Author: David B. Williams

, Thursday, November 19, 2015

The Washington Hotel during the reconstruction of Second Avenue in 1905. Within three years, the hotel and the hill below it were demolished. Picture source: Seattle Municipal Archives, picture 77282.

Few cities in the United States can match Seattle in the scale of landscape reconstruction. The citizens not only reclaimed more than 890 hectares of new land in the harbor, but also renovated the largest lake in the city, completely changed the drainage method, dried up the main water outlets, and renovated tens of millions of cubic meters of hills. One of the most famous projects is the demolition of Danny Hill, a 73-meter-high hill located at the northern end of Seattle's central business district.

After more than three years of work, the reconstruction of Mount Danny was completed in December 1930. "The once great cape was thrown out by nature a long time ago, creating trouble for Seattle's gradual expansion," a reporter from the Seattle Times wrote, and it no longer exists. time. "Finally opened the way for huge new buildings. The Central Business District headed north to Beiping and entered the territory. Just a few months ago, high clay dams prevented progress, poorly maintained streets, running-residential, old public and Semi-public building."

The renovation of Denny Hill was mainly promoted by the city of Seattle engineer Reginald H. Thomson, who was indifferent to the city's notorious topography. For Thomson, Seattle "is like a pit. To get anywhere, we have to climb out if we can." Hills like Danny hinder progress, restrict traffic, and reduce property values. . If Seattle is to become great, it must remove its hills, and Thomson decided that he was the one who did it.

The Danny Hill project was exhibited in 1907 and involved trains, steam shovels, hydraulic cannons, kilometers of pipes and tons of debris. Image source: UW Special Collections, image UW36359, composite image from Asahel Curtis photo.

Thomson's first push was in March 1898, when he started work on the west side of Mount Danny. Workers used hydraulic hoses to wash down 13 blocks of First Avenue. The deepest vertical incision is 5 meters. Most of the resulting 85,000 cubic meters of sediment eventually flowed into nearby Elliott Bay.

Five years later, Thomson’s crew attacked the mountain again. The reconstruction of Second Avenue removed more than 450,000 cubic meters of material, almost all of which entered Elliott Bay. During the project, at least three people died, including a 9-year-old boy who was blown to death by explosives while being heated by a worker in a pan with an open flame. A few months later, Thomson's third renovation project began, focusing on the southern end of the mountain. This is one of the two peaks of Mount Danny, with the steepest slope and a block height of up to 30 meters. It is also home to the Washington Hotel, one of Seattle's most magnificent buildings. The hotel opened in 1903-its first guest was President Theodore Roosevelt-the hotel offers magnificent views of the city, Puget Sound and surrounding mountains. Its owner argued with Thomson on the reclassification project for several months, but finally acquiesced. He realized that razing his hotel and lowering the hill would significantly increase the value of his land. By 1908, another 500,000 cubic meters of Denny had disappeared and the hotel had disappeared.

The high water pressure is achieved by pumps or gravity feed water, and the water is sent down the mountain through successively smaller pipes. Picture source: UW Special Collections, picture UW36352.

What makes Seattle's reclassification possible is the city's glacial history. During the maximum of the last ice age, the 1,000-meter-thick Puget flap of the Cordillera Ice Sheet passed through Seattle and finally reached Olympia, about 70 kilometers south. The glacier left three different layers of material, which formed the hills of Seattle. At the bottom is fine-grained clay deposited in the former ice lake. There are huge boulders up to 3 meters in diameter in this layer. The base layer is covered by a layer of washing sand, and then there is a thin layer on top. Although the advancement of glaciers did compress and consolidate these deposits, the clay and sand are relatively soft and easy to remove.

For most reconstructions in Seattle, the main demolition method is hydraulic. This requires a lot of water, most of which is drawn from Elliott Bay or Lake Union north of Mount Denny. The pipe from the water source enters the pit where workers known as "giants" operate hydraulic hoses. There are two giants and a team of five in each pit. A man fired at each giant, holding a one-meter handle connected to a cast iron nozzle. The nozzle with a length of 2 to 3 meters is mounted on an articulated base and has an adjustable opening with a diameter of 7 to 12 cm. This is the most skilled position in the team, usually held by the "old giant [man]" who studied trading in the gold mining area of ​​Alaska. In addition, each giant team uses wooden planks to guide the mud in the pit into a pipe that takes away the previous hills. The board members also removed roots and other materials that could block the system. Another person watched the iron fence, or grizzly bear, at the mouth of the pipe, which blocked the larger rocks and clay blocks. He also removes larger materials or hammers them into smaller pieces with a sledgehammer. Under normal circumstances, a worker can wash away approximately 750 cubic meters of material in an 8-hour shift, or enough material to fill 6,750 trolleys.

Water usually provides enough power to push away the hills, but when workers hit hard lenses in the clay and cultivate or encounter boulders, they have to rely on explosives. What's more exciting is that the workers found fossils, including tree trunks and mammoth teeth.

Isolated small hills known as "hate mounds"-exhibited in 1910-were left around the city, allegedly because their owners disagreed with the re-rating and kept them high in contempt of the city. Picture source: UW Special Collections, picture UW4812.

Thomson may have considered the first three regrades practice courses. In August 1908, he asked his workers to turn their hydraulic guns towards the center of the mountain. For the next two and a half years, they worked continuously, washing more than 4.1 million cubic meters of mud into the bay. This fourth effort produced perhaps the most famous reclassification feature: isolated hills are called "hate mounds", "hate piles" or "hate humps." In May 1910, six of these notorious pillars of private property rose from the flat hillside, giving Monument Valley a new look.

The legend believes that they exist because their owner disagrees with the re-rating and keeps them standing high against the city. However, there is no evidence to support this claim. At least three people with mounds signed a petition for re-rating. In addition, two of them talked to reporters at the time and both expressed their full support for the re-rating. One person said that he left his mound in place because he had no money to pay, and the other owner was in Alaska. As soon as he arrived in Seattle, he paid to razing his mound to the ground.

The fifth and last renovation of Mount Denny began in May 1929. The workers did not use the hydraulic giant for the first time. Much of the area surrounding the renovation has been developed, so it is impractical to gather muddy streams on paved streets with heavy traffic. Instead, the contractor demolished the hill with an electric shovel or excavator, and as with all previous renovations, the soil entered Elliott Bay. In order to reach the bay, the sediment is transported on a self-inclining barge via a conveyor belt.

The self-tilting barge has two internal storage tanks, one on each side, and an open deck that can hold 300 cubic meters of soil. A tugboat towed the entire ship into Elliott Bay, where a crew member opened the valve on the side of the ship. Within a few minutes, one of the tanks was filled with water, and the out-of-balance boat turned over and dumped its load. The tugboat then pulls the scow back to shore, ready for the next load.

Pieces of hills are sent into the hopper, fall onto the constantly moving conveyor belt, shoot at the waiting scows at a speed of 120 meters per minute and enter Elliott Bay. The crew is merciless. By December 1930, Danny Hill had almost disappeared.

On December 10, Mayor Frank Edwards climbed onto an excavator and pulled a lever, and the last cubic meter of Danny Hill disappeared. Hundreds of people stood by and watched, including many who were born on the mountain, attended Danny’s school and lived there all their lives. "There are a lot of wet eyes," a reporter for the Seattle Post wrote.

In 1988, when the University of Washington oceanographer Mark Holmes and his colleagues were inspecting the bathymetry of Elliott Bay (Elliott Bay), they noticed the anomalous landforms off the coast of downtown Seattle. Not sure why it was there, they measured this small mound through seismic reflection measurements and found that it was between 3 and 36 meters thick, 460 meters wide, and 760 meters long. The total volume is approximately 6.8 million cubic meters. When Holmes and his team began to study the history of Elliott Bay, they realized that they had discovered the remains of Mount Denny by accident. It is where it should be. It has long been forgotten, but it has not disappeared.

This article is adapted from Williams' latest book "Too High and Too Steep: Reshaping Seattle's Terrain" published this fall. More of his works can be found on geologywriter.com.

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