The Salt Lake City Council has been warned: A vote against the proposed skybridge as part of City Creek Center could kill the $1.5 billion downtown development.

Bruce Heckman, vice president of development for Taubman Centers Inc., a partner with The Church of Jesus Christ of Latter-day Saints in the City Creek development, tentatively stated that position during a council work session Tuesday afternoon.

Responding to a question from council chairwoman Jill Remington Love about what would happen if the skybridge was not approved, Heckman stopped just short of predicting the project's demise.

"If the skybridge is denied, that would at minimum cause a very large delay where we'd have to consider whether we move forward," Heckman said.

A lot has changed since October 2006, when plans for City Creek Center — including a skybridge over Main Street — were unveiled, he said. The national economy has seen a significant downturn, and department stores and retailers are less eager to commit to development projects. "We've got a changing kind of environment."

The project already has lost one anchor store, Dillard's, in large part because of delays, he said.

Developers of the two-block, mixed-use downtown project had hoped to avoid a final-hour vote on the skybridge, which Heckman said has been a "threshold question."

A significant hurdle was cleared in April 2007, when the council approved amendments to the city's master plan to allow for skybridges in certain circumstances.

The developers say they've met those conditions — a claim supported by a favorable recommendation from the Planning Commission.

Much of Tuesday's work session centered on concerns that inadequate study had been done on alternatives. Soren Simonsen, who along with fellow Councilman Luke Garrott has been opposed to the skybridge, expressed that position.

A public hearing Tuesday night showed that the skybridge remains controversial in the community. Those who spoke in favor or against the skybridge were equally divided, while others — including city activist Cindy Cromer — landed somewhere in between, calling current plans for the skybridge "improved" or "less bad."

The council is expected to make a decision at its April 8 meeting on whether to convey air rights over Main Street to allow for construction of the skybridge. Another work session with the developers also is planned for earlier that day.

Ron Loch, Taubman's vice president over planning and design, revisited alternatives to the skybridge during the Tuesday afternoon work session, detailing options for a single-level project, closing a portion of Main Street, keeping retail all on one block or connecting the project with a tunnel under Main Street.

Most of those options were ruled out, Loch said, because they wouldn't allow enough retail to make the shopping plaza a regional draw.

Simonsen questioned Taubman's criteria for defining that regional draw, asking why existing or future retail along neighboring streets is not considered as part of the equation.

Loch said enough stores, restaurants and department stores need to be grouped together in a walkable space — without gaps — to make the center a destination. The developers expect to draw about 10 million people to the outdoor shopping center annually.

The developers also discussed the difference between the skybridge planned for City Creek Center and others that have been unsuccessful in urban settings.

Heckman said architects and designers have created a unique second-level pedestrian walkway that is not only functional but a destination in itself.

The 130-foot-long, 28-foot-wide bridge has been designed to be transparent but also an "iconic structure," he said. Plans for the enclosed bridge show wetlands reeds and grass etched in glass to make it look like a creek bed, consistent with the rest of the development. A lounge-like area is planned at the bridge's center to provide a place where people could relax or even have pictures taken.

Other Western cities such as Seattle, Portland and San Francisco have successful pedestrian connectors that, like the City Creek proposal, improve safety around a light-rail system, Heckman said.

In other city business Tuesday, the council discussed Mayor Ralph Becker's proposed name change of the city's domestic partnership registry to the "mutual commitment registry."

The council is expected to vote on the name change on April 8. If approved, the registry could be up and running as soon as April 14.

The registry was proposed by Becker and approved by the council to provide a mechanism by which Salt Lake employers voluntarily can extend health care and other benefits to their employees' domestic partners — including gay couples, siblings, long-term roommates and parents.