Back one level
 
CSO

Combined Sewer System

 

The Everett wastewater collection system is divided into two distinct areas: a northend combined sewer system, and the southend separated sewer system.

 

Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe.  Most of the time, the combined sewer system conveys all of the wastewater to the Everett Water Pollution Control Facility, where it is treated and then discharged to either the Snohomish River or Port Gardner Bay.  During periods of heavy rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system.  For this reason, the combined sewer system is designed to overflow occasionally and discharge directly to the Snohomish River or Port Gardner Bay.  These overflows are called combined sewer overflows (CSOs).

 

Combined Sewer Overflows (CSO) Frequently Asked Questions

 

Why do we have CSOs?

How many CSOs are there in Everett and where are they located?

How do I know where there might be a CSO event?

What does the warning sign look like and what does it mean?

What will happen if I go in the water within 24 hours after a heavy rain near a CSO sign?

What if my dog goes in the water within 24 hours after a heavy rain near a CSO sign?

Will I get sick from eating the fish I catch near these signs?

Will my wetsuit protect me when scuba diving or windsurfing?

What can I do to keep local water safe and clean?

 

 

Why do we have Combined Sewer Overflows (CSOs)?

The combined sewer system in the north end of the City was largely constructed between 1890 and 1963.  The system was designed to convey sewage, horse manure, street and rooftop runoff, and garbage from city streets to the nearest receiving body of water.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

Prior to 1960, the combined sewer system discharged directly to Port Gardner Bay and the Snohomish River through numerous outfalls without treatment. A system of gravity sewers, lift stations, force mains, and regulators was constructed in the early 1960s to intercept these outfalls and convey the sewage to treatment lagoons. The interceptor sewers and lift stations were sized to accommodate all of the dry-weather flows and part of the stormwater runoff.  Excess combined sewage resulting from stormwater, overflows either to Port Gardner Bay or the Snohomish River.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

The advantage of the combined sewer system is that, most of the time when rainfall is low to moderate; both the stormwater and wastewater go to the treatment plant before being discharged to Puget Sound.  The disadvantage is that during heavy rains, untreated stormwater and wastewater may be discharged at combined sewer outfall locations.

Return to questions 

 

How many combined sewer outfalls are there in Everett and where are they located?

There are thirteen combined sewer outfalls in Everett. Click to see map. 

Return to questions

 

How do I know where there might be a CSO event?
Click here for real time overflow monitoring.  The symbols relay real time information from the City of Everett’s computerized system that monitors the wastewater system. 
(Once on the monitoring page, add it to your favorites or create a bookmark if you wish to return to it regularly.)


The CSO locations are identified by signs which are posted near each outfall. Click to see sign.


These signs warn people not to swim or fish at these outfalls during rainstorms or for at least 24 hours following rainstorms. CSOs contain bacteria and pathogens that could make someone sick if they swallow water or eat fish that have come in contact with CSOs.
Return to questions


What will happen if I go in the water within 24 hours after a heavy rain near a CSO sign?
Most people will not get sick from just getting contaminated water on their skin.  The biggest risk is from getting tainted water from an overflow in your mouth.  The bacteria in untreated sewage might make you sick, especially if you are already sick or have low immunity.  In general, young children and elderly people may have a higher risk of getting sick.

Return to questions

 

What if my dog goes in the water within 24 hours after a heavy rain near a CSO sign?

Animals are usually not affected, but if your pet does go in the water during an overflow, be sure to give it a good bath as soon as possible.  If your pet is very young or old, it could be at higher risk.  If your animal develops diarrhea, you should withhold food, and consult your veterinarian about what to do next.

Return to questions

 

Will I get sick from eating the fish I catch near these signs?

It is advisable that you not eat bottomfish caught near a CSO sign, because the sediments can be contaminated with chemicals from many years of pollution.  Bottomfish (such as flounder, sole, rockfish and cod) may carry levels of contamination from long exposure to contaminated sediments.  Eating these fish frequently may increase your risk of cancer and other chronic diseases.

Return to questions

 

Will my wetsuit protect me when scuba diving or windsurfing?

Wetsuits are an added protection for your skin.  If you do go in the water near an overflow location during or after a heavy rain, don’t get water in your mouth and wash yourself and your wetsuit with hot water and soap as soon as possible.

Return to questions

 

What can I do to keep local water safe and clean?

Remember that what goes down drains may go into lakes, streams or Puget Sound.  We can all help by:

  • Keeping paints, oils and pesticides out of storm drains
  • Fixing leaks from vehicles
  • Taking cars to a commercial car wash that recycles water before going to the treatment plant

If you wash your own car:

  • Wash it with biodegradable soap over grass or gravel
  • Use a bucket and a hose nozzle to limit the amount of soap and water used
  • Wash only the outside of the car, not the engine 

Click here: Stormwater Protection for additional information about Stormwater and Stormwater Protection including volunteer opportunities.

Return to questions

 
calendar Getting to Everett SiteMap Legal Stuff Community Movies Experience Everett  
Back to main site