Portland school district officials told voters in 2017 it would cost $790 million to renovate and modernize three high schools and one middle school, a project voters then approved.

But a new report by a California-based consulting firm shows that not only did initial construction estimates fall short by $100 million, but top officials in the district’s Office of School Modernization knowingly forged ahead with those figures against the recommendations of their staff.

The result? Construction costs for the current round of school modernization could approach or even top $1 billion.

The district now has two options, auditors said: Narrow the scope of its modernization efforts or ask voters for more money.

That audit was the topic of Monday’s school board meeting.

The problems, auditors for Sjoburg Evashenk Consulting wrote, began when district officials pitched construction costs and escalation rates to the school board that were well below estimates drafted by operational staff “without a documented methodology, rationale or explanation.”

When district officials were asked how they came up with their numbers, auditors Catherine Brady and Lienn Luu told the board, there was almost never any paperwork available to explain their process. They were also impeded by the fact that they couldn’t track down former decision-makers in the district’s bond office for interviews.

Brady and Luu said executive staff in the modernization office offered low estimates for so-called “soft costs:” processes such as inspections, permitting and legal fees. An estimated cost of $60 million for programming was also lower than it should have been, the auditors said, especially when the figure could have been checked against 2012 bond costs to prove it was insufficient.

They also told the board those same officials insisted construction costs would grow by 4 percent each year despite historical evidence and the market rate at the time. Market averages never went below 4.4 percent, the report shows, and are currently at 6.6 percent.

“So, at some point, somebody made a decision about a number,” board Chair Rita Moore said. “We don’t know who. We don’t know why. We don’t know how.”

Those averages for yearly construction inflation costs fluctuated by less than one percentage point as district officials presented estimates to the school board and the public. But even those tiny variances add up, Brady told the board.

“That 1 percent has huge repercussions on the budget,” she said. “Whatever went into that estimate was too low. Insufficiently conservative.”

Moore and board member Julia Brim-Edwards, who had not yet been elected when the district referred the bond measure to voters, were easily the most vocal during Monday’s meeting.

“How do we make sure this never, ever, ever, ever, ever happens ever again?” Moore said.

Brim-Edwards repeatedly pressed auditors and current district officials to spell things out in layman’s terms but became frustrated when those questioned couldn’t produce answers. She told other board members she was concerned voters would be hesitant to trust the district with another bond in 2020 if they couldn’t describe the deficiencies of the process in 2017.

“How can we explain this to the community if we still can’t explain the delta between $790 and $1 billion?” Brim-Edwards said. “How do we get to the answer?”

Auditors suggested developing a methodology to produce cost estimates and to store the documentation in a central location. They also said district officials should record how and why they decide to alter estimates.

District spokesman Harry Esteve said in a statement that officials in the central office have already been working to adopt those recommendations.

“We take very seriously our responsibility to be good stewards of public money when it comes to improving and modernizing our schools,” he wrote. “In every case, we look for ways to save on costs while still providing safe, modern and welcoming places for our students to learn and thrive.”

Both auditors and district officials said unanticipated construction boom across the city also inflated costs for the district’s capital projects. Esteve said the district is also looking for ways to contain current costs.

Auditors wrote that the numbers presented to voters began to tick up immediately after board members approved the bond package.

At Benson Polytechnic alone, construction costs may total $296 million at completion, 47 percent more than originally estimated. The school board is already planning to propose rolling some of the inflated costs into a 2020 bond package.

The other schools included in the bond package are Lincoln and Madison high schools, where costs are expected to be $243 million and $199 million, respectively. District officials presented construction costs of $187 million and $146 million at those schools.

Building a brand-new Kellogg Middle School is estimated to cost $60 million total, $15 million above the pitch district officials made.

The report’s authors also wrote that school board members focused more on asking district officials about building designs and program offerings rather than scrutinizing cost estimates in the months leading up to the bond going before voters.

Board members in Portland weren’t alone in that practice; auditors said elected leaders in Oregon’s North Clackamas district and California’s Santa Clara Unified School District were similarly drawn to design questions.

Four of the board’s current members were serving when those bond figures were developed: Julie Esparza Brown, Amy Kohnstamm, Paul Anthony and Mike Rosen. Only Kohnstamm is running for reelection this year.

Sometime after 9 p.m., Moore said six different community and board groups should have caught the discrepancies between the figures presented to voters and those modernization office staffers were relaying to their bosses.

Kohnstamm countered that there were actually just four committees and one, a bond accountability committee, didn’t have a charter that dictated it should oversee the estimate process.

“There was nothing in the charter that precluded that,” Moore said. “As far as I can tell, there was no oversight on the single most important question.”