Metronatural: Inventing and Taming Nature in Seattle - Politics of Urban Runoff: Nature, Technology, and the Sustainable City - page 116

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Figure 5.10
Population growth of Seattle, 1900-1960. Source : City of Seattle 2008.

connect the waterbodies and thereby open them to commerce and recre-
ation. The ship canal dropped the elevation of the lake by an average of
ten feet, creating new shoreline for residential development, and redirected
the lake outfl ow through the ship canal to the west rather than the Du-
wamish River to the south.
Thomson made a wise decision in the late nineteenth century to direct
major sewage outfalls away from Lake Union and Lake Washington, but
nonetheless, smaller sewage outfalls from Seattle and other municipalities
continued to be directed to the water bodies. By 1922, Lake Washington
was receiving thirty raw sewage outfalls from the east side of the city,
and residents began to recognize signifi cant impacts on the water qual-
ity of the lake. 109 The city built three rudimentary wastewater treatment
plants in 1924 at a cost of $2.5 million but later abandoned these plants
in favor of an interceptor sewer, constructed in 1936, to divert all Seattle
sewage outfalls from the lake. 110 Despite these efforts, growth of the sur-
rounding suburbs, particularly after World War II, would lead to further
deterioration of the lake's water quality. The Mercer Island fl oating bridge
was opened in 1940 and provided a convenient automobile connection
between Seattle and the eastside. Urban sprawl around the lake created
twenty-one independent sewer districts by 1955, and these communities
were dumping both treated and untreated waste into the lake. Visibility