Environment and Natural Resources
NEWS ADVISORY: October 11, 2002
For more information: Rich Hanson, 773-4216

Lake Oliver Alum Treatment to Improve Water Quality

PIERRE – The South Dakota Department of Environment and Natural Resources (DENR) invites you to Lake Oliver on Wednesday, October 16, to observe the lake being treated with alum. Media are invited to be at the boat dock on the south side of Lake Oliver at 9 a.m.

State staff and a professional alum applicator will be on hand to answer questions about the alum treatment process. A specially-designed barge with attached booms used to apply the alum should provide opportunities for photos and video. Sweetwater Technology Corporation from Aitkin, Minn., owns the barge and will be responsible for applying the alum.

The alum will be applied to the surface of the lake where depths are greater than five feet. Alum, or aluminum sulfate, is a nontoxic material used to control algae by reducing the amount of phosphorus in the water. As the alum settles to the bottom, it collects suspended particles and traps nutrients at the bottom of the lake.

Alum is used regularly in municipal water treatment plants to help treat water for human consumption. It is also harmless to fish and aquatic plants.

The alum treatment is expected to take three days to treat the entire lake. The alum treatment is part of a larger project designed to improve water quality on both Lake Cochrane and Lake Oliver.

Governor Bill Janklow secured sufficient federal and state funding to complete the Lake Cochrane/Lake Oliver Watershed Improvement Project, which will cost an estimated $125,000. Grants include $75,000 from the U.S. Environmental Protection Agency through the 319 Nonpoint Pollution Control Program, $20,000 from the state’s Consolidated Program, and $7,225 from the state’s Coordinated Soil and Water Conservation Program. The remaining funds will come from the Deuel County Conservation District, Lake Cochrane Improvement Association, East Dakota Water Development District, and local landowners participating in the watershed project.

The Deuel County Conservation District is the project sponsor.

Lake Oliver is a shallow, 180-acre lake located east of Clear Lake just off Highway 22 near the South Dakota-Minnesota border. The lake has experienced water quality problems in recent years and was placed on the state’s 1998 303(d) Waterbody List of impaired waters along with neighboring Lake Cochrane. Lake Oliver was placed on the list because of excessive nutrients, siltation, and noxious aquatic plants. Lake Cochrane was placed on the list because of the presence of fecal coliform bacteria; however, subsequent assessment monitoring in 1999 found low numbers of fecal coliform.

The Deuel County Conservation District completed a total maximum daily load (TMDL) in 1999. The TMDL concluded that the major problem for the two lakes was excessive nutrients in Lake Oliver that lead to the growth of noxious aquatic plants including algae. Sediment in Lake Oliver is the primary source of nutrients within the lake, and that only minimal nutrients reach the lake from the watershed. Treating Lake Oliver with alum to trap the nutrients at the bottom of the lake is the best alternative to improve the water quality and reduce algae. The goal of the project is to reduce the phosphorus concentrations in Lake Oliver by 50 percent.

Sediment retention ponds adjacent to Lake Cochrane will also be cleaned out as part of the overall watershed project. This will help to ensure that sediment loadings to Lake Cochrane remain at a low level. 

Alum treatment has been used successfully to improve water quality in several Minnesota lakes. DENR is not aware of its use on any lakes in South Dakota.

For more information on the TMDL conducted at Lake Oliver and Lake Cochrane, visit www.state.sd.us/denr/DFTA/WatershedProtection/TMDL/TMDL_CochraneOliver.pdf or contact Rich Hanson, DENR, at 605-773-4216.

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