INTRODUCTION 



Pollution of the Willamette River of Orepon has attracted 

 nationwide attention not only for the outstanding; example of an 

 overloaded major river that it offers but, also, because of its 

 impact upon economically important and hif^hly publicized run of 

 spring-chinook salmon. 



Pollution of the Willamette River is a problem that has received 

 considerable attention over the past two decades. The initial organized 

 studies of Willamette pollution stemmed from a conference called by the 

 Oregon State Board of Health in September, 1926. Following that con- 

 fe^encq^ the Portland City Departments of Health and Engineering routinely 

 sampled the river in the Portland harbor area extending from the Sellwood 

 Bridge, at river mile 16.5, to the confluence with the Columbia. These 

 studies were conducted betv/een October, 1926 and December, 1928 and re- 

 vealed that less than three parts per million of dissolved oxygen were 

 present in the river water during August, 1927, and during both August 

 and September of 1928. 



Rogers, Mockaore, and Adams (1930) reported more extensive studies 

 of the Willamette pollution after surveying the main stem and major 

 tributaries between July, 1929, and May, 1930, These authors reported 

 an oxygen block (io©., less than five parts per million of dissolved 

 oxygen) existed between Wilsonville (river mile 37) and the Sellwood 

 Bridge in Portland in August, 1929, but had disappeared by the time 

 they next studied the river in the following October. 



Gleeson (1936) mad© an extensive study of the pollution and tidal 

 complex betv/een the Sellwood Bridge and the Columbia River, September 

 5 to 27, 1934o Gleeson obtained no samples exceeding five parts per 

 million of dissolved oxygen over the entire reach of river that 

 he studied except in the extreme lower end where Columbia River back- 

 water was involved. Gleeson also demonstrated by calculation that 

 an oxygen block would develop in the lower Portland harbor area even 

 though all wastes from that city were excluded from the river. He 

 likewise determined that 7.6 days were required for the passage of 

 water between the Sellwood Bridge and the Colimibia River when the 

 river discharge vms at 4,000 second feet. 



Craig and Townsend (1946) reported a series of seven spot samplings 

 at the Sellwood Bridge and at the St. Johns Bridge, Portland^ between 

 February 4 and July 28, 1941, and four additional samplings betv/een 

 May 2 and August 21, 1942. Their findings indicated that the oxygen 

 block had formed in the VJillamette at the St. Johns Bridge sometime 

 between March 18 and May 1, 1941. The oxygen block had extended up- 

 stream to the Sellwood sometime between Fay 29 and July 17, 1941. 

 The oxygen block had formed at both stations sometime between May 

 2 and early August, 1942. 



