The St. Croix River has long been known for good water quality, but recent concerns from people within the watershed, as well as the IJC Commissioners’ request for the watershed boards review their water quality objectives every five years, have led to the creation of a subcommittee to explore trends, causes, and issues along its length.
The International St. Croix River Watershed Board formed a Water Quality Subcommittee in 2025. Its goal is to bring together the different groups within the basin to create a picture of conditions along the St. Croix River and determine what issues may exist.
Local residents near the mouth of the river have recently reported concerns about occasional events where they’re seeing discoloration, odor and foaming on the water, said Vincent Mercier, committee member and a scientist with Environment and Climate Change Canada’s (ECCC) Freshwater Quality Monitoring Division.
Additionally, a recently completed International Watershed Initiative (IWI) project undertaken by the board found that the nutrient nitrogen has been increasing over time at the river’s outflow, and that phosphorus, another nutrient, has been elevated at times.
Following the board’s public meeting in June 2025 at St. Stephen, New Brunswick, members agreed that these concerns warranted further investigation, which led to the appointment of the subcommittee. The subcommittee had its first meeting September 2026.
“In the 80s, the Pulp and Paper Mill and municipalities had very little wastewater treatment, and we went through a period where both countries started regulating wastewater treatment due to pollution leading to fish kills,” Mercier said. “Water quality got better for a while but lately changes to land usage in the watershed are becoming more prominent as potential sources of pollution.”
The subcommittee’s goals are to assess monitoring activities, concerns and information gaps and to assist the board in determining whether new binational water quality objectives should be developed, Mercier said. Their first meetings have been dedicated to sharing existing data, concerns, and activities between the different agencies and organizations collecting information.
The subcommittee has developed a project proposal to collate all the existing data to find any emerging patterns and gaps that require further investigation, Mercier said. It might also include recommendations for new water quality objectives for the river, which are goals that can be agreed upon by governments following recommendations from the IJC. These would be reported to the St. Croix board, which in turn can deliberate and share its own recommendations to the IJC for further discussion and submission to the federal governments. Currently, the board only has an outstanding objective for dissolved oxygen levels based on low oxygen events in the 1980s, he added. As this is a standing subcommittee, it is not subject to a specific timeline to report any findings.
The subcommittee is comprised of members from ECCC, The US Environmental Protection Agency, the US Geological Survey, Maine Department of Environmental Protection, New Brunswick Department of Environment and Local Government, the Passamaquoddy Nation Recognition Group, The Sipayik Environmental Department, and the St. Croix International Waterway Commission.
