Tables: Infiltration Basins (Large-Scale GI)¶
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1. Table 1¶
| N.J.A.C. 7:8 Stormwater Management Rules – Applicable Design and Performance Standards | ||
|---|---|---|
| Green Infrastructure | Yes | |
| Stormwater Runoff Quantity | Yes, when designed as an on-line system | |
| GR | Groundwater Recharge | Only with a waiver or variance from N.J.A.C. 7:8-5.3 |
| % | Stormwater Runoff Quality | Only with a waiver or variance from N.J.A.C. 7:8-5.3, 80% TSS Removal |
| Stormwater Runoff Quality Mechanisms and Corresponding Criteria | ||
| --- | --- | |
| Settling | ||
| Storage Volume | Entire Water Quality Design Storm (WQDS) Volume | |
| Infiltration | ||
| Maximum Design Storm Drain Time | 72 hours, Using Slowest Design Permeability Rate | |
| Permeability Rate Factor of Safety | 2 | |
| Minimum Subsoil Design Permeability Rate | 0.5 inches/hour | |
| Maximum Design Permeability Rate | 10 inches/hour | |
| Soil Testing Consistent with Chapter 12: Soil Testing Criteria | Required | |
| Minimum Distance between Basin Bottom and Seasonal High Water Table | 2 feet | |
| Biological and Chemical Activity | ||
| Minimum Sand Layer Thickness | 6 inches | |
| Minimum Sand Layer Permeability Rate | 20 inches/hour, tested per Chapter 12 | |
| Maximum % Fines in Sand Layer | 15% |
Source context and notes
Source revision: March 2021. # 10.2 INFILTRATION BASINS (LARGE-SCALE) [Figure: img-0.jpeg (original PDF, p. 1)](SOURCE.pdf#page=1) Infiltration basins are stormwater management systems constructed with highly permeable components designed to both maximize the removal of pollutants from stormwater, promote groundwater recharge and address the quantity impacts of land development. Pollutants are treated through settling, filtration of the runoff through, and biological and chemical activity within, the components. The total suspended solids (TSS) removal rate is 80%. | N.J.A.C. 7:8 Stormwater Management Rules – Applicable Design and Performance Standards | | | | --- | --- | --- | | | Green Infrastructure | Yes | | | Stormwater Runoff Quantity | Yes, when designed as an on-line system | | GR | Groundwater Recharge | Only with a waiver or variance from N.J.A.C. 7:8-5.3 | | % | Stormwater Runoff Quality | Only with a waiver or variance from N.J.A.C. 7:8-5.3, 80% TSS Removal | | Stormwater Runoff Quality Mechanisms and Corresponding Criteria | | | --- | --- | | Settling | | | Storage Volume | Entire Water Quality Design Storm (WQDS) Volume | | Infiltration | | | Maximum Design Storm Drain Time | 72 hours, Using Slowest Design Permeability Rate | | Permeability Rate Factor of Safety | 2 | | Minimum Subsoil Design Permeability Rate | 0.5 inches/hour | | Maximum Design Permeability Rate | 10 inches/hour | | Soil Testing Consistent with Chapter 12: Soil Testing Criteria | Required | | Minimum Distance between Basin Bottom and Seasonal High Water Table | 2 feet | | Biological and Chemical Activity | | | Minimum Sand Layer Thickness | 6 inches | | Minimum Sand Layer Permeability Rate | 20 inches/hour, tested per Chapter 12 | | Maximum % Fines in Sand Layer | 15% |2. Table 2¶
| Inflow Drainage Area = | 5 acre (motor vehicle surface) |
|---|---|
| Pavement NRCS Curve Number (CN) = | 98 |
| Tested Sand Permeability Rate = | 40 inches/hour |
| Tested Subsoil Permeability Rate = | 8 inches/hour |
| Maximum Design Storm Water Depth = | 2 ft |
| Sand Layer Depth = | 6 in |
Source context and notes
Source revision: March 2021. # Designing an Infiltration Basin The following examples show how to design various infiltration basins to treat the runoff generated by the WQDS. The examples below are two of many possible ways to configure these basins and are not intended to limit the design. Example 1 - Surface Infiltration Basin: For one acre of impervious pavement, design an infiltration basin to infiltrate the runoff generated by the WQDS. Runoff will receive pretreatment by a forebay designed in accordance with the criteria established in this chapter. Runoff volumes in excess of the WQDS generated volume will discharge via an emergency spillway. The following parameters apply: | Inflow Drainage Area = | 5 acre (motor vehicle surface) | | --- | --- | | Pavement NRCS Curve Number (CN) = | 98 | | Tested Sand Permeability Rate = | 40 inches/hour | | Tested Subsoil Permeability Rate = | 8 inches/hour | | Maximum Design Storm Water Depth = | 2 ft | | Sand Layer Depth = | 6 in | ## Step 1: Runoff Calculations Using the NRCS method described in National Engineering Handbook, Part 630 (NEH) and discussed in Chapter 5, the runoff volume for the WQDS was calculated to be 18,777 cf. ## Step 2: Forebay SizingImages on table pages¶
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