This is a test version, and I would appreciate any comments and bug reports.
This calculator implements the Temporary Sediment Basin (SD-3) sizing workflow from the Manual for Erosion and Sediment Control in Georgia and turns the Design Data Sheet into a repeatable, transparent set of computations.
Unlike “black box” tools, SD-3 depends heavily on table lookups and a few fixed criteria. The calculator keeps those steps visible by showing only the relevant window of each table and highlighting the exact cell(s) used for your design.
Temporary Sediment Basin (SD-3) Calculator
Sd3
Temporary Sediment Basin — full design sheet
Every step traced to the GSWCC manual, with the table cell used highlighted.
Project
Computed / checked names and the generation date are stamped on the PDF design sheet.
Hydrology & area
Basin geometry
Elevations, pipe & spillway
Elevation schedule (live)
Top of dam
DHW + freeboard
1,055.10
Design high water
E.S. crest + Hp
1,054.10
E.S. crest
riser crest + h
1,053.60
Riser crest
bottom + D
1,052.50
Clean-out mark
Vc on stage-storage
1,048.87
Basin bottom
base (input)
1,047.50
Basin sizing — auto
governs: surface area
Bottom W × L
56 × 132 ft
Wb = Wc − 2·Zu·D
Pool @ crest W × L
76 × 152 ft
L = 2W (Sd3 shape)
Storage depth D
5.0 ft
bottom → riser crest
Surface area @ crest
11,332 sf
≥ 11,326 required
Storage provided
1,721 cy
≥ 1,213 required
Bottom L : W
2.36 : 1
elongates below crest
Pick storage depth:
The “Balanced” option optimizes excavation depth versus footprint, while the “Smallest Footprint” option minimizes land take by allowing a deeper excavation.
Cross Section
Volume
1
Required storage volume Vs
Sd3 · Volume
67 cy/ac × drainage area1,212.7cy
× 2732,743cf
2
Clean-out volume Vc
Sd3 · Volume
22 cy/ac × drainage area (≈ ⅓ of Vs)398.2cy
3
Min. riser crest elevation
basin bottom + D1,052.50ft
4
Clean-out elevation
Vc on stage-storage curve1,048.87ft
height above bottom1.4ft
5
Riser length
riser crest − pipe invert at riser5.0ft
Runoff & surface area
6
Peak discharge Q2
2-yr, 24-hr storm (input)26.0cfs
7
Peak discharge Q25
25-yr, 24-hr storm (input)46.0cfs
8
Min. surface area
Sd3 · Surface Area
0.01 × Q2 (acres)0.260ac
× 43,56011,326sf
9
Available area at crest ≥ min?
provided 11,332 sf ≥ 11,326 sfYES
10
2:1 length-to-width (at crest)
Sd3 · Shape
76 × 152 ft → L = 2W2.0 : 1
Principal spillway
11
Max. capacity = Q2
principal sized for 2-yr storm26.0cfs
12
Head H (outlet ⟶ E.S. crest)
vertical distance6.10ft
13
Pipe length L
measured / auto46ft
min = [A − (B+C)/2]·(Zu+Zd) + T46ft
14
Pipe diameter Dps & flow
Table 6-29.1
from H and Q2Dps 24″, Q 27.0 cfs
Table 6-29.1 — pipe flow (cfs)
H \ Dps
12"
18"
24"
30"
36"
4
3.97
10.9
22.1
37.6
57.7
5
4.43
12.2
24.7
42.1
64.5
6
4.86
13.4
27
46.1
70.6
7
5.25
14.5
29.2
49.8
76.3
8
5.61
15.5
31.2
53.2
81.5
15
Actual flow Qps
Q × CF (CF=1.17)31.59cfs
16
Riser diameter Dr
≥ 1.5 × Dps36in
17
Trash rack diameter Dt
≥ 1.4 × Dr54in
18
Riser head h
Table 6-29.2
from Dr and Qps1.10ft
Table 6-29.2 — riser head: cell = Q (cfs) at head h for diameter Dr
h \ Dr
24"
30"
36"
48"
54"
0.8
13.9
17.4
20.9
27.9
31.4
1.0
19.5
24.3
29.2
39.0
43.8
1.2
25.6
32.0
38.4
51.2
57.6
1.4
–
40.3
48.4
64.5
72.6
1.6
–
49.3
59.1
78.8
88.7
19
Concrete per vert. ft
Table 6-29.3
anti-flotation, by Dr6.18cf/vf
Table 6-29.3 — anti-flotation concrete (cf per vertical ft)