As historic spots go, the sidewalk on the north side of E. 6th Street in St. Paul's Lowertown district doesn't rank with Landmark Center or Union Depot.

But the nondescript sheet of concrete is at the center of a debate that promises to simmer as long as Lowertown adds bars and restaurants: how best to tweak the district's charming historic fabric to handle more visitors and a livelier streetscape.

The matter will be taken up Thursday by the city's Heritage Preservation Commission, which may issue an advisory opinion. The City Council is expected to make a final decision within a few weeks.

Dave Brooks and Jim Crockarell, who own the buildings on 6th Street across from Mears Park, want the city to nearly double the width of the front sidewalk to create a promenade for outdoor cafe seating.

They lease to some of downtown's most popular hangouts -- the Barrio and Bulldog restaurants and Bin on the Park wine bar -- and Crockarell believes more draws could be on the way if outdoor seating were extended.

It's a proposal that has the backing of Mayor Chris Coleman, who raised the notion himself last summer, and Council Member Dave Thune. The plan is sweetened by the owners' pledge to cover all assessments, which could top $300,000.

"It will be easier to walk, easier to dine and you'll have this great experience," said Chuck Repke, an East Side leader who's working as a consultant for Brooks and Crockarell.

But many Lowertown residents and businesses, already worried about a parking squeeze they fear will come with the opening of the Saints ballpark in 2015, are against the plan.

They're worried about noise, congestion and pressure they'll face with up to 22 street parking spaces taken to make room for the wider sidewalk and a new bus/bike traffic lane.

Longtime Lowertown developer John Mannillo, who's leading opposition to the proposal, said it would alter the district's circa-1870 street grid and change building setbacks.

He also said it will cost the city at least $60,000 annually in lost parking revenues, a figure that city officials said is double their estimate.

"What happens if, after all is said and done, people don't want to sit outside with the smokers and exhaust fumes? If that happens, it's too late," Mannillo said.

The sidewalk in question runs from Sibley to Wacouta streets and is 10 feet wide. The city's proposal would widen it to 18 feet and maintain the two lanes of traffic that are there now.

But the proposal would drop one parking lane (for the expanded sidewalk) and convert the other parking lane alongside Mears Park to a bus and bike lane.

Outdoor seating has been provided outside Barrio and the Bulldog, but there's little room for more than narrow two-seat tables. A wider sidewalk would permit a row of four-seat tables, Repke said.

Joe Spencer, Coleman's arts and culture director, said that sidewalk cafes have been successful on the other side of downtown outside Pazzaluna and Chipotle.

"You just don't get that feeling of street life and vitality [in the Mears Park area] right now," he said.

Spencer said the mayor's office is willing to look at making the proposed bus/bike lane a part-time parking lane, which would save 16 spaces for at least part of the day.

Coleman also isn't necessarily opposed to an idea that Mannillo is pushing -- trying out the sidewalk cafe concept first with temporary wooden platforms that could be installed on a seasonal basis and remove as needed.

But Brooks and Crackarell won't pay for temporary extensions, Repke said. A pilot installation was tried a couple of years ago, but they didn't like the way it looked or the work required to use it.

"They don't want to have to buy a chunk of wood they would have to store," Repke said.

The pop-ups, as they're called, would cost $73,000 and installation no more than $20,000 annually, Mannillo said.

"We're only going to be using it for, what, four months of the year," he said. "Besides, people prefer to sit on wood rather than concrete. It's not as hot on the hot days."

Kevin Duchschere • 651-925-5035