What is the CPA?

Chapter 203 of the Acts and Resolves of Massachusetts in 1904 provided for the drainage of the lowlands and meadows around certain Great Ponds in the County of Dukes County, including Chilmark Pond. Specifically, the Acts authorize the proprietors of lowlands and meadows around Chilmark Pond to form an association and elect three Commissioners to “do whatever is necessary to properly drain the pond,” a tax collector to cover the costs thereof, and a Clerk. The CPA bylaws establish the following officers: President, Vice-President, clerk, Treasurer/Collector.  All of these positions are filled by volunteers who are elected annually.

What does the CPA do?

The 1904 law mandates the Commissioners “to do or cause to be done whatever may be necessary to properly drain the low lands and meadows around . . . [Chilmark] pond.” The 1904 law also authorizes the CPA to assess the proprietors for the expense of drainage, granting it the powers and manner provided for the collection of town taxes. The CPA bylaws expressly add the purpose of carrying on a fishery.

What is the current annual tax assessment?

$150

Why do we drain the pond?

The Pond has been opened to the Atlantic Ocean for hundreds if not thousands of years. The Wampanoag people started the practice to allow anadromous fish to spawn and maintain the shellfishery. Since the 1600s, Chilmarkers have continued this practice to maintain the fishery (as recently as the 1960s the Pond was a commercial fishery) and to harvest pond hay for animal feed. Nowadays, we open the Pond to improve its ecological health and to control flooding of the surrounding marshes and homes. According to the Massachusetts Estuaries Project and other experts, opening the Pond is the best way to flush out pollutants, increase salinity for fish and shellfish habitat and protect the surrounding marshes.

How often is the pond drained?

It varies, but in recent years 4-6 times per year.

Who decides when to drain the Pond?

The three elected Commissioners are charged deciding whether and when to open the Pond to the ocean. They regularly monitor the Pond conditions at various locations and consult extensively prior to making their decision. The Commissioners base their decision on the factors described below.

What factors determine when to drain the Pond?

Deciding when conditions are right for a Pond opening is based on science, current and forecasted weather conditions and past experience. Often Chilmark Pond and Tisbury Great Pond are often opened at about the same time because conditions tend to be similar and the Commissioners from both Ponds often consult.

Key factors in determining whether to open the Pond are:

• Pond depth. Sufficient hydrostatic pressure is necessary for the pond to drain into the ocean.

• Protecting the marshes. Marshes play an important role in the Pond’s health and water management. They should be protected from high water inundation.

• The tides and phase of the moon. The more extreme tides at full and new phases of the moon provide better likelihood that the pond will drain and be flushed out with cool, saline ocean water.

• Storms and wind. Storms can push sand back into the Pond, closing it before it gets a good drain and flush. Storms can also make it perilous for the contractor to open the pond.

• Protected species: between April 1 and August 31 we coordinate activity at the cut with BiodiversityWorks to ensure no harm to protected species. From the time protected chicks hatch until they fledge there are strict limits on disturbing them.

• Availability of the contractor to perform the work.

How is the Pond opened?

We contract with a trained operator who uses an excavator to dig a trench approximately 10 feet wide from the Pond to the ocean.  Nature takes it from there.

How long does the Pond stay open?

On average an opening lasts about two weeks. Once the Pond is opened, nature is in control. We have had openings that have lasted many weeks while sometimes it closes in just a day or two.

What is considered a good length of time for an opening?

We have been advised that two weeks allows for a healthy drain and flush with saltwater.

Why has the Pond become shallower in recent years?

Wind and ocean activity blow and push more sand into the Pond than is released when the Pond is opened.  Big storms like Superstorm Sandy and Nor’easters bring a considerable amount of sand through wash-overs into the Pond. In recent years we have been prevented from reducing shoals that forms at the mouth of the cut and the Pond has become very shallow. This means that it can hold less water without inundating the surrounding marshes. It also means that cuts may be less effective and predictable.

What fills the Pond? 

The Pond is part of a large watershed and is fed by direct rainfall, surface water including two brooks, subsurface groundwater and surface and subsurface ocean water.

Are there any rules about using the Pond?

The Town of Chilmark limits internal combustion boat engines to 5 horsepower on Chilmark Pond. Due to the fragility of its ecosystem, in 1982, the CPA voted to ban internal combustion engines on the Middle and Upper Ponds. In 2022, the CPA voted to phase out the use of internal combustion engines throughout the Pond effective in 2025.

What is the Chilmark Pond Foundation?

The Chilmark Pond Foundation is a community-centric organization established to support the science-based restoration of Chilmark Pond’s ecological health and protect it for future generations. The CPF is a 501(c)(3) charitable organization that has launched several programs including a cyanobacteria monitoring program that is part of MVCyano, a dredging program and an ecosystem monitoring program. The CPF works closely with the CPA.

What can I do to help?

• Get involved.

• Stop using nitrogen and phosphorus fertilizers and household products (whether organic or not).

• Protect the marshes and pond edge that help prevent erosion and also naturally purify surface water. Remove boats carefully so the vegetation at the Pond edge isn’t damaged.

• Have your septic checked to make sure it’s functioning and consider upgrading it to reduce nitrogen.