Crow Wing County staff reports surprises in lakeshore study on impervious surface
Crow Wing County staff reported a research project into the amount of impervious surface on studied lakes surprised them.
The results, they said, looking at lakeshore parcels found less impervious surface than expected. The study is expected to help the county with water planning and help staff more quickly respond in regard to permit applications.
The study, accomplished with a Center for Urban and Regional Affairs grant and staff work along with a St. Cloud State University student research assistance, looked at Borden, Platte, Upper and Lower Hay, Bertha, Pig, Arrowhead, Big Trout, Rush, Hubert, Round and Whitefish.
The study didn’t include parcels inside city limits.
Chris Pence, land services supervisor, said he was surprised to see the imperious surface — such as rooftops, driveways, sidewalks — didn’t necessarily increase as they got closer to the lake.
By county ordinance, residential lots without stormwater plans have a maximum of 15 percent allowed for impervious surface. Lots with a stormwater plan and shoreline buffer may have up to 25 percent.
The study found the highest average percent impervious surface per lot was on Round Lake at 14.5 percent, which decreased to 13 percent within 250 feet of the ordinary high water mark.
Second highest was Rush Lake with 13.7 percent for the average, which decreased to 11.8 percent closer to the lake.
Commissioner Paul Thiede asked if the study information would really convince anyone if larger land parcels around the lakes could be more fully developed. Mark Lield, land services director, said most of these parcels are developed.
“I think that’s the other point they are on these developed lakes ... We don’t have that level of impervious,” Liedl said. “The human foot print can be a good thing.”
Thiede said his point is the county now has more statistics on the development and can it be used on an undeveloped lake to see how much could be developed.
Liedl said the answer is yes if managed correctly.
Pence said he thought Whitefish Lake would be closer to 20 percent impervious, but the study found 4.8 percent on average, which increased to 6.3 percent closer to the lake. There are 745 lots on Whitefish Lake, the most in the study group.
Commissioner Phil Trusty said the data is informative when looking at falling water quality to see what else might be going on besides impervious surface coverage.
Pence said one of the findings from the study indicates the county may want to require a stormwater plan within 250 feet of the lake.
Administrator Tim Houle said there are low-tech ways to accomplish that from swales to rain gardens all designed to keep that water from running off the property.
Houle said there is room to protect surface water, the environment and allow development.
“It seems like there is some room to accommodate all of those interests,” Houle said.
The county has a permit form that shows people how many gallons of water are generated from a one-inch rain event and gives them detailed information on how to contain that water on their property.
The permit is on the county’s website and allows people to put in existing structures and impervious and add proposed impervious surfaces to calculate what they can do. That worksheet is put together for every shoreland permit.
“We strip away I think some of the emotion of what we might feel is good environment protection and we peel that away to what is good science. What do we know is actually causing changes to our surface water quality.
“I think that’s a real exiting proposition here. We can maybe change the nature and the tenor of the debate about what’s good science and how we protect what we all agree is our most precious resource.”