News Flash


Posted on: September 30, 2019

Smoke Testing in October


The City of Enumclaw has contracted National Plant Services (NPS) to conduct smoke testing within a portion of the City as part of a program to detect leaks within the sewer system.  This work is planned for October 2019 when the groundwater table is lower.  

Inflow and infiltration (I/I) in municipal sanitary sewer systems is a complex and often insidious problem that can often be challenging to control. The City 2019 budget included funding to identify sources of I/I that are creating sewage flows that exceed the pipe full capacity of the City’s system.   If the I/I problem is not addressed then as the system expands, or degrades further with age, larger sewer trunk lines will need to be constructed to convey sewage to the Wastewater Treatment Plant (WWTP).  

Flow monitoring in 2017 and 2018 indicated flow level peaks immediately after commencement of a rain event, indicative of inflow issues. The 2017 flow study looked at flows City-wide and the 2018 flow monitoring focused on the highest I/I areas from the 2017 study.  The basins recommended in the 2018 study for detailed review are proposed for this smoke testing effort and include eight basins mostly centered in the downtown area.  An additional basin not shown below is located west of the high school.  Roughly 10 miles of sewer will be tested or about 20% of the system. 

National Plant will use distribution of individual door hangers in advance of the smoke testing to notify potentially affected residents and businesses near areas where smoke testing is to be performed and will notify the local fire and police authorities of the planned activities. The notices will include information on the purpose of work, smoke testing procedures, precautions to take, what to expect while the work is being performed, and a phone number contact. The smoke that is being used is made specifically for this application and is therefore, non-toxic and non-staining. This work will include accessing some backyards/enclosed fences/gates to look for smoke, as well as smoke testing that will be performed in streets and right of ways.  The City will provide a representative to accompany the National Plant crew when backyard access is required.  

This testing efforts will help locate and quantify the issues causing I&I and facilitate determination of cost-effective strategies to combat these issues. Other methods for detecting I/I sources that may be used in subsequent efforts include dye testing, CCTV inspection, and additional flow monitoring.

Your cooperation and patience during the conduct of this work is appreciated.  If you have questions or concerns, please contact Scott Woodbury at 360-615-5728.

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