Hennepin County and city officials got a look Wednesday at environmental factors that might complicate construction of a southwest light-rail line, but they are still awaiting key information that might determine its fate: how much it would cost, and how much benefit it would provide.

Long-awaited estimates of cost and ridership for the proposed light-rail service from Minneapolis to Eden Prairie were not ready in time for the meeting. They now are scheduled for release Aug. 10.

The proposed Southwest Transitway would be the first light-rail line extending through several suburbs. Commuter rail service is scheduled to open later this year from Big Lake through the northern suburbs to Minneapolis, with passenger trains running on freight tracks.

The Southwest line would become part of a plan to double metro-area transit ridership by 2030. Proponents would like to see it open between 2015 and 2017.

But to receive the necessary federal approval and funding support, supporters of the Southwest line will have to prove that it can improve commuting times and options enough to justify its cost, said Katie Walker, manager of the rail study for Hennepin County.

The Federal Transit Administration has strict requirements for costs vs. benefits before it will provide funding. To go forward, the rail line will have to meet them, Walker said.

The estimates coming soon on cost and ridership will be the first indication of whether the project can meet cost-benefit guidelines, she said.

Routes being studied

Two routes are the most feasible from a construction standpoint, consultants said Wednesday.

One, known as 1A, would run from the new Twins baseball stadium in downtown Minneapolis between Cedar Lake and Lake of the Isles and on through St. Louis Park, Hopkins and Minnetonka to the SouthWest Transit Station in Eden Prairie. It would be built along a light-rail corridor owned by Hennepin County and used now as the Southwest Regional Trail.

The other route, known as 3A, would start out along the same path but veer south in Minnetonka near Shady Oak Lake to run through Eden Prairie's Golden Triangle business district and past the Eden Prairie Town Center to the SouthWest Station. Officials expect the change of direction in Minnetonka away from the light-rail corridor the county already owns to add to both costs and ridership.

Two alternate routes into downtown Minneapolis via Uptown are also up for discussion. They would run through dense areas of housing and employment and would add ridership to the rail line. But with that density would come greater construction cost and complexity, consultants said.

The two primary routes are more feasible when judged according to the numbers of historic properties, environmental resources, contaminated sites, and water resources in their path, the consultants said.

Noise and vibration from the rail line also would affect thousands fewer people on the two primary routes than on the alternate routes through Minneapolis. Noise and vibration on 1A and 3A could affect about 3,500 people, compared with about 7,000 people on the two alternate Minneapolis routes.

Similarly, the two primary routes could affect six or seven historic properties each, run within 500 feet of 15 to 17 park properties, and pass 98 to 99 known contaminated sites, while the two alternate routes in Minneapolis could affect 53 historic properties, run within 500 feet of 21 park properties, and pass 144 to 176 known contaminated sites.

How much these environmental concerns might add to the construction cost of the line would be studied during preliminary engineering, Walker said.

A detailed schedule for consideration of the Southwest Transitway plans was released Wednesday:

•On Aug. 10, the Southwest Policy Advisory Committee -- a group of 15 local officials chaired by Hennepin County Commissioner Gail Dorman -- will see cost and ridership estimates and then make them available at five public open houses on the project, one in each city along the route-.

•Using the cost and ridership information, the advisory committee is scheduled to recommend a preferred route on Sept. 30.

•On Oct. 20, the Hennepin County Board is scheduled to choose a preferred route.

•The Metropolitan Council is scheduled to vote on whether to approve the recommended route in November or December.

If all goes according to schedule, preliminary engineering could start on the rail line early next year, Dorfman said.

Laurie Blake • 612-673-1711

OPEN HOUSES ON LIGHT RAIL PLANS

Five public open houses on the project have been scheduled next month by the Southwest Policy Advisory Committee:

Aug. 11: 6:30 to 8 p.m., Hopkins City Hall

Aug. 13: 11:30 a.m. to 1 p.m., Downtown Minneapolis Library; 6:30 to 8 p.m., Minnetonka Marriott Hotel

Aug. 18: 6:30 to 8 p.m., St. Louis Park City Hall

Aug. 19: 6:30 to 8 p.m., Eden Prairie City Hall

A 7 p.m. presentation on station planning is also scheduled at each of the suburban locations.