West Tisbury will take another look at Mill Pond options

The notion of dredging Mill Pond in West Tisbury, the historic and scenic pond next to the town police station, has been discussed and debated extensively in recent years. Many believe that the pond should be dredged to prevent it from drying up.

Still others believe the pond can be maintained by simpler and less costly measures such as removing weeds. In 2008, selectmen agreed to appoint a special Mill Pond Committee to tackle the question of just what to do with the pond.

Since that time, a majority of the Mill Pond committee has consistently endorsed the dredge option, and has brought several articles to the floor of town meeting to seek funding to dredge out the 2.5-acre pond.

At the 2012 annual town meeting, voters approved an article authorizing the town to seek grant money for dredging Mill Pond, but added an amendment requiring any such projects to come back to town meeting for final approval.

But a new option has emerged in recent months so simple that it may seem radical to some: remove the dam and allow the Mill Pond and Mill Brook to return to its natural state, as it was before the arrival of English colonists.

Those who support this option believe removing the dam would create a free-flowing stream, unimpeded by dams, capable of supporting populations of native species like brook trout, white perch, herring, and American eels.

The future of Mill Pond and Mill Brook will be the topic of an informational meeting on Wednesday, January 30, at 5 pm at the Howes House. Various management options, including dam removal, will be discussed.

Stream restoration experts from the Massachusetts Division of Ecological Restoration and the Nature Conservancy will attend the meeting and be available to answer questions. All are invited to attend.

Dredge or dam removal

In a report dated November 28, Brad Chase of the Diadromous Fish Biology Management Project of Mass. Division of Marine Fisheries summarized the findings of a series of site visits to Mill Pond, Mill Brook, and the Tiasquam River.

The Tiasquam River also flows into Tisbury Great Pond, at a point less than half a mile southwest of Mill Brook’s outflow.

Mr. Chase and his staff inspected the site for diadromous fish (fish that migrate between the sea and fresh water) restoration potential. The report finds that Mill Pond is “quite shallow” with an average depth of less than two feet and a maximum depth of seven found upstream at two spillways.

The report concludes that the presence of diadromous fish in the Mill Brook watershed is known but not well documented. “More recent observations indicate the watershed had valued sea-run fisheries for rainbow smelt, white perch, America eel and river herring,” Mr. Chase wrote.

The report states that Mill Brook has not been viewed by past Marine Fisheries surveys as having potential for river herring restorations due to the number of mill dams and limited spawning and habitat in Tisbury Great Pond.

But the report states that interest in habitat restoration has increased in recent years, and a study commissioned by the town of Mill Pond in 2006 provided valuable information on physical features, water quality and aquatic resources.

“At present, the interest in habitat restoration in Mill Pond involves aspects of diadromous fish restoration, pond dredging and dam removal with no clear local consensus on the preferred approach,” Mr. Chase said.

Improved natural stream connectivity

Mr. Chase said that during all five site visits to Mill Brook, flows exiting Mill Pond were sufficient to provide enough water depth to the brook channel downstream of the dam to allow river herring to approach the spillway.

During an April 19, 2011 site visit, Mass Fisheries officials found river herring scales downstream from the Mill Pond dam, and a single American eel. Water chemistry was measured and found to be suitable to support river herring.

The report makes several recommendations but stops short of suggesting that the Mill Pond dam be removed to allow the brook to return to its natural state.

Mr. Chase concludes that any restoration efforts be related to broader watershed goals of the towns and property owners. He said the Marine Fisheries staff is available to provide materials and labor to replace the existing fish ladder at Mill Pond Dam with a properly designed, wood fishway.

A fish ladder is a structure on or an around artificial barrier that enables diadromous fish to continue upstream by swimming or leaping up a series of low steps.

Mr. Chase said Marine Fisheries also supports efforts to investigate improved fish passage and dam removal at Mill Pond Dam.

“Restoration that improves natural stream connectivity is preferred by Marine Fisheries for this location,” he wrote. “However more information is needed to select the preferred approach given the range of existing resource uses and interests. We recommend that the feasibility studies continue for this topic.”

Mr. Chase also recommends the town coordinate with the private owner of Looks Pond Dam about making fish passage improvements, and also recommends that a dam at Rainbow Farm could be removed with benefits to several diadromous species, independent of upstream improvements.