Facing dismal financial prospects, the Minneapolis Convention Center is slashing its supervisory ranks and will move more than half of its full-time staff of people who set up and take down for events to an on-call status.

"Without these difficult changes, we risk catastrophic changes to our future ability to provide for our employees, clients and community," Jeffrey Johnson, the center's executive director, told employees in a letter dated Thursday.

The city has been spending as much to subsidize the center as it takes in because operating costs far exceed rents and other charges the facility reaps from conventions, trade shows and other events. The city spent more than $13 million in 2009 from special hospitality taxes it collects to subsidize the center.

Johnson said that 23 of 44 full-time event workers will be shifted to intermittent status, and they will be called to work as needed. Those workers, whom Johnson said have seven or fewer years on the job, will have no guaranteed minimum number of hours. About 30 event workers already are part-timers. Many of the event staff are immigrant workers.

Johnson also said the center will drop one manager and an entire level of supervisors, cutting the number almost in half. He told employees that's a response to their complaints about too much supervision, a lack of trust and a lack of appreciation of their contributions. But he said he's expecting a more collaborative and flexible workforce.

Convention centers have been battered financially across the country, first by a post-9/11 drop in convention travel and then by the recession. Those factors affected Minneapolis just as it was opening a major expansion of the center. Centers nationally have been cutting costs and discounting rents.

"I want to get that subsidy number to go down," Johnson said.

Johnson said the organization cut its operating deficit slightly this year by keeping expenses flat amid an increase in income of about $1 million. But that's still $2 million below 2005. He projected two weeks ago in a budget hearing that the center would draw 204,000 people from outside the Twin Cities to events this year, up from a five-year low of 154,000 in 2010. "We've had a very good summer," he told a council committee.

Both groups of affected workers are unionized. "I know next year's going to be really slow," said Laura Spartz, the business agent representing supervisors. "They had to do something. I don't think they had any choices."

The Convention Center is budgeted for 213 workers this year. It recorded 51.4 percent occupancy in 2010.

Steve Brandt • 612-673-4438