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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. [post_title] => Papermill Pond Dam Removal and River Restoration Project [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => papermill-pond-dam-removal-and-river-restoration-project [to_ping] => [pinged] => [post_modified] => 2025-12-08 21:44:09 [post_modified_gmt] => 2025-12-08 21:44:09 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=18823 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [1] => WP_Post Object ( [ID] => 15402 [post_author] => 1 [post_date] => 2024-06-17 13:09:17 [post_date_gmt] => 2024-06-17 13:09:17 [post_content] => The Long Pond Dam currently serves as a barrier to migratory fish along Whitford Brook, a tributary to the Mystic River. Whitford Brook has seen significant declines in fish populations, in part due to dams along the river corridor that prevent fish from accessing upstream spawning habitat. Diadromous fish, including Alewife, Blueback Herring, American Shad, American Eel, and Sea Lamprey rely on access to upstream spawning habitat to complete their life cycle. For Long Pond specifically, CT DEEP Fisheries estimated that fish passage restoration could provide an annual run of more than 250,000 alewives. In conjunction with other recent improvements along Whitford Brook, facilitating fish passage at this location would create a 6.6-mile stretch of connected river corridor from the confluence of Whitford Brook with the Mystic River upstream to the top of Lantern Hill Pond. A nature-like fishway was identified as the targeted means of providing fish passage by Save the Sound as the configuration of the outlet structure and embankment were well suited to that approach (relative to a technical fishway) and because dam removal was not considered a viable option due to the recreational and habitat (spawning) value of the impoundment. Princeton Hydro’s scope included: evaluation of existing data including past H&H studies and engineering evaluations/inspections of the dam; site investigations including geomorphic assessment and wetland delineation; topographic, utility, and boundary surveys; development of a concept design; H&H analysis; geotechnical investigations; fish passage design; development of an engineering package (plans, technical specifications, construction cost estimate) and applications for regulatory approvals; and finalization of design documents based on regulatory feedback. The primary challenge presented by this project was that the dam in its existing configuration was not in compliance with CT DEEP dam safety standards and that improvements/modifications to the dam to bring it into compliance were being handled by others. Further, site constraints dictated that installation of a nature-like fishway would require replacement of the dam’s outlet structure, which would increase the scope and complexity of the project beyond that originally envisioned. While Princeton Hydro’s design of the nature-like fishway is largely complete, construction can not move forward until finalized plans for bringing the dam into compliance are completed by others and integrated with the proposed fish passage design. Princeton Hydro continues to coordinate with Save the Sound and other project partners to assure that future site improvements will work seamlessly with the proposed fish passage improvements. [post_title] => Designing a Nature-like Fishway at Long Pond Dam [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => design-of-nature-like-fishway-at-long-pond-dam [to_ping] => [pinged] => [post_modified] => 2024-07-24 09:54:10 [post_modified_gmt] => 2024-07-24 09:54:10 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=15402 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [2] => WP_Post Object ( [ID] => 14826 [post_author] => 1 [post_date] => 2024-04-18 14:55:52 [post_date_gmt] => 2024-04-18 14:55:52 [post_content] => 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. [gallery link="none" size="medium" ids="14819,14821,14820"] 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. [gallery link="none" ids="14824,14823,14825"] [post_title] => Hyde Pond Dam Removal [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => hyde-pond-dam-removal [to_ping] => [pinged] => [post_modified] => 2024-04-18 15:07:19 [post_modified_gmt] => 2024-04-18 15:07:19 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=14826 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [3] => WP_Post Object ( [ID] => 14093 [post_author] => 1 [post_date] => 2023-12-13 11:31:44 [post_date_gmt] => 2023-12-13 11:31:44 [post_content] => The Collins Company Lower Dam, constructed in 1910 as a hydroelectric dam, is located on the Farmington River, approximately 1 mile downstream (south) of the Collinsville Dam and State Route 179, in Avon, Connecticut, south of the Collinsville Town border and across the Farmington River from the Town of Burlington. In 2011, a pre-feasibility study was completed on the Collinsville Dam and the Collins Company Lower Dam to determine whether these defunct hydroelectric dams could be repowered. The study found that repowering only one of the dams was economically feasible. [caption id="attachment_13849" align="aligncenter" width="718"] Collins Company Lower Dam prior to removal. Photo by CT Insider.[/caption] In 2019, Canton Hydro, LLC began the retrofit of the Collinsville Dam for hydroelectric generation in conjunction with the construction of a fishway in order to allow passage of anadromous fish (i.e., American Shad, Alewife, Blueback Herring, and Sea Lamprey) to the upstream reaches of the Farmington River. Removal of the Collins Company Lower Dam will allow passage to the base of the newly retrofitted Collinsville Dam. The goals of this project are to eliminate a barrier to migratory fish; eliminate an obsolete dam; remove a public safety risk; re-create a free flowing, ecologically productive, and natural river channel; and create stable and safe public access. Also as noted above, this dam removal is imperative to enable fish passage at the fishway under construction at the Collinsville Dam, approximately one mile upstream. As part of the dam removal design process, Princeton Hydro developed a Sediment Management Plan, which involved assessing impounded sediment quality and quantity by conducting bathymetric mapping to sense elevation of top and bottom of unconsolidated sediment, and sampling and analyzing sediment for a broad range of contaminants. In addition to using the information gathered through the assessment, a professional survey and geomorphic concepts were used to determine the volume of impounded sediment and the anticipated river profile following dam removal. Princeton Hydro completed the bathymetric surveys, hydrologic and hydraulic analysis, geotechnical engineering, construction phasing determination, demolition and blasting plans, preparation of 30%, 60%, 90% and 100% designs, and regulatory review applications. Princeton Hydro is currently working through the engineering designs and permit applications. [post_title] => Collins Company Lower Dam Removal [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => collins-company-lower-dam-removal [to_ping] => [pinged] => [post_modified] => 2023-12-13 11:31:44 [post_modified_gmt] => 2023-12-13 11:31:44 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=14093 [menu_order] => 0 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [4] => WP_Post Object ( [ID] => 12767 [post_author] => 1 [post_date] => 2023-05-25 19:17:49 [post_date_gmt] => 2023-05-25 19:17:49 [post_content] => 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. [post_title] => Barkhamsted River Stabilization for Farmington River [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => barkhamsted-river-stabilization-for-farmington-river [to_ping] => [pinged] => [post_modified] => 2024-01-18 02:21:17 [post_modified_gmt] => 2024-01-18 02:21:17 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=12767 [menu_order] => 9 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [5] => WP_Post Object ( [ID] => 11476 [post_author] => 1 [post_date] => 2022-09-13 14:57:52 [post_date_gmt] => 2022-09-13 14:57:52 [post_content] => 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. [post_title] => Housatonic Valley Watershed Concept Planning & Geomorphic Design [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => housatonic-valley-watershed-concept-planning-geomorphic-design [to_ping] => [pinged] => [post_modified] => 2022-09-13 14:58:29 [post_modified_gmt] => 2022-09-13 14:58:29 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=11476 [menu_order] => 45 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [6] => WP_Post Object ( [ID] => 10427 [post_author] => 1 [post_date] => 2022-03-08 15:04:48 [post_date_gmt] => 2022-03-08 15:04:48 [post_content] => Princeton Hydro initiated engineering assessment and completed final design for the Farmington River Watershed Association and its project partners for this exciting, fast-paced fish passage improvement project, which included both the removal of the Spoonville Dam and the design of a nature-like fishway at the Winchell-Smith Dam. The Farmington River is a renowned Wild & Scenic River in Connecticut and this project looked to improve fish passage for historic runs of diadromous fish at both sites. The Spoonville Dam, a 35-foot-high concrete dam that was partially breached during the historic 1955 floods, is the first partial barrier to fish passage on the Farmington River. The dam is located in the Tariffville Gorge, just downstream from an outstanding whitewater rapids heavily utilized by whitewater enthusiasts. A transparent design process and open lines of communication with whitewater boaters were critical parts of the development of the final design, in order to ensure project buy in from the key project stakeholders. The second barrier on the Farmington is the Winchell-Smith Dam. The Winchell-Smith Dam is a low head timber crib dam that had already lost the upper two to four feet of the dam in previous high flow events. The dam currently provides a well-known scenic overlook from the dam’s mill that has been converted into a popular local restaurant. Site aesthetics were a critical design component and the design approaches needed to be approved of by the dam and restaurant owners. Princeton Hydro was initially tasked with designing a bypass channel around the dam but found during our geotechnical field investigation that the overbank area was dominated by collapsible soils which could potentially cause an unintended channel avulsion and dam circumvention if the bypass channel was constructed. We then proposed a partial rock ramp fishway extending in an upstream direction from the dam in order to minimize cost while maximizing the site’s fish passage effectiveness based on the target fish species’ behavioral needs. [post_title] => Spoonville Dam Removal and Winchell-Smith Fishway [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => spoonville-dam-removal-and-winchell-smith-fishway [to_ping] => [pinged] => [post_modified] => 2024-07-11 14:30:56 [post_modified_gmt] => 2024-07-11 14:30:56 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=10427 [menu_order] => 63 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [7] => WP_Post Object ( [ID] => 9050 [post_author] => 1 [post_date] => 2021-07-12 17:42:41 [post_date_gmt] => 2021-07-12 17:42:41 [post_content] => Princeton Hydro was contracted by the Town of Greenwich, Connecticut to develop a coastal resilience plan in anticipation of changing conditions due to climate change. The Town possesses 27 miles of shoreline along the Long Island Sound, with 7 of 30 islands in its eight harbors being town-owned. Greenwich, like many coastal communities, already experiences coastal, pluvial, and fluvial flooding which disrupts traffic patterns, impacts infrastructure, and damages town and private assets. In order to protect these coastal areas, which provide a variety of environmental, economic, and community benefits, our team is working to develop a plan that makes sense and will not only protect but enhance Greenwich’s coastal areas. The work for this project is broken up into two phases, Phase 1 includes a suite of analyses to identify specific areas that are at risk, assess the extent of exposure to flooding, provide concepts for enhancing resiliency, and prioritize specific recommendations for upgrading the municipality’s assets. These assessments are interdisciplinary and aim to provide a holistic overview of the built, physical, and natural systems within Greenwich Connecticut. A key component of our assessment and Plan is to not only provide information needed for planning and decision-making, but to also provide information to the general public. To meet this objective, Princeton Hydro will arrange and facilitate two public information sessions. Here, the Princeton Hydro communications team and experts will present our findings along with a Q&A session, provide a primer on climate change and its effects on sea level, and allow for public feedback to maximize public participation. During Phase 2, our team plans to specifically analyze the effects of tidal migration on the town's four pond complexes. Our plan will provide specific recommendations on how to transition the ponds and shoreline areas to adapt to changing future conditions, with the ultimate goal of maintaining the town’s most important natural resource for public use. The Princeton Hydro team will employ field and modeling techniques to monitor water quality, assess pollutant loading & sediment dynamics, and conduct biological surveys. Like Phase 1, Phase 2 will also include a public information session to present our findings, discuss projected conditions of the ponds, and provide a number of management options to suit future conditions. [post_title] => Greenwich Coastal Resiliency Assessment & Plan [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => greenwich-coastal-resiliency-assessment-plan [to_ping] => [pinged] => [post_modified] => 2024-07-11 14:52:32 [post_modified_gmt] => 2024-07-11 14:52:32 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=9050 [menu_order] => 78 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [8] => WP_Post Object ( [ID] => 8025 [post_author] => 1 [post_date] => 2021-04-21 15:56:58 [post_date_gmt] => 2021-04-21 15:56:58 [post_content] => Princeton Hydro was contracted to provide engineering design, permitting, and construction oversight services for the removal of the Heminway Pond Dam located on Steele Brook in Connecticut. The project was part of a larger-scale Watershed Based Plan for Steele Brook Watershed and the restoration of fish passage along the Naugatuck River. The project included the field assessment and design of the Heminway Pond Dam removal and the associated channel restoration and stabilization. Additionally, our team led the preparation of a sediment sampling plan in coordination with the Connecticut Department of Energy and the Environment (CTDEEP), sediment sampling and analysis, and a CTDEEP-approved sediment management plan. The impounded sediments contained metals and PAHs, with an average sediment depth of four feet. One of the primary design goals was to retain and stabilize as much of the impounded sediment as possible on-site to reduce the dam removal construction costs. The project also included the preparation of hydrologic and hydraulic analyses/modeling; federal, state, and local environmental permit packages, including a Section 106 Historic Consultation, and several public information meetings. To ensure constructibility of final designs and reduce construction costs, the project design and cost estimate were completed in coordination with RiverLogic Solutions, a contractor specializing in dam removal that frequently works in conjunction with Princeton Hydro. Historic, archaeological, and social issues were a major concern at this site, so a detailed historic consultation and public outreach plan was integrated into the design process from the onset of the project. Critical funding for implementation was provided by CTDEEP, and removal was completed in 2018. Princeton Hydro worked closely with the City of Watertown and the selected contractor to oversee and guide construction, which entailed removal of the concrete spillway, excavation and relocation of hundreds of yards of impounded sediment, and reconstruction of over 1,000 feet of river channel. The U.S. Environmental Protection Agency featured the Heminway Pond Dam Removal and Steele Brook Restoration project as a "Nonpoint Source Success Story." Click here to read it now. Be sure to click on the link within the “Success Story” to view the dam removal video that was created as part of the project: [embed]https://youtu.be/O-X4W2YS3l0?si=L3CHybEYJcMl_Kay[/embed] [post_title] => Heminway Pond Dam Removal [post_excerpt] => [post_status] => publish [comment_status] => closed [ping_status] => closed [post_password] => [post_name] => heminway-pond-dam-removal [to_ping] => [pinged] => [post_modified] => 2025-11-07 19:43:28 [post_modified_gmt] => 2025-11-07 19:43:28 [post_content_filtered] => [post_parent] => 0 [guid] => https://princetonhydro.com/?post_type=project&p=8025 [menu_order] => 91 [post_type] => project [post_mime_type] => [comment_count] => 0 [filter] => raw ) [9] => WP_Post Object ( [ID] => 7901 [post_author] => 1 [post_date] => 2021-04-20 20:58:04 [post_date_gmt] => 2021-04-20 20:58:04 [post_content] => Princeton Hydro was contracted by the U.S. Army Corps of Engineers to perform rigorous Periodic Levee Inspections for the following six levee systems in the Northeast:
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.
The Long Pond Dam currently serves as a barrier to migratory fish along Whitford Brook, a tributary to the Mystic River. Whitford Brook has seen significant declines in fish populations, in part due to dams along the river corridor that prevent fish from accessing upstream spawning habitat. Diadromous fish, including Alewife, Blueback Herring, American Shad, American Eel, and Sea Lamprey rely on access to upstream spawning habitat to complete their life cycle. For Long Pond specifically, CT DEEP Fisheries estimated that fish passage restoration could provide an annual run of more than 250,000 alewives. In conjunction with other recent improvements along Whitford Brook, facilitating fish passage at this location would create a 6.6-mile stretch of connected river corridor from the confluence of Whitford Brook with the Mystic River upstream to the top of Lantern Hill Pond.
A nature-like fishway was identified as the targeted means of providing fish passage by Save the Sound as the configuration of the outlet structure and embankment were well suited to that approach (relative to a technical fishway) and because dam removal was not considered a viable option due to the recreational and habitat (spawning) value of the impoundment.
Princeton Hydro’s scope included: evaluation of existing data including past H&H studies and engineering evaluations/inspections of the dam; site investigations including geomorphic assessment and wetland delineation; topographic, utility, and boundary surveys; development of a concept design; H&H analysis; geotechnical investigations; fish passage design; development of an engineering package (plans, technical specifications, construction cost estimate) and applications for regulatory approvals; and finalization of design documents based on regulatory feedback.
The primary challenge presented by this project was that the dam in its existing configuration was not in compliance with CT DEEP dam safety standards and that improvements/modifications to the dam to bring it into compliance were being handled by others. Further, site constraints dictated that installation of a nature-like fishway would require replacement of the dam’s outlet structure, which would increase the scope and complexity of the project beyond that originally envisioned.
While Princeton Hydro’s design of the nature-like fishway is largely complete, construction can not move forward until finalized plans for bringing the dam into compliance are completed by others and integrated with the proposed fish passage design. Princeton Hydro continues to coordinate with Save the Sound and other project partners to assure that future site improvements will work seamlessly with the proposed fish passage improvements.
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.
The Collins Company Lower Dam, constructed in 1910 as a hydroelectric dam, is located on the Farmington River, approximately 1 mile downstream (south) of the Collinsville Dam and State Route 179, in Avon, Connecticut, south of the Collinsville Town border and across the Farmington River from the Town of Burlington. In 2011, a pre-feasibility study was completed on the Collinsville Dam and the Collins Company Lower Dam to determine whether these defunct hydroelectric dams could be repowered. The study found that repowering only one of the dams was economically feasible.
In 2019, Canton Hydro, LLC began the retrofit of the Collinsville Dam for hydroelectric generation in conjunction with the construction of a fishway in order to allow passage of anadromous fish (i.e., American Shad, Alewife, Blueback Herring, and Sea Lamprey) to the upstream reaches of the Farmington River. Removal of the Collins Company Lower Dam will allow passage to the base of the newly retrofitted Collinsville Dam.
The goals of this project are to eliminate a barrier to migratory fish; eliminate an obsolete dam; remove a public safety risk; re-create a free flowing, ecologically productive, and natural river channel; and create stable and safe public access. Also as noted above, this dam removal is imperative to enable fish passage at the fishway under construction at the Collinsville Dam, approximately one mile upstream.
As part of the dam removal design process, Princeton Hydro developed a Sediment Management Plan, which involved assessing impounded sediment quality and quantity by conducting bathymetric mapping to sense elevation of top and bottom of unconsolidated sediment, and sampling and analyzing sediment for a broad range of contaminants. In addition to using the information gathered through the assessment, a professional survey and geomorphic concepts were used to determine the volume of impounded sediment and the anticipated river profile following dam removal.
Princeton Hydro completed the bathymetric surveys, hydrologic and hydraulic analysis, geotechnical engineering, construction phasing determination, demolition and blasting plans, preparation of 30%, 60%, 90% and 100% designs, and regulatory review applications.
Princeton Hydro is currently working through the engineering designs and permit applications.
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.
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.
Princeton Hydro initiated engineering assessment and completed final design for the Farmington River Watershed Association and its project partners for this exciting, fast-paced fish passage improvement project, which included both the removal of the Spoonville Dam and the design of a nature-like fishway at the Winchell-Smith Dam. The Farmington River is a renowned Wild & Scenic River in Connecticut and this project looked to improve fish passage for historic runs of diadromous fish at both sites.
The Spoonville Dam, a 35-foot-high concrete dam that was partially breached during the historic 1955 floods, is the first partial barrier to fish passage on the Farmington River. The dam is located in the Tariffville Gorge, just downstream from an outstanding whitewater rapids heavily utilized by whitewater enthusiasts. A transparent design process and open lines of communication with whitewater boaters were critical parts of the development of the final design, in order to ensure project buy in from the key project stakeholders.
The second barrier on the Farmington is the Winchell-Smith Dam. The Winchell-Smith Dam is a low head timber crib dam that had already lost the upper two to four feet of the dam in previous high flow events. The dam currently provides a well-known scenic overlook from the dam’s mill that has been converted into a popular local restaurant. Site aesthetics were a critical design component and the design approaches needed to be approved of by the dam and restaurant owners.
Princeton Hydro was initially tasked with designing a bypass channel around the dam but found during our geotechnical field investigation that the overbank area was dominated by collapsible soils which could potentially cause an unintended channel avulsion and dam circumvention if the bypass channel was constructed. We then proposed a partial rock ramp fishway extending in an upstream direction from the dam in order to minimize cost while maximizing the site’s fish passage effectiveness based on the target fish species’ behavioral needs.
Princeton Hydro was contracted by the Town of Greenwich, Connecticut to develop a coastal resilience plan in anticipation of changing conditions due to climate change. The Town possesses 27 miles of shoreline along the Long Island Sound, with 7 of 30 islands in its eight harbors being town-owned. Greenwich, like many coastal communities, already experiences coastal, pluvial, and fluvial flooding which disrupts traffic patterns, impacts infrastructure, and damages town and private assets. In order to protect these coastal areas, which provide a variety of environmental, economic, and community benefits, our team is working to develop a plan that makes sense and will not only protect but enhance Greenwich’s coastal areas.
The work for this project is broken up into two phases, Phase 1 includes a suite of analyses to identify specific areas that are at risk, assess the extent of exposure to flooding, provide concepts for enhancing resiliency, and prioritize specific recommendations for upgrading the municipality’s assets. These assessments are interdisciplinary and aim to provide a holistic overview of the built, physical, and natural systems within Greenwich Connecticut. A key component of our assessment and Plan is to not only provide information needed for planning and decision-making, but to also provide information to the general public. To meet this objective, Princeton Hydro will arrange and facilitate two public information sessions. Here, the Princeton Hydro communications team and experts will present our findings along with a Q&A session, provide a primer on climate change and its effects on sea level, and allow for public feedback to maximize public participation.
During Phase 2, our team plans to specifically analyze the effects of tidal migration on the town's four pond complexes. Our plan will provide specific recommendations on how to transition the ponds and shoreline areas to adapt to changing future conditions, with the ultimate goal of maintaining the town’s most important natural resource for public use. The Princeton Hydro team will employ field and modeling techniques to monitor water quality, assess pollutant loading & sediment dynamics, and conduct biological surveys. Like Phase 1, Phase 2 will also include a public information session to present our findings, discuss projected conditions of the ponds, and provide a number of management options to suit future conditions.
Princeton Hydro was contracted to provide engineering design, permitting, and construction oversight services for the removal of the Heminway Pond Dam located on Steele Brook in Connecticut. The project was part of a larger-scale Watershed Based Plan for Steele Brook Watershed and the restoration of fish passage along the Naugatuck River.
The project included the field assessment and design of the Heminway Pond Dam removal and the associated channel restoration and stabilization. Additionally, our team led the preparation of a sediment sampling plan in coordination with the Connecticut Department of Energy and the Environment (CTDEEP), sediment sampling and analysis, and a CTDEEP-approved sediment management plan. The impounded sediments contained metals and PAHs, with an average sediment depth of four feet. One of the primary design goals was to retain and stabilize as much of the impounded sediment as possible on-site to reduce the dam removal construction costs.
The project also included the preparation of hydrologic and hydraulic analyses/modeling; federal, state, and local environmental permit packages, including a Section 106 Historic Consultation, and several public information meetings. To ensure constructibility of final designs and reduce construction costs, the project design and cost estimate were completed in coordination with RiverLogic Solutions, a contractor specializing in dam removal that frequently works in conjunction with Princeton Hydro.
Historic, archaeological, and social issues were a major concern at this site, so a detailed historic consultation and public outreach plan was integrated into the design process from the onset of the project.
Critical funding for implementation was provided by CTDEEP, and removal was completed in 2018. Princeton Hydro worked closely with the City of Watertown and the selected contractor to oversee and guide construction, which entailed removal of the concrete spillway, excavation and relocation of hundreds of yards of impounded sediment, and reconstruction of over 1,000 feet of river channel.
The U.S. Environmental Protection Agency featured the Heminway Pond Dam Removal and Steele Brook Restoration project as a "Nonpoint Source Success Story." Click here to read it now. Be sure to click on the link within the “Success Story” to view the dam removal video that was created as part of the project:
Princeton Hydro was contracted by the U.S. Army Corps of Engineers to perform rigorous Periodic Levee Inspections for the following six levee systems in the Northeast:
The purpose of these inspections was to verify proper operation and maintenance, evaluate operational adequacy and structural stability, review design criteria to identify changes in current design standards, identify features to monitor over time, and communicate the overall condition to the USACE Levee Safety Officer.
The inspections consisted of collaboration between geotechnical, civil, mechanical, electrical, and H&H engineering disciplines. Our team inspected over 4 miles of levee systems, which included over 3 miles of levee embankment, 0.6 miles of floodwall, 0.13 miles of channel, 3 pumping stations, 39 interior drainage structures, and 5 closure structures (including 1 tide gate).
Princeton Hydro prepared a Periodic Inspection Report for each of the six levee systems inspected, which included the results of the design criteria review, methods, and results of the field inspection; a summary of areas/items of concern; a preliminary engineering assessment of causes of distress or abnormal conditions; and recommendations for remedial actions to address identified concerns. Final report development included briefing the USACE Levee Safety Officer (LSO) on our inspection findings, assigned ratings, and recommendations.
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