Contributed by Joe Stewart

This is the first in a three-part series about Wrentham’s dams.

Many people might not be aware there’s a push to remove dams across the state, and even across the country. Unless, of course, they live on or near a body of water formed by a dam. One such dam in the state’s crosshairs is Wrentham’s aging Eagle Dam, which forms the oasis known as Eagle Pond. 

Eagle Pond connects to the northeast corner of Lake Pearl, and to Eagle Brook, which winds through Norfolk and the Charles River watershed. Eagle Dam, which was last rebuilt in 1968, dates back to at least the 1800s.

Environmental activists, and in particular the Charles River Watershed Association (CRWA), contend that most dams have outlived their original purpose and should be removed to restore a river’s natural flow and increase biodiversity by reconnecting river habitats. Other research, however, asserts that dams help protect the environment by capturing sediment that could contain harmful substances. And then, of course, there’s the quality-of-life issue for abutters and other residents who enjoy the lakes and ponds formed by dams. 

But in the eyes of the state, Eagle Dam is a failing dam. For years, both Wrentham and the Massachusetts Department of Dams have been aware of its deteriorating condition and the risks that a failure pose. In particular, the high traffic corridor between Wrentham and Franklin, Franklin Street (state Route 140), is immediately downstream from the dam. The culvert through which Eagle Brook flows also supports water and gas mains--more than 40% of Wrentham’s water flows through the water main. 

Brian Anatoli, Wrentham’s director of public works, noted that if a substantial breach of the dam were to take place, a potential outcome could be the immediate closure of Route 140 until the water receded and the roadway was repaired.  Addi tionally, homes in Wrentham and Norfolk downstream from Eagle Dam along Eagle Brook might experience flooding, depending upon property elevations. 

Both outcomes would impose significant costs on many:  emergency repairs to the highway and culvert, emergency repairs to the water and gas mains, emergency repairs to homes and property, much of which is unlikely to be covered by homeowners’ insurance.

The town of Wrentham is responsible for Eagle Dam. Along with the DPW, the town must periodically inspect the dam and perform ongoing maintenance. The Commonwealth provides guidance and oversight and, in some cases, partial funding to offset the significant capital costs relating to public infrastructure. State funding, however, prioritizes the largest dams at the greatest risk. Eagle Dam, despite its problems, has been deemed a “low hazard” dam by the state.

What do the experts say?

Over the years, Wrentham has tapped multiple experts to provide advice on how to address Eagle Dam. They include Pare Corporation, an engineering and planning services firm with expertise in wetlands, streams, and dams; Weston and Sampson, an engineering consulting firm with deep expertise in public water supply (e.g., wells, water mains, storage, and distribution systems); the Charles River Watershed Association, which has developed modeling and simulation applications; and ESS Group, a water resource management consultancy now owned by TRC Companies.

Likewise, residents living near Eagle Dam have hired Creative Land and Water Engineering (CLAWE), an engineering consultancy providing expertise in hydrology and hydraulics, and in hydrogeology particularly in wetlands, rivers, and wildlife habitats.

In 2012, Pare Corporation performed a dam inspection and rated Eagle Dam as a low hazard dam in poor condition. In its report, Pare recommended that Wrentham either breach or repair the dam and noted that breaching the dam would provide an opportunity to restore more natural stream conditions.

More recently, the town hired ESS Group to conduct a technical feasibility study focused on removing the dam and they delivered their report in April 2021. ESS concluded that there were no major technical barriers to dam breaching or removal and recommended that planning begin immediately, highlighting that the dam’s deteriorating condition might lead to enforcement actions and specifically noting that continuing to do nothing was not a responsible option.

Similarly, the Charles River Watershed Association was hired to provide consulting around Eagle Dam options in part due to their extensive computer modeling of the Charles River watershed.   And Weston and Sampson was hired to provide expert advice and project oversight across projects including town water supply (repair and replacement of Town Well #3 and exploration of potential well sites in West Wrentham) and evaluation of Eagle Dam options. 

What are the options and the associated costs?

According to Anatoli, Wrentham’s DPW head, there are really only two options in regard to Eagle Dam, despite its “low-hazard” designation: repair or breach. Although the town could continue to defer action, Anatoli notes that the risk of failure will only increase as will Wrentham’s liability.  

Repairing the dam is the most intensive option, said Anatoli, requiring removal of the trees and all other vegetation on and in the dam wall and spillway, as well as rebuilding the spillway and the dam wall itself.  Breaching is less intensive, requiring controlled water release, breaching of the dam wall, and then restoration of the habitat.

Cost estimates provided to the town have ranged from $680K to breach the dam, to as high as $2 million to repair it. 

Repairing the dam would likely change the landscape in the area, asserts Robert Kearns of the CRWA. Most of the trees and vegetation in and on the dam will be removed, along with the trees that currently obscure Eagle Dam from Route 140. Kearns said the area around the dam would look much like Red Dam, the dam forming Lake Pearl:  a sparse earthen mound.

What’s the impact on the town wells?

Town Wells 2 and 3 (and the new Well 3 which will replace the existing Well 3) are sited near Eagle Dam and today provide 40% of Wrentham’s water.  In an analysis performed by CLAWE, the group hired by abutters to the pond, they noted that the pond formed by Eagle Dam provides 8 feet of surface water that supports production from Well 3 (both the existing and new wells) and enhances the drought tolerance of Well 2. Those 8 feet of surface water effectively form a 19-million-gallon storage tank that helps recharge the ground water from which Wells 2 and 3 draw.  

Weston and Sampson noted that there is not a 1:1 ratio between surface water level and aquafer capacity owing to permeability of the soils among other factors, but there is agreement that the pond serves as a buffer; it’s more a matter of the degree to which the Eagle Pond protects well capacity and at what cost for that protection.

What are the environmental impacts of repairing or removing the dam? 

The Commonwealth has designated Eagle Pond and surrounding areas as a priority habitat site to protect threatened species, including a small freshwater minnow, the bridle shiner.  CLAWE noted that this priority habitat includes half a dozen identified vernal pools, at least one of which would likely drain if the dam were to be breached or removed, although new vernal pools could form in the remaining water depressions. Vernal pools serve as essential breeding habitats for amphibians such as salamanders, a federally designated threatened species. In Massachusetts, vernal pools are technically protected under the Massachusetts Wetlands Protection Act, if they meet the definition of “wetlands” under the law.

As noted, potential flooding of the area if Eagle Dam breaches is just one of the reasons some experts point to removal. However, recent analysis disputes that claim. CRWA and Weston & Sampson conducted computer modeling using CRWA’s Charles River Flood Model, which models 190 river-miles including 108 dams and 450 bridges/culverts. Andrew Walker, the Weston & Sampson hydrologist who worked on the analysis, said after updating the model with measurements from Eagle Dam and Eagle Brook, they performed a total of 20 simulations of 24-hour storms using two climate models and two conditions: Eagle Dam repaired and Eagle Dam removed. 

The analysis focused on flooding impacts for 4 miles, from Lake Pearl to Main Street in Norfolk.  And the outcome of the analysis?  Less than 1/3 of an inch difference between keeping the dam and removing it, including no increases in flooding risks for any residences near Eagle Brook. Walker did note that consultation is underway with MassDOT to review their findings as they relate to the bridge at Franklin Street.

What about the abutters and other residents who use Eagle Pond?

Residents on or near Eagle Pond, and visitors to the pond to fish, highlight the pond’s tranquility and stunning wildlife. A recent visit to the pond resulted in several bald eagle and heron sightings. Bob Pellet, an abutter, noted that for more than 30 years the pond has provided a safe and secure habitat for a variety of fish, birds, and wildlife.

A nearby resident, Joel D’Errico, has become a vocal critic of the state’s drive to remove dams, especially Eagle Dam, noting quality of life for residents and visitors should be taken into account before any decision is made. Eagle Pond, he says, will be reduced to a slow-moving, small stream if the dam is removed. He takes issue with the CRWA’s assertion that dams harm the health of the Charles River and the animals and plants that rely on it. Dams, according to the CRWA, impact water quality, impede fish passage and encourage the growth of invasive species.

“Why do some fish have priority over other fish, or over herons and bald eagles?” asked D’Errico. “There’s trout and pickerel in Eagle Pond, supper for the herons and bald eagles. Isn’t this all part of the ecosystem too? The dam has been here for hundreds of years.”

Both D’Errico and Pellet expressed frustration with town officials, noting that grant money is available to repair Eagle Dam through the Dam and Seawall Repair Grant Program. However, William Hinkley from the Commonwealth’s Executive Office of Energy and Environmental Affairs pointed out that the grant program prioritizes “high hazard” or “significant hazard” dams in poor or unsafe conditions.

How can residents learn more about the Eagle Dam issue?

The DPW’s Anatoli noted that the town needs to come to a decision soon on what to do in regard to Eagle Dam: repair, breach, or defer a decision. Costs are escalating and the dam will continue to deteriorate. Residents should make their voices heard now.

To educate residents and to learn their thoughts, the town has sponsored a series of walks at Eagle Dam. The town has also conducted several Zoom conferences (May 1 conference available at https://youtu.be/ePuGz216XY8) and has surveyed residents through an online survey (survey available at bit.ly/eagledam).  

For more information about the town’s efforts, visit Wrentham.gov and search for Eagle Dam.