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Deciding Which BMPs are Right for Your Project

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Each project has its own specific stormwater needs and constraints and each Green Infrastructure Best Management Practice has unique benefits and functions. Click through the Decision-Making Tree to choose the best BMPs for your site. The new amendments to N.J.A.C. 7:8 place much greater emphasis on distributed green infrastructure. Design professionals will consult Tables 5-1 and 5-2 to determine which BMPs may be used to meet standards for runoff quality, groundwater recharge, and runoff quantity. Table 5-3 shows options available with a waiver or variance. This tool illustrates design options available without variances or waivers.

What’s a “major development”?
As of March 2021, “major development” means (a) an individual development or multiple developments that, individually or collectively, result in the disturbance of one or more acres of land since Feb. 2, 2004; or (b) the creation of one-quarter acre or more of “regulated impervious surface” since Feb. 2004; or (c) the creation of one-quarter acre or more of “regulated motor vehicle surface” since March 2021; or a combination of new regulated impervious surface or motor vehicle surface (b) and (c) above that totals one-quarter acre or more.

The Decision Making Tree can be used to help choose the best BMPs for your site. See below to navigate through decision steps.

None of these work for your project? You may be able to get a variance. See N.J.A.C. 7:8 4.6 or 5.2(e). See Addressing Challenges. Solving Problems

Dry Well

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A dry well is a subsurface stormwater facility consisting of either a structural chamber or stone filled excavation that is used to collect and temporarily store stormwater runoff from rooftops. The dry well inflow is connected by roof leaders. The sides and top of the dry well are completely lined with filter fabric to avoid fines clogging the system.

Cistern

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Cisterns are storage tanks designed to capture and store stormwater for non-potable uses such as irrigation, toilet flushing, or industrial processes. Stormwater runoff is typically carried from roof areas to cisterns through roof gutters, downspouts, drains, and/or pipes. Screens on gutters and downspouts filter large sediment and debris from stormwater runoff before it enters the rain barrel or cistern.

Green Roof

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A green roof is a system of lightweight soil and plants. The plants absorb some of the rain that falls on the roof, and any excess is stored in a soil layer below. Layers of soil and plants are as thin as just a few inches or as thick as several feet depending on the structural capacity of the roof and the types of plants that are specified. Roofs with a thin soil layer are lighter and easier to install, and are usually planted with succulents that need minimal water and nutrients to survive. Green roofs with thicker soil profiles can support a greater variety of plants, including trees and shrubs, but are more expensive.

Pervious Paving System

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Pervious pavement is a surface that allows water to infiltrate into the ground below. Pervious pavement materials can include asphalt, concrete, interlocking concrete pavers, gravel, and resin-bonded materials such as recycled rubber, mulch, and glass. These surface courses are installed over a supporting base of crushed stone that helps to store and infiltrate stormwater.

Pervious pavements can offer a simple means of integrating green infrastructure if your development footprint is tightly constrained.

Small-Scale Bioretention System

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Bioretention systems are vegetated depressions in the landscape designed to infiltrate stormwater into the subsoil, and/or hold it for a period of time to settle out pollutants and allow some uptake by plants. Bioretention basins can be sited in a wide range of different locations and settings. The terms “rain gardens” and “stormwater bumpouts” are often synonymous with bioretention systems. By co-locating stormwater management with visually appealing landscaped areas, designers can maximize the remaining area available for building.

Small-Scale Infiltration Basin

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An infiltration basin captures stormwater and infiltrates it into the ground through highly permeable soil media designed to remove pollutants and promote groundwater recharge. The soils in these systems treat pollutants via settling, filtration, and biochemical activity.

Like bioretention systems and sand filters, infiltration basins are more effective at providing water quality treatment and groundwater recharge for small drainage areas. For large drainage areas, a waiver is required to use an infiltration basin for water quality and/or groundwater recharge.

Small-Scale Sand Filter

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A sand filter is a depression in the ground used to capture, infiltrate, and filter pollutants before discharging. Sand filters are similar to infiltration basins in design. The primary difference is that sand filters can have vegetative cover and are less aesthetically obtrusive. Sand filters can be constructed with or without underdrains.

Like bioretention systems and infiltration basins, sand filters are more effective at providing water quality treatment and groundwater recharge for small drainage areas. The NJDEP requires a variance for sand filters with large drainage areas to count for water quality and groundwater recharge.

Wet Pond

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A wet pond is a permanent pool where stormwater is captured and regulated by an elevated outlet structure. Native vegetation should be used to provide a permanent buffer around the pool. Water from the pond should be used for irrigation or some other beneficial use.

Wet ponds are used to accommodate runoff and provide stability from larger design storms. They can also be used when wildlife habitats, recreational benefits, or water supply for irrigation or fire protection need to be enhanced. Wet ponds may look similar to constructed wetlands, but their plantings, soil, and subsurface systems are very different.

Standard Constructed Wetland

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A constructed wetland is an engineered wetland system that can be used to reduce peak flows and meet water quantity regulations. Constructed wetlands have the added benefit of removing a wide variety of pollutants through settling and vegetative filtering, providing wildlife habitat, and adding aesthetic value to a site.

Bioretention System

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Bioretention systems are vegetated depressions in the landscape designed to infiltrate stormwater into the subsoil, and/or hold it for a period of time to settle out pollutants and allow some uptake by plants. Bioretention basins can be sited in a wide range of different locations and settings. The terms “rain gardens” and “stormwater bumpouts” are often synonymous with bioretention systems. By co-locating stormwater management with visually appealing landscaped areas, designers can maximize the remaining area available for building.

Infiltration System

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An infiltration basin captures stormwater and infiltrates it into the ground through highly permeable soil media designed to remove pollutants and promote groundwater recharge. The soils in these systems treat pollutants via settling, filtration, and biochemical activity.

Like bioretention systems and sand filters, infiltration basins are more effective at providing water quality treatment and groundwater recharge for small drainage areas. For large drainage areas, a waiver is required to use an infiltration basin for water quality and/or groundwater recharge.

Sand Filter

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A sand filter is a depression in the ground used to capture, infiltrate, and filter pollutants before discharging. Sand filters are similar to infiltration basins in design. The primary difference is that Sand filters can have vegetative cover and are less aesthetically obtrusive. Sand filters can be constructed with or without underdrains.

Like bioretention systems and infiltration basins, sand filters are more effective at providing water quality treatment and groundwater recharge for small drainage areas. The NJDEP requires a variance for sand filters with large drainage areas to count for water quality and groundwater recharge.

Grass Swale

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A grass swale is a long, narrow grassy channel used to convey stormwater to a downstream green infrastructure practice or storm drain. Grass is typically kept to a height of about three to six inches to slow down the runoff and allow any debris or sediment to settle out without interfering with the direction of flow. Depending on site conditions, additional features such as check dams and underdrains may be required to comply with New Jersey Soil Erosion and Sediment Control Standards.

Vegetative Filter Strip

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A vegetative filter strip is a gently sloping landscaped area that provides pretreatment to an adjacent stormwater management facility. The BMP slows the upstream runoff rate, reducing the risk of erosion and allows for quicker infiltration before the water leaves the site. Vegetative filter strips add visual buffer from impervious areas such as parking lots.

Manufactured Treatment Device

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A manufactured treatment device (MTD) is a structural alternative to treating water quality on a site. This approach to treatment can be used when space is limited. MTDs are designed to remove chemical contaminants and sediment from runoff through filtration, vortex separation, and/or other technologies.

The Developers Green Infrastructure Guide 2.0 breaks down New Jersey’s Stormwater Rule amendments and helps developers and decision-makers understand more clearly green infrastructure options and advantages, compare alternatives, evaluate costs and benefits.

The Developers Green Infrastructure Guide 2.0 is brought to you by the Developers Green Infrastructure Task Force, a partnership between New Jersey Future and the New Jersey Builders Association.

The Task Force gratefully acknowledges the financial support of the William Penn Foundation, which made this project possible.

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