Concern that shade from docks could kill plants and aquatic life in the shallow waters of Lake Minnetonka has officials considering more restrictive dock rules in the popular west metro lake.

The Lake Minnetonka Conservation District, which governs dock use in the lake, is concerned because docks in wetlands and shallow areas block light to underwater flora and fauna.

With most of the lake's shoreline spoken for, developers are increasingly building near marshes and wetlands intending to extend docks into relatively shallow water, said David Gross, chair of the conservation district's environmental committee.

"We are wondering if we should do anything to protect those marshlands and wetlands," he said.

That question will be addressed Wednesday at a public forum dealing with docks and boat storage in water that is 4 feet deep or less. The meeting is from 7-9:30 p.m. at Shorewood City Hall.

"One of our missions is conservation and we haven't been paying that much attention to it," Gross said. The question is, "Do people really believe that we should manage the lake from an ecological point of view?'' Gross said. "We are going to allow people to voice their opinion."

After reviewing relevant scientific studies, a conservation district committee concluded that "there is a conflict between recreational use of the lake and the overall health of the lake."

To preserve lake quality in the face of increasing development, shallow waters "must be protected from the negative effects of surface structures and motorboat traffic. Minimal shading, no wake zones and reduction of boat traffic in shallow areas can mitigate the problem," the committee said.

The best way to minimize dock shade is to elevate the dock, keep it narrow, avoid covering it with structures, and keep it a minimum distance away from other docks. the district said. That might require people to share docks.

If, after hearing from the public, the district decides to change dock regulations, a new rule would likely be proposed by midsummer, Gross said.

Concern about the cumulative impacts of docks and water accessories such as boat canopies, diving platforms and trampolines extends to lakes across the state, said Jack Gleason, the DNR's representative in the dock discussion on Lake Minnetonka.

"We can love our resources to death by over using them," Gleason said. The conservation district is "trying to address over use of the lake."

The DNR is close to adopting new rules to control private structures on public waters. Of most concern are large platforms, some as big as hundreds of square feet, with space for barbecues, trampolines and lawn furniture, said Tom Hovey, DNR public waters hydrologist. "It's basically an expansion of their backyards over public waters."

One reason the large platforms are a problem is because they block light to plants, Hovey said. But they also obscure the visual beauty of the shore line.

"One of our goals is to preserve the natural shoreline," Hovey said. "Minnesota has an enormous amount of economy dependent on tourism. If we let the visuals of the lakes go that is going to be a problem."

The DNR's proposed new water structure rules are awaiting approval from Gov. Tim Pawlenty. When the governor signs off, they will be opened to public hearing. It's possible those new rules will take effect this year, Hovey said.

Laurie Blake • 612-673-1711