HomeMy WebLinkAboutWPO202200038 Calculations 2022-09-14 (20)1992
TEMPORARY SEDIMENT BASIN DESIGN DATA SHEET
(with or without an emergency spillway)
Project Breezy Hill
Basin # 1 Location
Total area draining to basin: 13.8 acres.
Basin Volume Desien
Wet Storage:
3.14
1. Minimum required volume = 67 cu. yds. x Total Drainage Area (acres).
67 cu. yds. x 13.8 acres = 925 cu. yds.
2. Available basin volume = 925 cu. yds. at elevation 374.98 . (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 13.8 acres = 455 cu. yds.
5. Elevation corresponding to cleanout level = 372.99
(From Storage - Elevation Curve)
6. Distance from invert of the dewatering orifice to cleanout level = 1.99 ft.
(Min. = 1.0 ft.)
Dry Storage:
7. Minimum required volume = 67 cu. yds. x Total Drainage Area (acres).
67 cu. yds. x 13.8 acres = 925 cu. yds.
1992 3.14
8. Total available basin volume at crest of riser* = 1,849 cu. yds. at
elevation 377.86 . (From Storage - Elevation Curve)
* Minimum = 134 cu. yds./acre of total drainage area.
9. Diameter of dewatering orifice = 6 in.
10. Diameter of flexible tubing = 8 in. (diameter of dewatering orifice
plus 2 inches).
Preliminary Design Elevations,
11. Crest of Riser = 377.86
Top of Dam = 380
Design High Water =
Upstream Toe of Dam =
Basin Shane
378.17
370
12. Length of Flow L =
Effective Width We
If > 2, baffles are not required
If < 2, baffles are required _
Runoff
13. Q2 = 19.37 cfs (From Chapter 5)
14. Q25 = 31.06 cfs (From Chapter 5)
Principal SDillwav Design
15. With emergency spillway, required spillway capacity QP = Q2 = 19.37 cfs.
(riser and barrel)
Without emergency spillway, required spillway capacity QP = Q25 = cfs.
(riser and barrel)
1992 3.14
16. With emergency spillway:
Assumed available head (h) = 1.14 ft. (Using QZ)
It = Crest of Emergency Spillway Elevation - Crest of Riser Elevation
Without emergency spillway:
Assumed available head (h) = ft. (Using Q25)
h = Design High Water Elevation - Crest of Riser Elevation
17. Riser diameter (Dr) = 60 in. Actual head (h) = 1.14 ft.
(From Plate 3.14-8.)
Note: Avoid orifice flow conditions.
18. Barrel length (1) = 44 ft.
Head (H) on barrel through embankment = 9 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 = 90 inches.
Height = 29 inches.
(From Table 3.14-D).
Emergencv SDillwav Design
21. Required spillway capacity Qe = Qu - Qp = 11.69 cfs.
22. Bottom width (b) = 12 ft.; the slope of the exit channel (s) _
3 ft./foot; and the minimum length of the exit channel (x) _
51 ft.
(From Table 3.14-C).
1992 3.14
Anti -Seep Collar Design
23. Depth of water at principal spillway crest (Y) _ _ ft.
Slope of upstream face of embankment (Z) _ :1.
Slope of principal spillway barrel (Sb) _ %
Length of barrel in saturated zone (LS) = ft.
24. Number of collars required = dimensions =
(from Plate 3.14-12).
Final Design Elevations
25. Top of Dam = 380
Design High Water = 378.17
Emergency Spillway Crest = 379
Principal Spillway Crest = 377.86
Dewatering Orifice Invert = 374.98
Cleanout Elevation = 372.99
Elevation of Upstream Toe of Dam
or Excavated Bottom of "Wet Storage
Area" (if excavation was performed) = 370