Late last week, we were forwarded an email from Greg Clark with the U.S. Geological Survey, whose team did some water monitoring during the flood event January 18th of this year. The monitoring in Harrison, where the Coeur d’Alene River flows into Coeur d’Alene Lake, shows that the conveyor belt of contamination from the upper basin to the lower basin was particularly bad during the flood this year.

According to Clark’s email, a measurement of the concentration of lead in the water at Harrison was the second highest ever recorded, the highest being a major flood in 1996. Also, the sample had the highest concentration of zinc and highest concentration of cadmium in more than 20 years. Clark said, “Based on these numbers, the load of lead delivered to the lake on January 18 alone was about 160 metric tons, or about 75% of the mean annual load of lead delivered to the lake during 2004 through 2009.” (Our emphasis.) However, Clark noted that sampling at the Lake’s outlet on January 20 was low, indicating that most of the lead settled to the lake bottom.

More disturbingly, however, is the measurement of flooding right before the peak. According to Clark, the river flow at Cataldo was higher than what was measured at the peak of the 2008 flood, but river the flow at Harrison was quite a bit lower. Clark says that this flow data indicates that a great deal of the water — and its accompanying sediment and metal contamination — was dumped into the lateral lakes along the lower basin. As Clark somewhat understated it in the email: “Obviously not good news as far as wildlife is concerned.”

Aerial photo of Coeur d'Alene River flooding at Harrison in 2008