SW3221007_Stormwater Report Revised Stage Storage_20230508

The stage storage relationship for the infiltration basin is calculated using
average end area values for the storage above the stone media. A porosity of
0.25 and 0.32 was used for sand and #57 clean stone, respectively to account for
volume within those media layers.
Table 11 — Infiltration Basin Stane Storane Table
Stage
V t)
Elevation
t)
Area
f t2
Porosity
Total Vol
ft3
!
0
813
1,057+
-
0
0.5
813.5
1,057+
0.25
132
1
814
1,057+
0.32
301
2
815
1,057+
0.32
639
3-
816-
1,057+
0.32
1,228
3+
816+
2,083
1
1,228
3.833.75
816.83 816.75
2,658 2,600
1
2,984A
4
817
2,906
1
3,672
5
818
4,331
1
7,291
6
819
6,182
1
12,547
+ Aprovided
n
Uprovided
2.6.2 Anti -floatation Calculations
977
977
2,945
3,417
7,036
12,292
The outlet structure is a 3 ft x 3 ft x 3.5 ft precast concrete box with 6 in side
and bottom wall thicknesses. Including concrete and reinforcing steel, the
structure has an empty mass of Moutletempty = 3,751 lb.
Assuming the total height of the box is exposed to buoyant forces, the volume of
water displaced by the box is calculated from the outside dimensions.
Vboxwater = 4.0 ft x 4.0 ft x 4.0 ft = 64 f t3
The buoyant force on the box is defined from the hydraulic forces acting
lb
Fb = VboxwaterPW = 64 f t3 x 62.4 ft3 = 3,994 lb
Additional mass was added to the outlet structure by pouring a 6 in concrete
slab over the bottom.
BREC, P.A. Dollar General - Store #24556
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