Sluicing away Jackson Street to unclog the city’s future arteries

LONG BEFORE BECOMING a student of Seattle history, I had a recurring (and oddly unsettling) dream of hiking an unbroken ridge between First Hill and Beacon Hill. Were it not for Reginald Heber Thomson (1856-1949), our city’s current topography might have matched my dreamscape.

When Thomson first stepped onto Seattle docks on Sept. 25, 1881, he told a friend that the city was built in a hole, and he meant to dig it out. The 25-year-old’s ambition might have been attributed to youthful exuberance, but in the decades to come, his words would prove prophetic. Appointed city engineer in 1892, Thomson began by installing water and sewage infrastructures (still in use today) before attacking Seattle’s hills and valleys.

Notes David Williams in his masterful 2015 history of Seattle topography, “Too High and Too Steep,” to Thomson, “A functioning city was like a human body.” Thomson insisted that “enlarging and improving what he called the city’s arteries” was vital to Seattle’s future health.

Picturesque piles of glacial deposit — like Denny Hill north of downtown — were, in Thomson’s view, “an offense to the public,” interrupting the free flow of traffic. In 1898, the hill’s decapitation commenced, using hydraulic hoses (called “giants”) to liquefy and sluice away the moraine.

When Rainier Valley residents complained that the Jackson Street incline’s steep 15% grade obstructed access to Seattle’s business district, Thomson lent a sympathetic ear. Intrigued by their initial suggestion to tunnel through the hill, he eventually advanced a “far cheaper and far better” solution — utter removal. “Every house and every garden and every street” in the affected areas might be lost, but he judged the sacrifice necessary to make municipal headway.

In May 1907, the hydraulic giants began their work. Enormous pumps fed up to 25 million gallons of fresh and saltwater daily to their pressurized hoses, expelling 1,000 cubic yards of dirt during each eight-hour shift.

Completed in December 1909, the Jackson Street project covered the largest surface area of all Seattle regrades: 56 blocks in total, with 29 lowered and 27 raised. More than 3 million cubic yards of dirt were moved, lowering Ninth and Jackson by 85 feet and raising Sixth and Weller by about 30.

My recurring dream might harbor some whiff of lost geography, yet the force of R.H. Thomson’s vision resides. While often trading natural beauty for an engineer’s expedience, his straightened, flattened, stretched Seattle provided a blank canvas for cityscapes to come.