Secondary wastewater treatment restored at Post Point

Temporary bypass installed after pipe failure flooded plant

May 12, 2017 - by Eric Johnston, Assistant Public Works Director

​Following a major loss of a critical pipeline on May 6, the City of Bellingham has been working to provide a temporary bypass and restore full secondary treatment. On Thursday May 11 at approximately 7:30 p.m., the first of four 12-inch-diameter temporary bypass pipes was installed. The bypass pipeline allowed the City to start reactivating the secondary treatment. While it may take several days to bring the secondary treatment process to full functionality, the outlook is positive.

On Saturday May 6 at 1:30 a.m., plant operators at the City of Bellingham responded to a high water alarm in a basement sump pump. Operators observed water approximately 3.5 feet deep in the gallery and flowing rapidly out of the broken pipe. A critical valve was manually closed at approximately 1:40 a.m.  Closing this valve stemmed the flow of water through the broken pipe and prevented a complete inundation of the plant. At least 750,000 gallons of wastewater flooded the underground galleries in the short time between failure and the closure of the valve. 

Despite the major flood and significant damage, this quick action by the operators preserved the operation of the primary treatment, disinfection and solids handling processes.  At no time was there a risk to public health or interruption of service to customers.

 “We are proud of – but not at all surprised by – the quick response of our professional operators on duty when the pipe failed,” Assistant Public Works Director Eric Johnston said. “The alarm system worked as it should so that operators could isolate the problem and rapidly shut down affected systems, preventing potential harm to human health or the environment.”

The failed pipe is essential to the operation of the secondary treatment process. Secondary treatment uses a biological process, or activated sludge, to reduce the organic content of wastewater. The failed pipeline, also known as the return activated sludge (RAS) pipe, helps circulate the biologic mass and maintains the health and viability of the organisms consuming the organic waste. If left unchecked for a long period of time, wastewater with high organic content can potentially be detrimental to water quality and contribute to a reduced dissolved oxygen level.  

“With the restoration of the secondary treatment process, we will see a slow return to high quality waste water treatment,” Johnston said.

Since the last update on May 7, Public Works has completed the following:

  • Installed the first of four temporary bypass pipelines and re-established the secondary treatment process;
  • Made changes in operations to maximize efficiency of the primary treatment and preserve biologic health of the offline secondary system;
  • Continued daily monitoring and testing to ensure the bacteria levels remain extremely low;
  • Removed and replaced equipment damaged by the flooding;
  • Installed temporary air quality monitoring equipment irreparably damaged during the flood; and  
  • Engaged local contractors to assist with stabilizing the existing failed pipe and planning for long-term repairs to the pipeline.

The City is continuing to closely coordinate with the Washington State Department of Ecology and is appreciative of the support they are providing.  Tasks for the next week include an assessment of the costs to restore full functionality and design of the permanent pipe line replacement. 

For previous reports on this incident, check the news tab on the City's website ( For general information on the wastewater treatment plant and processes, contact

Media availability
If there is interest from members of the news media, we will schedule a 30-minute tour of the City's wastewater treatment plant at Post Point and answer any questions. The tour will take place on Monday May 15. Please contact Amy Cloud at (360) 778-7912 or via if you would like to participate in this opportunity.

Media Contact

Eric Johnston, Assistant Director
Public Works

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