Recent Puget Sound sewage spill not as bad as it could have been

It's unnerving to consider what poured into Puget Sound last week during King County's worst sewage spill in decades:

Toilet tissue, bacteria, viruses, coffee grounds, pharmaceuticals, heavy metals, holiday spices — and untold amounts of human matter better left undescribed.

Yet just days after a malfunctioning switch at a wastewater-treatment plant released an Exxon Valdez-scale dump of raw sewage, contamination levels in Elliott Bay were returning to normal.

Experts said that's because a 10-million-gallon shot of untreated wastewater, while unacceptable, pales when compared with the toxic insults funneled into the Sound legally every day.

Every 24 hours, poisonous heavy metals such as copper splash into bays by the ton in stormwater runoff. In a given year, 123,000 metric tons of toxic oil-based chemicals may wash in off streets and parking lots.

The city of Victoria sends more than a million gallons of raw, untreated sewage water — solids are held back by a screen — into the Strait of Juan de Fuca every hour. Just last year, King County's overflow system pumped out 105 million gallons of raw sewage and rainwater during storms.

"We put so much into the Sound already that what ... happened [last week) is a minor blip," said Rick Keil, a University of Washington oceanography professor who studies the chemistry of pollutants in Puget Sound.

Not that the error is forgiven, or without consequence. In the wee hours Monday morning at the county's West Point plant in Discovery Park, a mishap with a sensor sent the roughly 5-to-1 mixture of stormwater and sewage through a pipe into relatively shallow waters of the bay.

Ecologists expect the spill will have short-term impacts on water quality, shellfish and, perhaps, mating for a few octopuses. County Executive Dow Constantine has called for an investigation.

"When you look across Puget Sound you have death by a thousand cuts," said Josh Baldi, policy adviser with the state Department of Ecology. "This happens to be one pretty large cut."

Still, most of the organic matter will dissipate and be used during the Sound's biological processes. And the biggest concern — the viruses and pathogens normally killed by treatment-plant disinfectants — probably didn't survive long.

"The bacteria are coming mostly out of our guts and they like to live at 98.6 degrees," said Randy Shuman, a water-quality scientist with King County. "The Sound is very salty and cold; they're going to die very quickly."

Rob Duff, who runs Ecology's environmental assessment program, added, "It's safe to say this won't be a long-term issue like some other stuff."

Oil, on the other hand, clumps near the water's surface — an ecologically sensitive zone — and contains carcinogens.

"Oil's effect is much more toxic, by orders of magnitude," Shuman said.

Scientists these days can measure even trace amounts of foreign substances in marine waters. At this time of year, Keil and his group at UW notice measurable upticks in water samples of everything from rosemary and thyme to vanilla and cinnamon, all making their way to saltwater through human waste.

But the most troubling pollutants don't need raw sewage to get into Puget Sound and spark havoc. And many don't get there by accident or even illegally.

Among the most disturbing ingredients of wastewater for fish and other creatures are the antibiotics and hormones that people flush down sinks and toilets. Those are rarely effectively stopped by treatment plants and can alter how fish and other creatures reproduce and feed.

Equally concerning are heavy metals: mercury, copper, lead, zinc and others. But the amount of those that make it to the Sound through sewage annually ranges from a few pounds, for mercury, to a few thousand pounds for lead.

The amount flushing into inlets through storm drains is exponentially higher. A recent toxics study by the state showed more than 500 metric tons of lead and 1,300 metric tons of zinc are coming into the Sound through stormwater every year.

The untreated waste from Monday's accident certainly would be significantly higher in nitrogen, which can contribute to fish-killing low-oxygen zones like the one in Hood Canal.

But nitrogen levels in the fully treated and disinfected wastewater that gets dumped from dozens of community sewage plants around the Sound are only two or three times lower than the nitrogen in raw sewage, said Ecology scientist Mindy Roberts. The amount of that treated wastewater that gets dumped into the Sound each day: about 400 million gallons.

Currently Ecology is in the early stages of trying to figure out how many oxygen problems exist in pockets up and down the Sound — not just in Hood Canal — and whether they are caused in part by human waste that makes its way into waters legally.

"We don't yet have enough information," said Roberts.

Craig Welch: 206-464-2093 or cwelch@seattletimes.com