Prickly Pear Creek Floodplain Reconstruction

Location: East Helena, MT
Project Type: Water Resource Management, Environmental

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

Current update:  Major site construction will be complete in fall 2016 and final site revegetation will be complete in spring 2017.  View a short video on the cleanup efforts here.

Since 2011, Pioneer has been providing a full range of data collection, environmental permitting, remedial design, project management, and construction management services for the East Helena Smelter Resource Conservation and Recovery Act (RCRA) site corrective measures. The project involves closing the site and remediating contaminated soil and groundwater associated with past smelting activities. Relocating and reconstructing approximately 6,000 linear feet of Prickly Pear Creek along the eastern margin of the site is a critical component of the remedy. The Pioneer-developed reconstructed creek design includes removing a derelict dam and impacted impoundment sediments, protecting the slag pile from future creek migration, and lowering the groundwater beneath the entire site to reduce groundwater flux through contaminated soils and associated transport of contaminants off the site via groundwater.

Tasks Pioneer completed include permitting, design, surveying, site assessments, and oversight:

  • Coordinated the complicated project permitting that required multiple joint applications, letter and conditional letter of map revision (LOMR and CLOMR) elements, floodplain permits, and a full range of other environmental permits. The creek relocation project disturbed approximately 45 acres of jurisdictional wetlands and over a mile of existing stream channel.
  • Designed the stream channel and floodplain to mitigate all wetland losses and create a stream channel, floodplain, and wetland complex with functions and values (FEWA) that meet or exceed the pre-project conditions.
  • Completed detailed wetland delineations/surveys and stream channel assessments to document existing conditions and to establish site-wide mitigation requirements.
  • Finalized the design and mitigation plans, obtained all permits, solicited and awarded a contract for construction activities, and started floodplain and creek reconstruction.
  • Coordinated the creek realignment project with other site cleanup activities.
  • Incorporated into the final design delivery of approximately 500,000 cubic yards of material from the floodplain reconstruction to cap the former smelter site.

 Project Dealt with

  • Stream Assessment
  • Wetlands Delineation
  • Wetland Mitigation Design
  • Wetland, Stream, and Environmental Permitting
  • Stream Channel, Floodplain, and Wetland Design
  • Project Coordination and Planning
  • Construction Contracting Management and Oversight