New weir is triumph for Maple Lake Improvement District
By Brenda Erdahl | Article courtesy of Maple Lake Messenger | published in the May 29, 2024 edition
A 3 ½ year journey to make the water outflow on Maple Lake more reliable has come to an end for the Maple Lake Improvement District (MLID).
On May 17 Bituminous Roadway, Inc. finished construction of a weir across Mill Creek that will help to reduce overly high and overly low water levels on Maple Lake. Mill Creek is a natural channel located on the southwestern side of the lake that flows under State Highway 55 and into Ramsey Lake. It’s also the lake’s only outlet.
In 2019, the area was coming off an extremely high-water summer that had multiple lakes enacting no wake restrictions, MLID President Tom Valenta said. A lot of rain late in the year, when typically, rainfall is at its lowest was causing an assortment of problems, particularly erosion issues along the shoreline.
“That got us starting to look at how we could improve the outflow so when the lake reaches levels too high, it can flow out as quickly as possible,” Valenta said.
After a lengthy process that involved the Maple Lake – Lake Property Owners’ Association, Inc., Minnesota Department of Natural Resources and Stantec engineers among others, on May 13th construction of the weir began. Five days later, the project that had been years in the making was completed.
A weir is a water level control structure that will be used on Maple Lake to maintain the runout elevation. According to Chris Meehan, Senior Principal Water Resources Engineer at Stantec, lake runout elevation is important because it impacts navigation (particularly through the channel into Little Maple) shoreline erosion, water quality, ice damage and flooding.
To determine the height of the weir and essentially the target water level of the lake, the DNR would only consider data points from the last 20 years.
“By looking at the historical data, we came up with the average water height change from May through September,” Valenta said. “While it’s not an exact science, the goal is to maintain that 20-year average.”
“It’s not so much about setting a lake height as it is about ensuring if it does get high, it flows out as quickly and efficiently as possible, and in the spring that it’s holding enough water in the lake to last through the summer,” he said.
In a typical year, the water level is at its highest in the spring, because that’s when the most precipitation falls. On average the lake height goes down six to eight inches by the end of the summer.
The weir will work the hardest during times of extreme weather. For example, in the last six years, except 2018 and 2019 area lakes experienced flooding. Then three years ago, the opposite happened.
“The area lakes were bone dry, and people couldn’t get their pontoons off their boat lifts,” Valenta said.
The job of the weir is to ensure the lake doesn’t get too high during wet years and to keep as much water in the lake as possible during dry years.
“Trying to target those averages gives us the best overall quality and experience because it’s in that normal range rather than the extreme,” Valenta said.
Another advantage of a weir is that it creates a designated outflow which means it will be easier to get the necessary permits to clean debris from the area when necessary.
Bogs, beaver dams, and other debris all ride the current that eventually ends at Mill Creek and as the channel nears Highway 55 and narrows to go under the road, all that debris gathers to essentially make its own little dam.
As part of the process to build the weir, MLID sent out a survey to lake property owners and the response was overwhelmingly positive.
The total cost of the project was $151,713 of which a portion was funded by the MLID. A government agency, the LID uses money from tax assessments to better the lake. According to Valenta, 50% of its budget is used on weed control and the other 50% on various projects like the weir. This was by far the organization’s largest project since it was formed on Nov. 14, 2017, he said.
The project was also partially funded through grants from Wright County and the Maple Lake – Lake Property Owners’ Association, Inc.
