Date of Determination- - = --- = --"= Augo 29 Sept. 5 Sept. 12 



Biochemical Oxygen demand, Sellwood Bridge; 



1949 conditions (lbs/day) 



1949 conditions reduced 30^ (lbs/day) 



1949 conditions reduced 50^ (lbs/day) 



Anticipated minimum dissolved oxygen present 

 below Sellwood Bridge; 

 Ae In terms of pounds per days 



1949 conditions septic septic septic 



mth 02 deficit and BOD reduced 30^ 70,928 34,948 70,219 



With 02 deficit and BOD reduced 50?? 123,702 92,994 126,888 



B. In terms of parts per millions 



1949 conditions septic septic septic 



With O2 deficit and BOD reduced ZOfo 2,5 1.3 2.4 



With O2 deficit and BOD reduced 50^ 4.4 3.4 4.3 



Admittedly, data obtained by weekly spot samplings constitute an 

 insecure basis, at bestj for definite conclusions regarding any problem 

 as complicated as pollution abatemento These data do strongly indicate, 

 however, that the primary treatment of domestic wastes alone will not 

 prove sufficient to lift the Willamette pollution block. An overall 

 r<«iu<B41on exceeding fifty percent of the 1949 waste load of the river 

 appears necessary to assure clearance of the lower reaches for the 

 passage of migratory fishes during the low flow stages. It appears 

 most probable, therefore, that the utilization of the Yfillamette River 

 by fall-chinook salmon must await either sufficiently increased minimum 

 river flows that may be provided by the Corps of Engineers' Willamette 

 Valley Project and/or the effective treatment of many of the oxygen- 

 consuming industrial wastes. 



CONCLUSIONS 



1» Pollution of the main stem Willamette River is a problem 

 cf long standing and one that seriously threatens the fall utiliza- 

 tion of the river's potentialities for fish production. Above 

 WiloOnville, the quality/ of the main stem water is being maintained 

 well within the accepted tolerance limits of cold-water fishes by 

 effective reaeration and dilution, in spite of a heavy pollution 

 burden. Below Wilsonville, however, where the stream gradient 

 decreases a rapid degradation in water quality develops during the 

 low water stages. During 1949, as in earlier years, an oxygen 

 block developed throughout the entire reach of the lower Willamette. 

 Under the conditions prevailing during 1949, the block developed 

 throughout its maximum range between July 6 and 19, The block per- 

 sisted throughout the sumner until it was dissipated by increasing 

 river flows sometime betv/een September 27 and October 12. More than 

 five parts per million of dissolved oxygen were found throughout the 

 river to its confluence with the Columbia on October 12, 



