Portland Area Distribution Center

In 2018, a leading real estate developer set out to build a state-of-the-art distribution center on the grounds of a historic Portland horse track. Portland Meadows had entertained locals since 1946, but after redevelopment the plot would be home to more than 1 million square feet of industrial warehouse space, dramatically expanding delivery capacity for large retailers in the Portland area such as Amazon.

The real estate company contracted with GeoEngineers for a range of geotechnical services during development. After careful site investigation and characterization, the GeoEngineers team decided that the facility could avoid costly deep foundations or expansive ground improvement programs. A relatively straightforward preload program would compact the soil prior to construction and reduce liquefaction risk. This approach simplified construction and reduced project costs for our client without sacrificing resiliency.

Approach

• Soil Characterization: The team started with a review of existing geologic data before mobilizing to the site to complete drilling and cone penetration tests. Soil samples were analyzed and characterized in a GeoEngineers laboratory.
• Liquefaction Analysis: GeoEngineers’ seismic experts estimated the amount of ground surface settlement to expect during a maximum-considered earthquake (MCE) event using standards in the 2015 International Building Code (IBC).
• Recommended Seismic Response Spectra: Our geotechnical engineers delivered generalized response spectra in accordance with ASCE 7 design standards.
• Foundation Recommendations: The team recommended less costly shallow foundations for the building as long as contractors completed a preload program to reduce long-term settlement.
• Preload Program Design: GeoEngineers’ team found a safe and efficient way to avoid costly deep foundations or extensive ground improvement. By recommending a preload program consisting of four feet of preload fill above the floor elevation our geotechnical engineers saved the client money without sacrificing design resiliency.
• Dewatering: To speed up settlement during the preload program, GeoEngineers also suggested installing wick drains to help with temporary dewatering.
  Structural Fill Recommendations: GeoEngineers identified moisture-sensitive soils on the project site and cautioned against using it for structural fill.
• Construction Observation and Special Inspections: Field staff observed a range of construction activities on behalf of our client, including fill placement/compaction, subgrade preparation and asphalt concrete compaction for the building’s parking lot.

Results

GeoEngineers’ careful geotechnical analysis and recommendations were the foundation of the project’s success. By designing a preloading program to mitigate future settlement GeoEngineers’ team could recommend a shallow foundation—ultimately reducing project costs for our client.