During the 1980s and the 1990s, the Bare Hill Pond Watershed Management Committee, as well as the state, conducted a series of studies, cited in Harvard’s Open Space and Recreation Plan, to consider how best to address the infestation and growth of invasive aquatic species and to protect the health of Bare Hill Pond. In 1999 the Massachusetts Department of Environmental Protection (DEP) concluded that Bare Hill Pond was endangered, due to excessive levels of phosphorous and invasive plants in the pond. This determination made the town eligible for federal grant funding, administered through the DEP, and prompted the Pond Committee to develop a remediation strategy.
As part of that strategy, projects were initiated to harvest invasive plants and to implement seasonal drawdowns to deter their regrowth. Now the Pond Committee is embarking on the next phase of remediation plans: controlling non-point-source pollutants running into the pond (e.g., phosphorous, salt, road chemicals) and removing phosphorous from the pond bottom itself through excavation of peat from shoreline areas during the winter drawdown.
History of treatments for an endangered pond
As noted in all the reports from the DEP, the pond was at high risk of eutrophication, the process by which a pond becomes a marsh. Plant growth accelerates, oxygen levels decline, algae blooms become more frequent, and invertebrate populations (and their predator fish) are put at serious risk. Eventually, the pond fills with peat moss and marsh grasses. In an undisturbed watershed, this can take 1,000 years. In a high phosphorous pond, it can accelerate 10-fold.
During the 1990s, control of plant growth was limited to the hand-pulling of water chestnuts and the use of a harvester, due to divisive local debate about whether or not herbicides should be used. Though not a cure, these methods were treatments, much like mowing the lawn. Unfortunately, the harvesting that provided temporary relief also had the unintended side effect of spreading the infestation, because milfoil and fanwort spread by cuttings. By 2001, the acceleration in the growth of the invasive species caused the Pond Committee to adopt a new course and find common ground for action rather than focus on the herbicide debate: drawdowns.
Drawdowns and beyond
Initially, these were conducted using gravity releases at the dam in 2001–2005, which had a maximum potential drawdown depth of 3.5 feet. This enabled us to test the methodology, monitor the results in the drawdown zone, and develop data to support deeper drawdowns, if needed.
The initial gravity drawdowns indicated efficacy in the drawdown zone, but limited impact, if any, beyond 3.5 feet in depth. With this data, the committee developed a plan for a pumping station, applied for a Section 319 grant and supplemental CPC funding, and then built—with volunteer design, engineering, and construction efforts—the pump station.
The project included a requirement for the committee to prepare a long-term watershed management plan, a document that would outline the short-term, medium-term and long-term practices that would achieve three key goals: (a) control the invasive aquatic species in the pond, (b) reduce the level of phosphorous in the pond, and (c) implement best practices in the watershed to protect the pond and the health of its watershed.
The first project lasted three years, resulting in a pumping station that has enabled deep drawdowns of up to six or more feet, significant reductions in invasive species in many areas of the pond, and the opportunity to continue to address the pond’s eutrophication with additional remedial measures.
A key finding of the watershed management plan was that the sources of phosphorous that drive eutrophication and invasive species growth needed to be controlled over the long term to address this problem at its source. This helped the committee to identify medium- and longer-term plans.
Storm water treatment
The Pond Committee applied for additional grant funding and this year initiated a project to excavate peat from the pond’s shoreline during the winter drawdown and to begin storm water treatment activity, which will focus on road runoff in the town center area and will use bioremediation plant gardens. The peat removal effort is being managed by Harvard’s Department of Public Works, which is developing a plan for selling the resulting organic material. This could become a self-funded activity in future years.
The support of the state and the Environmental Protection Agency for these activities has allowed the Pond Committee to proceed without seeking additional operating funds from the town’s constrained budget. Projects have relied very heavily on volunteers―a key part of the strategy, which pays significant dividends because volunteer efforts qualify toward meeting local matching requirements under the grants at the rate of $20 per hour. The state permits the committee to design projects so that watershed management activities count as matching time.
The outlook for water chestnuts
Another activity that is critical to the pond is removing the invasive water chestnut species in Clapps Brook area of the pond. Unlike milfoil and fanwort, water chestnuts are seed-bearing and are not controlled by drawdowns. They are also not spread by the harvester. This is where harvesting activities have been focused during the past two years. As a result, the number of plants has been reduced by 75 percent and, at this rate, might be eliminated altogether in the next several years.
Plans for education
Longer term, the Pond Committee will also focus on providing watershed educational opportunities and engaging directly with watershed residents. Development in the watershed can play an important role in protecting the pond. Planting native species to prevent runoff on the pond’s shores, avoiding the use of fertilizers, and protecting the ecosystem will help reduce invasive species growth and further slow eutrophication. Experience has shown that education and information can make a big difference and contribute to the health of the watershed.
Toward this end, the Pond Committee will host a public forum Thursday, March, 18, at 7:00 p.m. in Volunteers Hall, for a discussion of the Watershed Management Plan, with focus on the Storm Water Treatment Project.
For more information about the Pond Committee’s Watershed Management Plan, visit www.harvardpress.com/AboutHarvard/HarvardWiki/tabid/1636/Default.aspx?topic=Harvard+By+Design
