Potential floods, potential contamination
Photo by CHANSE WATSON The slough just east of the Cataldo Mission is one of the area’s most contaminated floodplain locations. As the flood waters pour into the slough, the toxic heavy metals from the soil are redeposited to the bottom of the marshy area.
What was set to be a fairly normal flood season for the Silver Valley may have gotten a little more interesting after last week’s snow storm.
According the local snowpack telemetry (SNOTEL) sites, Shoshone County is currently 28 percent above the yearly average snowpack for the area.
Ed Moreen, a project manager with the Environmental Protection Agency, spoke about how the increased snowpack could lead to flooding, but there are a lot of factors that all have to come into play.
“The SNOTEL sites are now showing above average snow water equivalent for the Coeur d’Alene Basin,” Moreen said. “The more snow in the mountains, the greater the probability of flooding, but it all depends on timing, temperatures, precipitation and snow pack at the time of runoff.”
But it isn’t just the higher than normal water levels that are cause for concern…
Once these snowpacks melt and the (usually inevitable) flood waters rise, the water will carry with it a lot of the toxic heavy metals that are present within the soil of the surrounding hillsides and floodplains.
Moreen is then charged with boarding a boat and going out on the raging floodwaters and monitoring the water and how it disperses the toxic particles.
In 2017, boat-based monitoring displayed a significant increase in heavy metals (lead, zinc, copper, etc.) concentrations in the Coeur d’Alene River beginning in the Dudley Reach (just downstream of the Cataldo Boat Launch).
The extent of the elevated heavy metals concentrations extended all the way to Lake Coeur d’Alene.
During flood events like the one that occurred in March of last year, flooding dispersed heavy metals out into the floodplain and lateral lakes in addition to the large volumes conveyed further down in the Coeur d’Alene River and to Lake Coeur d’Alene.
These floods make it difficult for groups like the EPA to maintain the work they accomplish during their cleanup efforts, as the flood waters carry the concentrated metals over previously cleaned areas before the water recedes and the metals settle back into the clean soil.
This creates an unsafe environment for both humans and wildlife.
“Our greatest concern is where people are getting exposed to those metals because it’s over such a large area and gets replenished in events such as March 2017,” Moreen said. “Continued distribution or redistribution of sediments containing high concentrations of heavy metals also impacts the ecosystem system significantly contributing to waterfowl and wildlife mortality, as well as impacting food sources such as aquatic insects that are important in the food web.”