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Multnomah County, Oregon
Geotechnical Engineering in Multnomah County, OR
Subsurface investigations, laboratory soils testing, and geotechnical reporting to characterize site conditions before design and verify them during construction. Multnomah County is covered on a project basis through our Seattle, WA regional hub.
- Dispatched from
- Seattle, WA regional hub · project-based mobilization
- Lead time
- Set in the proposal, with mobilization planned around your pour and earthwork schedule
- Laboratory
- Sugar Land, TX laboratory under chain of custody, or a mobile laboratory for large projects
- Reporting
- Reviewed and issued under a documented quality system; formatted for owner, engineer, and building-official review
- Serving
- Multnomah County, OR — Portland, Eugene, Salem
- Coverage
- Oregon statewide · 27 regional hubs
- Technicians
- ACI- and NICET-certified field staff; licensed professionals in Oregon
- Call us
- (346) 420-5425
Scope
Geotechnical services in Multnomah County
- Soil borings and sampling programs sized to the structure and site
- Laboratory index testing: Atterberg limits (ASTM D4318), moisture content (ASTM D2216)
- Moisture-density relationships and bearing evaluation for foundations and pavements
- Expansive-soil characterization for slab and pavement design
- Construction-phase verification: proof rolls, subgrade acceptance, fill placement observation
ASTM D4318ASTM D2216ASTM D698ASTM D1557
Full scope, standards list, and pricing basis: Geotechnical Engineering.
Local conditions
Geotechnical conditions in Multnomah County
Building in Multnomah County means contending with a demanding subsurface environment. The Portland Basin and surrounding terrain present a mix of soft alluvial soils along river corridors, expansive clays in upland areas, and the ever-present consideration of seismic hazard in a region underlain by the Cascadia Subduction Zone. Wet winters with persistent rainfall complicate earthwork windows and raise moisture-sensitivity concerns for native soils and engineered fill. Before a foundation is designed or a retaining wall is sized, the subsurface needs to be characterized — not assumed. Our geotechnical services for Multnomah County projects include subsurface investigations, laboratory soils testing, and geotechnical reporting by licensed engineers. Work is dispatched through our Seattle regional hub on a scheduled and project-based basis. Field technicians hold ACI and NICET certifications, and the laboratory operates under a documented quality system. The result is reliable site data that engineers, contractors, and developers can act on with confidence.
The Portland metropolitan area is underlain by varying deposits of alluvial silts and clays near the Willamette and Columbia rivers, where low bearing capacity and settlement potential are common concerns for foundation and infrastructure design. Oregon's wet season — typically October through April — compresses workable earthwork windows and requires close attention to soil moisture conditions and compaction specification compliance during construction.
FAQ · Multnomah County
How does Cascadia Subduction Zone seismic risk affect the geotechnical scope for my Multnomah County project?
The region's seismic exposure elevates the importance of liquefaction potential analysis, particularly on sites with loose saturated sands or silts near river corridors. A geotechnical investigation for projects subject to Oregon Structural Specialty Code (OSSC) seismic provisions will typically include soil classification per IBC Section 1613, site class determination, and where warranted, liquefaction susceptibility evaluation based on SPT or CPT data.
What soil testing standards apply to the compaction verification work during earthwork on a Multnomah County site?
Field density testing is performed in accordance with ASTM D6938 (nuclear gauge) or ASTM D1556 (sand cone) depending on material type and specification requirements. Laboratory moisture-density relationships are established using ASTM D698 (standard Proctor) or ASTM D1557 (modified Proctor). The applicable test method and compaction target are typically dictated by the project geotechnical report and the governing specification.
We are building on a site near the Willamette River floodplain — what specific concerns should the geotechnical investigation address?
Low-lying alluvial areas along the Willamette commonly contain soft, compressible silts and clays with elevated moisture content. The investigation should address bearing capacity, settlement potential, consolidation characteristics (ASTM D2435), and groundwater depth. For structures sensitive to differential settlement or planned below grade, lateral earth pressure parameters and dewatering feasibility also warrant evaluation in the geotechnical report.
Which office covers geotechnical in Multnomah County, OR?
Field work in Multnomah County is dispatched through the Seattle, WA regional hub, about 145 miles away. Laboratory testing is performed in Sugar Land, TX under chain of custody, or in a mobile laboratory mobilized to large Multnomah County projects.
Are the technicians you send to Multnomah County certified?
Field sampling and testing in Multnomah County are performed by our ACI- and NICET-certified technicians. Geotechnical engineering and professional services are delivered with professionals licensed in Oregon, coordinated under one proposal.
Scheduling & proposals
Need geotechnical engineering in Multnomah County?
Call to schedule a technician, or send project documents for a written proposal.