Our projects: Engineering sustainable solutions across industries.

The BRW Smelter Area Mine Waste Remediation and Contaminated Groundwater Hydraulic Control is in Butte, Montana. Historically, the Site included several different smelting and other industrial operations. These operations left behind a complex distribution of materials (including slag, tailings, demolition debris, foundations, and other historical structures), impacted soil, and groundwater.

Since 2017, Pioneer has collected information needed to refine the characterization of groundwater and solid materials within the Butte Reduction Works (BRW) Site. We completed detailed sampling plans outlining the scope of the field activities, sampling procedures and protocols, quality assurance/quality control procedures, and Site-specific health and safety hazards followed by multiple Site investigations, which included:

• Drilling approximately 100 boreholes and excavating approximately 60 test pits, documenting lithology (including field X-ray fluorescence screening), and collecting soil samples for metals and hydrocarbon analyses.
• Performing two aquifer pumping tests to support development of a groundwater model and hydraulic control design. Installing 52 piezometers (in existing boreholes) to periodically measure groundwater elevations, collect field data (water temperature, pH, conductivity, etc.), and collect groundwater samples for metals and hydrocarbon analyses.
• Collecting monthly surface water samples from upstream, adjacent, and downstream of the Site for 8 consecutive months.

We compiled all the data into a Microsoft Access database specific to the project. Laboratory data underwent Stage 4 or Stage 2A data validation. From the evaluation, we prepared comprehensive Data Summary Reports comparing the data to the Data Quality Objectives in the original sampling plans and qualifying the data based on these Data Quality Objectives criteria.

Pioneer is currently using the data obtained from these Site investigations to guide remedy design and implementation activities.

‍Geotechnical and Geophysical Site Investigations

As a result of the various past operations at the Site, various structures and materials within the Site must be considered when developing the remedy design. We completed multiple geotechnical and geophysical Site investigations to gather additional geotechnical information on the structures and materials within the Site, which included:

• Conducting a seismic, geophysical investigation of the Site to confirm the existence and location of a subsurface flume(s)/culvert(s). This included completing Multichannel Analysis of Surface Waves surveys along three separate transects within the Site, creating velocity profiles along the three transects, and using the relative difference in measured velocity between materials to identify the flume(s)/culvert(s) and other void spaces.
• Drilling 12 boreholes and collecting geotechnical samples according to the prepared sampling plan. This included interpreting the laboratory results and performing analyses for slope stability, bridge stability, and consolidation.
• Collecting train-induced vibration data on the rail line located south of the Site and using these data to evaluate the effects of train passage on the stability of the proposed excavation slope.

Soil and Groundwater Modeling

We organized, analyzed and compiled lithology and chemistry data at the Site into a three-dimensional statistical model of Site materials using Leapfrog Works software to interpolate and visualize the different material layers and delineate the extent, magnitude, and volume of waste within the Site. The Leapfrog Works model enhances the understanding of subsurface conditions and is a powerful tool to evaluate waste removal boundaries.

Site remediation includes designing a subsurface hydraulic control system to control discharge of metals-impacted groundwater to surface water and sediment. We organized groundwater data into a conceptual Site model, which we then used to develop a MODFLOW numerical flow model. The model is calibrated to Site conditions and allows multi-year simulations of design and construction scenarios.

Pioneer recently concluded a comprehensive geotechnical drilling investigation and performed the foundation design for a new 4-story structural steel building, poised at the former mall location in Helena. The project faced a challenge as the team unearthed uncontrolled fill material, a remnant from the demolished mall structure. Further complicating the site conditions, laboratory analysis of consolidation tests indicated that the subgrade soil was prone to significant collapse when saturated. To address these challenges, Pioneer's design incorporated the use of rammed aggregate piers. This innovative technique was instrumental in stabilizing both the uncontrolled fill and the native subgrade soil, significantly mitigating the risk of settlement. In addition to the design phase, Pioneer meticulously oversaw the on-site quality assurance during the installation of the rammed aggregate piers, ensuring the intent of the design was met.

Near Helena, Montana, Pickly Pear Creek was contaminated after a century's worth of smelter activities deposited arsenic, lead, and other containments into its soil and groundwater. A 5-year cleanup solution included lowering the groundwater and restoring the creek to its natural channel. This included moving over a million cubic yards of materials.

FIDIC - 2019 International Merit Award

ACEC - 2019 Grand National and Montana Engineering Excellence Awards.

Montana Contractors Association - Special Recognition Excellence Awards for Water Quality and Habitat Restoration.

Since 2011, Pioneer has provided a full range of planning, data collection, environmental permitting, remedial design, project management, construction management, and monitoring services at the East Helena Smelter Resource Conservation and Recovery Act Site to support corrective measures implemented to remediate contaminated soil and groundwater at the site. The project removed a derelict dam and impacted reservoir sediments and then relocated approximately 1.25 miles of Prickly Pear Creek and its floodplain to the eastern margin of the site. These actions permanently lowered groundwater beneath the entire site and reduced groundwater flux through inaccessible contaminated soils which reduced contributions to the contaminated groundwater plume without long-term pumping.

Pioneer completed the following major activities:

• Collected baseline stream, wetland, and soils data to support, permitting and design.
• The creek relocation project disturbed approximately 45 acres of jurisdictional wetlands and over a mile of existing stream channel. Pioneer led the complicated permitting effort that included multiple joint applications, letter and conditional letter of map revision elements, floodplain permits, and a full range of other environmental permits.
• Designed the stream channel and floodplain to replace all wetland losses with functions and values (FEWA) that meet or exceed the pre-project conditions.
• Designed the stream and floodplain to provide the desired hydraulic controls for the site ground water remedy and to deliver materials for the final plant site cap.
• Finalized the design and mitigation plans, obtained all permits, solicited, awarded, managed and completed the construction contract.
• Construction was completed in July 2017 and Pioneer is currently performing monitoring and maintenance activities at the site.

Scope of Work

‍As part of the Powell County Modernization project, Pioneer performed detailed survey, structure inventory, and site visits on the Clark Fork, Blackfoot, and Little Blackfoot Rivers and their tributaries. This work included hydraulic structure survey of 105 hydraulic structures, bathymetric channel crosssection survey at 182 channel locations and survey of reference marks at 8United States Geological Survey (USGS) gaging stations. Structure Inventories of 74 stream spanning structures were performed. A total of 66 site visits were performed. All survey tasks and data acquisition were performed in accordance with FEMA and DNRC guidance standards.

‍Project Performance

‍Results of the survey tasks were compiled into a report and submitted to DNRC and FEMA. The project was completed on schedule and within the original budget.

‍Knowledge Enhancement & Lessons Learned

‍In the Global Positioning System (GPS) structure survey work early stages, field data was uploaded daily for engineering QA/QC and to expedite the development of structure drawings in AutoCAD. The QA/QC team members realized that field crews were collecting more survey points than needed to define the required bridge and culvert elements for modeling. These additional points were slowing both QA/QC and drafting efforts. In response, Pioneer developed a more concise and standardized list of required survey points and relayed the information to the survey field team. This updated method was used for the remainder of the GPS survey data acquisition and increased the efficiency of the survey field team, the QA/QC process, and the hydraulic engineering team.

The Coronado National Forest is a United States National Forest that includes an area of about 1.78 million acres spread throughout mountain ranges in southeastern Arizona and southwestern New Mexico. Under CERCLA, officials developed an environmental cleanup plan for the abandoned Harshaw Creek Mines Sites within the forest.

With a redesign required of the Marstellar Consolidation Cell to accommodate more waste, the Pioneer Team worked closely with the Forest Service to develop alternate plans and implement the preferred alternative.  At the Endless Chain Waste Rock site, more waste was consolidated in place than planned and the site was redesigned to accommodate the change.

To remediate the Upper Harshaw Creek Mines in the Coronado National Forest, Santa Cruz County, Arizona, the Pioneer Team implemented a Forest Service design to reclaim historic mine waste at these sites.

Remediation work involved:

• Construction of three separate, on-site consolidation cells for disposal of waste.
• Removal of over 78,000 cubic yards of contaminated waste rock and tailings from five abandoned mines: the Marstellar, Augusta, Blue Nose, Endless Chain, and Morning Glory Mine sites.
• Collection of confirmation samples from waste rock removal areas and use of field-portable X-Ray Fluorescence testing to ensure that cleanup levels for arsenic and lead were achieved at each location.
• Cover material placing over the consolidation cells.
• Road building, reclamation, channel construction, adit and shaft closure work.

Oversight work required before and after surveys to calculate waste volumes and provide as-built drawings.  Density testing was conducted within the consolidation cells to verify proper compaction.

Due to unforeseen conditions, the Pioneer team had to employ an adaptive approach to accommodate rock excavation in the consolidation cells and significant increases in waste volumes (over 56%).  By working closely with the Forest Service we were able to overcome these challenges and complete all work within the required project timeline.

Work was completed at the Marstellar, Augusta, and Blue Nose sites in early March 2021. Construction on the Endless Chain and Morning Glory sites was completed in December 2021.