Drainage Area(acres).
67 cu. yds. x 5.07 acres = 340 cu. yds.
8. Total available basin volume at crest of riser* = 341 cu. yds. at
elevation 362.0 (From Storage - Elevation Curve)
* Minimum= 101 cu. yds./acre of total drainage area.
9. Diameter of dewatering orifice= 5 in.
10. Diameter of flexible tubing= 7 in. (diameter of dewatering orifice
plus 2 inches).
Preliminary Design Elevations
11. Crest of Riser = 355.5
Top of Dam = 364.0
Design High Water = 363.0
Upstream Toe of Dam = 354.0
Basin Shape
12. Length of Flow L =
Effective Width We 2.0
If> 2, baffles are not required
If<2, baffles are required
Runoff
13. Q2 = 13.1 cfs (From Chapter 5)
14. Q25 = 20.1 cfs (From Chapter 5)
Principal Spillway Design
15. With emergency spillway, required spillway capacity Qp = Q2 = 13.1
(riser and barrel)
Without emergency spillway, required spillway capacity Qp = Q25 = 20.1
(riser and barrel)
16. With emergency spillway:
Assumed available head(h) = 1 ft. (Using Q2)
h= Crest of Emergency Spillway Elevation - Crest of Riser Elevation
Without emergency spillway:
Assumed available head(h) = 0 ft. (Using Q25)
h=Design High Water Elevation- Crest of Riser Elevation
17. Riser Diameter(Dr) = 30 in. Actual head(h) = 0.7 ft
(From Plate 3.14-8.)
Note: Avoid orifice flow conditions.
18. Barrel length(1) = 62.4 ft.
Head (H) on barrel through embankment= 8.1 ft.
(From Plate 3.14-7).
19. Barrel diameter= 24 in.
(From Plate 3.14-B [concrete pipe] or Plate 3.14-A [corrugated pipe]).
20. Trash rack and anti-vortex device
Diameter= 54 inches
Height= 17 inches
(From Table 3.14-D).
Emergency Spillway Design
21. Required spillway capacity Q=Q25 - Qp = -3.0 cfs
22. Bottom width(b) = 8 ft.; the slope of the exit channel (s) _
3.9 ft./foot; and the minimum length of the exit channel (x) _
32 ft.
(From Table 3.14-C).
Anti-Seep Collar Design
23. Depth of water at principal spillway crest (Y) = 6.5 ft
Slope of upstream face of embankment(Z) = 2.5:1
Slope of principal spillway barrel (Sb) = 1.0%
Length of barrel in saturated zone (LS) = 41 ft
24. Number of collars required= 2 dimensions= 3.5 ft
(from Plate 3.14-12).
Final Design Elevations
25. Top of Dam = 364.0
Design High Water = 362.9
Emergency Spillway Crest = 363.0
Principal Spillway Crest = 362.0
Dewatering Orifice Invert = 360.0
Cleanout Elevation = 358.3
Elevation of Upstream Toe of Dam
or Excavated Bottom of"Wet Storage
Area" (if excavation was performed) = 354.0
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