Sewer Monster?

by KEVIN TAYLOR & r & & r & & lt;span class= & quot;dropcap & quot; & S & lt;/span & o if someone dumps a big load of crap over the aquifer in Post Falls, when should you worry about pulling a glass of water in Spokane? & r & & r & Chill. There's plenty of time.

In fact, you could put down this paper, run off and join the Army, serve a couple of tours in Iraq, get out and start a family. Yeah, that much time.

"From our wells, it's a 10-year time of travel," from the area around Rathdrum and Post Falls in North Idaho to Spokane water faucets, says Lloyd Brewer, Environmental Programs Manager for the City of Spokane.

"It's definitely a slow process ... it's not like the flow of a river, it's more like creeping along. Moving on the order of a few feet per day is pretty rapid for an aquifer," says John Monks, a Sandpoint-based hydrogeologist with Golder Associates who has been hired to investigate the sewage spill earlier this month in Post Falls.

Leaking at a new lift station, the spill went undetected from Aug. 8-11. An alarm system wasn't working so it is unclear exactly how long untreated wastewater was leaking that weekend, Post Falls Public Works Director Terry Werner says.

Worst-case estimates pencil out to 200,000 gallons, of which, Werner says, 105,000 gallons were captured in retention structures on-site.

"So basically there's 95,000 gallons, worst-case," Werner says. That's still enough wastewater -- and associated bacteria, viruses, nitrates and other chemicals -- to create a big stink about the safety of the aquifer that provides drinking water for nearly 600,000 people, mainly in Spokane and Kootenai counties.

The lift station is on the western edge of Post Falls north of Interstate 90. This is nearly three miles from the Spokane River, and contaminants are unlikely to get there, Werner says.

The aquifer, meanwhile, is some 200 feet below the spill site, Werner estimates, basing his calculation on the 195 feet that Post Falls had to drill for a new water well near Cabela's, about two miles west of the spill.

This new well will be the canary in the coal-mine. Any contamination that reaches the aquifer is likely to show up in this well first.

Monks, who regularly investigates spills above the aquifer, says he is creating a computer model to predict the flow of as many as 130,000 gallons of spilled sewage.

This sounds terrible, he says, but every single day an estimated 14 million gallons of sewage (23 cubic feet per second, according to USGS reports) flow to the aquifer from septic systems.

And this sounds really terrible except that every single day 948 million gallons (1,468 cubic feet per second) flow through the aquifer.

"It's not a good thing when these things happen," Monks says of the sewage spills, "but nonetheless ... it is a drop in the bucket. In my experience, spills of this volume tend to be diluted fairly rapidly as they move down-gradient."

The aquifer's high volume does not mean high velocity.

"The trick is it's pretty fast for an aquifer ... but it's still an aquifer," says Spokane's Brewer. "It still takes a fair amount of time for the water to move," through sand and gravel.

The sands and gravels also filter out many bacteria and viruses. Chemicals such as nitrates migrate more easily with the water ... but set off few warning bells as far downstream as Spokane.

"My sense of it right now is that (the spill) might have the potential of changing the characteristics of the aquifer in the amount of chloride one might measure or the amount of nitrate one might measure at a particular location. But that will drop the farther away you get -- basically it's getting diluted in the aquifer," Brewer says. "And on the issue of bacteria ... I'd be surprised if any coliform bacteria showed up."