With an air temperature of -5 degrees and winds at 15 miles per hour or more, St. Paul District staff from the channels and harbors section took to the ice of Lake Pepin on Feb. 18 for the first of weekly ice thickness measurements.
The 21-mile long lake on the Mississippi River in southeastern Minnesota is the annual host to the event and is often viewed as the first signs of spring. The surveys will continue on a weekly or biweekly basis until the navigation season begins.
To achieve their mission, survey crews from the Corps’ Fountain City Service Base in Fountain City, Wisconsin, use an airboat and a global positioning system to identify the exact measurement locations, which are at one mile intervals from one end of the lake to the other. The depths are used in a weekly report, and the measurements help the navigation industry determine when it might be possible to get tows upstream to St. Paul, Minnesota
“Lake Pepin is the best place to measure the ice thickness because it’s wider and has a slower rate of flow than most other parts of the river,” said Dave Francksen, Corps surveyor. “That being the case, the ice is going to be thicker here. So, this is effectively the last blockage of navigation that would impede commercial traffic on the Upper Mississippi River.”
The thickest ice discovered this year was at river miles 771 and 766, where 21 inches were recorded.
The first tow to pass through Lake Pepin in 2014 was the Motor Vessel Angela Kay, arriving in St. Paul on April 14, 2014. The average opening date of the navigation season in St. Paul for the last 10 years is March 24.
Ongoing work at Lock and Dam 5A, near Fountain City, until March 9, will prevent any up bound tows from reaching Lake Pepin until after construction is complete.
Data from the ice surveys is posted on the St. Paul District’s website. For figures on past and present Lake Pepin ice measurements, see: http://www.mvp.usace.army.mil/Missions/Navigation/IceMeasurements.aspx.