LAKE CITY - The sound of an airboat gliding on the snow and ice is a signal to many people who live in the towns along the shores of Lake Pepin.
"Everybody around here gets excited about this," said Kurt Schroeder, surveyor for the U.S. Army Corps of Engineers. "Nationally we have Groundhog's Day, but here, this is our Groundhog's Day. The ice survey means spring is coming."
Schroeder, along with Jack Zannon and Bill Chelmowski, is a member of the U.S. Army Corps of Engineers' crew that conducts the ice surveys on Lake Pepin every February and March.
When they did the first official survey of the season on Feb. 13, they unloaded the USACE airboat at the boat ramp at Roschen Park in Lake City. Two heavy snowstorms in the previous three days had left the boat ramp at Camp Lacupolis, where they normally start, inaccessible.
Even at Roschen Park, the snowplows had left a 4-foot berm of snow at the top of the boat ramp, but Chelmowski navigated the airboat over and through the berm, down the boat ramp, and onto the fresh snow on Lake Pepin.
A brief initial survey a week earlier, made on top of wind-crusted snow, left Chelmowski saying it had been one of the roughest rides of his career. The new snow would mean the longer ride for a full survey would be much smoother.
River mile markers
By starting at Lake City, Zannon and Chelmowski had to travel back to Camp Lacupolis to begin the survey which would end three hours later at Frontenac. Schroeder drove the truck and trailer to Frontenac to meet them at the end of the survey.
"We go from river mile 765 to 782," said Schroeder who has done the surveys for five years. "We measure at one-mile intervals, and we follow the main sailing line that the navigation industry uses."
The location of each survey point on this frozen stretch of the Mississippi River is marked on the crew's GPS. Using the airboat, they travel to each site, and on the first survey of the season, they drill two holes in the ice at each stop.
"The first hole, we will drill down, but not all the way through the ice," Schroeder said. "We mark it with a 10-foot wooden stake with the river mile on it. Then we drill another hole adjacent to it to take the measurement."
On subsequent surveys, the crew can then look for the wooden markers to use as guides for where to take their measurements, assuring that they are measuring the same ice each time and making their numbers more meaningful.
After they drill the measurement hole in the ice, they use "a stainless steel yardstick that has a little L-shaped bracket on the bottom," Schroeder explained. "You just hook it on the bottom of the ice shelf. It has the gauge right on the shaft, and we read the depth right off of there."
Blue or white ice
Schroeder said they also examine the ice to determine if it is white ice, blue ice, or a combination of both. Blue ice is clear and solid. White ice contains air bubbles and is less strong. The crew adds the blue ice and the white ice to determine the total depth of ice at a given spot.
On Feb. 13, the survey crew found the deepest ice was between mile 767 and mile 772 which is very near Lake City. The ice through that distance was 21 inches deep. The depth decreased as they moved farther upstream, dropping to 13 inches at mile 779, and diminishing to zero at mile 783. They found open water from mile 783 to mile 786.
After each survey, they post these results on Facebook and on the website https://www.mvp.usace.army.mil/Missions/Navigation/Ice-Measurements/. They also post data from the last 10 years for easy comparison.
While this information is useful to people using the lake recreationally, it is very important to the commercial navigation industry. Schroeder said they not only want to know the thickness of the ice, but the distance that it remains that thick.
"That helps them determine when they can send the first boat upstream to Red Wing or St. Paul," he said.
Last year, according to the USACE website, "the Motor Vessel Michael Poindexter was the first tow to pass through Lake Pepin and reach St. Paul, Minnesota. She arrived April 11, 2018. Historically the average date in which navigation is open occurs during the third week of March."
Late cold snap
Ice formed late on many parts of Lake Pepin this year with many sections of open water well into December. Then the extreme cold came and "that helped build the ice, but now, it is covered with 2 feet of snow, so that is going to help insulate it," Schroeder said. "We'll see what happens in the coming days."
Schroeder also surveys the river navigation channel in the summers, works on topographical maps, and helps with maintenance and repair projects on the locks and dams.
A temperature of 6 degrees with a wind blowing across Lake Pepin didn't stop him from saying, "This is the best job ever. Every three months you change gears."