By Charlie Warner
Argus News Editor
A group of about 75 interested persons attended an informational meeting on silica frac sand mining at the La Crescent High School Fine Arts Center on March 19.
The public meeting had been scheduled a month earlier before the county board voted to approve a one-year moratorium on frac sand mining in the county during the Feb. 28 county board meeting.
The March 19 meeting was sparsely attended, evidently because the one-year moratorium had already been approved by the county board.
Three experts in their respective fields made presentations on the geology of Houston County, groundwater issues in Southeast Minnesota and transportation issues with roadways.
U of M Geologist Dale Setterholm of the Minnesota Geological Survey explained that although the mining of silica sand has been going on in Minnesota for many years, the advent of hydro frac drilling for oil and natural gas in recent years has brought on a much greater demand for the silica sand.
Setterholm described why this type of sand, which is so common in the Coulee Region, is needed for hydro frac drilling. He also noted the closer the sand is located to the surface, the more economical it is to mine.
Most mines, according to Setterholm are 50 feet or less in depth. The top layer of earth is removed and the sand is mined.
A number of steps in the mining process are required, depending on where the sand is located. If the sand is located in a low area, water must be pumped out, the sand is crushed, washed, sized and then transported by truck or rail.
Because it is much more economical to transport silica sand by rail or barge, the closer the proximity to railroads or the river, the better.
Once the silica sand has been mined, there will be a large hole in the ground. Setterholm said the hole can be filled with earth and reclaimed back to its original state or filled with water and turned into a lake, as many iron ore mines in northern Minnesota have.
Setterholm was asked if there would be a danger of losing a natural filter by removing silica sand. He replied that removing the sand won’t change the quality of the ground water in the area. The most active filtering agent for groundwater is soil, not sand.
Minnesota DNR Hydrologist Jeff Green then discussed the various issues with the Karst geology of the Coulee Region.
Green explained that the Groundwater Pumping Act of 1937 has made it much more difficult for large water users to deplete the many aquifers in Minnesota.
The water appropriation permitting process is very involved and highly regulated.
“We are reviewing applications all the time,” Green said. “No major user is going to catch us by surprise.”
By state law, any user pumping more than 100 million gallons of water in a year must receive a special permit. And those users are closely inspected.
“We scrutinize the applications very seriously and the permitting process has gotten much stricter in the past 10 years,” Green noted.
Dr. James Wilde, U of M
Mankato civil engineer
Wilde discussed the various transportation issues involved with increased truck traffic on roadways.
Wilde said studies have indicated that one loaded semi tractor-trailer puts as much strain on a roadway as nearly 3,000 cars.
A newly-completed roadway, with an expected life of 20 years will begin to fail after five years if there is extensive truck traffic on it. In many cases roads with heavy truck traffic are scheduled for a mill and overlay seven to 10 years earlier than roads that are not subjected to excessive truck traffic.
One member of the audience challenged Wilde’s comments and stated that Houston County has many county roads rated at 10 tons per axel or more. That proved to be incorrect.
According to Houston County Highway Engineer Brian Pogodzinski, none of the county roads are rated at 10 tons. The majority are rated at five to seven tons. He did add that all of the state highways in Houston County are rated at 10 tons or higher, with the exception of Highway 26.
You can contact Charlie Warner at [email protected]