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The lake, a small impoundment of Peekskill Hollow Creek, serves as a vital recreational resource for the community. Princeton Hydro’s initial study was structured around three core tasks: (1) analysis of long-term water quality data, (2) development of an updated pollutant budget, and (3) formulation of short- and long-term management strategies. The analysis revealed a steady increase in conductivity and total phosphorus (TP) concentrations over the past two decades, indicating rising nutrient loads and a shift toward eutrophic conditions. Elevated TP levels were directly linked to increased algal biomass, particularly harmful cyanobacteria producing microcystin-LR, which exceeded safe swimming thresholds in 2014. The updated pollutant budget identified septic system leachate (55%) and stormwater runoff (22%) as the primary sources of phosphorus entering the lake. Internal loading from sediments and atmospheric deposition also contributed to the nutrient burden. To address these issues, Princeton Hydro proposed a suite of in-lake management interventions focused on the lake’s three public beaches. Recommendations included installing electric water pumps to improve circulation at Carrara’s Beach and ozone/aeration systems at Singer’s and North Beaches to reduce organic buildup and mitigate algal blooms. These nature-based, non-chemical solutions were designed to provide immediate relief while longer-term watershed improvements, such as septic upgrades and stormwater controls, are pursued. The plan emphasized the need for community engagement, regulatory coordination, and sustainable implementation to restore and protect Lake Peekskill’s ecological health and recreational value. Building on this foundational work, Princeton Hydro was re-engaged in 2022 by the Lake Peekskill Civic Association (LPCA) and the Town of Putnam Valley to provide additional lake management services. The team developed a comprehensive Lake Management Plan aimed at identifying and prioritizing cost-effective green infrastructure and stormwater Best Management Practices (BMPs) for implementation by the Town. The goal was to reduce nutrient loading, improve water quality, mitigate nuisance aquatic vegetation, prevent harmful algal blooms (HABs), and enhance overall stormwater management within the watershed. This phase of work included a detailed analysis of historical water quality data, a submerged aquatic macrophyte survey, and a field-based water quality assessment. Princeton Hydro also conducted a pollutant removal analysis to evaluate the effectiveness of specific watershed-based management techniques. The resulting plan provided a clear roadmap for reducing annual pollutant loads and minimizing the occurrence and severity of HABs through targeted, science-based interventions. The recommendations were designed to be actionable, scalable, and aligned with the Town’s capacity and resources, reinforcing the long-term commitment to restoring and maintaining the health of Lake Peekskill. [post_title] => Lake Peekskill Watershed Management Planning [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => lake-peekskill-watershed-management-planning [to_ping] => [pinged] => [post_modified] => 2026-03-06 13:38:57 [post_modified_gmt] => 2026-03-06 13:38:57 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=19291 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [1] => WP_Post Object ( [ID] => 19281 [post_author] => 1 [post_date] => 2026-03-05 19:57:58 [post_date_gmt] => 2026-03-05 19:57:58 [post_content] => The U.S. Army Corps of Engineers, New York District (USACE), in partnership with the New Jersey Department of Environmental Protection (NJDEP), conducted a comprehensive study to identify ecosystem restoration and flood-damage-reduction solutions for the Millstone River Basin in New Jersey. Project stakeholders included the U.S. Geological Survey, the USDA Natural Resources Conservation Service, Mercer and Middlesex Counties, Princeton University, and the Stony Brook–Millstone Watershed Association. During the study, Carnegie Lake, a freshwater impoundment of the Millstone River located in Mercer and Middlesex Counties, was identified as a significant natural resource within the watershed. As the project’s lead agency, USACE contracted Princeton Hydro to develop a detailed lake and watershed restoration plan for Carnegie Lake. The Carnegie Lake and Watershed Restoration Plan focused on three primary objectives. First, it involved collecting a wide range of site‑specific in‑lake and watershed data. Second, it quantified the hydrologic and non‑point‑source pollutant budgets for the lake, including total suspended solids and the nutrients nitrogen and phosphorus. Third, it used the findings from the first two objectives to develop a comprehensive lake and watershed restoration plan. The first objective was completed in 2003, during which extensive data were collected throughout the growing season. A major component of this effort was a detailed bathymetric survey that measured water depths and the volume of unconsolidated sediments. Additional tasks included collecting physical, chemical, and biological in‑lake data; conducting macrophyte and fisheries surveys; and collecting and analyzing baseline and stormwater samples. Hydrologic and pollutant budgets for Carnegie Lake and its watershed were then developed using standardized and widely accepted models calibrated with the collected baseline and stormwater data. These budgets informed water‑quality models used to predict in‑lake conditions under various climatic and pollutant‑loading scenarios. All water‑quality and watershed data, along with model results, were used to evaluate and prioritize feasible, cost‑effective in‑lake and watershed management techniques aimed at improving water quality and reducing pollutant loads. The project was finalized in March 2005. [gallery link="none" ids="19279,19277,19276"] [post_title] => Carnegie Lake Phase I Lake and Watershed Restoration Plan [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => carnegie-lake-phase-i-lake-and-watershed-restoration-plan [to_ping] => [pinged] => [post_modified] => 2026-03-05 20:21:18 [post_modified_gmt] => 2026-03-05 20:21:18 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=19281 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [2] => WP_Post Object ( [ID] => 19061 [post_author] => 1 [post_date] => 2026-01-12 21:50:23 [post_date_gmt] => 2026-01-12 21:50:23 [post_content] => From 2001 through 2002 Princeton Hydro collected the necessary field data such as in-situ, bathymetric, and discrete (both water and sediment), and also delineated and modeled the hydrologic and nutrient loads of the watershed for four (4) New Jersey state park lakes: Round Valley swimming area, Lake Absegami, Host Lake, and Hook Creek Lake. This data was then compiled and computed to prepare a Management Plan for each of the individual lakes. [gallery link="none" size="medium" ids="19062,19063,19064"] The plans provided specific objectives and recommendations for the short and long-term management of each Lake and its watershed. Both in-lake and watershed management techniques were provided in the plan. In-lake techniques tended to focus on symptomatic problems such as algal blooms and the accumulation of sediments, while watershed techniques tended to focus on reducing pollutant loads through the use of structural and non-structural Best Management Practices (BMPs) and Green Infrastructure (GI) techniques. The management techniques were priority ranked, with these rankings being dependent upon applicability, regulatory constraints, technical feasibility, degree of effectiveness, initial implementation costs, and operations and maintenance costs. In-lake restoration techniques were designed to improve the water quality and/or aesthetics of the waterbody by alleviating the specific impacts of pollution. Although these measures typically provide only short-term relief without controlling the source of the pollutants, they can substantially improve the aesthetics of a lake while the long-term, watershed-based management practices are being implemented. In contrast to in-lake restoration techniques, watershed-based techniques focused on the causes of eutrophication rather than the effects. Watershed techniques were not as visible as in-lake techniques and tended to take more time to produce their desired results. However, they were absolutely vital in reducing the pollutant load, as well as producing and sustaining long-term improvements in surface water quality for each of the lakes. [post_title] => New Jersey State Park - Diagnostic Feasibility Lake Studies [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => new-jersey-state-park-diagnostic-feasibility-lake-studies [to_ping] => [pinged] => [post_modified] => 2026-01-12 21:52:34 [post_modified_gmt] => 2026-01-12 21:52:34 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=19061 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [3] => WP_Post Object ( [ID] => 17715 [post_author] => 1 [post_date] => 2025-07-01 14:59:08 [post_date_gmt] => 2025-07-01 14:59:08 [post_content] => The Cooper River Watershed is a 39.5 square mile tributary to the Delaware River within the Delaware River Basin. It is characterized by extensive residential and commercial development and a number of highly degraded waterbodies. Near the mouth of the Cooper River, a tidal dam forms Cooper River Lake (CRL). This 192-acre public lake has a Total Maximum Daily Load (TMDL) for total phosphorus (TP) and a variety of other nonpoint source pollutants. Immediately upstream of CRL are Wallworth Lake and Evans Pond which suffer the same impairments as CRL. CRL is the centerpiece of Camden County’s 347-acre Cooper River Park; Evans Pond and Wallworth Lake are within Camden County’s Wallworth Park (56 acres). These waterbodies are part of Camden County’s greenway and provide recreational opportunities to the overburdened communities (OBCs) that surround them. These waterbodies also provide significant water quality services to the watershed, such as regional stormwater attenuation and sediment trapping. Unfortunately, the highly degraded condition of this watershed is well documented. Further, in 2020 a harmful algal bloom (HAB) was confirmed by NJDEP within Hopkins Pond, a waterbody upstream of CRL, with toxin levels posing a high risk of adverse health effects. Camden County Soil Conservation District (CCSCD) was awarded funding through NJDEP’s Lake Restoration Grant program to develop a USEPA 9-Element Plus 1 Watershed Implementation Plan (9E+1 WIP) for the CRL watershed, including Evans Pond, Wallworth Lake, and Hopkins Pond. The goal of the WIP is to develop a strategy to cost effectively identify and address the potential watershed impacts through in-lake and watershed-based management activities, with designs to address impacts driven by climate change. Through stakeholder engagement and the review of historical data, the project team is determining sources of pollutant loading in the watershed. The team will utilize the results, and the data collected during the water quality monitoring and watershed assessment to characterize and prioritize areas that and locations that would be optimal for best management practices and green infrastructure. Ultimately, the project team will develop a comprehensive Cooper River Lake Watershed Implementation Plan. Princeton Hydro is in the process of completing a 1-year detailed sampling and surveying exercise of the CRL watershed for the purpose of collecting the data needed to assess the lake and streams within and design the lake/stream protection and watershed management plan. In addition to the above mentioned tasks, Princeton Hydro also conducted bathymetric assessments of CRL, Evans Pond, and Wallworth Lake. [post_title] => Watershed Implementation Plan for Cooper River Lake [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => watershed-implementation-plan-for-cooper-river-lake [to_ping] => [pinged] => [post_modified] => 2025-07-01 14:59:08 [post_modified_gmt] => 2025-07-01 14:59:08 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=17715 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [4] => WP_Post Object ( [ID] => 17621 [post_author] => 1 [post_date] => 2025-06-03 11:31:15 [post_date_gmt] => 2025-06-03 11:31:15 [post_content] => Over 40 years ago, Mercer County purchased 279 acres of flood-prone land along Miry Run as part of a restoration and flood mitigation initiative. In 2018, Mercer County Park Commission (MCPC) contracted Princeton Hydro and Simone Collins Landscape Architecture to develop the Miry Run Ponds Master Plan with three primary goals: (1) Provide passive recreation to complement other County activities; (2) Preserve and enhance the habitat, water quality, and natural systems that currently exist onsite; and (3) Provide linkage to adjacent trails and parks. [caption id="attachment_7488" align="alignnone" width="1024"] Miry Run Ponds Master Plan won the 2021 Landscape Architectural Chapter Award from the American Society of Landscape Architects New Jersey Chapter.[/caption] The team assessed the land area and proposed a concept plan to enhance the area and create recreational lake activities. Applying expertise in science-based assessment and evaluations, we performed:
In response to recurring water quality issues, including a significant cyanobacterial bloom in 2014 that led to prolonged beach closures, the Town of Putnam Valley engaged Princeton Hydro to revise and update the Lake Peekskill Watershed Management Plan. The lake, a small impoundment of Peekskill Hollow Creek, serves as a vital recreational resource for the community. Princeton Hydro’s initial study was structured around three core tasks: (1) analysis of long-term water quality data, (2) development of an updated pollutant budget, and (3) formulation of short- and long-term management strategies.
The analysis revealed a steady increase in conductivity and total phosphorus (TP) concentrations over the past two decades, indicating rising nutrient loads and a shift toward eutrophic conditions. Elevated TP levels were directly linked to increased algal biomass, particularly harmful cyanobacteria producing microcystin-LR, which exceeded safe swimming thresholds in 2014. The updated pollutant budget identified septic system leachate (55%) and stormwater runoff (22%) as the primary sources of phosphorus entering the lake. Internal loading from sediments and atmospheric deposition also contributed to the nutrient burden.
To address these issues, Princeton Hydro proposed a suite of in-lake management interventions focused on the lake’s three public beaches. Recommendations included installing electric water pumps to improve circulation at Carrara’s Beach and ozone/aeration systems at Singer’s and North Beaches to reduce organic buildup and mitigate algal blooms. These nature-based, non-chemical solutions were designed to provide immediate relief while longer-term watershed improvements, such as septic upgrades and stormwater controls, are pursued. The plan emphasized the need for community engagement, regulatory coordination, and sustainable implementation to restore and protect Lake Peekskill’s ecological health and recreational value.
Building on this foundational work, Princeton Hydro was re-engaged in 2022 by the Lake Peekskill Civic Association (LPCA) and the Town of Putnam Valley to provide additional lake management services. The team developed a comprehensive Lake Management Plan aimed at identifying and prioritizing cost-effective green infrastructure and stormwater Best Management Practices (BMPs) for implementation by the Town. The goal was to reduce nutrient loading, improve water quality, mitigate nuisance aquatic vegetation, prevent harmful algal blooms (HABs), and enhance overall stormwater management within the watershed.
This phase of work included a detailed analysis of historical water quality data, a submerged aquatic macrophyte survey, and a field-based water quality assessment. Princeton Hydro also conducted a pollutant removal analysis to evaluate the effectiveness of specific watershed-based management techniques. The resulting plan provided a clear roadmap for reducing annual pollutant loads and minimizing the occurrence and severity of HABs through targeted, science-based interventions. The recommendations were designed to be actionable, scalable, and aligned with the Town’s capacity and resources, reinforcing the long-term commitment to restoring and maintaining the health of Lake Peekskill.
The U.S. Army Corps of Engineers, New York District (USACE), in partnership with the New Jersey Department of Environmental Protection (NJDEP), conducted a comprehensive study to identify ecosystem restoration and flood-damage-reduction solutions for the Millstone River Basin in New Jersey. Project stakeholders included the U.S. Geological Survey, the USDA Natural Resources Conservation Service, Mercer and Middlesex Counties, Princeton University, and the Stony Brook–Millstone Watershed Association.
During the study, Carnegie Lake, a freshwater impoundment of the Millstone River located in Mercer and Middlesex Counties, was identified as a significant natural resource within the watershed. As the project’s lead agency, USACE contracted Princeton Hydro to develop a detailed lake and watershed restoration plan for Carnegie Lake.
The Carnegie Lake and Watershed Restoration Plan focused on three primary objectives. First, it involved collecting a wide range of site‑specific in‑lake and watershed data. Second, it quantified the hydrologic and non‑point‑source pollutant budgets for the lake, including total suspended solids and the nutrients nitrogen and phosphorus. Third, it used the findings from the first two objectives to develop a comprehensive lake and watershed restoration plan.
The first objective was completed in 2003, during which extensive data were collected throughout the growing season. A major component of this effort was a detailed bathymetric survey that measured water depths and the volume of unconsolidated sediments. Additional tasks included collecting physical, chemical, and biological in‑lake data; conducting macrophyte and fisheries surveys; and collecting and analyzing baseline and stormwater samples.
Hydrologic and pollutant budgets for Carnegie Lake and its watershed were then developed using standardized and widely accepted models calibrated with the collected baseline and stormwater data. These budgets informed water‑quality models used to predict in‑lake conditions under various climatic and pollutant‑loading scenarios. All water‑quality and watershed data, along with model results, were used to evaluate and prioritize feasible, cost‑effective in‑lake and watershed management techniques aimed at improving water quality and reducing pollutant loads.
The project was finalized in March 2005.
From 2001 through 2002 Princeton Hydro collected the necessary field data such as in-situ, bathymetric, and discrete (both water and sediment), and also delineated and modeled the hydrologic and nutrient loads of the watershed for four (4) New Jersey state park lakes: Round Valley swimming area, Lake Absegami, Host Lake, and Hook Creek Lake. This data was then compiled and computed to prepare a Management Plan for each of the individual lakes.
The plans provided specific objectives and recommendations for the short and long-term management of each Lake and its watershed. Both in-lake and watershed management techniques were provided in the plan. In-lake techniques tended to focus on symptomatic problems such as algal blooms and the accumulation of sediments, while watershed techniques tended to focus on reducing pollutant loads through the use of structural and non-structural Best Management Practices (BMPs) and Green Infrastructure (GI) techniques. The management techniques were priority ranked, with these rankings being dependent upon applicability, regulatory constraints, technical feasibility, degree of effectiveness, initial implementation costs, and operations and maintenance costs.
In-lake restoration techniques were designed to improve the water quality and/or aesthetics of the waterbody by alleviating the specific impacts of pollution. Although these measures typically provide only short-term relief without controlling the source of the pollutants, they can substantially improve the aesthetics of a lake while the long-term, watershed-based management practices are being implemented.
In contrast to in-lake restoration techniques, watershed-based techniques focused on the causes of eutrophication rather than the effects. Watershed techniques were not as visible as in-lake techniques and tended to take more time to produce their desired results. However, they were absolutely vital in reducing the pollutant load, as well as producing and sustaining long-term improvements in surface water quality for each of the lakes.
The Cooper River Watershed is a 39.5 square mile tributary to the Delaware River within the Delaware River Basin. It is characterized by extensive residential and commercial development and a number of highly degraded waterbodies. Near the mouth of the Cooper River, a tidal dam forms Cooper River Lake (CRL). This 192-acre public lake has a Total Maximum Daily Load (TMDL) for total phosphorus (TP) and a variety of other nonpoint source pollutants. Immediately upstream of CRL are Wallworth Lake and Evans Pond which suffer the same impairments as CRL.
CRL is the centerpiece of Camden County’s 347-acre Cooper River Park; Evans Pond and Wallworth Lake are within Camden County’s Wallworth Park (56 acres). These waterbodies are part of Camden County’s greenway and provide recreational opportunities to the overburdened communities (OBCs) that surround them. These waterbodies also provide significant water quality services to the watershed, such as regional stormwater attenuation and sediment trapping. Unfortunately, the highly degraded condition of this watershed is well documented. Further, in 2020 a harmful algal bloom (HAB) was confirmed by NJDEP within Hopkins Pond, a waterbody upstream of CRL, with toxin levels posing a high risk of adverse health effects.
Camden County Soil Conservation District (CCSCD) was awarded funding through NJDEP’s Lake Restoration Grant program to develop a USEPA 9-Element Plus 1 Watershed Implementation Plan (9E+1 WIP) for the CRL watershed, including Evans Pond, Wallworth Lake, and Hopkins Pond. The goal of the WIP is to develop a strategy to cost effectively identify and address the potential watershed impacts through in-lake and watershed-based management activities, with designs to address impacts driven by climate change.
Through stakeholder engagement and the review of historical data, the project team is determining sources of pollutant loading in the watershed. The team will utilize the results, and the data collected during the water quality monitoring and watershed assessment to characterize and prioritize areas that and locations that would be optimal for best management practices and green infrastructure. Ultimately, the project team will develop a comprehensive Cooper River Lake Watershed Implementation Plan. Princeton Hydro is in the process of completing a 1-year detailed sampling and surveying exercise of the CRL watershed for the purpose of collecting the data needed to assess the lake and streams within and design the lake/stream protection and watershed management plan. In addition to the above mentioned tasks, Princeton Hydro also conducted bathymetric assessments of CRL, Evans Pond, and Wallworth Lake.
Over 40 years ago, Mercer County purchased 279 acres of flood-prone land along Miry Run as part of a restoration and flood mitigation initiative. In 2018, Mercer County Park Commission (MCPC) contracted Princeton Hydro and Simone Collins Landscape Architecture to develop the Miry Run Ponds Master Plan with three primary goals: (1) Provide passive recreation to complement other County activities; (2) Preserve and enhance the habitat, water quality, and natural systems that currently exist onsite; and (3) Provide linkage to adjacent trails and parks.
The team assessed the land area and proposed a concept plan to enhance the area and create recreational lake activities. Applying expertise in science-based assessment and evaluations, we performed:
Our project team facilitated focus groups with local municipalities, residents, interest groups, and County stakeholders to seek their input and report on site evaluation findings. In partnership with the County, we held public meetings to gather feedback on the conceptual site designs. This helped to inform the park planning process and determine how best to manage the site to meet the needs of the community and future generations.
The final Miry Run Pond Master Plan goes above and beyond the original vision, proposing considerable improvements to the area prioritizing valuable natural features, including 34 acres of reforestation, 64 acres of new meadows, 19 acres of vernal pools, and 7.9 miles of walking trails. It serves as a long-term vision and will be implemented over multiple phases. Dredging of the lake began in 2023.
Liberty State Park is located on the west bank of Upper New York Bay and is one of the most visited state parks in the nation with over 5.1 million visitors in 2018. Princeton Hydro was contracted to design a resilient coastal ecosystem within 235 acres of this highly urbanized setting that provides both ecological and social benefits. This includes the restoration of over 80 acres of tidal and non-tidal wetlands and creation of several thousands of feet of intertidal shoreline and shallow water habitat hydrologically connected to the Upper New York Bay.
Historically, the site contained intertidal mudflats and shallow water habitat, which were filled and developed as a railroad yard. Once constructed, this project will expand public access, improve water quality, restore native plant communities, and improve coastal resiliency for urban communities that are vulnerable to storm events. The site design includes a trail network for the park interior that will provide access to the newly established habitat zones and views of the Statue of Liberty and New York City skyline. This trail network will enhance pedestrian connectivity between the existing portion of Liberty State Park, Liberty Science Center, Jersey City, and local public transit hubs.
To inform the design development, our team conducted design charrettes with various stakeholders and a myriad of monitoring tasks focused on site characterization including a wetland delineation; bio-benchmarking surveys of the tidal marsh vegetation communities; topographic, bathymetric, and utility surveys; and geotechnical sampling such as SPT borings and test pits. Field data and observations were incorporated into various analyses to support the engineering design including a 2D Hydrologic and Hydraulic model and wave analysis, and a detailed Sea Level Rise Analysis to inform the design of various project elements to accommodate sea level rise projections through 2070. The tidal channel geometry, culvert width, and tidal marsh were designed to address increased flows and water surface elevations. Groundwater levels and flow direction were also characterized through the installation of monitoring wells and continuous measurements of the groundwater level using piezometers.
To support the design process, the team developed interim construction cost estimates for various design milestones and coordinated and advanced the local, state, and federal permit process and applications. As part of NJDEP’s public outreach campaign, our team participated in an open house interacting directly with members of the public. We produced a 4-minute video simulating the expected visitor experience using detailed engineering design renderings. When completed, this will be one of the largest ecosystem habitat restoration projects in New Jersey. Click below to watch the video now:
Tanglwood Lake, located in Pike County, PA, is an impoundment created by Tanglwood Lake Dam, which is owned and maintained by the Tanglwood Lakes Community Association, Inc. (TLCA). Classified as a High-Quality, Cold-Water Fishery (HQ-CWF) for water quality protection, it accepts flow from Lake Wallenpaupack via Kleinhans Creek. The drainage area to the lake is approximately 0.6 square miles (384 Acres). The lake itself is approximately 26.0 acres.
Princeton Hydro has been contracted to conduct lake management services for TLCA since 2016 and was contracted to perform consulting and engineering services for design, permitting, bidding, construction administration, and construction oversight for the partial sediment removal from Tanglwood Lake through hydraulic dredging and onsite disposal. Princeton Hydro conducted a bathymetric survey and performed sediment sampling to determine the volume and consistency of the sediment as well as the feasibility of onsite dewatering. Building on this previous work, wetland delineation and a site survey were conducted to collect data to inform the engineering design, regulatory compliance, contractor solicitation, and construction. Princeton Hydro’s regulatory experts prepared all applicable state and federal permits, including PADEP Dam Safety; Soil Erosion and Sediment Control Plan Certification; and NPDES Stormwater Permit for the sediment removal; dewatering; and disposal on the adjacent lot.
The engineering design for sediment removal and dewatering was completed, along with the engineering design for the disposal area of the dewatered dredged material. The dredging occurred over multiple events, with approximately 2,000 cubic yards of sediment and organics removed from the eastern portion of the lake. This sediment was dewatered using geotubes placed on a gravel bed. Once dewatered and all approvals were obtained, the sediment was relocated to the adjacent lot to create a gentle slope off the roadway and to make the site more park-like for the community.
Mercer County is currently conducting maintenance dredging for a portion of the impoundment (Miry Run) behind Dam 21. The focus of the dredging is to remove sediment in the vicinity of the water trail proposed as set forth in the January 2020 Master Plan for the Miry Run Ponds Park. Initially it was assumed, and was later confirmed, the material to be dredged was clean (i.e. below NJDEP residential reuse threshold) and that the dredged material would be placed on the adjacent farm fields and disked into the soil. The project was based on the Dredging Concept Plan that initially identified the areas proposed for dredging and thin layer application. If the dredged sediments from the project had been determined to be above NJDEP’s threshold for the intended use in the placement areas, it would have been dewatered onsite and disposed of at a regulated facility.
Based on an evaluation of the completed bathymetric survey, which was completed as part of the Master Plan, and the location of the water trail, Princeton Hydro identified three primary areas where the maintenance dredging will be focused.
Dredging Area 1 is in the main body of the lake just downstream of Line Road and would generate approximately 34,000 cubic yards of dredged material.
Dredging Area 2 is in the northeast cove, just north of Dredging Area 1. Dredging Area 2 has approximately 4,900 cubic yards of accumulated sediment.
Dredging Area 3, the northwestern cove, would require the removal of approximately 7,300 cubic yards of accumulated sediment. Total anticipated dredging volume is roughly 46,200 cubic yards.
The final project scope included (1) a sediment sampling plan, (2) sample collection and laboratory analysis, (3) engineering plan preparation, (4) preparation and submission of all NJDEP regulatory permitting materials, (5) preparation of the technical specification, (6) bid administration, and (7) construction administration and observation services.
Princeton Hydro was contracted by American Rivers to design, apply for permits, and provide construction administration services for the removal of the Kehm Run Dam, an earthen embankment, 270-feet long by 22 feet high, with a cast-in-place ogee spillway, about six (6) feet in height. The former impoundment was five (5) acres in size and contained an estimated 40,000 cubic yards of accumulated sediment. Princeton Hydro conducted a bathymetric survey, developed engineering plans, performed hydrologic and hydraulic analysis, applied to PADEP Dam Safety for a Restoration Waiver, and also to the York County Soil Conservation District plan approval. As part of the regulatory activities, Princeton Hydro subcontracted for a bog turtle (Glyptemys muhlenbergii) Phase I assessment, PA Historic and Museum Commission (PHMC) notices, and filed for a PA Fish and Boat Commission (PFBC) water lowering authorization. The dam was breached in 2019, and the project was completed the following year, with follow up site visits in 2021.
The project was challenging due to the quantity of sediment encountered and its fine-grained nature as a colloidal (very small clay particles), with a relatively small stream immediately downstream. As a result of PADEP Dam Safety inspecting the site, expressing their concerns about the quantity of sediment, Princeton Hydro prepared a revised breach design that provided containment of the sediment, while deregulating the dam. As a result, the former lakebed created an opportunity for its use to as a nature-based BMP to address nutrient loading to the Susquehanna River and Chesapeake Bay. The Susquehanna River Basin Commission saw this opportunity and funded a next phase to further enhance the wetlands created to improve sediment capture from the watershed.
This was a challenging project and has been documented by American Rivers in their blog as “Taking the Lemons and Making some Dam Lemonade”. As a project that provided significant lessons in adaptive management and making the most out of a challenging project.
Connecticut Fund for the Environment (FE) and Save the Sound (STS), in partnership with USFWS and CTDEEP Inland Fisheries Division, secured federal funding to remove the Hyde Pond Dam, restoring Whitford Brook, the primary in-flowing stream to the Mystic River estuary, to a natural free-flowing condition. This created unobstructed fish passage from Mystic River up through the project site, and removed a threat to public safety. The existing dam was an earthen embankment with a concrete capped masonry spillway 4.8 feet high that created a 12-acre impoundment. A fishway installed at the dam by CT DEEP to support a regionally-important river herring run and sea-run brook trout fishery was known to be ineffective due to its outlet location, beaver interference, and frequent low flows due to leakage through the dam. The dam removal restored fish passage to 4.1 miles of stream and provide access for alewife, blueback herring, American eel, American shad, and sea-run brook trout.
Princeton Hydro confirmed through impoundment probing and bathymetric survey that the impoundment contained significant quantities of impounded sediments that had become densely vegetated as scrub-shrub vegetation. Sediment management and wetland impacts became driving factors in the project design and regulatory process. Princeton Hydro coordinated with CT DEEP Planning and Standards Division to develop and approve a sediment sampling plan that included multiple samples throughout the site as well as downstream and upstream.
Results indicated some elevated contaminant levels in some areas. Princeton Hydro developed a sediment management plan and construction sequence, informed by the sediment analysis that balanced active sediment management and passive river restoration. The design entailed excavation of a portion of the sediment prone to mobilization that was then replaced, stabilized, and vegetated on-site.
Princeton Hydro coordinated closely with CFE/STS to negotiate with US Army Corps of Engineers and CT DEEP regulatory divisions to minimize impacts to wetland resources as much as practicable, protect downstream water quality, restore river and riparian functions to the site, and stay within grant cost limits. RiverLogic Solutions provided construction services, and Princeton Hydro provided construction supervision to remove the dam within budget and on schedule in 2015. Since removal, the site has undergone a gradual transition in vegetation but remains a vibrant stream-floodplain wetland complex.
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PRINCETON HYDRO
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