Howard A. Hanson Dam

  • By Alan J. Stein
  • Posted 9/10/2001
  • Essay 3549
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Dedicated in 1962, the Howard A. Hanson Dam brought necessary flood relief to the Green River Valley, and opened the way for increased valley development. Named for Seattle attorney and state legislator Howard A. Hanson (d. 1957), who campaigned long and hard for the project, the dam has changed South King County from flooded farmlands to a sea of warehouses, industrial plants, condominiums, and shopping centers.

Lay of the Land

When settlers first arrived in the valley in the 1850s, they found arable land, abundant salmon, and proximity to both Puget Sound and the mountain passes, making it an excellent location for hardworking farmers and fishermen wishing to sell their wares.

The valley was fed by several rivers. The White River and the Green River flowed out of the mountains to the east, forming a confluence near what is now downtown Auburn. From there, the river traveled north and was met by the Black River (an outflow from Lake Washington) near what is now Tukwila. The combined rivers formed the Duwamish River which then flowed farther north into Elliott Bay.

South of the White/Green river confluence lay the Stuck River which flowed to Commencement Bay in South Puget Sound. The Stuck and the White rivers flowed so near to each other that during spring floods, the two rivers would sometimes merge, spilling water far to the north and south.

Early Flood Control

The valley was first a bustling center for hop farming, but an aphid infestation in 1890 destroyed practically all of the crops. After that the farms were mostly dairy farms and berry farms. The land was very fertile, but farmers dealt continuously with the problem of yearly flooding. Logjams would occur on the rivers which would often redefine the course of the water.

Sometimes the floods became so severe that farmers would illicitly dynamite the jams in the middle of the night, causing other farmers to get flooded out. This type of feuding between White River and Stuck River farmers continued until 1906, when one of the largest floods diverted most of the water to the Stuck River, leaving the White River’s northern channel dry. After that, government engineers stepped in and built a diversion dam, which channeled all of the water along the Stuck River.

Nevertheless, floods remained an almost annual event in the valley, usually around the months of November and December. Farmers built their buildings on small stilts or slightly higher ground and learned to tie up rowboats to their front porches in case of extreme flooding conditions.

This Means War!

In 1926, the Associated Improvement Clubs of South King County was formed, and one of their first projects was flood control. They performed studies on diking, river-deepening, river-straightening, and dammed reservoirs, but realized that the problem was bigger than any solution they could devise. They turned to the federal government, specifically the War Department.

In 1936, the U.S. Army Corps of Engineers began their own studies, and after five years of analysis recommended a water-storage site a few miles upstream from Auburn. This was opposed by fishing interests, due to the damage a dam would cause to spawning fish. The Army would have gone back to the drawing board, but World War II intervened, delaying any further investigation until 1946.

Three years after the Army resumed their studies, they recommended construction of a storage dam at Eagle Gorge, far to the east into the Cascade Mountains. Congress adopted the Eagle Gorge Dam as a federal project in 1950, and advanced planning continued throughout most of the decade.

Hands-on Hanson

An early campaigner for flood control in the valley was Howard A. Hanson. Hanson was a member of the State Legislator in 1907, and in the 1920s became the Chief Civil Deputy Prosecuting Attorney for King County. In the late 1920s, he became chairman of a rivers and harbors sub-committee of the Seattle Chamber of Commerce.

Hanson felt that flood control in the valley would aid not only valley farmers, but also the economic development of both King and Pierce counties. Taking his campaign on the road, it was Hanson who turned the project in a regional undertaking, rather than a localized one.

After World War II, Hanson organized efforts leading to contributions by the State and King County totaling $2 million. Unfortunately, the tireless advocate for Eagle Gorge Dam passed away on November 4, 1957, and was never able to see the fruits of his labors. In his honor, in 1958 the name of the dam was changed to Howard A. Hanson Dam by an Act of Congress.

Dam Building

Groundbreaking for the Howard A. Hanson Dam was held on February 3, 1959, when a dynamite blast was set off, showering rock and dirt into the air. Relocation of 13.7 miles of Northern Pacific Railway line, which travels along the river, had begun three years earlier in preparation for construction.

A 900 foot long tunnel, 19 feet in diameter, was built first to divert the Green River away from the construction site. For the next three years, hundreds of workers labored on the project, creating a dam that rose 235 feet above the bottom of the Green River, and which was 675 feet wide at the crest, including the spillway and abutment structures.

The only delay in the project occurred in November 1959, caused, unsurprisingly, by a flood. A cofferdam was wiped out and had to be rebuilt. Work continued apace, and the dam was actually able to stop a Christmas Day flood in 1961, months ahead of schedule. Formal dedication of the dam occurred on May 12, 1962, when thousands of valley residents traveled deep into the mountains to witness the beginning of their flood-free days.

What Price Progress?

The total cost of the dam came out to $40.5 million, of which $38.5 was federal investment. At the time of dedication, estimated annual benefits from the dam were $2 million (in 1962 dollars). As of October 1996, Howard A. Hanson Dam had prevented flood damages amounting to more than $694 million.

For the next few years, farming flourished in the valley, now that floods were no longer an issue. Then, things began to change. Developers, who had previously shunned the waterlogged valley, now saw miles of flat, open land. What was meant to be a boon for farmers turned out to be just the opposite.

Farmland acreage began to decrease, as industry moved in. In the 1960s, the Boeing Company built a vast aerospace plant a few miles north of downtown Kent, while other companies began building warehouses up and down the valley. More jobs were created in the valley, and apartment houses and condominiums began sprouting up over the next few decades, as well as shopping centers, strip malls, and auto dealerships.

By the end of the twentieth century, farming was a mere side industry. Farms still dot the landscape, but many are being encroached by asphalt, concrete, and steel. Now, instead of engorged waterways the valley is filled with glutted highways and streets. Traffic jams have taken the place of logjams.


Clarence B. Bagley, History of King County Vol. 1 (Chicago: S.J. Clarke Publishing Co, 1929), 712-727; “Gorge Dam Begun,” The Seattle Times , February 3, 1959, p. 16; “Soaring Costs Menace Eagle Gorge Project,” The Seattle Times , March 20, 1959, p. 1; “Howard A. Hanson Dam, End to Flood Threats; Provides Other Benefits to Valley,” Kent News-Journal, May 9, 1962, pp. B-6-7; “Hanson Dam Dedication Draws Crowds of 2,300,” Kent News-Journal, May 16, 1962, p. B-1; U.S. Army Corps of Engineers, Howard A. Hanson Dam, Eagle Gorge, Green River, King County, Washington (Seattle, 1963); Additional information provided by the White River Valley Museum.

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