Spreadsheet: 2128d001-83e4-4dcb-88d0-1a337a0ecf0c
Sheet: Wet Ponds_Wetlands

WET POND/WETLAND CALCULATOR
This calculator sizes the components of a wet pond or wetland such that it treats the Water Quality Volume (WQv).
CALCULATOR
Wet Ponds and Wetlands Calculator - by Water Quality Volume
1 | Water Quality Volume - WQv |  |  | [NAME]
2 | [NAME] volume calculator (min size) |  |  | [NAME]
3 | Wet Pond or Wetland
4 | Permanent pool volume calculator |  |  | [NAME]
5 | Live storage volume calculator |  |  | [NAME]
6 | Dimensions Calculator
7 | Permanent Pool Depth |  |  | feet (typically 1.5 to 2 feet average depth for wetlands, 4 to 6 feet for wet pond)
8 | Live Storage Volume Depth |  |  | feet (typically 1 to 2 feet for wetlands, 1 to 3 feet for wet pond)
9 | Total Depth at WQv - d |  |  | feet
10 | Basin Length to [NAME] (L/W) |  |  | generally between 2 and 4
11 | Basin Side Slope |  |  | feet/feet (ratio of horizontal to vertical, for example, 3 for 3H:1V)
12 | [NAME] of Basin Bottom |  |  | feet
13 | Length of Basin Bottom |  |  | feet
14 | [NAME] of Basin at Permanent Pool Depth |  |  | feet
 | Length of Basin at Permanent Pool Depth |  |  | feet
 | [NAME] of Basin at WQv Depth |  |  | feet
 | Length of Basin at WQv Depth |  |  | feet
15 | Permanent Pool Volume |  |  | [NAME] (must be greater than 2x WQv for wet ponds, greater than 1x for wetlands)
 | Live Storage Volume |  |  | [NAME] (must be greater than WQv)
16 | Check of Permanent Pool Volume
 | Check of Live Storage Volume
17 | Drain time for WQv - t | 48 |  | hours (between 24-28, recommend 48 hours)
 | Surface Area at Mid Elevation |  |  | square feet
 | Orifice Area |  |  | square feet
18 | Approx. Orifice Diameter for Drain Time |  |  | inches (refine outlet control sizing and configuration during design)
19 | Flow Rate thru Orifice |  |  | gpm (flow rate when basin is at WQv depth)
 | Est. Impervious DMA |  |  | ft2
 | Sizing Ratio (BMP/DMA)
 | DP + Forebay
INSTRUCTIONS
Follow the steps below to determine the required size of your wet pond/wetland.
Step
1 | Enter the Water Quality Volume (WQv) for the DMA. The WQv is calculated in Step 14 of the Water Quality Volume and Water Quality Flow Rate Calculator.
2 | The required volume for the forebay is shown here (typically 10 to 25% of the WQv).
3 | Select whether you are designing a wet pond or wetland.
4 | The required permanent pool volume is calculated here. The permanent pool should be equal to the WQv for wetlands and two times the WQv for wet ponds.
5 | The required live storage volume is calculated here. This is typically equal to the WQv.
6 | Use the following steps of the Dimensions Calculator to determine the basin configuration.
7 | Enter the depth of the permanent pool. Wetlands include shallower areas (0 to 18 inch depth) for increased plant growth as well as deeper micropools (up to 4 feet depth). Enter the average depth of the wetlands' permanent pool. There is typically a 1.5 to 2 feet average depth for wetlands, 4 to 6 feet for wet ponds.
8 | Enter the live storage depth (i.e., the water depth above the permanent pool used to captured the WQv event). [NAME] are typically 1 to 2 feet for wetlands and 1 to 3 feet for wet ponds. This depth DOES NOT include freeboard, which is typically 1 foot above the maximum design depth (freeboard should be added in actual design).
9 | The total depth of the basin at the WQv level is calculated here.
10 | Enter the length to width ratio of the basin.  A ratio between 2 and 4 is recommended.
11 | Enter the side slope of the basin. The slope of earthen side walls should be no steeper than 3:1 (i.e., at least 3 feet horizontal for each 1 foot vertical). Enter 0 for vertical hardscaped sidewalls.
12 | Enter the width of the pond bottom at the invert of the basin.
13 | The length of the basin bottom is calculated here.
14 | The width and length of the basin at the permanent pool depth and at the design water depth (i.e., [NAME]) are calculated here.
15 | The basin's permanent pool volume and the live storage volume are calculated here. Adjust the basin width and/or depth until the volumes are greater than or equal to the permanent pool volume and WQv calculated in Steps 4 and 5.
16 | This step checks that the permanent pool and live storage volumes meet the required volumes calculated in Steps 4 and 5. If either volume is less than required, increase the basin width (Step 12) or depths (Steps 7 and 8).
17 | The WQv design drain time is entered here.  The time should be between 24 and 48 hours, with 48 hours being recommended.
18 | The diameter of the orifice needed to drain the WQv in the design drain time is shown here. This planning level estimate of the required outlet control should be revised during design. The minimum allowable orifice size is 1-inch diameter.
19 | The step calculates the estimated flow rate through the orifice when the water level is at the WQv depth.
DEFINITIONS
 | Water Quality Volume (WQv) | The runoff volume to be managed by the stormwater BMP such that treatment requirements are met. The WQv is calculated by the Water Quality Volume and Water Quality Flow Rate Calculator.
 | Live Storage Volume | The temporary ponding area above the permanent pool that stores the WQv volume.
 | Permanent Pool Volume | The volume of water that is permanently in the wet pond/wetland.
 | Forebay Volume | A sediment forebay should be used to isolate gross sediments as they enter the facility and to simplify sediment removal.
 | Permanent Pool Depth | The depth from the invert of the basin to the top of the permanent pool water level. This depth may vary in wetlands; for the purposes of the planning level calculations, the average permanent pool depth can be entered here.
 | Live Storage Volume Depth | Depth from the top of the permanent pool to the top of the live storage area.
 | Depth at WQv (d) | The depth of the basin from the top of the live storage volume to the invert of the basin. Does not include freeboard.
 | Freeboard | The vertical distance between the maximum design water depth and the top of the basin embankments.
 | Orifice | An orifice is a flow restrictor. It drains the pond slowly to improve water treatment through settling of pollutants.
 | Drain Time (t) | The time for the storage area to drain the water quality volume.