For three years now, the City of Calgary and Alberta Health Services have issued warnings to those who want to dip, plunge or splash in the Elbow River, but the source of the fecal contamination remains a mystery.

It could be leaking sewage pipes that are emptying into storms or into groundwater. It could be humans choosing to relieve themselves on the banks of the river. It could be RV enthusiasts dumping waste where they aren't supposed to.

More likely is that it's a combination of many different sources all contributing their bit of contamination to the larger whole.

One thing is clear: while there is animal waste in the water, there is also human sewage.

"We're not likely to find one big thing that's going to fix the river. I sure wish we could. We continue to look, and if we do find something, we will fix that," said Nancy Stalker, manager of water quality services at the City of Calgary.

"In the meantime, it's likely a small variety of a lot of different little impacts."

No pattern

The trick in tracking the source is that it's not coming from one location. The water quality is variable along the stretch from Sandy Beach to the confluence with the Bow, with more concerns as the water gets closer to Ninth Avenue S.E.

No one stormwater outfall is spewing large amounts of contamination at all times.

If that were the case, the city would move up those pipes until it found the source of the contamination and sort out the issue.

There is no pattern.

And groundwater contamination, says Stalker, is tricky to track.

Warnings remain along the Elbow River, from Sandy Beach to the confluence with the Bow. (James Young/CBC)

"For example, we know that trees and roots sure do love sewer pipes because of the water that runs through them, and sometimes they may create a very small hole that that might leak a little bit into the groundwater, and you could imagine how many homes drain into the Elbow," she said.

Contributing to the issue is the fact that the Elbow is shallow and slow moving.

Common problem

Nicholas Ashbolt, a professor at the University of Alberta's school of public health, agrees the city has a difficult task in trying to track the sources of contamination.

Ashbolt says the issue is common in cities, particularly as infrastructure ages, but he is confident in the capabilities of the City of Calgary, which he says is world-class when it comes to water.

"It's one of the problems with going to a gravity-based sewer system. It's vulnerable to this leaking, so it's sadly very common," said Ashbolt.

He said sewers can have undetected cracks for years that drip, drip into groundwater or into stormwater drains. The contamination can travel undetected through those pipes and show up in another location.

Stalker says the city hasn't even been able to detect a relationship between contamination and increased rainfall that swells the river with stormwater runoff.

New sewers

For Ashbolt, it points to the need for a rethink on the way cities deal with waste, something he's been actively working on.

In Sturgeon County, just outside Edmonton, he's working on a pilot project where blackwater — which drains from toilets and sinks — is sent into separate vacuum sewer pipes that don't leak and that save energy.

"So there [are] solutions in the medium- to long-term, as we build new communities and redo downtown infill developments, that we really start moving toward an infrastructure that's not only safer for human health, it actually costs about half as much," said Ashbolt.

"So there's a fundamental shift on the verge of happening in the water industry. And it's a shift that will take decades to implement."

And in the meantime?

"It's really important that people never drink from river water, avoid face and mouth contact with the river so that they don't ingest that, and wash their hands," said Stalker.

"If you do decide to go wading into the river, make sure you're washing your hands before you stick your hand in that bag of chips that you might be enjoying on the side of the river on a hot summer day."