The orange goo that has appeared near a recently installed culvert on Lynn Creek may be unsightly, but it’s not a worry for the creek’s fish, according to port officials.
The stain, which has been accumulating on rocks near the creek’s mouth for several months, drew concern recently from the community’s streamkeepers, who worried the residue might harm aquatic life. But now lab tests conducted for Port Metro Vancouver, whose new outflow created the mess, suggest the deposits are harmless.
“It appears to be naturally occurring iron stain,” said Carrie Brown, the port’s manager of environmental programs. “We expected that and did some testing and confirmed it.”
It appears the compound has been picked up by groundwater from an underground source and deposited on the rocks as it escapes through the culvert, which was installed last year in conjunction with the reconstruction of a neighbouring rail bridge. The iron compound, together with elevated levels of manganese also found in the water, are harmless to marine life, according to the port’s findings.
“We had 100 per cent fish survival using Environment Canada’s standard testing method,” said Brown.
When the issue came to PMV in August, the authority sent technicians to the area with workers from Environment Canada. They took water samples from the creek above the stain and below it, and from the mouth of the culvert itself. The samples were sent to an independent lab, which analyzed them and tested them on rainbow trout, a standard gauge of toxicity.
The conservationists who originally called attention to the issue acknowledged at the time that the orange colour might point to naturally occurring iron, but they raised the possibility the compound could cause harm to fish indirectly, by inhibiting the growth of algae, for instance, and disrupting the food chain.
But that isn’t a risk either, according to the port.
“It’s always been my understanding that . . . the concern has been about the iron itself,” said Brown.
That doesn’t mean the authority is willing to live with the status quo, however, she said.
“It’s esthetically orange, which is a challenge, so we’re looking at ways we might come back and remedy that,” said Brown.
Cleaning the rocks isn’t an option, as the chemicals that would have to be used to get the colour off are themselves extremely toxic. So instead the port is looking to discharge the water at a different location where is won’t be an issue.
Plans haven’t been finalized or approved, but the authority hopes to start work on a revamped culvert early next year, said Brown.
Environment Canada is also analyzing samples from the outflow, but the results may take several months, she said.
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