Superfund Information Systems: Site Profile

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Onondaga Lake is located along the northern side of the City of Syracuse in Onondaga County, New York. The lake itself covers an area of 4.6 square miles. Its shoreline borders the city of Syracuse, as well as the towns of Geddes and Salina and villages of Solvay and Liverpool. The site includes the lake and seven major and other minor tributaries and upland sources of contamination. The lake receives water from a drainage basin of approximately 285 square miles, located almost entirely within Onondaga County. Effluent from the Metropolitan Syracuse Wastewater Treatment Plant discharges into the southeastern end of the lake. The lake flows into the Seneca River, which flows into the Oswego River. The Oswego River ultimately flows into Lake Ontario.  

Onondaga Lake has been the recipient of industrial and municipal sewage discharges for more than 100 years. The availability of salt and limestone along and in the vicinity of Onondaga Lake led Honeywell International, Inc.’s (Honeywell’s) predecessor companies (e.g., Solvay Process Company, Allied Chemical Corp. and AlliedSignal, Inc.) to locate along the west side of the lake. In 1946, Allied Chemical started a mercury cell process that resulted in waste streams containing mercury and heavy metals being discharged by its facilities at Willis Avenue and Bridge Street. Honeywell’s Semet Residue Ponds are another source of contamination to the lake. While Honeywell is the site’s primary potentially responsible party (PRP), other industrial and manufacturing facilities located along the shore or tributaries to the lake are sources of contamination to the lake. Site investigations and cleanup activities are ongoing. The EPA and New York State have determined that the site poses no immediate threat to human health or the environment while studies are underway.

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What Has Been Done to Clean Up the Site?

Interim Remedial Measures (IRMs): IRMs undertaken at the site include removing chlorobenzene from existing wells; altering existing on-site sewers; on-site demolition, removal, decontamination and recycling of former mercury cell processing buildings and building materials; cleaning storm drainage systems; investigation of berms surrounding the Semet Tar Ponds; design and construction of a lakeshore barrier wall and groundwater collection/treatment system; and removal of some contaminated sediments and floodplain soils in or adjacent to Geddes Brook and Ninemile Creek.

Long-term Cleanup: Investigations and long-term remedial actions at the various subsites are being performed by the site’s PRPs, pursuant to enforcement agreements between the PRPs and the State of New York. EPA has contributed over $16.5 million to the State of New York for various activities at the site, including investigations, coordination and management at subsites, implementation of a citizen involvement plan, creation of a site-wide database, and establishment of a comprehensive
enforcement program.

Dredging in Onondaga Lake was performed from 2012 through 2014, removing approximately 2.2 million cubic yards of contaminated material. Isolation and thin-layer capping of contaminated lake sediment, which began in 2012, was completed in 2016.

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What Is the Current Site Status?

Cleanup activities at the subsites have been or are being performed via various means (e.g., as part of a cleanup remedy selected in a Record of Decision or as an interim remedial measure). With the exception of the Lower Ley Creek subsite, where the investigation was performed under federal authorities, the investigations and cleanup actions at the other subsites have been or are being performed by the subsites’ potentially responsible parties (PRPs), pursuant to enforcement agreements between the PRPs and the State of New York.

Between 1998 and March 2015, cleanup remedies were selected for 10 of the subsites. Selected cleanup remedies include dredging of contaminated sediments, excavation of contaminated soils, in-situ, on- and off-site treatment of contaminated materials, collection and treatment of contaminated groundwater, and capping of contaminated soils and sediments.New York State is the lead agency for all of the subsites except for Lower Ley Creek. More information about the status of the cleanup of the subsites and the lake bottom can be found on the New York State Department of Environmental Conservation’s Region 7 Project Information webpage. The status of the Lake Bottom subsite and the federal-lead Lower Ley Creek subsite are discussed below. Dredging of contaminated lake sediments (Lake Bottom subsite) began in summer 2012 and was completed in November 2014. Approximately 2.2 million cubic yards of contaminated sediment was removed from the lake bottom and three shoreline areas. The dredging and related capping and habitat restoration work is being performed by Honeywell International with oversight by the New York State Department of Environmental Conservation, the EPA, and the New York State Department of Health. Capping, which included the placement of more than 3 million cubic yards of material consisting primarily of sand, activated carbon, siderite, and stone, was completed in December 2016.  Habitat restoration activities, including improving wetlands and planting native plants, shrubs, and trees in shoreline areas, will continue into spring 2017.


NYSDEC and EPA issued a Record of Decision (ROD) in 2002 for the Semet Residue Ponds Subsite.  The selected remedy addressed the contaminated material present in the ponds and the groundwater.   The groundwater portion of the remedy was completed in 2013.   The portion of the remedy addressing the materials in the ponds is currently being reevaluated.

The cleanup of the LCP Bridge Street Subsite, one of two primary sources of mercury entering the lake, was completed in 2015.

Remedial activities for the Geddes Brook/Ninemile Creek Subsite, which was impacted by sources at the LCP Bridge Street Subsite, were completed in 2014.

Along the southern shore of the lake, a steel barrier wall and groundwater extraction system have been constructed and are in operation so as to prevent contaminated groundwater from entering the lake from the Semet Residue Ponds, Willis Avenue, and Wastebed B/Harbor Brook Subsites. More than 65,000 gallons of free product chlorinated benzenes have been removed, to date, from subsurface soils at the Willis Avenue Subsite using recovery wells and sent off-site for treatment/disposal. Treatability studies to evaluate off-site thermal treatment/reuse options to address the Semet residue material are ongoing.

An interim remedial measure to address contaminated groundwater migration and seeps at, and mitigate erosion of Solvay waste along the shoreline of, the Wastebeds 1-8 Subsite commenced in 2013. A Record of Decision (ROD) for operable unit (OU) 1 of the Wastebeds 1-8 Subsite, which includes Solvay waste and contaminated soil/fill materials present, was issued in 2014. The remedy consists of a two-foot thick soil cover over areas where active recreation is planned or where appropriate to protect ecological resources, and a one-foot thick soil cover where passive recreation is planned.  The remedy has been completed in the area of the site where Onondaga County’s Lakeview Amphitheater and related facilities were constructed.

The General Motors (GM) Inland Fisher Guide (IFG) Subsite includes two operable units. OU1 of this subsite is the former GM-IFG Syracuse Plant property that is located south of Ley Creek on Town Line Road in the Town of Salina. A remedial investigation/feasibility study (RI/FS) is ongoing for OU1.

A remedy for OU2 of the Former-GM IFG Subsite, which includes Ley Creek channel sediments; surface water; and floodplain soils/sediments in the reach from Townline Road to the Route 11 Bridge, was issued by NYSDEC and EPA in 2015. The remedy includes excavating approximately 25,000 cubic yards of PCB-contaminated sediment and soil from impacted media; the design of this remedy is underway. Excavation to remove PCB-contaminated soil from residential properties adjacent to Upper Ley Creek was conducted between September 2016 and December 2016.   EPA’s mobile lab was used for soil sample analyses.

Remediation at the Ley Creek PCB Dredgings Subsite was completed in 2000. The site is undergoing long-term maintenance and monitoring.

Construction activities at the Salina Landfill Subsite began in 2011. Waste consolidation from the landfill area south of Ley Creek to the landfill area on the northern side of Ley Creek was completed in 2011. Construction of the 50-acre landfill capping system and of the groundwater-collection trench north of Ley Creek was completed in the fall 2013. Construction and startup of the on-site leachate treatment system was completed in early 2015.

A ROD for the Niagara-Mohawk Hiawatha Boulevard Subsite was issued in 2010. The remedial design of the selected remedy for soil was completed in 2011. The selected remedy calls for contaminated soil in the northeastern portion of the Subsite that could leach contaminants to groundwater to be solidified in place and groundwater along the northern perimeter of the Subsite to be treated using enhanced bioremediation. The in-situ soil solidification portion of the remedy was completed in May 2014. A pilot study for enhanced bioremediation of groundwater was recently completed.  A design for groundwater remediation is underway.

In 2014, the EPA finalized its plan to clean up contaminated soil and sediment at the Lower Ley Creek subsite, located in the city of Syracuse and town of Salina. The cleanup will include excavation and capping of contaminated soil and sediment in Lower Ley Creek and disposal of the excavated soil and sediment. The parties potentially responsible for contamination at the site are currently working on the remedial design in accordance with an Administrative Order on Consent with EPA.

RI/FSs are currently underway for the Willis Avenue, Waste Beds 1-8 (groundwater), Wastebed B Site/Harbor Brook, and Semet Tar Beds (areas not covered by the first ROD).


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