In May, an 84-year-old woman died in an early morning house fire. Neighbors in Southeast Portland woke at 3 a.m. to the sound of windows popping and found flames.

One called 911 but got a busy signal. Another neighbor got past the 911 system's automated screening process, but hung up after waiting on hold for more than two minutes. Dispatchers never called her back. They had no record she'd ever phoned.

Whenever a 911 call is disconnected, operators with Portland's Bureau of Emergency Communications are supposed to call the number back to make sure the caller is OK.

But at least 18,482 people never got that call last year, according to a city report released Wednesday. That amounts to roughly 50 ignored calls each day, some of them potentially serious. The report also said it's been happening for more than a decade.

Though an investigation by the city ombudsman's office found the failure didn't affect the city's response to the fire, the findings wound up highlighting yet another high-stakes problem for a 911 system already struggling with growing wait times and a staffing shortage.

A screening system meant to filter accidental cell phone calls failed to retain data for tens of thousands of emergency calls, the ombudsman's report found. The loss prevented operators from following city policy and caused the city to underreport hold times and abandoned call rates.

Those statistics are likely worse than reported. Bureau figures reported by The Oregonian/OregonLive in March showed the number of 911 calls on hold for more than two minutes grew from 229 in 2014 to 423 in 2015.

Lisa Turley, director of the emergency communications bureau, called the report misleading. She said the number of disconnected calls include people who hung up before being screened and placed on hold, and that it's possible many of the untracked calls weren't emergencies.

But that's the problem, said Margie Sollinger, Portland's ombudsman: Officials just don't know.

"Every day, we have people who work here, who live here, who visit here who rely on having an emergency system that's sound and reliable," Sollinger said. "And because of that system flaw, we don't have that right now."

Right now, all cell phone calls go to an automated system that requires callers to say "911" or press any number before they're routed to an operator. Callers are placed on hold when operators aren't available.

The screening system is supposed to retain phone numbers -- and notify an operator -- if calls on hold become disconnected. But that hasn't been happening and can't be fixed without an entirely new system.

Overall, operators handled 846,362 emergency and nonemergency calls last year, the report said. Of those, about 354,770 were cell calls that made it through the screening system.The report found an additional 18,482 cell calls that vanished from the system, despite making into the hold queue, when a caller gave up or was disconnected.

"If a caller using a landline or the internet hangs up or is disconnected while waiting on hold, the system preserves the number and an operator generally returns the call to determine whether an emergency exists," the report said. "By contrast, if a cell phone caller hangs up or is disconnected, the number drops off the reader board and vanishes. The call essentially disappears through a crack in the phone system, making it look like it never happened."

Sollinger suggested City Council study whether to screen cell calls only during peak times, when sifting through accidental dial-ups might be too big of a burden.

But Turley said it's not that simple.

She said the screening system must run all the time, or not at all. Not screening calls, she said, is out of the question. Turley said dealing with a call typically takes two to three minutes and that call times would increase without screening.

The bureau has about 120 employees, she said, but only 80 are certified to take calls.

"I'm already short-staffed," Turley said. "It already takes too long."

Cell phones pose a challenge for emergency communications systems nationwide. Beyond a propensity for accidental calls, it can be difficult for dispatchers to determine callers' locations and call-back numbers.

Although several jurisdictions, including Portland, have systems for filtering out unintentional calls, most do not, because they fear screening out real emergencies, the report said.

Turley described Portland's system as akin to a hospital, with operators using triage to manage the overwhelming load.

"For the individual, it's a terrible thing, but for the large scale picture -- for the million calls the entire year -- the (screening system) is entirely beneficial," Turley said. "There are sometimes hard choices, and that's what happens here."

When asked about the disconnected calls, Turley blamed the media and television programs for setting expectations too high -- and cell phone carriers for unreliable service.

"It's kind of magic to me that these calls even get through at all," she said. "We need to accept the fact that sometimes it doesn't work. There's a place where you can't improve it.... I don't know if we're there yet. I'm not saying that we're there or not."

The bureau plans to use a new state-funded call system next spring. The upgrade includes a new screening system that promises to retain all phone numbers so operators can return calls that aren't making it into their records.

But Sollinger's office said the Bureau of Emergency Communications should seek City Council approval before accepting the money and going forward.

Sollinger's report also found the emergency communications bureau never sought council approval before launching its screening system in 2004. The setup was approved only by an advisory board that includes representatives from first-responder agencies. The report said the bureau told the council about the system a few weeks before it went live.

The report found no evidence that the council approved permanent use of the setup.

"This is the front line of public safety so it's the kind of decision that should go before council and the public," Sollinger said.

Commissioner Steve Novick, who took over the emergency communications bureau in 2013, said the bureau responded to the report by warning callers in the automated answering message not to hang up because they likely won't get called back.

"It is an unfortunate situation, but there are no easy immediate answers," Novick wrote in an email.

Turley, meanwhile, is stepping down this spring after 14 years with the bureau. She said a pile of challenges in that time, including the screening system and staffing levels, helped her decision to retire.

"Having to deal with issues like this," she said, "gets old."

--Jessica Floum

jfloum@oregonian.com

@jfloum