Understanding and Implementing Green Infrastructure

By Tucker Simmons and Dr. Clay Emerson, PE, CFM

People generally think of green infrastructure as an eco-friendly way to handle stormwater runoff. While many green infrastructure elements are planned and managed specifically for stormwater control, the capabilities and benefits are far reaching. In this piece, we’ll provide an in-depth look at all that green infrastructure encompasses, best practices, and real-world examples of green infrastructure projects in action.

WHAT IS GREEN INFRASTRUCTURE?

Defined as an approach to water management that protects, restores, or mimics the natural water cycle, green infrastructure can be implemented for large scale projects and small scale projects alike.

Unlike conventional, or “gray” infrastructure, green infrastructure uses vegetation, soil, and other natural components to manage stormwater and generate healthier urban environments. Green infrastructure systems mimic natural hydrology to take advantage of interception, evapotranspiration and infiltration of stormwater runoff at its source. Examples include permeable pavers, rain gardens, bioretention basins, rain barrels, and tree boxes.

WHY IS GREEN INFRASTRUCTURE BENEFICIAL?

Green infrastructure provides various benefits, including cleaning and conserving water, reducing flooding, improving public health, providing jobs, beautifying neighborhoods, supporting wildlife and providing economic benefits at both the larger community and individual household level. Let’s take a closer look at some of the primary benefits:

Prevents Flooding: By absorbing and slowing the flow of water, green infrastructure can reduce the burden on storm sewer systems and mitigate localized flooding.

Saves Money: While some green infrastructure designs may require the same or greater initial investment than conventional strategies, green design methods provide a big return in reducing costs over the long-term.

Improves Water Quality: Through natural absorption and filtration processes, green infrastructure significantly reduces stormwater runoff volume, decreases the pollutants and particulates within the stormwater, and improves the quality of the runoff flowing into surrounding water bodies.

Improves Air Quality: Green infrastructure techniques like tree boxes, green roofs and vegetative barriers have long been associated with improving air quality. Urban tree boxes help shade surfaces, effectively putting moisture into the air while reducing greenhouse gases. Trees mitigate heat and air pollution, both cooling and cleaning the air.

Enhances Aesthetics: Many green infrastructure practices utilize native plants and trees to improve runoff absorption and reduce stormwater pollution. This vegetation can provide a sound barrier or privacy screen for properties, and enhances the overall aesthetics of the surrounding environment. 

Increases Property Values: Research shows that property values increase when trees and other vegetation are present in urban areas. Planting trees can increase property values by as much as 15%.

LARGE-SCALE GREEN INFRASTRUCTURE IMPLEMENTATION:

With the use of proper design techniques, green infrastructure can be applied almost anywhere and is especially beneficial in urban areas. In developed environments, unmanaged stormwater creates two major issues: one related to the volume and timing of stormwater runoff (flooding) and the other related to pollutants the water carries. Green Infrastructure in urban environments can recharge groundwater, decrease runoff, improve water quality, and restore aquatic habitats while controlling flooding.

Across the United States, more than 700 cities utilize combined sewer systems (CSS) to collect and convey both sanitary sewage and stormwater to wastewater treatment facilities. During dry weather, all wastewater flows are conveyed to a sewage treatment plant where it receives appropriate treatment before it is discharged to the waterway. However, during heavy rainfall or significant snowmelt, the additional flow exceeds the capacity of the system resulting in a discharge of untreated sewage and stormwater to the waterway; this discharge is referred to as a combined sewer overflow (CSOs). For many cities with CSS, CSOs remain one of the greatest challenges to meeting water quality standards. Green infrastructure practices mimic natural hydrologic processes to reduce the quantity and/or rate of stormwater flows into the CSS.

New Jersey, as part of the 2012 USEPA’s Integrated Municipal Stormwater and Wastewater Planning Approach Framework, utilized green infrastructure as one of the main components in managing its CSS and reducing CSOs. Because of the flexibility of green infrastructure in design performance, it can reduce and mitigate localized flooding and sewer back-ups while also reducing CSOs. An integrated plan that addresses both overflows and flooding can often be more cost-effective than addressing these issues separately. New Jersey, in addition to meeting its CSO reduction goals, is using green infrastructure throughout the sewershed to build resilience to large storm events and improve stormwater management.

Stormwater planters installed by the Philadelphia Water Department

Philadelphia takes advantage of numerous green stormwater infrastructure programs such as Green Streets, Green Schools, and Green Parking. There are a wide variety of green infrastructure practices that Philadelphia is using to decrease stormwater runoff throughout the entire city. After just five years of implementing the Green City, Green Waterplan, Philadelphia has reduced the stormwater pollution entering its waterways by 85%. Using over 1,100 green stormwater tools (i.e. CSO, living landscapes, permeable surfaces, etc.), in just one year, Philadelphia was able to prevent over 1.7 billion gallons of polluted water from entering their rivers and streams.

New York City is using a green infrastructure program, led by its Department of Environmental Protection, that utilizes multiple green infrastructure practices to promote the natural movement of water while preventing polluted stormwater runoff from entering sewer systems and surrounding waterbodies. While attaining this goal, the green infrastructure also provides improvements in water and air quality, as well as improves the aesthetics of the streets and neighborhoods. According to the NYC Green Infrastructure Plan, “By 2030, we estimate that New Yorkers will receive between $139 million and $418 million in additional benefits such as reduced energy bills, increased property values, and improved health.”

SMALL-SCALE GREEN INFRASTRUCTURE IMPLEMENTATION:

Green infrastructure techniques are extremely beneficial on every scale. Residential homes and neighborhoods can benefit from the implementation of green infrastructure in more ways than many people realize. There are a wide variety of green infrastructure projects that can be completed with a relatively small time and financial investment. Many of us at Princeton Hydro have incorporated green infrastructure practices into our homes and properties. Here’s a look at some of those projects in action:

Dr. Steve Souza, a founding principal of Princeton Hydro, installed rain gardens throughout his property utilizing native, drought-resistant, pollinator-attracting plants. The rain gardens are designed to capture and infiltrate rainwater runoff from the roof, driveway, patio and lawn.

Princeton Hydro’s President Geoffrey Goll, P.E. built an infiltration trench in his backyard. An infiltration trench is a type of best management practice (BMP) that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in adjacent waterways. 

And, in the front yard, Geoffrey installed a variety of wildflower plantings.

MUNICIPAL TOOLKIT

An interactive website toolkit was recently launched by New Jersey Future to help municipalities across the state incorporate green infrastructure projects into their communities. For this project, Princeton Hydro’s engineers and scientists provided real-world examples integrating green infrastructure into development in order to bring to light the benefits and importance of investing in green infrastructure at the local level. The New Jersey Green Infrastructure Municipal Toolkit provides expert information on planning, implementing, and sustaining green infrastructure to manage stormwater. This toolkit acts as a one-stop resource for community leaders who want to sustainably manage stormwater, reduce localized flooding, and improve water quality.

GET STARTED

Since its inception, Princeton Hydro has been a leader in innovative, cost-effective, and environmentally sound stormwater management systems. Long before the term “green infrastructure” was part of the design community’s lexicon, the firm’s engineers were integrating stormwater management with natural systems to fulfill such diverse objectives as flood control, water quality protection, and pollutant reduction. Princeton Hydro has developed regional nonpoint source pollutant budgets for over 100 waterways. The preparation of stormwater management plans and design of stormwater management systems for pollutant reduction is an integral part of many of the firm’s projects.

Interested in working with us on your next Green Infrastructure project? Contact us here.


Tucker Simmons, Water Resources Intern

Tucker is a Civil and Environmental Engineering major at Rowan University focusing on Water Resources Engineering. He is the President and player of the Rowan University Men’s DII Ice Hockey Team. His Junior Clinic experience includes the study of Bio-Cemented sand and the Remote Sensing of Landfill Fires. In the future, Tucker hopes to work on creating a more sustainable environment. Tucker enjoys playing ice hockey, being with friends and family, and exercising.

 

Clay Emerson, Senior Project Manager

Clay’s areas of expertise include hydrologic and hydraulic analysis, stormwater management and infiltration, nonpoint source (NPS) pollution, watershed modeling, groundwater hydrology/modeling, and water quality and quantity monitoring at both the individual site and watershed scales. His educational and work experience includes a substantial amount of crossover between engineering and environmental science applications. He has specific expertise in the field of stormwater infiltration and has conducted extensive research on the NPS pollution control and water quantity control performance of stormwater BMPs. He regularly disseminates his monitoring results through numerous peer-reviewed journal publications, magazine articles, and presentations.

 

Two-Part Blog Series: Flood Assessment, Mitigation & Management

In this two part blog series, we showcase our work in the Moodna Creek Watershed in order to explore some of the concepts and methods used to estimate flood risk for existing conditions and the year 2050 and develop a flood management strategy (Part One), and traditional engineering and natural systems solutions used to manage and reduce flood risk (Part Two).

Part One: Flood Assessment & Mitigation Analysis in the Moodna Creek Watershed

The greater Moodna Creek watershed covers 180 square miles of eastern Orange County, NY. The watershed includes 22 municipalities and hundreds of streams before joining the Hudson River. This region has seen tremendous growth in recent years with the expansion of regional transit networks and critical infrastructure.

The Moodna Creek watershed can be split into two sub-basins — the Upper Moodna Creek and the Lower Moodna Creek. In the span of 15 months, Hurricane Irene, Tropical Storm Lee, and Hurricane Sandy each have caused significant flooding throughout the Moodna Creek watershed, damaging public facilities, roadways, and private properties. Both sub-basin communities have noted a concern about increased flood risk as more development occurs.

As global temperatures rise, climate models are predicting more intense rainfall events. And, the flood risk for communities along waterways — like the Moodna Creek watershed — will likely increase as time passes. In order to understand existing and future risk from flood events in this flood-prone area, a flood risk management strategy needed to be developed. The strategy uses a cost-benefit analysis to review the feasibility of each measure and the overall impact in reducing flood risks.

With funds provided from a 2016 grant program sponsored by the New England Interstate Waters Pollution Control Commission (NEIWPCC) and the New York State Department of Environmental Conservation’s (NYCDEC) Hudson River Estuary Program (HEP), Princeton Hydro along with a variety of project partners completed a flood assessment and flood mitigation analysis specific to the Lower Moodna Creek watershed.

Let’s take a closer look at our work with the Lower Moodna Creek watershed, and explore some of the methods used to estimate flood risk and develop a flood management strategy:

Lower Moodna Creek Watershed Flood Assessment & Analysis

The primary Lower Moodna Creek project goals were to assess flood vulnerabilities and propose flood mitigation solutions that consider both traditional engineering strategies and natural systems solution approaches (land preservation, wetland/forest restoration, green infrastructure and green water management). The project team focused on ways to use the natural environment to reduce risk.  Instead of strictly focusing on just Moonda Creek, the team took a holistic approach which included all areas that drain into the river too. These analyses were incorporated into a Flood Assessment Master Plan and Flood Mitigation Plan, which will serve as a road map to reducing flooding issues within the watershed.

Managing Flood Risk

The first step in managing flood risk is to understand what type of exposure the communities face. The Moodna Creek project modeled flooding within the watershed during normal rain events, extreme rain events, and future rain events with two primary goals in mind:

Visual assessment being conducted in flood-prone areas of Moodna Creek Watershed.

  • Assess the facilities, infrastructure, and urban development that are at risk from flooding along the Moodna Creek and its tributaries within the study area.
  • Develop a series of hydrologic and hydraulic models to assess the extent of potential flooding from the 10-year (10%), 100-year (1%),  and 500-year (0.2%) storm recurrence intervals within the study area. The modeling includes flows for these storm events under existing conditions and also hypothetical scenarios with predicted increases in precipitation and population growth.

 

The project team used these models and data to propose and evaluate a series of design measures that help reduce and mitigate existing and anticipated flood risk within the study area. Where possible, the proposed solutions prioritized approaches that protect and/or mirror natural flood protection mechanisms within the watershed such as floodplain re-connection and wetland establishment. In addition to flood protection, the project components also provide water quality protection, aesthetics and recreation, pollutant reduction, and wildlife habitat creation.

Land Use and Zoning

Zoning is a powerful tool that determines a region’s exposure to hazards and risk. Zoning determines which uses are permitted, or encouraged, to be built in moderate and high-risk areas. It also prevents certain uses, such as critical facilities, from being built in those areas. Zoning is also a determinant of a region’s character and identity.

In the Lower Moodna Creek watershed, a large majority (82%) of land is zoned for residential use. However, in the flood-prone areas, there is a higher ratio of areas zoned for non-residential uses (commercial, industrial) than in areas that are zoned for potential future development. Specifically, within the 10-year storm recurrence floodplain, 30% of the land is zoned for industrial use. This is likely because several facilities, such as wastewater treatment plants and mills, require access to the river and were strategically developed to be within immediate proximity of waterfront access. The Lower Moodna zoning analysis demonstrated a general preference within watershed to limit residential use of flood-prone areas. 

Land Preservation

Preserving land allows for natural stormwater management, as well as limits the exposure of development, and minimizes sources of erosion within the watershed. Preserved land also maintains the hydrologic and ecologic function of the land by allowing rainwater to be absorbed or retained where it falls and thus minimizing run-off. If the land within the floodplain is preserved, it will never be developed, and therefore the risk — a calculation of rate exposure and the value of the potential damage — is eliminated.  Therefore, land preservation, both within the floodplains and in upland areas, is the best way to minimize flood damage.

Conserved riparian areas also generate a range of ecosystem services, in addition to the hazard mitigation benefits they provide. Protected forests, grasslands, and wetlands along rivers and streams can improve water quality, provide habitat to many species, and offer a wide range of recreational opportunities. Given the co-benefits that protected lands provide, there is growing interest in floodplain conservation as a flood damage reduction strategy.

Within the mapped Lower Moodna floodplains, our assessment determined that there appears to be a slight priority for preserving land most at-risk for flooding. This is likely a consequence of prioritizing land that is closest to riparian areas and preserving wetland areas, which are the most likely to experience flooding. Within the floodplains for the 10-year storm, approximately 22.7% is preserved. For the 100-year storm, approximately 21.2% of the land is preserved. Within the 500-year storm, this number drops slightly to 20.3%. These numbers are so close in part because the difference between the 10-year, 100-year, and 500-year floodplains are small in many areas of the watershed.

Hydrology and Hydraulics

Hydrology is the scientific study of the waters of the earth, with a particular focus on how rainfall and evaporation affect the flow of water in streams and storm drains. Hydraulics is the engineering analysis of the flow of water in channels, pipelines, and other hydraulic structures. Hydrology and hydraulics analyses are a key part of flood management.

As part of this flood assessment, Princeton Hydro created a series of hydrologic and hydraulic (H&H) models to assess the extent of potential flooding from the 10-year, 100-year, and 500-year storm recurrence intervals within the Lower Moodna. The modeling, which included flows for these storm events under existing conditions and future conditions based on predicted increases in precipitation and population growth, makes it easier to assess what new areas are most impacted in the future.

These are just a few of the assessments we conducted to analyze the ways in which flooding within the watershed may be affected by changes in land use, precipitation, and mitigation efforts. The flood models we developed informed our recommendations and proposed flood mitigation solutions for reducing and mitigating existing and anticipated flood risk.

Stay tuned for Part Two of this blog series in which we will explore flood risk-reduction strategies that include both traditional engineering and natural systems solutions. For more information about Princeton Hydro’s flood management services, go here: http://bit.ly/PHfloodplain.

 

November Events Spotlight: Conferences Throughout the Country

Princeton Hydro is participating in a variety of conferences taking place throughout the country that address topics ranging from lake management to green infrastructure resiliency:

October 30 – November 2: North American Lake Management Society (NALMS) Conference

NALMS is hosting its 38th International Symposium in Cincinnati Ohio, titled “Now Trending: Innovations in Lake Management.” This year’s symposium includes a robust exhibit hall, a variety of field trips, and a wide array of presentations on topics ranging from the latest in monitoring technologies to combating invasive species to nutrient and water quality management and more. Princeton Hydro’s Dr. Fred Lubnow, Director of Aquatic Programs, and Dr. Stephen Souza, Founder, both of whom have been members of NALMS since its inception, are presenting and exhibiting during the conference.

LEARN MORE

 

October 31 – November 2: Society for American Military Engineers (SAME) Small Business Conference (SBC)

SAME gives leaders from the A/E/C, environmental, and facility management industries the opportunity to come together with federal agencies in order to showcase best practices and highlight future opportunities for small businesses to work in the federal market. Princeton Hydro is proud to be attending the 2018 SAME SBC Conference, which is being held in New Orleans and co-locating with the Department of Veteran’s Affairs’ National Veterans Small Business Engagement. The program consists of networking events, small business exhibits, a variety of speakers and much more.

LEARN MORE & REGISTER

 

November 2: The 2nd Annual New Jersey Watershed Conference

We are a proud sponsor of this year’s New Jersey Watershed Conference, which is an educational event that aims to advance knowledge and communications on issues related to water quality and quantity across the state. The agenda features a variety of presentations from local experts on watershed management, stormwater, green infrastructure, and the problems and solutions related to the health of our watersheds. Princeton Hydro is exhibiting & our Marketing Coordinator, Kelsey Mattison, is leading a workshop on “How Social Media can be a Champion for your Watershed.”

LEARN MORE & REGISTER

 

November 4 – 8: 2018 American Water Resources Association Conference

The AWRA’s 53rd Annual Water Resources Conference is being held in Baltimore, MD. Community, conversations and connections are highlights of every AWRA conference and the 2018 conference will provide plenty of opportunities for all three, including an exhibitor hall, networking events, and variety of presentations and technical sessions. Princeton Hydro’s Christiana Pollack, GISP, CFM is giving a presentation on flood assessment and mitigation. 

LEARN MORE & REGISTER

 

November 8 – 10: Engineers Without Borders (EWB) USA Conference

The EWB, a nonprofit humanitarian organization that partners with developing communities worldwide in order to improve their quality of life, is hosting its USA National Conference in San Francisco.  The ​annual ​conference ​will ​address ​the ​theme ​“Engineers Unlock Potential.” ​Experts, ​practitioners, ​decision-makers, ​young ​professionals ​and ​students ​from ​a ​range ​of ​sectors ​will come together to network, exchange ideas, foster new thinking and develop solutions to the world’s most pressing infrastructure ​challenges. Princeton Hydro Staff Engineer Natalie Rodrigues, EIT, CPESC-IT, a EWB member, is attending the conference and presentation. Her session, titled “So You Think You Might Like to be an EWB Regional Officer or State Representative, ” is designed for those interested in taking the next step beyond Chapter or Project participation at EWB-USA, as well as for current Regional Steering Committee members who want to “amp up” their game.

LEARN MORE & REGISTER

 

November 13: Society for American Military Engineers (SAME) Philadelphia Resiliency Symposium

SAME Philadelphia is hosting an all day symposium featuring experts on infrastructure resiliency in the face of extreme storms, flooding and other natural disasters. Presentation topics include, Flood Hazard Risk and Climate Change Effects for Bulk Oil Storage Facilities; Post-Storm Infrastructure Improvements and Stream Restoration; and Resilience Risk Analysis and Engineering. Princeton Hydro President Geoffrey Goll, P.E. is giving a presentation titled, “Enhancing Coastal Habitat & Increasing Resiliency through Beneficial Reuse of Dredged Material in New Jersey.” We hope to see you there!

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November 16: NJ Chapter American Water Resources Association (NJ-AWRA) Future Risk Symposium

As the frequency and intensity of storm events changes, how should watershed managers, engineers, and planners make informed decisions for the future? NJ-AWRA’s 2018 Future Risk Symposium, held at Duke Farms in Hillsborough, NJ, will focus on Future Flooding in Riverine Systems with presentations on climate trends, modeling, and planning that can be used in NJ to prepare for future flood events in New Jersey’s riverine systems. Princeton Hydro’s Christiana Pollack, GISP, CFM is giving a presentation on flood assessment, and the concepts and methods used to estimate flood risk for existing conditions and the year 2050.

LEARN MORE & REGISTER

 

STAY TUNED FOR MORE EVENT SPOTLIGHTS!

Efforts to Manage Hydrilla in Harveys Lake Prove Difficult but Effective

Collaboration between state agencies and local organizations in Luzerne County bring in grant money to determine Hydrilla infestation levels in Harveys Lake. Treatment efforts are scheduled for 2019.

Story provided by Princeton Hydro Senior Limnologist Michael Hartshorne, and originally published in the Pennsylvania iMapInvasives Fall 2018 Newsletter

Hydrilla (Hydrilla verticillata)

Hydrilla (Hydrilla verticillata) is a relatively new invasive plant in Pennsylvania with the first documented occurrence in 1989 in Adams County. Still, it was not until recently that lake managers, park rangers, and others in the natural resource field have turned their attention to this aggressive invader. Looking incredibly similar to our native waterweed (Elodea canadensis), hydrilla differs in that it is comprised of 4-8 whorled, toothed leaves in contrast to the smooth edged, 3-leaved whorl of E. canadensis.

 

Harveys Lake, located in the Borough of Harveys Lake (Luzerne County) is a large, deep glacial lake with limited littoral (i.e., shoreline) habitat. A significant body of work has been conducted at the lake with the original Phase I: Diagnostic-Feasibility Lake study conducted in 1992 and a Total Maximum Daily Load (TMDL) issued for phosphorus in 2002.

From 2002 to present, Princeton Hydro has assisted the Borough in the restoration of the lake with a heavy focus on stormwater best management practices (BMPs) supplemented by routine, in-lake water quality monitoring. The goal of the storm water/watershed-based efforts was to reduce the lake’s existing, annual total Hydrilla (Hydrilla verticillata) phosphorus load so it’s in full compliance with the established TMDL.

Mapped locations noted in 2014 and 2015 of hydrilla in Harveys Lake as documented in the Pennsylvania iMapInvasives database.

Over the last 15 years, the installation of these watershed-based projects has led to improved water quality conditions; specifically, phosphorus and algae concentrations have been reduced. While water quality conditions improved Harveys Lake, it was during one of the routine, summer water quality monitoring events conducted in July 2014 that a dense stand of hydrilla was noted at the Pennsylvania Fish and Boat Commission’s public boat launch. More than likely, the plant entered the lake as a “hitchhiker” on the boat or trailer being launched from this public boat launch by someone visiting the lake.

Hydrilla (Hydrilla verticillata) Credit: Nick Decker, DCNR Bureau of State Parks

Since the initial identification and confirmation of the hydrilla, the Borough of Harveys Lake has worked in conjunction with the Harveys Lake Environmental Advisory Council, the Luzerne County Conservation District, the Pennsylvania Department of Environmental Protection, and Princeton Hydro to secure funding for additional surveys to determine the spatial extent and density of growth followed by an aggressive eradication plan.

Grant funds already allocated to Harveys Lake under the state’s Non-Point Source Pollution Program were used to conduct a detailed boat-based and diving aquatic plant survey of Harveys Lake to delineate the distribution and relative abundance of the hydrilla in 2014. During these surveys, the distribution of the hydrilla was found to be limited to the northern portion of the lake with the heaviest densities just off the boat launch with plants observed growing in waters 20-25 feet deep.

A follow-up survey had shown hydrilla coverage to increase from 38% of surveyed sites to 58% of sites in 2016 with hydrilla now present at the lake’s outlet area. Spatial coverage of hydrilla increased from approximately 50 acres in 2014 to 210 acres in 2016, an increase of 160 acres.

This map shows the 2018 proposed treatment area of Harvey’s Lake. Due to funding issues, treatment is now scheduled for 2019. The current hydrilla distribution encompasses the entire littoral zone of Harvey’s Lake.

In hopes of preventing hydrilla escaping into the lake’s outlet stream, the Borough of Harveys Lake funded an emergency treatment of the two-acre outlet area in 2016 utilizing the systemic herbicide Sonar® (Fluridone). A follow-up treatment of 159 acres was conducted in 2017, again utilizing the Fluridone-based systemic herbicide.

The next treatment, which will attempt to cover the majority of the littoral habitat covered by hydrilla, is scheduled for late spring/early summer of 2019. It should be noted that Sonar® is being applied at a low concentration that is effective at eradicating the hydrilla, but will not negatively impact desirable native plant species.

The treatments conducted to date have documented some reductions in the vegetative coverage of hydrilla as well as tuber production relative to the original plant surveys conducted in 2016. However, it is recognized that it will take multiple years of treatment to eradicate this nuisance plant from the lake, as well as a highly proactive, interactive program to educate residents as well as visitors to the lake in preventing the re-introduction of this or other invasive species to Harveys Lake.

 

The successful, long-term improvement of a lake or pond requires a proactive management approach that addresses the beyond simply reacting to weed and algae growth and other symptoms of eutrophication. Our staff can design and implement holistic, ecologically-sound solutions for the most difficult weed and algae challenges. Visit our website to learn more about Princeton Hydro’s lake management services: http://bit.ly/pondlake

Michael Hartshorne‘s  primary areas of expertise include lake and stream diagnostic studies, TMDL development, watershed management, and small pond management and lake restoration. He is particularly skilled in all facets of water quality characterization, from field data collection to subsequent statistical analysis, modeling, technical reporting, and the selection and implementation of best management practices. He has extensive experience in utilizing water quality data in concert with statistical and modeling packages to support load reduction allocations for the achievement of water quality standards or tailored thresholds set forth to reduce the rate of cultural eutrophication. He also has significant experience in conducting detailed macrophyte, fishery, and benthic surveys.

Mitigation Milestone Reached at Mattawoman Creek Mitigation Site

Photo courtesy of GreenVest

Mattawoman Creek Mitigation Project will Restore and Protect 80+ Acres of Mattawoman Creek, Chesapeake Bay’s Most Productive Tributary

As one of the Chesapeake Bay’s most productive tributaries and a vital part of Maryland’s natural resources, Mattawoman Creek supports some of the largest populations of finfish, amphibians, and birds in the state. A collaborative team of private and public sector entities have designed the “Mattawoman Creek Mitigation Site” in Pomfret, Charles County, Maryland, an effort that will enhance or create 64+ acres of wetlands and restore nearly 3,800 linear feet of this perennial stream.  With over 28,500 native trees and shrubs to be planted, this mitigation project will result in 80+ acres of continuous, forested wetland with complex and diverse vegetative communities. It is expected to provide a wide array of habitat to resident and transient wildlife, including birds, reptiles, invertebrates, amphibians and rare, threatened and endangered species.

Unique to this project, Mattawoman Creek Mitigation Site is Maryland’s first-ever Umbrella Mitigation Banking Instrument (UMBI) for federal and other government agency use.   A UMBI is the bundling of multiple mitigation banks into one agreement in order to streamline the regulatory approval process, thereby eliminating steps and involving fewer resources. The Maryland UMBI document helps the USAF and other public agencies secure certainty of cost and schedule, facilitate timely permit issuance, and expedite the satisfaction of their permitted requirements for planned capital improvement projects. This approach also maximizes the scale of restoration and resulting land protection and efforts, creating contiguous blocks of habitat with greatly enhanced benefits compared to single, permittee-responsible projects. This precedent was a result of a partnership between United States Air Force (USAF) and Joint Base Andrews (JBA), U.S. Army Corps of Engineers (USACE), Maryland Department of the Environment (MDE), GreenTrust Alliance, GreenVest, and Princeton Hydro.

Projects completed under the UMBI will reduce federal and state workload expediting the regulatory review and issuance of permits by the MDE and USACE. Additionally, projects completed under this UMBI will aid in compliance with the Federal Paperwork Reduction Act where federal regulatory staff can evaluate success and performance issues for multiple permittees at one single habitat restoration or mitigation site. In addition, federal costs are capped, and liabilities  are transferred through to GreenVest, the private sector operator, and GreenTrust Alliance, the nonprofit bank sponsor, who will also serve as the long-term steward of sites restored under this program.

Pictured is the southern restoration area after
sorghum germination, prior to wetland creation
and reestablishment.
A function-based stream assessment was
performed on the degraded channel.

 

Photo courtesy of GreenVestDesign, engineering/modeling, and permitting of the site was completed by  Princeton Hydro and GreenVest under our currently Ecosystem Restoration contract with the USACE. Princeton Hydro also provided an Environmental Assessment and Environmental Baseline Survey, and conducted a geotechnical investigation, which included the advancement of test pits, visual and manual investigation techniques and logging, infiltration testing, laboratory soils testing, and seasonal high-water table estimations.

A wetland water budget was also developed for the proposed wetland creation and restoration to determine if sufficient water is available to establish or reestablish wetlands on the site. It was also used to inform design development including proposed grading and plant community composition. The establishment and re-establishment of wetlands on the site will be accomplished through directed grading, ditch plugging and stream restoration designed to maximize the retention of surface water, floodplain re-connection, and groundwater inputs.

Highlights from the Mattawoman Creek Wetland and Stream Mitigation project:
  • 80 acres of land were placed into conservation easement and removed from active row crop production and cattle pasture. The easement, which is held by GreenTrust Alliance, provides permanent protection for all 80 acres.
  • Over 64 acres of wetlands will be restored, created, enhanced or preserved, which will sequester approximately 75 tons of carbon per year.
  • 3,798 linear feet of perennial stream will be restored by re-establishing, historic floodplain access during more frequent storm events, stabilizing hydraulics and geomorphology, and adding aquatic habitat value.
  • Full integration of the wetland and stream restoration elements will occur exponentially, increasing anticipated functions and values in the post construction condition. Functions include: storm damage and flood attenuation, groundwater recharge and discharge, nutrient cycling and sequestration, local water quality improvement, and wildlife habitat enhancements.
  • This project will also create and enhance the forested wetland and stream habitat for the State-listed Threatened Selys’ Sundragon (Helocordulia selysii).
  • As part of the site design, over 28,500 native trees and shrubs will be planted.
  • The Mattawoman Creek Mitigation Site is located within a Tier 3 Biodiversity Conservation Network area. These areas are classified by the Department of Natural Resources as “highly significant for biodiversity conservation” and are priority conservation areas that support critical species and habitats.
  • The project will yield advanced mitigation values: 7.913 in wetland credits and 1,595 in stream credits. These credits are durable and will be available for JBA’s use in order to satisfy permitted impacts associated with planned capital improvement projects.

Over 6,000 acres (25%) of the Mattawoman Creek watershed has been protected by public ownership and various conservation and agricultural easements, which, in addition to the Mattawoman Creek Mitigation Site, help ensure that Mattawoman Creek forever remains a high-quality destination for outdoor recreation.

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

Princeton Hydro Joins American Sustainable Business Council

Princeton Hydro is proud to join the American Sustainable Business Council (ASBC), a coalition of businesses that prioritizes, “a triple bottom line of People, Planet, and Profit.” ASBC works to combat climate change by divesting from fossil fuels and investing in climate solutions, and passing carbon tax legislature at both federal and state levels. ASBC also works to address many other issues related to public health and the economy.

As a sustainable business headquartered in New Jersey, Princeton Hydro is also affiliated with the New Jersey Sustainable Business Council, the state chapter of the ASBC. In addition to joining the councils, Princeton Hydro’s President, Geoffrey Goll, P.E. joined the steering committee for ASBC’s “Clean Water is Good for Business” campaign.

“At Princeton Hydro, we are passionate about the protection of natural resources, fostering stewardship, and designing and conducting business in a sustainable manner. We believe in affecting positive change in our world for people and the environment,” said Goll. “We’re excited to align ourselves with an organization that reflects our core values, and we look forward to future sustainable business opportunities.”

The Clean Water is Good for Business campaign focuses on the Delaware River Watershed, a region that Princeton Hydro is actively working to protect and enhance. The campaign focuses on the importance of clean water, not just for human health, but for business health as well. Even companies that don’t directly rely on clean water for production of goods still need it to sustain day-to-day functions and keep employees healthy. ASBC recently released its Business Case where it lists the top priorities of the campaign as creating a comprehensive strategy, growing funding for conservation, and decreasing stormwater runoff.

Clean water is not only the key foundation to life itself, but a sustainable economy as well. Without clean water, we put our natural resources, businesses, and communities at risk. Protecting water quality is a long-term effort that requires continued investment, monitoring, and evaluation.

Princeton Hydro offers expertise in water resources management and engineering, ecosystems, and geotechnical investigations and design. Our staff provides a full suite of services throughout the Mid-Atlantic and New England states. Our capabilities are reflected in our award-winning projects that consistently produce real-world, cost-effective solutions. If you’re interested in learning how Princeton Hydro can help you, please contact us.

Innovative and Effective Approach to Wetland Restoration

The Pin Oak Forest Conservation Area is a 97-acre tract of open space that contains an extremely valuable wetland complex at the headwaters of Woodbridge Creek. The site is located in a heavily developed landscape of northern Middlesex County and is surrounded by industrial, commercial, and residential development. As such, the area suffered from wetland and stream channel degradation, habitat fragmentation, decreased biodiversity due to invasive species, and ecological impairment. The site was viewed as one of only a few large-scale freshwater wetland restoration opportunities remaining in this highly developed region of New Jersey.

Recognizing the unique qualities and great potential for rehabilitating and enhancing ecological function on this county-owned parkland, a dynamic partnership between government agencies, NGOs, and private industry, was formed to restore the natural function of the wetlands complex, transform the Pin Oak Forest site into thriving habitat teeming with wildlife, and steward this property back to life. The team designed a restoration plan that converted 28.94 acres of degraded freshwater wetlands, 0.33 acres of disturbed uplands dominated by invasive species, and 1,018 linear feet of degraded or channelized streams into a species-rich and highly functional headwater wetland complex.

BEFORE
View of stream restoration area upon commencement of excavation activities. View of containerized plant material staged prior to installation.

 

We used an innovative approach to restore the hydraulic connection of the stream channel with its floodplain in order to support wetland enhancement. Additionally, to further enhance wetlands with hydrologic uplift, the team incorporated microtopography techniques, which creates a variable surface that increases groundwater infiltration and niches that support multiple habitat communities. This resulted in a spectrum of wetland and stream habitats, including the establishment of a functional system of floodplain forest, scrub shrub, emergent wetlands and open water. Biodiversity was also increased through invasive species management, which opened the door for establishing key native flora such as red maple, pin oak, swamp white oak, and swamp rose. The restored headwater wetland system also provides stormwater quality management, floodplain storage, enhanced groundwater recharge onsite, and surface water flows to Woodbridge Creek.

Completed in 2017, the integrated complex of various wetland and upland communities continues to provide high quality habitat for a wide variety of wildlife species including the state-threatened Black-crowned Night heron and Red-headed Woodpecker. The work done at the site significantly enhanced ecological function, providing high-quality habitat on indefinitely-preserved public lands that offer countless benefits to both wildlife and the community.

AFTER
Post-restoration in 2018, looking Northeast. View of wetland enhancement approximately 2 months after completion of seeding and planting activities.

 

Public and private partnerships were and continue to be critical to the success of this project. The diverse partnership includes Middlesex County Office of Parks and Recreation, Woodbridge Township, Woodbridge River Watch, New Jersey Freshwater Wetlands Mitigation Council, GreenTrust Alliance, GreenVest, and Princeton Hydro. The partners joined together as stakeholders to identify long term restoration and stewardship goals for Pin Oak Forest Preserve, and nearly four years later, the partners all remain involved in various aspects of managing the property and this project itself, ranging from fiscal oversight by New Jersey Freshwater Wetland Mitigation Council and GreenTrust Alliance, to permit and landowner access coordination performed by Woodbridge Township and Middlesex County, or the ongoing stewardship, maintenance, and monitoring of the project and the larger park, being conducted by being conducted by GreenTrust Alliance, GreenVest, and NJ Department of Environmental Protection.

This project was funded through the New Jersey Freshwater Wetland In-Lieu Fee program. In 2014, GreenTrust Alliance, GreenVest, and Princeton Hydro secured $3.8 million dollars of funding on behalf of the Middlesex County Parks Department to restore three wetland sites, which included Pin Oak Forest.

The Pin Oak Forest project is a great model for showcasing a successful approach to the enhancement of public lands through a dynamic multidisciplinary, multi-stakeholder partnership. And, because of proper planning and design, it has become a thriving wildlife oasis tucked in the middle of a densely-populated suburban landscape.

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

Dam Removal Underway in Watertown, Connecticut

Deconstruction of the Heminway Pond Dam, Watertown, CT on July 16, 2018.

As dams age and decay, they can become public safety hazards, presenting a failure risk and flooding danger. According to American Rivers, “more than 90,000 dams in the country are no longer serving the purpose that they were built to provide decades or centuries ago.” Dam removal has increasingly become the best option for property owners who can no longer afford the rising cost of maintenance and repair work required to maintain these complex structures.

Dams can also cause environmental issues such as blocking the movement of fish and other aquatic species, inundating river habitat, impairing water quality, and altering the flow necessary to sustain river life. Removing nonfunctional, outdated dams can bring a river back to its natural state and significantly increase biodiversity for the surrounding watershed.

A view from the site of the Heminway Pond Dam removal on July 19, 2018.

Currently, work is underway in Watertown, Connecticut to remove the Heminway Pond Dam, which restricts fish passage in Steele Brook, creates a pond with increased water temperatures and high bacterial levels due to high geese populations, and encourages deposition of iron precipitate in the stream channel just downstream of the dam.

Princeton Hydro designed the engineering plans, managed permitting and is now overseeing construction for the removal project. The removal of the Heminway Pond Dam is identified as an integral component in addressing water quality impairment between the dam and Echo Lake Road.

CT DEEP recently published this piece encapsulating the Heminway Pond Dam removal project:

REMOVAL OF HEMINWAY POND DAM ON STEELE BROOK IN WATERTOWN UNDERWAY

Upstream at rock-filled breach in Heminway Pond Dam and shallow, dewatered impoundment on Steele Brook in Watertown (7-18-18)

After almost 15 years of discussion and planning with the Town of Watertown and other partners, removal of Heminway Pond Dam on Steele Brook in Watertown finally got underway in early July.  Though no longer functional, the dam and pond were originally constructed to supply water for a former thread/string mill.  The Town acquired the dam and pond from the Siemon Company, the most recent owner, in 2007 with an eye towards removing the dam, restoring the river and converting the dewatered impoundment area into a passive recreation area, including an extension of the Steele Brook Greenway.  With these goals in mind, the Town approached CT DEEP for help with removal of the dam.

As it turns out, CT DEEP, has also had a strong interest in seeing this dam removed.  It is anticipated that dam removal will improve the hydrology in this section of Steele Brook and eliminate a water quality impairment which manifests itself during hot weather and low flow conditions, as an orange-colored plume of water (due to iron precipitate) immediately downstream of the dam that impacts aquatic life.  Dam removal would also benefit fisheries by restoring stream connectivity and habitat.

Working towards these mutual goals, CT DEEP was able to provide federal CWA 319 nonpoint source grant funding to USDA NRCS to develop a watershed-based plan for Steele Brook to address nonpoint source impairments that includes a dam removal feasibility analysis for Heminway Pond Dam.  Based on the recommendations in this plan, CT DEEP subsequently provided additional 319 grant funds to the Town of Watertown to hire a consultant to develop a dam removal design package, and assist with permitting and preparation.

With the Town of Watertown as a strong and vested partner, CT DEEP is now helping this project over the finish line by providing a combination of 319 and SEP funds to accomplish the actual dam removal and restoration of Steele Brook.  Dayton Construction Company is performing the construction and Princeton Hydro is the consultant overseeing the project on behalf of the Town.  The Northwest Conservation District is also assisting with the project.  It is anticipated that the majority of the work will be completed by this Fall.  U.S. EPA, ACOE and CT DEEP have all played active roles with regard to permitting the project.

 

A view of the first notch during the Heminway Pond Dam removal on July 17, 2018.

Princeton Hydro has designed, permitted, and overseen the reconstruction, repair, and removal of dozens of small and large dams in the Northeast. Click here to read about a recent dam removal project the firm completed on the Moosup River. And, to learn more about our dam and barrier engineering services, visit: bit.ly/DamBarrier.

September Events Spotlight: Webinars, Conferences & Film Festival

Princeton Hydro is proud to participate in a number of conferences, events, and webinars throughout September:

 

September 6 at 12 pm: “Social Media Hacks” Webinar for the Society for American Military Engineers (SAME) Young Member Council 

SAME Young Member Council is hosting a webinar that will offer solutions for boosting social media presence and increasing engagement. Designed for social media beginners and experts alike, the webinar titled, “Social Media Hacks,” will be presented by Dana Patterson, Communications Strategist for Princeton Hydro. Participants will learn about creating successful social media strategy, utilizing free social media management tools, tracking social media analytics, and executing high-quality posts on various social media platforms. The webinar is free for SAME Members and $25 for all non-members.

Learn more and register.

 

September 9: Wild & Scenic Film Festival On Tour

Hosted by Musconetcong Watershed Association, the “Wild & Scenic Film Festival On Tour” celebrates the 50th Anniversary of the Wild and Scenic Rivers Act by bringing communities together to screen films that call attention to local and global environmental issues. The Hackettstown, NJ tour event, which Princeton Hydro is a proud sponsor of, will feature 11 short films including River Connections, a film that explores the importance of free-flowing rivers and highlights the recent Hughesville Dam removal project. An interactive panel event will follow the film screening and feature experts including MWA Executive Director Alan Hunt, Ph.D. and Princeton Hydro President Geoffrey Goll, P.E., who were both interviewed in the film. This event is free and open to the public, but registration is required.

Learn more and register.

 

September 12: Schuylkill Action Network’s (SAN) Water Utility Forum

This year’s SAN Forum will cover a variety of water-quality related topics, including perfluorinated compound (PFCs) and upcoming drinking water regulations. The forum will provide a platform to collaborate and share information, expertise, and technology to help achieve a shared vision of clean water and a healthy environment for the Schuylkill River and its tributaries. A variety of presentations will be offered during the forum, including one by Dr. Fred Lubnow, Director of Aquatics Programs for Princeton Hydro, on the topic of Harmful Algal Blooms (HABs).

Learn more and register.

 

September 15: Mercer County Park Commission’s River Days

Join Mercer County Park Commission for “River Days,” a free, family-friendly event at the Tulpehaking Nature Center with trail activities, arts and crafts, a raffle, and a neighborhood cookout on the back lawn of the nature center. Check out the Princeton Hydro air boat and chat with our Aquatics Field Director about the upcoming multi-year restoration of freshwater tidal wetlands in John A. Roebling Memorial Park. The restoration project is a partnership between Mercer County, New Jersey, Mercer County Park Commission, and Princeton Hydro.

Learn more.

 

September 23-26: 91st Annual Water Works Operators’ Association of Pennsylvania (WWOAP) Conference

WWOAP is hosting its 91st annual conference, which offers a diverse collection of professional presentations, workshops, networking events and an exhibit hall. Princeton Hydro’s Director of Aquatics Programs  Dr. Fred Lubnow is presenting on “Managing HABs and Their Associated Cyanotoxins in Raw Water.” Other presentation topics include “What Might Climate Change Look Like in Pennsylvania,” “A Multi-Lateral Approach to Water Loss Reduction,” and “Achieving Water Quality Optimization.”

View the full conference program.

 

September 25: New England Interstate Water Pollution Control Commission (NEIWPCC) Research Webinar

NEIWPCC is offering a free research webinar on modeling and flood-mitigation recommendations for a forested and urban Hudson River tributary watershed. The webinar takes a look at the Moodna Creek Watershed and Flood Mitigation Assessment and describes how flood models were used to inform recommendations for reducing and mitigating existing and anticipated flood risk. The assessment was conducted by environmental consultants at Princeton Hydro and GreenVest, and funded by NEIWPCC through the New York Department of Environmental Conservation’s Hudson River Estuary Program. This free webinar will be presented by Christiana Pollack, GISP, CFM, Environmental Scientist & GIS Manager for Princeton Hydro, and Jessica Jahre, CFM, AICP.

Learn more and register.

 

September 28: Alliance for NJ Environmental Education (ANJEE) Autumn Conference

Duke Farms will host ANJEE’s Autumn Conference, titled “Imagine a World Outdoors.” The conference, which takes place completely outdoors and does not include a single PowerPoint presentation, invites environmental education professionals throughout New Jersey to come together to collaborate around innovative ideas, learn and disseminate best practices, and network. Participants will explore natural history with local experts in birding, animal tracking, and plant identifying and learn trade secrets from experienced outdoor teachers who will share their methods and techniques. Princeton Hydro’s Dana Patterson and Pinelands Adventures’ Danielle Odom are teaching a workshop on “How to Bring Out the Inner Bird Nerd in your Students. ANJEE hopes the event will inspire participants to become more informed and dedicated stewards of the land.

Learn more and register.

 

Stay tuned for more event updates!

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

By Kevin Yezdimer, P.E. and Jim Hunt, P.E.

Just 25 miles east of Philadelphia, on the edge of the New Jersey Pinelands region, sits a network of 22 lakes that serve a multitude of recreation purposes for the residents of Medford Lakes. Serving as the guardian to these natural beauties is the Medford Lakes Colony (MLC), a private homeowner association. Homeowners in this community contribute to a “Lake Restoration Fund,” managed by MLC, which is used to maintain the water control structures and monitor the water quality for the bodies of water within the community. This dedicated fund is often used for dredging of the lake beds; repairs and replacement of dams, spillways, and culverts; installation of aerators or fountains to promote long-term benefits to water quality; treatments for weeds and algae; and the maintenance of the coves and beaches.

In mid-April, a concerning blockage developed in Lake Wauwauskashe Dam’s spillway and water was backing up at the upstream outlet structure. The 30-inch wide corrugated metal pipe serves as the dam’s primary (and only) outlet under Wagush Trail, a neighborhood road connecting Lake Wauwauskashe and Lake Mushkodasa. During the attempt to clear the mass of accumulated woody-debris via vacuum truck extraction, a previous repair consisting of a 5’ segment of corrugated plastic pipe had been dislodged and expelled from the downstream end of the spillway. With a compromised dam and flooding in the forecast, MLC acted immediately to handle this emergency dam repair.

Primary Spillway Inlet
Before – Upper portion of the existing corrugated metal pipe was collapsed. After – Pipe was slip-lined and the annulary space was grouted.

 

Given Princeton Hydro’s long-term history of inspecting and maintaining dams and levees in Medford Lakes, MLC contracted our experts to assist. The next day, our team of geotechnical engineers were on-site to investigate the situation. To facilitate the inspection and minimize the stress/pressure on the dam, the upstream and downstream lakes were lowered via an NJDEP Fish and Wildlife Lake Lowering Permit. Additionally, a video inspection of the compromised culvert pipe was conducted. Our geotechnical team observed that the upstream portion of the pipe had collapsed and the structure was experiencing significant seepage (i.e. water flowing through undesirable paths through the dam with the potential for soil piping and stability failure).

Primary Spillway outlet
Before – The existing corrugated metal pipe had corroded and erosion had taken place around the outlet. After – Pipe has been slip-lined and outlet protection (riprap) was installed to stabilize the surrounding soil.

 

With the risk of potential dam failure, Princeton Hydro immediately kicked-off coordination with the NJDEP Bureau of Dam Safety, NJDEP Division of Land Use Regulation, the Pinelands Commission, and the Borough of Medford Lakes. Our licensed engineers promptly developed the repair concept and associated scope of work, detailing our proposed means and methods for the emergency repair.

“We take the potential risk of dam failure very seriously, as safety is one of our core values,” said Kevin Yezdimer, P.E. Director of Geosciences Engineering at Princeton Hydro. “Our geotechnical team prioritized the design, permitting, and implementation of this emergency repair to assure the safety of our client and the community.”

Injection grouting underway (Grout pressure is monitored during placement & the ground surface is monitored for signs of heave).

This included addressing the collapsed pipe; utilizing cementitious injection grouting and compaction grouting to eliminate seepage pathways and stabilize the earthen dam in-place; and provide spillway outfall protection. Through private solicitation, Princeton Hydro selected Compaction Grouting Services, Inc. as the specialty contractor to perform the repair.

A considerable volume of water was required to prepare the grout mixes, and no water sources were available adjacent to the project site. Seeking out solutions, MLC proposed the unique idea of using reclaimed wastewater from the local wastewater treatment plant. Our team confirmed that reuse of the reclaimed wastewater was indeed within the guidelines of the “Technical  Manual for Reclaimed Water for Beneficial Reuse,” and we successfully facilitated approval to use it with NJDEP Division of Water Quality.

Placement of cellular fill into the hollow concrete structure is underway. A lightweight foaming agent was added to the grout mix within the concrete truck. The lightweight grout was then pumped into the structure.

As the construction effort ramped-up, some complications arose. By design, this unique structure allows water flow over the dam’s weirs and drops 8 to 10 feet vertically before travelling under the roadway through the primary spillway. Above the primary spillway is a concrete structure that spans from the upstream lake to the downstream lake and immediately beneath the local roadway. It was discovered that this 50’ long, 6’ deep, concrete structure was hollow and served as a potential seepage pathway. Princeton Hydro proposed to fill-in the hollow structure with a lightweight cellular fill material in order to cut-off the potential seepage pathways, eliminate the 6’ deep hollow chamber beneath the roadway, and facilitate a long-term repair solution.

Implementation of this strategy was further complicated when a utility markout and a subsequent video inspection of the hollow structure confirmed that a gas line passed through the structure on the downstream side of the roadway. Princeton Hydro coordinated with South Jersey Gas to disconnect the gas line in order to minimize risk during construction and eliminate future complications. The neighborhoods on either side of the dam were fed redundantly, so their service was not interrupted during this process.

Overall, the emergency dam repair solution involved an in-situ soil stabilization of an earthen embankment dam via compaction/injection grouting, slip-lining the primary spillway, stabilization of the downstream outlet, and utilization of reclaimed wastewater as a water source for on-site grout batching. The following was completed by our team and contractors during the course of the emergency construction:

  • Slip-lining of the failed 30-inch pipe using a smooth, slightly smaller in diameter high density polyethylene pipe (HDPE) pipe inside of the existing pipe, providing an equal or greater hydraulic capacity as that existing;

  • Grouting of the annular space between the new and old pipes;

  • Non-woven geotextile fabric and riprap outfall protection were placed around the downstream outlet of the culvert pipe to provide scour protection;

  • Compaction and injection grouting was performed in multiple locations. The compaction grout utilized a “low-slump” mix while the injection grout utilized a much more mobile or fluid mix allowing for filling of existing seepage pathways or soil voids, and;

  • Approximately 44 cubic yards of lightweight cellular-grout backfill was utilized to fill in the hollow concrete structure beneath the roadway completing the emergency repair without the need for complete outlet structure or earthen dam reconstruction.

Lowering New Pipe Into Place

Creative, innovative solutions paired with timely coordination and expertise drove the success of the Lake Wauwauskashe Dam emergency repair.

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

Kevin M. Yezdimer, P.E., Princeton Hydro’s Geoscience Engineering Director, is a multidisciplinary professional civil engineer who holds degrees in both Geology and Civil Engineering, and has 11 years of progressive and varied work experience as both a design consultant and project owner with Geotechnical & Construction Engineering being his core area of expertise. He has significant experience performing soil and rock core sampling programs, infiltration testing, soils laboratory testing, foundation design (shallow and deep), preparation of construction recommendations,  and overseeing construction review activities (e.g., earthwork, foundations, concrete, masonry, structural steel, roadway, and utility construction).

 

Jim Hunt, P.E., joined Princeton Hydro in 2017 as a Geotechnical Engineer and provides a wide range of engineering services for the firm including: subsurface explorations, bearing capacity and settlement analyses, slope stability analysis, stability analysis of existing structures, preparation of technical deliverables, and cost estimating.