Green Infrastructure Design for New NJDEP Stormwater Rules

New Green Stormwater InfrastructureRegulatory Training

April 23, 2020

Brian Friedlich, P.E.Project Manager, KleinfelderBFriedlich@Kleinfelder.com

609-924-8821

www.njawra.org

Impacts of Development on StormwaterWhat is Green InfrastructureRegulatory Drivers for Green InfrastructureNew NJDEP Stormwater RulesStormwater Planning StrategiesGreen Infrastructure BMPsGreen Infrastructure Examples

Overview of Presentation

The Urban Hydrologic Cycle

Figure taken from http://www.manukauwater.co.nz

Impacts of Development:

Increased runoffIncreased/frequent floodingReduced rechargeLower dry-weather flow in streamsIncreased pollutant loading

Impact of Development on Hydrology

What is Green Infrastructure?(GI)

NJDEP Definition of GI:Methods of stormwater management that reduce stormwater volume, flow, or characteristics by allowing the stormwater to:• infiltrate, • be treated by vegetation or by soils,• be stored for reuse.

Green infrastructure includes:• pervious paving• rain gardens• vegetated swales • cisterns• green roofs• vegetated filter strips

Conventional Stormwater Design

Figure taken from http://www.michiganlakeinfo.com

Green Infrastructure Stormwater Design

Figure taken from http://www.michiganlakeinfo.com

Conventional Approach LID/GI ApproachPeak Flow Reduction

Match Hydrograph

Hydrologic Design Approaches

Mimic Natural

Hydrology

Run

off F

low

Rat

e

Time

But Volume Increases

Improve our Environment and Communities:

• Community Engagement • Provide Green Communities• Address Flooding• Water Quality/CSO Reduction• Less reliance on potable water

(rain harvesting)

• Increased habitat for wildlife• Increased property values

Why Green Infrastructure in New Jersey?

To Meet Regulatory Requirements:• Stormwater Management Rules• NJPDES Non-Point Source Permitting• Municipal Stormwater Regulation

Program (MS4)• Total Maximum Daily Load (TMDL)• Combined Sewer Overflow (CSO)

Permitting

continued

Rule proposed to replace the current nonstructural strategies requirement with a requirement that green infrastructure be used to meet groundwater recharge, runoff quantity and runoff quality standards12/3/18 – NJAC 7:8 rule proposal published by NJDEP2/1/19 – NJDEP comment period ends3/2/20 – New rules published in NJ Register3/2/21 – Operative date of new rules

https://www.nj.gov/dep/rules/adoptions/adopt_20200302a.pdf

New Stormwater Rule Timeline

• Requiring use of green infrastructure to meet groundwater recharge, stormwater runoff quality, and stormwater runoff quantity requirements.

• Nonstructural strategies moved from design and performance standards to planning subchapters.

• New Green Infrastructure Standards• Change in definitions for “major development”, “regulated impervious

surfaces” and “regulated motor vehicle surfaces”.• Codifying BMP Manual into regulations. (New Draft Chapters are open

for comment) • Requirements for design and acceptance of alternative BMPs.• New/modified waiver, variance and mitigation requirements.• Clarifications for discharge into CSO systems and use of community

basins in CSO areas.

Major Stormwater Rule Changes

Tier 1 - Green Infrastructure BMP SummaryBest Management Practice

Stormwater Runoff QualityTSS removal rate (percent)

Stormwater Runoff

Quantity

Groundwater Recharge

Minimum separation from

seasonal high water table (feet)

Cistern 0 Yes No -

Dry Well 0 No Yes 2

Grass Swale 50 or less No No2

1

Green Roof 0 Yes No -

Manufactured Treatment Device (GI) 50 or 80 No No Dependent upon the

devicePervious Paving System 80 Yes

Yes (no underdrain)

No (w/ underdrain)

2

1Small- Scale Bioretention System 80 or 90 Yes

Yes (no underdrain)

No (w/ underdrain)

2

1Small-Scale Infiltration Basin 80 Yes Yes 2

Small-Scale Sand Filter 80 Yes Yes 2

Vegetative Filter Strip 60-80 No No -

Best Management Practice

Stormwater Runoff QualityTSS removal rate (percent)

Stormwater Runoff

Quantity

Groundwater Recharge

Minimum separation from

seasonal high water table (feet)

Bioretention System 80 or 90 YesYes (no underdrain)

No (w/ underdrain)

2

1

Infiltration Basin 80 Yes Yes 2

Sand Filter (w/o underdrain) 80 Yes Yes 2

Standard Constructed Wetland 90 Yes No N/A

Wet Pond (w/ native vegetation buffer and reuse component)

50-90 Yes No N/A

Tier 2 - Green Infrastructure BMPs for Quantity Only

*These BMPs may be used for groundwater recharge and runoff quality with a waiver or variance from GI standards

Best Management Practice

Stormwater Runoff QualityTSS removal rate (percent)

Stormwater Runoff

Quantity

Groundwater Recharge

Minimum separation from

seasonal high water table (feet)

Blue Roof 0 Yes No N/A

Extended Detention Basin 40-60 Yes No 1

Manufactured Treatment Device(non-GI)

50 or 80 No No Dependent upon the device

Sand Filter (w/ underdrain) 80 Yes No 1

Subsurface Gravel Wetland 90 No No 1

Wet Pond 50-90 Yes No N/A

Tier 3 - BMPs for Use with Variance or Waiver Only

*These BMPs may only be used with a waiver or variance from GI standards

Maximum Contributory Drainage Area

Best Management Practice Maximum Contributory Drainage Area

Dry Well 1 acre

Manufactured Treatment Device 2.5 acres

Pervious Paving SystemsArea of additional inflow cannot exceed three

times the area occupied by the BMP

Small-scale Bioretention Systems 2.5 acres

Small-scale Infiltration Basin 2.5 acres

Small-scale Sand Filter 2.5 acres

“Contributory drainage area” means the area from which stormwater runoff drains to a stormwater management measure, not including the area of the stormwater management measure itself

STORMWATER PLANNING

1ST Step in Stormwater Management is Planning

Stormwater Planning Tools and MethodsNonstructural Strategies/Low-Impact Development• Preservation of Wooded/Env. Sensitive Areas• Vegetative Conveyance• Disconnecting Impervious Surfaces

Green Infrastructure• Rain Gardens• Porous Pavement• Bioswales

Structural Best Management Strategies• Wet Ponds• Constructed Wetlands

Bioretention/Rain Gardens

Reference: NJ Stormwater BMP Manual

Pervious Paving Systems

Reference: http://www.icpi.org

Vegetative Filters and Swales

Reference: NJ Stormwater BMP Manual

Drywells and Cisterns

Photo Credit: Rutgers

Photo Credit: Earth Stone and Water/NJ Future Developers’ Guide

Green Roofs

http://dcgreenworks.org/programs/rainwater-conservation-and-reuse/green-roofs-2-0/

Photo Credit: The Watershed Institute

Photo Credit: Duke Farms

Sustainable Streets

Benefits include stormwater management, aesthetics, green streets (plantings), traffic calming, pedestrian accessibility.

Green Infrastructure for Residential

Legend:A – Low Density Residential1. Bioretention / Rain Garden2. Soil Amendments3. Bioretention / Rain Garden4. Grassed Swale5. Disconnectivity (Rain Barrel)6. Permeable Pavers7. Grassed Swale8. Bioretention / Rain Garden9. ConservationB – High Density Residential10. Conservation11. Permeable Pavers12. Disconnectivity (Rain Barrel)13. Disconnectivity (Dry Well)14. Minimizing Imperviousness (Reduced street width)

Figure taken from http://www.lid-stormwater.netSketch A was adapted from Prince George's County, MD, LID IMP Guidance Document, 2002.Sketch B was modified from Start at the Source as provided by Bay Area Stormwater Management Agencies Association and illustrator Patric Dawe.

Community Center – Montgomery Twp, NJ

Community Center – Montgomery Twp, NJ

Cambridge Water Department – Community Gardens and Rails to Trails Project

Post-Construction Photographs

QuestionsList of Resources:• NJDEP Amended Stormwater Rules -

https://njstormwater.org/pdf/N.J.A.C._7_8_Final_4.8.2020.pdf• Model Stormwater Ordinance for Municipalities -

https://www.nj.gov/dep/stormwater/bmp_manual/NJ_SWBMP_D.pdf• NJDEP BMP Manual - https://www.njstormwater.org/bmp_manual2.htm• NJ Future NJ Developers’ GI Guide - https://developersguide.njfuture.org/• NJ Future NJ GI Municipal Toolkit - https://gitoolkit.njfuture.org/• Rutgers GI Guidance Manual for NJ -

http://www.water.rutgers.edu/GreenInfrastructureGuidanceManual.html• NJDEP Stormwater Maintenance Guidance -

https://njstormwater.org/maintenance_guidance.htm• NJDEP Stormwater Training Literature - https://njstormwater.org/training.htm