From the get-go, the conversation about Dallas City Hall’s future has been polluted by finger pointing, foregone conclusions and unreasonable expectations. Council members are set today to discuss the building again. They should bring the patience, honesty and open-mindedness this debate deserves.

The hulking structure designed by architecture legend I.M. Pei has deteriorated to the point where the city can’t continue to do nothing. Options include moving into a different, existing space, constructing a new city hall or staying put and repairing 1500 Marilla.

City staffers earlier this month presented a wide-ranging estimate that it would cost between $152 million and $345 million to handle the building’s deferred maintenance.

Council members must now decide whether to invest in getting better numbers — probably at great cost — or to cut bait and move on with a different option.

At the briefing earlier this month, some council members sharply questioned the cost figures’ reliability. And we’ll grant that any estimate with a $200 million range is plainly imprecise. But there should be room for a little grace here. Assistant City Manager Donzell Gipson told us staffers had little time to offer an estimate of the total cost of City Hall’s deferred maintenance.

In an Aug. 29 memo, Mayor Eric Johnson named council committee members and outlined priorities for each committee. The finance committee was instructed to “determine whether Dallas City Hall and other municipal facilities effectively support City operations and best serve the citizens of Dallas.”

After the mayor issued the committee charges, staff received a committee assignment asking for a dollar figure on the cost to fix City Hall, Gipson said. The finance committee met to discuss this topic on Oct. 21. By our math, that gave city staff less than two months to come up with a wildly complex number — hardly a reasonable timeframe.

So city staff used what information they had and cobbled together an estimate from bits and pieces of knowledge about various systems and needs in the 1978 building.

The $17 million quote for new emergency generators is a recent one, Gipson explained, so that one should be reliable. Two of the larger items, water infiltration and garage repair, are estimated to cost at $72 million to $100 million and $25 million to $145 million, respectively. Gipson said those estimates are partly based on old quotes adjusted into today’s dollars and partly on other potential unknowns.

There are concerns about leaks in the reflecting pool, for example, and fixing that problem could carry many unknown costs, Gipson said.

What lends credibility to staff’s low-range estimate is a facilities condition assessment dated October 2018. It identified some $92 million in needed repairs and replacements at City Hall, a city spokesperson said. Many of the items in the report were never addressed.

It’s been years since Dallas learned City Hall needed nearly $100 million in maintenance, and deferred maintenance costs grow the longer they’re deferred. So staff’s $152 million low-end estimate may not be a hard quote, but it reads as reasonable to us based on the costs that were assessed in the recent past.

Staff said some of the high-range estimates are based on unknowns. That sounds like a guess to us. But City Hall is an unusually difficult building to work with, in part because it isn’t constructed like most buildings. Its exterior and interior concrete structure makes it hard and expensive to assess costs. So staff threw out a number they hope is the worst-case scenario to fulfill the mandate in the committee charge.

Now, there’s a caveat to all this. Dallas City Hall — both council and staff — have done an abysmal job of managing the city’s real estate assets. Keeping track of the maintenance needs at City Hall and other city-owned properties is grinding work. It’s also work that just doesn’t get done in a systemized way.

The most recent and memorable example of Dallas’ real estate bungles is the building at 7800 N. Stemmons Freeway. The city bought it to use as a permitting center and then couldn’t get permits for it.

The failures ran so deep that City Manager Kimberly Bizor Tolbert instructed staff to “suspend all real estate purchasing unless previously approved by Dallas voters or the City Council.”

The last inventory of city-owned property was in 2017, our newsroom colleague reported in May, and Dallas assessed only 220 of its more than 500 properties at that time.

The most recent city budget did include plans for an updated facility condition assessment, and a February memo does discuss the development of a new “Strategic Real Estate Master Plan.” Hopefully, those steps will help.

As for City Hall, residents will have an opportunity to voice their opinions at a listening session hosted tonight by council members Cara Mendelsohn and Paul Ridley. Both council members oppose tearing the building down, an option we think needs to be on the table.

Some of the talk there will likely focus on staff’s estimates for repairs. The numbers aren’t perfect, but make no mistake, City Hall does have serious and costly problems that must be addressed.

Whether the time is right to move on is a tough call. But pretending that staff inflated the figures just to prime the city for a teardown doesn’t match the facts we reviewed.

A real conversation about what to do next should begin with the reality that this building is in trouble, and there is no cheap way out.