For more information about Oregon Department of Environmental Quality projects in the slough, please visit their website.
Combined Sewer Overflows (CSOs) occur in some
areas of the City where the stormwater sewer and
sanitary sewer are combined in one pipe - a combined
When it rains, combined sewer pipes fill up with both stormwater runoff and
sewage. Once the pipes fill to capacity, the excess combined sewage overflows
into the local river or slough.
The City of Portland used
to have 13 CSO outfalls that discharged combined
sewage into the Lower
Columbia Slough. But in October 2000 the Bureau
of Environmental Services completed its "Big
Pipe" project and sewage stopped flowing
in to the Columbia Slough for the first time
century. The elimination of CSOs from the Slough
has greatly increased the health of the waterway.
Local agencies continue to monitor the Slough
to measure the improvements of water quality
the elimination of CSO's from the Slough.
Columbia Slough Fish may be Hazardous to your Health. Fish in the Columbia Slough
contain PCBs and pesticides. These chemicals may effect human development, reproduction
and immune systems. These chemicals may also increase your chance of getting
People most at risk include: unborn babies, pregnant
and nursing mothers, children and people who eat Slough
fish often and for many years. Even though the concentrations
of PCBs and pesticides in Slough fish are fairly low,
they still pose a health risk because these chemicals
increase in the body and my cause health problems
many years after eating the fish.
PCBs and pesticides accumulate in the fatty parts
of fish over the life of the fish. If you do choose
to eat Columbia Slough fish, to reduce health risks
you should avoid eating the fatty parts or the guts.
Bake or broil the fish fillet on a rack so that the
fat drips off, and then do not eat the fat drippings.
TMDL is a term from the
Clean Water Act that stands for Total Maximum Daily
Load. It is an estimate of how much of a particular
pollutant a water body can absorb before it becomes
a problem. TMDLs are established by Oregon DEQ
for every water body that is listed in the Clean
Water Act as a water-quality-limited water body
In 1998 TMDLs were established for the Columbia
Slough for pH, dissolved oxygen, phosphorus, chlorophyll-a,
bacteria, lead, DDE/DDT, PCBs, dieldrin, and 2,3,7,8-TCDD.
Oregon DEQ is working to establish a TMDL for temperature
on the Slough that is scheduled to be completed by