1884: The Solvay Process Company (later to become Allied-Signal Corp.) begins production of soda ash.

1918: The Solvay Process Company begins production of organic chemicals.

1940: Swimming is banned.

1946: Allied begins chlorine production and discharges mercury into the lake.

1960: Construction of the Onondaga County Metropolitan Wastewater Treatment Plant (Metro) is completed. 1970: Fishing is banned. Due to the discovery of mercury in the lake's fishery, the US Attorney General sues Allied-Signal to stop mercury dumping. The amount of mercury discharged to the lake is calculated to be 22 lb/day.

1977: Allied closes chlorinated benzene plant and Willis Avenue chlor-alkali plant. 1979: Metro is upgraded to secondary and tertiary treatment. 1986: Allied closes soda ash manufacturing operations.


Calcium carbonate
Mercury
Clay
Silt
Phosphorus
Ammonia
Nitrite
Pathogenic bacteria and viruses
PCBs
chlorinated benzenes
chloride, sodium, and calcium (salts)


Phosphorus leads to algae growth which impacts the lake's water clarity and when the algae die, oxygen is consumed which leads to depletion of oxygen in the lake.

The Allied chlor-alkali facility discharged an estimated 165,000 pounds of mercury to Onondaga Lake from 1946 until 1970. Scientists estimate that 7 million cubic yards of the lake sediments remain contaminated.

Methyl mercury, formed in aquatic systems through the activity of certain bacteria, is among the most poisonous chemicals known. If all the mercury in the average fever thermometer were converted to methyl mercury, it would be enough to render more than 10,000 one pound largemouth bass unfit for human consumption.

The water in the oceans, which is about 3.5% salt by its weight, is extremely salty compared to fresh waters. For comparison, Otisco Lake, a lake also located in Onondaga County, has a salt content of about 0.03%, nearly 120 times lower than the ocean. Before the Solvay Process Company (later Allied-Signal) closed in 1986, the salt content of Onondaga Lake was unusually high, averaging 0.30%. This was 10-times greater than Otisco Lake.

The water in the oceans, which is about 3.5% salt by its weight, is extremely salty compared to fresh waters. For comparison, Otisco Lake, a lake also located in Onondaga County, has a salt content of about 0.03%, nearly 120 times lower than the ocean. Before the Solvay Process Company (later Allied-Signal) closed in 1986, the salt content of Onondaga Lake was unusually high, averaging 0.30%. This was 10-times greater than Otisco Lake.