Essay : Mill Pond's future needs careful judgment by West Tisbury voters
There has been a lot of discussion and information lately about West Tisbury's Mill Pond. What to do about it, whether to dredge the pond and/or create a wetland at its headwaters, or even to remove the dam and allow it to become a stream running through wetlands and maybe a forest eventually. It is important, while the town studies this issue and then votes how to proceed, that voters get the full story.
Voters agreed to spend up to $25,000 to have engineers study the pond and make recommendations as to how to best preserve and manage the pond. Carl Nielson, of ESS Engineering, presented his company's recommendations in a presentation at the Howes House on January 18. The presentation was videotaped by MVTV, and we will ask that it be replayed in the weeks before the annual town meeting. The final report is also available at the town hall.
In short, Mr. Nielson reported that the best way to preserve the pond, which is in an advanced state of eutrophication (meaning it has lots of rich sediment which encourages growth of vegetation, algae mats etc.), would be to dredge the pond, "resetting" its environment, which would cost the town about $200,000. He offered an alternative, which would double the cost, but could be eligible for federal and state grant funding, and which would require 40 percent in-kind matching funds by the town, that can be met in a number of ways other than actual cash commitments (e.g. volunteer time by the Mill Pond Committee, the town highway department, or town officials), possibly costing the town little to nothing beyond what we have already spent.
That alternative would be to create a serpentine shaped pollutant trapping wetland system at the top half of the pond in addition to dredging and making the other part of the pond deeper. A deeper, cooler part of the pond would be more hospitable to fish and add a diverse wildlife habitat. The created wetland would trap a lot of the sedimentation that collects in the pond. Some additional maintenance would need to occur, possibly every five years or so, to remove accumulated sediment at the head of the pond, but would not be a huge undertaking. In order to receive grant funding, the town would be required to institute some best management practices, such as improving the road runoff situation into the Mill Brook and pond and addressing other watershed issues.
The Mill Pond Committee has voted 6-1 to ask the town if we may engage Mr. Nielson's company to assist us, at no cost to the town, in the application for funding for the dredging and wetland creation alternative. An article on the annual town meeting warrant asks for this permission.
Meanwhile, Prudy Burt, a member of the town conservation commission, but on her own initiative, has asked two speakers to come and discuss the merits of dam removal. She also asked the Massachusetts Division of Ecological Restoration at the Department of Fish and Game to do a "Site Reconnaissance, Preliminary Evaluation and Opinion of Probable Cost for Dam Removal at the Old Mill Pond Dam in West Tisbury", which they did in June 2011, at no cost to the Town. The report discusses some of the issues that would need to be addressed if the town wishes to remove the dam, namely, ensuring flow to Factory Brook, which feeds Maley's Pond, a firefighting water supply source. It also discusses the possible need to build another bridge or culvert at the old dam's outlet on the Edgartown-West Tisbury Road. The estimated cost for this project, though there also are some funds available to help, was $568,000. The report is available at town hall.
We have some evidence from Bill Wilcox's Mill Brook 2010 Water Quality Assessment that ponds appear to act as nutrient sinks, filtering out some of the phosphorus and other chemicals that would otherwise flow into the Tisbury Great Pond and the sea beyond. This ecological benefit appears to me to be an even more important reason to preserve and maintain the Mill Pond, beyond our mere love of its beauty, its historical significance as part of the historic district and our promise, when the town voted to accept ownership of the pond in 1949, to maintain it.
Although the Mill Brook, or river, as it was sometimes referred to, flowed freely before human beings began living near it, damming up several ponds on it, and polluting it with road and agricultural runoff and other pollutants, we need to consider its current state and determine whether maintaining a deeper pond, with created wetland to help filter out harmful chemicals, is a more ecological answer at this time.
I trust the voters of West Tisbury will study this complex issue carefully and make an informed decision about the fate of the Mill Pond. Please continue to read, listen, and think through the implications for ourselves and future generations. See you at the annual town meeting on April 10.
Anna Alley is a member of West Tisbury's Mill Pond Committee.