Don’t Get Sunk: Everything You Need to Know About Sinkholes (Part One)

Photo by Steven Reilly/New Jersey Herald

Sinkholes are a phenomenon that tend to baffle and frighten most people. How is it possible that the ground beneath our feet could just drop? How do we know if we’re nearby a sinkhole? What should we do if we see one? How are sinkholes fixed? The mystery of the unknown around sinkholes can be quite unnerving.

Have no fear, we’ve got answers to all of those questions and more! In this two-part blog series, our experts share their knowledge and provide important information about this scary occurrence. In part one, we provide a detailed look at what a sinkhole is, three different types of sinkholes, and what causes them to form. In part two, we explore how to detect sinkholes and the steps taken to repair them.

What is a Sinkhole?

Sinkholes are a common phenomenon around the world. They result from both man-made and natural causes. Marshall Thomas, a Princeton Hydro geologist, describes sinkholes as “depressions observed from the surface, caused by dissolution of carbonate rocks.” In other words, sinkholes form when the rock below the land surface gets dissolved by water that penetrates the surface and continues to move downward, further into the subsurface.

Most common in areas with “karst terrain,” or types of rocks that can easily be dissolved by groundwater, sinkholes can go undetected for years until the space underneath the surface gets too big or enough of the surface soil is washed away. Sometimes the holes are small, measuring a few feet wide and ten feet deep. Sometimes the holes are hundreds of miles wide and deep. However, all of them can be dangerous.

Sinkholes are found throughout the world. States like Pennsylvania, Texas, Florida, Alabama, Tennessee, and Missouri are at higher risk for sinkholes because they tend to have more soluble rocks like salt beds and domes, gypsum, limestone, and other carbonate rocks. People living in these states are recommended to have professionals look at any property they intend to buy to make sure it isn’t in an area above soluble rock.

Types of Sinkholes

Not all sinkholes are the scary, earth-falling-out-from-underneath-your-feet events. Some occur slowly over time and are very evident from the surface. Geologists classify sinkholes in three major types. Their formation is determined by the same geological processes, barring a few differences. Let’s dive in!

1. Dissolution Sinkholes

Illustration by USGSDissolution sinkholes start to form when limestone or dolomite is very close to the soil surface, usually covered by a thin layer of soil and permeable sand which washes away or is eroded. Rain and stormwater runoff gradually percolate through crevices in the rock, dissolving it. Consequently, a bowl-shaped depression slowly forms.

Sometimes, dissolution sinkholes become ponds when the depression gets lined with debris, which traps water inside. Dissolution sinkholes develop gradually and are normally not dangerous. However, the ones that become ponds can drain abruptly if water breaks through the protective bottom layer.

Fun fact: Most of Florida’s lakes are actually just large sinkholes that filled up with water!

2. Cover-Subsidence Sinkholes

Illustration by USGSThis type of sinkhole, which starts with the dissolution of the underlying carbonate bedrock, occurs where the covering sediment is permeable (water can pass through it) and contains sand. First, small pieces of sediment split into smaller pieces and fall into openings in the carbonate rock underneath the surface. With time, in a process called piping, the small particles settle into the open spaces. This continues, eventually forming a dip in the surface ranging from one inch to several feet in depth and diameter. Again, these aren’t the sinkholes movies are made about.

3. Cover-Collapse Sinkholes

Illustration by USGSThis type of sinkhole is the one making headlines and causing fear. In order for cover-collapse sinkholes to happen, the covering soil has to be cohesive, contain a lot of clay and the bedrock has to be carbonate. Similar to the cover-subsidence sinkholes, the cohesive soil erodes into a cavity in the bedrock. The difference with this is that the clay-filled top surface appears to remain intact from above. However, underneath, a hollowed out, upside down bowl shape forms. That hollowing gets bigger and bigger over time until eventually, the cavity reaches the ground surface, causing the sudden and dramatic collapse of the ground. Just like that, poof, we have a sinkhole that appears to be surprising and abrupt but really has been brewing for many years.

What Causes a Sinkhole?

Sinkholes can be natural or man-made. The most common causes of a sinkhole are changes in groundwater levels or a sudden increase in surface water.

Intensive rain events can increase the likelihood of a sinkhole collapse. Alternatively, drought, which  causes groundwater levels to significantly decrease, can also lead to a greater risk of collapse of the ground above. In a world with a greater variability in rainfall and drought events due to climate change, sinkholes may become a more common occurrence around the world.

Humans are also responsible for the formation of sinkholes. Activities like drilling, mining, construction, broken water or drain pipes, improperly compacted soil after excavation work, or even significantly heavy traffic (heavy weight on soft soil) can result in small to large sinkholes. Water from broken pipes can penetrate through mud and rocks and erode the ground underneath and cause sinkholes.

Most commonly, human-caused sinkholes are the result of:

  • Land-use practices like groundwater pumping, construction, and development
  • Changing of natural water-drainage patterns
  • Development of new water-diversion systems
  • Major land surface changes, causing substantial weight changes

In some cases, human-induced sinkholes occur when an already forming sinkhole is encountered during construction processes such as excavation for stormwater basins and foundations. Dissolution of bedrock generally occurs in geologic time-frames (thousands of years). In these cases, the excavation process has removed the covering soils, decreasing the distance between the top of the void and the ground surface.  

In other cases, voids in the bedrock are generated due to rock removal processes such as hammering and blasting. Hammering and blasting can generate fractures or cracks in the bedrock that soil can then erode into. A void in the bedrock may already exist, however, the process of removing the bedrock by hammering and/or blasting can speed up the meeting of the upside-down bowl and the surface that much quicker. One site where this happened has experienced over 35 sinkholes in 4 years.

Overall, it’s generally not a good idea to pump groundwater or do major excavation in areas that are prone to sinkholes. According to the USGS, over the last 15 years sinkhole damages have cost on average at least $300 million per year. Because there is no national tracking of sinkhole damage costs, this estimate is probably much lower than the actual cost. Being more mindful about the subsurface around us and our actions could help lower the average yearly cost in damages and even save lives.

Photo by Barbara Miller PennLive Patriot News

Stay tuned for Part Two of this blog series in which we explore we explore how to detect sinkholes and the steps taken to repair them! For more information about Princeton Hydro’s Geotechnical Engineering services, go here: http://bit.ly/PHGeotech

Special thanks to Princeton Hydro Staff Engineer Stephen Duda, Geologist Marshall Thomas, and Communications Intern Rebecca Burrell for their assistance in developing this blog series.

Sources:

DIY: Protecting Water Quality in Your Community

There are lots of things we can do to preserve our precious water resources. Reducing stormwater pollution in our neighborhoods is something everyone can take part in. Storm drain cleaning is a great place to start!

DIY Storm Drain Cleaning

Urbanization has fundamentally altered the way that water moves through the landscape. Stormwater that doesn’t soak into the ground runs along streets and parking lots and picks up pollutants. Much of the pollution in our nation’s waterways comes from everyday materials like fertilizers, pesticides, motor oil, and household chemicals. Rainwater washes these substances from streets, yards and driveways into storm drains.

It’s a common misconception that storm drains lead to wastewater treatment plants. In actuality, storm drains rarely lead to treatment plants and instead stormwater systems carry untreated water directly to the nearest waterway. This polluted runoff can have negative impacts on water quality, overstimulate algal growth (both toxic and non-toxic), harm aquatic species and wildlife, and cause trash and debris to enter our lakes, streams, rivers and oceans.

https://www.middlesexcentre.on.ca/Public/Stormwater

We can all do our part to improve and preserve water resources in our community and beyond!

Keeping neighborhood storm drains cleaned is one simple step. Removing debris that collects in nearby stormwater catch basins, storm drains and along curbs promotes cleaner runoff, reduces the potential for flooding, and decreases the amount of pollution and trash entering our waterways.

Follow these simple steps for DIY storm drain cleaning:

  1. Photo: Santiago Mejia, The ChronicleRake/sweep and discard debris that has collected on top of the storm grate and in curbside rain gutters. Please note: If you notice a major blockage or issue with a storm drain, contact your local municipality immediately.
  2. Use a scrub brush or toilet bowl scrubber to remove debris that may be stuck to the storm grate.
  3. Adopt a storm drain(s) and maintain a regular cleaning schedule: Make a note on your calendar each quarter to clean and clear debris from storm drains nearby your home or workplace. And, make a habit of checking your storm drains after rainstorms when clogging is most common.
  4. Host a community clean-up day that includes trash pick-up, storm drain cleaning, and disseminating information on the impacts of stormwater runoff and what we can do to help.
  5. Consider contacting your local watershed association or municipality about getting drain markers installed on storm drains throughout the community. The markers act as a continued public reminder that anything dumped into a storm drain eventually ends up in our precious waterways downstream.

Remember: Small actions lead to big achievements in protecting water quality. 

REGISTER: Green Infrastructure Stormwater Management One-Day Course

REGISTRATION IS STILL OPEN FOR MONTCLAIR STATE UNIVERSITY’S GREEN INFRASTRUCTURE STORMWATER MANAGEMENT ONE-DAY CONTINUING EDUCATION COURSE BEING HELD ON SEPTEMBER 20, 2019 FROM 8 AM – 4 PM

Are you a consultant, planner, municipal representative, community leader, or project manager seeking to learn more about Green Stormwater Infrastructure & Management Techniques? This one-day course is for YOU!

Green infrastructure techniques have increasingly become the “go to” strategy to address flooding, water quality, and environmental impacts caused by stormwater runoff. Whether it be rain gardens or regional bioretention basins, infiltration basins or other large-scale bio engineered BMPs, green infrastructure is being implemented everywhere from suburban subdivisions to urban redevelopment sites. Unfortunately, while growing popular, these techniques are often misapplied, improperly constructed, or inadequately maintained.

This innovative one-day class focuses on the proper design and implementation of green infrastructure BMPs, as well as their special maintenance requirements. The course curriculum includes interactive presentations, case studies and project examples.

This year’s course will cover the following topics and more:

  • The Application and Advantages of Green Infrastructure Stormwater Management Techniques
  • Design and Construction of Infiltration Basins
  • Data Collection Needs: Soil, Geotechnical, and Groundwater Hydrology Data
    Design and Construction of Gravel Wetland Systems
  • Rain Garden Design and Application
  • Green Infrastructure Stormwater Options and Alternative Capping Techniques for Remediation Sites

Dr. Stephen Souza, Princeton Hydro Co-Founder and President of Clean Waters Consulting, LLC, is the faculty coordinator for the course, which also features a lecture by Princeton Hydro’s Green Infrastructure Practice Area Leader Dr. Clay Emerson, PE, CFM.

Course participants will also receive professional credits, including:

  • New Jersey LSRP CECs: 7 Technical CECs (NJ SRPLB Course # 2015-065);
  • New Jersey Professional Engineers: 7 CPCs;
  • New Jersey Board of Architects: 7 hours of CECs;
  • Certified Floodplain Managers: 6.5 CECs; and
  • NJ Public Health Continuing Education Contact Hours: 7 CEs.

Princeton Hydro is proud to partner with Montclair State University and take part in this valuable continuing professional education course. We hope to see you there!

Learn More & Register Today

Managing Urban Stormwater Runoff and Revitalizing Natural Habitat at Harveys Lake

Measuring 630+ acres, Harveys Lake, located in Luzerne County, Pennsylvania, just northeast of Wilkes-Barre, is the largest natural lake (by volume) within the Commonwealth of Pennsylvania, and is one of the most heavily used lakes in the area. It is classified as a high quality – cold water fishery habitat (HQ-CWF) and is designated for protection under the classification.

Since 2002, The Borough of Harveys Lake and the Harveys Lake Environmental Advisory Council  has worked with Princeton Hydro on a variety of lake management efforts focused around maintaining high water quality conditions, strengthening stream banks and shorelines, and managing stormwater runoff.

Successful, sustainable lake management requires identifying and correcting the cause of eutrophication as opposed to simply reacting to the symptoms of eutrophication (algae and weed growth). As such, we collect and analyze data to identify the problem sources and use these scientific findings to develop a customized management plan that includes a combination of biological, mechanical, and source control solutions. Here are some examples of the lake management strategies we’ve utilized for Harveys Lake:

 

Floating Wetland Islands

Floating Wetland Islands (FWIs) are an effective alternative to large, watershed-based natural wetlands. Often described as self-sustaining, FWIs provide numerous ecological benefits. They assimilate and remove excess nutrients, like nitrate and phosphorous, that could fuel algae growth; provide habitat for fish and other aquatic organisms; help mitigate wave and wind erosion impacts; and provide an aesthetic element. FWIs are also highly adaptable and can be sized, configured, and planted to fit the needs of nearly any lake, pond, or reservoir.

Five floating wetland islands were installed in Harveys Lake 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.

Princeton Hydro worked with the Harveys Lake Environmental Advisory Council and the Borough of Harveys Lake to obtain funding for the FWIs through the Pennsylvania Department of Environmental Protection (PADEP).

 

Streambank & Shoreline Stabilization

Harveys Creek

The shoreline habitat of Harveys Lake is minimal and unusual in that a paved road encompasses the lake along the shore with most of the homes and cottages located across the roadway, opposite the lake. In addition to the lake being located in a highly populated area, the limited shoreline area adds to the challenges created by urban stormwater runoff.

Runoff from urban lands and erosion of streambanks and shorelines delivers nutrients and sediment to Harveys Lake. High nutrient levels in the lake contribute to algal blooms and other water quality issues. In order to address these challenges, the project team implemented a number of small-scale streambank and inlet stabilization projects with big impacts.

The work included the stabilization of the streambank downstream for Harveys Lake dam and along Harveys Creek, the design and installation of a riparian buffer immediately along the lake’s shoreline, and selective dredging to remove sediment build up in critical areas throughout the watershed.

 

Invasive Species Management

Hydrilla (Hydrilla verticillata), an aggressively growing aquatic plant, took root in the lake in 2014 and quickly infected 250 acres of the lake in a matter of three years. If left untreated, hydrilla will grow to the water’s surface and create a thick green mat, which prevents sunlight from reaching native plants, fish and other organisms below. The lack of sunlight chokes out all aquatic life.

In order to prevent hydrilla from spreading any further, Princeton Hydro and SePRO conducted an emergency treatment of the impacted area utilizing the systemic herbicide Sonar® (Fluridone), a clay-based herbicide. SonarOne, manufactured by SePRO, blocks hydrilla’s ability to produce chloroplasts, which in turn halts the photosynthetic process. The low-concentration herbicide does not harm fish, wildlife or people using the lake. Surveys conducted after the treatment showed it was working – the hydrilla had turned white and was dying off. Additional Sonar treatments followed and efforts to eradicate hydrilla in the lake continue.

Dr. Fred Lubnow, our Director of Aquatic Programs, estimates complete eradication of the aquatic plant could take around five years. Everyone can do their part in preventing the spread of this and other invasive species. Boaters and lake users must be vigilant and remove all vegetation from the bottom of watercrafts and trailers.

 

Stormwater Best Management Practices (BMPs)

In 2009, Princeton Hydro developed a stormwater implementation plan (SIP) for Harveys Lake. The goal of the stormwater/watershed-based efforts was to reduce the lake’s existing annual total phosphorus load to be in full compliance with the established Total Maximum Daily Load (TMDL). This TMDL is related to watershed-based pollutant loads from total phosphorus (TP) and total suspended solids (TSS), which can contribute to algal blooms.

A number of structural urban runoff projects were implemented throughout the watershed. This includes the design and construction of two natural stream channel projects restoring 500 linear feet of tributaries and reducing the sediment and nutrient loads entering the lake. A series of 38 urban runoff BMPs, including nutrient separating devices and roadside infiltration, were installed in areas immediately adjacent to the lake to further reduce the loads of nutrients and other pollutants reaching the lake.

The photos below show a stormwater project that was completed in the Hemlock Gardens Section of the Watershed. Hemlock Gardens is a 28-acre section of land located in the southeastern portion of the watershed. It contains approximately 26 homes, has very steep slopes, unpaved dirt roads, and previously had no stormwater infrastructure in place.

Two structural stormwater BMPs were installed:

  • A nutrient separating baffle box, which utilizes a three-chamber basin with screens to collect leaf litter, grass clippings and trash
  • A water polishing unit that provides a platform for secondary runoff treatment

In 1994, Harveys Lake was identified as “impaired” by PADEP due to large algal blooms. In 2014, Harveys Lake was removed from the list of impaired waters. Project partners attribute the recovery of this lake to the stream restoration, urban runoff BMP implementation, and the use of in-lake nutrient reduction strategies.

The Harveys Lake Watershed Protection Plan Implementation Project proved that despite the lake being located in an urbanized watershed, it is possible to implement cost-effective green infrastructure and stormwater retrofit solutions capable of significantly decreasing pollutant loading to the lake.

To learn more about our lake and pond management services or schedule a consultation, visit: http://bit.ly/pondlake.

A Day in the Life of a Stormwater Inspector

Walking through a park isn’t always a walk in the park when it comes to conducting stormwater inspections. Our team routinely spots issues in need of attention when inspecting stormwater infrastructure; that’s why inspections are so important.

Princeton Hydro has been conducting stormwater infrastructure inspections for a variety of municipalities in the Mid-Atlantic region for a decade, including the City of Philadelphia. We are in our seventh year of inspections and assessments of stormwater management practices (SMPs) for the Philadelphia Water Department. These SMPs are constructed on both public and private properties throughout the city and our inspections focus on areas served by combined sewers. 

Our water resource engineers are responsible for construction oversight, erosion and sediment control, stormwater facilities maintenance inspections, and overall inspection of various types of stormwater infrastructure installation (also known as “Best Management Practices” or BMPs).

The throat of a sinkhole observed by one of our engineers while on site.

Our knowledgeable team members inspect various sites regularly, and for some municipalities, we perform inspections on a weekly basis. Here’s a glimpse into what a day of stormwater inspection looks like:

The inspector starts by making sure they have all their necessary safety equipment and protection. For the purposes of a simple stormwater inspection the Personal Protection Equipment (PPE) required includes a neon safety vest, hard hat, eye protection, long pants, and boots. Depending on the type of inspection, our team may also have to add additional safety gear such as work gloves or ear plugs. It is recommended that inspectors hold CPR/First Aid and OSHA 10 Hour Construction Safety training certificates. 

Once they have their gear, our inspection team heads to the site and makes contact with the site superintendent. It’s important to let the superintendent know they’re there so that 1) they aren’t wondering why a random person is perusing their construction site, and 2) in case of an emergency, the superintendent needs to be aware of every person present on the site.

Once they arrive, our team starts by walking the perimeter of the inspection site, making sure that no sediment is leaving the project area. The team is well-versed in the standards of agencies such as the Pennsylvania Department of Environmental Protection, the Pennsylvania Department of Transportation, the New Jersey Department of Environmental Protection, and local County Soil Conservation Districts, among others. These standards and regulations dictate which practices are and are not compliant on the construction site.

After walking the perimeter, the inspection team moves inward, taking notes and photos throughout the walk. They take a detailed look at the infrastructure that has been installed since the last time they inspected, making sure it was correctly installed according to the engineering plans (also called site plans or drainage and utility plans). They also check to see how many inlets were built, how many feet of stormwater pipe were installed, etc.

If something doesn’t look quite right or needs amending, our staff makes recommendations to the municipality regarding BMPs/SMPs and provides suggestions for implementation.

One example of an issue spotted at one of the sites was a stormwater inlet consistently being inundated by sediment. The inlet is directly connected o the subsurface infiltration basin. When sediment falls through the inlet, it goes into the subsurface infiltration bed, which percolates directly into the groundwater. This sediment is extremely difficult to clean out of the subsurface bed, and once it is in the bed, it breaks down and becomes silt, hindering the function of the stormwater basin.

To remedy this issue, our inspection team suggested they install stone around the perimeter of the inlet on three sides. Although this wasn’t in the original plan, the stones will help to catch sediment before entering the inlet, greatly reducing the threat of basin failure.

Once they’ve thoroughly inspected the site, our team debriefs the site superintendent with their findings. They inform the municipality of any issues they found, any inconsistencies with the construction plans, and recommendations on how to alleviate problems. The inspector will also prepare a Daily Field Report, summarizing the findings of the day, supplemented with photos.

In order to conduct these inspections, one must have a keen eye and extensive stormwater background knowledge. Not only do they need to know and understand the engineering behind these infrastructure implementations, they need to also be intimately familiar with the laws and regulations governing them. Without these routine inspections, mistakes in the construction and maintenance of essential stormwater infrastructure would go unnoticed. Even the smallest overlook can have dangerous effects, which is why our inspections team works diligently to make sure that will not happen.

Our team conducts inspections for municipalities and private entities throughout the Northeast. Visit our website to learn more about our engineering and stormwater management services.

 

Volunteers Spruce Up Rain Gardens at Clawson Park

Volunteers recently gathered together at Clawson Park in Ringoes, NJ to install native plants in the park’s large stormwater basin and overhaul two of the park’s rain gardens, removing invasive weeds and planting beneficial native species.

By definition, a rain garden is a shallow depression that is planted with deep-rooted native plants and grasses and positioned near a runoff source to capture rainwater. Rain gardens temporarily store rainwater and runoff, and filter the water of hydrocarbons, oil, heavy metals, phosphorous, fertilizers and other pollutants that would normally find their way to the sewer and even our rivers and waterways. They are a cost effective, attractive, and sustainable way to minimize stormwater runoff. They also help to reduce erosion, promote groundwater recharge, and minimize flooding. Planting native plants helps to attract pollinators and birds and naturally reduces mosquitoes by removing standing water thus reducing mosquito breeding areas.

Once a rain garden has been established, it is low maintenance and typically only requires occasional weeding to remove any invasive species that may have cropped up. The recent volunteer effort, lead by Jack Szczepanski, PhD, Senior Aquatics Scientist, was an important step in maintaining the health and native diversity of Clawson Park’s rain gardens.

An informational sign was also installed at the park. Designed by Princeton Hydro and installed by the East Amwell’s Department of Public Works, the sign describes the benefits of stormwater management and planting native species.

The park’s rain gardens and stormwater basins were originally designed and implemented by Princeton Hydro. Back in 2016, Eagle Scout Brandon Diacont had an idea to beautify Clawson Park and improve the park’s stormwater drainage issues. Princeton Hydro supported his vision by developing, permitting, and implementing a stormwater management project plan, which included the installation of multiple rain gardens throughout the park. In October of 2016, under the guidance of Princeton Hydro’s Landscape Designer Cory Speroff, MLA, ASLA, CBLP, a great group of volunteers gathered together and got to work bringing the project plan to life!

 Photos from 2016 volunteer event:

The Princeton Hydro team has designed and constructed countless stormwater management systems, including rain gardens in locations throughout the Eastern U.S. Click here for more information about our stormwater management services.

Thank you to Patsy Wang Iverson for providing the photos for this blog.

Protecting Greenwood Lake’s Water Quality Through Stormwater Management

The summer is upon us and Lakes Appreciation Month is right around the corner, what better time to pay a visit to and learn more about the lakes in your area.

Princeton Hydro conducts work on lakes throughout the Northeast to preserve, protect and improve water quality and ecological health, ensuring that your community lakes can be enjoyed now and into the future. Today, we’re putting the spotlight on Greenwood Lake:

Greenwood Lake, a 7-mile-long interstate lake that straddles the border of New York and New Jersey, is a popular recreation spot for residents and tourists of both states. Considered to be one of the top bass fishing lakes in New Jersey, Greenwood Lake is abundant with largemouth and smallmouth bass, yellow perch, chain pickerel and catfish. The lake is also extensively used by residents for swimming and boating.

For over 35 years, Princeton Hydro’s scientists have worked with New Jersey, local governing municipalities, and the various environmental organizations involved with the protection of Greenwood Lake and its watershed. In the early 2000s, we developed a comprehensive Restoration Plan and a proactive monitoring program that we have used over the years to properly manage the lake and its watershed. The plan was developed for the Greenwood Lake Commission and the Township of West Milford with funding provided through the New Jersey Department of Environmental Protection’s Nonpoint Source 319(h) Program. The Restoration Plan focuses heavily on the implementation of various types of stormwater best management practices (BMPs) to help reduce the influx of sediment and nutrients into the lake. We track the positive effects and benefits achieved through these stormwater projects by conducting both storm-event based and in-lake water quality monitoring.

The goal of the stormwater-based efforts is to ensure the lake’s total phosphorus (TP) load is systematically reduced in accordance with the lake’s established Total Maximum Daily Load (TMDL). The TMDL is a regulatory term in the U.S. Clean Water Act, that identifies the maximum amount of a pollutant (in this case phosphorus) that a waterbody can receive while still meeting water quality standards. Princeton Hydro was instrumental in developing the TMDL for Greenwood Lake. Phosphorus entering the lake from runoff is the primary driver of the lake’s eutrophication. The direct results of eutrophication are increases in the density of aquatic plants and nuisance algae. All this added productivity leads to reduced clarity, reductions in dissolved oxygen concentrations, and a number of other ecological impacts that compromise the quality, aesthetics, and use of the lake.

Last year, Princeton Hydro and the Greenwood Lake Commission, with input from the West Milford Environmental Commission, proposed an updated Watershed Implementation Plan (WIP) for the lake. Approved and funded by the NJ Highlands Council, the updated WIP includes a variety of components that build upon the original Restoration Plan and incorporate newly advanced stormwater management and Nonpoint Source Pollution (NPS) reduction technologies.

Belcher's Creek at Edgecumb and Glencross

The WIP includes in‐lake and stream monitoring; the assessment of the existing stormwater structures installed through grant‐based, watershed activities; and the identification of watershed-based projects that can be completed to support the Lake’s compliance with TMDL TP levels with a specific focus on the stormwater runoff produced by Belcher’s Creek, a major tributary to Greenwood Lake.

The WIP also includes the following nine minimum elements considered necessary by both NJDEP and USEPA for funding eligibility:

  1. Identify causes and sources of pollution
  2. Estimate pollutant loading into the watershed and the expected load reductions
  3. Describe management measures that will achieve load reductions and targeted critical areas
  4. Estimate amounts of technical and financial assistance and the relevant authorities needed to implement the plan
  5. Develop an information/education component
  6. Develop a project schedule
  7. Describe the interim, measurable milestones
  8. Identify indicators to measure progress
  9. Develop a monitoring component

While many of these elements have been indirectly addressed to varying degrees in the original Restoration Plan, in order to maximize Greenwood Lake’s opportunities to obtain State and Federal funding for the design and implementation of watershed control measures, the WIP now explicitly correlates the nine elements to eight specific deliverables, which are as follows:

  1. Conduct a detailed in‐lake and watershed‐based water quality monitoring program and compare the data to that collected in 2004 and 2005 to document changes or shifts in water quality.
  2. Meet with the Township of West Milford, Passaic County and other stakeholders to
    inventory recently completed BMPs and other watershed management measures.
  3. Conduct a field‐based evaluation of the stormwater project completed since the original 319‐grant funded Restoration Plan.
  4. Conduct site assessments to identify other potential stormwater/watershed BMP projects.
  5. Conduct a field assessment of the Belchers Creek Corridor to identify potential Nonpoint Source Pollution Reduction Projects.
  6. Assemble the WIP with all the 9 elements fully satisfied.
  7. Schedule and implement stakeholder and public meetings to evaluate project status.
  8. Submit of final version of WIP to the NJDEP and present the findings and recommendations to the public.

This project was initiated in September 2018 and is projected for completion by September 2019. The Greenwood Lake Commission, serves as the inter‐State steward of the Greenwood Lake watershed, and is working closely with Princeton Hydro and the watershed stakeholders (Township of West Milford, Passaic County and others), to ensure the WIP is a holistic document.

Stay tuned for more Greenwood Lake updates as the WIP progresses. For more information about Princeton Hydro’s lake management projects and capabilities, or to discuss your project needs and goals, please contact us.

Some of the photos utilized in this blog are from The Village of Greenwood Lake.

Urban Wetland Restoration to Yield Flood Protection for Bloomfield Residents

As part of the Third River Floodplain Wetland Enhancement Project,
a disturbed, flood-prone industrial site will be converted into a thriving public park.

Along the Third River and Spring Brook, two freshwater tributaries of the Passaic River, a disturbed industrial site is being transformed into 4.2 acres of wetlands, restoring the natural floodplain connection, enhancing aquatic habitat, and increasing flood storage capacity for urban stormwater runoff. The groundbreaking ceremony for this important ecological restoration project for Bloomfield Township took place last month.

“The Third River Floodplain Wetland Enhancement Project is a unique, creative solution that will transform a highly-disturbed, flood-prone, former industrial site into a thriving public park allowing for both passive and active recreational activities,” said Mark Gallagher, Vice President of Princeton Hydro. “By removing a little over four acres of upland historic fill in this densely developed area and converting it to a functioning floodplain wetland, the project will restore valuable ecological functions, increase flood storage capacity, and enhance wildlife habitat.”

Princeton Hydro is serving as the ecological engineer to Bloomfield Township for the Third River Floodplain Wetland Enhancement Project. Princeton Hydro’s scientists and engineers have assisted in obtaining grants, collected background ecological data through field sampling and surveying, created a water budget, completed all necessary permitting, and designed both the conceptual and final restoration plans. Additionally, Princeton Hydro will be conducting construction oversight during the implementation of this important urban wetland creation project.

The site includes 1,360 feet along the east bank of the Third River and 3,040 feet along the banks of the Spring Brook. These waterways are freshwater tributaries of the Passaic River and share a history of flooding above the site’s 100-year flood plain. The Third River, like many urban streams, tends to be the victim of excessive volume and is subjected to erosion and chronic, uncontrolled flooding. This green infrastructure project will re-establish the natural floodplain wetland and riparian plant communities, which will lead to a species-rich forest community through the removal of invasive species, setting the stage for native plants.

“Over 500 trees and shrubs will be planted in the new wetland with additional trees and shrubs being planted along Lion Gate Drive and in existing woodlands. The selected native plant species all provide important wildlife value such as providing fruit for migratory birds,” Gallagher explained. “We are excited to work with Bloomfield Township to design an urban restoration project that will both enhance the site’s ecological and flood storage value and provide accessibility to the community of Bloomfield.”

It is estimated that Phase One of the project, which includes the wetland construction and plantings, will be completed by September 1, 2019. The maintenance building, concession stand, ball field, etc., will be constructed as part of Phase Two.

“We are very excited to break ground on this exciting project that will have tremendous public benefits, like providing much-needed open space and lowering flood insurance rates for nearby residents and businesses,” said Bloomfield Township Mayor Michael Venezia. “By taking an underutilized parcel of land and turning it into beautiful park and waterfront space to be enjoyed by the public, we are fulfilling our commitment to preserving and enhancing open space. We would not have accomplished this without the efforts of Councilman Nick Joanow, who has advocated for this park for many years, Township Administrator Matthew Watkins, our excellent contractors and environmental experts, and I would like to thank them all. I also want to thank the Department of Environmental Protection and Freshwater Wetlands Mitigation Council for their important grant assistance to help us jump start this complex which will enrich the lives of Bloomfield residents for decades to come.”

NY/NJ Baykeeper has been vital in bringing the project to fruition, having served as an advocate for the project for the last 17 years.

“Lion’s Gate natural restoration is a legitimate all-in-one project that uses green infrastructure and smart planning to address the nested set of urban land use challenges, including: stormwater management, flooding, brownfield cleanup, natural habitat restoration, and the need for both more active playing fields and more passive greenfields,” said Greg Remaud, Baykeeper and CEO, NY/NJ Baykeeper.

Together, Bloomfield Township, Strauss and Associates, ARH, and Princeton Hydro secured $1.76 million in funding for this project from the New Jersey Freshwater Wetlands Mitigation Council and another several million dollars from NJDEP’s Office of Natural Resource Restoration.

To read more about our wetland restoration work, go here: http://bit.ly/PHwetland

 

NJ SPOTLIGHT OP/ED Addresses the Creation of Stormwater Utilities in New Jersey

NJ Spotlight recently published an Op/Ed piece co-authored by Association of New Jersey Environmental Commissions (ANJEC) Board of Trustees members John A. Thonet, P.E., P.P., and Dr. Stephen J. Souza, PhD.

The piece asserts the position that New Jersey needs stormwater utilities to provide a sustained source of local funding in order to improve and maintain stormwater infrastructure in communities throughout the state.

We’ve included an excerpt from the Op/Ed below:

NJ SPOTLIGHT OP-ED: NEW UTILITIES WOULD HELP NEW JERSEY FIGHT FLOODING AND POLLUTION

2018 will be one of the wettest years on record for the Garden State, and all that rain has resulted in frequent flooding, millions of dollars in damages, gridlocked traffic, impacted drinking water and polluted waterways.

The problem is daunting, but there is a solution. For decades, the state has provided comprehensive planning and regulations aimed at protecting the public from the flooding impacts of improperly and inadequately managed stormwater. These efforts have helped but failed to address all the social, economic and environmental impacts associated with stormwater runoff. Today, rather than continuing to use conventional “collect, detain and discharge” approaches to controlling runoff, the use of “green infrastructure” is proving to be a better alternative. It’s focused on reducing runoff at its source, through recharge, reuse and evapotranspiration, rather than just treating it as a “waste” or “nuisance” to get rid of as quickly as possible.

Green infrastructure measures include porous pavement, green roofs, rain barrels, rain gardens, bioretention basins and other techniques designed to capture rainwater and allow it to soak into the ground instead of concentrating and discharging it downstream. Additionally, the “green infrastructure” approach is far more attractive and provides ecological and community benefits that can’t be achieved with standard detention basins.

So, what’s the hold-up? The answer is the absence of a sustained source of local funding to implement and maintain new stormwater infrastructure, including green infrastructure, as well as to retrofit, upgrade or replace failing existing stormwater management facilities…

Click Here to Read the Complete Op/Ed

 

About the Op/Ed Authors: 

John A. Thonet, P.E., P.P., is the president of Thonet Associates, Inc, an environmental, planning and engineering consulting firm based in Pittstown, NJ.

Dr. Stephen J. Souza, PhD is the owner of Clean Waters Consulting, LLC, a water resource consulting firm based in Ringoes, NJ that provides consulting services to Princeton Hydro, of which Steve is one of the founding principals.

Conservation Spotlight: Reducing Flood Risk and Restoring Wetlands in Jamaica Bay

Located in Queens, New York on the northern shore of Jamaica Bay, Spring Creek South contains approximately 237 acres of undeveloped land, including wetlands and 2.4 miles of coastline. The site is bounded by the Howard Beach residential neighborhood in Queens, a commercial area along Cross Bay Boulevard, the Belt Parkway, and Jamaica Bay. The northwest section of Spring Creek South is part of the National Park Service’s Gateway National Recreation Area, and is largely comprised of small patches of degraded tidal marsh and disturbed and degraded upland ecosystems.

On October 29, 2012, Hurricane Sandy drove a catastrophic storm surge into the New Jersey and New York coastlines. Spring Creek South and the surrounding community of Howard Beach experienced record flooding and damage to property and critical infrastructure. Storm tides caused damage and erosion along the shoreline and in the salt marsh area, degrading important habitat and leaving the site vulnerable to invasive species.

Hurricane Sandy Aftermath at Howard Beach, taken 10/30/2012 by Pam Andrade

The New York State Division of Homeland Security and Emergency Services (NYSDHSES) was awarded funding from FEMA’s Hazard Mitigation Grant Program to restore Spring Creek South. The U.S. Army Corps of Engineers (USACE) New York District, serving as project administrator, contracted Princeton Hydro to provide ecosystem restoration services. The goal of the project is to reduce future flood risk exposure while also protecting, restoring, and improving the quality and function of ecological systems; improving stormwater management and water quality; and enhancing the park’s visitor experience.

To achieve this goal, the project team is using an integrated approach that involves utilizing green infrastructure to create a natural barrier for the community and reduce the risks of coastal storms. Project activities include berm construction and the restoration of tidal marsh, creation of freshwater wetland forest, and creation of maritime shrub, forest, and grassland habitats, as well as stabilization of the existing shoreline.

On December 31, 2018, we completed Phase One of the project, which entails engineering design and preliminary permitting. More specifically, we’ve provided conceptual planning; analysis of subsurface soils for geotechnical properties and hazardous waste; coastal and freshwater wetland delineations; biological benchmarking analysis; and the development of sea level rise curves and two-dimensional hydrologic and hydraulic coastal modeling. As part of the hydrology study, we analyzed what the site could be expected to look like in 50 years due to climate changes and sea level rise. Our engineering design was also brought to 65% completion.

We also obtained permits, prepared the Environmental Assessment (EA), and oversaw the National Environmental Policy Act (NEPA) process. The EA received a “Finding of No Significant Impact” (FONSI) from FEMA, which means the environmental analysis and interagency review concluded that the project has no significant impacts on the quality of the environment.

Due to the complex nature of this project and its location, we are coordinating with a variety of different entities, including the local Howard Beach Community Board, the FAA (proximity to JFK International Airport), Port Authority, USACE, NOAA Fisheries, USFWS, USEPA, NYSDEC, NYC DEP, the National Park Service, HDR Engineering and WSP Engineering.

Phase Two of the project is the construction phase, which is expected to take about two years to complete. A key part of the Spring Creek South construction activities is the restoration of approximately 40 acres of tidal marsh, which is anticipated to improve water quality locally by stabilizing sediment, reducing erosion, and filtering dissolved particulate materials. The project team will restore existing coastline areas and install a salt marsh along the shoreline. Planted with native flora, like Spartina alterniflora, a perennial deciduous grass found in intertidal wetlands, the coastal salt marsh will help to stabilize sediment. Additionally, removing invasive species like Phragmites australis from the area and replacing it with native plant species will increase the ability for native vegetation to colonize the site, improve vegetative diversity, and reduce fire risk in the park.

A forested wetland area and berm will also be created in order to provide the surrounding communities with natural shields and buffers to future storms. The berm, with an elevation of 19 feet (NAVD88), will help to manage the risk of storm surge flooding caused by coastal storms. The forested wetland area will also provide improved stormwater runoff storage, naturally filter stormwater, and, via flap gates, direct its flow toward Jamaica Bay, away from residential and commercial properties.

These measures will help to dissipate wind and wave energy, increase shoreline resilience, improve stormwater management at the site, and create habitat that increases the ecological value and biodiversity at the site, while providing resilience benefits. Restoration activities will benefit vulnerable and rare ecological communities by producing localized environmental enhancements, including improving water quality and creating and restoring habitat. The project also increases opportunities for recreational uses such as wildlife viewing/photography, fishing, and nature study.

Princeton Hydro specializes in the planning, design, permitting, implementing, and maintenance of wetland rehabilitation projects. To learn more about some of our ecosystem restoration and enhancement services, visit: bit.ly/PHwetland.