A New Chapter for Chilmark Pond: Dredging Begins!

Dredging in the Lower Chilmark Pond. Photo courtesy of Ollie Becker.

The Long-Awaited Day Has Arrived:

After five years of persistent advocacy and fortitude in a very challenging permitting climate, CPF’s hard work has finally paid off and dredging in the Chilmark Lower Pond has officially begun. This dredging and beach nourishment work is a big step toward restoring the long-term health and resilience of Chilmark Pond.

A Long Journey to Get Here:

This multi-year effort to secure permissions to dredge required tenacity and collaboration. The entire CPF Board has been focused on making sure that this project came to fruition, and they would like to express their gratitude to the Town of Chilmark and members of the pond community who have been essential partners.

Let us all recognize Amy Salzman whose expertise, persistence, and leadership were indispensable and guided this effort over the finish line. Amy’s commitment to Chilmark Pond made this possible. Thank you, Amy!

Evening dredging on Chilmark Lower Pond. Photo courtesy of Ollie Becker.

Why Dredging Matters:

Monitoring over the past several years has shown that the accumulation of sand has resulted in shorter cut duration, reduced water exchange, and limited flushing capacity. These impacts were evident in a recent Chilmark Pond cut on March 2, which lasted only four days. The pond was opened again on April 24^th. This was a good opening with considerable tidal exchange according to the elevation logger. The pond closed on May 5^th. This was likely the best recent opening. This results in reduced flushing of the pond with clean (salty, clear, low-nutrient) seawater, increased nutrient (nitrogen and phosphorus) build-up, and continued ecological stress.

Over time, sand builds up in the pond as the result of the ocean’s action moving sand with the tides and closing the breach. This was particularly dramatic in the winter of 2023-24 when there were a series of extraordinarily powerful nor’easters that caused waves to wash over the dunes, driving much of their sand into the pond. This causes more sand coming into the pond than being pushed out, shallowing the pond and creating a delta near the opening that restricts the flow of water in and out of the pond, reducing the flushing capacity of each pond opening or “cut”, making them shorter and less beneficial to the pond’s ecological health.

Aerial view of dredging in the Lower Chilmark. Photo courtesy of Ollie Becker.

The current dredging project is designed to create two channels near the cut, removing this sand buildup which will allow cuts to better drain the pond and promote healthy tidal exchange of pond and ocean water. Cuts are an effective and efficient management tool:

1)      To flush out excess nitrogen and phosphorus,

2)      To increase the salinity pond-wide,

3)      To lower the elevation of the pond to avoid flooding

4)      To allow for the exchange of biological organisms, and

5)      During the summer, cuts help lower the pond’s temperature

How do we know that dredging improves pond health? Example of Success:

Dredging is a proven and effective tool to increase the benefits of openings and, in turn, pond health. The Massachusetts Estuaries Project recommends specifically improving the health of Chilmark Pond by achieving longer and more effective openings.

Read the whole 2015 MEP Report 

An example of this was seen at Edgartown Great Pond. After a decade of dredging (2009 – 2019) Edgartown Great Pond:

·         Improved In Water Quality

·         Increase in Eelgrass Meadows

·         Increased Shellfish Populations

Looking Ahead:

With dredging now underway, we are entering a new and hopeful chapter for Chilmark Pond. This work lays the foundation for longer cuts, improved water exchange, and a healthier and more resilient ecosystem in the years to come. We will continue to monitor the pond closely and share updates as the project progresses.