While serious challenges remain, Onondaga Lake water quality has improved significantly over the last 30 years.

Restoration Progress

Onondaga Lake is not damaged to a point beyond repair. Significant progress has been made in reducing pollution inputs, and water quality has improved significantly since the 1970s, when restoration efforts began. Status for each major pollutant is discussed below. Additional information about current pollution levels is available under Onondaga Lake Cleanup: Current Status.

Phosphorus

Metro is currently the lake's main phosphorus and ammonia contributor.

Metro is currently the lake's main phosphorus contributor. High phosphorus loading causes excessive growth of algae, which can give the water a cloudy, green appearance, decreases water clarity, and reduces dissolved oxygen availability. Upgrades to Metro were completed in 1979 and 1981. These and other improvements that reduced phosphorus loading over the last twenty years have helped improve water clarity significantly, but not enough to allow recreational swimming.

Ammonia

is also currently the lake's main ammonia contributor. Ammonia can be toxic to fish in high concentrations, and can reduce natural fish spawning and restrict migration patterns. Between 1990 and 1998, more than 90% of the lake's ammonia input came from Metro, because the facility was never intended to remove significant quantities of ammonia from sewage. After recent improvements to the Metro system, Metro's to Onondaga Lake has declined, however, ammonia and nitrite levels that prevail in Onondaga Lake exceed environmental standards established to protect fish and other aquatic life from their toxic effects.

Combined Sewer Overflows

Combined sewer overflows are the main source of bacteria to Onondaga Lake.

Combined sewer overflows are the main source of bacteria to Onondaga Lake. They cause the lake to violate bacteria standards after heavy rainfalls. Public health standards for levels of indicator bacteria are routinely violated throughout the southern half of Onondaga Lake following storm events. Violations occur on about 54 days in the average summer. These violations prevent the lake from being used for swimming.

There were originally 66 overflows to be addressed under the Amended Consent Judgment program. With the completion of the West St. Sewer Separation project and the Hiawatha Regional Treatment facility, and with the completion of the Maltbie, Teall and Franklin St. Floatables Control Facilities, an additional 4 overflows are now treated to remove floatables.

In addition, when the County took over a portion of the City's sewage collection system, the County undertook a widespread program to clean and upgrade the combined sewer system. This led to a major reduction in the number, frequency and volume of overflows into Onondaga Creek and Harbor Brook. This program, called Best Management Practices, maximized the flow of wastewater to Metro for treatment and reduced the discharges of untreated sewage combined with stormwater into Onondaga Creek, Ley Creek and Harbor Brook which flow into the lake.

Mercury

Allied discharged an estimated 165,000 pounds of mercury into Onondaga Lake from 1946-1970. After 1970, the mercury loading was with the onset of new more stringent regulations. Another factor which assisted in improving the lake's water quality was the closure of Allied-Signal Inc.'s (Honeywell) Syracuse operations in 1986. With its closure, direct discharges of mercury, chlorides and other contaminants from that operation also ceased.

Scientists estimate that 7 million cubic yards of the lake sediments remain contaminated. As a result, the lake bottom sediments are listed as a hazardous waste site on the National Superfund List. Allied-Signal, Inc. (Honeywell) is completing a series of mercury studies under the direction of the State Department of Environmental Conservation and the State Attorney General's office to identify the major on-going sources of mercury in the lake system and recommend ways to eliminate contamination in the fish. The ultimate solution to the mercury in the lake's ecosystem and sediments is not known at this time.

Sediment Loading: Tully Valley Mudboils

Onondaga Lake is impacted by high concentrations of clay and silt which are carried into the lake from Onondaga Creek. Most of these sediments come from the Tully Valley mudboils which are located about 15 miles upstream from the mouth of Onondaga Creek.

The United States Geological Survey began remediating mudboil discharge to the creek in 1992. A combination of tributary diversions, pressure relief wells and a dam has reduced sediment loads from 30 tons to one half ton per day.

Salinity

Before the Solvay Process Company (later Allied-Signal) soda ash production facility closed in 1986, the salt content of Onondaga Lake was unusually high, averaging 0.30%. For comparison, this was ten times greater than nearby Otisco Lake.

The concentration of chloride, the most important component of salinity to Onondaga Lake, has decreased from 1600 milligrams per liter to less than 400 milligrams per liter since the closure of the Allied soda ash facility. The salt content of the lake is presently about 0.10% by weight, a three-fold reduction since the soda ash facility closed.

The salinity level of the lake is still artificially high because salty wastes are still entering Onondaga Lake from the Solvay waste beds located along Nine Mile Creek. The waste beds contain of the company's soda ash production. Elimination of continued salt pollution inputs from waste beds would result in reductions in the chloride concentrations of the lake to less than 250 milligrams per liter. Without this loading, the total salt content of Onondaga Lake could approach 0.05%, which is much closer to the levels of other freshwater lakes in the area.