Billions in upgrades lift Long Island Sound water grades, but challenges remain
Investments of billions in wastewater infrastructure across Connecticut and New York have raised water-quality grades for most of Long Island Sound, though the western narrows still score low.
Save the Sound’s biennial assessment indicates that three major basins of Long Island Sound now receive “A” grades, the eastern narrows a consistent “B,” and the western narrows have moved up to a “D” after years of an “F.” The improvement follows billions of dollars in state and federal spending on wastewater treatment upgrades, including about $1.2 billion in Connecticut over two decades and a $40 million EPA program.
Water samples from 2025 measured dissolved oxygen, organic carbon, phytoplankton levels and clarity, among other indicators. Despite the progress, officials warn that rising water temperatures, continued development, and occasional combined-sewer overflows could reverse gains. The report also graded dozens of smaller inlets, with most Connecticut sites earning “A” or “B.” Stakeholders view the results as a sign that investment can restore the heavily polluted Sound, while emphasizing the need for ongoing vigilance.
