Tables: Wet Ponds (Large-Scale GI)
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1. Table 1
BMP 2026, Ch 10.5, p. 1
| N.J.A.C. 7:8 Stormwater Management Rules – Applicable Design and Performance Standards |
|
|
|
Green Infrastructure |
Yes, provided the system is designed to maintain at least a 10-foot wide area of native vegetation along at least 50 percent of the shoreline and to include a stormwater runoff retention component designed to capture stormwater runoff for beneficial reuse. See Page 4. |
|
Stormwater Runoff Quantity |
When designed to receive runoff from all storm events as an on-line system |
| GR |
Groundwater Recharge |
Not Allowed |
| % |
Stormwater Runoff Quality |
Only with a waiver or variance from N.J.A.C. 7:8-5.3, 50% TSS removal with 1:1 pool volume ratio; up to 90% TSS removal if extended detention is also provided |
| Stormwater Runoff Quality Mechanisms and Corresponding Criteria |
|
|
| --- |
--- |
|
| Settling |
|
|
| Minimum Ratio of Permanent Pool Volume to WQ Design Storm Runoff Volume |
1:1 |
|
| 12 to 24-Hour Extended Detention |
Optional |
|
| Recommended Minimum Pool Length to Width Ratio |
3:1 |
|
| Presence of a Permanent Pool |
Required |
|
| Surface Area of Permanent Pool |
Minimum of 0.25 acre |
|
Source context and notes
# 10.5 WET PONDS (GI)
[Figure: img-0.jpeg (original PDF, p. 1)](SOURCE.pdf#page=1)
Wet ponds designed with a reuse component and a native vegetation perimeter are used to address the stormwater runoff quantity impacts of land development. This type of stormwater facility has an elevated outlet structure that creates a permanent pool where stormwater runoff is detained and attenuated. Wet ponds can be designed as multi-stage, multi-function systems; extended detention in the permanent pool provides pollutant treatment for runoff from the Water Quality Design Storm
through sedimentation and biological processing; detention and attenuation are also provided for larger storm event through the higher elevation outlets. When designed in accordance with this chapter, the total suspended solids (TSS) removal rate is 50 - 90%, depending upon the storage volume in the permanent pool and the duration of detention time, if extended detention is provided.
| N.J.A.C. 7:8 Stormwater Management Rules – Applicable Design and Performance Standards | | |
| --- | --- | --- |
| | Green Infrastructure | Yes, provided the system is designed to maintain at least a 10-foot wide area of native vegetation along at least 50 percent of the shoreline and to include a stormwater runoff retention component designed to capture stormwater runoff for beneficial reuse. See Page 4. |
| | Stormwater Runoff Quantity | When designed to receive runoff from all storm events as an on-line system |
| GR | Groundwater Recharge | Not Allowed |
| % | Stormwater Runoff Quality | Only with a waiver or variance from N.J.A.C. 7:8-5.3, 50% TSS removal with 1:1 pool volume ratio; up to 90% TSS removal if extended detention is also provided |
| Stormwater Runoff Quality Mechanisms and Corresponding Criteria | |
| --- | --- |
| Settling | |
| Minimum Ratio of Permanent Pool Volume to WQ Design Storm Runoff Volume | 1:1 |
| 12 to 24-Hour Extended Detention | Optional |
| Recommended Minimum Pool Length to Width Ratio | 3:1 |
| Presence of a Permanent Pool | Required |
| Surface Area of Permanent Pool | Minimum of 0.25 acre |
2. Table 2
BMP 2026, Ch 10.5, p. 11
| Design Number |
Permanent Pool Volume (ac-ft) |
WQ Runoff Volume |
Extended Detention Period |
|
|
Ratio of Permanent Pool to WQ Runoff |
% TSS Removal |
|
|
|
12 Hr |
18 Hr |
24 Hr |
|
|
| 1 |
1.246 |
1.246 |
- |
- |
- |
|
|
| 2 |
2.764 |
1.481 |
X |
- |
- |
|
|
| 3 |
0.704 |
0.058 |
- |
- |
X |
|
|
Source context and notes
[Figure: img-7.jpeg (original PDF, p. 11)](SOURCE.pdf#page=11)
TSS Removal Rates for GI Wet Ponds
The following example illustrates how to use the chart to determine the TSS removal rate provided:
Example: A number of GI wet pond designs are to be evaluated for TSS removal rates.
| Design Number | Permanent Pool Volume (ac-ft) | WQ Runoff Volume | Extended Detention Period | | | Ratio of Permanent Pool to WQ Runoff | % TSS Removal |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | | 12 Hr | 18 Hr | 24 Hr | | |
| 1 | 1.246 | 1.246 | - | - | - | | |
| 2 | 2.764 | 1.481 | X | - | - | | |
| 3 | 0.704 | 0.058 | - | - | X | | |
Step 1: For each row of the designs, determine the ratio of the Permanent Pool Volume to the volume of stormwater generated by the WQDS. The result is located in the column below the red arrow symbol.
| Design Number | Permanent Pool Volume (ac-ft) | WQ Runoff Volume | Extended Detention Period | | | Ratio of Permanent Pool to WQ Runoff | % TSS Removal |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | | 12 Hr | 18 Hr | 24 Hr | | |
| 1 | 1.246 | 1.246 | - | - | - | 1.0 | |
| 2 | 2.764 | 1.481 | X | - | - | 1.9 | |
| 3 | 0.704 | 0.058 | - | - | X | 12.1 | |
Step 2: For each of the designs, find the ratio along the x-axis and project a vertical line up towards the curves. If the ratio is greater than 3.0, use 3.0. Stop at the curve that matches the period of
3. Table 3
BMP 2026, Ch 10.5, p. 11
| Design Number |
Permanent Pool Volume (ac-ft) |
WQ Runoff Volume |
Extended Detention Period |
|
|
Ratio of Permanent Pool to WQ Runoff |
% TSS Removal |
|
|
|
12 Hr |
18 Hr |
24 Hr |
|
|
| 1 |
1.246 |
1.246 |
- |
- |
- |
1.0 |
|
| 2 |
2.764 |
1.481 |
X |
- |
- |
1.9 |
|
| 3 |
0.704 |
0.058 |
- |
- |
X |
12.1 |
|
Source context and notes
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | | 12 Hr | 18 Hr | 24 Hr | | |
| 1 | 1.246 | 1.246 | - | - | - | | |
| 2 | 2.764 | 1.481 | X | - | - | | |
| 3 | 0.704 | 0.058 | - | - | X | | |
Step 1: For each row of the designs, determine the ratio of the Permanent Pool Volume to the volume of stormwater generated by the WQDS. The result is located in the column below the red arrow symbol.
| Design Number | Permanent Pool Volume (ac-ft) | WQ Runoff Volume | Extended Detention Period | | | Ratio of Permanent Pool to WQ Runoff | % TSS Removal |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | | 12 Hr | 18 Hr | 24 Hr | | |
| 1 | 1.246 | 1.246 | - | - | - | 1.0 | |
| 2 | 2.764 | 1.481 | X | - | - | 1.9 | |
| 3 | 0.704 | 0.058 | - | - | X | 12.1 | |
Step 2: For each of the designs, find the ratio along the x-axis and project a vertical line up towards the curves. If the ratio is greater than 3.0, use 3.0. Stop at the curve that matches the period of
4. Table 4
BMP 2026, Ch 10.5, p. 13
| Design Number |
Permanent Pool Volume (ac-ft) |
WQ Runoff Volume |
Extended Detention Period |
|
|
Ratio of Permanent Pool to WQ Runoff |
% TSS Removal |
|
|
|
12 Hr |
18 Hr |
24 Hr |
|
|
| 1 |
1.246 |
1.246 |
- |
- |
- |
1.0 |
50% |
| 2 |
2.764 |
1.481 |
X |
- |
- |
1.9 |
79% |
| 3 |
0.704 |
0.058 |
- |
- |
X |
12.1 |
90% |
Source context and notes
# Wet Ponds (Large-Scale GI)
Source revision: January 2026.
| Design Number | Permanent Pool Volume (ac-ft) | WQ Runoff Volume | Extended Detention Period | | | Ratio of Permanent Pool to WQ Runoff | % TSS Removal |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | | 12 Hr | 18 Hr | 24 Hr | | |
| 1 | 1.246 | 1.246 | - | - | - | 1.0 | 50% |
| 2 | 2.764 | 1.481 | X | - | - | 1.9 | 79% |
| 3 | 0.704 | 0.058 | - | - | X | 12.1 | 90% |
# Considerations
A number of factors should be considered when utilizing a GI wet pond to treat stormwater runoff.
# Pretreatment
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