Lessons from the Assabet: Dynamics of Dam Removal Along a New England River
Lessons from the Assabet: Dynamics of Dam Removal Along A New England River
Travis Kelley
Introduction
Waterways across New England have been deeply impacted by human activity and today represent a regional landscape characterized by numerous dams and impoundments. With a history of human use extending back thousands of years, these rivers are vital ecological corridors that have also provided sustenance for countless birds, fish, mammals, and invertebrates for millenia. In many Indigenous cultures, rivers are approached with reciprocity and seen as relatives (“water kin”1) to be protected and cherished, held in trust by the collective. In contemporary times, this notion of protecting water as a commons, “hydrocommons,”2 is gaining momentum once again, and with it an eagerness to reconnect communities to the waterways that enabled settlement historically and are still relied upon in our everyday lives today.
Today’s rivers hardly resemble those experienced by pre-contact Native American peoples. By the early 17th century, European settlers began to use natural points of constriction along waterways as sites to generate power for
1 Yazzie, Melanie K. and Baldy, Cutcha Risling. “Introduction: Indigenous peoples and the politics of water. Decolonization: Indigeneity, Education & Society. Volume 7, No 1. 2018. P. 1-18. Quoting Zoe Todd (2017) 2 Neimanis, Astrida. “Bodies of Water, Human Rights and the Hydrocommons.” TOPIA: Canadian Journal of Cultural Studies 21 (May 1, 2009). https://doi. org/10.3138/topia.21.161.
mills. With the coming of the Industrial Era in the mid-late 19th century, these modest dams gave way to hydraulic manipulation of a grander scale, and soon nearly every river or creek with enough water to power mills was dammed. With these dams came unregulated pollution dumped from the surrounding mills, which collected over time in the impoundments of dams downstream. As technology and economic systems evolved, the riverbased mill culture of New England declined and the dams largely fell out of use. Today, ecologists have come to understand these structures are harmful to the ecological health of New England, and significant effort has been made to remove them3 Yet some of these efforts have been strongly opposed by the surrounding communities, and 14,000
3 Hart, David, Thomas Johnson, Karen Bushaw-Newton, Richard Horwitz, Angela Bednarek, Don Charles, Danielle Kreeger, and David Velinsky. “Dam Removal: Challenges and Opportunities for Ecological Research and River Restoration.” BioScience 52 (January 19, 2009): 669–82. https://doi.org/10.1641/00063568(2002)052[0669:DRCAOF]2.0.CO;2. Pohl, Molly M. “Bringing down Our Dams: Trends in American Dam Removal Rationales.” JAWRA Journal of the American Water Resources Association 38, no. 6 (2002): 1511–19. https://doi. org/10.1111/j.1752-1688.2002.tb04361.x.
dams still exist across New England.4 Nine of them are on the Assabet River in east-central Massachusetts, and their stories exemplify many of the challenges the dams present. Through exploring how the ecological and social issues around dam removal manifest along the Assabet watershed, we can better
understand how this regional condition functions, investigate why dam removal is so divisive, and explore methods for how these challenges might be overcome in the future.
Assabet Dams, Tributaries, Wastewater Facilities
The above elevation profile, taken from a June 2008 Sediment Modeling Report, shows locations of the river’s tributary confluences, discharges from wastewater treatment facilities, dams, and impoundments.
4 Fox, Coleen A., Francis J. Magilligan, and Christopher S. Sneddon. “‘You Kill the Dam, You Are Killing a Part of Me’: Dam Removal and the Environmental Politics of River Restoration.” Geoforum 70 (March 2016): 93–104. https://doi.org/10.1016/j.geoforum.2016.02.013.
Historical Context
The Assabet is a 32-mile river, which ends at its confluence with the Sudbury River to form the Concord River. From there, the water flows north to Lowell, where it meets the Merrimack River and eventually flows into the Atlantic Ocean at Newburyport, Massachusetts. These lands are the ancestral home of the Nipmuc, Agawam, Pawtucket, and Massachusett peoples,1 many of whom lived seminomadic lives, migrating between coastal and inland locations seasonally. Indigenous people utilized fiber from riverbanks for weaving, the rich wildlife and plant abundance found at the rivers for sustenance, and the water flows themselves as transportation corridors. In the spring, anadromous fish such as herring, Atlantic salmon, and shad migrated into freshwater rivers to spawn, providing an abundance of food for Native people at a critical time as the winter snows melted.2 Indigenous people built weirs, usually constructed of wood, which helped them to catch fish as they migrated upstream. The construction and use of weirs became a cultural gathering point for communities, and the predictability of these migrations and relatively low danger and expenditure of energy to capture the fish made this a pillar of the seasonal
cycle of Indigenous life.3 The confluence of the Assabet and Sudbury Rivers is a known site of Indigenous fish weirs, and two other sites have been identified in Marlborough and Northborough, which are upstream areas, indicating that the entire river would have been used for spring migration fishing.4 The word “Assabet” is the traditional Algonquian name for the river, and means “the place where fishnet-making materials grow,”5 indicating that wet meadows were once a dominant part of the floodplain. While some areas along the riverine corridor still resemble that description, the impacts of colonial settlement have come to dominate the river through a series of dams, impoundments, and channel walls of stone and concrete.
3 Lutins, Allen. “Prehistoric Fishweirs in Eastern North America.” Master’s Thesis. Graduate School of the State University of New York at Binghamton. May 1992 4 US Army Corps of Engineers, New England District. “Assabet River, Massachusetts: Sediment and Dam Removal Feasibility Study,” September 2010.
5 “Assabet River Facts.” Organization for the Assabet, Sudbury and Concord Rivers (OARS). https:// oars3rivers.org/our-rivers/river-facts/
The SuAsCo Watershed
The Sudbury, Assabet, and Concord River watershed, often referred to as “SuAsCo” Watershed, is in eastern Massachusetts. The Assabet’s watershed is outlined in dark blue, while the dams are marked in magenta. Two breached dams, one on the Assabet and one on the Concord River in Lowell, are marked with broken magenta lines. The Essex Dam, on the eastern quadrant of the Merrimack River, marks the only dam between the ocean and the Concord River’s confluence with the Merrimack.
Lowell
Nashua
Newburyport
Concord River
Boston Massachusetts
Merrimack River
Sudbury River
Assabet River
Concord
Massachusetts Bay
Atlantic Ocean
Context (cont’d)
Industrialization along the Assabet follows a familiar narrative to many other watersheds across the region. Development along the corridor was slow in the early days of colonization, with the conclusion of King Philip’s War opening up the area to settler expansion. While towns such as Stow, Sudbury, and Concord date to this era, most of the contemporary towns directly abutting the river came to exist later, as a direct result of harnessing the river’s power for industrial purposes. Hudson, for instance, was originally called “The Mills,” so named for the grist mills and tanneries that existed there throughout the 1700s. By the early 19th century, it had become known as “Feltonville,” after a wealthy mill owner, and finally was incorporated as a separate town in 1866, by which time it had a plethora of mills, including at least five shoe factories.1 Nearby Maynard, named for mill owner Amory Maynard, has a similar story and dropped its “Assabet Village” name and separated from Sudbury to become its own town in 1871.2 Yet the Ben Smith Dam, mill pond, and the expansive mill complex had been constructed several decades prior, and was one of the largest textile mills in the country. Within a national context, New England’s textile mills represent one of many ways in which the
1 US Army Corps, “Assabet River,”
2 Gutteridge, William H. A brief history of the town of Maynard, Massachusetts. Maynard, Pub. by the town, 1921. Pdf. https://www.loc.gov/item/21006952/
region’s economy was tied to the institution of slavery and subsequent Jim Crow-era power systems, as virtually all the cotton processed in this area came from the South. Other local industries were connected with the wider economy of the United States as well. The American Powder Mills in present-day Acton, for instance, supplied thousands of pounds of gunpowder to the US Government every week during the Civil War. The dams and remaining mill complexes are the physical manifestation of these histories, and in many cases have come to be viewed as important cultural monuments to the industrial origins of the surrounding communities.
Historical
Rail Connections
This detail of a historic map from 1866, courtesy of the Osher Map Library, shows how well connected these communities were. “Feltonville” is the historic name for Hudson, while “Rockbottom” is current day Gleasondale, and “Assabet” is present-day Maynard.
Shoe Manufactory
This image shows the Tower Brothers Shoe Manufactory on the shore of the Assabet in Hudson. It was one of 5 shoe factories in town.
Slowing of water causes sediment to settle
Increased water levels
The Impact of Dams
Original water surface
Limited fish migration
Sedimentation
This diagram displays some of the impacts that dams have on a river. The impounded water slows and warms, causing sediments to drop and accumulate behind the dam. This impacts sediment patterns downstream. Dams also block fish passage–both local, freshwater fish, as well as andromous fish, which spend most of their lives in the ocean, but travel upstream into freshwater to spawn. The dams of New England have drastically impacted this cycle, decimating New England fisheries.
Decreased sediment transport downstream
Anadromous fish passage blocked
Ecological Considerations of Dams
The ecological concerns that dams raise are both physical and chemical, in that the structures limit the potential for aquatic life to travel freely throughout the system, and the impoundments alter the flow of sediment and temperature of the water.1 There are some cases in which dams might be beneficial in that they limit the spread of invasive aquatic species, but the fragmentation that dams cause is generally considered to have a negative impact on the overall ecological system. The disconnection tends to favor generalist species over specialists, meaning that more rare species have less habitat, and the slow-moving impoundment water is consistently measured to have lower quality than in segments with free-flowing water. Apart from this, dams have an enormous impact on anadromous fish species, which migrate from their ocean habitats to inland freshwater systems to spawn.2 The
1 Brown, Rebecca, Don Charles, Richard Horwitz, James Pizzuto, Katherine Skalak, David Velinsky, and David Hart. “Size‐dependent Effects of Dams on River Ecosystems and Implications for Dam Removal Outcomes.” Ecological Applications 34 (August 13, 2024). https://doi.org/10.1002/eap.3016.
Magilligan, F.J., B.E. Graber, K.H. Nislow, J.W. Chipman, C.S. Sneddon, and C.A. Fox. “River Restoration by Dam Removal: Enhancing Connectivity at Watershed Scales.” Edited by Anne R. Kapuscinski and Julian D. Olden. Elementa: Science of the Anthropocene 4 (May 31, 2016): 000108. https://doi.org/10.12952/journal.elementa.000108.
Zaidel, Peter A., Allison H. Roy, Kristopher M. Houle, Beth Lambert, Benjamin H. Letcher, Keith H. Nislow, and Christopher Smith. “Impacts of Small Dams on Stream Temperature.” Ecological Indicators 120 (January 1, 2021): 106878. https://doi.org/10.1016/j. ecolind.2020.106878.
2 Druschke, Caroline, Emma Lundberg, Ludovic Drapier, and Kristen Hychka. “Centring Fish Agency in Coastal Dam Removal and River Restoration.” Water
dams prevent this cycle from occurring, and are the primary cause for the decline of alewives, salmon, and American shad across the region.3 The impoundments also slow the water, allowing sediment to settle and increasing the water temperature, dramatically altering the water conditions above and below the dam.4 The movement of sediment downstream is also considered vital to ecological functionality across the watershed, manifested most acutely in the coastal salt marshes, which are slowly drowning due to the lack of sediment accretion and rising water levels due to climate change. Since every dam and context is different, all these factors must be considered in the process of river restoration.5
Alternatives 10 (October 1, 2017).
3 Fox et al. “You Kill the Dam,” 97
4 Hart et al, “Dam Removal” Grant, Gordon E., and Sarah L. Lewis. “The Remains of the Dam: What Have We Learned from 15 Years of US Dam Removals?” Engineering Geology for Society and Territory - Volume 3, 2014, 31–35.
5 Poff, N. Leroy and Hart, David D. “How Dams Vary and Why It Matters for the Emerging Science of Dam Removal.” BioScience Vol. 52, no. No. 8 (August 2022): 659–68.
Hoenke, Kathleen M., Mukesh Kumar, and Lynnette Batt. “A GIS Based Approach for Prioritizing Dams for Potential Removal.” Ecological Engineering 64 (March 1, 2014): 27–36. https://doi.org/10.1016/j. ecoleng.2013.12.009.
Dams and Water Quality of the Assabet
These issues are well represented in the case of the Assabet River. Seven historic dams, one of which is breached, and two modern dams, stand along the river, with over 100 more within the watershed. With the proliferation of industry along the water and few regulations, the Assabet, like most New England rivers, endured decades of contamination from these businesses, much of which settled into the impoundments behind dams downstream.1 A report on the Assabet River sediment from 20082 details the varied contamination levels in the impoundments being considered for dredging, which would accompany dam removal, and showcases the continuing legacy of the polluting mill culture.
1 Zimmerman, Marc J., and Jason R. Sorenson. “Sediment Studies in the Assabet River, Central Massachusetts, 2003.” Scientific Investigations Report, 2005. https://doi.org/10.3133/sir20055131.
2 CDM Smith Engineering, Prepared for US Army Corps of Engineers New England District. “Assabet River Sediment and Dam Removal Study Modeling Report,” June 2008.
Even with the collapse of most mills along the river and the considerable impact of the Clean Water Act in 1972, The Assabet struggled with water quality through the 20th century. In the 1980s, it garnered the unfortunate nickname of “The Cesspool of Massachusetts”3 due to the pollution which impacted the visual and olfactory enjoyment of the river. In conversation with a longtime river advocate, she described how buildings were commonly constructed without windows facing the river, and how real estate agents routinely found alternative routes when bringing prospective buyers to properties to avoid traveling near the river. It was seen as a detractor, its smelliness an indisputable indicator of its degradation. In the public comment section of the 2010 feasibility report, one resident writes of the “oil slicks” and “raw sewage” she observed in the 1960s, which she claims was in part a result of illegal dumping of untreated human waste in the river during the night carried out by the Town of Hudson. The revelation of these actions coincided with the environmental movement of that era, but improvements were slow, and phosphorus levels continued accelerating in a positive feedback loop.
River Facts,” (OARS)
Dams and Water Quality of the Assabet
(cont’d)
By the early 2000s, the Assabet was officially classified as “impaired” and a number of studies were carried out to understand its condition, sediment composition, and sources of pollution. The high nutrient load, caused mostly by the wastewater treatment facilities, identified as the primary point pollution sources, combined with the warmer, slower-moving water of the impoundments, resulted in eutrophic conditions, characterized by explosive growth of duckweed and algae. These organisms cover the water’s surface, blocking light and reducing dissolved oxygen levels, only to die back in the fall and release these nutrients back into the water to continue this detrimental cycle. In 1999, data collected by river advocacy nonprofit OAR (now OARS) became certified as quality controlled by governmental authorities, which marks the beginning of quantitative data that helps illustrate the river’s degradation scientifically, though collected data dates to 1992.1 The data showed what locals already knew: significant effort must be made to clean up the Assabet.
As solutions to water quality issues were sought, dam removal was considered, along with other strategies, such as upgrades to the wastewater treatment facilities that discharge into the river. The Assabet Consortium was formed with representatives from communities along the river, and a coordinated effort was made to reduce phosphorus levels and aquatic biomass in the river by 90% through the establishment of a total maximum daily load (TMDL) regulation. The facility upgrades, which occurred in phases over roughly ten years and cost a combined $100 million, resulted in marked improvements to water quality and the project was hailed a success2 (US EPA 2015). Contemporary data, which will be relayed in a subsequent section, shows that these efforts have been insufficient to meet biomass goals in the impoundments.
1 http://www.assabetriver.org/wq/
2 United States Environmental Protection Agency, Office of Water. “Six Municipalities, One Watershed: A Collaborative Approach to Remove Phosphorus in the Assabet River Watershed.,” March 2015.
Impact of Wastewater Treatment Facility Upgrades
The graphs above show the troubling levels of contamination being discharged into the Assabet in the late 1990s and the significant impact of upgrades to the facilities. Graphs courtesy of United States Environmental Protection Agency, Office of Water. “Six Municipalities, One Watershed: A Collaborative Approach to Remove Phosphorus in the Assabet River Watershed.,” March 2015.
The Feasibility Report
Prior to the completion of most upgrades and associated water quality improvements, a feasibility study was conducted by the US Army Corps of Engineers, studying how dam removal would impact water quality. This report,1 published in 2010, included assessment of fish species, sediment dispersal, surface and subgrade water levels, and other impacts of dam removal.
The report’s main conclusions particularly favored the removal of the Ben Smith, Gleasondale, and Hudson dams, with the other three historic dams that were also studied concluded to have a lesser impact on overall river water quality. It shows the composition of fish species to be largely generalist, pollution-tolerant species, a varied plant community including many invasive plants, and poor water quality in the dam impoundments. A detailed plant list correlated spatially using aerial photographs showed plant communities along the river, and the aquatic organism appendix outlines existing fish species (EFS) and target fish species (TFS) for small rivers in this region. While the report is largely technical in nature, an appendix also gives context to the cultural resources adjacent to the river. One of the most significant findings was that winter discharge levels had a significant impact on phosphorus levels during the growing season, as the
1 US Army Corps, “Assabet River,”
compound attached itself to sediments in the impoundments, and was a significant source of nonpoint pollution. More stringent winter TMDLs were implemented as a result of this finding.
While this was a preliminary study, this report has been an invaluable source of information on how legacy dams impact rivers, and how these efforts are often perceived by local residents. A public comment appendix included at the end of the report allows us to better understand public opinion at the time when a preliminary version of the document was released to the public. These written comments were submitted to the Army Corps of Engineers in response to a draft version of the report, allowing residents to comment, ask for inclusion or exclusion of information, and express their opinions about the potential impacts of removal.
Ben Smith Dam
Hudson Dam
Dams With the Most Impact
Gleasondale Dam
The three main dams that the report identified as having the largest impact of overall water quality on the Assabet River were the Hudson Dam (also know as the Washington St or Rt. 85 Dam), The Gleasondale Dam, and the Ben Smith Dam.
The Gleasondale Mill Complex
Situated in a quiet part of Stow, the Gleasondale Mill area was once a thriving commercial hub. The railroad previously stopped here at a station named for nearby Rockbottom Farm.
Public Concerns Related to Dam Removal
While ecologists agree on the benefits of dam removal, New England communities have historically been skeptical about removing dams. Fox et al. wrote about the “micro-politics” of dam removal in 2002, relaying a number of reasons why these efforts prove to be so contentious. The public comments in the 2010 report illustrate how many of the concerns shared by other New England communities were also of concern along the Assabet.
Outsiders
The perception of the dam removal advocates–their intentions, approach, and dictation of the outcome–can in itself lead to opposition for removal. Dam removal advocates are ususally equipped with scientific evidence about the environmental benefits of removal, engineering statistics about the looming safety hazard that the dam(s) present, and too frequently fail to see the issue as being inextricably linked to cultural and sociopolitical sensibilities.1 These advocates are often perceived as outsiders who are coming into the (often rural) community to determine how the landscape is to be shaped. Local residents understandably feel that their autonomy is being removed, and mobilize to protect the perceived threat to their community. One resident said he and his neighbors were “universally appalled by the whole procedure” and described his contacts as “look[ing] with alarm on those outsiders who apparently think they act [o]n our behalf.” He goes on to detail how “at one of the meetings, the Army Corps representative smiled smugly and implied that the protesters were common ‘treehuggers,’” and concluded, “With this kind of ‘dispassionate’ and biased opinion running the show, we who are citizens feel steamrollered by a machine which has no particular feeling for the area they seek to destroy.” Other residents questioned the integrity of the report, implying that the Army Corps of Engineers and other agencies had an agenda in the framing of the report’s findings. The report “Smacks of corruption and collusion between the upriver towns and the DEP,” writes one resident, while another scathingly describes the Corps of Engineers as “an agency which did such a fine job destroying the Mississippi River basin.”
1 Fox et al. “You Kill the Dam,”
Existing Ecologies and Aesthetics
Though the leading narrative in favor of dam removal is often framed as benefitting the river’s ecological health, many residents see it as destructive to the upstream flooded ecosystem, which despite being an anthropogenic landscape is in some cases perceived locally as pristine. This highlights how variable the perception of nature is to a broad audience, and how these “artificial ecosystems” are often seen as greatly beneficial.2 These perceptions, of course, are not without merit, as the recreational opportunities are often greatly expanded by the impoundment, and wildlife spotted in these contexts lead to the perception of a vibrant ecology. As one resident put it, “Removing the Ben Smith Dam in Maynard will reduce our beautiful river to a bog, source of mosquitoes and other undesirable insects, and take from us an irreplaceable natural source of renewal.” Another local wrote to protect the “visual treasure” of the Ben Smith impoundment. It is challenging for residents to accept that a restored river also has ecological and aesthetic value, even with the renderings that went along with the public presentations and feasibility report.
The perception of the river as being irreparably damaged by dam removal is challenging for proponents to overcome. The public comment section of the report is full of these concerns. “You are attempting to ‘save’ the river by basically eliminating it,” writes one resident, adding “Just because a thing can be done doesn’t mean it should be.” Another comment worries that dam removal
2 Fox et al. “You Kill the Dam,”
The question of smell and mud was raised numerous times in this process, with one local asking “How long will we be looking at a mud pit (and how long will it smell?)” In the early 2000s, there was a lack of consensus within the restoration community of the overall impacts of dam removals, but today scientists are agreed that river bank revegetation is relatively swift. A 2024 OARS report, discussed more later, shows that invasive purple loosestrife is well established along the Assabet, but the necessity of plant monitoring following dam removal is a given. The issue of exposed mud also raises questions about the safety of these sediments. “What will happen to the safety and health of my family when exposed to these materials [heavy metals, etc]?” asks another writer. They continue, “The area behind my home will be turned into a brown field. Is that really what communities’ desire?” Numerous other comments raise the issue of who will pay for the cleanup and revegetation of these newly-exposed areas.
Recreation
The recreational value of the dam impoundments is another common concern when considering removing a dam. “Having paddled much of the Assabet, [I believe] the area that may be affected by the dam removal is the most beautiful section of the river,” writes one resident. Many others echo this sentiment–that the waterway is a wellused and much beloved paddling route, which may no longer be possible if the dams are removed. The previously-mentioned sediment report included drawings of the possible changes to the water levels with removal, and show a much narrower channel. Since the dams in question do not regulate the river’s flow, the same volume of water will continue to flow, albeit through a more narrow and shallow corridor, meaning the detrimental impact for recreation is likely limited times of lowest flow. Yet worries that the river will become a trickle through a smelly mud flat is an evocative, worrying image, and residents tend not to believe consultants that attempt to alleviate these concerns . Even in public comments that thoughtfully describe consideration of the ecological benefits of removal, the loss of the recreational space looms larger. One such commenter writes of the “benefits to having motivated users in place to protect the shoreline and water.” It is true that many river advocates believe that getting people out on rivers is one of the best ways to increase awareness and motivate people to protect our waterways. Will fewer people care about the river if they cannot paddle it? Are there other ways that waterfront design, particularly in town centers, could help motivate residents to take a larger interest in stewardship of the river?
Kayaking the Assabet
The author’s husband on the Gleasondale impoundment, fall 2024
Public Concerns Related to Dam Removal (cont’d)
Business and Economics
Other concerns are more practical and economic in character, such as the potential drop in property value, water tables, and availability of water to support local businesses and fire suppression. “Who will pay for the serious and negative reduction in the value of me and my neighbor’s property? … The market value of these homes will deeply decline,” opines one resident. Waterfront property value and the impact of dam removal is a valid concern that would require further study for the Assabet in particular, but has recently been studied and found to have a negligible correlation, or “null hypothesis” at sites ranging across New England (Guilfoos and Walsh, 2023). Several residents mention the concern about the water table, particularly in Stow, which does not have a municipal sewer system. “Lowering of the water table would be an increased expense for Stow residents who will need to dig a new well,” one resident states. The same resident worries about fire safety, asserting that “a two to three foot deep narrow river will not be enough water to pump from and protect us with. There will be an increase in our homeowners insurance for fire coverage, one more expense for Stow residents. What price do you put on personal safety?” Local businesses also depend on the river to irrigate their land. “The river has served as the primary and essentially only source of irrigation water since [the Gleasonville dam] was first built in the 1920s,” writes the owner of Stow Acres Country Club. Similarly the owner of Honey Pot Hill Orchards, a popular destination for Bostonians during the autumn, writes that their use of the river for irrigation “can mean the difference between profit and loss at the orchard.”These concerns accompanied with more direct costs such as dam removal, dredging, and floodplain restoration underscore how the river impacts the community economically in both direct and indirect ways.
Cultural and Historical Considerations
Perhaps the most visible yet often overlooked aspect of dam removal is how the dams create cultural landscapes for the towns. As previously mentioned, many of the towns along the river came into existence due to the economic activity that the river’s water power provided. Despite the changes in how these landscapes function, they are often much beloved by their communities. The Ben Smith Dam in Maynard is the particular subject of these kinds of concerns, with many public comments related to its removal and the impact it would have on the mill ponds in the downtown district. One writer claims that “they are a central feature of the town, a historical landmark, and necessary for fire suppression for the mill complex. If the dam was removed, flow to the mill ponds would stop.” The feasibility report does state that the removal of the dam would lower water levels to the extent that water would no longer flow by gravity to these ponds, which are a focal point of the town center. Another resident states that “Although privately owned, the Maynard Historical Commission considers the Ben Smith Dam to be a key component of our town’s cultural and architectural heritage,” and essentially threatens that the community would seek protections for it (ie. National Register of Historic Places designation) should further attempts to remove it be made. Another comment talks about how the mill ponds “are visible to a high percentage of people who live and work in Maynard.”
Interestingly, the river also runs through the town of Maynard, but is highly channelized and barely visible unless one is on foot and looking directly down on it from the main street bridge, but is rarely mentioned as being part of the town’s character. It is the mill ponds, which are essentially formed from a side channel that branches off the river’s main stem upstream of the dam (and town), that are the main concern. They have become a vital
cultural landscape, despite serving no practical purpose anymore. The sprawling mill complex, which offers over one million square feet of floor space, is now used as an office complex, and the mill ponds serve an aesthetic purpose to the offices and town at large. It is impossible to put a monetary value on the value that these kinds of landscapes provide a town, and they are often primary drivers of the emotional response to the idea that they would disappear.
Mill Pond Prominance
This 1879 postcard, courtesy of the Maynard Historical Society, shows the prominance of the mill complex and adjacent ponds in the town center.
Public Process
These valid concerns combined with the simple fact that people don’t like change can lead to staunch resistance even when faced with facts related to safety, ecological function, and the economic impact of repairing dams in perpetuity. Greater effort is needed to understand the complicated factors that play into these scenarios, and much can be learned by looking at these situations from a social science perspective.1 By considering how public sentiment is formed and altered, removal advocates can create community buy-in and present “‘win-win-win’ outcomes [with potential to] benefit not only the ecosystem but also dam owners and the local community.”2 Advocates of environmental democracy believe that communities should have significant input in these kinds of decisions, and recent studies have developed methodologies for how to accomplish this. One framework is called Structured Decision Making, which helps residents imagine “a range of approaches that can significantly improve habitat connectivity while allowing the dam and/or impoundment to remain in place.”3 (Vogler 2021, 114). This involves workshops in which residents can better understand the potential outcomes implicit in these approaches, and allows them to rank them using “trade-off cards,” which stimulate conversation about their values. This kind of process alleviates much of the automatic resistance which forms from the perception that outsiders are coming in to dictate what will happen,
1 Johnson, Sarah E. and Graber, Brian E. “Enlisting the Social Sciences in Decisions about Dam Removal.” BioScience Vol. 52, no. No. 8 (August 2022): 731–38.
2 Johnson et a., “Enlisting,” 732
3 Vogler, Emily. “Building Watershed Democracies,” The New Farmer’s Almanac, 2001. 113-116.
and empowers communities to decide the future of the dams for themselves.
In the context of the Assabet, numerous meetings were held to try and engage the public about the potential benefits of dam removal. The executive director of OAR at the time described how small group sessions, framed as “river restoration listening sessions,” were held with residential and commercial abutters, while larger workshops were held in Westborough and Stow. These bigger meetings sought to present a range of perspectives to the gathered community members, including experts in fisheries, climate change, water pollution, and local history. A leading public engagement organization, Consensus Building Institute, was contracted to help lead the process. Yet the community was largely aligned in opposition to the idea that any dams should be removed. The only public comment included in the feasibility study that was unequivocally in favor of dam removal came from the Board of the Westborough Wastewater Treatment Facility, who also wrote in opposition to further limits on their TMDL. Two comments from OAR members, one from the Executive Director, advocated for more time to pass to understand the impacts of the WWTF upgrades, which were largely not yet complete at this time. Citing the lack of community and dam-owner support and uncertainty of cost, she writes that the organization concluded that dam removal was not a “viable option for achieving water quality standards” at that time.
Understanding Future Water Level
These graphics, from a 2008 sediment modeling report, show potential impacts of dam removal for the Hudson and Ben Smith Dam impoundments
The Assabet Today
The built environment adjacent to the river is, in many cases, oriented away from it, which may be a legacy of pollution and public perception of impaired waterways. Many industrial sites and warehouses can be found along the corridor, and the embanked sections that flow through town centers are so far below street level that they are practically invisible unless one is actively seeking it. The remaining mill buildings along the shore are often tall and sprawling, blocking the water from view. In Hudson, the central gathering point of the town sits on a hill above the dam impoundment, but the view is blocked by a mix of public and private buildings. Even in Maynard, where concern for the iconic mill ponds is high, these features are blocked from the main commercial district by the historic mill buildings. The river’s main channel runs between this district and the mill, but can only really be spotted when it floods. A recent conversation with a friend who lives in Marlborough, which discharges its waste water into the Assabet, was not aware of the river at all. Culturally, many local residents do not seem to be conscious of how our drinking water and sanitation is directly tied to the watershed.
As previously stated, the water quality strategic plan set in July 1999 aimed to reduce biomass in the Assabet River, one of the key indicators of a river’s eutrophication, by fifty percent. An October 2024 OARS report details the current state of floating biomass in the impoundments, finding “extreme levels of biomass coverage” in the Hudson impoundment, with high concentrations also found in the Gleasondale and Ben Smith impoundments. In recent years, only the Gleasondale impoundment has consistently met the goals set in 1999 (with 2022 being an exception). The report tracked a significant correlation between rainfall and biomass growth.
During years with less rainfall, the river flow slows, creating favorable conditions for aquatic plant growth. The charts found in the report indicate that the biomass coverage trends have varied between the impoundments, with the Hudson site having the highest increase. The study also included information on invasive water-loving plant species, showing that efforts to eradicate water chestnut has been largely effective, while the proliferation of purple loosestrife plants has increased throughout all three impoundments. Water quality data measuring e. coli content, which is considered the indicator for safe swimming, shows that seasonal fluctuations of these metrics exceed safety thresholds most years. These findings indicate that the desired results of upgrading the WWTFs have not adequately addressed water quality issues, and that perhaps the time has come to reconsider river restoration methods such as dam removal.
The Latest Biomass Data
Above, right: These visuals, provided by OARS, show floating plant mass covering the surface of the three most impaired impoundments, behind the Hudson, Gleasondale, and Ben Smith Dams.
Left: A correlation between biomass growth and rainfall is charted, courtesy of OARS. As climate change brings more drought and storms, the fluxuations in rainfall will continue to have an impact of the profileration of floating biomass.
Waterways across New England have been and continue to be impacted by the results of industrial-era dams, built to power businesses that have long-since disappeared. On the Assabet River corridor, the issues created by these dams and the use of the river as a discharge site for treated municipal sewer discharge has produced degraded water quality and ecological functionality. Though significant effort was made to study methods to address these issues, community opposition to the idea of dam removal prevailed. The concerns of residents echo those expressed in other New England areas, and include a concern for the existing wetland ecologies, property values, water table levels, fire safely, potential public health hazards due to newly-exposed sediments, threats to existing recreational activities, loss of cultural and historical landmarks, and the perception that the river will become a meager stream through an odorous mud flat. While these valid concerns would need to be addressed in any renewed effort towards dam removal, the current science indicates that the status quo is insufficient to provide a healthy riverine ecosystem. The river does not consistently meet swimming safety thresholds or goals around aquatic biomass content. With momentum towards removal currently building at the Talbot Mill Dam in Billerica, the only dam without fish passage downstream of the Assabet, the time may be right to spark a conversation about how beneficial dam removal can be for ecological connectivity and water quality.
As alternative solutions to these lingering issues on the Assabet are discussed, an emphasis should be placed on how to reach community members in a manner that allows them to engage with removal advocates in a respectful way that emphasizes local agency. Residents that abut the river are understandably most engaged, but any subsequent process should aim to create more awareness among the general public about the issues the Assabet faces, and how they are connected to these issues in the form of our sanitation networks. In the public
comment section of the 2010 report, one resident asserts that “ The current practice of discharging wastewater into the river is unsustainable and it must ultimately be stopped.” Alternative sewage treatments that are considered more sustainable do exist, but do not currently meet the needs of the community-scale shift that this resident seems to imagine. Until such methods can be scaled up appropriately, we must find progressive measures that work within existing sanitation frameworks. Perhaps the first step is to address the relative invisibility of our channelized rivers. The Assabet is technically visible from bridges that cross it, but is often so far below street level that it can barely be spotted from a car. Towns such as Hudson have invested in creating more opportunities
The Town of Hudson
for residents to connect with the river in recent years, such as the riverwalk that runs through a small portion of the town, featuring a playground and skate park. The legacy of industrial development along the river, however, leaves many views blocked by large industrial complexes and modern warehouses that face away from the water. More research is needed to understand how designers and planners can help reorient communities to their rivers, embracing them as assets, and creating new cultural and educational opportunities for local residents to interact with the water. This may assist river advocates create the public will to implement meaningful changes that stimulate greater ecological health and cultural connectivity for the Assabet.
Our Backs to the River
The town of Hudson faces away from its impoundment. Despite being so close to the water, the water is almost completely blocked from the main downtown corridor.
Dam
Town Hall
South St Rt
Commercial Corridor
Impoundment
Appendix
Historic, contemporary, and prospective depictions of the river
Page 26-27: Images of dam, impoundment, and commercial corridor of Hudson Pages 28-29: Collages showing impoundment views from the Hudson rotary
Pages 30-31: Diagramatic map and photography related to the Ben Smith Dam and Maynard Mill Ponds
Pages 32-40: Information pages for all dams on the Assabet River
Page 41: Images of downstream dams on the Concord and Merrimack Rivers
Pages 42-49: Existing (2007) and rendered conditions of all six dams studied in the 2010 Feasibility Report, showing potential impacts of dam removal
Cultural Use of the Impoundment
This archival image, courtesy of the Hudson Historical Society, depicts recreation on the Hudson Dam impoundment in the early 20th century. With the warming temperatures and fluxuations brought by climate change, the ability to use the dammed landscape for winter recreation is disappearing.
Downtown Hudson and the Hidden Dam
Despite its proximity to “The Rotary,” considered the commercial hub of downtown Hudson, the dam is not a prominent feature of the town. Its position well below the street level renders it invisible from a car driving down Washington Street. The Auto mechanic business further blocks the dam and impoundment from the well-used pedestrian corridors around the rotary.
Waterfront “Views” from Hudson’s Main Street Rotary Above, collages by the author show the limited visibility of Hudson’s mill pond, barely visible despite its proximity to the commercial hub.
The Ben Smith Dam
Removal of the Ben Smith Dam in Maynard is complicated by the canal and mill ponds in the center of town. The above map, taken from the 2010 feasibility report, shows how the current hydrology works. By lowering the water level through dam removal, water would no longer flow into the diversion channel to the ponds. Right, the lower mill pond and mill complex are shown. Below, the impoundment and accessible kayak launch at Ice House Landing offer a bucolic setting for recreation.
George H. Nichols Dam
Year Built: 1969, rebuilt in 2012
Height: 22ft
Length: 1,550ft
Storage Capacity: 6,500 acre-ft
Impoundment Name: George H. Nichols Reservoir/The Assabet Reservoir/A1 Impoundment
This dam was originally built to mitigate flood hazards in the upper watershed. The reservoir is considered to be the headwaters of the Assabet River. It has a surface area of 380 acres, a shoreline of 3.87 miles, and a total catchment area of approximately 7 square miles.
Aluminum City Dam (Also known as Sawmill Dam, Old Mill Pond Dam, and Rt. 20 Dam)
Year Built: 1925
Height: 7ft
Impoundment Area: 0.39 acres
Impoundment Name: Old Mill Pond
Impoundment Max Depth: 4ft
Estimated Extent of Dam Influence: 0.1 miles
Though the current structure is known to have been built in 1925, it’s been suggested that the building to the right of the above image was the original mill, and dates to the 19th century, suggesting that there may have been a dam structure in place here prior to that point.
No mention of this dam exists in the town historical records, so much is unknown about it. It’s been speculated that there was a sluiceway under what is currently the Aluminum City (a now-closed door supplier) structure, but this is unconfirmed.
There is no boat access or known use on the impoundment, and the surrounding land is used for commercial and residential uses
Allen Street Dam (Also known as Woodside Dam, Gothic Craft Dam, privately owned) Year Built: 1900
Structural Height: 12ft, Hydraulic Height: 8ft
Impoundment Area: 6.9 acres, Max Storage: 20 acre-ft
Estimated Average Depth: 1.5ft; Estimated Average Sediment Thickness: 4.5ft
Impoundment Name: Woodside Pond
Impoundment Max Depth: 8ft
Estimated Extent of Dam Influence: 0.6 miles
This district, known as Woodside Area, has been a mill site since 1720. The existing mill structure has been converted to condos, called “Residence at the Falls,” and sits just downstream of the dam. The dam itself is constructed of stone with a concrete layer on top, likely dating to 1900, when the mill was built. The dam is rated “Significant Hazard.”
Upstream of the dam, the Wachusett Aqueduct crosses the mill pond (right), adding further historic character to this neighborhood.
Tyler Flood Control Dam
Year Built: 1980
Hydraulic Height: 34.4ft
Length: 1,490ft
Impoundment Storage Capacity: 5,700 acre-ft
Impoundment Name: Assabet River
This damis an earth embankment with a silt core wall and was built to control flooding. It has a 275 foot long emergency spillway that discharacters to the Assabet River, located on the east side of the site. A June 1981 inspection report detailed sink holes that had developed and required remediation, and warned that a breach in the dam would result in numerous nearby homes and roads, including interstate Rt 290, to be inundated with 5-9 ft of water. Marlborough’s Westerly Waterwater Treatment facility discharges upstream of the dam (below, left). The upstream impoundment edge of the dam is below right.
Hudson Dam (Also known as Washington Street Dam, Rt. 85 Dam)
Year Built: 1956 (last repaired 1987)
Hydraulic Height: 9ft; Structure height 15ft
Impoundment Area: 21.9 acres
Impoundment Max Depth: 10ft
Estimated Extent of Dam Influence: 1.2 miles
The first dam recorded on this site dates to a grist mill from 1698, with the first bridge across the river being built the follwing year. A masonry dam was built in 1860 to support the many industries clustered around the dam. Oringally named “The Mills,” the hamlet became known as Feltonville by 1812, and became the separate town of Hudson in 1866. Hudson hosted at least five shoe factories and a show box factory, among other industries, which used power from this dam and another in town, which is on Danforth Creek, which is a tributary that meets the river downstream of the Hudson Dam.
Gleasondale Dam (privately owned)
Year Built: originally 1816, current structure built 1880/1924 - conflicting sources
Structural Height: 15ft; Hydraulic Height: 12ft
Length: 140ft
Impoundment Area: 13.6 acres, Max Storage: 124 acre-ft
Impoundment Name: Assabet River.
Impoundment Max Depth: 11ft
Estimated Extent of Dam Influence: 1.5 miles
This site has been dammed since 1750 and is responsible for the growth of this part of Stow. Sources conflict about when exactly the current structure was built. This privately-owned dam is inaccessible and there is no convenient portage route around it.
Ben Smith Dam
Year Built: 1870 (Original: 1847) to power woolen mill constructed by Amory Maynard
Structural Height: 9ft; Hydraulic Height: 6ft
Length: 170ft
Impoundment Area: 145.8 acres
Impoundment Name: Assabet River
Impoundment Max Depth: 11ft
Estimated Extent of Dam Influence: 5 miles
Creates the millpond in Maynard Town Center (right), a focal point of the town, and the impounment is well used by kayakers from the launch and public rental site at Ice House Landing (below)
Powdermill Dam
Year Built: Current structure built by Nathan Pratt in 1835 on site of early 1800s dam
Height: 19ft
Impoundment Area: 27.2 acres; Max Storage: 122 acre-ft
Impoundment Max Depth: 8ft
Estimated Extent of Dam Influence: 1 mile
This was the site for an expansive powder mill complex with buildings well spaced around the impoundment to avoid destruction when there was an inevitable explosion or fire. Henry David Thoreau mentioned hearing such explosions from Concord. The granite block dam is now used for hydropower generation, and is privately ownded.
Damonmill Dam
Year Built: early dam established 1658, later developed into large cotton and woolen
Height: N/A
Length: N/A
Impoundment Storage Capacity: N/A
Reclemated dam is now a swift water rock ramp. The dam site dates from a bog iron works established in 1658, and later a cotton and woolens mill operated by the Damon family through much of the 19th century. The mill complex was used as apple cold storage for several decades in the early 20th century and has now been redeveloped into an office complex. The historic mill channel through the complex can still be observed (below left).
