stormwater.mang.2004.pg15 DRYWELL PERFORMANCE FOR STORMWATER INFILTRATION
This Spreadsheet calculates storage volumes and infiltration rates for drywells in stornowaler service. The user must input the parameters on the left of the
sheet and verify that the lower table covers the entire depth of the installed drywell system. If the entire depth is not covered.the user most input values of
ELEV up to the top of the system and copy the remainder of the cells for additional ELEV values input. The user most also manually correct the DR1AkTLL
VOLUN E column for elevations above the top of drywell.
The calculations are based upon the following assumtions:
1) The excavation for the drywell installation is conical at a 1 on 1 slope and completely back-filled with stone of void ratio as input by user.
2) The bottom of the excavation is level and the diameter as indicated.
3) The bottom of the excavation is taken as ELEV-0.
4) Infiltration occurs over the sidewall area only.
5) Infiltration rate is calculated from actual inflow rate(CFEUSF)from the percolation test and user defined factor of safety. A standard 12"diameter by 6"
deep percolation test has been utilized for inflow,rate calculation.
6) A factor of 0.95 has been included within DRYWELL V OLL4vIE.calculation to account for volume of the structure.
USER INPUT PARAMETERS CALCULATED PARAMETERS
PROJECT: CLUTE SELF STORAGE-4-8' DIA. X 8' DEEP DRYWELLS
DRYWELL DIAMETER = 8 FT EXCAVATION BASE RAD= 5 FT
DRYWELL DEPTH = 8 FT ALL CONE DEPTH = 14.5 FT
STONE UNDER DRYWELL= 1 FT ALL CONE RADIUS(1 ON 1) = 14.5 FT
STONE POROSITY= 0.4 ALL CONE VOLUME= 3192.5 CF
SOILS PERCOLATION RATE= 0.5 MIN/INCH BOTT CONE VOLUME = 130.9 CF
F.S. ON INFILTRATION = 2 BOTT CONE SW AREA= 111.1 SF
HYDRAULIC HEAD FACTOR = 1.15 /FT INFIL RATE FROM PERC = 3.360 CF/SF'HR
##DRYWELLS/ SYSTEM = 4 INFIL RATE WITH F.S. = 1.680 CF/SF'HR
EXCAVATION BASE DIA= 10 FT
TOTAL SYSTEM DEPTH = 9.5
CF SF SF CF CF/DW CFH/SF PER DRYWELL PER SYSTEM
FT FT EXCVTN EXCVTN BOTTOM DW TOTAL INFIL CFH CFS CF CFS
ELEV TOP RAID VOLUME SW AREA AREA VOLUME STORAGE RATE INFILTRATION STORAGE INFIL
0 5 0.0 0 78.5 0 0 0 0 0 0 0
1 6 95.3 48.9 0.0 38.1 1.680 82.1 0.02 152 0.09
2 7 228.3 106.6 47.8 120.0 1.932 206.0 0.06 480 0.23
3 8 405.3 173.3 95.5 219.4 2.222 385.0 0.11 878 043
4 9 632.5 248.8 143.3 339.0 2.555 635.7 0.18 1356 0.71
5 10 916.3 333.2 191.0 481 A 2.938 979.1 0.27 1924 1 09
6 11 1262.9 426.5 238.8 648.4 3.379 1441.2 0.40 2594 1.60
7 12 1678.7 528.7 286.5 843.4 3.886 2054.5 0.57 3373 2.28
8 13 2169.8 639.8 334.3 1068.5 4.469 2859.0 0.79 4274 3.18
9 14 2742.E 759.7 382.0 1326.3 5A39 3904.4 1.08 5305 434