Brownfield Development – Kent, WA
CRETE is led the site investigation, waste profiling, permitting, design and construction oversight for the cleanup of a secondary aluminum smelter site in Kent, WA. Maralco Aluminum operated from 1980 to 1986 when the property was abandoned and over 30,000 cubic yards (cy) of waste from smelting activities was abandoned on site.
The majority of the waste was concentrated in a large stockpile stored outside with limited covering. Contamination migrated from the source material to site soils, groundwater, and sediment.
A wetland was located adjacent to the stockpiled waste, in the center of the property, which flowed to the King County Drainage District ditch system.
Work Performed
- Excavation and off site disposal of over 35,000 tons of waste material. CRETE successfully tested waste to avoid hazardous waste classification, which reduced landfill costs.
- Work was done as a two phase interim action under the Washington Department of Ecology (Ecology) Model Toxics Control Act (MTCA) to facilitate an expedited cleanup and development schedule.
- Work was planned in separate phases to allow for acceleration of main source removal followed by more surgical sediment removal.
Value Added
- Waste was direct loaded into waiting transfer containers using a conveyor belt transfer system. This minimized the handling of the waste and reduced the amount of cross contamination and the amount of decontamination required.
- Air samples were collected during construction to document that no fugitive dust was generated during construction activities
- The removal extent within in the stockpiled area was determined ahead of construction using soil borings, hand augers, and surface grab samples advanced through the source material. This eliminated additional sampling and down time waiting on results during construction.
- The interim action removed waste and soil above conservative screening levels. The cleanup action was completed per Washington Administrative Code (WAC) Part 173-340. The interim action adhered to the requirements in subpart 380 and 400.