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Onondaga Lake

Aerial view of Onondaga Lake looking north. The Inner Harbor is in the foreground.
Aerial view of Onondaga Lake.

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Onondaga Lake and Watershed

Image showing the Onondaga Lake watershed. The watershed covers most of southern Onondaga County.
Onondaga Lake watershed (source:
CNYRPDB). Click for larger image.

Onondaga Lake is located in Central New York along the edge of the City of Syracuse. The lake covers 4.6 square miles, has an average depth of 35 feet and a maximum depth of 63 feet. It is approximately one mile wide and 4.6 miles long. The lake receives water from a 285-square mile watershed located mostly in Onondaga County (the southern tip of the watershed extends into northern Cortland County).

Onondaga Lake's major tributaries are Nine Mile Creek and Onondaga Creek, together accounting for about 70% of all the water that flows into the lake each year. The Metropolitan Syracuse Wastewater Treatment Plant (Metro) is the next largest source of water, supplying approximately 20% of the lake's annual inflow.

Other tributaries include Ley Creek, Harbor Brook, Saw Mill Creek, and Bloody Brook. Water flows north out of Onondaga Lake to the Seneca River and eventually makes its way to Lake Ontario.

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Pollution in Onondaga Lake: A Snapshot

In the 19th century, Onondaga Lake was a popular tourist attraction, with beaches, resorts and amusement parks. Over time, industrial development and a growing population led to increases in sewage and industrial discharges that took their toll on the water quality of Onondaga Lake. Swimming was banned by 1940 and fishing in 1970.

Because of pollution control efforts (which began in the 1970s) and more recent cleanup work, the lake is now the cleanest it has been in over 100 years. The lake reopened to fishing in 1986 (with consumption advisories) and over 65 species of fish have been documented in the lake. The ongoing revitalization of Onondaga Lake has exceeded the expectations of many, but there is still work to be done.

Main Sources, Responsible Entities and Cleanup Status

Pollution in Onondaga Lake comes from three main sources: industrial pollution, wastewater pollution and polluted runoff.

  1. Industrial Pollution
    1. The problem: Starting in the 1880s and continuing for over 100 years, a number of industries discharged waste, including mercury, salt processing residue, ammonia, organic compounds and PCBs, contributing to the contamination of Onondaga Lake's water and sediment. Groundwater at many upland sites was also contaminated. This pollution limited recreational uses of the lake, reduced wildlife habitat, and elevated levels of toxic contaminants in fish and other aquatic life. As a result, Onondaga Lake was designated a federal Superfund site in 1994. The Superfund site includes the lake bottom and subsites around the lake and along tributaries.
    2. Responsible entities: Investigations and long-term remedial actions at the subsites are performed and paid for by potentially responsible parties (PRPs), pursuant to enforcement agreements between the PRPs and New York State. Honeywell, which merged with Allied-Signal (previously Solvay Process Company, the party responsible for much of the pollution), plays an instrumental role in the remediation efforts.
    3. Update on cleanup: Dredging of the contaminated lake bottom was completed in 2014. Cleanup projects at upland sites and in contaminated lake tributaries are in various stages of design, implementation or completion. Some project reports and fact sheets are available on DEC's Region 7 Environmental Remediation Project Information page. Detailed information is also available at the DEC Region 7 office in Syracuse, the Onondaga County Public Library at the Galleries, and other locations identified in the fact sheets.
  2. Wastewater Pollution
    1. The problem: Ammonia and phosphorus in sewage from Onondaga County-owned Metro contributed to impacts on fish migration and reproduction, led to algal blooms and poor water clarity, and decreased oxygen levels. In addition to the ammonia and phosphorus, stormwater runoff entering Syracuse's combined sewer system can overwhelm the system and send untreated sewage and stormwater to Onondaga Lake's tributaries. These combined sewer overflows (CSOs) are a major source of bacteria, trash, organic material, solids and grit. To address the ammonia, phosphorus and CSO problems, a legal agreement was reached in 1989 requiring wastewater treatment plant and collection system improvements.
    2. Responsible entity: Onondaga County is responsible for complying with the legal agreement and the Clean Water Act.
    3. Update on cleanup: In accordance with fulfillment of Paragraph 25 of the 4th Stipulation of the Amended Consent Judgment (ACJ), Onondaga County submitted "Metro WWTP Optimization Analysis of Total Phosphorus Treatment" to the Department in August 2011. This report was approved by DEC in December of that year. The report's recommended actions included modifications to the existing tertiary process, and adjustments for hydraulics, operations procedures and maintenance schedules related to optimizing the current facility in support of ACJ compliance. Implementation of the recommended actions are intended to provide Metro WWTP operations staff with the tools for improving phosphorus treatment performance and reliability while reducing effluent variability. By 2014 the County has also comleted 169 green infrastructures and abated 46 out of 72 pre-ACJ CSOs.
  3. Polluted Runoff
    1. The problem: Stormwater runoff in the Onondaga Lake watershed carries pollutants to the lake and its tributaries. Pollutants include sediment from the Tully Valley mudboils, salt from highway ice removal, fertilizers and pesticides from lawns, gardens and farms, animal waste, and debris and floating trash from nearby streets.
    2. Responsible entities: In addition to efforts by local, State and Federal entities, everyone who lives, works or plays in the Onondaga Lake watershed must do their part.
    3. Update on cleanup: Projects throughout the watershed are reducing sediment, nutrients and other polluted runoff.
      Projects include:
      • a vacuum truck that removes trash from stormwater catch basins;
      • skimmer vessels that remove floating waste from the Inner Harbor;
      • initiatives to reduce mudboil activity and sediment loading to Onondaga Creek;
      • programs addressing animal waste and pesticide management at farms;
      • increased use of phosphorus-free fertilizers;
      • school education programs;
      • measures to control road and streambank soil erosion and stormwater runoff.

Revitalizing Onondaga Lake

Many years of research and remediation has made Onondaga Lake the cleanest it has been in over a century. Pollution, toxicity levels, and algal growth have decreased and water clarity has improved. Plant and animal diversity in and around the lake are showing impressive progress. With these improvements, the lake is once again becoming a destination for outdoor enthusiasts, while serving as a source of community pride.

There is still much to accomplish -- Federal, State and local organizations, residents, and lake users will continue to play a major role in the revitalization of Onondaga Lake.

More information about the pollution history, cleanup status and revival of Onondaga Lake is provided on the Onondaga Lake Cleanup page and in the links below.

DEC Webpages with Information about Onondaga Lake

Join Onondaga Lake News E-Mail List -- Subscribe to Onondaga Lake News and have project information, updates and public meeting announcements emailed to you.

Onondaga Lake Cleanup -- This page describes the history of Onondaga Lake, cleanup efforts from the passage of the Clean Water Act to today, and the status and successes of cleanup projects.

Onondaga Lake Areas of Concern -- Map of polluted areas around Onondaga Lake. Ongoing cleanup efforts are addressing many of these sites.

Return to Glory (PDF) -- 2006 article for the New York State Conservationist magazine describing the history of Onondaga Lake.

Region 7-Environmental Remediation Project Information -- This page lists documents and webpages describing ongoing projects to clean up Onondaga Lake and surrounding areas contaminated with hazardous materials. This page also includes information about many additional hazardous waste cleanup projects in central New York.

Major Ongoing Natural Resources Damages Assessments -- A Natural Resource Damage Assessment (NRDA) calculates the cost of restoring natural resources impacted by hazardous materials. DEC coordinates the NRDA for Onondaga Lake with the federal Department of the Interior and the Onondaga Nation.

Onondaga Lake Fishing -- Fishing information for Onondaga Lake. This page describes plant life, public access sites, common fish species and research programs.

Map of navigational buoys (PDF) -- A printable map of hazards and navigational buoys on Onondaga Lake.

Watersheds, Lakes, Rivers -- What is a watershed? New York has 17 main watersheds that DEC uses as the basis for management, monitoring and assessment programs, and many smaller watersheds like the Onondaga Lake watershed.

Oswego River/Finger Lakes watershed -- The Onondaga Lake watershed is part of the much larger Oswego River/Finger Lakes watershed.

Much of the information on this page was adapted from two documents produced by the CNY Regional Planning and Development Board with support from the Onondaga Lake Partnership: The State of Onondaga Lake 2010 and Onondaga Lake Watershed Progress Assessment and Action Strategies: An Overview. Both documents are available on the Onondaga Lake Partnership website. The DEC is a member of the Onondaga Lake Partnership and works cooperatively with federal, state and local governments on the cleanup of Onondaga Lake.

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