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In urban areas, streams have often been buried beneath streets, buildings, and infrastructure, cutting them off from the natural ecosystem. However, a growing movement towards "daylighting" streams—uncovering and restoring these buried watercourses—has proven to be an innovative solution for improving water quality, reducing flood risks, restoring fish passage, and creating healthier habitats. Princeton Hydro has been at the forefront of these efforts, bringing expertise in ecological restoration and water resource management to daylighting projects across New Jersey.
Daylighting is the process of removing obstructions and impervious surfaces from a buried stream or river, restoring it to a more natural state. Often, streams were diverted underground to make way for urban development. Daylighting involves reversing this process, bringing the water flow back above ground where it can interact with the natural environment. The result is a newly visible, revitalized waterway that reconnects the stream to its surrounding ecosystem. This process not only improves stormwater management but also enhances urban spaces and promotes healthier habitats.
Daylighting streams offers numerous advantages to both the environment and local communities. Some key benefits include:
Princeton Hydro has successfully completed numerous daylighting projects that demonstrate the transformative power of restoring natural waterways. By leveraging innovative engineering and ecological practices, these projects restored the natural flow of waterways and enhanced the surrounding landscape. Let’s take a closer look at two examples:
In the heart of Trenton, NJ, Princeton Hydro undertook a comprehensive stream restoration. The City of Trenton, as part of a larger urban revitalization and brownfield redevelopment project, sought to restore the stream, Petty’s Run, which had long suffered from typical urban afflictions: pollution, flooding, and heavy debris accumulation.
Princeton Hydro developed a green infrastructure design that addressed these challenges holistically. The design included removing from the stream channel heavy debris, contaminated soils, and the concrete remains of previous development. The team also replaced the restrictive upstream road crossing with a pedestrian bridge, enhancing both the stream’s flow and the community’s connectivity. A significant aspect of the project involved daylighting the 250-foot underground portion of Petty’s Run, restoring it to a natural, open flow while creating an adjacent floodplain meadow to manage stormwater and provide habitat.
The project improved stormwater management, enhanced the landscape’s biodiversity, added habitat value, and established a new public green space with walking trails, which now serves as both an ecological asset and a recreational area for the community. This project earned both the Phoenix Award for Brownfield Redevelopment and the Bowman’s Hill Land Ethics Award.
Thompson Park, a sprawling 675-acre recreational area in Middlesex County, NJ, boasts a variety of amenities, including hiking trails, ballfields, and a zoo that is home to over 50 geese and fowl, goats, and approximately 90 deer. The streams within the park faced challenges, particularly in the areas surrounding the zoo’s enclosures, including erosion and compromised water quality.
In order to increase channel stability, decrease erosion, improve water quality and ecological function, and reduce the 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, New Jersey Department of Environmental Protection, South Jersey Resource Conservation and Development Council, Middlesex County Mosquito Extermination Commission, Freehold Soil Conservation District, Rutgers Cooperative Extension, Enviroscapes and Princeton Hydro worked together to fund, design, permit, and construct numerous stormwater management measures within Thompson Park.
One of the key project initiatives involved daylighting a section of a 24-inch reinforced concrete pipe (RCP) that had previously conveyed stormwater underground. Daylighting the stream, widen the stream channel, improved stormwater absorption, reduced erosion, helped restore the stream’s natural gradient, and improved aquatic habitat.
This multi-faceted restoration project improved stream function and created a more sustainable environment for both zoo inhabitants, the park’s visitors, and the watershed.
Princeton Hydro’s President and Founding Principal, Geoffrey M. Goll, PE, recently shared his expertise in stream restoration during a "Daylighting Streams: Design & Engineering" webinar hosted by The Watershed Institute. The webinar explored the process of uncovering and restoring buried watercourses. Moderated by Susan Bristol, The Watershed Institute Municipal Policy Specialist, the webinar featured experts Vince Sortman, Biohabitats Senior Fluvial Geomorphologist; Warren T. Byrd, Jr., FASLA, Founding Partner of Nelson Byrd Woltz Landscape Architects & Professor Emeritus, University of Virginia; and Geoffrey. The webinar provided valuable insights into the challenges and benefits of these projects, highlighting the importance of hazard mitigation, maintenance, and community involvement in successful daylighting initiatives. The event underscored the significance of daylighting in enhancing both urban infrastructure and natural ecosystems.
Daylighting streams is a forward-thinking approach to urban water management that brings immense benefits to the environment and local communities. As daylighting continues to gain recognition as an essential tool for watershed restoration, Princeton Hydro remains a trusted leader in the field, combining innovative design with environmental stewardship.
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.
In the late 1920s, the U.S. government began allocating funds for road construction in U.S. national forests. This led to hundreds of thousands of culverts being built and installed across the country for the purpose of moving water quickly and efficiently underneath the roadways to prevent flooding, minimize erosion, and provide pathways for stormwater.
However, culverts have had an unintended and significant consequence: they block the migration routes of some fish and aquatic organisms.
Culverts that are undersized, improperly placed, or designed with smooth featureless surfaces can impede or totally block fish and aquatic species from passing. Culverts with extremely high velocity flows make it incredibly difficult for aquatic organisms to navigate upstream, and extremely low velocity flows make it hard for fish to pass in either direction. The high-velocity flows can erode the stream channel immediately downstream of the culvert, which can leave the culvert pipe perched. This elevation above the water channel makes it impossible for organisms to pass through. Debris can also collect in the culvert, not only blocking fish passage, but water as well.
In addition to blocking the upstream passage of fish and other aquatic species, some culverts disrupt the normal stream movements of some macroinvertebrates, which are key components of these stream ecosystems, an important food source to countless species, and play a critical role in the cycling of energy and nutrients throughout stream ecosystems. Disruptions to the movement and dispersal of stream macroinvertebrates can reduce available habitat, lead to genetic isolation of some populations, and cause extirpation of critical species. When populations splinter, it causes a reduction in genetic diversity, which can lead to the spread of more invasive species and many other ecological issues.
While culverts serve an important function in road construction and flood prevention, their impact on aquatic organisms must be taken into consideration. Finding solutions that both allow for efficient water flow and enable safe aquatic migration is crucial in preserving the health of our waterways and their ecosystems.
A shift in the 1980s recognized the importance of redesigning road-stream crossings for several reasons, including restoring aquatic organism passage and maintaining flood resilience. Between 2008 and 2015, U.S. Forest Service (USFS) partnered with more than 200 organizations in the Legacy Roads and Trails Program to replace 1,000+ culverts across the country. The aim of the program was to upgrade culverts to emulate natural streams and to allow fish and wildlife to pass more naturally both upstream and downstream.
Replacing culverts with structures that better facilitate the movement of both water and aquatic organisms has benefits beyond restoring critical ecosystems and improving biodiversity. Ecological restoration creates jobs, stimulates outdoor recreation and local economic activity, and generates long-term economic value.
Princeton Hydro has a strong history in designing connectivity-friendly road-stream crossings and restoring/replacing outdated culverts. Our team of engineers and scientists has been directly involved with hundreds of stream and ecosystem restoration projects throughout the Northeast.
For several years, Princeton Hydro has partnered with NY-NJ Harbor & Estuary Program (HEP) to plan and design for aquatic connectivity through climate-ready infrastructure. Created by the U.S. Environmental Protection Agency (USEPA) at the request of the governors of New York and New Jersey, HEP develops and implements plans that protect, conserve and restore the estuary, and aquatic connectivity is a key focus area for HEP and its partners.
Most recently, HEP partnered with Princeton Hydro to address hydraulic capacity issues at priority road-stream crossings in New Jersey’s South River and Lower Raritan River watersheds. The Princeton Hydro team developed a 30% engineering plan for a priority road-stream crossing – the Birch Street crossing over the Iresick Brook in Old Bridge, NJ.
Iresick Brook is upstream from Duhernal Lake, located at the end of the free-flowing South River, which feeds into the Raritan River, and ultimately flows into Raritan Bay. Duhernal Lake is dammed at the outlet so there is little to no connectivity downstream from the Iresick Brook sub-watershed. The watershed is highly dendritic (meaning the drainage pattern follows a tree-like shape) with many small streams running through it, some of them ephemeral.
The Iresick Brook 5 (IB5) culvert, located in Old Bridge Township, New Jersey, is an undersized double culvert in poor condition with an eroding streambank. This culvert was chosen as a restoration priority primarily due its inadequate sizing (both pipes are only 3-feet in diameter). The outdated infrastructure blocks the passage of fish and other aquatic organisms, and it can only accommodate a 50-year storm event.
Once the IB5 culvert was identified as the priority site, Princeton Hydro completed a site investigation, which included a geomorphic assessment, site observations, and simplified site survey of the channel alignment, profile, and cross sections both upstream and downstream of the culvert.
At the time of the survey, flow was only a couple inches deep in the channel and incredibly slow-moving, especially in the upstream reach. Despite the low flow at the time of the survey, during storm events, the stream experiences extremely high velocities. The undersized culvert creates hydraulic constriction and subsequently a velocity barrier that prevents passage. Additionally, when the high-flow stream water is forced through the small pipes, it creates a firehose effect, which has led to the formation of a 60-foot-long scour hole at the culvert outlet. Substrate from the scour hole has been washed downstream, forming an island of large sand and small gravel.
Approximately 155 feet upstream of the culvert is a channel-spanning v-notch weir comprised of a combination of sheet pile and timber. The weir appears to be a historical stream gauge that is highly degraded and creates an artificially perched channel. The upstream channel also contains woody debris, which gets caught at the culvert, blocking water flow and organism passage.
For the design process, Princeton Hydro used the USFS Stream Simulation Design, an gold-standard ecosystem-based approach for designing and constructing road-stream crossings that provide unimpeded fish and other aquatic organism passage through the structure. The Stream Simulation, a required standard on USFS road projects, integrates fluvial geomorphology concepts and methods with engineering principles to design a road-stream crossing that contains a natural and dynamic channel through the structure so that fish and other aquatic organisms will experience no greater difficulty moving through the structure than if the crossing did not exist.
The design also incorporated utility constraints (gas line, sewer line, drinking water main, and stormwater outlet), a longitudinal profile assessment, channel capacity and slope analysis, and a simplified hydrologic & hydraulic assessment.
Ultimately, Princeton Hydro recommended that HEP replace the existing culvert with a Contech Precast O-321 culvert, or similar alternative. The proposed design increases the culvert opening area and allows for significant increases in flow capacity. This culvert replacement project has the potential to reduce local flood risk and restore aquatic organism passage to the reach of Iresick Brook.
Aquatic connectivity is crucial for improving healthy aquatic ecosystems and managing severe storms and flooding. Increases in rainfall due to climate change makes investing in these improvements even more of a growing priority. With so many culverts in place, it can be difficult to know which culvert restoration projects to prioritize.
We worked with HEP to create a toolkit for addressing problematic road-stream crossings. The easy-to-use matrix helps to prioritize potential projects and identify solutions for problem culverts and relative cost solutions.
The toolkit was just recently released to the public with the hope that it will be used as a template to promote the development of more resilient and environmentally-friendly infrastructure.
Click here to get more info and download.
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.
Just 50 miles southeast of New York City, tucked between two municipalities, sits a 650+ acre tidal salt marsh which spans the shorelines of the South River in densely populated, highly developed Central New Jersey. The South River is the first major tributary of the Raritan River, located 8.3 miles upstream of the Raritan River’s mouth, which drains into Raritan Bay.
The Lower Raritan River and Raritan Bay make up a large part of the core of the NY-NJ Harbor and Estuary Program. Within the Raritan Estuary, the South River wetland ecosystem is one of the largest remaining wetland complexes. While the South River salt marsh ecosystem has been spared from direct development, it has been degraded in quality, and does not provide optimal habitat for wildlife or maximum flood protection for residents. This area is subject to fairly regular tidal flooding (particularly when it occurs simultaneously with a storm) and periodic—generally more severe—flooding during more significant events such as nor’easters and tropical storms. Hurricanes Irene and Sandy caused damage in the Boroughs of Sayreville and South River too.
In 2018, Princeton Hydro and Rutgers University, along with the Lower Raritan Watershed Partnership, Middlesex County, Borough of Sayreville, Borough of South River, NY/NJ Baykeeper, Raritan Riverkeeper, and the Sustainable Raritan River Initiative, secured funding from NFWF’s National Coastal Resilience Fund for the “South River Ecosystem Restoration & Flood Resiliency Enhancement Project.”
The South River Ecosystem Restoration and Flood Resiliency Enhancement Project aims to:
Reduce socioeconomic damages to the Boroughs of South River and Sayreville caused by storm damage, flooding, and sea level rise;
Transform degraded wetlands to high-quality marsh that can reduce flooding and enhance fish & wildlife habitat; and
Engage stakeholders in activities about coastal resilience and ecological health to maximize public outreach in the Raritan River Watershed.
For this 165-acre tidal marsh and transitional forest “eco-park,” the project team is conducting an ecosystem restoration site assessment and design. This phase of the coastal restoration project will result in a permit-ready engineering design plan that stabilizes approximately 2.5 miles of shoreline, reduces flood risk for smaller coastal storms, and enhances breeding and foraging habitat for 10 state-listed threatened and endangered avian species.
This area has experienced repeated flooding, especially during large storms. For example, coastal areas of Sayreville and South River flooded after Hurricane Floyd (1999), Tropical Storm Ernesto (2006), Hurricane Irene (2011), and Hurricane Sandy (2012). Over the last century, there have been several studies and assessments completed for the South River, many of which identify this project area as a priority location for flooding improvements. The following are key reports and studies published about the project area and surrounding communities:
NJ Legislature’s 71st Congress published a report, “Basinwide Water Resource Development Report on the Raritan River Basin” which focused on navigation and flood control for the entire Raritan River Basin. It discussed recommendations for flood control and local storm drainage, setting the stage for future actions.
NJDEP Division of Water Resources published Flood Hazard Reports for the Matchaponix Brook System and Raritan River Basin, which delineated the floodplains in the South River, and its tributaries, the Manalapan Brook and Matchaponix Brook.
USACE New York District released a “Survey Report for Flood Control, Raritan River Basin,” which served as a comprehensive study of the Raritan River Basin and recommended several additional studies. Although the South River was studied, none of the proposed improvements were determined to be economically feasible at that time.
Project area was listed as one of the Nation’s Estuaries of National Significance.
USACE conducted a multi-purpose study of this area. This preliminary investigation identified Federal interest in Hurricane and Storm Damage Reduction and ecosystem restoration along the South River and concluded that a 100-year level of structural protection would be technically and economically feasible.
USACE NYD and NJDEP released a joint draft, “Integrated Feasibility Report and Environmental Impact Statement” for the South River, Raritan River Basin, which focused on “Hurricane & Storm Damage Reduction and Ecosystem Restoration.” Because it was previously determined that there were no widespread flooding problems upstream, the study area was modified to focus on the flood-prone areas within the Boroughs of Sayreville and South River, as well as Old Bridge Township.
Through collaboration with our project partners and following input provided from a virtual stakeholder meeting held in December 2020, Princeton Hydro developed a conceptual design for an eco-park that incorporates habitat enhancement and restoration, and protective measures to reduce impacts from flooding while maximizing public access and utility. Public access includes trails for walking and designated areas for fishing. The eco-park can also be used for additional recreation activities such as bird watching and kayaking.
Highlights of the conceptual design include the following features:
Approximately two miles of trails with overlook areas, connection to fishing access, and a kayak launch.
~3,000 linear feet of living shoreline, located along portions of the Washington Canal and the South River, to provide protection from erosion, reduce the wake and wave action, and provide habitat for aquatic and terrestrial organisms.
~60 acres of enhanced upland forest to provide contiguous habitat areas for resident and migratory fauna.
A tidal channel that will connect to the existing mud flat on the southeastern part of the site and provide tidal flushing to proposed low and high marsh habitats along its banks.
A vegetated berm with a trail atop will extend the length of the site to help mitigate flood risk.
Two nesting platforms for Osprey, a species listed as “Threatened” in NJ
Designated nesting habitat for the Diamondback Terrapin, a species listed as “Special Concern” in NJ
Princeton Hydro specializes in the planning, design, permitting, implementing, and maintenance of ecological rehabilitation and floodplain management projects. Click here to read about a coastal rehabilitation and resiliency project we completed in New Jersey.
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.
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