Geotechnical report (if any ECA, slope, or known soil issue)

When you need one

A geotechnical report is triggered by:

• Any ECA on the parcel (steep slope, landslide-prone, peat, liquefaction, abandoned landfill).
• Slope ≥ 40% with ≥10 ft rise over ≤25 ft, even if it's off the parcel and the buffer crosses on.
• Known soils issues on the property or next door — pre-existing fill, unstable cuts, the neighbor's drainage problems.

For sloped, landslide-band, or liquefaction-zone lots — common in West Seattle, Magnolia, Crown Hill, South Park, Georgetown, Madrona — a geotech report is effectively required.

What it produces

Per SDCI Director's Rule 5-2016, the report covers:

• Subsurface character (borings, test pits, sometimes monitoring wells)
• Foundation design recommendations
• Retaining wall recommendations if needed
• Slope stability analysis
• Drainage and infiltration feasibility
• Seismic considerations
• Shoring requirements if excavation impacts neighbors

The number that matters

The report's foundation recommendation is the line item that swings the budget the most. Conventional spread footings cost what's in the GC's bid. Pin piles or helical piles (often required on landslide-prone or liquefaction soils) typically add $20,000 to $60,000 to the foundation alone.

Good news: you get that number in writing three months before mobilization, so you can price it into the GC bid rather than swallow it as a change order at excavation.

Cost

• Simple flat lot, no ECA: $1,000 – $3,500 (Seattle ECA reviews tend higher than other jurisdictions).
• ECA / slope / liquefaction: $3,500 – $8,000.
• Complex with multiple borings or monitoring wells: $10,000+.

Hiring criteria

• PE license, geotechnical specialty — verify at WA DOL.
• Familiar with Seattle's ECA review process and Director's Rule 5-2016.
• Prior projects in your specific neighborhood. The soils story varies block to block in Seattle.