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Friends of Casco Bay understands that some dredging is necessary to ensure the safe and efficient movement of ocean-going vessels­­. We advocate for dredging that has a minimal impact on marine life in the Bay and that properly disposes or reuses dredge material.

What is dredging?

Dredging is the removal of sediments and debris from the bottom of harbors and shipping lanes. It is a routine necessity in waterways around the world because sedimentation—the natural process of sand and silt washing downstream—gradually fills channels and harbors.

Working waterfronts have been essential to the history, economy, and character of Casco Bay. Over time, sediments carried by stormwater runoff settle in around the piers and wharves, and even in the shipping lanes farther from shore. Dredging these accumulated sediments is necessary to “keep the port in Portland Harbor” and to protect the health of our marine waters.

When sediments wash into the nearshore waters they can be polluted by substances that have been flushed from the air, the landscape, or pipes. The substances include household and industrial chemicals, raw sewage, pesticides, and fertilizers, which can be very toxic to marine life. These toxins can make extracting and disposing of these polluted sediments an extremely costly proposition.

Areas that are dredged more frequently tend to contain sediments that are less toxic than those areas that are dredged less frequently, and consequently, these dredge spoils can often be disposed of at sea. When sediments are found to be toxic to marine life, disposal at sea is not an option, and inland disposal is an order of magnitude more expensive.

Dredging in Casco Bay

Photograph by Kevin Morris • Aerial support provided by LightHawk

The Portland shipping channel in the Fore River is dredged to remain compliant with federal law. The US Army Corps of Engineers oversees and funds the dredges so that large vessels, including cruise ships, oil tankers, bulk cargo carriers and the Coast Guard, can safely navigate through the Harbor. Because this dredging happens on a routine basis, the sediments tend to be less contaminated than what is found around the commercial wharves, and the dredged materials are disposed of at sea at federal dredge disposal sites.

But a variety of smaller, private wharf owners around the Port of Portland have lost significant wharfage due to sedimentation. As Portland’s commercial piers fill in with mud, vessels may be grounded on sand bars that emerge at low tide. When the water around the wharves gets shallower, merchant vessels and fishing boats compete for ever fewer berths—or move to other ports.

For example, sediment in and around the wharves in Portland contain a legacy of pollutants from the City’s past and from still existing combined sewer overflows and stormwater runoff.

Even though the wharf owners do not own the submerged lands around their piers, they are responsible for maintaining them under the Submerged Lands Act. This maintenance includes bearing the costs of testing accumulated sediments for toxics and paying to dredge and relocate them. Testing the mud can cost thousands of dollars; the removal and relocation of contaminated sediments can run into hundreds of thousands of dollars.

Dredge spoils that contain toxic chemicals cannot be deposited at designated disposal sites at sea. Instead, they are generally shipped to approved landfills at a cost that can be ten times higher than at-sea disposal. Wharf owners cannot afford that option, so the mud continues to pile up.

What is Friends of Casco Bay doing to ensure safe dredging of our working waterfront?

Photograph by Kevin Morris

Friends of Casco Bay has long endorsed the removal of contaminated sediments from our waters.

Recently, waterfront business owners and officials from Portland and South Portland have begun considering a new option to deal with the contaminated sediments filling in their wharves: burying them in a deep, secure hole called a Confined Aquatic Disposal cell—or CAD cell for short. After sediments are deposited in the hole, it is capped with clean sediment.

CAD cells have been shown to keep polluted sediments out of circulation in other harbors. If done properly, a CAD cell could be an ecological and economical solution to the legacy of pollution at the bottom of our harbor.

A working group of Portland officials and waterfront business owners is exploring the feasibility of locating a CAD cell in Casco Bay. They have identified a possible CAD cell site near the Coast Guard station on the South Portland side of the harbor. Friends of Casco Bay is monitoring this effort closely.

To stay informed about the Portland Harbor Dredging project, go to  www.portlandharbordredge.info.

What you can do. . .

  • Sign up for our emails so you can stay informed about this issue.
  • Support our Baykeeping Program with a donation.
  • Support your town’s work to reduce combined sewer overflows and build green infrastructure to reduce stormwater pollution.
  • Keep pollutants, such as pesticides, fertilizers, and household chemicals, out of the Bay. Check out our BayScaping Program for tips.
  • If you see a construction site without a silt barrier—plastic fencing along the downslope side of the site—report it to your town’s Code Enforcement Officer or Public Works Department. Oftentimes, a little education on proper construction methods can ensure that the dirt stays in place.
  • Prevent erosion from your property, so that less silting along the waterfront will occur:
    • Fill in bare spots in the lawn with grass seed and mulch to hold soil in place.
    • Plant a buffer strip of bushes and trees along the edge of your yard.
    • Construct a rain garden of water-loving plants or a grassy swale to hold stormwater runoff and soil in a heavy rain.

Cover photo: Photograph by Kevin Morris

Read more about our Baykeeping work:

Friends of Casco Bay Testimony in Opposition to LD 1853: An Act To Ensure the Safe and Consistent Regulation of Pesticides throughout the State by Providing Exemptions to Municipal Ordinances That Regulate Pesticides

March 19, 2018

March 21, 2018 Senator Paul Davis Representative Danny Martin State and Local Government Committee c/o Legislative Information Office 100 State House Station Augusta, ME 04333 Re: Friends of Casco Bay Testimony in Opposition to LD 1853: An Act To Ensure the Safe and Consistent Regulation of Pesticides throughout the State… Read more

Ivy Frignoca, Casco Baykeeper

Opposing the 2019-2024 Draft Proposed National Oil and Gas Leasing Program

February 26, 2018

Ms. Kelly Hammerle, Chief National Oil and Gas Leasing Program Development and Coordination Branch Leasing Division, Office of Strategic Resources, Bureau of Ocean Energy Management (BOEM) 45600 Woodland Road Sterling, VA 20166-9216 February 26, 2018 Re: Docket ID: BOEM-2017-0074: Comments opposing the 2019-2024 Draft Proposed National Oil and Gas Leasing… Read more

Cathy Ramsdell Interview

Protecting the Bay from Pesticides

February 6, 2018

We are delighted to share that in January 2018, the City of Portland passed one of the strongest ordinances in the state to restrict pesticide use. Executive Director Cathy Ramsdell served for nearly a year on a task force to help the city develop the ordinance. She often found herself… Read more

Support of LD 1657: An Act To Update the Allowance Budget for the Regional Greenhouse Gas Initiative

January 10, 2018

January 10, 2018 Senator Thomas Saviello Representative Ralph Tucker Environment and Natural Resources Committee c/o Legislative Information Office 100 State House Station Augusta, ME 04333 Re: Friends of Casco Bay Comments in Support of LD 1657: An Act To Update the Allowance Budget for the Regional Greenhouse Gas Initiative Dear… Read more

After a rainstorm, millions of gallons of polluted stormwater pour into Casco Bay.

Support of LD 178: An Act To Authorize a General Fund Bond Issue To Provide Jobs, Improve Road Infrastructure and Protect Water Resources

January 9, 2018

January 9, 2018 Senator James Hamper Representative Drew Gattine Committee on Appropriations and Financial Affairs c/o Office of Fiscal and Program Review 5 State House Station Augusta, ME 04333 Re: Friends of Casco Bay Testimony in Support of LD 178: An Act To Authorize a General Fund Bond Issue To… Read more

Ivy Frignoca, Casco Baykeeper

Support of LD 1510: An Act To Authorize a General Fund Bond Issue to Fund Wastewater Infrastructure Projects for Ratification by Voters

January 9, 2018

In many instances, the improvements needed to wastewater treatment facilities cost more than municipal taxpayers can bear. State and federal funds have traditionally supplemented and must continue to supplement municipal budgets to improve and protect water quality in compliance with the Clean Water Act. Read more