A clean lake reflects well on all of us.


Water Quality in the Past

Population & Industry

As Syracuse grew in the late 19th and 20th centuries, the lake's western shore became industrialized. Sewage disposal and industrial discharges into the lake also increased, and the quality of the water began to suffer. Eventually, people stopped visiting Onondaga Lake for swimming and fishing, primarily because of the lake's degraded water quality. Over time, all of the lake's resorts and beaches closed. By the early 1940s, the lake was mainly being used for the disposal of industrial and municipal wastes.

Sewage Disposal

Municipal wastewater (sewage) has been a major source of pollution to Onondaga Lake. Problems associated with sewage include excessive levels of phosphorus, ammonia and nitrite, and bacteria and other harmful microorganisms, increased turbidity, and reduced oxygen availability.

For years, Syracuse dumped its sewage directly into the lake with little or no treatment. Steps were taken beginning in 1907 with the creation of the Syracuse Interceptor Sewer Board to address sewage-related problems in Onondaga Creek and Harbor Brook.

In 1960, Onondaga County established a sewer district and built a treatment plant (Metro) on the south shore of the lake. The County improved sewage treatment at Metro in 1979, and upgraded again in 1981 and subsequently, notably 2004 with advanced ammonia and phosphorus treatment along with ultraviolet disinfection. As a result, the water quality of Onondaga Lake improved.

Soda Ash Production

Solvay Process Company Facility and Erie Canal, early 1900s

In 1884, the Solvay Process Company began production of soda ash on the Lake shore and nearby properties. Approximately 6 million pounds of salty wastes, made up of chloride, sodium, and calcium, were discharged daily to Onondaga Lake from the Solvay Process soda ash facility before it closed. These discharges significantly affected Onondaga Lake and the Seneca River system. The Lake's elevated salinity reduced the diversity of its aquatic life and reduced dissolved oxygen levels. High concentrations of calcium increased the calcium carbonate formation rate resulting in excessive accumulations on the Lake's bottom. Allied-Signal (a successor to Solvay Process Company) closed the soda ash production facility in 1986, but salty wastes continued to reach Onondaga Lake from the Solvay waste beds located along Nine Mile Creek.

Industrial Pollutants

In 1946, Allied Chemical and Dye Corporation (a successor to Solvay Process Company) began production of chlorine by the mercury cell process. As a result, mercury wastes were discharged directly into Onondaga Lake. The Allied facility discharged an estimated 165,000 pounds of mercury to Onondaga Lake between 1946 and 1970.

Mercury loading was greatly reduced after 1970, and the Allied chlor-alkali plant was closed in 1977. However, scientists estimate that 7 million cubic yards of lake sediments were contaminated with mercury, and mercury remains a contaminant of primary concern because of its persistence in fish.

Other industrial activities on or near Onondaga Lake have contributed PCBs (polychlorinated biphenyls) and chlorinated benzene.

Tully Valley Mudboils

Onondaga Lake suffers from excessive sedimentation—the settling of materials on the bottom of the lake. Some of this material comes from the Tully Valley mudboils located about 15 miles upstream from the mouth of Onondaga Creek.

Mudboils are holes in the earth that discharge mud and soft sediments from underground. They are associated with groundwater flow under pressure. The occurrence of the mud boils have been attributed to solution mining activities in the Tully Valley. There is disagreement over this contention.