Factsheet: What to Know About the EPA’s Proposed Plan for Addressing Lead in Residential Soils
Butte Priority Soils Operable Unit, Butte, MT, June 2026
On June 1, 2026, the U.S. Environmental Protection Agency Butte Priority Soils Operable Unit, Butte, MT June 2026 (EPA) released a Proposed Plan for changes to the existing cleanup level for lead in residential soils and interior dust at the Butte Priority Soils Operable Unit (BPSOU) of the Silver Bow Creek/Butte Area Superfund Site. We encourage interested residents to read the Proposed Plan and attend the public meeting (06/16). The Butte community and all interested stakeholders are also invited to submit written comments during the 30-day public comment period, which will run through June 30, 2026.
Existing BPSOU Boundary and Proposed Modification
- Existing BPSOU Boundary
- 4,265 acres
- 4,700 households
- Proposed BPSOU Modification
- 3,637 additional acres
- 7,100 additional households
Proposed Changes
Lower Cleanup Level for Lead in Residential Soils and interior dust The EPA proposes to lower the BPSOU-specific cleanup level for lead in residential soils and interior dust from 1,200 mg/kg (which is equivalent to parts per million) to 456 mg/kg.
Expand the BPSOU Boundary
The EPA proposes to expand the current BPSOU boundary to incorporate densely populated residential neighborhoods impacted by historic mining operations in Butte. Properties within the expanded BPSOU boundary (see map) will need to be sampled and evaluated for contamination to determine if remedial action is necessary.
Update the Timeline for Cleanup
The EPA expects that sampling, evaluation, and necessary remedial action will take a total of 15 years from 2026. Sampling, evaluation, and any necessary remedial action will prioritize the most vulnerable populations.
EPA’s National Lead Directive Prompts BPSOU Cleanup Changes
In October 2025, the EPA released a new Directive for residential soil cleanups at Superfund sites. This Directive updated EPA’s 1994 Lead Guidance, established a standardized screening level of 200 mg/kg soil-lead, and lowered the target blood-lead level from 10 micrograms per deciliter (µg/ dL) to 5 µg/dL. While the EPA acknowledges there is no known safe level of lead in blood, the 5 µg/dL blood lead target is used to prioritize resources to protect children from the highest, most immediate hazards addressable under CERCLA. The EPA will continue to work with the Butte-Silver Bow Health Department and WIC to prioritize the sampling of those residences where there is a resident with an elevated blood lead level.
The proposed changes in this 2026 Proposed Plan only modify the component of the BPSOU Selected Remedy that addresses contaminated residential soils and interior dust, consistent with the new blood lead level target established in EPA’s 2025 Directive, to ensure protection of human health and the environment within the BPSOU. The 2025 Directive also recognizes that layers of protection, such as institutional controls and informational devices, enhance the effectiveness of response actions.