The Portland Japanese Garden underwent a major renovation and expansion. The existing Gardener’s Building was removed to make way for a new Café, Village House, and Garden Workshops. A shoring system was installed to retain cuts up to 30 feet in height within the improved area and dry-stacked cut stones were used as fascia for the shored walls and to construct low retaining walls. In addition, the parking area was expanded to include a new ticket structure and ponds.  

The Japanese Garden is located within the limits of a well-documented large ancient landslide that shows creep movement. GRI reviewed existing geologic information, and conducted a site reconnaissance, subsurface explorations, seismic refraction profiling, and laboratory testing, and completed engineering analyses. The primary geotechnical considerations included the presence of the landslide, near-surface moisture-sensitive soils, variable conditions of the underlying basalt, and steep slopes. GRI addressed site preparation and grading, excavations, retaining walls, shoring, conventional spread footings, drilled shafts, tie-back anchors, floor support, subdrainage, seismic considerations, pavement design, and stormwater management. Under separate contracts, GRI provided geotechnical services for the new Koi holding tank building, new bonsai greenhouse, and renovation of the existing Japanese Garden Administration Building. 

Location: Portland, Oregon

Owner: Portland Japanese Garden

Market Sector: Development

Services: Geotechnical Engineering, Seismic Engineering