Onondaga Lake is located in Central New York, immediately northwest of and adjacent to Syracuse, New York. The southeastern end of the lake and the southwestern shore are industrial areas and expressways; the northeastern shore and northwestern end border a series of parks and museums.

thumb|upright=1.2|Onondaga watershed

Onondaga Lake is a dimictic lake, meaning that the lake water completely mixes from top to bottom twice a year. The lake is long and wide making a surface area of . Its drainage basin has a surface area of , encompassing Syracuse, Onondaga County except the eastern and northern edges, the southeastern corner of Cayuga County and the Onondaga Nation Territory, and supports approximately 450,000 people.

Onondaga Lake has two natural tributaries that contribute approximately 70% of the total water flow to the lake. These tributaries are Ninemile Creek and Onondaga Creek. The Metropolitan Syracuse Wastewater Treatment Plant (METRO) contributes 20% of the annual flow. No other lake in the United States receives as much of its inflow as treated wastewater. and discharges into the Seneca River which combines with the Oneida River to form the Oswego River, and ultimately ends up in Lake Ontario. This includes implementing a long-term operation, maintenance, and monitoring program to ensure the effectiveness of the remedy.

The lake is included in an ongoing land rights action filed by the Onondaga Nation, which seeks the return of its ancestral homelands to promote environmental protection in conjunction with affirming Haudenosaunee sovereignty: "Onondaga Lake is the birthplace of Haudenosaunee democracy. Subsequently and consequently, the lake is the founding site of democracy for the U.S. people and, as such, should be protected as a national treasure instead of the chemical cesspool it has become." According to Grand River Mohawk scholar Susan M. Hill, "Among the Haudenosaunee, the names that the nations call themselves (and each other) denote key geographical features of their home territories… The recognition of geographic identity demonstrates the relationship to the land the people came from, the land they belonged to." For the Haudenosaunee, law is made in cooperation with land and water.

Onondaga Lake is central to The Great Law of Peace, or Kayaneren’kowa. According to Haudenosaunee histories, the five Nations had fallen away from the Original Instructions of Skyholder, or the Creator, who mandated that humans cultivate the land and live alongside "all things that grow" and game animals.

The Nations, who had "lost sight of the harmony and balance provided for in the Original Instructions" The Onondaga Nation website describes this event as the formation of "the first representative democracy in the West."

The event was recorded with the creation of the Hiawatha Belt, a wampum whose design would later be used as the Flag of the Iroquois Confederacy. This belt conveys the guiding principles of the Haudenosaunee, the story of the Great Peacemaker, and the founding of the league at Onondaga Lake.

Onondaga Lake remains a sacred site for the Haudenosaunee, which King directly connects to Haudenosaunee environmental protection and sovereignty: "The value of water and the meaning of water law for the Native American called the Haudenosaunee cannot be separated from a yet-more foundational discussion on Haudenosaunee sovereignty and the right to protect land and Creation must be understood… Views on sovereignty are dependent upon the level of regard one has for the land itself (water, of course, included)." Jesuit missionaries visiting the Syracuse region in the same time period were the first to report on salty brine springs around the southern end of what they called "Salt Lake", known today as Onondaga Lake. The brine springs were reported to have extended around much of the lake for a distance of nearly 9 miles. They extended from the present-day towns of Salina through Geddes and from Liverpool to near the mouth of Ninemile Creek. European settlers, mostly trappers and traders, followed the Jesuit missionaries and French explorers into the Syracuse area during the 17th and 18th centuries.

Among its provisions was the transfer of the lands around the lake from the Onondaga Nation to local salt producers on the condition that the salt would be produced for the common use of everyone.

Onondaga Lake also became a popular resort area. By the late 19th century, its shoreline was dotted with hotels, restaurants, and amusement parks. began drilling deep test holes in the area south of Syracuse in 1883. The company's main product was soda ash, integral to several industries. Eventually Solvay found halite deposits at a depth of below land surface in the southern end of Tully Valley. From 1890 to 1986, more than 120 wells were drilled into four halite beds on the east and west flanks of the valley.

In 1920, the Solvay Process Company merged with four other chemical companies, forming Allied Chemical and Dye Corporation. In 1950 it began the production of chlorine by mercury cell in 1950. Mercury-contaminated waste was also dumped directly into Onondaga Lake. Allied Chemical and Dye Corporation became Allied Chemical Corporation in 1958. Its continued practice of allowing mercury into the lake led to the federal and state governments banning fishing in 1970, due to mercury contamination of the fish. The US Attorney General sued Allied Chemical to halt the dumping of mercury into the lake. It is estimated that Allied Chemical was dumping approximately of mercury into Onondaga Lake per day. In 1981 Allied Chemical Corporation become Allied Corporation; in 1985 it changed its name to Allied-Signal, Inc. when it merged with the Signal companies. The company announced that it would close its operations in Syracuse because of changes in environmental laws, and in 1986 began dismantling its facility.

Onondaga Lake Park Marina

The Onondaga Lake Park Marina is located on Onondaga Lake Parkway in Liverpool.

Wegmans Good Dog Park

thumb|right|250px|Outlet on the shores of Onondaga Lake in Liverpool, New York,

The Wegmans Good Dog Park was the first of its kind in Central New York and is located in the Cold Springs Mud Lock section of Onondaga Lake Park. It is open from sunrise to sunset, seven days a week year round.

In the 1980s, a decision was made to replace the structure with a historically accurate reconstruction. In addition, a visitor center was built. This is used for the display of archeological artifacts recovered from the area, in a more accurate and "hands on" living museum.

Events

thumb|right|150px|Sailboating on the lake in 1907

  • Syracuse Hydrofest - The North American championship of hydroplane racing - annual event in the Willow Bay area of Onondaga Lake Park in mid-June.
  • Lights on the Lake - Onondaga Lake Park in Liverpool from late November to early January.

Pollution

Sewage wastewater

One major source of pollution for Onondaga Lake is municipal sewage. For years, Syracuse dumped human waste into the lake with little or no treatment. Before European settlement and the growth of a large population in the area, the lake was oligo-mesotrophic, meaning that it contained low levels of aquatic plant blooms. The low oxygen levels lead to the choking out of fish and plants, especially in the deeper areas of the lake. Through these tributaries, the CSO eventually reaches Onondaga Lake. CSO has been generating concerns about bacteria. In Onondaga Lake the chlorinated benzenes are located in the southwest portion, in the form of a dense oily liquid that has settled into the sediments. A fishing ban was imposed in 1970 due to mercury contamination.

Sewage pollution cleanup

The first steps taken to control sewage pollution occurred in 1907 with the creation of the Syracuse Interceptor Sewage Board. It served to address sewage-related problems in Onondaga Creek and Harbor Brook. In 1960, Onondaga County established a sewer district and built the Metropolitan Sewage Treatment Plant ("Metro") on the south shore of the lake. In 1988, ASLF, the state of New York, and Onondaga County reached a settlement

outlined in a Consent Judgement which required the county to pay Upstate Freshwater Institute to create water quality models for the lake. These models would then form the basis for discharge limits imposed on the county's Metro facility.

In 1990, the U.S. Congress created the Onondaga Lake Management Conference (Public Law 101-596, section 401). It ordered the group to develop a comprehensive revitalization, conservation, and management plan for Onondaga Lake that recommends priority corrective actions and compliance schedules for its cleanup. The Conference also called for coordination of implementing the plan. The largest responsibility of the Onondaga Lake Management Conference was the completion of the Onondaga Lake Management Plan.

In 1997, New York State, Onondaga County, and ASLF reached an agreement, the Onondaga Lake Amended Consent Judgement (ACJ), on municipal wastewater collection and treatment improvements. The ACJ called for a schedule to attain compliance with the Clean Water Act. The ACJ is a multi-year program designed to improve the water quality of Onondaga Lake while achieving full compliance with state and federal water quality regulations by December 1, 2002. ACJ projects are divided into three main categories: wastewater treatment, collection system, and lake and tributary monitoring. Since 2007, Onondaga Lake has been in full compliance with the ambient water quality standards for ammonia. It was officially de-listed for that particular parameter in the State's 2008 list of impaired bodies of water.

The ACJ achieved other successes. Between 1993 and 2006, the phosphorus discharges from Metro were decreased by 86%. Regarding contamination via CSOs, the ACJ required that by 2010 the county eliminate or capture for treatment 95% of the CSO volume generated during heavy rain and snow melt. In 2011, Honeywell completed second-phase construction on this barrier wall. The estimated cost of the cleanup plan was $451 million; an estimated $414 million in order to construct the remedy, followed by an annual maintenance cost of $3 million.

The plan called for a cap covering of lake-bottom. Capping began in August 2014, and was completed in 2016. Habitat restoration was completed in November 2017.

In 2015, the EPA's first five-year review found that the addition of diluted calcium nitrate solution was effective in containing methylmercury (MeHg) in deep areas of the lake, which helped reduce MeHg concentrations throughout the lake and in zooplankton.

Audubon New York honored Honeywell with the 2015 Thomas W. Keesee Jr. Conservation Award for its role in "one of the most ambitious environmental reclamation projects in the United States."

As part of the scope of the cleanup project, Honeywell has funded and operates the Onondaga Lake Visitors Center, which opened in 2012. The center, located on land owned by the New York State Department of Transportation adjacent to Honeywell's cleanup headquarters on the southwestern shore, presents information about the ongoing cleanup.

Sedimentation control

Since 1992, the Onondaga Lake Partnership has supported the efforts of the United States Geological Survey (USGS) in the following remedial activities: the diversion of surface water away from the mudboils, the installation of a dam on the stream that flows from the mudboils area, and the drilling of wells to reduce the pressure around the mudboils (21).

A survey in 1928 showed the lake was habitat for only ten remaining species. In addition, in recent years, areas around the lake have become an overwintering spot for bald eagles, a demonstration that the fishing is good.

According to Kimmerer, these improvements are both the work of restoration efforts and the water itself:<blockquote>Engineers, scientists, and activists have all applied the gift of human ingenuity on behalf of the water. The water, too, has done its part. With lessened inputs, the lakes and streams seem to be cleaning themselves as the water moves through. In some places, plants are starting to inhabit the bottom. Trout were found once again in the lake and when water quality took an upward turn it was front-page news. A pair of eagles have been spotted on the north shore. The waters have not forgotten their responsibility. The waters are reminding the people that they can use their healing gifts when we will use ours.

Onondaga sovereignty and environmental justice

thumb|right|250px|Onondaga Lake outside Syracuse, New York, in the moonlight

The lake is also subject of a land right action filed on March 11, 2005, by the Onondaga Nation. The Onondaga Nation has been seeking the return of its land for over 200 years because its land was unlawfully ceded by "unauthorized Onondaga negotiators" in 1788. The Onondaga Nation sought the protection and conservation of the natural resources within and affecting the Nation's land, and the security of Onondaga rights to hunt, fish, and gather resources for subsistence and cultural needs. According to Sid Hill, the Tadodaho of the Haudenosaunee, the Onondaga people want the water, land, and air returned to its condition prior to being illegally taken by New York State in the 18th and 19th centuries. Hill considers the degraded state of Onondaga Lake as evidence that neither New York State nor federal authorities can adequately care for the land and water resources.

According to Kimmerer, "The Onondaga land rights action sought legal recognition of title to their home, not to remove their neighbors and not for development of casinos, which they view as destructive to community life. Their intention was to gain the legal standing necessary to move restoration of the land forward. Only with the title can they ensure that mines are reclaimed and that Onondaga Lake is cleaned up." on "Environmental Injustice in the Onondaga Lake Waterscape, New York State, USA," in which they say, "Onondaga leaders argue that infringement of their nation's traditional resource use rights and desecration of its aboriginal territory, especially places like Onondaga [L]ake that are central to its culture, have harmed their people's cultural, economic, physical, emotional, and spiritual well-being." Further, Kimmerer quotes Clan Mother Audrey Shenandoah: "In this action, we seek justice. Justice for the waters. Justice for the four-leggeds and the wingeds, whose habitats have been taken. We seek justice, not just for ourselves, but justice for the whole of Creation."

Kimmerer argues that the precedent of the Kaswentha demonstrates the Onondaga Nation's negotiating skills: "The Onondaga Nation, perhaps the oldest continuing democracy on the planet, protected much of its land and lifeways from the European settlers' encroachment through skillful negotiations, beginning with the [Kaswentha] and continuing through subsequent treaties based on the same principles of sovereignty and mutual respect.