Published On: Wed, Nov 20th, 2013

Flood control costs keep rising

HARTINGTON — A heated discussion at Tuesday’s Hartington City Council meeting revealed city leaders’ concern about adding another expense to the water quality and flood control project.

The city is being asked for an additional $8,400 for three more borings to help determine the actual soil composition on the downside section of the dam, said project coordinator Dan Kathol.

“It will allow the engineers to make the most cost-effective recommendation,” he told the City Council.

Griffin Dewartering North Central LLC, is the company Olssen Associates has been working with to solve some recently discovered problems.  Water that seeps through the sand layers under the reservoir could potentially create uplift when the water hits the clay layer of soil immediately downstream of the reservoir. Engineers say the danger is that water has the potential for traveling under the dam and pulling soil along with it.

Due to the water pressure on clay, which has low permeability, the water could be forced up and backward to the base of the existing dam structure.

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