Confidential, Environmental Services

Client: Confidential

Year: 2024 - 2025

Location: Portland, Oregon

Features:

  • Groundwater sampling and analysis

  • Vertical delineation of nitrate contamination

  • Wet mining impact assessment

  • Regulatory compliance support

  • Preparation of reports for DEQ approval

Project Summary

Knife River retained Central Engineering Services (CES) to evaluate nitrate contamination at their site and to assess potential impacts from wet mining operations. Through phased investigations and strategic sampling efforts, CES provided critical data to guide remediation planning and regulatory compliance. CES's expertise in environmental site assessments and regulatory coordination was instrumental in supporting Knife River’s operational goals while ensuring environmental stewardship.

Scope of Work:
CES conducted multiple rounds of groundwater sampling to establish baseline conditions and evaluate nitrate stratification within the subsurface. Depth-discrete groundwater samples were collected from monitoring wells to determine vertical variation in contamination. Additionally, CES performed an exploratory phase involving the excavation of test pits, where soil and groundwater samples were analyzed to identify areas of higher nitrate concentrations. In collaboration with Knife River, CES designed and executed a wet mining simulation, which included installing monitoring wells in the identified areas of concern and collecting samples over time to assess changes in nitrate levels. The findings from these efforts were documented to support the regulatory closure process.

Features:

  • Conducted groundwater sampling at multiple intervals to monitor nitrate concentrations.

  • Excavated and analyzed test pits to delineate contamination and identify areas of concern.

  • Installed monitoring wells in critical areas to collect baseline data before initiating wet mining simulations.

  • Carried out wet mining simulation to evaluate potential impacts on groundwater quality.

  • Coordinated with regulatory agencies to prepare comprehensive reports and secure approvals.

Results:
The investigation revealed that nitrate concentrations remained consistent with depth, indicating limited vertical migration of contaminants. The test pit analysis identified the highest nitrate concentrations near Test Pit #2, with levels reaching approximately 18 mg/L. Findings from the wet mining simulation demonstrated that excavation activities did not result in significant changes to nitrate concentrations in groundwater, providing critical data to support future mining operations. Based on these results, CES prepared a Voluntary Cleanup Program (VCP) report and submitted it for DEQ approval, with the goal of obtaining a Comfort Letter for regulatory closure.