GRANITE FALLS -- Floodwaters on the Minnesota River came within an inch or two of topping the main levee in 1997 and inundating anywhere from 250 to 300 homes on the west side of Granite Falls.
It required a dangerous, around-the-clock operation to raise the levee and keep ahead of the rising waters during the flood.
Now, city officials in Granite Falls are authorizing a study to determine what must be done to permanently upgrade the city's main levee to provide protection against floodwaters that could be higher than those experienced in 1997.
Along with providing greater flood protection, the city wants to upgrade the levee so that it can be certified by the U.S. Army Corps of Engineers. That certification could be critical to the homes and other buildings it protects: Absent the protection, many property owners will be required to purchase costly flood insurance for a relatively high-risk flood zone.
Mayor Dave Smiglewski said council members approved the study at the meeting Monday. There was little discussion, as the members are eager to move forward on upgrading the levee, he added.
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City Engineer Dave Berryman, of Rodeberg and Berryman in Montevideo, estimated the study should cost no more than $35,000 to complete. Much of the work will require taking test borings to determine the materials used in the existing levee to assess its integrity, as well as engineering to determine the heights and widths needed for improved protection.
Smiglewski said the levee was built in parts, each time in response to flood conditions. The portion of the levee protecting the city's fire hall and public works garage was constructed immediately after the 1952 flood. A larger flood in 1969 led to emergency measures to significantly expand the levee.
A similar, emergency expansion took place in 1997. City officials believe that locally available clay was used in most of the construction. A project to upgrade or rebuild the levee would very likely be able to take advantage of the materials already contained in it, he said.
Each flood event leads to a recalculation of what is considered the level that waters would reach in a 100-year flood event -- which is a flood event with a 1 percent statistical probability of occurring in any given year.
The 100-year flood level is now pegged at an elevation higher than the waters reached in 1997, meaning that portions of the levee will almost certainly need to be raised, Smiglewski said.
He said the engineer is hopeful the study will be completed by this fall. The Minnesota Department of Natural Resources has earmarked funds for the study's costs, according to the mayor.
The DNR has also orally committed to providing $1 million in 2009 and $1 million in 2010 toward the costs of a levee upgrade. Until the engineering study is completed, there is no way to estimate what the levee upgrade might cost, Smiglewski said.
