Iowa DNR unveils Twelve-Mile wetland project

Published: Tuesday, Nov. 20, 2012 11:30 a.m. CDT • Updated: Wednesday, Nov. 21, 2012 10:40 a.m. CDT

Proposed plans for the Twelve-Mile Lake wetlands project were discussed at a public information meeting Wednesday.

The wetland and accompanying structure to be built will sit just above Twelve-Mile Lake. A host of native grasses and other organisms will serve as a filter for water run off resulting in improved water quality and healthy lake habitat, reduce costs, alleviating some problems at the water treatment plant.

The main purpose of the proposed wetland is to improve and maintain water quality of Twelve-Mile Lake.

"One of the primary drivers of this project, in terms of long-term protection, is removing and storing sediment and nutrients from run off from the watershed" said Steve Green, general manager of Creston Municipal Utilities.

Twelve-Mile Lake is currently Creston's main source of drinking water.

"The city is interested in protecting their investment for the people of Creston and for future use," added Mayor Warren Woods.

Erosion has caused an increase in siltation in the lake. Excessive nutrients, phosphorus and nitrogen, have increased as a result of water run off. Nutrients entering Twelve-Mile Lake cause algae, bacteria and other tiny organisms to grow. While some are required for the lake to maintain its health, too many nutrients can be harmful.

Poor water quality can lead to an increase in algae blooms which cause an unpleasant odor, greatly reducing the appeal of the lake. Severe algae blooms greatly impact the sport fish population and quality of water for human consumption.

"To remedy a nutrient problem in the lake, some of the best ways, is to do it, are to spill that water into an area that is shallow enough where rooted plants can grow, and they would consume the excess nitrogen and phosphorous in a location that doesn't impact the lake," said Gary Sobotka, fisheries biologist of Iowa Department of Natural Resources. "These wetlands have a proven track record of removing the nutrients from the lake. The clearest water we have comes out of these areas."

Some concerns from nearby residents were addressed.

Green said the proposed wetland will not cause flooding to neighboring land. The continuous, slow moving water will be drained seasonally in the summer months.

Twelve-Mile Lake restoration wetland project will take place during 2013 and 2014. The cost of the project is estimated at $400,000 with structural costs shared by the Water Enhancement Review Board and Iowa Department of Natural Resources.

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