IMPACTS OF A SPILL OF NO. 6 FUEL OIL ON LAKE WINONA

ABSTRACT A spill of about 7,400 gallons of No. 6 fuel oil into Lake Winona provided an unusual opportunity to observe the behavior of a residual fuel oil in a confined freshwater environment. Oil-laden condensate from Winona State University's heating plant entered Lake Winona via a storm sewer during the winter and, because of ice cover, went undetected until April 15, 1979. Because its density was almost the same as water, the oil caused unusual problems. Surface fractions were readily removed by standard measures, but cleanup was thwarted by heavier fractions which rose continually from the lake bottom and drifted throughout the lake. Scuba divers located a pool of heavy oil in a deep area near the storm sewer outlet and most of it was pumped into an on-shore reservoir. Globules of oil continued to rise from the lake bottom during the ensuing summer season, severely curtailing recreational use of the lake. The spill resulted in the deaths of waterfowl and it apparently stressed spawning sunfish sufficiently to trigger a kill by Flexibacter columnaris bacteria. The oil produced no taste problems in fish flesh. The cost of cleanup was almost $104,000, and a civil penalty of $3,500 was levied against the State of Minnesota. The entire episode was documented photographically.