WHAT'S HAPPENING NOW WITH THE CLEANUP?

CONSTRUCTION COMPLETED:  December 2025

PRELIM TOTAL COST:  $5.6 million (incl. monitoring, maint, reveg, etc.)

NEXT STEPS:  Complete new wetlands on east side of site

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LOCATION & DESCRIPTION:  (See cleanup design & related docs HERE.)

A 40-acre site ~10 miles south of Deer Lodge to the east of Racetrack Pond, running 2.2 river miles SW to NE beginning just north of Gemback Road. 

CHARACTERISTICS:

Relative to other phases, the Strategic Plan characterized Ph. 7 as "Moderate Priority" for erosion of contaminated sediments into the river; and "High Priority" for contaminated soil levels, as the area includes a public fishing access (pp.11-12). DEQ estimated removal of 135,800 cubic yards of mine waste-contaminated material from the site.

STATUS (as of July 2026)

Construction was completed in Dec. 2025, and the parking lot, stated-owned portions of the floodplain, and the river are now open to the public. (If you visit, please do not trespass on private property and be aware of tripping hazards.) The project cost ~$5.6 million, including construction, engineering, revegetation, streambank material, and surveying. This total is over original estimates, as more contaminated material needed to be removed (173,250 cubic yards total), which also required more backfill.  NEXT STEPS: As of July 2026 DEQ had completed some minor repairs to revegetated areas. A new wetlands feature on the east side of the site (which will reclaim some borrow areas and provide diverse waterfowl habitat in the area) will be completed by the end of 2026. CFRTAC reviewed and provided input on the wetland design, and the site was part of a public tour of Ph 7, on June 16, 2026. 

Learn more about the wetland design (plus lessons learned from the overall cleanup thus far) in our June 2026 newsletter. See our comments on Ph.7 design here, the State's response to comments here, and more info on Ph.7 in our February and May 2025 newsletters.  

ESTIMATED START DATE:  2027 

ESTIMATED TOTAL COST:   $20.62M (may change) 

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LOCATION & DESCRIPTION: 

Includes Arrowstone Park. Extends through Deer Lodge from the I-90 bridge at Exit 187 (eastbound) north to the city's boundary with Grant Kohrs Ranch (near the Cottonwood Creek confluence).  

CHARACTERISTICS:

This phase is of high concern because temporary soil caps installed ~30 years ago at Arrowstone Park are failing in some areas, exposing arsenic and other contaminants that have created public health risks. Community concern led DEQ to prioritize cleanup here. In the interim, DEQ installed safety signage and added temporary soil caps on bare spots to cover exposed toxic contaminants. Please use caution at the park, avoid exposed soils (especially river banks), and wash hands, boots, pets, boats, etc. after any potential exposure.

STATUS  (as of July 2026):

Additional sampling was completed at the site in June and July 2026 to fill data gaps. This included: 1) Geoprobe Sampling to examine soils at greater depth in some areas, and to sample areas that DEQ previously could not access; 2) Surface Soil Sampling in some areas to collect more current data; to better factor in current use of the park (to ensure focus is on the highest-use areas); and to apply more up-to-date sampling methodologies than were used previously; and 3) Opportunistic Sampling in areas of known or suspected slickens to help ensure maximum protection of human health.

This sampling data is now being applied to a re-started cleanup design process, guiding decisions on contamination removal boundaries and depths. 

CFRTAC will provide input into the cleanup design by participating in the agencies' Remedial Design Meetings, beginning in summer 2026.

NEXT UP AFTER PHASE 7 and PHASES 13/14 (described above):

• Phase 8/9:  (Located between the north boundary of Phase 7 -- about 1/3 mile north of Racetrack Pond -- and Sager Lane.) The 2023 Strategic Plan rated this stretch as Moderate Priority for erosion of tailings and volume of contamination. Phase 8/9 has already been sampled, though additional sampling may be required. Cleanup remedial design may begin in 2027, or may follow work on Phases 10-12 - see below.

• Phases 10-12: (Located between Sager Lane and the I-90 bridge on the south end of Deer Lodge.) According to the 2023 Strategic Plan, these phases have high volumes of contamination, are at the "highest" risk of tailings eroding into the river, and pose "the most acute risk to aquatic habitat." They are therefore ranked high priority in the plan. These phases are combined as they share haul roads, which are all accessed from Sager Lane. As of July 2026 the sampling plan for these phases is underway -- these will require State and EPA approval. Cleanup remedial design is estimated to begin in 2027, though it is possible work on Phase 8/9 will occur first.

Phases 7 and 10-14 (described above) were prioritized for cleanup based on the ranking criteria described on p. 12 of the 2023 Strategic Plan. According to the schedule included in the plan, other phases will be addressed in an upstream-to-downstream sequence after these higher-priority phases are completed. (The sequence of cleanup may change as the plan is updated.) These include:

• Phase 4B:  Estimated to start in 2029. Phase 4A was completed in 2023. 

• Phases 17 - 22: To be completed in order after Phases 8 & 9, with some possibly being combined. At roughly one phase per year, (with Phase 17 A & B taking a year apiece), annual start dates will be from 2032 to 2038.

• Maintenance and monitoring for completed phases is ongoing. The Strategic Plan estimates this work will continue beyond construction of the final phase from 2040 through 2044.