We’re committed to improving our ecosystems, quality of life, and communities for the better.
Our passion and commitment to the integration of innovative science and engineering drive us to exceed on behalf of every client.
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Princeton Hydro has partnered with Wildlands Conservancy for over a decade on multiple dam removals in the Lehigh River Valley. Our firm designed and permitted the removal of eight consecutive barriers on Jordan Creek, including three consecutive low-head dams. We also designed and permitted two low-head dams on Little Lehigh Creek. Collectively, these dam removal projects reconnected miles of river, enhanced aquatic habitat, and improved adjacent parkland and recreational fishing in the economically-stressed, urban communities of Allentown, PA.
Building upon the successes of the barrier removals on Jordan and Little Lehigh Creeks, Princeton Hydro partnered with the Wildlands Conservancy again in 2018 to remove a combination of four privately and publicly owned dams on Bushkill Creek in Easton, PA. The dam removal projects served as a model for landowners and municipalities regarding the need for future dam removals throughout the Delaware and Lehigh Valley Watersheds.
Having been restored to its natural, free-flowing state in Fall 2024, the barrier removals were part a larger, watershed-wide effort to improve aquatic connectivity, fisheries, and benthic macro-invertebrate and wildlife habitats. The projects restored fish passage, reduced nonpoint source pollution, improved water quality, and restored capacity for groundwater recharge, as well as stabilized and restored the stream’s channels and banks.
As part of the barrier removal projects, Princeton Hydro:
The Ousatonic Fish and Game Protective Association, Inc., in partnership with the Connecticut Department of Energy and Environmental Protection’s Inland Fisheries Division, sought to remove the Papermill Pond Dam on the East Aspetuck River to restore fish habitat formerly exceptional in quality for trout, facilitate fish passage through the site, and improve accessibility and functionality for people to engage in outdoor activities at the site in order to foster deeper stewardship ethic for the watershed.
The Papermill Pond Dam, located in New Milford, is an embankment dam situated on the East Aspetuck River. It is located 2.9 miles upstream of the confluence with the Housatonic River and is the first barrier on the East Aspetuck River. The spillway is concrete capped with masonry core. It has an approximate structural height of 11 feet and length of 75 feet.
The following alternatives were analyzed: 1) no action; 2) fishway bypass channel around dam; 3) technical fishway at dam; 4) dam lowering with fishway at dam; 5) river bypass and off-line pond; and, 6) full removal. Conceptual designs were developed for each alternative. Each alternative was analyzed and rated numerically relative to twelve categories: river morphology, aquatic resources (fisheries, macroinvertebrates, water quality), recreation, historic resources, flooding, relative liability, relative short-term costs, relative long-term costs, availability of funds, and anticipated permitability. Dam removal ranked as the most feasible alternative, but dam repair stood out as the best option for maintaining the existing ease of recreational access. That alternative necessitated dam repair, ongoing maintenance and inspection, both short-term and long-term sediment dredging, and construction of a fish bypass channel. The Association considered the alternatives and decided to pursue full dam removal.
Based on negotiations with CTDEEP that considered impacts to downstream habitats and other applicable regulations, the resulting recommendation was to remove a portion of the impounded sediment prior to passive release of the remaining impounded sediment, regardless of potential contamination. This minimized transitory sediment deposition in downstream habitats, thereby reducing the short-term impacts of the project. Thus, sediment proximal to the dam is proposed to be excavated and permanently deposited in upland areas onsite.
The dam was successfully removed in 2019 under supervision of CTDEEP Fisheries Division and Princeton Hydro.
Princeton Hydro was on the team to study the Bronx River Double Dam for New York City Parks (the dam owner). The project goal was to present an economically, environmentally, and socially sustainable long-term fish-passage solution for the Bronx River Double Dam.
The culmination of the project was a fish passage Alternatives Analysis for the dam site, where the cost and benefits of various long-term solutions for the project site were assessed, including dam removal and an engineered fishway. To inform the Alternatives Analysis, Princeton Hydro first studied the feasibility of the removal of the Bronx River Double Dam.
To inform the dam removal feasibility study and a conceptual dam removal design, Princeton Hydro supplemented data from a previous technical fishway design with data collected from additional field investigations. Princeton Hydro led the field collection effort, including sediment sampling, sediment probing, and a bathymetric survey to shed light on the impounded sediment concerns. Field investigations also included an investigation on the infrastructure, an updated topographic survey, and a seismic refraction survey to understand the potential for underlying bedrock to inform a conceptual design for dam removal.
Based on the data reviewed, Princeton Hydro concluded that dam removal is feasible and that its removal would 1) Restore the Bronx River to its historical flowpath, 2) Likely restore transparent fish passage at the site, and 3) Not impact infrastructure.
In comparing the dam removal alternative to the engineering fishway, the dam removal would provide a greater ecological benefit, while also reducing long term liabilities related to dam failure and costs associated with dam maintenance and inspection. Despite uncertainty associated with the dam removal alternative at this stage in the concept design, it is expected the upfront construction cost of the dam removal would be higher than the engineering fishway alternative.
The feasibility study and alternatives analysis set the stage for the US Army Corps of Engineers to further study fish passage at the Bronx River Double Dam.
Princeton Hydro was contracted to investigate, analyze, and design the removal of obstructions and restore natural stream function on Darby Creek. With funding from the National Fish and Wildlife Foundation and Pennsylvania Growing Greener program, the objective of the project was to remove remnant bridge piers in Colwyn and Sharon Hill Boroughs, a failed dam in Darby Borough, a mill dam in Landsdowne and Clifton Heights Boroughs, and a dam in Upper Darby Township and Clifton Heights Borough.
The Kent Park Dam was a placed rock structure that spanned Darby Creek within Kent Park within Delaware County. Princeton Hydro prepared hydrologic and hydraulic analyses; assessed fluvial geomorphic characteristics; determined infrastructure impacts; inventoried natural resources, including wetland delineations and invasive species; and assessed impounded sediment. Design plan sets were prepared, public presentations completed, and permit applications submitted to the Pennsylvania Department of Environmental Protection, U.S. Army Corps of Engineers, and the Delaware County Soil Conservation District.
This project included the reconstruction of the stream bank using bioengineered soil lifts; the innovative construction of a riffle over a sanitary sewer line, which protruded above the stream bed; and the creation of a wetland complex within a small spring tributary to Darby Creek, which reduced sediment contributions to the stream.
Princeton Hydro provided construction observation and administration to ensure the implementation met the stakeholders’ expectations and design intent. This project was funded by the PADEP Growing Greener Grant program, the National Fish and Wildlife Foundation, and a NOAA settlement fund from the 2004 Athos I oil spill on the Delaware River.
As Phase I of this project, Princeton Hydro was contracted by the Farmington River Coordinating Committee (FRCC) to assess the river banks in the Wild & Scenic Section of the West Branch Farmington River that are adjacent to roadways, identify and prioritize failing or eroding banks, and develop conceptual designs and construction cost estimates for addressing the high priority sites. The points where “river meets road” were prioritized because normal river processes can threaten public road infrastructure.
This effort represented a proactive approach by the FRCC to identify potential problem sites and to find solutions that enhance, rather than degrade, the river while protecting public road infrastructure. Conventional attempts to protect road infrastructure are often undertaken without an understanding of river processes and thus result in degradation of natural resource functions and values.
In Phase I, Princeton Hydro identified approximately 500 linear feet of river bank along the West Branch Farmington River in the Town of Barkhamsted that was eroded. If unaddressed, the erosion could jeopardize an adjacent road.
In 2019, Princeton Hydro was subsequently contracted for Phase II of the project by the Town of Barkhamsted to complete an engineering design for the 500 linear foot bank stabilization. Because the stabilization occurred on a Wild & Scenic section of the West Branch Farmington River, the Farmington River Coordinating Committee, National Parks Service, and National Oceanic and Atmospheric Administration were involved as additional partners. This phase began with an initial site assessment completed in conjunction with the land survey. The survey was used to inform a hydrologic and hydraulic assessment, which in turn informed the design of the bank stabilization as well as ensuring the proposed design did not adversely impact flooding in the area. The final engineering design included stabilization of the undercut bank toe with a mechanically compacted naturalized mixture of boulders, cobbles, and gravels.
Princeton Hydro is currently contracted to assist the Town of Barkhamsted in obtaining permits required for construction. Once the permits are obtained, Princeton Hydro is expected to be involved in the bid support and construction oversight of the designed project.
The Marshfield 8 Dam is a historic run-of-the-river dam located on the Winooski River. The Vermont Agency of Natural Resources (VT ANR), acting on behalf of the private owner who was concerned with its deteriorating condition, contracted Princeton Hydro to complete sediment management planning, engineering design, and permitting for the removal of the dam.
Princeton Hydro conducted a detailed site investigation, sediment probing, and hydraulic modeling to develop a site-specific sediment management plan and engineering design. The plan utilized field data, and hydrologic and hydraulic modeling to address the geomorphic response of the existing impounded reach and consequences of downstream sediment transport. In addition, Princeton Hydro proposed long-term monitoring measures to assess geomorphic changes and to inform future dam removal designs led by the VT ANR.
During the planning process, Princeton Hydro coordinated with a historic preservation firm to research and document historic uses of the site. In developing the design, Princeton Hydro coordinated with the adjacent landowner to design bank stabilization measures that incorporated the landowner’s concerns, as well anticipated shear stresses and channel adjustment post-removal. Princeton Hydro also performed construction oversight during the implementation of this project.
The Lake Hudsonia Dam was constructed in the early 1900s as part of a scout campground and impounded the headwaters of Hibernia Brook. The lake and dam are owned by Rockaway Township. For years, the Township was trying to determine the best path forward regarding the dam: repair or removal. Around 2010, it was determined that the removal of the dam would create significant wetlands and, therefore, it qualified for NJDEP Wetlands Mitigation Council funding. The removal of Lake Hudsonia Dam was designed in concert with a restoration component, which optimizes environmental benefits to the Hibernia Brook system. Hibernia Brook is a freshwater, non-trout producing, C1 stream (FW2-NTC1). Lake Hudsonia is typically 6 feet deep and likely contributes to elevated water temperatures, due to direct insolation, that is a exported to downstream reaches.
Restoration of a man-made impoundment to a free-flowing stream bordered by riparian floodplain wetland community
Increased flood storage capacity of the Hibernia Brook corridor
Improved water quality of C1 stream through enhanced removal of in-stream pollutants by restored riparian floodplain wetland
Reduction in summer in-stream water temperatures
Re-creation of stream habitat in the former impoundment
Restoration of fish passage and movement of other aquatic organisms
Re-connection of formerly isolated populations and stream habitats upstream and downstream of the dam
As part of the restoration element of this project, the lake bed was reshaped to reestablish a geomorphically appropriate streamchannel, to re-naturalize grades, and to re-establish vegetation. Accumulated sediment was moved within the impoundment and placed along the eastern shoreline, which is nearly vertical along the existing edge of water, to re-naturalize grades and create a gradual transition from the proposed floodplain wetland to the existing surrounding grades. Impounded sediments were sampled and analyzed for NJDEP Soil Remediation Standards (Residential, Non-Residential, and Impact to Groundwater) and determined to be suitable to remain onsite.
The proposed design to remove Hudsonia Lake Dam is focused on the restoration of Hibernia Brook and its floodplain to a native riparian wetland plant community. This restoration project seeks to convert the artificial impoundment of Hibernia Brook into a freshwater wetland complex of emergent and scrub/shrub wetland. Permit applications were simultaneously submitted to the NJDEP LURP for GP 16 and GP 18. In 2021, the project was bid and awarded to a contractor and construction was completed in November 2021, with oversight by Princeton Hydro. The impoundment area will be planted as an emergent wetland community with scattered patches of shrubs in order to stabilize the site. Over time, the site is anticipated to develop into a forested plant community similar in composition to the forested wetlands surrounding the site.
In April 2015, Solebury Township breached the historic mill dam in Aquetong Spring Park to convert the former lake into a natural area with a free-flowing, cold water stream capable of supporting native Brook Trout. After the dam breach, areas of active down-cutting through sediment within the former impoundment were observed along the mainstem and a major tributary of Aquetong Creek.
This resulted in the creation of steep, eroding banks, which increased the sediment load to the sensitive aquatic habitat of Aquetong Creek. Additionally, Solebury Township wanted to control invasive species in Aquetong Spring Park and replant the project area with native species. The Township secured funding to construct riparian buffers, implement streambank stabilization measures, establish trout habitat structures within the mainstem and its tributary, control invasive species, and implement a woodland restoration plan.
Princeton Hydro designed the restoration of the main channel and tributary to reduce channel and bank erosion while supporting Brook Trout habitat. After gathering and reviewing the existing data for the site, Princeton Hydro conducted field investigations to inform and guide the final design including surveying cross sections and performing fluvial geomorphological assessments of the existing channel. Pebble counts were performed, cross sections were analyzed, and existing hydrological data was reviewed to inform the design. Simultaneously, an invasive species control and woodland restoration plan was developed for the park.
Data collected from the site was used to develop a geomorphically-appropriate, dynamically-stable design. The proposed channel design included excavation of impounded sediment to create stable channel dimensions, the addition of gravel, cobble, and boulder substrate where original/existing channel substrates were absent or insufficient, and the installation of large wood features to create aquatic habitat and enhance stability of channel bed and banks. The banks and riparian corridor were vegetated with native seed, shrubs and trees to ultimately create a wooded, shaded riparian buffer. The design ultimately stabilized the streambanks with features that double as trout habitat and replanted the surrounding park with native vegetation.
Princeton Hydro also provided stormwater design support for adjacent areas in Aquetong Spring Park including multiple stormwater connections to the main tributary. After completion, Princeton Hydro provided bid assistance, developed a probable cost, drafted technical specifications, and produced a bid package to assist the client in bringing the project to construction. Princeton Hydro continues to work with the Township to monitor the site.
Princeton Hydro partnered with the Housatonic Valley Association (HVA) in their long-term effort to support municipal flood hazard mitigation planning, improve flood resiliency of transportation infrastructure, and remove barriers to aquatic organism passage in northwestern Connecticut. HVA deployed teams of trained volunteers to inventory road-stream crossings at multiple sites following protocols developed by the North Atlantic Aquatic Connectivity Collaborative.
Princeton Hydro assisted the HVA and other project partners including Connecticut Department of Energy and Environmental Protection, University of Connecticut, and Tufts University in identifying the highest priority road-stream crossings to accomplish the multi-faceted goals.
Our role was to train HVA staff on survey and data collection of the road-stream crossings to support the re-design of the road culverts following the U.S. Forest Service Stream Simulation for Aquatic Organism Passage (AOP) at Road-Stream Crossings. This approach utilizes a detailed assessment of the stream geomorphic conditions, including dimensions, pattern, and profile. It also examines bedforms (pools, riffles, runs, steps), substrate grain size, large wood, and then recreates (or simulates) that channel design through the crossing. The approach has been used with great success throughout the National Forest system, with multiple AOP culverts withstanding large hurricanes while nearby conventional crossings fail.
Princeton Hydro successfully applied the design approach at road-stream crossings in Pennsylvania and Massachusetts. Then, our team developed preliminary designs for eight road-stream crossings, which have been incorporated into municipal flood hazard plans.
In 2019, Princeton Hydro was contracted by Riverkeeper, Inc. to progress two sequential dam removals, Barrier #1 and Maiden Lane Dam on the Furnace Brook, a tributary to the Lower Hudson River in the Town of Cortlandt of Westchester County, NY. Furnace Brook, like many of the tributaries to the Lower Hudson River, was industrialized with many mill dams in the late 1800s and early 1900s.
Barrier #1, a low-head, masonry dam, was the first barrier on Furnace Brook. Princeton Hydro conducted the site investigation, H&H Analysis, engineering plan set development, permit submission, and construction oversight. The dam removal was finalized in October 2020, which was the first permitted dam removal in New York State in decades.
Less than a mile upstream of Barrier #1 is the Maiden Lane Dam, a dam with a 20+ foot-high concrete spillway. From 2019 to 2021, Princeton Hydro developed a conceptual design under the contract with Riverkeeper, Inc. This work included collecting and analyzing sediment samples, conducting geomorphic assessment including sediment probes, completing an H&H analysis which focused on potential impacts to flooding, and developing a conceptual design plan set. At this stage, Princeton Hydro also coordinated with NYSDEC, Westchester County, and the Town of Cortlandt to ensure the feasibility of the dam removal.
In 2021, Princeton Hydro was contracted by Westchester County to finalize the engineering plan set, support the permit submission, and provide bid procurement support. This work will include finalizing a sediment management plan with NYSDEC and other permitting agencies. The project team estimates this phase will be completed in 2022, with removal of Maiden Lane Dam occurring in 2023.
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