At first light over Bend, a recorded bell sounded across three headwater valleys, and roughly nine thousand people did what they had practiced: they left. The Cascade Spine region ran its full eruption-zone drill on Tuesday, and by the ninety-minute mark the valleys nearest the volcanic arc stood nearly empty, their roads moving in one calm direction.

The Spine is the Republic’s volcanic arc and its snowpack — the place the rivers begin and, on a geological clock, the place most likely to end a town overnight. Civil-defense doctrine here is not built on prediction, which no one can promise, but on rehearsal, which everyone can practice.

We do not drill because we expect the mountain to wake tomorrow. We drill so that the day it does, leaving is a habit and not a decision.— a regional civil-defense steward, Bend

Ninety minutes, graded in the open

The ninety-minute standard is the time the region commits to clearing its closest valleys once a full evacuation is called. Tuesday’s drill met it in two of the three valleys and missed in the third by eleven minutes, held up by a single bridge under repair. The Auditor will publish the timings — including the miss — and the region has already posted the bridge as the first item on its next readiness review.

That a missed timing is published at all is the point. The Backbone’s status board showed the headwater network in “Drill” condition throughout, distinct from a real outage, so no one mistook the exercise for the event. Mutual-aid crews from the Columbia Plateau staged at the threshold but were not needed.

By midmorning the valleys were filling again, the bell silent, the roads turned back to two directions. The mountain had not moved. That, the steward said, is exactly the condition under which a republic should learn to leave it.