Now, for some historical context . . .
Oregonians have raised questions about potential negative health impacts from swimming in the Willamette River for at least a hundred years. As was the case throughout the United States, Canada, and Western Europe, health threats spurred the first concerns about Willamette River pollution. The rapid expansion and concentration of urban populations made apparent the need for clean water supplies, effective ways to remove solid and liquid wastes, and improved sanitation practices to maintain community health. In the case of the Willamette River below Willamette Falls, pollution concerns grew steadily in the last decade of the nineteenth century and became persistent by the first decade of the twentieth century.
Representatives of the Oregon State Board of Health, newspaper editors, and other Oregonians were well aware of the steadily deteriorating quality of water in Portland and along the entire Willamette River. In February 1906, the Oregonian reacted to a typhoid epidemic linked to Eugene’s Willamette River sewer outfalls by calling the river a “common sewer for the entire valley between the Cascade and Coast Ranges of mountains from Cottage Grove to the Columbia.” Later in 1906 the Oregon State Board of Health observed typhoid in the Columbia River for the first time and identified the sources as tributary streams in eastern Oregon as well as the Willamette. The Secretary of the Board of Health noted that the “Willamette River has not been free from typhoid germs for years.” In response, an Oregonian reporter concluded that “it evidently behooves the many swimmers about Portland to cultivate the gentle art of keeping their mouths closed while in the water.”
Portland residents contributed significant amounts of typhoid-bearing raw sewage to Willamette River waters. Between 1905 and the mid-1920s, Portland nearly tripled in population. To serve the city’s residents and booming businesses, city engineers built an extensive system of “combined” sewers—lines that collected both storm water runoff and human waste. All of these sewers sent untreated effluents directly into the Willamette River, Columbia Slough, and other local streams. Such disposal practices were the norm in cities and towns throughout the United States, Canada, and Europe; practical technologies to treat sewage so as to minimize bacteriological threats and reduce biological oxygen demand were not available until the 1910s. In May 1911 Oregon State Health Officer Dr. Calvin S. White echoed the sentiments of the Oregonian in 1906 by declaring the Willamette River an “open sewer.”
Even as state officials drew attention to degraded water quality, newspaper editorials called for increased recreational use of the river and Portland residents looked to the river for other than waste disposal purposes. Leaders of the Apostolic Faith Mission of Portland conducted large-scale baptisms in the Willamette in July 1914, and a month later the first annual Willamette River marathon swim took place, from Oaks Park to the Morrison Street Bridge. Area residents continued to hold outdoor swimming and diving competitions at Oaks Park at least through the summer of 1921. In the midst of this popularity, in 1915 Portland City Commissioner George Baker proposed a plan to increase amenities along the river by designating swimming areas and providing dressing rooms. Aware of the many sewer outfalls within city limits, Baker planned these swimming zones in and near Oaks Park, above most outfalls.
In May 1922, the Portland Rowing Club filed an objection with Portland city commissioners to the proposed Lents trunk sewer outlet. Rowing Club representatives did not object to the outlet itself, entering just north of their property along the bank of the river. Their primary objection was that the outlet was not placed deep enough in the river channel to carry the effluent away.
The presence of raw sewage outfalls in such close proximity to recreational areas reflected the dominant belief in the assimilative and self-purifying capacities of flowing water. According to prevailing scientific and engineering orthodoxies, not only could bodies of water be used as waste sinks, locations for recreation, and, in many cases, even sources of potable water, but these seemingly mutually exclusive activities were also “reasonable uses” of streams.
A “reasonably” used body of water meant that it would serve the community-at-large in many ways. From the beginning of Euro American settlement in the valley, the Willamette had been a “working river,” and “not primarily a decorative river,” as the Portland Telegram stated in November 1922. The Willamette
has always dressed in working clothes. It is habitually unkempt. Its banks bristle with the rough rubbish of visionless, grubbing commerce. . . . Like most rivers in American cities, [the Willamette] is a sewer, a back-door area, a clutter-yard, a dump, a workshop . . .
As this editorial illustrates, residents of Portland perceived the Willamette in a variety of ways. Even when used reasonably, however, water quality in and near Portland continued to deteriorate, and excessive overall pollution levels were more apparent during the annual low-water periods of late summer through early fall.
Public health officials were aware of the direct link between this degradation and the city’s sewer outfalls into the Willamette, Columbia Slough, and other streams. Cooperative sewerage plans for the greater Portland area had been proposed since at least 1916 as part of attempts to establish a comprehensive urban plan and planning commission. In 1924, Portland City Health Officer Dr. George Parrish recommended construction of a sewage treatment plant with effluents treated with chemicals in settling basins. Parrish made this appeal in part because he reasoned that keeping people from swimming in the river would be practically impossible, even if prohibitory ordinances were adopted.
The Portland city council considered closing the Willamette River in Portland to swimming and recreation at least as early as the summer of 1924. Portland’s city health officer and chief sanitary inspector presented this option because of the threat of bacterial infection from raw sewage. In this particular instance, tidal action carried effluent from the Lents trunk sewer outfall upstream.
 For more thorough coverage, see James V. Hillegas, "Working for the 'Working River': Willamette River Pollution, 1926-1962," M.A. thesis, Portland State University, 2009.
 For the evolution of public health and sanitary engineering practices in the United States, see John Duffy, The Sanitarians: A History of American Public Health (Urbana, Ill., University of Illinois Press, 1990), and Martin V. Melosi, The Sanitary City: Urban Infrastructure in America from Colonial Times to the Present (Baltimore, Md., Johns Hopkins University Press, 2000).
“The Water Problem,” Morning Oregonian, Feb. 28, 1906, p. 8.
 “Germs in Rivers,” Morning Oregonian, Aug. 17, 1906, p. 14.
 See Carl Abbott, Portland: Planning, Politics, and Growth in a Twentieth-century City (Lincoln, Nebr., University of Nebraska Press, 1983), 49-52. Portland’s population in 1910 was 207,214, and in 1930 it was 301,815; for these figures, see U.S. Bureau of the Census, Census of Population: 1950 Oregon—Volume II, Part 37, Characteristics of the Population, Number of Inhabitants, Oregon, 12, available at http://www.census.gov/prod/www/abs/decennial/1950.htm, accessed Oct. 6, 2008.
 Melosi, The Sanitary City, 172.
“Sewage Laws Needed,” Morning Oregonian, May 4, 1911, p. 7.
 See, for example, “The Beautiful Willamette,” Oregon Daily Journal, Feb. 22, 1921, p. 6.
 “127 Are Baptized,” Morning Oregonian, July 31, 1914, p. 12; “Six Enter Trial Swim,” Morning Oregonian, July 27, 1914, p. 8. See also “Some of Us Are Still Wearing Our Woolens but the Bathing Girls Have Opened Season,” Oregon Sunday Journal, May 7, 1916, sec. 2, p. 3.
 See “School Swimmers Carry Off Honors,” Sunday Oregonian, July 31, 1921, sec. 2, p. 2.
 “Bathers Line River,” Sunday Oregonian, Aug. 15, 1915, sec. 2, p. 14.
 See “Sewer Objection Upheld,” Sunday Oregonian, May 28, 1922, sec. 1, p. 14.
 For more on the practical applications of the concepts of “assimilative capacity” and “reasonable use,” see, in particular, Melosi, The Sanitary City, 161-165, Joel A. Tarr, The Search for the Ultimate Sink: Urban Pollution in Historical Perspective (Akron, Ohio, University of Akron Press, 1996), 159-178, and Arn Keeling, “Urban Waste Sinks as a Natural Resource: The Case of the Fraser River,” Urban History Review 34:1 (2005), 58-70.
 “A River in a City,” Portland Telegram, Nov. 8, 1922, p. 6. Geographer Arn Keeling has found a similar relationship of the residents of Vancouver, B.C., to their urban river, the Fraser; see Keeling, “Urban Waste Sinks,” 60.
 For example, see Portland City Commissioner Robert Dieck’s call for a comprehensive sewage plan between the city of Portland and Multnomah County in “New Sewer Plan Is Recommended,” Sunday Oregonian, Oct. 1, 1916, sec. 1, p. 16. For Portland city planning efforts, see Abbott, Portland, 71-92.
 “Sewage Basins Wanted,” Sunday Oregonian, Aug. 3, 1924, sec. 1, p. 13.
 See “City Quarantine on Dips in River May be Adopted,” Oregon Daily Journal, July 24, 1924, p. 2, and “Windemuth Water Declared Impure,” Morning Oregonian, July 16, 1924, p. 8.