The depressed DO in the mid-seetion of the Tualatin presiunably 

 steirmed from the decomposition of domestic and industrial wastes enter- 

 ing the river principally from the populated areas of Forest Grove and 

 EillsborOo 



A seasonal study of pollution in the Tualatin is indicated for 

 this stream supports resident game fish as well as a few migratory 

 food-fishes o 



iLo Clackamas River Basin 



The increase in both POD and conductivity normally anticipated 

 in any stream draining a vfell populated area was found in the lower 

 reaches of the Clackamas o The DO remainded consistently high, however, 

 with no evidence of depressiono It is concluded, thet under the condi= 

 tions prevailing on September 20, 1948, the Clackamas was fully capable 

 of absorbing the pollution burden being placed upon ito 



III. STM^ARY AND RKCOf.Q.^T?MDATIONS 



lo Existing data indicate that the most critical pollution 

 problem in the Lower Colxanbia Basin— insofar as fish life is concerned— 

 exists in the T?illamette River and certain of its tributaries. 



2o A reconnaissance survey, conducted during September and October 

 of 19483 indicated pollution in sufficient severity to affect fish life 

 nay develop in reaches of the Coast Fork Y/illamette, Marys, Rickreall, 

 South Santiam, South and Main Yamhill, Pudding, and Tualatin Rivers~as 

 well as in the main-stem Vfillamette betv/een Eugene and the confluence 

 cf the McKenzie, and betvreen Salem and the Columbia River, The 1948 

 data confirm many observations made by eerlier investigators. 



3o Main-stem pollution, which is sufficient to cause a Icni-oxjgen 

 block during low-water stages, constitutes a problem of particular 

 corsequence to the migratory food-fish resources of the Columbia Basin. 



4, At the present time, too little is knovm of the circtmstances 

 under which the main-stem Willamette oxygen barrier forms and lifts 

 to permit any accurate evaluation of its affect upon existing migratory 

 fish runs. Likewise, too little is knovm to permit an accurate evalua- 

 tion of benefits from the abatement program being vigorously prosecuted 

 by the Oregon State Sanitary Authority or of the probable benefits of 

 pollution abatement stemming from the Corps of Engineers' Willamette 

 Yailsy Project. 



5e The main-stem Willamette pollution block should receive top 

 priority in any study of pollution effecting fishlife in the Pacific 

 Northv/es t» 



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