TORONTO — It was five years ago that a small-town disaster destroyed lives, tarnished personal and political reputations and shattered Canadian complacency about something long taken for granted - tap water.

The deadly May 2000 tainted-water tragedy in Walkerton, Ont., had such a profound impact on public attitudes towards drinking water that Jim Smith, Ontario's chief drinking water inspector, doesn't think it likely that it could ever happen again.

"I don't see another Walkerton as having a high probability of occurrence," Smith said in an interview. "I believe Ontario's water is safe."

That view is a little too optimistic, say experts and observers, who agree the province has made tremendous progress, but also warn that the job of ensuring tap water never again threatens public health remains unfinished.

"The day before Walkerton happened, the ministry was of the view that our drinking-water regime was one of the strongest in the country, if not North America, and residents had very little to worry about," said environmental lawyer Paul Muldoon.

"Then Walkerton happened."

The crisis that bloomed over the Victoria Day long weekend five years ago went on to kill seven people and sicken 2,500 - half the rural midwestern Ontario community's entire population - after E. coli bacteria from cattle manure was washed into a town well.

"It was almost impossible in those early, awful hours to believe that such a thing could happen here in Ontario," Environment Minister Leona Dombrowsky told the legislature Thursday in a statement marking the anniversary.

"The seven deaths and thousands of illnesses were all the more terrible because these people were betrayed by something they thought they could trust entirely - their drinking water."

Walkerton's water system, it turned out, was vulnerable in part because the two untrained brothers who ran it, Stan and Frank Koebel, didn't grasp the importance of monitoring and treating the water properly under what were mostly voluntary guidelines.

A far-reaching judicial inquiry into the outbreak also exposed gaping flaws in the government's approach to drinking-water safety.

"The Walkerton tragedy shook the foundations of our faith in many institutions, including government," Dombrowsky acknowledged.

To help restore that trust, the government has implemented about half of the 121 recommendations that flowed from the inquiry almost three years ago, including creating Smith's position of chief drinking water inspector.

The rest are in the pipeline, Smith said.

Key recommendations already implemented include stringent legal requirements for monitoring, testing and treating water; certification of those who run waterworks; and strict protocols for the properly reporting of contamination.

There's also a bulked-up water division at the Ministry of the Environment that has implemented a rigorous inspection program to ensure compliance with the new regulations.

"We have a fail-safe system in place that has a comprehensive set of checks and balances," Smith said. "I wouldn't say there are weaknesses at this point."

Environmentalists disagree, citing as the most glaring deficiency the lingering absence of legislation to protect water from becoming contaminated in the first place.

"It's protecting the sources of water, which is the first barrier but the most important," said Muldoon, executive director of the Canadian Environmental Law Association.

"The drinking water of the province is not protected until that source-water protection is passed, and it's good legislation."

The provincial government had promised a law this spring. That's now been pushed back at least until the fall, sparking fear among environmental advocates that the Liberal government may be getting cold feet.

Still, Walkerton resident Bruce Davidson, vice-chairman of the grassroots lobby group Concerned Walkerton Citizens, has praise for the strides the government and ministry have made so far.

"You're not going to have something that says, 'People could die' land on the desk of one man and then be ignored," Davidson said.

"You now have changes to ensure that scenario doesn't happen."

The disaster launched a second career of sorts for Davidson, who now speaks about water safety to audiences across the country. He's learned that "ignorance and arrogance" remain the most serious threats to the safety of Canada's drinking water.

"You still have some folks who are not grasping the full consequences of tainted water," Davidson said. "Some people are still looking at Walkerton as a one-off. Walkerton is anything but a one-off. We have to drive that message home."

Walkerton touched off shock waves that resonated across Canada and prompted every other jurisdiction to look at its own approach to drinking-water safety, said Duncan Ellison, executive director of the Canadian Water and Wastewater Association in Ottawa.

"All of the provinces looked at their regulatory programs and decided that there were some gaps and that those gaps could be filled," Ellison said. Several provinces, Quebec and Nova Scotia in particular, significantly tightened their legislative frameworks, he added.

But Davidson said he still encounters front-line water managers who cling to the old ways, and don't see a problem with fudging well or chlorinator records the way the Koebel brothers did.

The Koebels had no formal training or testing of their skills before being licensed to run Walkerton's water system; they were "grandfathered" by virtue of two decades of on-the-job experience, which came with little technical or scientific expertise.

That still applies to about 1,200 of 8,000 water-system operators in Ontario, where Smith said the rules governing operator training and certification have seen a "significant strengthening" in Walkerton's wake.

The number of untested operators is down by about half over the past couple of years and by this time next year, every one of them will have been properly trained and tested before being licensed, he said.

The task of training operators, especially in remote areas, will be taken up by the new Clean Water Centre that officially opens in Walkerton at the end of the month, in the very building where the landmark inquiry into the tragedy took place.

Officials in Walkerton say they hope the centre will become a symbol of their town's transformation from a lingering symbol of the problem into a proud part of the solution.

"We still have hundreds of people in this community whose health has been permanently impaired," Davidson said.

"The cost of this is just beyond belief."