Octachlorostyrene OCS
A toxic substance and critical pollutant that is a by-product of high temperature industrial processes involving chlorine. Like dioxin, OCS is not produced intentionally. Release to the environment occurs in effluent from chlorine and gas production, aluminum smelting, and other metal production. OCS has been found in leachate from industrial landfills and fly ash from waste incinerators. Related Programs - Binational Program

Oligotrophic
Refers to an unproductive, nutrient poor lake that typically has very clear water. Lake Superior is classified as an ultra-oligotrophic lake.

Ontario Federation of Anglers and Hunters OFAH
An Ontario conservation organization that promotes sustainable use of natural resources by providing boater education programs on exotic species, fish, wildlife, forestry research and management, and timber management policy.

Ontario Ministry of Natural Resources OMNR
This provincial agency is responsible for management of Canadian waters of the Great Lakes to help sustain a healthy ecosystem. Responsibilities of the OMNR include coordinating resource planning with other entities, protecting and enhancing biological resources, managing fish harvest, protecting and rehabilitating habitat and fish communities, enforcing legislation, increasing public awareness of exotic species through educational programming, and monitoring ecosystem health through assessment and research programs.

Ordinary High Water Mark OHW
The elevation marking the highest water level which has been maintained for a sufficient time to leave evidence upon the landscape. Defined in Minnesota statutes as the boundary of protected waters. Generally, it is the point where the natural vegetation changes from predominately aquatic to upland species. For streams, the OHW is generally the top of the bank of the channel. The OHW is the elevation from which building and sewage setbacks are measured. OHWL means ordinary high water level.

Organic Chemicals
Nearly all of the millions of compounds that contain carbon atoms are organic chemicals. More than 90% of all known compounds are organic. The few carbon compounds that are not considered organic include carbon dioxide and bicarbonate. Hydrocarbons like methane are simple organic chemicals that contain only hydrogen and carbon. Other organic chemicals include most pesticides and chemicals based on benzene.

Outfall
The location or structure where wastewater or drainage empties into the surface water from a sewer, drain, or other conduit.

Outstanding International Resource Waters OIRW
This proposed designation by the Binational Program and the Great Lakes Initiative would protect the entire Lake Superior Basin from new or expanded point source discharges of persistent toxic substances.

Outstanding National Resource Waters ONRW
This proposed designation contained in the Clean Water Act Reauthorization would establish special areas within the U.S. portion of the Lake Superior basin where new or expanded point source discharges of persistent toxic substances would be prohibited as part of the Binational Program and Great Lakes Initiative. See also MN Rule Chapter 7050. Related Programs - Clean Water Act

Outstanding Resource Value Waters ORVW
Waters of the State of Minnesota with high water quality, wilderness characteristics, unique scientific or ecological significance, exceptional recreation value or other special qualities which warrant stringent protection from pollution. See MN Rule Chapter 7050.

Ozone
A pollutant formed in the lower atmosphere by the reaction of nitrogen oxides and hydrocarbons in sunlight, commonly called smog, for which National Ambient Air Quality Standards have been established. Ozone is also found naturally in the upper atmosphere where it acts as a protective filter, screening out ultra-violet rays.