Chehalis's Seismic Design Category, explained

Chehalis carries Seismic Design Category D under USGS's ASCE 7-16 model. High seismic hazard - this is the category most of coastal California, the Pacific Northwest, and other active fault regions fall into. Code mandates significant seismic detailing and restricts irregular structural configurations. This is the category the Brace + Bolt scope (cripple-wall bracing, foundation bolting) is built for. That puts Chehalis in the 91th percentile nationally for seismic hazard - higher than 91% of the 4,875 US cities USGS was checked against here.

Where Chehalis sits in Washington

The raw figures: peak ground acceleration 0.521g, short-period spectral response 1.18g, 1-second spectral response 0.486g. Among 125 Washington cities in this dataset, Chehalis ranks 50 for seismic hazard, the 60th percentile within the state. About 7,717 people live in Chehalis, Washington.

What a retrofit costs in Chehalis

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for Washington. A typical retrofit still runs $5,000-$10,000 nationally, about $7,000 for a common single-family job.

Insuring against this, not just retrofitting

Outside California, earthquake coverage is typically sold as an endorsement added to a standard homeowners policy, not a separate product - worth asking about directly when getting a home-insurance quote for a Chehalis address.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced Chehalis's numbers. The guide to what a Seismic Design Category actually means covers why a category is never a substitute for an engineer's assessment of one specific house.