Tables: Bioretention Systems (Large-Scale)¶
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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, for systems designed to infiltrate into the subsoil |
| % | Stormwater Runoff Quality | Only with a waiver or variance from N.J.A.C. 7:8-5.3, 80 - 90% TSS Removal, Depending on Vegetation Selection and Depth of Soil Bed |
| Stormwater Runoff Quality Mechanisms and Corresponding Criteria | ||
| --- | --- | |
| Settling | ||
| Storage Volume | Entire Water Quality Design Storm Volume | |
| Vegetative Uptake and Filtration | ||
| Minimum Density of Vegetation | 85% | |
| Appropriate Species Selection | See Chapter 7: Landscaping | |
| Depth of Soil Bed | 1.5 - 2 feet, See Chapter 9.7: Small-scale Bioretention Systems | |
| 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 | |
| Soil Testing Consistent with Chapter 12: Soil Testing Criteria | Required |
Source context and notes
Source revision: January 2026. # 10.1 BIORETENTION SYSTEMS (LARGE-SCALE) [Figure: img-0.jpeg (original PDF, p. 1)](SOURCE.pdf#page=1) Bioretention systems are stormwater management facilities used to address the stormwater quality and quantity impacts of land development. The system consists of a soil bed planted with vegetation; it can be underdrained, or stormwater runoff can infiltrate into the subsoil. Pollutants are treated through the processes of settling and uptake and filtration by the vegetation. Pollutants are also treated within the soil bed through infiltration. The total suspended solids (TSS) removal rate is 80 - 90%; this rate will depend on the depth of the soil bed and the type of vegetation selected. | 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, for systems designed to infiltrate into the subsoil | | % | Stormwater Runoff Quality | Only with a waiver or variance from N.J.A.C. 7:8-5.3, 80 - 90% TSS Removal, Depending on Vegetation Selection and Depth of Soil Bed | | Stormwater Runoff Quality Mechanisms and Corresponding Criteria | | | --- | --- | | Settling | | | Storage Volume | Entire Water Quality Design Storm Volume | | Vegetative Uptake and Filtration | | | Minimum Density of Vegetation | 85% | | Appropriate Species Selection | See Chapter 7: Landscaping | | Depth of Soil Bed | 1.5 - 2 feet, See Chapter 9.7: Small-scale Bioretention Systems | | 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 | | Soil Testing Consistent with Chapter 12: Soil Testing Criteria | Required |2. Table 2¶
| Inflow Drainage Area | 120,000 sf of motor vehicle surface |
|---|---|
| Pavement NRCS Curve Number (CN) = | 98 |
| Soil Bed Depth = | 18 inches |
| Tested Permeability of Soil Bed = | 8 inches/hour |
| Tested Permeability of Subsoil = | 2 inches/hour |
| Depth to the Seasonal High Water Table = | 8 ft |
Source context and notes
Source revision: January 2026. # Designing a Bioretention System The following examples show how to design various bioretention systems to treat the runoff generated by the WQDS. The examples below are two of many possible ways to configure these systems and are not intended to limit the design. Example 1: For the existing two-lane curbed regulated motor vehicle surface illustrated below, design a bioretention basin to infiltrate the runoff generated by the WQDS. Runoff will enter the proposed system as flow piped from a new shallow catch basin situated along the curb line, and overflow will discharge to the existing stormwater collection system. The following parameters apply: | Inflow Drainage Area | 120,000 sf of motor vehicle surface | | --- | --- | | Pavement NRCS Curve Number (CN) = | 98 | | Soil Bed Depth = | 18 inches | | Tested Permeability of Soil Bed = | 8 inches/hour | | Tested Permeability of Subsoil = | 2 inches/hour | | Depth to the Seasonal High Water Table = | 8 ft | [Figure: img-10.jpeg (original PDF, p. 16)](SOURCE.pdf#page=16) ## Example 1 – Existing Conditions ## Step 1: Runoff Calculations3. Table 3¶
| Inflow Drainage Area = | 110,000 sf of motor vehicle surface |
|---|---|
| Pavement NRCS Curve Number (CN) = | 98 |
| Soil Bed Depth = | 18 inches |
| Assumed Design Permeability of Soil Bed = | 4 inches/hour |
| Water Quality Design Storm Depth = | 18 inches = 1.5 feet |
Source context and notes
# Bioretention Systems (Large-Scale) Source revision: January 2026. Example 2: For the existing uncurbed section of regulated motor vehicle surface illustrated below, design a bioretention swale with an underdrain to treat the runoff generated by the WQDS. Runoff will enter the proposed system as overland flow from the adjacent road surface. Additionally, a connection to the existing downstream stormwater collection system will be required in order to maintain safe travel conditions. The following parameters apply: | Inflow Drainage Area = | 110,000 sf of motor vehicle surface | | --- | --- | | Pavement NRCS Curve Number (CN) = | 98 | | Soil Bed Depth = | 18 inches | | Assumed Design Permeability of Soil Bed = | 4 inches/hour | | Water Quality Design Storm Depth = | 18 inches = 1.5 feet | [Figure: img-13.jpeg (original PDF, p. 19)](SOURCE.pdf#page=19) Example 2 – Existing Conditions ## Step 1: Runoff Calculations Using the NRCS method described in National Engineering Handbook, Part 630 (NEH) and discussed in Chapter 5, the volume of runoff produced by the WQDS was calculated to be 9,482 cf.Images on table pages¶
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