From Manhattan Beach to the city of Crosslake, over the span of 4 miles, the highway threads its way past five lakes on the Whitefish Chain. Built 40-some years ago, the road pre-dates the sort of stormwater treatment that allows sediment — and the algae-feeding phosphorus it carries — to settle out before it’s discharged.
“There wasn’t a problem with the road. The problem was the storm sewer collection going directly to these high-quality water bodies,” said Assistant Crow Wing County Engineer Rob Hall in a news release.
When the road was built, curb-and-gutter was installed where it was needed. So was the storm sewer. “You drained it to where water had always drained, which in this instance was the nearest lake.”
The $388,000 Big Trout Lake project installed pipes that channel stormwater runoff to three underground sediment collectors. It drew from a $310,000 Clean Water Fund grant from the Minnesota Board of Water and Soil Resources. Work finished in 2018.
The system treats runoff from 121 acres, keeping an estimated 40 pounds of phosphorus out of the lake each year. Once it enters the lake, each pound of phosphorus can produce up to 500 pounds of algae — which can affect water quality. Decomposing algae also reduces dissolved oxygen in the water.
Water clarity is affected by additional factors including invasive species, wave action, water temperature, precipitation and ice-out. Over the past four years, Big Trout Lake’s water clarity averaged 14.9 feet — an increase of 1.6 feet compared with the longtime average from 1992 through 2016.
Deep and cold, Big Trout Lake supports Crow Wing County’s only population of stocked lake trout. Sandy beaches are part of what attracts lakeshore property owners. The county’s assessed value for Big Trout lakeshore lots and homes exceeds $213 million.
“That’s an important resource, and it’s a resource worth saving,” Jeff Laurel of the Whitefish Area Property Owners Association, said during a 2017 site visit.
The WAPOA board set a precedent when it agreed to pay 75% of the estimated $1,500 annual routine maintenance cost to pump out the sediment collectors. Manhattan Beach will pay the balance.
Crow Wing County Highway Department staff reviewed the plans. The county owns the system, will handle any safety concerns that arise, and eventually will be responsible for replacing it. The highway department was more involved with subsequent stormwater projects in Crosslake.
“This project is definitely a catalyst,” said Crow Wing Soil & Water Conservation District Manager…