THE DIRT: Stormwater management in the Silver Valley

The Silver Valley has long been vulnerable to flooding during spring runoff, and one major disaster made clear how these events can threaten not only public safety but also the progress of environmental cleanup. The flooding event at Milo Creek in 1997 was especially significant, it not only caused widespread damage but also re-contaminated several properties that had already undergone remediation. In response, Milo Creek became the focus of a collaborative effort that led to major stormwater infrastructure upgrades. These upgrades were designed not just to mitigate flooding, but also to protect the integrity of past and future remediation efforts.

Following the improvements in Milo Creek, stormwater systems were enhanced throughout the Silver Valley, particularly in the large gulches that can carry massive volumes of runoff during major flood events. Most of these improvements focused on capturing stormwater and piping it directly into the South Fork of the Coeur d’Alene River to reduce the risk of localized flooding and erosion.

While redirecting stormwater away from flood-prone areas is beneficial, directly discharging it into the river raises serious concerns for water quality. As stormwater flows over roads, rooftops, parking lots, and other hard surfaces, it picks up a variety of pollutants—such as sediment, oil, grease, fertilizers, bacteria, and excess nutrients. When this untreated runoff enters the South Fork, it can degrade water quality, harm aquatic life, and contribute to nutrient loading. This nutrient pollution, especially phosphorus, can lead to algal blooms and low oxygen levels that damage ecosystems and impact water bodies all the way downstream to Coeur d’Alene Lake.

Recognizing the urgency of this issue, Governor Brad Little’s Leading Idaho Initiative has prioritized reducing nutrient loading in the Coeur d’Alene Lake watershed. Under this initiative, state funding has been allocated to support Kellogg’s stormwater improvement projects that address phosphorus and other contaminants found in runoff.

So far, three phases of stormwater projects have been completed or are underway. Each project is aimed at reducing the impact of stormwater through filtration and infiltration techniques that remove pollutants before they reach the river. Pilot projects have tested innovative approaches for slowing runoff and allowing it to soak into the ground. Treatment systems have been installed to capture and remove debris, sediment, and oil from the water. Infiltration swales throughout the city are also helping to reduce the volume of water that would otherwise flow directly into the river by allowing it to naturally infiltrate into the soil.

Once fully implemented, these efforts will treat approximately 75% of the stormwater in Kellogg. These projects represent a significant investment in both environmental protection and community resilience, helping ensure that the Silver Valley’s recovery from past contamination is protected for generations to come.

The Dirt is a series of informative articles focused on all aspects of cleanup efforts associated with the Bunker Hill Superfund Site. Our goal is to promote community awareness of contamination issues, to provide tools for protecting public health, and to keep the community informed of current and future cleanup projects. The Dirt is a group of committed and local experts from multiple agencies including the Basin Environmental Improvement Project Commission, Panhandle Health District, Shoshone County, Silver Valley Economic Development Corporation, and the Idaho Department of Environmental Quality.