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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] => 13315 [post_author] => 1 [post_date] => 2023-07-27 16:44:27 [post_date_gmt] => 2023-07-27 16:44:27 [post_content] => Exciting changes have unfolded at Kol Emet, a Reconstructionist Congregation in Yardley, Bucks County, Pennsylvania. The campus’ exterior lands have undergone a remarkable transformation, blossoming into an enchanting and peaceful place for community member gatherings, and a wildflower meadow. Princeton Hydro partnered with Congregation Kol Emet to design and implement the synagogue's 10-acre campus transformation. The Princeton Hydro team provided green infrastructure engineering, landscape architecture, and construction services aimed at enhancing the usability and welcoming atmosphere of the synagogue, and creating a sustainable outdoor solution in the event of future pandemics, and a place to connect with the natural environment that surrounds the property. The design provides a net positive impact by reducing flooding in the community and improves water quality by augmenting stormwater management and biodiversity throughout the property. "Our vision surpassed mere construction of a gathering space," said Geoffrey M. Goll P.E., President of Princeton Hydro, a congregant of Kol Emet, Executive Board Member, and point person for the project. "We wanted to create a harmonious union between the synagogue campus and the surrounding preserved woodlands, cultivating a serene haven where congregants can unite, celebrate, and worship, while also enhancing the ecological functionality and biodiversity of the landscape. This was a realization of the vision of the Founders of Kol Emet and the labor and financial support of many members of the Board, past and present, and a generous donation by a longtime supporter of the community. The outdoor sanctuary was named in honor and memory of a founding member and former President, Geri Shatz, who was a staunch supporter of the Jewish community and advocate for the mission of Kol Emet. She lived the ideals of community and contribution. I am proud of the extraordinary transformation that’s been achieved." About the Congregation of Kol Emet The Kol Emet Reconstructionist Congregation, is a 501(c)3 religious organization, founded in 1984. While a center of worship for its members, it is much more than that. Kol Emet is a community of people who care about improving the world around them through social action and environmental protection. The sentiment of "Tikkun Olam" is embodied by Kol Emet and the committee that spearheaded the project, working directly with the Princeton Hydro team to bring the project goals to fruition. The modern interpretation of the Hebrew phrase “Tikkun Olam,” is “action intended to repair and improve the world.” The campus restoration project brings the concept of “Tikkun Olam” to life. About the Restoration Project Princeton Hydro Landscape Architect Cory Speroff, PLA, ASLA, CBLP is the project’s lead designer. The project included landscape design and planting that incorporates native and sustainable trees and shrubs; significant upgrades to the existing stormwater management basin, including the conversion of low-flow channels, impervious surfaces, and turf-covered areas to native grassland and wildflower habitat; and the development of the “Geri Shatz Outdoor Contemplative Space." Cory’s design inspiration for the Geri Shatz Outdoor Contemplative Space is modeled after the Hebrew term “etz chaim” or “Tree of Life.” In Judaism, the Tree of Life has a number of meanings, both literal and figurative. In the Kabbalah, the Tree of Life represents the connection between heaven and earth, wisdom and knowledge, and the interconnectedness of all living things. It is visually represented as a diagram that looks much like a tree with 10 nodes and 22 lines. Cory’s design for the community space uses strategically placed trees to mimic the Tree of Life and aims to promote community connection and a connection to the surrounding natural landscape. The contemplative space consists of a bimah, seating to accommodate at least 80 people, and a beautiful array of native trees and flowering shrubs, including black gum, silver birch, and Virginia sweetspire. [gallery link="none" columns="2" ids="13117,13071"] Cory’s design for the land surrounding the contemplative space improves flood resilience; controls stormwater runoff volume and promotes groundwater recharge; boosts safety features of the campus; and enhances habitat for pollinators, native plants, and other important species. The wildflower meadow was seeded with a variety of native plants, including purple love grass, common milkweed, wild bergamot, and blue wild indigo. [gallery link="none" columns="2" ids="13055,13081"] [gallery columns="2" link="none" ids="13042,13044"] “During the height of the COVID-19 pandemic, it felt like the only way to see our loved ones was to be outside, and during these backyard and front porch gatherings many people re-discovered their love for the outdoors,” said Cory. “In talking with the Committee, there was a desire to create an outdoor sanctuary where the congregation could gather and continue that re-discovery. I believe that through the careful consideration of symbolic elements and thoughtful design choices, we’ve created a space that can inspire introspection, connection, and a sense of harmony with both nature and faith.” The Generosity that Made the Project Possible Funding for the project came from the Congregation Kol Emet’s “Our Heart. Our Home” capital campaign, a $750,000 campaign focused on upgrading four key aspects of the synagogue: social hall, HVAC upgrades, indoor sanctuary, outside school, and the new outdoor sanctuary. The outdoor sanctuary and ecological uplift to the 10-acre campus is a primary piece of the campaign and was made possible by the generous donations of several Kol Emet members. Stan Shatz bestowed a bounteous donation in memory of Geri Shatz, which made possible the creation of the “Geri Shatz Outdoor Contemplative Space.” The following families also contributed to the funding of the Geri Shatz Outdoor Contemplative Space: Laurel & Kevin Bloch, Barbara & Debra Fogel and Family, Jill & David Gordon, Annie & Ryan Kubanoff and Family, and Teddi & Josh Matisoff and Family. The Princeton Hydro team is honored to have worked with Kol Emet on this important and inspirational project. Enjoying and Celebrating the New Space Congregation Kol Emet came together on Sunday, June 4, 2023 for a celebration and ribbon-cutting ceremony to mark the completion of the outdoor sanctuary project. Here are a few photos from the joyous event: [gallery link="none" ids="13125,13116,13130"] Princeton Hydro is an expert in engineering, ecological restoration, and landscape architecture, and we’ve been incorporating green stormwater infrastructure and nature-based solutions into our designs for decades. Click here to read about the landscape restoration and stormwater management project we designed and implemented in Thompson Park, a 675-acre recreation area in Middlesex County, New Jersey. [post_title] => From Turf to Biodiverse Outdoor Space: The Remarkable Transformation of Congregation Kol Emet’s 10-Acre Campus [post_excerpt] => [post_status] => publish [comment_status] => open [ping_status] => open [post_password] => [post_name] => transforming-kol-emet-campus [to_ping] => [pinged] => [post_modified] => 2024-01-18 03:45:39 [post_modified_gmt] => 2024-01-18 03:45:39 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?p=13315 [menu_order] => 0 [post_type] => post [post_mime_type] => [comment_count] => 0 [filter] => raw ) [2] => WP_Post Object ( [ID] => 9403 [post_author] => 1 [post_date] => 2021-12-27 12:55:10 [post_date_gmt] => 2021-12-27 12:55:10 [post_content] => What is Stormwater Runoff? Stormwater runoff is all of the rainfall or snowmelt water that is not absorbed into the ground and instead flows over land. When not managed properly, stormwater runoff causes issues like pollution in our waterways, flooding, and erosion. Stormwater runoff has been cited in multiple studies as a leading cause of water quality impairment to our local lakes and rivers. And, with increasing levels of rainfall from climate change impacts, stormwater management is an especially critical issue for communities all across the U.S. What is Stormwater Management? Stormwater management focuses on reducing runoff and improving water quality through a variety of techniques. Traditional stormwater management methods include things like storm drains, retention ponds, and culverts. Green stormwater infrastructure uses vegetation, soil, and other natural components to manage stormwater. Green stormwater infrastructure systems mimic natural hydrology to take advantage of interception, evapotranspiration, and infiltration of stormwater runoff at its source. Examples include rain gardens, constructed wetlands, vegetated bioswales, and living shorelines. Many stormwater systems include a combination of grey and green infrastructure management practices. Stormwater management treatment "trains" combine multiple stormwater management processes in order to prevent pollution and decrease stormwater flow volumes that negatively affect the receiving waterbody. Let’s Take a Look at a Stormwater Treatment Train in Action The Thompson Park Zoo in New Jersey Thompson Park is a 675-acre recreation area - the largest developed park in the Middlesex County park system - with numerous attractions including playgrounds, ballfields, hiking trails, and a zoo. The zoo is an animal haven that houses over 50 geese and fowl, goats, and approximately 90 deer in a fenced enclosure. The park also features Lake Manalapan. Within the zoo is a 0.25-acre pond that impounds stormwater runoff from adjacent uplands and two stormwater-fed tributaries to Lake Manalapan and Manalapan Brook. There are three tributaries to the pond with varying levels of erosion. The western tributary contains a headcut that is approximately four feet high. A headcut is created by a sudden down-cutting of the stream bottom. Similar to a miniature waterfall, a headcut slowly migrates upstream and becomes deeper as it progresses. The headcut in the Zoo tributary had destabilized the stream by eroding and incising its channel and banks. Additionally, foraging by Zoo inhabitants had removed most ground cover around the pond and associated tributaries, which also caused erosion. The bare soil conditions, headcut, and manure from the Zoo animals were contributing sediment, nutrient, and pathogen loading to the Zoo pond and subsequently Lake Manalapan. The Zoo pond drains to an outlet structure, a 24-inch reinforced concrete pipe (RCP), and subsequently to a vegetated swale via a stormwater outlet. A second outlet pipe drains stormwater runoff from an asphalt parking lot which discharges to the vegetated swale. The shoreline of Lake Manalapan where the vegetated swale drains into the lake was the subject of a previous restoration project during which a diverse suite of native plants was installed; however, the swale was not included in this project and a maintained lawn, which does not adequately filter stormwater runoff or provide any ecosystem services. The swale also had little access to its floodplain where vegetation can help filter non-point source (NPS) pollutants from the Zoo pond and adjacent uplands. Images taken in September 2021, before the restoration work commenced, show areas of erosion and a riparian zone devoid of vegetation. Implementing a Stormwater Management Treatment Train In order to increase channel stability, decrease erosion, improve water quality and ecological function, and reduce the NPS pollutants originating from the Zoo, a stormwater management treatment train was designed and constructed. Middlesex County Office of Parks and Recreation and Office of Planning, the New Jersey Department of Environmental Protection (NJDEP), South Jersey Resource Conservation and Development Council (SJRC&D), Middlesex County Mosquito Extermination Commission, Freehold Soil Conservation District, Rutgers Cooperative Extension, Enviroscapes and Princeton Hydro worked together to fund, design, permit, and construct the following stormwater management measures:
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.
Exciting changes have unfolded at Kol Emet, a Reconstructionist Congregation in Yardley, Bucks County, Pennsylvania. The campus’ exterior lands have undergone a remarkable transformation, blossoming into an enchanting and peaceful place for community member gatherings, and a wildflower meadow.
Princeton Hydro partnered with Congregation Kol Emet to design and implement the synagogue's 10-acre campus transformation. The Princeton Hydro team provided green infrastructure engineering, landscape architecture, and construction services aimed at enhancing the usability and welcoming atmosphere of the synagogue, and creating a sustainable outdoor solution in the event of future pandemics, and a place to connect with the natural environment that surrounds the property. The design provides a net positive impact by reducing flooding in the community and improves water quality by augmenting stormwater management and biodiversity throughout the property.
"Our vision surpassed mere construction of a gathering space," said Geoffrey M. Goll P.E., President of Princeton Hydro, a congregant of Kol Emet, Executive Board Member, and point person for the project. "We wanted to create a harmonious union between the synagogue campus and the surrounding preserved woodlands, cultivating a serene haven where congregants can unite, celebrate, and worship, while also enhancing the ecological functionality and biodiversity of the landscape. This was a realization of the vision of the Founders of Kol Emet and the labor and financial support of many members of the Board, past and present, and a generous donation by a longtime supporter of the community. The outdoor sanctuary was named in honor and memory of a founding member and former President, Geri Shatz, who was a staunch supporter of the Jewish community and advocate for the mission of Kol Emet. She lived the ideals of community and contribution. I am proud of the extraordinary transformation that’s been achieved."
The Kol Emet Reconstructionist Congregation, is a 501(c)3 religious organization, founded in 1984. While a center of worship for its members, it is much more than that. Kol Emet is a community of people who care about improving the world around them through social action and environmental protection.
The sentiment of "Tikkun Olam" is embodied by Kol Emet and the committee that spearheaded the project, working directly with the Princeton Hydro team to bring the project goals to fruition. The modern interpretation of the Hebrew phrase “Tikkun Olam,” is “action intended to repair and improve the world.” The campus restoration project brings the concept of “Tikkun Olam” to life.
Princeton Hydro Landscape Architect Cory Speroff, PLA, ASLA, CBLP is the project’s lead designer. The project included landscape design and planting that incorporates native and sustainable trees and shrubs; significant upgrades to the existing stormwater management basin, including the conversion of low-flow channels, impervious surfaces, and turf-covered areas to native grassland and wildflower habitat; and the development of the “Geri Shatz Outdoor Contemplative Space."
Cory’s design inspiration for the Geri Shatz Outdoor Contemplative Space is modeled after the Hebrew term “etz chaim” or “Tree of Life.” In Judaism, the Tree of Life has a number of meanings, both literal and figurative. In the Kabbalah, the Tree of Life represents the connection between heaven and earth, wisdom and knowledge, and the interconnectedness of all living things. It is visually represented as a diagram that looks much like a tree with 10 nodes and 22 lines. Cory’s design for the community space uses strategically placed trees to mimic the Tree of Life and aims to promote community connection and a connection to the surrounding natural landscape.
The contemplative space consists of a bimah, seating to accommodate at least 80 people, and a beautiful array of native trees and flowering shrubs, including black gum, silver birch, and Virginia sweetspire.
Cory’s design for the land surrounding the contemplative space improves flood resilience; controls stormwater runoff volume and promotes groundwater recharge; boosts safety features of the campus; and enhances habitat for pollinators, native plants, and other important species. The wildflower meadow was seeded with a variety of native plants, including purple love grass, common milkweed, wild bergamot, and blue wild indigo.
“During the height of the COVID-19 pandemic, it felt like the only way to see our loved ones was to be outside, and during these backyard and front porch gatherings many people re-discovered their love for the outdoors,” said Cory. “In talking with the Committee, there was a desire to create an outdoor sanctuary where the congregation could gather and continue that re-discovery. I believe that through the careful consideration of symbolic elements and thoughtful design choices, we’ve created a space that can inspire introspection, connection, and a sense of harmony with both nature and faith.”
Funding for the project came from the Congregation Kol Emet’s “Our Heart. Our Home” capital campaign, a $750,000 campaign focused on upgrading four key aspects of the synagogue: social hall, HVAC upgrades, indoor sanctuary, outside school, and the new outdoor sanctuary. The outdoor sanctuary and ecological uplift to the 10-acre campus is a primary piece of the campaign and was made possible by the generous donations of several Kol Emet members.
Stan Shatz bestowed a bounteous donation in memory of Geri Shatz, which made possible the creation of the “Geri Shatz Outdoor Contemplative Space.”
The following families also contributed to the funding of the Geri Shatz Outdoor Contemplative Space: Laurel & Kevin Bloch, Barbara & Debra Fogel and Family, Jill & David Gordon, Annie & Ryan Kubanoff and Family, and Teddi & Josh Matisoff and Family.
The Princeton Hydro team is honored to have worked with Kol Emet on this important and inspirational project.
Congregation Kol Emet came together on Sunday, June 4, 2023 for a celebration and ribbon-cutting ceremony to mark the completion of the outdoor sanctuary project. Here are a few photos from the joyous event:
Princeton Hydro is an expert in engineering, ecological restoration, and landscape architecture, and we’ve been incorporating green stormwater infrastructure and nature-based solutions into our designs for decades. Click here to read about the landscape restoration and stormwater management project we designed and implemented in Thompson Park, a 675-acre recreation area in Middlesex County, New Jersey.
Stormwater runoff is all of the rainfall or snowmelt water that is not absorbed into the ground and instead flows over land. When not managed properly, stormwater runoff causes issues like pollution in our waterways, flooding, and erosion. Stormwater runoff has been cited in multiple studies as a leading cause of water quality impairment to our local lakes and rivers. And, with increasing levels of rainfall from climate change impacts, stormwater management is an especially critical issue for communities all across the U.S.
Stormwater management focuses on reducing runoff and improving water quality through a variety of techniques.
Traditional stormwater management methods include things like storm drains, retention ponds, and culverts. Green stormwater infrastructure uses vegetation, soil, and other natural components to manage stormwater. Green stormwater infrastructure systems mimic natural hydrology to take advantage of interception, evapotranspiration, and infiltration of stormwater runoff at its source. Examples include rain gardens, constructed wetlands, vegetated bioswales, and living shorelines. Many stormwater systems include a combination of grey and green infrastructure management practices.
Stormwater management treatment "trains" combine multiple stormwater management processes in order to prevent pollution and decrease stormwater flow volumes that negatively affect the receiving waterbody.
Thompson Park is a 675-acre recreation area - the largest developed park in the Middlesex County park system - with numerous attractions including playgrounds, ballfields, hiking trails, and a zoo. The zoo is an animal haven that houses over 50 geese and fowl, goats, and approximately 90 deer in a fenced enclosure. The park also features Lake Manalapan.
Within the zoo is a 0.25-acre pond that impounds stormwater runoff from adjacent uplands and two stormwater-fed tributaries to Lake Manalapan and Manalapan Brook. There are three tributaries to the pond with varying levels of erosion. The western tributary contains a headcut that is approximately four feet high. A headcut is created by a sudden down-cutting of the stream bottom. Similar to a miniature waterfall, a headcut slowly migrates upstream and becomes deeper as it progresses. The headcut in the Zoo tributary had destabilized the stream by eroding and incising its channel and banks. Additionally, foraging by Zoo inhabitants had removed most ground cover around the pond and associated tributaries, which also caused erosion.
The bare soil conditions, headcut, and manure from the Zoo animals were contributing sediment, nutrient, and pathogen loading to the Zoo pond and subsequently Lake Manalapan. The Zoo pond drains to an outlet structure, a 24-inch reinforced concrete pipe (RCP), and subsequently to a vegetated swale via a stormwater outlet. A second outlet pipe drains stormwater runoff from an asphalt parking lot which discharges to the vegetated swale.
The shoreline of Lake Manalapan where the vegetated swale drains into the lake was the subject of a previous restoration project during which a diverse suite of native plants was installed; however, the swale was not included in this project and a maintained lawn, which does not adequately filter stormwater runoff or provide any ecosystem services. The swale also had little access to its floodplain where vegetation can help filter non-point source (NPS) pollutants from the Zoo pond and adjacent uplands.
In order to increase channel stability, decrease erosion, improve water quality and ecological function, and reduce the NPS pollutants originating from the Zoo, a stormwater management treatment train was designed and constructed.
Middlesex County Office of Parks and Recreation and Office of Planning, the New Jersey Department of Environmental Protection (NJDEP), South Jersey Resource Conservation and Development Council (SJRC&D), Middlesex County Mosquito Extermination Commission, Freehold Soil Conservation District, Rutgers Cooperative Extension, Enviroscapes and Princeton Hydro worked together to fund, design, permit, and construct the following stormwater management measures:
To see the project elements taking shape and being completed, watch our video:
The project is funded by a Water Quality Restoration 319(h) grant awarded to SJRC&D by the NJDEP for continued implementation of watershed-based measures to reduce NPS pollutant loading and compliance with a total phosphorus (TP) Total Maximum Daily Load (TMDL) established by the NJDEP for Lake Manalapan. The TMDL is a regulatory term in the U.S. Clean Water Act, that identifies the maximum amount of a pollutant (in this case phosphorus) that a waterbody can receive while still meeting water quality standards.
“The South Jersey Resource Conservation and Development Council was pleased to participate in this project. Partnering with these various governmental agencies and private entities to implement on the ground conservation and water quality improvements aligns perfectly with our mission. We are thrilled with the great work done at Thompson Park and look forward to continuing this partnership.”Craig McGee, South Jersey Resource Conservation and Development Council District Manager
“The South Jersey Resource Conservation and Development Council was pleased to participate in this project. Partnering with these various governmental agencies and private entities to implement on the ground conservation and water quality improvements aligns perfectly with our mission. We are thrilled with the great work done at Thompson Park and look forward to continuing this partnership.”
Construction of the stormwater treatment train components began in early August 2021 and was completed by the end of September 2021.
The first step of the stormwater treatment train was to stabilize the tributary to Lake Manalapan and its associated headcut. Streambank stabilization measures included grade modifications to create a gradual stream slope and dynamically stable form with improved habitat features, including riffles and pools, with gravel and cobble substrate. On August 17, grading of the floodplain bench began, the RCP was exposed, and the team started excavation for the lower three steps in the step-pool sequence.
On August 20, the rock grade and step-pool sequence were completed. And, fabric was installed along both sides of the rock-lined channel to increase stream-bank stability. Rock was placed within the pools to cover the edge of the fabric. We are very pleased to report that the newly restored channel held up to two large storm events during the construction process.
Bags of BioChar, a pure carbon charcoal-like substance made from organic material, were installed across the Zoo pond using an anchor and line system. The BioChar bags help to remove TP and other nutrients from the water column and bed sediments of the Zoo pond and subsequently Manalapan Brook Watershed. The team also built, planted and installed a floating wetland island, an effective green infrastructure solution that improves water quality by assimilating and removing excess nutrients that could fuel algae growth.
After conclusion of pipe lighting, excavation of the floodplain bench and installation of scour protection, native perennial vegetation was planted within the floodplain and swale in order to provide sediment deposition and nutrient uptake functions, as well as aquatic food web services and water temperature moderation before flows are discharged to Lake Manalapan. The plantings also enhance and create suitable avian and pollinator species habitat, and greater flora and fauna diversity.
This stormwater treatment train project improves the habitat and water quality of the Manalapan Brook Watershed by addressing NPS pollutants that originate from Thompson Park Zoo. The completed work also supports the Watershed Protection and Restoration Plan for the Manalapan Brook Watershed by reducing TSS and TP loads in compliance with the TMDL. Additionally, the project improves the overall ecosystem by stabilizing eroded streambanks, installing native and biodiverse vegetation, and reducing the quantity of pollutants entering Lake Manalapan.
“Thompson Park Zoo is an excellent model for showcasing a successful and comprehensive approach to stormwater management and watershed restoration through a dynamic multi-stakeholder partnership. We are so proud to be a part of this project and continue to support the Manalapan Brook Watershed Protection Plan through a variety of restoration activities.”Amy McNamara, E.I.T, Princeton Hydro Project Manager and Water Resource Engineer
“Thompson Park Zoo is an excellent model for showcasing a successful and comprehensive approach to stormwater management and watershed restoration through a dynamic multi-stakeholder partnership. We are so proud to be a part of this project and continue to support the Manalapan Brook Watershed Protection Plan through a variety of restoration activities.”
At Princeton Hydro, we are experts in stormwater management; we recognize the numerous benefits of green infrastructure; and we’ve been incorporating green infrastructure into our engineering designs since before the term was regularly used in the stormwater lexicon. Click here to learn more about our stormwater management services.
Over the past year, the Deal Lake Commission (DLC) has implemented a variety of stormwater management projects aimed at reducing the volume of stormwater runoff, decreasing total phosphorus loading, and preventing debris, sediment, and pollutants from flowing into waterbodies throughout the Deal Lake, Wesley Lake, and Sunset Lake Watersheds.
These projects encompass a strategic combination of stormwater best management practices (BMPs), including structural BMPs, non-structural controls, and green infrastructure techniques. These stormwater management projects were funded by a Clean Water Act Section 319(h) grant awarded by the New Jersey Department of Environmental Protection to the DLC.
Let’s take a look at some of the recently completed initiatives:
Manufactured Treatment Devices (MTDs) are pre-fabricated stormwater treatment structures used to address stormwater issues in highly developed, urban areas. MTDs capture and remove sediments, metals, hydrocarbons, and other pollutants from stormwater runoff before the runoff reaches surrounding waterbodies and/or storm sewer systems.
This year, Princeton Hydro worked with the DLC and Leon S. Avakian Engineers to design and install three MTDs throughout Asbury Park, NJ with the purpose of improving water quality in Sunset Lake.
Students from the Asbury Park High School Engineering Academy, led by their teacher Kevin Gould, were invited to observe one of the MTD installations. The educational field trip was combined with a presentation from Princeton Hydro’s Senior Aquatic Ecologist Dr. Jack Szczepanski, which was titled, “Ecology and Engineering in Asbury Park.”
Rain gardens are a cost effective, attractive, and sustainable way to minimize stormwater runoff and filter out pollutants. This aesthetic, low-maintenance addition to any outdoor landscape creates a functioning habitat that attracts pollinators, beneficial insects, and birds. And, in a small way, it helps reduce erosion, promote groundwater recharge, and minimize flooding.
The DLC along with the Deal Lake Watershed Alliance, Asbury Park's Environmental Shade Tree Commission (ESTC), Asbury Park Department of Public Works (DPW) and Princeton Hydro completed a major renovation to an existing rain garden located in front of the Asbury Park bus terminal and municipal building.
The rain garden, which was originally constructed by the ESTC, was not functioning properly due to one of the inlets being completely obstructed by sediment. The DPW helped clear the sediment and regrade it, while the ESTC removed invasive weeds and replanted it with native shrubs, perennials, and flowers.
Floating Wetland Islands (FWIs) are a low-cost, effective green infrastructure solution used to mitigate phosphorus and nitrogen stormwater pollution. FWIs are designed to mimic natural wetlands in a sustainable, efficient, and powerful way. They improve water quality by assimilating and removing excess nutrients that could fuel harmful algae blooms; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments.
The DLC worked with Princeton Hydro to design and install a total of 12 floating wetland islands, six in Sunset Lake and six in Wesley Lake. A team of volunteers, led by the DLC and Princeton Hydro, planted vegetation in each of the FWIs and launched and secured each island into the lakes.
Clean Water Act Section 319(h) grant related efforts will continue in the Spring of 2022 with the design and installation of “bioscape” gardens and tree boxes. Stay tuned for updates!
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To learn more about the Deal Lake Commission, click here. To read about one of Princeton Hydro’s recently completed stormwater management projects, click here.
The Dunes at Shoal Harbor, a coastal residential community in Monmouth County, New Jersey, is situated adjacent to both the Raritan Bay and the New York City Ferry channel. In July 2018, Princeton Hydro was contracted to restore this coastal community that was severely impacted by Hurricane Sandy. Today, we are thrilled to report that the shoreline protection design plans have been fully constructed and the project is complete.
In order to protect the coastal community from flooding, a revetment had been constructed on the property many years ago. The revetment, however, was significantly undersized and completely failed during Hurricane Sandy. The community was subjected to direct wave attack and flooding, homes were damaged, beach access was impaired, and the existing site-wide stormwater management basin and outfall was completely destroyed.
The installation of a 15-foot rock revetment (one foot above the 100-year floodplain elevation) constructed with four-foot diameter boulders;
The replacement of a failed elevated timber walkway with a concrete slab-on-grade walkway, restoring portions of the existing bulkhead, clearing invasive plants, and the complete restoration of the failed stormwater basin and outlet; and
The development of natural barriers to reduce the impacts of storm surges and protect the coastal community, including planting stabilizing coastal vegetation to prevent erosion and installing fencing along the dune to facilitate natural dune growth.
During the final walkthrough earlier this month, the Princeton Hydro team captured drone footage of the completed project site. Click below to watch the video:
For more images and background information on this project, check out the following photo gallery and read our original blog post from July 2018:
For more information about Princeton Hydro’s engineering services, go here.
Strawbridge Lake is located in Moorestown Township in Burlington County, New Jersey with portions of the watershed also extending into Mount Laurel and Evesham Townships. This 33-acre, tri-basin lake is a result of the impoundment of the confluence of Hooten Creek and the North Branch of the Pennsauken Creek that dates back to the 1920s.
The lake receives surface runoff through Hooten Creek to the Upper and Middle Basins and the Lower Basin receives runoff from the headwaters of the North Branch of Pennsauken Creek. The lake then discharges back into another section of the North Branch Pennsauken Creek, which then flows into the Delaware River.
The watershed area that drains into the Strawbridge Lake is made up of an intricate mix of land uses: agriculture, new and mature residential subdivisions, office parks, major highways, retail stores, and large industrial complexes. The lake and the park area that surrounds it are heavily used for a variety of recreational activities.
Children’s Pond, which is located in Strawbridge Lake Park, is a popular fishing spot in the community. The pond initially functions as a wetland and drains from the northern portion of the watershed. Sedimentation—the naturally occurring process of the deposition and accumulation of both organic and inorganic matter in the bottom and/or banks of waterbodies—had significantly reduced the mean pond depth, thereby reducing the pond’s aesthetic appeal, impairing the fishery, contributing to eutrophication, and impacting the water quality of Strawbridge Lake. Sedimentation can also lead to contamination that poses a threat to aquatic plant and wildlife.
The dredging of Children’s Pond was identified by Princeton Hydro's Lake and Watershed Management Plan and presented to the Moorestown Township Council’s environmental committee as one of a number of immediate actions needed in order to restore the pond, preserve the health of the watershed, and reduce impacts to Strawbridge Lake. Dredging, often used as an efficient solution for sediment removal, can expeditiously restore the waterway to its original depth and condition while also removing dead vegetation, pollutants, excess nutrients, and trash that may have accumulated.
Moorestown Township Council awarded contracts to Princeton Hydro for the dredging and cleanup of the Children's Pond, which was an important part of the previously mentioned Watershed Management Plan for Strawbridge Lake.
Before the dredging could begin, a variety of surveys, field investigations, and data collection activities took place at the project site. A bathymetric survey is a critical component of any dredging project because it measures the depth of a waterbody, as well as maps the underwater features of a waterbody.
Due to the small area and shallow depths of Children’s Pond, the survey was conducted using a calibrated sounding rod and a Trimble GPS unit. The calibrated sounding rod was lowered into the water until it reached the top of the accumulated sediment. The location of the sample point and the water depth was then recorded with the GPS unit. Next, the pole was pushed down into the sediment until the point of refusal, and the bottom of sediment elevation was also recorded with the GPS unit. Data was collected from shoreline to shoreline at 25-foot transect intervals.
The data collected via the bathymetric survey, as well as the site survey, field investigations, and soil analysis, was used to shape the project’s engineering design and construction plans.
With the data collection process complete, Princeton Hydro was able to finalize the engineering plans and obtain all necessary permits for the project. Once the project commenced, Princeton Hydro oversaw the construction process and documented the project's progress through Daily Field Reports (DFRs).
DFRs act as a living record of the project and provide the project’s key stakeholders with full details of the team's daily performance and productivity, including arrival and departure times, the weather and temperature, equipment utilized on-site that day, a description of the work completed, and photographs of the work in progress.
This photo from the DFR on March 2, 2020 documents the beginning of excavation work in Children’s Pond:
This photo from the DFR on April 16, 2020 shows grading being completed on the west side of Children’s Pond:
This photo from the DFR on April 20, 2020 documents the continuation (and near completion) of the excavation and grading work:
Princeton Hydro provides construction oversight services to private, public, and nonprofit clients for a variety of ecosystem restoration, water resource, and geotechnical projects across the Northeast. For more information, go here. And, to get an inside look at all that construction oversight entails, check out our blog:
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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.
Hydrology is the study of the properties, distribution, and effects of water on the Earth’s surface, in the soil and underlying rocks, and in the atmosphere. The hydrologic cycle includes all of the ways in which water cycles from land to the atmosphere and back. Hydrologists study natural water-related events such as drought, rainfall, stormwater runoff, and floods, as well as how to predict and manage such events. On the application side, hydrology provides basic laws, equations, algorithms, procedures, and modeling of these events.
Hydraulics is the study of the mechanical behavior of water in physical systems. In engineering terms, hydraulics is the analysis of how surface and subsurface waters move from one point to the next, such as calculating the depth of flow in a pipe or open channel. Hydraulic analysis is used to evaluate flow in rivers, streams, stormwater management networks, sewers, and much more.
Combined hydrologic and hydraulic data, tools, and models are used for analyzing the impacts that waterflow - precipitation, stormwater, floods, and severe storms - will have on the existing infrastructure. This information is also used to make future land-use decisions and improvements that will work within the constraints of the hydrologic cycle and won’t exacerbate flooding or cause water quality impairment.
Simply put, hydrologic and hydraulic modeling is an essential component of any effective flood risk management plan.
Eastwick, a low-lying urbanized neighborhood in Southwest Philadelphia, is located in the Schuylkill River Watershed and is almost completely surrounded by water: The Cobbs and Darby creeks to the west, the Delaware River and wetlands to the south, and the Schuylkill River and Mingo Creek to the east. The community is at continual risk of both riverine and coastal flooding, and faces an uncertain future due to sea level rise and riverine flooding exacerbated by climate change.
Princeton Hydro, along with project partners KeystoneConservation and University of Pennsylvania, conducted an analysis of Eastwick, the flood impacts created by the Lower Darby Creek, and the viability of several potential flood mitigation strategies.
Flood mitigation approaches can be structural and nonstructural. Structural mitigation techniques focus on reconstructing landscapes, including building floodwalls/seawalls and installing floodgates/levees. Nonstructural measures work to reduce damage by removing people and property out of risk areas, including zoning, elevating structures, and conducting property buyouts.
For Eastwick, studying stream dynamics is a key component to determining what type of flood mitigation strategies will yield the most success, as well as identifying the approaches that don’t work for this unique area.
Princeton Hydro’s study focused on the key problem areas in Eastwick: the confluence of Darby Creek and Cobbs Creek; a constriction at Hook Road and 84th Street; and the Clearview Landfill, which is part of the Lower Darby Creek Superfund site. Additionally, the study sought to answer questions commonly asked by community members related to flooding conditions, with the main question being: What impact does the landfill have on area flooding?
The built-up landfill is actually much higher than the stream bed, which creates a major disconnection between the floodplain and the stream channel. If the landfill didn’t exist, would the community still be at risk? If we increased the floodplain into the landfill, would that reduce neighborhood flooding?
Princeton Hydro set out to answer these questions by developing riverine flooding models primarily using data from US Army Corps of Engineers (USACE), Federal Emergency Management Agency (FEMA), The National Oceanic and Atmospheric Administration (NOAA), and NOAA's National Weather Service (NWS). FEMA looks at the impacts of 1% storms that are primarily caused by precipitation events as well as coastal storms and storm surge. NOAA looks at the impacts of hurricanes. And, NOAA's NWS estimates sea, lake and overland storm surge heights from hurricanes.
The models used 2D animation to show how the water flows in various scenarios, putting long-held assumptions to the test.
The models looked at several different strategies, including the complete removal of the Clearview Landfill, which many people anticipated would be the silver bullet to the area’s flooding. The modeling revealed, however, that those long-held assumptions were invalid. Although the landfill removal completely alters the flood dynamics, the neighborhood would still flood even if the landfill weren’t there. Additionally, the modeling showed that the landfill is actually acting as a levee for a large portion of the Eastwick community.
Ultimately, the research and modeling helped conclude that for the specific scenarios we studied, altering stream dynamics – a non-structural measure – is not a viable flood mitigation strategy.
The USACE is currently undergoing a study in collaboration with the Philadelphia Water Department to test the feasibility of a levee system (a structural control measure), which would protect the Eastwick community by diverting the flood water. Funding for the study is expected to be approved in the coming year.
There are many studies highlighting flood mitigation strategies, environmental justice, and climate change vulnerability in Eastwick. Princeton Hydro Senior Project Manager and Senior Ecologist, Christiana Pollack CFM, GISP, presented on the flooding in Eastwick at the Consortium for Climate Risk in the Urban Northeast Seminar held at Drexel University. The seminar also featured presentations from Michael Nairn of the University of Pennsylvania Urban Studies Department, Ashley DiCaro of Interface Studios, and Dr. Philip Orton of Stevens Institute of Technology.
For more information about Princeton Hydro’s flood management services, go here.
Sinkholes can be quite terrifying. We see them on the news, on television and in movies seemingly appearing out of nowhere, swallowing up cars and creating calamity in towns across the world. In this two-part blog series, our experts uncover the mystery around sinkholes and arm you with the facts you need to make them less scary.
In part one of the blog series, we discuss what a sinkhole is, three different types of sinkholes, and what causes them to form. In this second part, we explore how to detect sinkholes, what to do if you detect a sinkhole, and the steps taken to repair them.
Not all sinkholes are Hollywood-style monstrosities capable of swallowing your whole house. But even a much smaller, less noticeable sinkhole can do its fair share of harm, compromising your foundation and damaging utilities.
Although sinkholes can be scary to think about, you can take comfort in knowing there are ways to detect them, both visually and experimentally. Often, you can spot the effects of a developing sinkhole before you can spot the hole itself. If you live in an area with characteristics common to sinkhole formation (i.e. “karst terrain,” or types of rocks that can easily be dissolved by groundwater), there are some things you can do to check your property for signs of potential sinkhole formation.
According to the American Society of Home Inspectors, there are key signs you should be on the lookout for in and around your home:
If you spot any of the signs listed above, or you suspect that you have a sinkhole on or near your property, you should contact your township, public works, or the local engineering firm that represents your municipality right away. If you have discovered a sinkhole that is threatening your house or another structure, be sure to get out immediately to avoid a potentially dangerous situation.
If you’re trying to determine whether or not you have a sinkhole on your property, there are a few physical tests that can be conducted to determine the best course of action.
Electro-resistivity testing: This extremely technical test can best be summed up by saying it uses electrodes to determine the conductivity of the soil. Since electricity can’t pass through air, this test shows any pockets where the current didn’t pass through. This is a fairly accurate way to determine if there is a sinkhole and where it is.
Micro-gravity testing: Another incredibly technical method, this test uses sensors that detect the measure of gravity. Since the gravitational pull in a given area should be the same, you can see if there are minute differences in the measurement. If there is a difference, then it’s likely that you have a sinkhole in that area.
If you are still unsure whether or not you live in a sinkhole risk area, you can check with your local, territorial, or national government offices; review geological surveys such as the United States Geological Survey (USGS); and contact an expert.
There are three main techniques experts utilize to repair sinkholes. The type of sinkhole and landowner's aesthetic preferences determine the methodology used to repair the sinkhole.
Our engineers regularly go out in the field to oversee and inspect sinkhole repairs. If you detect a sinkhole, or what might be a sinkhole, on your property, our experts strongly advise immediate actions be taken. Ignoring a sinkhole will only cause it to get larger and more dangerous as time passes, and putting topsoil over a sinkhole will only exacerbate the symptoms.
While there’s really no way to prevent a sinkhole, you can never be too prepared! Here are three easy steps you can take to determine if you live in or around a sinkhole-prone area and what to do in the event of a surprise sinkhole:
Although scary, sinkholes are a manageable threat if you’re informed and prepared. After all, it is possible to do something about sinkholes – if they can be detected in time.
Special thanks to Princeton Hydro Staff Engineer Stephen Duda, Geologist Marshall Thomas, and Communications Intern Rebecca Burrell for their assistance in developing this blog series.
Sinkholes are a phenomenon that tend to baffle and frighten most people. How is it possible that the ground beneath our feet could just drop? How do we know if we’re nearby a sinkhole? What should we do if we see one? How are sinkholes fixed? The mystery of the unknown around sinkholes can be quite unnerving.
Have no fear, we’ve got answers to all of those questions and more! In this two-part blog series, our experts share their knowledge and provide important information about this scary occurrence. In part one, we provide a detailed look at what a sinkhole is, three different types of sinkholes, and what causes them to form. In part two, we explore how to detect sinkholes and the steps taken to repair them.
Sinkholes are a common phenomenon around the world. They result from both man-made and natural causes. Marshall Thomas, a Princeton Hydro geologist, describes sinkholes as “depressions observed from the surface, caused by dissolution of carbonate rocks.” In other words, sinkholes form when the rock below the land surface gets dissolved by water that penetrates the surface and continues to move downward, further into the subsurface.
Most common in areas with “karst terrain,” or types of rocks that can easily be dissolved by groundwater, sinkholes can go undetected for years until the space underneath the surface gets too big or enough of the surface soil is washed away. Sometimes the holes are small, measuring a few feet wide and ten feet deep. Sometimes the holes are hundreds of miles wide and deep. However, all of them can be dangerous.
Sinkholes are found throughout the world. States like Pennsylvania, Texas, Florida, Alabama, Tennessee, and Missouri are at higher risk for sinkholes because they tend to have more soluble rocks like salt beds and domes, gypsum, limestone, and other carbonate rocks. People living in these states are recommended to have professionals look at any property they intend to buy to make sure it isn’t in an area above soluble rock.
Not all sinkholes are the scary, earth-falling-out-from-underneath-your-feet events. Some occur slowly over time and are very evident from the surface. Geologists classify sinkholes in three major types. Their formation is determined by the same geological processes, barring a few differences. Let's dive in!
Dissolution sinkholes start to form when limestone or dolomite is very close to the soil surface, usually covered by a thin layer of soil and permeable sand which washes away or is eroded. Rain and stormwater runoff gradually percolate through crevices in the rock, dissolving it. Consequently, a bowl-shaped depression slowly forms.
Sometimes, dissolution sinkholes become ponds when the depression gets lined with debris, which traps water inside. Dissolution sinkholes develop gradually and are normally not dangerous. However, the ones that become ponds can drain abruptly if water breaks through the protective bottom layer.
2. Cover-Subsidence Sinkholes
This type of sinkhole, which starts with the dissolution of the underlying carbonate bedrock, occurs where the covering sediment is permeable (water can pass through it) and contains sand. First, small pieces of sediment split into smaller pieces and fall into openings in the carbonate rock underneath the surface. With time, in a process called piping, the small particles settle into the open spaces. This continues, eventually forming a dip in the surface ranging from one inch to several feet in depth and diameter. Again, these aren’t the sinkholes movies are made about.
3. Cover-Collapse Sinkholes
This type of sinkhole is the one making headlines and causing fear. In order for cover-collapse sinkholes to happen, the covering soil has to be cohesive, contain a lot of clay and the bedrock has to be carbonate. Similar to the cover-subsidence sinkholes, the cohesive soil erodes into a cavity in the bedrock. The difference with this is that the clay-filled top surface appears to remain intact from above. However, underneath, a hollowed out, upside down bowl shape forms. That hollowing gets bigger and bigger over time until eventually, the cavity reaches the ground surface, causing the sudden and dramatic collapse of the ground. Just like that, poof, we have a sinkhole that appears to be surprising and abrupt but really has been brewing for many years.
Sinkholes can be natural or man-made. The most common causes of a sinkhole are changes in groundwater levels or a sudden increase in surface water.
Intensive rain events can increase the likelihood of a sinkhole collapse. Alternatively, drought, which causes groundwater levels to significantly decrease, can also lead to a greater risk of collapse of the ground above. In a world with a greater variability in rainfall and drought events due to climate change, sinkholes may become a more common occurrence around the world.
Humans are also responsible for the formation of sinkholes. Activities like drilling, mining, construction, broken water or drain pipes, improperly compacted soil after excavation work, or even significantly heavy traffic (heavy weight on soft soil) can result in small to large sinkholes. Water from broken pipes can penetrate through mud and rocks and erode the ground underneath and cause sinkholes.
In some cases, human-induced sinkholes occur when an already forming sinkhole is encountered during construction processes such as excavation for stormwater basins and foundations. Dissolution of bedrock generally occurs in geologic time-frames (thousands of years). In these cases, the excavation process has removed the covering soils, decreasing the distance between the top of the void and the ground surface.
In other cases, voids in the bedrock are generated due to rock removal processes such as hammering and blasting. Hammering and blasting can generate fractures or cracks in the bedrock that soil can then erode into. A void in the bedrock may already exist, however, the process of removing the bedrock by hammering and/or blasting can speed up the meeting of the upside-down bowl and the surface that much quicker. One site where this happened has experienced over 35 sinkholes in 4 years.
Overall, it’s generally not a good idea to pump groundwater or do major excavation in areas that are prone to sinkholes. According to the USGS, over the last 15 years sinkhole damages have cost on average at least $300 million per year. Because there is no national tracking of sinkhole damage costs, this estimate is probably much lower than the actual cost. Being more mindful about the subsurface around us and our actions could help lower the average yearly cost in damages and even save lives.
Stay tuned for Part Two of this blog series in which we explore we explore how to detect sinkholes and the steps taken to repair them! For more information about Princeton Hydro’s Geotechnical Engineering services, click here.
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