‘Supertunnel’ documents the building of the Highway 99 tunnel as it turns 5

THOUGH A YOUNG Catherine Bassetti had run away to join a circus aerial act, nothing prepared her for the dizzying altitudes she encountered documenting Seattle’s most audacious construction project of this millennium.

Her dazzling illustrated book, “Supertunnel: Building Seattle’s State Route 99 — Journey from Light to Light,” provides a backstage view of the project’s colossal scale. As a re-imagined waterfront nears completion on the tunnel’s fifth anniversary, Bassetti’s luminous photos capture trials, tribulations and triumphs.

“It provides a detailed analysis of the complete ‘design-build’ of the tunnel,” she says, “as well as the groundbreaking engineering and complex problem-solving that took place.”

First, the backstory. The 2.2-mile-long Alaskan Way Viaduct opened April 4, 1953, immediately becoming Seattle’s most traveled north-south corridor. The looming double-deck highway, while dividing the city from its waterfront, also offered drivers a spectacular unfolding vista — the loss of which is still lamented.

In 2001, the magnitude-6.8 Nisqually earthquake shook the region, causing widespread destruction, including alarming damage to the viaduct’s support structure. After long debate over possible fixes, the state Department of Transportation, King County and the City of Seattle announced in January 2009 that the viaduct would be replaced by a tunnel.

Construction began in July 2013 with the arrival of Bertha (named after Seattle’s first woman mayor, Bertha Knight Landes), then the world’s largest tunnel-boring machine. After significant delays, boring ended in 2017. Two years later, the tunnel opened.

Fittingly for the project’s visual documentarian, composition and design run in Bassetti’s family. Her grandfather, Joseph W. Wilson, helped create downtown’s Northern Life Tower (1929, now the Seattle Tower), an Art Deco landmark. Her father, architect Fred Bassetti, is responsible for several of our region’s greatest hits, from the Seattle Aquarium (1971) to the Seattle Municipal Tower (1989).

Catherine Bassetti’s early Barnum & Bailey stint and career as a European commercial photographer honed physical and pictorial skills that landed her the job of photographing the full tunnel project. She wound up in places she’d never anticipated, from squeezing into cramped corners underground to dangling from cranes.

With dozens of vertiginous and expansive views, “Supertunnel” details the unique journey of documenting a vast, structural tour de force of engineering. By revealing views hitherto unseen, it finds beauty in the depths and heights. From start to finish, the book follows the tunnel’s breathless path — as the book’s optically attuned subtitle aptly states, from light to light.