The Death of the Dams: Impact of Recent Dam Removals in NJ

 

HST 401-A

Alexander Stapkowitz

5/2/2025

The Death of the Dams: Impact of Recent Dam Removals in NJ

              The last time I visited one of my favorite fishing spots on the Pequest River, I noticed something different. The four-foot-high rock dam that spanned nearly seventy-five feet across the river was gone. I later found out that the long-deteriorated dam was the first of four dams on the river to be removed, as a part of the growing effort nationwide to demolish aging dams along our rivers and creeks. So why are we all of the sudden removing dams, especially those in New Jersey?

            Well, the short answer is that many dams on our rivers and creeks are DEAD. Of the 1,700 regulated dams in New Jersey (dams over five feet tall), only ten percent are still used for their original purpose such as power generation or flood control.¹ This is in part due to the abandonment of many industrial facilities such as sawmills, forges, paper mills, and grist mills that once operated along our waterways. With many of these operations being long gone, hundreds of concrete dams in New Jersey have been left unmaintained and are experiencing significant deterioration, as the lifespan of reinforced concrete in dam applications is roughly fifty years.² Not only are most of New Jersey’s dams over fifty years old (some being well over 100), but nearly one-third of regulated dams in New Jersey are classified as high-hazard or significant-hazard potential.³ This means that they could cause substantial property damage or even loss of life if a failure were to occur.

 

NJ Dam Distribution Map

            Further contributing to the problem of dam deterioration is sedimentation and the buildup of silt. Years of precipitation events have washed sediments into riverbeds and the slower flowing water above dams has allowed these sediments to accumulate over time, exerting more pressure on dams and even threatening their structural integrity. On major waterways in New Jersey such as the Passaic River, contaminants from former riverside industries have washed into the river and accumulated into toxic sludge, which continues to degrade the health of the ecosystem.⁴ With less water being present above dams due to silt buildup and increased evaporation, dams are less useful for water storage and are contributing to declining water quality, oxygen levels, and habitat for native species.² Additionally, dams with large silt deposits are leading to higher water temperatures that trigger harmful algae blooms. With so many of our dams already in bad shape and negatively impacting the environment, what can we expect with the intensification of climate change?

            As climate change is contributing to the intensification of storm events, dams across the country are becoming increasingly more hazardous to communities. One example can be seen in California, where the Oroville Dam (one of the tallest in the country) sustained spillway damage from heavy rainstorms in 2017. As a result of the damage, nearly 190,000 downstream residents were required to evacuate their neighborhoods.⁵ Just in the past ten years, over 16,000 dams nationally have been bumped up to the high-hazard potential classification, which signifies ‘probable loss of life’ or ‘extensive property damage’ if they were to fail.⁶ With the average age of America’s 90,000 dams being about 64 years old, the American Society of Civil Engineers (ASCE) gave them a D+ rating regarding condition and public safety in their 2025 Infrastructure Report Card.⁶

            Thinking about the design of dams with respect to climate change, many dams were simply not designed to handle the increasing magnitude and frequency of storms we see today. According to the State of New Jersey 2024 All-Hazard Mitigation Plan, “annual precipitation is expected to increase by 4% to 11% by 2050, which could influence the hydrographs of many dammed rivers in the state. As a result, it is conceivable that a dam could lose some or all of its entire designed margin of safety, also known as freeboard. Loss of designed margin of safety may cause floodwaters more readily to overtop the dam or create unintended loads. Such situations could lead to a dam failure”.³ Being that New Jersey is the most densely populated state in the country (nearly 1,300 people per square mile on average), dam safety is a growing concern during major storm events that put over 1.2 million residents at risk of severe flooding.⁷ Utilizing Hurricane Irene as an example, a total of six dams failed in New Jersey, while 51 were damaged from intense floods.³ Fortunately, the dams that failed were relatively small and did not directly cause any human casualties. But not knowing how intense the next major storm event might be, many engineers, environmental scientists, and government officials have started taking action to address the risks posed by our aging dams.

Rahway River Dam (Hurricane Irene Flooding)

             Over the past five years, dam removals in New Jersey have started to gain traction, with a total of 17 projects being initiated, ranging from small dams on creeks to large dams along major rivers such as the Raritan River. While this may not seem like a lot, only 34 dams were removed between the years 1985 and 2015, which goes to show the increasing interest in demolishing dams that no longer serve a purpose.¹ While the alternative to dam removals is dam repairs, the long-deteriorated state of many dams (almost beyond repair) coupled with the long-term costs of continuous maintenance make removing dams the more practical solution in many cases (especially from a safety and environmental perspective). To rehabilitate high-hazard dams in New Jersey alone, an estimated $360 million would be needed, while $34 billion would be needed to fix high-hazard dams nationally.⁸ While dam removals can also be costly, ranging anywhere from $100,000 to over $50 million (depending on size and location), the benefits of eliminating maintenance costs, reducing safety risks, and improving the health of rivers make dam removals highly appealing.

            Removing dams comes with a number of challenges, as it involves extensive coordination between local conservation groups, municipal and county officials, state agencies such as the New Jersey Department of Environmental Protection (NJDEP), National Oceanic and Atmospheric Administration (NOAA), Federal Emergency Management Agency (FEMA), and sometimes the U.S. Army Corps of Engineers. One of the challenges unique to New Jersey is the fact that 48% of all dams in the state are privately owned, which makes coordinating removals and obtaining funding from landowners more difficult.¹ Another challenge prevalent today is the process of securing adequate funding, which often comes from state sources (NJDEP), federal sources (NOAA), or private conservation organizations. However, with cuts to funding from sources such as FEMA and NOAA, the process of obtaining funding for dam removal projects is bound to become more difficult and could certainly delay (or even cancel) some future projects. In addition to coordination and funding challenges, many dams are located in remote locations, which makes accessing them and bringing in large excavators or removing debris extremely challenging (while also driving up costs). Relating to the problem of sedimentation, removing dense layers of silt (up to ten feet in extreme cases) must be done before dam removals can occur, as the release of silt downstream can be detrimental to the river’s health. This only becomes more difficult when pollutants are embedded within the sediments, bringing up the question of proper disposal and finding the right place to store contaminated silt.

            Despite these difficulties, dam removals have many substantial benefits. In addition to improving water quality, dissolved oxygen levels, water temperatures, and aquatic habitat, removing dams allows for the return of migratory species such as American shad and American eels. The movement and spawning of these species has been restricted for years by dams, but the restoration of free-flowing rivers has allowed them to return to waterways such as the Musconetcong, Paulinskill, Millstone, and Raritan rivers in New Jersey. From the standpoint of safety, removing dams reduces flood risks for downstream communities and improves recreational opportunities for boaters and fisherman like myself. Between 2018 and 2021, 149 drowning deaths in the United States occurred due to low-head dams.² Therefore, removing these dams can dramatically improve safety for those seeking recreational opportunities or those who have rivers in their communities.

Low-Head Dam Demolition (Raritan River)

            An example of a successful dam removal in New Jersey can be seen on the Paulinskill River, in which the Columbia Lake Dam was removed in 2018. The dam was 330 feet long and 18 feet high when it was built in 1909 for hydroelectric power generation.⁹ Removing the dam cost nearly $8.5 million, with funding from local, state, and federal sources. While many dam removals can take up to four years (depending on site location and sedimentation), this dam was removed in about 1.5 years from site preparation to cleanup. Being that the dam was located just a quarter mile upstream from the Delaware River, its removal allowed for the quick return of American Shad into the Paulinskill River after nearly 100 years. Not only did water quality and natural habitat improve, but nearby communities are experiencing less flooding as a result of the dam removal.

 

Columbia Lake Dam (Before and After Removal)

            While there are many ways to critique dams, some dams actually continue to serve a positive purpose. In fact, dams on large reservoirs are essential for the storage of drinking water (which is especially important during drought conditions). Without these dams, man-made reservoirs would technically not exist and would not be able to control the release of water to downstream communities. One example in New Jersey is Round Valley Reservoir, which is the largest reservoir by volume in the state, capable of holding 55 billion gallons of water at full capacity.¹⁰ While reservoirs are not candidates for dam removals, they still suffer from deteriorating dams that pose safety risks to the public and threaten the storage of large quantities of water.

Round Valley Reservoir (Embankment Dam)

            Returning to the Pequest River (one of my favorite fishing spots), three more dam removals are scheduled to begin in the next few years. Removing these dams will not only improve fishing opportunities for myself, but will reduce flooding for the many homes and businesses along the river in the small town of Belvidere. As many functionless dams along rivers continue to degrade and act as ecological barriers that diminish waterways, their existence is becoming increasingly concerning. With strengthening rain events and climate change, the desire to remove these dams for safety reasons will only increase in the coming years. While many upcoming large dam removals on waterways such as the Musconetcong and Raritan rivers have moved closer to being initiated over the past couple years, it will be interesting to see how recent funding cuts offset these projects. Maybe these dams will remain DEAD in our waterways for several more years, but we must nonetheless be aware of their growing safety and ecological implications as our climate changes.

References

1.    1. Hamilton, Pat. “Restoring Free-Flowing Rivers.” NJDEP, 2017, https://dep.nj.gov/njfw/wp-content/uploads/njfw/digfsh_damremoval.pdf

2.     2. Tippett, Mara. “The History & Science of Dams and Their Removal.” Raritan Headwaters, 22 Aug. 2024, www.raritanheadwaters.org/2024/08/21/the-history-science-of-dams-and-their-removal/.

3.     3. “State of New Jersey 2024 All-Hazard Mitigation Plan.” State of New Jersey, 2024, https://nj.gov/njoem/mitigation/pdf/2024mit/08_Section_4_3_Dam_Levee_revised_20240802.pdf

 

4.     Lewis, Robert. Passaic River Coalition (PRC), 2017, Passaicriver.org/.

 

5.     Phillis, Michael, and John Hanna. “Worsening Floods and Deterioration Pose Threats to US Dam Safety.” AP News, AP News, 3 July 2024, apnews.com/article/dam-failures-safety-repairs-1e40fa79a59b4e307d944beb258b91be.

 

6.     “2025 Infrastructure Report Card: ASCE’s 2025 Infrastructure Report Card.” ASCE’s 2025 Infrastructure Report Card |, 28 Mar. 2025, infrastructurereportcard.org/.

 

7.     “Why Remove Dams?” New Jersey Dams, 21 Apr. 2020, njdams.org/why-remove-dams/.

 

8.     Ingram, Elizabeth. “$157.5 billion Needed to Rehabilitate Non-Federal Dams in the U.S.” Factor ThisTM, 21 Apr. 2023, www.renewableenergyworld.com/hydro-power/dams-civil-structures/157-5-billion-needed-to-rehabilitate-non-federal-dams-in-the-u-s/.

 

9.     Hydro, Princeton. “Dismantling the Past, Renewing the Future: Removing Paulina Lake Dam on the Paulins Kill River.” PRINCETON HYDRO, 2 Aug. 2024, princetonhydro.com/Paulina-dam-removal-first notch/.

 

10.  “Round Valley Reservoir.” Schnabel Engineering, 3 Jan. 2025, www.schnabel-eng.com/projects/round-valley-reservoir/.