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Taum Sauk Area Water Quality
How the Reservoir Failure Affected Water Quality
As the upper Taum Sauk reservoir failed, the water carried a tremendous amount of trees, boulders and sand into the Johnson's Shut-In's Park area. As it went through the shut-ins, into the lower reservoir and over the top of the lower reservoir dam and on down into the Black River it carried a huge amount of clays and fine silt. A lot of that ended up in the lower reservoir, in the east fork and the Black River. Increased tubidity, which is water clarity conditions, has been documented by the Missouri Department of Natural Resources down into and through Clearwater Lake.
Conditions in the Black River are historically clear. "We measured water clarity, which is measured in tubidity units," said Randy Crawford, Chief of the Water Quality Monitoring Section of the Missouri Department of Natural Resources' Environmental Services Program. "Typically, in the Black River during a low flow period when it has not been raining, the turbidity is down around one or one to five, which is similar to drinking water when you get it out of your tap. The day after the reservoir failure, turbidity readings were 3,500 units in water in the east fork coming over the lower reservoir dam. Those tubidity conditions have been decreasing over time as that turbid water moves through the system."
Very fine clay particles, some of them 20- to 40,000 times smaller than a grain of sand, were suspended in the water. "When particles that small get suspended in water it can take years for them to settle out," said Crawford. With all the clay particles suspended in the water, the lower reservoir looked like chocolate milk. "Ameren UE came to the department with a plan to use flocculation chemicals to help settle some of those particles."
Running water cleared up very well right after application of the chemicals. The department was getting readings in the target range of 10 to 15 turbidity units. Readings started to go back up, which was expected, due to rain and wave action in the lower reservoir, work on the upper reservoir and other upstream activity. By Feb. 15, turbidity at Lesterville Highway 21 Bridge monitoring station showed a reading of 30 turbidity units.
