Tundra swans are dying again this year. Like they do every year.

Lured to the beautiful lower Coeur d’Alene basin’s waterways and wetlands for rest and food, the birds end up, quite literally, choked on sediments contaminated with lead. The lead, of course, is flushed downstream by flooding from the legacy of mining in the Silver Valley. Each spring runoff season brings a fresh coating of contamination. Each spring migration season brings 150 or more swan carcasses.

According to Idaho Fish and Game, this year’s late spring is causing the swans to stay over longer in the basin, which will likely lead to more mortality.  Lead poisoning is particularly hard on tundra swans because it shuts down their digestive systems, causing them to starve. Some 80% of the lower Coeur d’Alene wetlands are contaminated enough to be lethal to swans. More than 92% of swan deaths in the basin are due to contamination.

Recent data presented to a committee of the Basin Environmental Improvement Project Commission, the agency responsible for monitoring and guiding cleanup efforts, showed that, indeed, January flooding caused widespread contamination.

Typical runoff from the Upper Coeur d’Alene mining districts will deposit sediments with 2000 or 3000 parts per million of lead contamination downstream. In the high water flows from this past January, sediment deposits were more like 5000 parts per million. As the scientists explained, larger flows are moving more particles and bigger particles and thus spreading more contamination.

The most disturbing thing, however, is that the level of contamination that triggers cleanup action in the Basin is 530 parts per million. In other words, in every year, in every flood season, the lower Coeur d’Alene basin is contaminated beyond levels that are safe.

Regulators continue to consider final approval for the cleanup plan for the upper Coeur d’Alene basin, but it might still be years before there’s even a preliminary plan for the lower Coeur d’Alene. Unfortunately, it looks to be another couple of decades before this mess gets cleaned up and birds will be safe.