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Portland Water Bureau

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Dye Study Conducted at Bull Run River

Starting in the summer of 2014, the Portland Water Bureau will be required to meet lower water temperature targets in the lower Bull Run River to improve habitat conditions for fish. 

The Water Bureau has been preparing to meet those requirements. The rock weir at the downstream end of the stilling basin below Dam 2 was removed because it held water up and caused heating. The north water intake tower at Dam 2 is currently being reconstructed to allow cold water to be stored for summer use. The Bureau will be releasing some of that cold water in the early morning each summer day so that the late afternoon peak temperature downstream at the Larson’s Bridge site will be lower. 

With the rock weir now gone, the Bureau needs to again determine how long it will take water to travel from Headworks to Larson’s Bridge.  This information is vital in helping to determine the timing of the release of cold water. 

Assistant Program Specialist Ross Turkus releases dye just below Headworks.
Assistant Program Specialist Ross Turkus releases dye just below Headworks.

To figure this out, staff recently completed a study using fluorescent dye introduced into the Bull Run River. Senior Engineer Jeff Leighton led the study team that released dye while the river was running at a 20 and 40 cubic feet per second flow, the range of river flows that will be used in the future. Portland Water Bureau fish biologists confirm that the bright-colored dye that was selected for the test does not harm aquatic life. 

Engineering Intern James Ferris sampling for dye near Larson’s Bridge.
Engineering Intern James Ferris sampling for dye near Larson’s Bridge.

Water samples were collected and analyzed using an instrument called a fluorometer.  The fluorometer can detect dye concentrations down to one (1) part per billion in water. It took on average about 11.5 hours for water to get to Larson’s at 20 Cubic Feet per Second (cfs) and seven (7) hours at 40 cfs.

Jeff Leighton
Engineering Services Group

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