It has been 347 days since the City of Flint declared its lead-tainted water unsafe to drink straight from the tap, and 250 days since Gov. Rick Snyder put the city into a state of emergency.

But the federal Environmental Protection Agency's top official on the ground in Flint doesn't expect current water restrictions to end anytime soon.

Mark Durno, deputy chief of the EPA's emergency response branch, said in an interview that barring extraordinary improvement in water quality this fall, it is likely that the city will remain on filters through at least the rest of the year.

"I wouldn't think so now," Durno said of the idea of lifting the filter restriction before another round of water testing is complete in December. "We're going to be where we are now for the rest of the calendar year" unless lead levels drop more dramatically than expected.

The uncertainty about filters is just one sign of how cloudy the end of the Flint water crisis remains.

Since fall 2015, when local and state officials acknowledged the city's water contamination and moved to change the city's water source back to Detroit's water system, Flint's water quality and lead levels have generally been improving. That's according to government testing and independent sampling by Virginia Tech professorMarc Edwards, credited with bringing widespread attention to the city's lead-contaminated water.

In June, officials buoyed by improving water quality removed restrictions on pregnant women and small children, who had been warned to use bottled water only. Filtered tap water can now be consumed by all city residents, say state and federal officials as well as outside experts.

But two years and five months after the city'sswitch to the Flint River as a drinking water supply, state and federal officials said in interviews they still can't say which specific thresholds will be used to declare an end to the drinking-water crisis or a likely time line.

Among the challenges arethe unprecedented length, scope and intensity of the damage cause by corrosive water moving through the city's water system for nearly 18 months. Other factors include the intense spotlight on the city by federal regulators as well as missteps in a previous lead crisis (in a different city) that prompted officials to declare victory prematurely.

Among them: full compliance with the federal Lead and Copper Rule; optimization of corrosion control to prevent future lead contamination; adequate staffing and personnel training in the Flint water department; replacement of damaged water service lines; determination of a backup water source for the city; readiness to complete the city's transfer to the Karegnondi Water Authority as a new water source, and completion of adopted recommendations by the governor's Flint task force.

The EPA also says it has a working plan, but declined to reveal those details.

"Water quality in Flint is looking significantly better as Flint’s water system continues to improve," the federal agency said in a statement in response to questions about goals and time line. "Flint’s water system has become one of the best-monitored water systems in the nation. And as a result, we now have lots of monitoring data that confirms we are going in the right direction."

But the EPA added that "there can continue to be higher levels in individual homes with lead service lines, so we continue to recommend using filters and flushing. Both are especially necessary where lead service lines are being replaced."

Another crisis year for Flint?

Experts say as a result, all Flint residents may not be able to drink unfiltered water for another 12 months.

"As a minimum, the drinking water needs to meet current drinking water standards and testing needs to demonstrate that the quality is not fluctuating. Given the history of the problem in Flint, the fix needs to control spikes," professor Richard G. Luthy, director of Stanford University's Engineering Research Center for Re-inventing Urban Water Infrastructure, said. "Because of distrust of officials, it would seem that filters would need to be used until the city can say the system has been performing well for a period of time, perhaps for a year."

Luthy said there were phosphate treatments initiated in Rhode Island and Washington, D.C., during similar water crises. "It took 12 months for Rhode Island and six months in Washington for the treatments to become effective," he added.

In contrast to those cases, Flint had untreated corrosive water coursing through its pipes for almost a year and a half before officials switched the drinking water source back to the Detroit water system and reapplied proper corrosion controls.

Some environmental advocates say that relying on the Lead and Copper Rule's guidelines for taking action — the principal barometer used by government officials in news releases — could be misguided when it comes to protecting human health.

Part of the confusion is over the Lead and Copper Rule, which calls for steps to be taken when more than 90% of approved water samples have a lead level of at least 15 parts per billion. Critics have said it's long overdue for revision, but the EPA does not expect any changes until at least next year. In April, one of those critics, Snyder, said Michigan should move to a limit of 10 parts per billion by 2020.

Tom Neltner, Chemicals Policy Director at the Environmental Defense Fund argues that meeting the EPA's Lead and Copper Rule does not mean a water system has a "safe" level of lead, which is a known neurotoxin. The problem, he said, is that this EPA level has no relation to the health risk.

"There is no safe level of lead, but people need something to determine what actions to take," Neltner said. "What level do you need to filter or not?"

He said that EPA officials have promised members of Congress an appropriate level for those concerned about infants who rely on formula made from tap water and considered to be the most vulnerable to lead exposure. It is unclear how this level could apply to giving an all-clear to Flint.

Officials have declined to say whether they have a target lead level for the city and a period of time over which that level would need to be maintained before releasing residents from restrictions on water use.

"Flint makes it real," Nelter said. "It makes it imperative that the EPA answer this most basic question that citizens have."

Past lessons

The uncertainty over the crisis' end reflects the unique nature of Flint's lead contamination — EPA officials call it unprecedented — as well as lessons learned from past public health catastrophes, experts say.

In Washington, D.C., "it took two years to get the 'all clear' ” from the time the problem first became front-page news, said Edwards, who also worked on the crisis there. "In retrospect, the all-clear was given too soon because the EPA allowed the use of 'cheats' to make lead look lower during sampling than when consumers were drinking water," he said. "D.C. children had a higher incidence of elevated lead in blood as the result of this mistake. Care is being taken to make sure that no similar mistake is made in Flint."

Edwards added that he would not be surprised that the city is meeting thefederal law officially in about six months, "but at this point, it is possible that no one will be satisfied with the minimum." The city was declared out of compliance with the federal Lead and Copper Rule during testing between January and June. The next round will not be completed until December.

How and when the crisis ends could have a direct impact on aid promised to the city.

Since Jan. 9, the state has distributed 2,643,622 cases of bottled water, 135,458 water filters, 296,460 replacement cartridges and 54,117 water testing kits, according to the most recent state figures released last week. Free water-related supplies could be critical for residents of the impoverished city in which many still do not trust using filtered water despite assurances from government and independent experts.

No end in sight for Flint; filter use expected to last rest of year

"As far as continuation of bottled water goes, no decisions have been taken as yet, but the conventional thinking is that two to three months should be a reasonable period after the water is uniformly found to be at or above federal standards for any system in the country," said Baird, the governor's point person on the ground in Flint.

He added that "our thinking at this point is that filters have been widely distributed in Flint, and we need to keep on an inventory of cartridges and filter replacements" until all of the lead service lines have been replaced.

A mayor's plea

Any talk about ending free water and filters for the city worries Flint Mayor Karen Weaver.

Earlier this year, Weaver launched her FAST Start program using more than $27 million in state-appropriated funds to remove lead-tainted service lines, but the progress has been slow going. So far, 71 lines have now been replaced during her administration, and the next phase of the initiative is now under way, with a goal of replacing a total of 288 lead-tainted pipes by the end of the month.

"Forty-seven lines completed in nine workdays is great progress," retired Brig. Gen. Michael McDaniel, manager of the FAST Start project, said in a statement last week. "It took us over 30 days to do 33 lines in the state's initial pilot. Our goal is to replace 10 to 12 lines a day so that we complete this phase by the end of the month.”

Still, the city could have more than 10,000 pipes composed of either lead or galvanized steel contaminated by lead that need to be replaced, according to preliminary estimates. ​Lead flakes can build up on the walls of corroded galvanized steel pipes and slough off into the water supply. Pipes made of copper or plastic are generally considered to be safe.

Until all of the lead pipes are gone, free filters and bottled water should be provided by the state, Weaver said.

"This is moving in the right direction, but we are still not in a place where we can drink the water without filters," she said in a recent interview. "I think the trust of the people has been broken for a lot of folks. People just don't trust the filters even if we said that the pipes are 100% coated."

Lead in fixtures too

But outside experts are starting to raise new red flags about other causes of elevated lead in Flint's water.

Two University of Michigan professors warned late last week that home service lines may not be the largest contributor of lead in Flint, despite a major push by the city to replace all of them.

Large spikes of lead occur in homes with and without lead service lines, according to the study's initial findings. Jacob Abernethy, assistant professor of electrical engineering and computer science, and Eric Schwartz, an assistant professor of marketing, wrote that lead can leach from several sources, including the home’s interior plumbing, faucet fixtures and aging pipe solder.

"What we can conclude is that citizens as well as policymakers may need to widen their focus beyond the service line materials and consider alternative efforts to address other sources of lead," the professors wrote. "Service-line replacement is certainly a necessary part of the solution, but it will not be sufficient."

Following the U-M report, state environmental protection officials said they would begin to use a smaller bottle to test those residents who volunteer to have their water tested for lead. The smaller bottle is designed to detect lead in the water system closer to the tap. Officials replaced problematic fixtures in schools, but officials have not talked about what to do about homes with lead in their fixtures and interior plumbing.

Still, state and federal environmental officials say they are heartened by recent testing results that show of the state's 162 samples at Flint homes, 146 were at or below the federal action level of 15 parts per billion under the federal Lead and Copper Rule. These results came during the hottest months of the summer when officials say they expect lead levels to be at their highest.

Only a small fraction of homes tested today exceed federal guidelines. And those homes tend to be older and worth less than other houses in the city, according to U-M researchers.

"The system is settling down, and we're not seeing as much noise," the EPA's Durno said of all of the recent testing reviewed at a joint meeting in Chicago last month.

Durno said broadly that several factors are under watch by EPA officials in Flint. They want to see the city's consistent compliance with the Lead and Copper Rule and proper notification to city residents when those levels are too high. The city's water system also needs close monitoring, especially as the city expects to move to another regional water system run by the Karegnondi Water Authority as soon as next year.

"Our team of experts need to agree that corrosion control has been effectively reestablished in the system," Durno said, added that he thought that goal still remained a "tough" one. "This isn't tied to a standard process."

Still, state and federal officials remain worried and somewhat perplexed about what they described as anomalies in lead levels in some areas. In one sample, according to Krisztian, officials discovered one testing site with 2,000 parts per billion.

Gauging progress

Federal officials say they are also generally pleased with how well orthophosphate is being absorbed into the pipes to help recoat the lead lines and prevent lead flaking into the water supply. Another sign of progress: the near-elimination of "red water," or water samples tainted with high levels of iron, another signal of an unhealthy water system.

Now EPA officials said they are looking for other indicators.

They are in the midst of probing deeper into the causes of lead spikes in the system. Part of the problem may be galvanized pipes that attract lead. Another area of testing will continue to explore testing water at various points along the water system in a process known as sequential testing. This is done, officials say, in a bid to discover where the problematic portions of the pipes may be in terms of lead contamination.

According to a recent report commissioned by the state, records showed that about 10,200 lines have been identified as lead or galvanized steel — also considered risky for leaching lead — and likely need to be replaced. But those records are not completely accurate. Rowe found in the city's pilot project only 64% of sites excavated had been accurately labeled by city records.

Federal officials say more work needs to be done to determine the number and placement of the problematic lines. U-M researchers say their machine learning techniques, which utilize all of the available city data, parcel records and a database of more than 3,000 inspection reports, are able to estimate line materials with better than 80% accuracy to guide the city's pipe replacement program.

"We find, for instance, that houses built in the 1920s to 1940s are many times more likely than those built after 1960 to have lead in their service line," they wrote. "Our guesses aren’t perfect by any means, but estimates of this level can save millions of dollars on recovery efforts."

Part of the recovery effort also counts on residents. They've been urged to clean their faucet aerators regularly and keep the water moving throughout their homes. Flushing faucets on a daily basis and cleaning faucet aerators weekly will help reduce the presence of lead, experts say. Federal officials are also running a separate flushing program that runs up to 24 hours a day.

But for many locals, trust in the city's water quality won't come as long as any lead service lines remain in Flint.

“I don't know if residents will ever trust the water coming out of their tap again unless the pipes are replaced. How can you expect anyone to take the word of experts and test results when we were lied to for so long?" said state Senate Minority Leader Jim Ananich, D-Flint. who raised some of the earliest red flags in the crisis and has been critical at times of the state's approach to recovery.

"What the state needs to do is go all in on helping us get these pipes out and get the system upgrades necessary to guarantee safe water from now on," Ananich said. "That means focusing more on accelerating infrastructure improvements and less on press releases about changes in numbers.”

Contact Matthew Dolan: 313-223-4743 or Follow him on Twitter @matthewsdolan.