A Minnetonka group opposing the construction of mountain biking trails in a local park has sued the city after it rejected a petition for an environmental review of the project.

The nonprofit group Protect Our Minnetonka Parks filed the lawsuit in the Minnesota Court of Appeals Thursday. It challenges the City Council's denial of an Environmental Assessment Worksheet (EAW) for the project, which would add almost 5 miles of mountain biking trails across Lone Lake Park.

The lawsuit argues that according to language found in a state statute, the city "shall" conduct an EAW if there "may be potential for significant environmental effects."

"The fact that they wouldn't even take into account potential environmental concerns … is very troubling," said Marshall Tanick, the attorney representing the nonprofit, adding that "the city is seeming to turn a blind eye" to those concerns.

The city was notified of the lawsuit Friday and will be assigned an attorney by the League of Minnesota Cities, according to city spokeswoman Kari Spreeman.

Mountain bikers have pleaded with the city for years to build trails for the popular outdoor sport. The city decided on Lone Lake Park — a 146-acre respite with wetlands, dense woodlands and prairies near Shady Oak Beach — as the potential location.

But local environmentalists, including Protect Our Minnetonka Parks founder Maureen Hackett and pollinator expert Heather Holm, say mountain biking would disturb the wildlife, vegetation and other park users.

They were particularly concerned with the effect the sport could have on the rusty patched bumblebee, which was listed as an endangered species by the U.S. Fish and Wildlife Service last year and has been spotted in Lone Lake Park. A study commissioned by the city concluded that the trails would increase the risk of the species being "disturbed and potentially displaced."

Hackett and Holm petitioned the state's environmental quality board to conduct the EAW. The council rejected their petition in August on a 4-2 vote, with council members saying the city had already done a thorough environmental impact study of the project.

"We could do the EAW and be in exactly the same spot … six to nine months from now," Mayor Brad Wiersum said at the time. "We're here to take the heat and make the decision, and live with the consequence of people liking us or not liking us."

The City Council was expected to vote on a concept plan for the project on Oct. 22. The city has yet to decide whether that vote will be delayed, Spreeman said.

Molly Ekstrand, a member of the Minnetonka Mountain Bike Trail Advocates, said it was "unfortunate" that the debate between supporters and opponents of the trails had come to this point.

"The folks that are in favor of the bike trails are also in favor of the environment," she said. "I think it's unfortunate that we can't work together better."

Holm, who has spotted the bee several times since August, said she was disappointed the council rejected their petition.

"Our job is to convince our elected officials that this park truly is unique and special," she said.

For Hackett, the EAW is the last chance to teach people about the park's ecosystem. "What I would like to get out of all of this is for people to know what they're going to lose," she said. "Which is why we're asking the city to look at what they're doing before they do it."

Miguel Otárola • 612-673-4753