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They provided guidance on NJDEP's new stormwater ordinances, a summary of requirements, and recommendations for developing and implementing stronger ordinances. Co-sponsored by the American Littoral Society, Association of New Jersey Environmental Commissions, and Pinelands Preservation Alliance, the webinar was attended by officials, planning board members, municipal professionals (engineers and planners), attorneys and Environmental Commission members from all across the state. In March 2020, NJ Department of Environmental Protection (NJDEP) published revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which states that, in order to meet stormwater management performance criteria set forth by NJDEP, New Jersey municipalities are required to update their stormwater control ordinances to incorporate green infrastructure. Check out our blog detailing the updated requirements. NJDEP periodically updates the stormwater rules and provides municipalities with a deadline to incorporate the rule changes in order to stay in compliance. In July 2023, NJDEP published the Inland Flood Protection Rule, which requires municipalities to update their stormwater control ordinances to improve water quality. The Watershed Institute’s webinar, which was part of its “Technical Friday" webinar series, not only provided participants with a clear understanding of the recent rule updates and guidance on how to implement best practices, but also provided the opportunity for everyone to get their questions answered. To view the full webinar, click below: [embed]https://www.youtube.com/watch?v=ROn4wtzyp4k&feature=youtu.be[/embed] The Watershed Institute's next "Technical Friday" webinar, which is free to attend, will focus on "Stormwater Design: Myths and Misconceptions." One of the most complicated aspects of a new development application is designing the stormwater management infrastructure. It is also one of the most complex parts of reviewing applications before New Jersey’s land use boards. While stormwater management is a difficult and complex issue, it is vital to the health and wellbeing of New Jersey communities and residents. The state's 2023 Municipal Separate Storm Sewer System (MS4) permit puts front and center New Jersey's obligation to review the stormwater issues caused by land development. Better design submissions will assist in reaching this goal and may speed up the process of review and approval. On December 8 from 10 am - 12 pm, join Gabriel Mahon, PE, Bureau Chief of the Bureau of NJPDES Stormwater permitting and Water Quality Management and Dr. Clay Emerson, PhD, PE, CFM from Princeton Hydro as they examine some of the common issues they uncover in stormwater management proposals and provide guidance on incorporating best practices and submitting designs that successfully address New Jersey's stormwater management goals. Click here to register. The Watershed Institute, established in 1949, is a nonprofit organization located in Central New Jersey that promotes and advocates conservation and restoration of natural habitats, collects data on environmental conditions in its watersheds, and provides environmental education through numerous programs. To learn more about The Watershed Institute, click here. At Princeton Hydro, we recognize the benefit of green infrastructure and we’ve been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We are a leader in innovative, cost-effective, and environmentally sound stormwater management systems. The preparation of stormwater management plans and design of stormwater management systems for pollutant reduction is an integral part of our projects. Click here to read about an award-winning Green Infrastructure stormwater management & Floodplain Restoration project we completed on Blue Acres Property in Linden’s Tremley Point. [post_title] => WATCH: Webinar on NJDEP Enhanced Stormwater Management Ordinance [post_excerpt] => [post_status] => publish [comment_status] => open [ping_status] => open [post_password] => [post_name] => watch-webinar-on-njdep-enhanced-stormwater-management-ordinance [to_ping] => [pinged] => [post_modified] => 2024-12-10 17:48:09 [post_modified_gmt] => 2024-12-10 17:48:09 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?p=13876 [menu_order] => 0 [post_type] => post [post_mime_type] => [comment_count] => 0 [filter] => raw ) [1] => WP_Post Object ( [ID] => 4961 [post_author] => 3 [post_date] => 2020-06-19 14:22:14 [post_date_gmt] => 2020-06-19 14:22:14 [post_content] => In March 2020, NJ Department of Environmental Protection (NJDEP) published the long-awaited revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which now requires the use of green infrastructure. But what do these updates actually mean for New Jersey’s stormwater infrastructure? At Princeton Hydro, we recognize the benefit of green infrastructure and we've been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We've been following the rule amendments very closely, so we’ve got the inside scoop on how to interpret these new updates. In this blog, we’ll break down the complexities and changes to help you understand what’s really going on. What is Green Infrastructure? So, let’s start with what green infrastructure actually is in a general sense. Many people think of green infrastructure solely as a way to classify certain stormwater best management practices, or BMPs, but in reality, it goes much deeper than that. Green infrastructure is an approach to engineering design that emphasizes the use of natural processes. Examples include green roofs, rain gardens, constructed wetlands, vegetated bioswales, and living shorelines. In general, approaching environmental management from this lens can help reduce costs and negative impacts to our ecosystems. The benefit to using green infrastructure over structural grey infrastructure is that these living BMPs are incredibly resilient. Being living systems, green infrastructure BMPs help decrease stormwater volume, as soil and vegetation naturally retain and evapotranspire water. Afterall, those natural processes have successfully worked for billions of years, so why not mimic them in our design? In addition to effectively managing stormwater, green infrastructure has other added benefits such as reducing the heat island effect, reducing energy use, removing pollutants from the air, beautifying public spaces, and even increasing property value. Though the actual practice of green infrastructure may seem new and innovative, the concept has been around for decades. What’s Changed? So now, let’s get to the updated regulations. The biggest takeaway from this update is that green infrastructure is now required to meet the three performance criteria that NJDEP sets forth for stormwater management. The amendments to the rule give definitions of green infrastructure as it applies to stormwater management. The rule defines green infrastructure as follows: "‘Green Infrastructure’ means a stormwater management measure that manages stormwater close to its source by: Treating stormwater runoff through infiltration into subsoil; Treating stormwater runoff through filtration by vegetation or soil; or Storing stormwater runoff for reuse.” NJDEP evaluates stormwater management compliance through three basic performance metrics: (1) groundwater recharge, (2) water quality, and (3) peak flow control. While these metrics have remained relatively unchanged under the amended rule, the requirements for meeting them have been modified to include green infrastructure. The pre-existing rule required that major developments incorporate nonstructural stormwater management BMPs/strategies to the “maximum extent practicable” to meet their criteria. The amended rule not only gives specific suggestions for the kind of BMPs it's looking for by adding a definition of green infrastructure, but it also makes those BMPs/strategies a requirement for compliance with the rule’s minimum standards. The rule also includes tables outlining/summarizing the application of each type of stormwater BMP. One of the biggest changes here is that some of those BMPs have drainage area limitations, which could pose new challenges in the design process. As stated above, the rule defines green infrastructure as, “a stormwater management measure that manages stormwater close to its source.” This is where those drainage area limitations come into play. Dry wells have a one acre drainage area limitation, which is not new, however, pervious pavement has a 3:1 ratio requirement, meaning that the water flowing over standard pavement, or impervious surfaces, should not be more than three times greater than the area of the pervious pavement. Likewise, in the amended rule, BMPs like bioretention systems, have a drainage area limitation of 2.5 acres. The addition of this requirement will require designers to spread BMPs out throughout their site, instead of simply including one large structural BMP in a single location on the site. This approach decentralizes and distributes BMPs, enabling more stormwater to infiltrate into the ground, rather than runoff. Because this method more clostely mimics the natural water cycle, it is expected to foster better long-term performance of the BMPs. This 2.5-acre drainage area limitation is going to effect stormwater design in that it will lead to BMP decentralization. So, project sites will likely have numerous smaller BMPs that will be distributed throughout the area, as opposed to having one large basin at the bottom of the site. This applies, in particular, to large scale commercial and residential projects, as the updated rule will discourage, and in most cases actually not allow, for the implementation of one large basin at the bottom of the site, which currently is common practice in large-scale development design. Motor Vehicle Surfaces Another update to the rule is that motor vehicle surfaces are now incorporated into the definition of major development, which was further clarified and defined as: “Any individual ‘development,’ as well as multiple developments that individually or collectively result in: The disturbance of one or more acres of land since February 2, 2004; The creation of one-quarter acre or more of “regulated impervious surface” since February 2, 2004; The creation of one-quarter acre or more of “regulated motor vehicle surface” since March 2,2021; or A combination of 2 and 3 above that totals an area of one-quarter acre or more. The same surface shall not be counted twice when determining if the combination area equals one quarter acre or more.” The amended rule requires these motor vehicle surfaces to have 80% total suspended solids (TSS) removal, in order to maintain water quality. These surfaces include standard pavement drive/parking areas and gravel and dirt drive/parking areas, according to the rule. However, the rule does not require water quality control for runoff from other impervious surfaces that are not traveled by automobiles, such as rooftops and sidewalks, or other paved walkway areas. Revisions to BMP Manual In addition to the changes made to the actual rule, NJDEP released an updated draft of Chapters 5, 12, 13, and Appendix D of the NJ Stormwater BMP Manual, which is currently open for public comment. Chapter 5 regards Stormwater Management and Quantity and Quality Standards and Computations and Chapter 12 regards Soil Testing Criteria. The biggest update to the manual is the addition of the recently finalized Chapter 13: Groundwater Table Hydraulic Impact Assessments for Infiltration BMPs, which requires design engineers to assess the hydraulic impact on the groundwater table to avoid adverse impacts such as surficial ponding, flooding of basements, interference with sewage disposal systems, and interference with the proper functioning of the BMP itself. The addition of this chapter will ensure that these issues are minimized, helping to improve the state’s stormwater management practices overall. What does this all mean for New Jersey Municipalities? New Jersey municipalities will need to comply with the new standards, as the NJ Stormwater Management Rule represents the minimum requirements for stormwater control ordinances. The law states that municipalities must update their ordinances by March 2, 2021. To make this transition a bit smoother, NJDEP has released a revised model ordinance in Appendix D of the NJ Stormwater BMP Manual to act as a sample for municipalities to follow when adopting these new regulations. Similar to before, municipalities do have the ability to require stricter stormwater performance metrics, but the criteria outlined in the rule are the minimum that must be met under the new regulations. For more information on the updates to the stormwater regulations, you can check out an informational webinar (below) hosted by NJ-AWRA and The Watershed Institute. This webinar includes three presentations by New Jersey stormwater experts, including our Director of Stormwater Management & Green Infrastructure, Dr. Clay Emerson, PE, CFM. [embed]https://youtu.be/wy0i6qCY2TM[/embed] [post_title] => Understanding The Updated NJ Stormwater Rule [post_excerpt] => [post_status] => publish [comment_status] => open [ping_status] => open [post_password] => [post_name] => nj-stormwater-regulations-2020 [to_ping] => [pinged] => [post_modified] => 2025-11-04 02:44:42 [post_modified_gmt] => 2025-11-04 02:44:42 [post_content_filtered] => [post_parent] => 0 [guid] => https://www.princetonhydro.com/blog/?p=4961 [menu_order] => 0 [post_type] => post [post_mime_type] => [comment_count] => 0 [filter] => raw ) [2] => WP_Post Object ( [ID] => 2078 [post_author] => 3 [post_date] => 2018-06-25 17:19:19 [post_date_gmt] => 2018-06-25 17:19:19 [post_content] => This summer, Princeton Hydro is hosting five interns, each of whom are passionate about protecting water quality and preserving our natural resources. From June to August, our interns will gain professional work experience in a variety of subject areas, ranging from stormwater management to dam restoration to ecological design to lake management and much more. They are assisting on a variety of projects, getting real-world practice in their areas of study, and working with a Princeton Hydro mentor who is helping them gain a deeper understanding of the business of environmental and engineering consulting and setting them up for career success. Let's Meet Our Interns: Ivy Babson, Environmental Science Intern Ivy is a rising senior from University of Vermont, majoring in Environmental Science with a concentration in Ecological Design, and minor in Geospatial Technologies. In the future, she hopes to implement ecological design in urban areas and create a sustainable environment that would allow future generations to care for and interact with a healthy earth. Ivy will work alongside Senior Aquatics Scientist Dr. Jack Szczepanski and the Princeton Hydro Aquatics team on projects related to lake and pond management, including fisheries management, data collection and analysis, and water quality monitoring. Recently, Ivy assisted Aquatic Ecologist Jesse Smith in completing an electrofishing survey in a Northern New Jersey river. Learn more about Ivy. Marissa Ciocco, Geotechnical Intern Marissa is entering her fourth year at Rowan University where she is a Civil and Environmental Engineering major with a Bantivoglio Honors Concentration. In the future, Marissa hopes to work towards creating a greener and safer environment. During her internship, Marissa will be mentored by Jim Hunt P.E., Geotechnical Engineer, who has already engaged Marissa in a few construction oversight projects, including a culvert restoration effort in Medford Lakes, NJ and observing geotechnical borings in Evesham, NJ. Learn more about Marissa. Will Kelleher, Environmental Science Intern Will is a rising junior at the University of Vermont, studying Environmental Science with a concentration in Water Resources. His current career interests are focused around wetlands restoration and water chemistry. He recently spent two weeks studying water management and sustainable technology in the Netherlands and in the past has helped with biological and chemical stream monitoring with Raritan Headwaters Association. Mentored by Senior Aquatics Scientist Dr. Jack Szczepanski, Will’s area of focus will be lake and pond management. He’ll spend most of his time in the field alongside members of the Aquatics Team collecting water quality data and mapping aquatic plants, learning about aquatic habitat creation, and implementing various invasive aquatic weed control efforts. Learn more about Will. Veronica Moditz, Water Resources Intern We are thrilled to welcome back Veronica, who interned with us last year, and is in her final year at Stevens Institute of Technology, pursuing a Bachelor Degree in Environmental Engineering and a Master Degree in Sustainability Management. She is currently the secretary for Steven's Environmental Engineering Professional Society chapter. In the future, she hopes to work on more sustainable approach to engineering problems. Veronica will work alongside Project Engineer and Construction Specialist Amy McNamara, EIT, and Mary L. Paist-Goldman, P.E., Director of Engineering Services, on a variety of environmental engineering projects. Most recently, she assisted with a construction oversight and stormwater management project in Morris County, NJ. Tucker Simmons, Water Resources Engineer Tucker is a Civil and Environmental Engineering major at Rowan University focusing on Water Resources Engineering. His Junior Clinic experience includes the study of Bio-Cemented sand and the Remote Sensing of Landfill Fires. In the future, Tucker hopes to work on creating a more sustainable environment. Throughout his internship, Tucker will be mentored by Dr. Clay Emerson, P.E. CFM, Senior Water Resources Engineer, and will work on projects related to stormwater management, hydrologic and hydraulic analysis, and various aspects of environmental restoration. He recently assisted with a sink hole inspection in Tredyffrin Township, PA and mapped the water depths of a lake in Bucks County, PA. Stay tuned for updates on what our interns are working on! … [post_title] => EMPLOYEE SPOTLIGHT: Meet the Interns [post_excerpt] => [post_status] => publish [comment_status] => open [ping_status] => open [post_password] => [post_name] => meet-the-interns-2018 [to_ping] => [pinged] => [post_modified] => 2025-11-04 02:15:22 [post_modified_gmt] => 2025-11-04 02:15:22 [post_content_filtered] => [post_parent] => 0 [guid] => http://www.princetonhydro.com/blog/?p=2078 [menu_order] => 0 [post_type] => post [post_mime_type] => [comment_count] => 0 [filter] => raw ) ) [post_count] => 3 [current_post] => -1 [before_loop] => 1 [in_the_loop] => [post] => WP_Post Object ( [ID] => 13876 [post_author] => 1 [post_date] => 2023-11-07 16:12:00 [post_date_gmt] => 2023-11-07 16:12:00 [post_content] => The Watershed Institute hosted a webinar on Enhanced Stormwater Management Ordinances, which featured two expert speakers: Princeton Hydro Senior Technical Director of Engineering Dr. Clay Emerson, PE, CFM, and The Watershed Institute Policy Director Michael Pisauro, Esq. They provided guidance on NJDEP's new stormwater ordinances, a summary of requirements, and recommendations for developing and implementing stronger ordinances. Co-sponsored by the American Littoral Society, Association of New Jersey Environmental Commissions, and Pinelands Preservation Alliance, the webinar was attended by officials, planning board members, municipal professionals (engineers and planners), attorneys and Environmental Commission members from all across the state. In March 2020, NJ Department of Environmental Protection (NJDEP) published revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which states that, in order to meet stormwater management performance criteria set forth by NJDEP, New Jersey municipalities are required to update their stormwater control ordinances to incorporate green infrastructure. Check out our blog detailing the updated requirements. NJDEP periodically updates the stormwater rules and provides municipalities with a deadline to incorporate the rule changes in order to stay in compliance. In July 2023, NJDEP published the Inland Flood Protection Rule, which requires municipalities to update their stormwater control ordinances to improve water quality. The Watershed Institute’s webinar, which was part of its “Technical Friday" webinar series, not only provided participants with a clear understanding of the recent rule updates and guidance on how to implement best practices, but also provided the opportunity for everyone to get their questions answered. To view the full webinar, click below: [embed]https://www.youtube.com/watch?v=ROn4wtzyp4k&feature=youtu.be[/embed] The Watershed Institute's next "Technical Friday" webinar, which is free to attend, will focus on "Stormwater Design: Myths and Misconceptions." One of the most complicated aspects of a new development application is designing the stormwater management infrastructure. It is also one of the most complex parts of reviewing applications before New Jersey’s land use boards. While stormwater management is a difficult and complex issue, it is vital to the health and wellbeing of New Jersey communities and residents. The state's 2023 Municipal Separate Storm Sewer System (MS4) permit puts front and center New Jersey's obligation to review the stormwater issues caused by land development. Better design submissions will assist in reaching this goal and may speed up the process of review and approval. On December 8 from 10 am - 12 pm, join Gabriel Mahon, PE, Bureau Chief of the Bureau of NJPDES Stormwater permitting and Water Quality Management and Dr. Clay Emerson, PhD, PE, CFM from Princeton Hydro as they examine some of the common issues they uncover in stormwater management proposals and provide guidance on incorporating best practices and submitting designs that successfully address New Jersey's stormwater management goals. Click here to register. The Watershed Institute, established in 1949, is a nonprofit organization located in Central New Jersey that promotes and advocates conservation and restoration of natural habitats, collects data on environmental conditions in its watersheds, and provides environmental education through numerous programs. To learn more about The Watershed Institute, click here. At Princeton Hydro, we recognize the benefit of green infrastructure and we’ve been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We are a leader in innovative, cost-effective, and environmentally sound stormwater management systems. The preparation of stormwater management plans and design of stormwater management systems for pollutant reduction is an integral part of our projects. Click here to read about an award-winning Green Infrastructure stormwater management & Floodplain Restoration project we completed on Blue Acres Property in Linden’s Tremley Point. 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The Watershed Institute hosted a webinar on Enhanced Stormwater Management Ordinances, which featured two expert speakers: Princeton Hydro Senior Technical Director of Engineering Dr. Clay Emerson, PE, CFM, and The Watershed Institute Policy Director Michael Pisauro, Esq. They provided guidance on NJDEP's new stormwater ordinances, a summary of requirements, and recommendations for developing and implementing stronger ordinances.
Co-sponsored by the American Littoral Society, Association of New Jersey Environmental Commissions, and Pinelands Preservation Alliance, the webinar was attended by officials, planning board members, municipal professionals (engineers and planners), attorneys and Environmental Commission members from all across the state.
In March 2020, NJ Department of Environmental Protection (NJDEP) published revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which states that, in order to meet stormwater management performance criteria set forth by NJDEP, New Jersey municipalities are required to update their stormwater control ordinances to incorporate green infrastructure. Check out our blog detailing the updated requirements.
NJDEP periodically updates the stormwater rules and provides municipalities with a deadline to incorporate the rule changes in order to stay in compliance. In July 2023, NJDEP published the Inland Flood Protection Rule, which requires municipalities to update their stormwater control ordinances to improve water quality. The Watershed Institute’s webinar, which was part of its “Technical Friday" webinar series, not only provided participants with a clear understanding of the recent rule updates and guidance on how to implement best practices, but also provided the opportunity for everyone to get their questions answered.
To view the full webinar, click below:
The Watershed Institute's next "Technical Friday" webinar, which is free to attend, will focus on "Stormwater Design: Myths and Misconceptions." One of the most complicated aspects of a new development application is designing the stormwater management infrastructure. It is also one of the most complex parts of reviewing applications before New Jersey’s land use boards. While stormwater management is a difficult and complex issue, it is vital to the health and wellbeing of New Jersey communities and residents. The state's 2023 Municipal Separate Storm Sewer System (MS4) permit puts front and center New Jersey's obligation to review the stormwater issues caused by land development. Better design submissions will assist in reaching this goal and may speed up the process of review and approval.
On December 8 from 10 am - 12 pm, join Gabriel Mahon, PE, Bureau Chief of the Bureau of NJPDES Stormwater permitting and Water Quality Management and Dr. Clay Emerson, PhD, PE, CFM from Princeton Hydro as they examine some of the common issues they uncover in stormwater management proposals and provide guidance on incorporating best practices and submitting designs that successfully address New Jersey's stormwater management goals.
The Watershed Institute, established in 1949, is a nonprofit organization located in Central New Jersey that promotes and advocates conservation and restoration of natural habitats, collects data on environmental conditions in its watersheds, and provides environmental education through numerous programs. To learn more about The Watershed Institute, click here.
At Princeton Hydro, we recognize the benefit of green infrastructure and we’ve been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We are a leader in innovative, cost-effective, and environmentally sound stormwater management systems. The preparation of stormwater management plans and design of stormwater management systems for pollutant reduction is an integral part of our projects. Click here to read about an award-winning Green Infrastructure stormwater management & Floodplain Restoration project we completed on Blue Acres Property in Linden’s Tremley Point.
In March 2020, NJ Department of Environmental Protection (NJDEP) published the long-awaited revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which now requires the use of green infrastructure. But what do these updates actually mean for New Jersey’s stormwater infrastructure?
At Princeton Hydro, we recognize the benefit of green infrastructure and we've been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We've been following the rule amendments very closely, so we’ve got the inside scoop on how to interpret these new updates. In this blog, we’ll break down the complexities and changes to help you understand what’s really going on.
So, let’s start with what green infrastructure actually is in a general sense. Many people think of green infrastructure solely as a way to classify certain stormwater best management practices, or BMPs, but in reality, it goes much deeper than that. Green infrastructure is an approach to engineering design that emphasizes the use of natural processes. Examples include green roofs, rain gardens, constructed wetlands, vegetated bioswales, and living shorelines. In general, approaching environmental management from this lens can help reduce costs and negative impacts to our ecosystems. The benefit to using green infrastructure over structural grey infrastructure is that these living BMPs are incredibly resilient. Being living systems, green infrastructure BMPs help decrease stormwater volume, as soil and vegetation naturally retain and evapotranspire water. Afterall, those natural processes have successfully worked for billions of years, so why not mimic them in our design?
In addition to effectively managing stormwater, green infrastructure has other added benefits such as reducing the heat island effect, reducing energy use, removing pollutants from the air, beautifying public spaces, and even increasing property value. Though the actual practice of green infrastructure may seem new and innovative, the concept has been around for decades.
So now, let’s get to the updated regulations. The biggest takeaway from this update is that green infrastructure is now required to meet the three performance criteria that NJDEP sets forth for stormwater management. The amendments to the rule give definitions of green infrastructure as it applies to stormwater management. The rule defines green infrastructure as follows:
"‘Green Infrastructure’ means a stormwater management measure that manages stormwater close to its source by:
Treating stormwater runoff through infiltration into subsoil;
Treating stormwater runoff through filtration by vegetation or soil; or
Storing stormwater runoff for reuse.”
NJDEP evaluates stormwater management compliance through three basic performance metrics: (1) groundwater recharge, (2) water quality, and (3) peak flow control. While these metrics have remained relatively unchanged under the amended rule, the requirements for meeting them have been modified to include green infrastructure. The pre-existing rule required that major developments incorporate nonstructural stormwater management BMPs/strategies to the “maximum extent practicable” to meet their criteria. The amended rule not only gives specific suggestions for the kind of BMPs it's looking for by adding a definition of green infrastructure, but it also makes those BMPs/strategies a requirement for compliance with the rule’s minimum standards.
The rule also includes tables outlining/summarizing the application of each type of stormwater BMP. One of the biggest changes here is that some of those BMPs have drainage area limitations, which could pose new challenges in the design process.
As stated above, the rule defines green infrastructure as, “a stormwater management measure that manages stormwater close to its source.” This is where those drainage area limitations come into play. Dry wells have a one acre drainage area limitation, which is not new, however, pervious pavement has a 3:1 ratio requirement, meaning that the water flowing over standard pavement, or impervious surfaces, should not be more than three times greater than the area of the pervious pavement.
Likewise, in the amended rule, BMPs like bioretention systems, have a drainage area limitation of 2.5 acres. The addition of this requirement will require designers to spread BMPs out throughout their site, instead of simply including one large structural BMP in a single location on the site. This approach decentralizes and distributes BMPs, enabling more stormwater to infiltrate into the ground, rather than runoff. Because this method more clostely mimics the natural water cycle, it is expected to foster better long-term performance of the BMPs.
This 2.5-acre drainage area limitation is going to effect stormwater design in that it will lead to BMP decentralization. So, project sites will likely have numerous smaller BMPs that will be distributed throughout the area, as opposed to having one large basin at the bottom of the site. This applies, in particular, to large scale commercial and residential projects, as the updated rule will discourage, and in most cases actually not allow, for the implementation of one large basin at the bottom of the site, which currently is common practice in large-scale development design.
Another update to the rule is that motor vehicle surfaces are now incorporated into the definition of major development, which was further clarified and defined as:
“Any individual ‘development,’ as well as multiple developments that individually or collectively result in:
The disturbance of one or more acres of land since February 2, 2004;
The creation of one-quarter acre or more of “regulated impervious surface” since February 2, 2004;
The creation of one-quarter acre or more of “regulated motor vehicle surface” since March 2,2021; or
A combination of 2 and 3 above that totals an area of one-quarter acre or more. The same surface shall not be counted twice when determining if the combination area equals one quarter acre or more.”
The amended rule requires these motor vehicle surfaces to have 80% total suspended solids (TSS) removal, in order to maintain water quality. These surfaces include standard pavement drive/parking areas and gravel and dirt drive/parking areas, according to the rule. However, the rule does not require water quality control for runoff from other impervious surfaces that are not traveled by automobiles, such as rooftops and sidewalks, or other paved walkway areas.
In addition to the changes made to the actual rule, NJDEP released an updated draft of Chapters 5, 12, 13, and Appendix D of the NJ Stormwater BMP Manual, which is currently open for public comment. Chapter 5 regards Stormwater Management and Quantity and Quality Standards and Computations and Chapter 12 regards Soil Testing Criteria. The biggest update to the manual is the addition of the recently finalized Chapter 13: Groundwater Table Hydraulic Impact Assessments for Infiltration BMPs, which requires design engineers to assess the hydraulic impact on the groundwater table to avoid adverse impacts such as surficial ponding, flooding of basements, interference with sewage disposal systems, and interference with the proper functioning of the BMP itself. The addition of this chapter will ensure that these issues are minimized, helping to improve the state’s stormwater management practices overall.
New Jersey municipalities will need to comply with the new standards, as the NJ Stormwater Management Rule represents the minimum requirements for stormwater control ordinances. The law states that municipalities must update their ordinances by March 2, 2021. To make this transition a bit smoother, NJDEP has released a revised model ordinance in Appendix D of the NJ Stormwater BMP Manual to act as a sample for municipalities to follow when adopting these new regulations. Similar to before, municipalities do have the ability to require stricter stormwater performance metrics, but the criteria outlined in the rule are the minimum that must be met under the new regulations.
For more information on the updates to the stormwater regulations, you can check out an informational webinar (below) hosted by NJ-AWRA and The Watershed Institute. This webinar includes three presentations by New Jersey stormwater experts, including our Director of Stormwater Management & Green Infrastructure, Dr. Clay Emerson, PE, CFM.
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