Metro South

Scope of Work:

Metro, the regional government for the Portland Metropolitan area, is considering the development of a new, state-of-the-art Waste Transfer Center for the greater Portland area. The goal of the facility would be to create a full-service Materials Transfer Center and Household Hazardous Waste Facility that will be able to keep up with the region’s growth in population, increase in consumption, and increased public demand for recycling options. In 2020, Metro was most strongly considering an approximately 26-acre site in Clackamas Oregon that has been used as an aggregate quarry since the early 1960’s.

Generally, the site consisted of an aggregation of excavation cells up to 100 feet deep that have been backfilled with undocumented material from unknown sources. In addition, the site harbored open excavation pits, stockpiles, and an active mining operation.  Anticipating a complex and challenging project from a geotechnical perspective, Metro turned to Central Geotechnical Services to perform a Preliminary Geotechnical Investigation to assess the feasibility of the site for development.

Our investigation consisted of an examination of historical documentation and aerial photography, geotechnical drilling, laboratory testing, and the installation of piezometer monitoring wells.  In addition, a suite of geophysical exploration techniques, including Refraction Microtremor (ReMi) and Multichannel Analysis of Surface Waves (MASW), were employed to assess the physical properties of the site soil and to understand the seismic characteristics of the site for use in a site-specific seismic spectral response analysis.


  • Challenging site conditions within a 50-year-old quarry site
  • Site-specific seismic spectral response analysis
  • Refraction Microtremor (ReMi) survey
  • Multichannel Analysis of Surface Waves (MASW)
  • Installation of piezometer monitoring wells


This project required a tight timeline in order to meet Metro’s due diligence deadlines.  Our firm enjoyed the pace that was needed to meet the project deadlines and looks forward to continued work with Metro in upcoming phases.

Due to the complexity of the site and the proposed development, Central Geotech’s wide range of technical expertise was vital to the success of the project’s initial phases. Through rigorous analysis, internal design charettes, and effective collaboration with the project team, Central Geotech gathered and analyzed the geotechnical information necessary for due diligence and project cost estimation within the timeline that was needed.

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