What is being done about sewer overflows in the Merrimack River (CSOs)?
Sewer overflows in the Merrimack River are a regional issue affecting multiple communities.
Cause of CSOs:
Since the late 1970s, sewage treatment plants have been required to process all the sewage generated on a typical dry day. However, during rainstorms, the volume of water entering these plants from cities like Manchester NH, Lowell, Lawrence, and Haverhill overwhelms their capacity, resulting in excess flow being discharged into the river. Newburyport does not contribute to this overflow.
Health and Environmental Impact:
CSOs can contain high levels of harmful bacteria, leading to rashes, infections, and intestinal problems for people and animals. They can also harm fish by reducing oxygen levels in the water. The Massachusetts Department of Public Health advises avoiding direct contact with river water for 48 hours after a CSO event. Residents can subscribe to Health Department alerts for updates on CSO events and other public health notifications at this link.
Local Testing and Notifications:
The Newburyport Health Department conducts weekly water testing during the summer season at Plum Island Point Beach. If water quality is found to be unsafe for swimming, the Health Department, in conjunction with the Harbormaster Department, will post signs at public beach entrances and parking lots to notify beachgoers. Testing will continue until the water is deemed safe. More information on beach testing can be found here.
Regional Efforts to Reduce CSOs:
Addressing CSOs is expensive and involves multiple solutions, such as separating stormwater and sewage pipes, building underground storage tanks, and expanding treatment plants.
According to the Merrimack Valley Region Multi-Hazard Mitigation Plan (May 2024), CSOs are a major regional concern for public and environmental health. These events occur when heavy rainfall causes the volume of sewage and rain to exceed the sewage system capacity, leading untreated stormwater and wastewater to discharge directly into the river. CSOs pose a significant human health threat, especially for communities like Lawrence and Methuen, which rely on the Merrimack River for drinking water. They also elevate risks for river users and negatively impact wildlife and ecosystem health.
City-Specific Efforts:
Haverhill: Haverhill's infrastructure includes both separate and combined sewer pipes, with combined pipes accounting for about 20% of the sewer area. The city has continuously monitored its 13 active CSO outfalls since 2014. Overflow volumes fluctuate dramatically due to precipitation levels, with 2023 being a historic year for CSO discharge at 97.3 million gallons. Haverhill has implemented several phases of its CSO Abatement Program, reducing CSO volumes significantly, with ongoing Phase III focusing on the Locke Street area sewer separation, expected to take nine years.
Lawrence: Lawrence has both separate and combined sewer pipes, with combined pipes making up about 70% of the sewer lines. The Greater Lawrence Sanitary District (GLSD) monitors CSO volumes, which vary with precipitation. In 2022, GLSD reported 41.5 million gallons of overflow, while in 2023, a record high precipitation year, the overflow reached 164 million gallons. As part of the CSO Abatement Program, GLSD has invested over $60 million towards reducing CSO events by completing projects that bolster the treatment process, increasing maximum flow to the plant, and operating a high flow treatment system. To ensure continued operation, GLSD also added full backup power to the main treatment plant in 2019 and the Riverside pumping station in 2020.
Manchester: A $300 million project includes digging a 2-mile-long tunnel, up to 80 feet deep in some areas, to separate stormwater and sewage. This project is expected to reduce the city’s CSO outflow by 80 percent.
Lowell: The city has agreed to an EPA legal order to spend about $200 million on a large-scale pipe separation project and other repairs to prevent sewage from discharging into streets, yards, and basements. Initial construction in Lowell is expected to start in 2025.