UPDATED/CORRECTED CSO ADVISORY: Combined sewer overflows (CSOs) on Wednesday, September 20

(September 21, 2017) - Heavy rains caused Portland’s combined sewer system to overflow to the Willamette River on Wednesday, September 20 from a SE Portland pump station that is slated to be improved and expanded. Overflows occurred at 4:15 a.m., 2:33 p.m., and 3:01 p.m. to the Willamette River from the SE Alder Street Pump Station at SE Alder Street and Water Avenue. https://goo.gl/maps/kmdmYw57pD22. The morning overflow lasted for about four minutes, and the afternoon overflows lasted for a total of about 30 minutes.

An overflow did not occur, as previously reported, at N Edison & Philadelphia.

UPDATED CSO ALERT:

(5 p.m., September 20, 2017) – Heavy rains caused Portland’s combined sewer system to overflow to the Willamette River beginning at around 2 p.m. at N Edison & Philadelphia. Officials estimate that less than 100 gallons overflowed. The event lasted for approximately one minute.

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EARLIER ALERT: Four-minute combined sewer overflow (CSO) occured to Willamette River from pump station slated for upgrades

(September 20, 2017) – A combination of stormwater from heavy rains and sewage overflowed to the Willamette River for four minutes early this morning from a SE Portland pump station that is slated to be improved and expanded.

The CSO (combined sewer overflow) occurred at 4:15 a.m. from the SE Alder Street Pump Station at SE Alder Street and Water Avenue. https://goo.gl/maps/kmdmYw57pD22.

The pump station, built in 1952, is being upgraded and will be taken offline by October for two years of construction.  The upgrades will improve reliability and increase pumping capacity to prevent sewage releases into buildings and streets as well as overflows to the river. For more information on the project, please visit: https://www.portlandoregon.gov/bes/72747.

CSOs are rare, but when they occur the public is advised to avoid contact with the river for about 48 hours due to increased bacteria in the water. In this case, the public is advised to avoid contact with the Willamette River from the Morrison Bridge to the Columbia River confluence until this advisory is lifted.

Areas upstream are not subject to this advisory.

The event began at 4:10 a.m. and lasted for four minutes, discharging about 3,000 gallons. A combined sewer overflow is about 80% stormwater and 20% sewage.

Since completing the Big Pipe project in 2011, a 20-year $1.4 billion program to reduce overflows, the number of CSOs have been reduced by 94 percent to the Willamette River and 99 percent to the Columbia Slough.  Before the project, CSOs occurred an average of 50 times a year, with some instances lasting days. Today, the combined system overflows to the Willamette River an average of four times per winter and once every three summers.

For more information about CSO events, what they are and why they occur, visit https://www.portlandoregon.gov/bes/article/565061.

The Bureau of Environmental Services works with Portland residents and businesses to protect water quality, public health, and the environment through wastewater collection and treatment, sewer construction and maintenance, stormwater management, and stream and watershed restoration. For news updates, follow @BESPortland on Twitter and visit www.portlandoregon.gov/bes/news