Pioneer was selected as the number one design contractor for the Streamside Tailings Operable Unit (SST OU) Remedial Actions (RAs) being conducted by the DEQ. Completion of the SST OU RAs will address past adverse impacts to Silver Bow Creek and its floodplain cast by past mining activities in the region. Silver Bow Creek originates in Butte, Montana, and flows approximately 24 miles through Silver Bow and Deer Lodge Counties, Montana, to the Warm Springs Ponds to become one of the tributaries to the Clark Fork River. The SST OU comprises approximately 4,000,000 cubic yards of fluvially deposited tailings covering approximately 1,600 acres of the Silver Bow Creek floodplain.
The RAs include excavation and disposal of tailings in a regional repository, total reconstruction of the stream channel and floodplain, revegetation and coordination with Natural Resource Damage restoration actions also being conducted by the State of Montana. To-date Pioneer has performed the following work for the SST OU project:
- Completed design and managed construction for removal of 107,000 cubic yards of tailings covering 53.3 acres for the Parcel 152 Project. The viability and economy of field-directed additional removal based on statistics-based X-Ray Fluorescence (XRF) field screening techniques developed by Pioneer were proven during this project.
- Completed design and is currently managing construction for the SST OU Subarea 4 Phase 1 RA Project that includes removal of 289,000 cubic yards of tailings covering 189 acres. This project included design and construction of a semi-permanent 5.3-mile long haul road designed to accommodate transportation of up to 2 million cubic yards of tailings using 60-ton capacity haul trucks. The haul road includes a highway underpass, two bridges, railroad protection and coordination, at-grade road crossings, and innovative construction methods across wetland and poor subgrade areas. Haul road construction was completed in December 2004, and tailings excavation will be complete in spring 2005.
- Completed tailings investigation and currently designing SST OU Subarea 4 Phase 2 RAs that will include extension of the haul road constructed for the Phase 1 RAs and excavation of 310,000 cubic yards of tailings covering 40 acres. This project will include detailed dewatering and stream diversion design necessary to complete removal of saturated tailings.
- Assisted DEQ with QA testing for RAs being conducted in Subareas 1 and 2.
- Completed tailings investigation for planned future RAs at the historic Nissler Wetlands in SST OU Subarea 1.
- Pioneer developed a statistics-based XRF field screening protocol that reduces characterization costs and facilitates accurate field screening of removal areas. This method facilitated a reduction of the over-excavation safety factor that reduced the volume of tailings to be excavated, saves a greater volume of underlying native soils suitable for revegetation, both of which provide substantial cost savings and reduce adverse impacts to borrow source areas.
Pioneer prepared a Design Development Report for Subarea 4 at the SST OU which detailed a four-year plan to accelerate the overall SST OU RA schedule while saving money, reducing need for vegetative backfill materials, reducing or eliminating in-situ treatment areas with project cost savings of approximately 2.3 million dollars.