Two Dams Removed in the Hudson River Watershed

The Hudson River provides habitat for approximately 85% of New York State’s fish and wildlife species, 200 of which rely on the Hudson River for spawning, nursery, and forage habitat. According to Riverkeeper, a nonprofit focused on protecting and restoring the Hudson River, there are approximately 1,600 dams, mostly obsolete, fragmenting the rivers and streams of the Hudson Valley and blocking fish from reaching critical habitat.

The recent removal of two defunct dams – The Strooks Felt Dam and Furnace Brook Barrier #1 – marks an important milestone in the Riverkeeper’s journey to “Undam the Hudson River” and restore fish passage between the Hudson and the Atlantic Ocean. 

The removal of these dams, located on tributaries of the Hudson River, are especially important to depleted populations of migratory fish like river herring and American eel, who are a vital part of the coastal ecosystem and spawn in freshwater tributaries. 

Funding for both projects was provided by the Environmental Protection Fund and administered by the Department of Environmental Conservation (DEC). Riverkeeper led the effort to remove the obsolete dams, with Princeton Hydro providing dam and stream assessment, surveying, engineering design, and permitting assistance. 


Strooks Felt Dam

For the first time in 300 years, fish in the Quassaick Creek will be able to move upstream thanks to the dismantling of the 106-year-old, 4-foot-high Strooks Felt Dam in Newburgh, New York, located 60 miles north of New York City in the critical estuary of the Hudson River. 

The dam site was dominated by gravel, cobble, boulder, and even bedrock steps, indicating a high-energy stream with a high sediment transport potential. This dam removal, like many others, released this coarse sediment and allowed the creek to carry it to downstream reaches. This coarse sediment forms habitat features like riffes, bars, and pools that are crucial components of healthy streams and rivers. Releasing the impounded bedload by removing these dams is key to increasing the resilience of freshwater streams like Quassaick Creek. 

Downstream of spillway facing west

The dam removal, which was completed in October 2020, involved excavating the concrete spillway before reshaping and re-grading bedload sediment behind the dam.

Historically, the Strooks Felt Dam was part of a series of older dams that sat in slightly different positions in the same area and supplied former mill operations. Other nonobstructive structures associated with the former mill were left as part of an enduring history, allowing anyone who visits the site or combs through the records to visualize what was there before. The obsolete dam, however, will no longer block water, sediment, or critical fish passage

Project collaborators included: Riverkeeper, Orange County and the City of Newburgh, the Town of New Windsor, DEC Hudson River Estuary Program, Quassaick Creek Watershed Alliance, Steelways Inc, RiverLogic Solutions, and Princeton Hydro. 

Two additional dams farther upstream from the former Strooks Felt Dam site are in the early planning stages for removal.

 


Furnace Brook Barrier #1

The 5-foot-high, 75-foot-long Furnace Brook Barrier #1 was dismantled in Westchester County, New York in mid-November 2020. The removal of this dam brings migratory fish one-step closer to reconnecting with their ancestral habitat.

Furnace Brook Dam removal. Photo courtesy of RiverKeeper.

The positive results were immediate. Riverkeeper stated in a recently published article, “As soon as a path was cleared, we spotted two fish – white suckers, a freshwater species – darting up to the previously unreachable part of the brook. We can’t wait to come back in the spring and see whether herring, returning from the ocean, are migrating upstream…”

The dam clearing process at Furnace Brook involved the removal of the dam and an existing collapsed former concrete bridge span downstream of the dam. Stone masonry boulders from the former spillway were then redistributed and partially embedded in the restored channel to enhance aquatic habitat and increase bank stabilization

Project collaborators included Rivekeeper, NYSDEC’s Hudson River Estuary Program, Westchester County Parks Department, Westchester County, the dam owner, the town of Cortlandt, the Friends of the McAndrews Estate, and Princeton Hydro. 

Upstream of this project, Princeton Hydro is developing an initial engineering design and sediment management plan for the removal of another, larger dam.

The collapsed concrete bridge deck was also removed as part of this project.

 

Princeton Hydro has designed, permitted, and overseen the reconstruction, repair, and removal of dozens of small and large dams throughout the Northeast. To learn more about our dam engineering and removal services, visit: bit.ly/DamBarrier.

Year in Review: Top 10 Successes of 2020

Princeton Hydro has grown from a small, four-person firm operating out of a living room to a 60+ person business with six office locations in the Northeast and a satellite office in Colorado. Over the last two decades, we’ve restored many miles of rivers, improved water quality in hundreds of ponds and lakes, and enhanced thousands of acres of ecosystems in the Northeast.

This year, we are feeling extra grateful for those who have supported our business and helped us further our mission during these difficult times. As we reflect on 2020 and set our sights on 2021, we have many successes to celebrate.  Here’s a look at our top 10 successes of the year:

 

1. RESTORED FISH PASSAGE ON SIX WATERWAYS

Our team installed one fish ladder and oversaw the removal of five dams in four states. In New York, in partnership with Riverkeeper, Princeton Hydro oversaw the removal of two dams on tributaries to the Hudson River: Strooks Felt Dam on the Quassaick Creek in Newburgh and Barrier #1 on Furnace Brook in Cortlandt. The dams were the first barriers for fish movement upstream from the Hudson River. In Connecticut, the Slocomb Dam along Roaring Brook in South Glastonbury was removed, restoring American eel and trout passage. In Massachusetts, the Horseshoe Mill Pond Dam in Wareham was removed, opening over 3 miles of fish habitat on the Weweantic River, Buzzards Bay’s largest freshwater river. Here, migratory fish can now swim unimpeded from Buzzards Bay to lay their eggs in fresh water upstream for the first time in 200 years. In New Jersey, we led the removal of Warren Hills Dam in Washington, NJ and partnered with the American Littoral Society to install a fish ladder at the Old Mill Pond Dam in Spring Lake Heights, NJ, which allows migratory fish to scale the dam and access spawning grounds that had been blocked-off for over 100 years.

 


 2. LED THE LARGEST APPLICATION OF PHOSLOCK IN THE NORTHEAST ON NEW JERSEY’S LARGEST LAKE

We implemented a variety of measures that helped Lake Hopatcong, New Jersey’s largest lake, mitigate harmful algal blooms (HABs). We applied a clay-based nutrient inactivating technology called Phoslock, which was the largest Phoslock treatment to occur in the Northeastern US. This treatment along with HAB prevention measures like the installation of biochar bags, nanobubble aeration systems, and floating wetland islands proved successful in mitigating HABs and improving overall water quality in 2020. And to top it all off, The Washington Post was awarded a Pulitzer Prize for its explanatory reporting on a novel climate change story featuring Lake Hopatcong and our lake management work.

 


3.  DESIGNED AND CONSTRUCTED WETLAND AND SHORELINE RESTORATION PROJECTS

We completed a shoreline restoration project at The Dunes at Shoal Harbor, a coastal residential community along the Jersey Shore that was severely impacted by Hurricane Sandy. In Linden’s Tremley Point neighborhood – another New Jersey community ravaged by Hurricane Sandy – we completed a green infrastructure and floodplain restoration project, the first restoration project to ever be implemented on NJDEP Blue Acres-acquired property. We transformed a densely developed, flood-prone, former industrial site in Bloomfield into a thriving public park with 4.2 acres of wetlands. Each of these three projects helped to restore valuable ecological functions and increase storm resiliency.

 


4. LAUNCHED A COMMUNITY SCIENCE MONITORING PROJECT FOR THE SCHUYLKILL RIVER

On World Habitat Day, the nonprofit, Schuylkill River Greenways, in partnership with Berks Nature, Bartram’s Garden, The Schuylkill Center for Environmental Education, Stroud Water Research Center, and Princeton Hydro, kicked-off a Water Quality Monitoring Project for the Schuylkill River. This project aims to document the current ecological health of the river and engage a diverse set of river users and residents. As part of the campaign, the team is recruiting “Community Scientists” to conduct Visual Monitoring Assessments. Additionally, the stakeholder team is implementing water quality sampling and monitoring throughout 2021 at locations along the main stem of the Schuylkill River.

 


5. WELCOMED EIGHT NEW FULL-TIME TEAM MEMBERS

This year, we added eight new full-time staff members and one intern with expertise and qualifications in a variety of fields, all of whom have a passion for water resource management and environmental stewardship. In March, we were thrilled to welcome Dr. Laura Craig to our team as the new Director of Natural Resources. She is an Aquatic Ecologist who has overseen 25 dam removals, co-founded the NJ Dam Removal Partnership, and has 10+ years of experience in river conservation and climate adaptation. Go here to learn about the career opportunities currently available with us.

 


6. COMPLETED A MAJOR ECOLOGICAL STUDY OF THE HUDSON RIVER

Photo from USACE

The USACE Commanding General and 55th U.S. Army Chief of Engineers signed the Hudson River Habitat Restoration Ecosystem Restoration study, designating it as complete and making it eligible for congressional authorization. Princeton Hydro led the Integrated Feasibility Study and Environmental Assessment, which recommends three ecosystem restoration projects at sites along the river including Henry Hudson Park, Schodack Island Park, and Moodna Creek. The Hudson River Estuary is a significant habitat for fish, plants, and other wildlife, and this milestone marks progress toward the river’s return to a dynamic and self-regulating ecosystem. If constructed, these projects would restore almost 24 football-sized fields of wetlands in total.

 


7. EARNED THREE PRESTIGIOUS AWARDS

The New Jersey Section of the American Water Resources Association honored Princeton Hydro with the “Excellence in Water Resources: Ecological Restoration Award” for the Linden Blue Acres Floodplain Restoration & Green Infrastructure project. This restored the ecological and floodplain function on former residential properties acquired by the NJDEP Blue Acres Program for the first time. The American Littoral Society and Princeton Hydro received the “Land Ethics Best Large-Scale Project Award” from Bowman’s Hill Wildflower Preserve for the work they did to restore the health and water quality of the Metedeconk River flowing through Ocean County Park in Lakewood, NJ. The Iowa Court and South Green Living Shoreline Project in Little Egg Harbor and Tuckerton, NJ, for which Princeton Hydro lead the sediment sampling/testing and hydrographic survey, received the “2020 Best Green Project Award” from Engineering News-Record.

 


8. GAVE OVER 20 PRESENTATIONS ON WATERSHED MANAGEMENT & RESILIENCY MEASURES

During the Hudson River Estuary Program’s conference, Christiana Pollack, GISP, CFM presented on managing invasive Phragmites and restoring wetland habitats. And, at the Consortium for Climate Risk in the Urban Northeast, Christiana presented on a flood mitigation analysis project in a flood-prone Philadelphia community. As part of The American Sustainable Business Council’s “Clean Water is Good for Business” campaign, Marketing & Communications Manager, Dana Patterson, led a webinar, titled “Making the Business Case on Clean Water Issues to the Media.” At the 2020 Delaware Wetlands Conference, Senior Project Manager, Michael Rehman, presented a wetland restoration project that illustrates how a degraded urban area can be successfully rehabilitated. And, for a New York State Federation of Lake Associations webinar series, Senior Aquatic Ecologist, Chris Mikolajczyk, CLM, presented on a unique lake management initiative. And, our Director of Aquatics, Dr. Fred Lubnow, joined Rep. Debbie Mucarsel-Powell & other experts to discuss Harmful Algal Blooms at a virtual #ProtectCleanWater Town Hall hosted by the National Wildlife Federation Action Fund.

 


9. CELEBRATED A VARIETY OF STAFF ACHIEVEMENTS

Our staff our repeatedly striving for personal growth and continue to amaze us. North American Lake Management Society chose Chris L. Mikolajczyk, CLM, Senior Aquatic Ecologist as the next President of the Board of Directors. Senior Ecologist, Michael Rehman, PWS, and Fluvial Geomorphologist, Paul Woodworth, became Certified Ecological Restoration Practitioners through the Society for Ecological Restoration. Emily Bjorhus and Robert George earned their Professional Wetland Scientist certification through the Society of Wetland Scientists program. In January, our Marketing & Communications Manager, Dana Patterson, received the Society of American Military Engineers New Jersey Post’s “Young Member Award” for her efforts in maintaining and advancing the objectives of the organization (pictured above). A national science journal published Environmental Scientist, Brittany Smith’s, graduate research study, which assessed “The Ecogeomorphic Evolution of Louisiana’s Wax Lake Delta.” Cory Speroff passed his Landscape Architecture exams and Andrew Simko earned his Professional Engineering license. And, Dr. Clay Emerson won our Earth Day Photo Contest with his incredible close-up of an Eastern Fence Lizard.

 


10. WE STAYED UNIFIED AND CONNECTED

2020 was a particularly challenging year, but the Princeton Hydro family stood together. With offices spread across the Northeast and collaboration between offices on a daily basis, we were unknowingly prepared for the shift to remote work during an unexpected global pandemic. But, it took more than just working laptops and VPN connections to keep us going. Because of our staff’s motivation and dedication to serving our clients, we were able to not only keep our firm open, but we continued to grow our geographic and service reach.

 


Thank you for supporting Princeton Hydro and sharing our stories. We truly appreciate each and every one of our clients, partners, and friends. Cheers to a fruitful 2021 and beyond!

UPDATE: Hudson River Habitat Restoration Study Completed & Chief’s Report Signed

Photo from USACE

As part of the multi-faceted effort to restore the vital Hudson River ecosystem, the USACE New York District launched the Hudson River Habitat RestorationPrinceton Hydro led the Hudson River Habitat Restoration Integrated Feasibility Study and Environmental Assessment for USACE. For this project, we established and evaluated baseline conditions through data collection and analysis; developed restoration objectives and opportunities; prepared an Environmental Assessment; and designed conceptual restoration plans for eight sites.

This week, Lt. Gen. Scott A. Spellmon, USACE Commanding General and 55th U.S. Army Chief of Engineers, signed the Hudson River Habitat Restoration Ecosystem Restoration Chief’s Report, which represents the completion of the study and makes it eligible for congressional authorization.

As stated in the USACE-issued news release, “The Chief’s Report recommends three individual ecosystem restoration projects including Henry Hudson Park, Schodack Island Park, and Moodna Creek within the 125-mile study area from the Federal Lock and Dam at Troy, NY to the Governor Mario M. Cuomo Bridge. These projects would restore a total of approximately 22.8 acres of tidal wetlands, 8.5 acres of side-channel and wetland complex, and 1,760 linear feet of living shoreline with 0.6 acres of tidal wetlands. The plan would also reconnect 7.8 miles of tributary habitat to the Hudson River through the removal of 3 barriers along Moodna Creek.”

“The signing of this Chief’s Report is a significant milestone for the HRHR Project,” said Col. Matthew Luzzatto, USACE New York District Commander. “This has truly been a team effort and I want to thank our non-federal sponsors, New York State Department of Environmental Conservation and New York State Department of State, and all of our engineers, scientists, and partners at the local, state and federal level for their unwavering support.”

Read the full press release here. And, for more background information on the Feasibility Study and proposed restoration work, check out our original blog post:

Feasibility Study Identifies Key Opportunities for Hudson River Habitat Restoration

Engineering Assessment of West Point’s Lower Cragston Dam

Highland Falls, New York, which is 40 miles north of Manhattan, stretches along the Hudson River and is populated by many lakes and ponds, including the Cragston Lakes (a.k.a. Lower Cragston). For the community’s 4,000 residents, living in an area where water is abundant has many benefits, but the benefits are not without flood risk.

The 9-acre Lower Cragston Lake, the second largest lake in the Highland Falls area,   contains the Lower Cragston Dam, which is owned by the United States Military Academy at West Point and managed through the U.S. Army Corps of Engineers New York District (USACE NYD). According to the Office of the New York State Comptroller, Lower Cragston Dam is classified as a “High Hazard” dam. The dam is approximately 10 feet high and 210 feet long, and consists of an earthen embankment with a concrete core wall, a concrete ogee spillway, and a low level outlet.

In order to ensure safety to the surrounding community and mitigate any potential flood risk associated with the dam’s operations, Princeton Hydro was contracted by the USACE NYD to perform an Engineering Assessment for Lower Cragston Dam. Engineering Assessments and periodic safety inspections are intended to provide an independent review of an existing dam structure to ensure that all components are functioning properly and in compliance with current dam safety regulations.

Princeton Hydro utilized a multidisciplinary approach to perform the Lower Cragston Dam Engineering Assessment, which consisted of:

  • Document Review: In order to understand the site and to develop a proper drilling scope and methodology, our team conducted a thorough review of existing documentation, including historic engineering plans, dam inspection reports, and an Emergency Action Plan.
  • Geotechnical and Geophysical Investigation and Reporting: This is one of the most significant aspects of a dam safety evaluation and is often the most efficient means of obtaining critical subsurface information. The information obtained from these field studies is used to devise safety improvements if determined to be necessary.
  • Bathymetric and Topographic Survey: The bathymetric survey entails the accurate mapping of water depths and the quantification of the amount of accumulated, unconsolidated sediment. The topographic survey looks at the height, depth, size, and location of the dam and surrounding area.
  • Hydrologic & Hydraulic Analysis: This analysis looks at the watershed and spillway structure related to the extent of potential flooding from storm recurrence intervals within the study area. The data helps to evaluate measures that can reduce and mitigate existing and anticipated flood risk.
  • Structural Analysis: Our team utilized various methods, to assess the structural integrity of the dam and to evaluate the internal stresses and stability under usual, unusual, and extreme loading combinations.
  • Seepage & Stability Analysis: Seepage through an earthen dam generally correlates with the reservoir water level of the dam. A careful analysis helps to detect any abnormal seepage issues and associated consequences.
  • Dam Break Analysis: This type of analysis is used to estimate the potential hazards associated with a failure of the dam structure and features.

The geotechnical investigation for the Lower Cragston Dam Engineering Assessment involved performing soil borings and rock coring within the dam embankment, for which Princeton Hydro developed a Drilling Program Plan (DPP) to ensure the activities were performed successfully and safely. The DPP, which also required our team to have a comprehensive understanding of bedrock and surficial geologic formations in the area, was ultimately approved by the USACE Dam Safety Officer and successfully executed in the field. The collected samples were tested at Princeton Hydro’s AASHTO accredited and USACE validated soil laboratory.

Ultimately, the geotechnical investigation and subsequent soil analysis were used to inform the slope stability and seepage analysis. The geotechnical analyses, hydrologic & hydraulic study, structural inspection, bathymetry, and dam break analysis were used to provide USACE and West Point with recommendations for repair options, replacement options, and decommissioning options for the dam.

Engineering Assessments are vital to the longevity of dams and the safety of the communities they protect. By providing detailed analysis, effective repair, and management programs can be designed and implemented efficiently. This helps to ensure dam systems are providing the level of protection they were designed to deliver.

Princeton Hydro has designed, permitted, and overseen the reconstruction, repair, and removal of dozens of small and large dams. Our Geoscience and Water Resources Engineering teams perform dam inspections and conduct dam feasibility studies throughout the Northeast. For more info, visit: bit.ly/PHEngineering.

After 100 Years, Fish Passage is Restored at Critical Migratory Fish Spawning Grounds in NJ

Photo by the American Littoral SocietyFor over 100 years, the Old Mill Pond Dam in Spring Lake Heights, New Jersey has blocked critical anadromous fish species from reaching optimal spawning habitat. Today, we are thrilled to announce that, thanks to a fish ladder installed by the American Littoral Society (ALS), migratory fish can now scale the dam and access upstream spawning grounds.

The 60-foot-long fish ladder is a device that allows a channel of water to flow through it and is engineered to create both the proper water depth and velocity for fish to navigate through. In this case, it will enable fish to scale the 10-foot-high dam and go deeper into Wreck Pond Brook.

This video from ALS provides an up-close look at the Alaska-Steeppass Fish Ladder and more details about the project:

Re-opening river passage for migratory species improves not only the health of Wreck Pond Brook and its watershed, but it also benefits the overall ecosystem of the Atlantic shoreline and its coastal rivers. It also supports important recreational and commercial species, such as cod, haddock, and striped bass, which leads to a healthier economy.

For over a century, the dam blocked anadromous fish like Alewife and Blueback river herring, from entering the Wreck Pond Brook Watershed. These fish spend most of their lives in the ocean but need freshwater in order to spawn. The Old Mill Pond Dam, an impassable obstruction for these migrating fish, was identified as a key contributor to the decline of Atlantic coast river herring populations. Subsequently, river herring were classified as National Oceanic and Atmospheric Administration (NOAA) Species of Special Concern and identified as requiring Concentrated Conservation Actions.

Design rendering provided by the American Littoral SocietyThe fish ladder, which was funded through the US Fish and Wildlife Service and implemented by ALS along with a variety of project partners, including Princeton Hydro, is one more major step in the ongoing effort to restore critical migratory fish spawning grounds, support a vibrant food web to the area, and rehabilitate Wreck Pond and its watershed.

According to the ALS, “Now, instead of Old Mill Dam acting as the furthest migration destination for Alewife and Blueback river herring, these fish have the ability to navigate up the dam through the fish ladder and utilize roughly an additional mile of optimal spawning habitat. The ALS will add the Old Mill Dam fish ladder and newly accessible spawning habitat into its ongoing river herring monitoring surveys.”

American Littoral Society promotes the study and conservation of marine life and habitat, protects the coast from harm, and empowers others to do the same. Learn more and get involved: littoralsociety.org.

Princeton Hydro has designed, permitted, and overseen solutions for fish passage including the installation of technical and nature-like fishways and the removal of dozens of small and large dams throughout the Northeast. To learn more about our fish passage and dam removal engineering services, visit: bit.ly/DamBarrier.

Images provided by the American Littoral Society. 

Photo by the American Littoral Society

UPDATE: NJ’s Dunes at Shoal Harbor Shoreline is Restored

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.

Rendering of the shoreline protection design
September 2020
A rendering of the shoreline protection design by Princeton Hydro. A snapshot of Princeton Hydro's completed work in September 2020.

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.

July 2018
September 2020

Princeton Hydro performed a wave attack analysis commensurate with a category three hurricane event and used that data to complete a site design for shoreline protection.

The site design and construction plans included:

  • 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.

These measures will prevent shoreline erosion, protect the community from wave attacks and flooding, and create a stable habitat for native and migratory species.

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:

Conservation Spotlight: Dunes at Shoal Harbor Shoreline Protection

For more information about Princeton Hydro’s engineering services, go here.

Employee Spotlight: Meet Our Two New Team Members

We’re excited to announce the expansion of our growing business with the addition of two new team members who have experience and qualifications in water resource management.

Meet the new team members:

Robert costello, water resource engineer

Robert is a passionately curious water resources engineer who is determined to use his knowledge and experience to provide the best possible outcomes for our clients in every one of his projects. Robert received his degree from the University of Delaware, with a major in Environmental Engineering and a Minor in Civil Engineering. While in school, he was involved heavily in the research conducted at the University’s Water Science and Policy department. After schooling was finished, he used his degree to work on various engineering projects including subsurface geotechnical investigations, hydrologic and hydraulic modeling of water conveyance systems, stormwater BMP design, as well as the complete design, modeling, and supervision of Green Infrastructure Systems.

Outside of work, Robert is an avid outdoor enthusiast. He enjoys kayaking, hiking, and skiing in the Adirondacks during the winter.

Mark Herrmann, PE, CFM, Senior Project Manager, Green Infrastructure & Stormwater Management

Mark is a Civil Engineer and Certified Floodplain Manager with extensive experience in both the public and private sectors. His areas of expertise include stormwater management, hydrologic and hydraulic studies, sustainable design, utility design, and land development. Mark has served as a lead engineer, project manager, and construction manager for a variety of large-scale and small-scale residential land development projects, transportation improvement projects, and utility infrastructure projects. He is passionate about protecting our water supply and our environment and enjoys working on complex, challenging projects that benefit our natural resources.

With four kids at home, Mark does not have much free time. If he does catch a break from the action, you can find him with his head in a book, sitting behind a chessboard, or gazing at the stars and planets through his telescope.

Restoring Ballinger Lake Dam in Medford Lakes, NJ

Medford Lakes is a borough in Burlington County, New Jersey that consists of 22 lakes, and more than 10% of the homes there are log cabins. Located just 25 miles east of Philadelphia, within the New Jersey Pinelands Commission Management Area, the Borough is overseen by the Medford Lakes Colony (MLC), a homeowners association that manages social events and recreation activities for the community and also manages its “Lake Restoration Fund.” All homeowners in the community contribute to the Fund, which is used to manage and monitor lake water quality and maintain water control structures like dams and culverts.

Medford Lakes and its surrounding neighborhoods contain approximately 60 dams. The MLC retained Princeton Hydro to provide various engineering services for multiple dam structures throughout the Borough, including periodic visual inspections, dam breach and inundation analysis, and maintenance and repair work.

Ballinger Lake, located at the intersection of Lenape Trail and Stokes Road, contains a dam that is registered as a Class I – High Hazard Dam with NJDEP Division of Dam Safety. Immediately downstream from the dam is Main Street Medford Lakes, a congested portion of the Medford Lakes Borough.

The dam, originally constructed in the 1920s, is an earthen embankment dam with a clay core. Between 2000 – 2001, a reconstruction project took place that included the creation of both a primary and auxiliary spillway and a concrete culvert. The primary spillway consists of a concrete drop box and culvert that passes through the embankment. The auxiliary spillway, armored with articulated concrete block, is a low point on the embankment along Stokes Road.

In 2008, the Ballinger Lake Dam was inspected by Princeton Hydro and the NJDEP, Division of Dam Safety. The results of these inspections revealed considerable seepage at one of the concrete joints within the concrete culvert, a non-compliant trash rack assembly, a distressed gate valve assembly, and unstable downstream conditions.

Under Princeton Hydro’s direction, the lake was lowered to reduce the hydraulic load on the dam and to facilitate the required remediation and repairs. Princeton Hydro provided full turn-key engineering services that encompassed the development of the engineering documents and plans and preparation of all the permitting requirements (NJDEP Dam Safety, Pinelands Commission Certificate of Filing (CoF), NJDEP Dam Safety Emergency Permit, Burlington County Soil Conservation Erosion and Sediment Control, and NPDES permits). Our team also prepared the contractor bid specifications and provided construction oversight and management throughout the course of the repairs.

Throughout this process, Princeton Hydro completed multiple studies to characterize the hydraulic, hydrologic, structural, stability, geotechnical, and groundwater conditions at the dam under pre and post-repair conditions. The team eliminated the leakage and brought the dam back into compliance.  In 2019, MLC contracted Princeton Hydro to perform additional maintenance and improvements to the Ballinger Lake Dam spillway, outfall, and sluice gate.

The scope of work for the 2019 engineering and construction project included the following:

  • Replacement of the failed sluice gate structure
  • Installation of a baffled culvert extension on the downstream side of the existing culvert
  • Regrading of the downstream embankment to a shallower, uniform 3H:1V slope
  • Regrading of the levee crest to a uniform elevation
  • Riprap armament of the downstream channel
  • Various repairs to joints and spalls within the existing concrete dropbox and culvert structures.

The photo above, taken on September 23, 2019 by Princeton Hydro, shows a view of the lowered lake level and pumping intake hose.

Construction began on September 19, 2019 with the lowering of Ballinger Lake to facilitate the work within the existing dropbox structure. The lake lowering process was performed by a 6-inch centrifugal pump, which discharged water into the downstream channel. The photo above, taken on September 23, 2019, shows a view of the lowered lake level and pumping intake hose. After the lake was lowered below the dropbox crest, all of the concrete was power washed and work began to waterproof and repair all of the joints within the culvert.

The above photo, taken on October 17, 2019 by Princeton Hydro, shows the riprap being removed from the stream bed prior to pouring the flowable fill concrete mud mat.

In October, the team began removing portions of the existing stream bed riprap in preparation for pouring a flowable fill-based mud mat to level the foundation of the culvert extension. The area was dewatered with a submersible pump, with the discharge filtered through a sediment bag and directed back into the downstream channel at a point upstream of the installed turbidity barrier. The above photo, taken on October 17, 2019, shows the riprap being removed from the streambed prior to pouring the flowable fill concrete mud mat.

The above photo taken by Princeton Hydro shows the grate being prepared for the installation of the sluice gate valve operating mechanism.

The installation of the sluice gate valve support structure began in November 2019. Princeton Hydro oversaw the process to ensure the installation was being completed according to the design drawings and NJDEP Dam Safety regulations. The above photo taken by Princeton Hydro shows the grate being prepared for the installation of the sluice gate valve operating mechanism.

Photo taken on December 5, 2019 by Princeton Hydro showing the soil erosion mat being installed.

In December 2019, the team completed a topsoil application, seeding, and soil erosion matting installation to all disturbed areas of the site. All areas disturbed by construction activities (approximately 6,400 square feet) were graded to pre-construction conditions. The topsoil was applied to these areas and hand-raked to re-establish the original grades. The area was then seeded with perennial ryegrass, fertilized, and covered with a soil erosion mat. The above photo, taken on December 5, 2019, shows the soil mat being installed.

Following the final site inspection performed by Princeton Hydro in April 2020, we completed the Ballinger Lake Dam Spillway & Sluice Gate Improvements Closeout Report and presented it to MLC. The report confirmed that the site was considered stabilized in accordance with the approved project plans, the Standards for Soil Erosion and Sediment Control in New Jersey, and all NJDEP Bureau of Dam Safety requirements.

Princeton Hydro has designed, permitted, and overseen the reconstruction, repair, and removal of dozens of small and large dams in the Northeast. Click below to read about an emergency repair we completed on the Lake Wauwauskashe Dam. A concerning blockage developed in Lake Wauwauskashe Dam’s spillway and water was backing up at the upstream outlet structure causing a number of issues and potential hazards. Medford Lakes Colony, Princeton Hydro, and other project partners employed innovative solutions that lead to a successful emergency repair.

Creative, Timely Solutions Lead to Successful Dam Repair in Medford Lakes

To learn more about our dam and barrier engineering services, visit bit.ly/DamBarrier.

 

Dredging Children’s Pond to Restore Water Quality in Strawbridge Lake

Sedimentation in Children’s Pond, which is located in Strawbridge Lake park, was negatively impacting the water quality Strawbridge Lake. In order to restore the pond and reduce impacts to Strawbridge Lake, the Moorestown Township Council awarded contracts to Princeton Hydro for the dredging and cleanup of the Children's Pond.

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.

Image by NJ.govThe 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.

Before the dredging commenced, Princeton Hydro conducted a bathymetric survey to understand the depth and underwater features of a water body.

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:

A Day in the Life of a Construction Oversight Engineer

Understanding The Updated NJ Stormwater Rule

In March 2020, NJ Department of Environmental Protection (NJDEP) published the long-awaited revisions to the New Jersey Stormwater Management Rule (N.J.A.C. 7:8), which now requires the use of green infrastructure. But what do these updates actually mean for New Jersey’s stormwater infrastructure?

At Princeton Hydro, we recognize the benefit of green infrastructure and we’ve been incorporating it into our engineering designs since before the term was regularly used in the stormwater lexicon. We’ve been following the rule amendments very closely, so we’ve got the inside scoop on how to interpret these new updates. In this blog, we’ll break down the complexities and changes to help you understand what’s really going on.

What is Green Infrastructure?

So, let’s start with what green infrastructure actually is in a general sense. Many people think of green infrastructure solely as a way to classify certain stormwater best management practices, or BMPs, but in reality, it goes much deeper than that. Green infrastructure is an approach to engineering design that emphasizes the use of natural processes. Examples include green roofs, rain gardens, constructed wetlands, vegetated bioswales, and living shorelines. In general, approaching environmental management from this lens can help reduce costs and negative impacts to our ecosystems. The benefit to using green infrastructure over structural grey infrastructure is that these living BMPs are incredibly resilient. Being living systems, green infrastructure BMPs help decrease stormwater volume, as soil and vegetation naturally retain and evapotranspire water. Afterall, those natural processes have successfully worked for billions of years, so why not mimic them in our design?

In addition to effectively managing stormwater, green infrastructure has other added benefits such as reducing the heat island effect, reducing energy use, removing pollutants from the air, beautifying public spaces, and even increasing property value. Though the actual practice of green infrastructure may seem new and innovative, the concept has been around for decades.

What’s Changed?

So now, let’s get to the updated regulations. The biggest takeaway from this update is that green infrastructure is now required to meet the three performance criteria that NJDEP sets forth for stormwater management. The amendments to the rule give definitions of green infrastructure as it applies to stormwater management. The rule defines green infrastructure as follows:

“‘Green Infrastructure’ means a stormwater management measure that manages stormwater close to its source by:

  1. Treating stormwater runoff through infiltration into subsoil;

  2. Treating stormwater runoff through filtration by vegetation or soil; or

  3. Storing stormwater runoff for reuse.”

NJDEP evaluates stormwater management compliance through three basic performance metrics: (1) groundwater recharge, (2) water quality, and (3) peak flow control. While these metrics have remained relatively unchanged under the amended rule, the requirements for meeting them have been modified to include green infrastructure. The pre-existing rule required that major developments incorporate nonstructural stormwater management BMPs/strategies to the “maximum extent practicable” to meet their criteria. The amended rule not only gives specific suggestions for the kind of BMPs it’s looking for by adding a definition of green infrastructure, but it also makes those BMPs/strategies a requirement for compliance with the rule’s minimum standards.

The rule also includes tables outlining/summarizing the application of each type of stormwater BMP. One of the biggest changes here is that some of those BMPs have drainage area limitations, which could pose new challenges in the design process.

As stated above, the rule defines green infrastructure as, “a stormwater management measure that manages stormwater close to its source.” This is where those drainage area limitations come into play. Dry wells have a one acre drainage area limitation, which is not new, however, pervious pavement has a 3:1 ratio requirement, meaning that the water flowing over standard pavement, or impervious surfaces, should not be more than three times greater than the area of the pervious pavement.

Likewise, in the amended rule, BMPs like bioretention systems, have a drainage area limitation of 2.5 acres. The addition of this requirement will require designers to spread BMPs out throughout their site, instead of simply including one large structural BMP in a single location on the site. This approach decentralizes and distributes BMPs, enabling more stormwater to infiltrate into the ground, rather than runoff. Because this method more clostely mimics the natural water cycle, it is expected to foster better long-term performance of the BMPs.

This 2.5-acre drainage area limitation is going to effect stormwater design in that it will lead to BMP decentralization. So, project sites will likely have numerous smaller BMPs that will be distributed throughout the area, as opposed to having one large basin at the bottom of the site. This applies, in particular, to large scale commercial and residential projects, as the updated rule will discourage, and in most cases actually not allow, for the implementation of one large basin at the bottom of the site, which currently is common practice in large-scale development design.

Motor Vehicle Surfaces

Another update to the rule is that motor vehicle surfaces are now incorporated into the definition of major development, which was further clarified and defined as:

Any individual ‘development,’ as well as multiple developments that individually or collectively result in:

  1. The disturbance of one or more acres of land since February 2, 2004;

  2. The creation of one-quarter acre or more of “regulated impervious surface” since February 2, 2004;

  3. The creation of one-quarter acre or more of “regulated motor vehicle surface” since March 2,2021; or

  4. A combination of 2 and 3 above that totals an area of one-quarter acre or more. The same surface shall not be counted twice when determining if the combination area equals one quarter acre or more.

The amended rule requires these motor vehicle surfaces to have 80% total suspended solids (TSS) removal, in order to maintain water quality. These surfaces include standard pavement drive/parking areas and gravel and dirt drive/parking areas, according to the rule. However, the rule does not require water quality control for runoff from other impervious surfaces that are not traveled by automobiles, such as rooftops and sidewalks, or other paved walkway areas.

Revisions to BMP Manual

In addition to the changes made to the actual rule, NJDEP released an updated draft of Chapters 5, 12, 13, and Appendix D of the NJ Stormwater BMP Manual, which is currently open for public comment. Chapter 5 regards Stormwater Management and Quantity and Quality Standards and Computations and Chapter 12 regards Soil Testing Criteria. The biggest update to the manual is the addition of the recently finalized Chapter 13: Groundwater Table Hydraulic Impact Assessments for Infiltration BMPs, which requires design engineers to assess the hydraulic impact on the groundwater table to avoid adverse impacts such as surficial ponding, flooding of basements, interference with sewage disposal systems, and interference with the proper functioning of the BMP itself. The addition of this chapter will ensure that these issues are minimized, helping to improve the state’s stormwater management practices overall.

What does this all mean for New Jersey Municipalities?

New Jersey municipalities will need to comply with the new standards, as the NJ Stormwater Management Rule represents the minimum requirements for stormwater control ordinances. The law states that municipalities must update their ordinances by March 2, 2021. To make this transition a bit smoother, NJDEP has released a revised model ordinance in Appendix D of the NJ Stormwater BMP Manual to act as a sample for municipalities to follow when adopting these new regulations. Similar to before, municipalities do have the ability to require stricter stormwater performance metrics, but the criteria outlined in the rule are the minimum that must be met under the new regulations.

For more information on the updates to the stormwater regulations, you can check out an informational webinar (below) hosted by NJ-AWRA and The Watershed Institute. This webinar includes three presentations by New Jersey stormwater experts, including our Director of Stormwater Management & Green Infrastructure, Dr. Clay Emerson, PE, CFM.