CSO Program Update - 2009
City Engineer, Steve Sperr presented an updated on the CSO Program at the January 6, 2009 City Council meeting. Presentation is available below.
CSO Program Update
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What are CSOs?
CSOs are discharges of untreated wastewater and stormwater released directly into marine waters, lakes, and rivers during periods of heavy rainfall.
Although the sewage in CSOs is greatly diluted by stormwater, CSOs may potentially be harmful to public health and aquatic life because they may introduce toxins and pathogens into these water bodies.
Maps - Click the map to view larger image size in PDF format. With Adobe Reader, use the magnifying feature to zoom in to specific areas of interest.
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Where are the Port Angeles CSOs? Combined sewers remain in many parts of older cities, including Port Angeles. During peak storm events, CSOs are discharged from four separate locations in Port Angeles (see location map).
CSO-1 was eliminated as part of the Crown Park Sewer and Stormwater Project as of January 31, 2005.
The CSOs discharge to storm sewer or overflow pipes that are routed to the Port Angeles Harbor (CSO-6, 7, 8, and 10). Within the past decade, the City has previously eliminated CSO discharge points CSO-2, 3, 4, 5, 9, and 11 as indicated on the map.
Why do we have CSOs?
Up until the 1940s, the standard engineering practice in the U.S. was to provide combined sewers (sewers that carry wastewater and stormwater runoff in a single pipe) to convey wastewater and runoff to the nearest water body where these were discharge occurred with little or no treatment.
Beginning in about the 1950s, separate sewer systems were built for wastewater and stormwater, and in the late 1950s, treating wastewater became the standard practice. Interceptor pipes were built to transport all wastewater (from either combined or separate systems) to wastewater treatment plants. Many of the older, combined sewer pipelines remain in operation throughout the country, including some in Port Angeles.
CSOs occur because these combined sewer interceptors and pipelines have a limited capacity, and intense rain storms cause flows that exceed pipe capacities. Under such conditions, the flow could damage the City's wastewater treatment plant and/or back up into homes and streets. To prevent system damage and sewer backups, specific structures have been built to allow the combined sewer pipes to discharge and thereby relieve the pressure.
Are CSOs legal?
CSOs are legal under the City Wastewater Treatment Plant's National Pollution Discharge Elimination System permit. However, the Federal Clean Water Act and Washington law require that sewer agencies control CSOs as soon as reasonably practicable.
Washington State Department of Ecology regulations provide that a CSO location is considered "controlled" if untreated discharges occur there not more than once per year, on average.
How often do City CSOs occur?
The table below summarizes the total number of CSO events and volume (in gallons) for each of the four remaining CSO sites in previous years.
Annual Reports
In addition to adopting and updating a CSO Control Plan, the City of Port Angeles prepares an annual CSO report and files it with the Department of Ecology.
CSO Water Quality Sampling
In order to accurately assess the impacts of CSO discharges on receiving water quality, the City draws monthly samples at each of the City's five overflow pipelines. Table 1 summarizes the latest biological contaminant sampling data from each CSO discharge point.
CSO Location
CSO Description
Number of Discharges
Fecal Coliform Sampling
Data for 12/8/04 event
(colonies/100 ml)
CSO-1*
4th & N Street
4
Not sampled **
CSO-2
Railroad Ave & Oak Street
11
20,000
CSO-7
Railroad Ave & Laurel Street
15
21,000,000
CSO-8
Lincoln St and 1/2 alley
0
Not sampled **
CSO-10
North end of Francis Street
3
Not sampled
*CSO-1 was eliminated as of January 31, 2005.
** There was not a CSO event on this day at sites CSO-1 and CSO-8.
As part of its public outreach effort, the City of Port Angeles has posted warning signs at CSO locations and at public water access areas nearby.
The signs warn people to avoid contact with the receiving waters during and following heavy rain and include a local telephone number and web site address where the public can obtain more information about CSOs.
Vicinity public agencies are notified during ach CSO event by the City of Port Angeles Public Works Department. These agencies are the Washington Department of Ecology, Washington Department of Health, Washington Department of Fish and Wildlife, Washington Department of Natural Resources, Clallam County Health Department , Port of Port Angeles, and Lower Elwha Klallam Tribe.
CSO Reduction Plan
Under Washington law and administrative regulations, cities with CSOs are required to adopt a written plan for reducing their CSOs. The Port Angeles CSO Reduction Plan has been recently updated and is currently being reviewed by the Department of Ecology.
CSO Reduction Projects
Since adopting its CSO Reduction Plan, the City of Port Angeles has constructed several projects to bring CSOs under control. Six of the original ten CSO discharge points have been eliminated. (See map below and click to view larger image size.)
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The CSO-1 discharge point was eliminated in January 2005 with the installation of a higher capacity pipeline and pump station in this area. The CSO-8 discharge point will also be eliminated within the near future by installation of a stormwater pipeline.
Port Angeles will also be building several CSO reduction projects during the next decade. Future pipeline and pump station improvements in the downtown Port Angeles area will eliminate or reduce CSO-6, 7, and 10 to the Washington Department of Ecology "controlled" level of not more than one discharge per year, on average.
