THE DIRT: Completion of Priority Cleanup Activities in the Ninemile Basin

All priority cleanup activities in the East Fork Ninemile (EFNM) Basin have been successfully completed, marking a significant milestone in environmental cleanup efforts. The EFNM Waste Consolidation Area (WCA) has reached capacity, and final closure activities are now underway. As this phase concludes, monitoring efforts will continue to assess the effectiveness of the remedial actions.

The Ninemile watershed, located near Wallace, Idaho, spans approximately 12 square miles, with Ninemile Creek extending 7 miles from its confluence with the South Fork Coeur d’Alene River (SFCDR) to the EFNM Creek headwaters. This area has been significantly impacted by historical mining activities dating back to the late 1800s, which introduced elevated metal concentrations into sediments, soil, and water.

In 2012, the Interim Record of Decision Amendment (RODA) identified 36 legacy mining sites contributing to metal contamination in the Ninemile Basin. These sources included waste rock dumps, mine workings, fill areas, and jig tailings piles. Initial, limited cleanup efforts by the Coeur d’Alene Tribe and Idaho Department of Environmental Quality (DEQ) began in the 1990s, followed by remediation of the Rex No.2/Sixteen-to-One Mine between 2002 and 2007. In 2014, the Coeur d’Alene Trust launched extensive remedial actions (RAs) in line with the work outlined in the RODA. Through an adaptive management approach, the U.S. Environmental Protection Agency (EPA) collaborated with stakeholders to prioritize and implement RAs across the Upper Basin, with the Ninemile Basin designated as an initial focus area due to its significant contribution of dissolved and particulate metals to area waterbodies

Since 2014, cleanup work in the EFNM Basin has been ongoing. These efforts included the design and development of the WCA and remediation of major sites such as the Interstate Callahan rock dumps, Success Complex, Interstate Millsite, Lower EFNM Creek, Tamarack Complex, and Dayrock Complex. In total, approximately 1,545,000 cubic yards of waste were excavated and hauled to the EFNM WCA for placement and compaction, and approximately 15,000 linear feet of stream were reconstructed. The EFNM WCA generated approximately 350,000 cubic yards of rock and 375,000 cubic yards of soil for the Ninemile Basin remedial actions. The EFNM WCA’s strategic location near contamination sources resulted in an estimated $8.5 million in transportation cost savings while minimizing traffic disruptions to local communities. By late 2024, the EFNM WCA reached capacity, and final cover design was completed. Construction of the final cover system is anticipated for completion in 2025 and 2026, signifying the culmination of key cleanup efforts.

To ensure the long-term success of these remedial actions, the Basin Environmental Monitoring Plan (BEMP) was developed in accordance with the 2002 ROD and 2012 RODA. The BEMP provides a framework for assessing the effectiveness of cleanup activities, guiding the collection, analysis, and interpretation of environmental data. In the Ninemile Basin, RA effectiveness monitoring will evaluate progress toward remediation objectives, including water quality improvements and ecological responses. Monitoring efforts, which will continue for at least five years, will determine whether performance goals have been met. If goals are achieved, monitoring will transition to a site-wide program; if not, further assessments will be conducted to identify additional recommendations for achieving long-term environmental objectives in the Ninemile Basin.

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.