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.

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

Client Spotlight: Lake Hopatcong Foundation

This month we are launching the first blog in our Client Spotlight Blog Series! Each spotlight will feature one of our important client relationships in order to give you an inside look at our collaboration. We pride ourselves on forming strong ties with organizations that share our values of creating a better future for people and our planet. So we are excited to be able to share snippets of the incredible teamwork we’ve been able to accomplish over the years!

At Princeton Hydro, we value our client relationships, as the collaborative work we are able to complete with organizations like the Lake Hopatcong Foundation (LHF) reaches exponentially further than anything we could complete alone. One of the reasons our organizations have such strong symmetry is that our values align and complement each other.

As their mission states,”Lake Hopatcong Foundation dedicates itself to protecting the lake environment and enhancing the lake experience, bringing together public and private resources to encourage a culture of sustainability and stewardship on and around New Jersey’s largest lake, for this and future generations.” We are so proud to help protect New Jersey’s largest lake with LHF.

We have been working with LHF since its inception in 2012, which is why we are excited to feature them in our first client spotlight blog. We spoke with Jessica Murphy, President/Executive Director of the Foundation, and Donna Macalle-Holly, Grants and Program Director, to give you an insider look at the organization:

Q: What makes the Lake Hopatcong Foundation unique?

A: The Lake Hopatcong Foundation is unique in that our mission spans a wide spectrum of activities. In addition to projects that focus on the lake environment, we also take on initiatives that support education, safety, community-building, recreation, and even arts and culture. The lake is split between two counties and four towns, so bringing the community together for all these things is very important to us, in addition to making sure the lake itself is healthy.

Q: What does the Lake Hopatcong Foundation value?

A: During our strategic planning process, the board and staff developed a list of values that we go back to when operating and making decisions. They are:

  • Collaboration – We operate in a way that brings people together throughout the community.
  • Action – We are committed to our mission, moving quickly to take on projects that have an impact on and around the lake.
  • Sustainability – We are forward-thinking when making decisions, taking future generations into account when considering projects and initiatives.
  • Warmth – We are a friendly face to the community, showing the best of ourselves and bringing out the best in the people of Lake Hopatcong.

Q: How long have you been working with Princeton Hydro?

The Lake Hopatcong Floating Classroom ready for take off!

When we first started the Lake Hopatcong Foundation in 2012, Dr. Fred Lubnow was kind enough to do a water quality presentation as one of our very first events as an organization! In the years since, we’ve worked closely with Princeton Hydro, particularly in a support role as they conduct business with the Lake Hopatcong Commission. The Lake Hopatcong Commission is a state entity created in 2001 through the Lake Hopatcong Protection Act dedicated to protecting the water quality of Lake Hopatcong and to preserve the natural, scenic, historical and recreational resources of the lake. LHF funded Princeton Hydro’s water quality monitoring during the years that the Commission ran out of money

Q: What types of services has Princeton Hydro provided to your organization?

A: In addition to water quality monitoring on the lake, Princeton Hydro has led volunteer training for us in our efforts to prevent the spread of invasive species and to teach local students in our spring field trip program. Dr. Lubnow has also worked alongside us in applying for grants and in providing insight and expertise for other environmental projects at the lake, including helping guide the installation of floating wetland islands, and helping our NJ Lakes Group to work with NJDEP on Harmful Algal Bloom (HAB) policies. He even did a quick fact check on our children’s book, Lake Hopatcong Speaks Out, before we published it!

Q: Do you have a favorite or most memorable project we’ve worked on together?

Princeton Hydro’s Senior Project Manager, Christopher Mikolajczyk, CLM, presenting during a Water Scout training held by the Lake Hopatcong Foundation.

A: The days that Chris Mikolajczyk spent teaching our volunteers about how to find and remove water chestnuts from the lake were a lot of fun, particularly because we were kayaking on the lake for it! And, also because the kayak we provided Chris was too small for him, and he had to scrunch in to fit, but he was a trouper and paddled on.

Q: What are some exciting things your organization is working on right now?

A: We are working closely with Princeton Hydro and LHC on a series of projects, funded through NJDEP grants, LHC, LHF, and local governments, that we hope will prevent and mitigate HABs on the lake. Those projects include aeration systems, phosphorus-locking technologies, and stormwater infrastructure upgrades. We’re excited to see how effective each can be. Also, on August 7 at 12:30, Dr. Lubnow will be presenting the Lake Hopatcong water quality monitoring project results at LHF’s “Thirst for Knowledge” lunch-and-learn webinar series, which was created to share information and discuss topics of interest to our lake community. To register for the free webinar, visit lakehopatcongfoundation.org.

Photo by: Colleen Lyons of the Lake Hopatcong Commission

Photo by: Colleen Lyons of the Lake Hopatcong Commission

Q: What drives you to want to go to work every day?

A: All of us at Lake Hopatcong Foundation have a passion for this lake and want to see it protected; we have a love for the community that surrounds it, too. Jessica Murphy grew up on the lake, met her husband here, and now is raising her four children to love the lake, too. Donna Macalle-Holly also met her husband on Lake Hopatcong, lives on the lake, and has worked professionally to take care of it for nearly two decades. Everyone in our office has made memories on Lake Hopatcong and developed friendships with those who live and work here. Those personal connections fuel our passion for what we do.

Q: How can Princeton Hydro support you/your organization in the future?

A: Continue to be the incredible resource you are! We are so fortunate to have the deep knowledge and expertise that Fred and your entire team provide, and we look forward to continuing to work together in the years ahead.

Water Scouts paddling on Lake Hopatcong.


Some recent projects we are/have been working on with LHF include installing biochar bags to help control phosphorus levels and applying Phoslock to help mitigate harmful algal blooms! Because of our history working on Lake Hopatcong, we too have gained a passion for protecting and maintaining this lake. This incredibly important work could not be done without the genuine devotion and dedication from the Lake Hopatcong Foundation. We look forward to continuing great work with this incredible group!

Floating Wetland Islands: A Sustainable Solution for Lake Management

Nick Decker, PA State Parks Resource Manager, and Cory Speroff and Katie Walston of Princeton Hydro position a floating island of native plants in the lake at Frances Slocum State Park

Looking for a unique and creative way to manage nutrient runoff in freshwater lakes? Installing Floating Wetland Islands (FWI) is a low-cost, effective green infrastructure solution used to mitigate phosporus and nitrogen stormwater pollution often emanating from highly developed communities and/or argricultural lands.

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 algae growth; 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.

“A pound of phosphorus can produce 1,100 lbs of algae each year. And, each 250-square foot island can remove 10 lbs of phosphorus annually.” explains Princeton Hydro Staff Scientist Katie Walston. “So, that’s 11,000 lbs of algae that is mitigated each year from each 250 square foot of FWI installed!”

This illustration, created by Staff Scientist Ivy Babson, conveys the functionality of a Floating Wetland Island

This illustration, created by Staff Scientist Ivy Babson, conveys the functionality of a Floating Wetland Island

Typically, FWIs consist of a constructed floating mat with vegetation planted directly into the material. Once the islands are anchored in the lake, the plants thrive and grow, extending their root systems through the mat and absorbing and removing excess nutrients from the water column such as phosphorus and nitrogen.

Native plants on the floating island designed by Princeton Hydro that will help reduce the phosphers and algae in the lake at Frances Slocum State ParkThe plants uptake a lot of nutrients, but the workhorse of the FWIs is the microbial community. The matrix used within the islands has a very high surface area and it promotes microbial growth, which performs the majority of the nutrient uptake. Additionally, the root growth from the plants continues to increase the surface area for the microbial biofilm to grow on. Both the plants and microbes acting together help optimize nutrient removal.

Princeton Hydro has designed and installed numerous FWIs in waterbodies large and small for the purpose of harmful algal bloom control, fisheries enhancement, stormwater management, shoreline preservation, wastewater treatment, and more. FWIs are also highly adaptable and can be sized, configured, and planted to fit the needs of nearly any lake, pond, or reservoir.

Greenwood Lake

Recently, the Princeton Hydro team completed a FWI installation in Belcher’s Creek, the main tributary of Greenwood Lake. The lake, a 1,920-acre waterbody located in  both Passaic County, New Jersey and Orange County, New York, is a highly valued ecological and recreational resource for both states and has a substantial impact on the local economies. In addition, the lake serves as a headwater supply of potable water that flows to the Monksville Reservoir and eventually into the Wanaque Reservoir, where it supplies over 3 million people and thousands of businesses with drinking water. 

Since the lake was negatively impacted by HABs during the 2019 summer season, Greenwood Lake Commission (GWLC) has made a stronger effort to eliminate HABs and any factors that contribute to cyanobacteria blooms for 2020 and into the future. Factors being addressed include pollutant loading in the watershed, especially that of Belcher’s Creek. The installation of FWIs in Belcher’s Creek will immediately address nutrients in the water before it enters Greenwood Lake and help decrease total phosphorus loading. In turn this will help reduce HABs, improve water quality throughout the Greenwood Lake watershed, and create important habitat for beneficial aquatic, insect, bird and wildlife species.

“In addition to the direct environmental benefits of FWIs, the planting events themselves, which involve individuals from the local lake communities, have long-lasting positive impacts,” said Dr. Jack Szczepanski, Princeton Hydro Senior Project Manager, Aquatics Resources. “When community members come together to help plant FWIs, it gives them a deepened sense of ownership and strengthens their connection to the lake. This, in turn, encourages continued stewardship of the watershed and creates a broader awareness of how human behaviors impact the lake and its water quality. And, real water quality improvements begin at the watershed level with how people treat their land.”

The project was partially funded by the New Jersey Department of Environmental Protection’s (NJDEP) Water Quality Restoration Grants for Nonpoint Source Pollution Program under Section 319(h) of the federal Clean Water Act. As part of the statewide HAB response strategy, the NJDEP made $13.5 million in funding available for local projects that improve water quality and help prevent, mitigate and manage HABs in the state’s lakes and ponds. The GWLC was awarded one of the NJDEPs matching grants, which provided $2 in funding for every $1 invested by the grant applicant. For this project, the GWLC purchased the FWIs and NJDEP provided the 2:1 cash match in order for the GWLC to implement additional HAB prevention and mitigation strategies in critical locations throughout the watershed.

Check out the photos from last month’s installation:

Here are a few more examples of FWI design and installation projects we’ve completed:

Frances Slocum Lake

Officials with the state Department of Conservation and Natural Resources, Luzerne Conservation District, Nanticoke Conservation Club, and students at Rock Solid Academy in Shavertown teamed up with Princeton Hydro to install two floating islands on the lake. They were planted natives to the area, including Green Bulrush, Broadleaf Arrowhead, Blue Flag Iris, Shallow Sedge, and Spotted Joe-Pye.

Princeton Hydro also installed solar-powered aeration systems in the middle of the FWIs. Aeration systems provide additional water quality improvements, help prevent water around the islands from stratifying, promotes “through-column” mixing, and helps to minimize the occurrence of phytoplankton blooms. The use of solar-powered aeration, whether installed on a FWI or along the shoreline, creates a sustainable, cost-effective, zero-energy water treatment solution, and eliminates the need to run direct-wired electrical lines to remote locations. Learn more.

Princeton Hydro also installs solar-powered aeration systems on FWIs, creating a sustainable, cost-effective, holistic water treatment solution.
Harveys Lake

Princeton Hydro, along with project partners, installed five floating wetland islands in Harveys Lake in order to assimilate and reduce nutrients already in the lake. The islands were placed in areas with high concentrations of nutrients, placed 50 feet from the shoreline and tethered in place with steel cables and anchored. A 250-square-foot FWI is estimated to remove up to 10 pounds of nutrients per year, which is significant when it comes to algae. Learn more.

Volunteers install native plants in one of the FWIs installed in Harveys Lake. Photo by: Mark Moran, The Citizen’s Voice.
lake hopatcong

Through a nonpoint source pollution grant awarded by NJDEP to the Lake Hopatcong Commission, Jefferson Township was able to install FWIs in order to deliver better water quality to Ashley Cove and Lake Hopatcong. The primary goal of the project was to reduce high levels of algae-causing phosphorus present in the lake. In each FWI, indigenous plants, Milkweed and Hibiscus, among other vegetation, were planted along with peat and mulch. Learn more.

Casey Hurt, right, and Richard Ampomah maneuver one of two floating wetland islands in Ashley Cove.
Lake Holiday

Two interconnected sets of FWIs were installed in Lake Holiday in the tributary coves of Isaac’s and Yeider’s Creeks. The strategic placement of the islands eliminates interference with normal boat traffic. In order to minimize movement, the FWIs were secured to trees along the bank with coated cable and protective bands and anchored to the lake bottom with submerged concrete blocks. Learn more.

Senior Scientist Katie Walston installs goose netting around the vegetation in order to prevent geese and other unwanted species from feeding on the plants.

Over the coming weeks, our team will be in Asbury Park, New Jersey installing FWIs in Sunset Lake. Stay tuned for more! For additional information about floating wetland islands and water quality management, go here: bit.ly/pondlake.

6 Ways to Celebrate Lakes Appreciation Month

July is Lakes Appreciation Month – a great time of year to enjoy your community lakes and help protect them.

Lakes Appreciation Month was started by North American Lake Management Society (NALMS) to help bring attention to the countless benefits that lakes provide, to raise awareness of the many challenges facing our waterways, and to encourage people to get involved in protecting these precious resources.

“You work and play on them. You drink from them. But do you really appreciate them? Growing population, development, and invasive species stress your local lakes, ponds, and reservoirs. All life needs water; let’s not take it for granted!” – NALMS

Chemical pollutants, stormwater runoff, hydrocarbons, invasive aquatic species, and climate change are just a few of the the serious threats facing lakes and other freshwater habitats. So what can you do to to help?


We’ve put together six tips to help you celebrate Lakes Appreciation Month and get involved in protecting your favorite lakes:

1. Join the “Secchi Dip-In” contest

The “Secchi Dip-In” is an annual citizen science event where lake-goers and associations across North America use a simple Secchi disk to monitor the transparency or turbidity of their local waterway. Created and managed by NALMS, volunteers have been submitting information during the annual Dip-In since 1994. Get all the Dip-In details here.

2. Monitor and report algae blooms

With the BloomWatch App, you can help the U.S. Environmental Protection Agency understand where and when potential harmful algae blooms (HABs) occur. HABs have the potential to produce toxins that can have serious negative impacts on the health of humans, pets, and our ecosystems. Click here to learn more and download the app here. For more information on HABs, check out our recent blog.

3. Commit to keeping your lake clean

Commit to keeping your lake clean: Volunteers play a major role in maintaining the health and safety of community waterways. If you’re interested in helping to conserve and protect your water resources, you can start by cleaning up trash. Choose a waterbody in your community; determine a regular clean-up schedule; and stick to it! Cleaning your neighborhood storm drains really helps too; click here to find out how.

Photo: Santiago Mejia, The Chronicle
4. support your local lake

You can help support your favorite lake by joining or donating to a lake or watershed association. As an organized, collective group, lake associations work toward identifying and implementing strategies to protect water quality and ecological integrity. Lake associations monitor the condition of the lake, develop lake management plans, provide education about how to protect the lake, work with the government entities to improve fish habitat, and much more.

5. Get outside and enjoy (safely)

There are countless ways to enjoy and appreciate your community lakes. During Lakes Appreciation month, take photos that illustrate how you appreciate your community lakes, share them on social media using the hashtag: #LakesAppreciation, and hopefully you’ll inspire others to show their Lake Appreciation too.

6. ENTER the Lakes Appreciation Challenge

NALMS invites you to participate in its social media photo contest, titled “Show Your Lakes Appreciation Challenge.” To participate: Take a picture of yourself or someone you know enjoying or working on a lake or reservoir during July. And, upload the photo to Facebook, Instagram and/or Twitter using a descriptive caption and the #LakesAppreciation hashtag. Three winners will be determined via a raffle and announced via social media on Monday, August 3rd. Learn more.

fishing on lake

To ensure you’re staying safe while participating in Lakes Appreciation Month and all outdoor activities, please be sure to follow local regulations and the CDC’s recommended COVID-19 guidelines.

To learn more about NALMS and get more ideas on how to celebrate your local lakes, go here: https://www.nalms.org. If you’re interested in learning more about Princeton Hydro’s broad range of award-winning lake management services, go here: http://bit.ly/pondlake.

 

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.

Mitigating Harmful Algal Blooms at Lake Hopatcong: Largest Application of Phoslock in Northeast

To prevent harmful algal blooms (HABs) in New Jersey’s largest lake, a clay-based nutrient inactivating technology called Phoslock, is being applied in Lake Hopatcong this week. This is the largest Phoslock treatment to occur in the Northeastern U.S. The Phoslock treatment, which is happening in the southern end of the lake called Landing Channel, is expected to take approximately one week depending on the weather conditions.

Over the course of the 2019 summer season, Lake Hopatcong suffered from large-scale and persistent HABs causing local and county health agencies to close off all beaches and issue advisories over large sections of the lake. These unprecedented conditions had significant negative impacts on the ecological, recreational, and economic resources of the lake and region. In order to combat HABs in this upcoming 2020 summer season, the Lake Hopatcong Commission has partnered with the Lake Hopatcong Foundation, four municipalities (Jefferson, Hopatcong, Mt. Arlington, and Roxbury), two counties (Morris and Sussex), and their environmental consultant, Princeton Hydro, to develop both short- and long-term lake management strategies.

“The negative effects of HABs in our lake last year were numerous, widespread, and in some cases devastating,” recalled Donna Macalle-Holly of Lake Hopatcong Foundation. “It is imperative for every stakeholder to pool our resources to keep it from happening again. Collaboration is the only way to protect public health, as well as the health of New Jersey’s largest lake.”

In an effort to evaluate a variety of innovative in-lake and watershed-based measures to prevent, mitigate, and/or control harmful algal blooms in Lake Hopatcong, the Lake Hopatcong Commission was awarded a $500k grant as part of New Jersey Department of Environmental Protection’s (NJDEP) new $13.5M initiative to reduce and prevent future harmful algal blooms in New Jersey. In addition to the $500k grant, the aforementioned local government and nonprofit stakeholders provided $330k in matching funds to implement and evaluate a variety of ways to address HABs in Lake Hopatcong.

“Our lake community cannot sustain another year like 2019,” said Lake Hopatcong Commission Chairman Ron Smith. “Since the news of our grant award in early March, we have been working with our partners to make sure the projects are implemented in time for the 2020 season.”

This week, the water resource engineering and natural resource management firm, Princeton Hydro—a lake management consultant to Lake Hopatcong for over two decades—is implementing the first and largest innovative measure as part of the NJDEP HABs grant-funded project. This involves treating 50 acres of the southern end of the lake with Phoslock, a clay-based product that inactivates phosphorus in both the water column and the sediments, making this critical nutrient unavailable for algal growth. The Phoslock treatment, which requires proper permitting by NJDEP, is applied as a slurry and will be distributed from a boat. The slurry will temporarily make the water appear turbid, but should disperse approximately two to six hours after each treatment.

“We are expecting the Phoslock treatment to limit the growth of algae and therefore reduce the occurrence of harmful algal blooms in the lake this summer, keeping it open for recreation and business,” said Dr. Fred Lubnow, Director of Aquatic Resources at Princeton Hydro and leading HABs expert. “If this technology is deemed successful and cost-effective in Lake Hopatcong, we could set the precedent for large-scale HABs prevention in other lakes throughout New Jersey, and even across the nation.”

Developed by the Australian national science agency CSIRO, Phoslock is frequently used to strip the water column of dissolved phosphorus, as well as to inactivate phosphorus generated from deep, anoxic sediments. Recently, at a smaller scale, it has been shown to inactivate the mobilization of phosphorus from shallow sediments where there is a mobilization of phosphorus from both chemical and biological processes.

Algae uses phosphate, the biologically available form of phosphorus, as a food source to grow. When there is an excessive amount of phosphorus in a lake, algal growth can be dense and can negatively affect water quality. This excessive plant growth, caused by eutrophication, can both cause a lack of oxygen available, leading to fish kills, as well as produce harmful algal blooms with cyanotoxins, which are harmful to humans and pets.

Photo credit: SePRO Corporation

After Phoslock is applied, it sinks through the water column, binding phosphate as it moves towards the sediment. Once settled at the bottom of the lake, it forms a very thin layer and continues to bind phosphate released from the sediment, thus controlling the release of phosphorus into the lake. One pound of phosphorus has the potential to generate up to 1,100 lbs of wet algae biomass. However, 1.1 tons of Phoslock is capable of removing 24 pounds of phosphorus — that’s over 26,000 lbs of wet algae biomass not growing in the lake for every 1.1 ton of Phoslock applied. In turn, Phoslock’s ability to suspend biologically available phosphorus is therefore a major step towards improving a lake’s water quality.

As part of the NJDEP HABs grant funding, the stakeholder group will be evaluating the relative effectiveness of this treatment strategy. Because of its shallow depth and separation from the main lake, the Landing Channel area was a good candidate for evaluation of this technology. Princeton Hydro will conduct pre- and post-treatment monitoring of the Phoslock treatment area in order to conduct an objective evaluation of the cost effectiveness of the treatment as a means of preventing the development and/or mitigation of HABs. If the study indicates that Phoslock is a cost-effective treatment, the Lake Hopatcong Commission may consider additional trials in other sections of the lake, if funding is available.

To learn more about HABs, check out our recent blog:

Identifying, Understanding and Addressing Harmful Algae Blooms

Analyzing Mitigation Strategies for Flood-Prone Philadelphia Community

Photo from Eastwick Friends and Neighbors Coalition

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.

Putting Hydrologic & Hydraulic Analysis to Work in Philadelphia

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 Senior Ecologist Christiana Pollack CFM, GISP participated in a workshop for Eastwick residents held by CCRUN and the Lower Darby Creek team. The goal of the workshop was to get the community’s input on the accuracy of the predictive models.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.

This is an example of a 2D model showing where the water is originating, how the water flows through the neighborhood, moves to the lower elevations, and eventually sits.

This is an example of a 2D model showing where the water is originating, how the water flows through the neighborhood, moves to the lower elevations, and eventually sits.

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.

This model was developed to illustrate how the removal of the landfill impacts waterflow through the Eastwick community.

This model was developed to illustrate how the removal of the landfill impacts waterflow through 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.

Take a Deeper Look at Eastwick Flood Mitigation Efforts

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.

You can watch the full seminar here:

For more information about Princeton Hydro’s flood management services, go here: http://bit.ly/PHfloodplain.

NJDEP Releases Updated Guidance for Harmful Algal Blooms

Last summer, 39 of New Jersey’s lakes were plagued with toxic algae outbreaks, also known as harmful algae blooms or HABs, causing major water quality degradation, beach closures and health advisories. In response, the NJDEP implemented a unified statewide approach to addressing HABs in freshwater recreational waters and sources of drinking water, and protecting the public from risks associated with exposure to cyanobacteria.

Last week, NJDEP announced a new component to its statewide Cyanobacterial HAB Response Strategy: a color-coded health alert index that provides precise recreational use recommendations for impacted waterbodies based on levels of cyanobacteria and/or cyanotoxins present. The index has six tiers – NONE, WATCH, ALERT, ADVISORY, WARNING, and DANGER – each providing recommendations on the specific activities that should or should not be pursued based on water monitoring results.

“Princeton Hydro is proud to be one of the contributing factors in the development of the Updated Guidance for HABs,” said said Dr. Fred Lubnow, Director of Aquatic Resources for Princeton Hydro. “We feel this updated protocol will provide the necessary and objective information for State and local organizations to make informed and rational decisions, based on sound and scientifically-based data, on how to deal with HABs in a recreational setting.

Princeton Hydro and Clean Water Consulting are the technical advisers for the New Jersey Lake Group, who have met a number of times over the last 8 to 9 months to discuss the State’s guidance on dealing with HABs.  In late 2019, on behalf of the New Jersey Lake Group, Princeton Hydro and Clean Water Consulting developed a White Paper providing recommended changes for consideration to NJDEP’s Recreational Response Strategy to HABs.

“I’m proud to say that many of the provided recommendations were integrated into NJDEP’s Updated Guidance for HABs,” explained Dr. Lubnow.

WATCH
(Suspected or confirmed HAB with potential for allergenic and irritative health effects)
This warning will be posted when HAB cell counts exceed 20,000. In this scenario, public beaches remain open, but the index instructs the public to use caution, provides information on the potential less serious health effects, and allows for more informed decision-making.

ALERT
(Confirmed HAB that requires greater observation due to increasing potential for toxin production)
This warning indicates a public bathing beach closure only and is posted when a HAB has been confirmed with cell counts between 40,000 and 80,000 and no known toxins above the public threshold. Beaches remain open (dependent upon local health authority) and monitoring for future toxin production should be increased.

ADVISORY
(Confirmed HAB with moderate risk of adverse health effects and increased potential for toxins above public health thresholds)
Signs will be posted for this warning level when cell counts exceed 80,000 or when toxin levels exceed 3 micrograms per milliliter of microcystins. Public bathing beaches will be closed, but the waterbody will remain accessible to some “secondary contact” activities, like boating.

WARNING and DANGER
(Confirmed HAB with high risk of adverse health effects due to high toxin levels)
and (Confirmed HAB with very high risk of adverse health effects due to high toxin levels)
These tiers are designed to alert the public to the presence of HABs that are producing very high levels of toxins which justify additional caution. In some instances, the entire waterbody may be closed for all public use. New Jersey has experienced approximately 12 “warning level” HAB events over the last 3 years; monitoring has never indicated a “danger level” HAB event.

According to their press release, NJDEP is committed to working with local officials to implement the index and get signage posted at lakes throughout the state as soon as possible.

In order to create the health index, NJDEP scientists carefully reviewed HABs data collected over the last three years by Lake Hopatcong Commission, Lake Hopatcong Foundation, Princeton Hydro, and other sources. The tiered warning system will enable lake communities, residents and visitors to make more individualized decisions about what risks they are willing to take and what activities they feel comfortable engaging in at the various levels of HABs.

In the coming days, the NJDEP’s Harmful Algal Bloom website will be updated to include the new health index and accompanying signage, relevant monitoring data, and other information for each of the impacted bodies of water, as well as an updated HAB Monitoring and Response Strategy. For now, you can read the full press release and additional information here: https://www.nj.gov/dep/newsrel/2020/20_0023.htm.

To learn more about HABs, check out our recent blog:

Identifying, Understanding and Addressing Harmful Algae Blooms