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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
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