Remediation and Source Control at an Aluminum Extruding and Anodizing Facility

The client’s industrial facility is located on 5 acres of the Columbia Slough, just over a mile from the Columbia River. Two settling ponds that were installed for the treatment of operational wastewater before discharge to the slough were used until the mid-1980s. The ponds were excavated, backfilled, and covered with asphalt.

In 1997, the DEQ reviewed information for all properties in the Columbia Slough area and opened up this site for further investigation. During a Phase II environmental site assessment, a layer of residual sludge was found near the bottom of one of the former ponds. Further investigation found links between the wastewater-pond’s residual sludge, high pH in soils, and elevated metal concentrations in the groundwater surrounding the pond. The DEQ was concerned about the potential for metals in the groundwater impacting the adjacent Columbia Slough. 

MFA was engaged to assist with remediation of the site. The remedial action included excavation of aluminum sludge from the bottom of the historical settling pond; removal of high-pH soils; pH screening during excavation to assess whether soil at progressive elevations fell below the screening limit; backfilling the excavation; adding MetaFix™ soil amendment in the configuration of a treatment wall on the groundwater-downgradient side of the excavation; and transporting the impacted material off site for disposal. The depth of the soil that had to be removed, combined with space constraints at the site, required sheet pile shoring to support excavation walls and provide stability to nearby buildings and structures. MFA oversaw the subcontractors implementing the shoring system and conducting the removal and backfill. Landscaping enhancements were also made along the bank of the Columbia Slough consistent with City of Portland tree-planting and erosion-control requirements.

MFA assisted the client with National Pollutant Discharge Elimination System permit compliance, stormwater sampling, development of stormwater management plans, stormwater collection / conveyance system design, stormwater quality treatment system design, and compliance reporting to state and local agencies. MFA also assisted with evaluation and development of best management practices, including filtered catch basins, traps in catch basins, piping roof runoff to a water quality treatment system, and using a media/sand filter stormwater quality treatment system.

MFA monitored the effectiveness of the remediation as well as stormwater system upgrades and treatment, performed a stormwater mass loading evaluation, and received a source control decision from the DEQ in 2019 and a conditional No Further Action (NFA) determination in 2020.