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.
WHERE ARE THE 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). The CSOs discharge to storm sewer or overflow pipes that are routed to the Port Angeles Harbor (CSO-6, 7, 8, and 10).
CSO-1 was eliminated as part of the Crown Park Sewer and Stormwater Project as of January 31, 2005.
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.
HISTORY OF PORT ANGELES - Combined Sewer Overflows
PRESENTATION by City Engineer, Michael Puntenney - October 11, 2011
This presentation characterizes the historic basis of the City of Port Angeles' CSO problem and the solutions to fix it.
Each city's infrastructure historically developed differently, has different geographical and geological conditions, are in different economic straits, and each must be evaluated for which solution will work best for that community.
We often read in the Press that this is the most expensive project ever undertaken in the City's history, with little emphasis on the elegant, efficient, and economical engineering accomplishment that Brown and Caldwell has created in developing the current CSO designs.
I am certain that this project‘s estimated cost of just under $40M feels extremely burdensome to the citizens of Port Angeles, and should not be taken lightly. However, the project's approach is truly the most inexpensive way to solve the problem, which we will show in this presentation.
Presentation by City Engineer, Michael Puntenney / October 2011
At the end of it, I hope that the Council, council candidates, and citizens of Port Angeles will have the necessary information and be in a position to confidently make a decision on this project, both for what it does for Port Angeles and what it doesn't cost. For any other approach will certainly cost the citizens a great deal more.
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 sewer agencies control CSOs as soon as reasonably practicable. The Washington State Department of Ecology (DOE) is requiring all CSOs into Port Angeles Harbor be controlled by the end of 2015.
DOE regulations say a CSO location is considered "controlled" if untreated discharges occur there not more than once per year, on average.
In compliance with DOE requirements the City measures the quantity and duration of CSO events. These are preliminary wet weather overflow numbers and may not be finalized. See monthly reports for final statistics for current and previous years.
Monthly reports include finalized duration and volume data at each CSO location. In order to assessthe impacts of CSO discharges on receiving water quality, the City draws samples at each of the City's four overflow pipelines. The biological contaminant sampling data is also included in the monthly reports below.
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 each 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.
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 has been approved by the Department of Ecology.
In accordance with its approved CSO Reduction Plan, the City of Port Angeles is on schedule to design and build projects to bring CSOs under control. In 2012, the City is starting construction. For details visit the CSO Construction Page.
Construction of the Phase 1 projects began August 2012. The work includes a large sewer main between Francis St. Park and the wastewater treatment plant, in order to control discharges from CSO 10. Also, a 5 million gallon storage tank will be retrofitted and the industrial outfall formerly operated by Rayonier will be placed into service. Improvements within the treatment plant are included, and force mains from downtown to the treatment plant will be constructed.
Phase 2 includes replacement of pump station 4 (located along Marine Drive), constructing a new sewer main between Lincoln St. and the new pump station, and connecting the pump station to the force mains constructed during Phase 1. Construction of Phase 2 is scheduled for 2014 and 2015. Once the system is operational, Port Angeles will meet the Washington Department of Ecology “controlled” level of not more than one discharge per year, per outfall, on average. Pollution to Port Angeles Harbor will be greatly reduced.
Port Angeles is on schedule to control its CSOs by the end of 2015.
Six of the original ten CSO discharge points were eliminated before 2005. (See map below and click to view larger image size.)
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