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Storm water complicates Lake Street transit project
by Drew Kerr
Published: June 25th, 2012
The proposed $160 million, Interstate 35W-Lake Street project, may become more
expensive because of storm water issues.
Costs associated with adding a transit station and new on- and off-ramps
connecting Lake Street and Interstate 35W in Minneapolis may be going up.
Officials working on the project – already estimated to cost as much as $160
million – say the Federal Highway Administration recently advised that a plan
will be needed to handle storm water and prevent flooding on the interstate if
the work is to move forward.
State and city officials say the worst-case scenario is that they will have to
build a new storm tunnel costing more than $60 million, but they are working to
come up with less expensive alternatives.
Inadequate drainage has been an issue in south Minneapolis for years, but is
coming back into focus because of the amount of impervious surface needed for
the I-35W/Lake Street project — 15 acres.
The Hennepin County-led project includes plans to add a southbound I-35W exit
ramp to Lake Street, a northbound entrance ramp from Lake Street and a
two-level bus rapid transit station that would sit in the center of the
interstate. Funding for that work also remains uncommitted.
While officials say those plans alone aren’t going to create flooding, they are
giving the federal agency fresh cause to revisit longstanding concerns about
storm water management in the area.
A 12-foot-wide storm tunnel, built in the 1970s, runs 100 feet beneath the
interstate and serves as the primary channel for bringing storm water from
south Minneapolis to the Mississippi River. Even without the additional
pavement, it is frequently overwhelmed, leading to flooding during heavy
rainstorms, engineers say.
Engineers who looked at the issues more than six years ago determined the
tunnel should be closer to 20 feet wide, but no work was done.
Jim Grube, director of Hennepin County’s Public Works Department and a leader
on the Lake Street/35W project, said the storm water issues were anticipated
but came into focus after designs became more fixed.
Though Grube said the county shouldn’t take the lead on finding a solution, or
commit any funding for the associated costs, he will continue working with
partners to figure out how the project moves forward.
Planners are in the midst of a three-year effort to ready the project for
construction, and design work is expected to continue through 2013.
“What we’re doing is we’re peeling an onion and sometimes that makes us cry,”
Grube said. “I suppose the drainage issue may make us cry, but we’ll keep
peeling.”
City and state officials say they are working on plans for storm water
retention ponds, additional culverts and other mitigation strategies that could
satisfy the federal agency’s concerns. The project advisory committee will meet
Thursday to tour the site and discuss next steps.
The city and state jointly own the existing storm tunnel and are seen as having
the primary responsibility for addressing the issue.
Peter Wagenius, policy director for Minneapolis Mayor R.T. Rybak, said the city
has yet to identify ways to pay for future storm water work and described the
$60 million expense as “unacceptable.”
“All we know now is what the worst-case scenario is — and that’s having to
build a $60 million-plus storm tunnel,” Wagenius said. “Sixty million [dollars]
is a lot more than we’re prepared to swallow, so we have to do something
different and we don’t know what that is yet.”
Craig Wilson, a principal at Minneapolis-based Sustology, an environmental
consultancy that has worked with the city on storm water issues in the past,
said the goal should be to deal with the storm water closest to where it
originates.
Green roofs, rain gardens and other on-site controls are better
environmentally, and in many cases less expensive than building infrastructure
that would carry the water elsewhere, Wilson said.
“A much better strategy is to try to work with what we have and stop water
before it even gets to the system,” he said.
Whatever challenges project backers now face, Wagenius and others say they
don’t expect the storm water issues to keep the project from moving forward.
Improving the Lake Street-I35W intersection is a priority for the city, in part
because it is closely linked to ambitions to redevelop the nearby Kmart site
and reconnect Nicollet Avenue.
Officials say the future development of the Kmart site, which sits just west of
the I-35W and separates Nicollet Avenue, is largely dependent on improving
interstate access and bringing better transit to Lake Street.
Joyce Wisdom, executive director of the Lake Street Council, which represents
businesses along the Lake Street corridor, said she hopes officials will
consider those larger ambitions.
“This is the perfect time to be looking at the whole site,” she said.