Onondaga Lake, in Central New York, has a history of severe environmental degradation. Once a popular recreational spot, the lake became profoundly polluted over more than a century. It earned a reputation as one of the most polluted lakes in the United States due to industrial and municipal discharges.
Historical Industrial and Municipal Contributors
Onondaga Lake’s historical pollution stemmed from industrial activities and municipal waste management. Beginning in the late 1800s, the Solvay Process Company (later Honeywell) operated along the lake’s western shore. This company discharged industrial waste from soda ash and other chemical manufacturing processes directly into the lake’s waters and sediments.
Between 1946 and 1970, approximately 165,000 pounds of mercury were discharged into the lake from chlor-alkali production, alongside salt processing residue, ammonia, and organic compounds. Wastebeds formed along the shoreline from these industrial byproducts. These discharges significantly altered the lake’s chemistry and ecology, leading to long-term environmental issues.
Municipal wastewater also contributed substantially to the pollution. For many years, untreated or inadequately treated sewage from Syracuse flowed directly into the lake. Even after the Metropolitan Sewage Treatment Plant (“Metro”) was built in 1960, combined sewer overflows (CSOs) remained a major problem. During heavy rainfall, the combined sewer system would become overwhelmed and discharge raw sewage and stormwater directly into the lake’s tributaries.
Persistent Pollutants and Their Environmental Legacy
Historical discharges introduced persistent pollutants into Onondaga Lake. Mercury, primarily from chlor-alkali production, was a significant contaminant that bioaccumulated in the lake’s food chain. This led to fishing bans as early as 1970 due to unsafe levels in fish.
Ammonia, originating from both industrial processes and municipal sewage, severely impacted aquatic life. Its presence contributed to oxygen depletion and fueled algal blooms that reduced water clarity. High concentrations of chlorides, with approximately 6 million pounds discharged, also affected the lake’s salinity and its natural stratification.
Polychlorinated biphenyls (PCBs) were another group of persistent industrial chemicals found in the lake’s sediments. Other contaminants, including benzene, toluene, xylene (BTEX compounds), polycyclic aromatic hydrocarbons (PAHs), chlorinated benzenes, pesticides, and heavy metals like lead and cobalt, also settled into the lake’s sediments and contaminated groundwater.
Extensive Remediation Efforts
Remediation efforts addressed Onondaga Lake’s severe contamination. The lake was designated a federal Superfund site in 1994, which mandated a comprehensive cleanup. This designation encompassed the lake bottom and several upland subsites.
Honeywell, as the successor to industrial polluters, took on responsibility for much of the industrial waste cleanup. This involved dredging approximately 2.2 million cubic yards of contaminated sediment from the lake bottom between 2012 and 2014. Following dredging, a cap was placed over 475 to 579 acres of the lake bottom, completed in 2016, to isolate remaining contaminants. A barrier wall was also constructed to prevent contaminated groundwater from reaching the lake.
Onondaga County also addressed municipal wastewater pollution. Upgrades to the Metropolitan Wastewater Treatment Plant (Metro) improved treatment for phosphorus and ammonia. These upgrades led to reductions, with ammonia levels in Metro’s outflow dropping by 98% and phosphorus by 80-86%. The county also launched the “Save the Rain” program, using green infrastructure to capture stormwater before it could enter the combined sewer system, reducing combined sewer overflows into the lake’s tributaries.
Present Condition and Future Prospects
Onondaga Lake has undergone a significant transformation due to cleanup efforts. Water quality is now the cleanest it has been in over a century, showing ecological recovery. Reductions in ammonia and phosphorus levels have led to improved water clarity and a decrease in harmful algal blooms.
The lake’s ecosystem has responded positively, with over 65 fish species documented. Brown trout now persist throughout much of the year due to enhanced dissolved oxygen levels. These improvements have fostered increased recreational opportunities, including public access, trails, and parks.
Despite this progress, challenges remain concerning residual contamination. Fish consumption advisories are still in place for certain species and for sensitive populations, such as pregnant women and children, due to lingering mercury levels. Concerns persist that not all toxic chemicals were fully removed or contained by the remediation, requiring ongoing monitoring and maintenance. While swimming remains prohibited, the long-term outlook involves continued vigilance to ensure sustained recovery and expanded public use.