Blue Heron Sanitary Sewer Rehabilitation WO #016

The City of Lake Oswego has begun the rehabilitation of several wastewater collection lines in the Blue Heron neighborhood.  This project is an essential component to the City’s commitment to provide an adequate wastewater collection system to meet the demands of today and tomorrow.  The project will be accomplished in two phases. 

The first phase is the investigation.  To determine the condition of the main lines and private service laterals, the City will survey the area and perform television inspections of all the lines.  We are aware that some of the lines are undersized and quite old.  Other possible problems could be lines that have settled and now have flat spots or bellies.  Since wastewater collection lines flow via gravity it is important that all lines have what we call positive slope between manholes.  In other words, the wastewater must flow down hill.  Another problem we face is root intrusion.  Roots form blockages in lines and can cause backups of the wastewater into private residences.  Often as lines age they can crack and break apart.  These cracks allow clean groundwater, which must be treated, to seep into the line.  This groundwater increases the volume of wastewater the City pays to treat, thus increasing the fees to the citizens.  By decreasing the amount of clean groundwater in our wastewater lines we can lower the costs to our citizens.  These are some of the problems we will be looking for in our investigation.

Phase two involves repairing any problems discovered in the investigation. Based on the nature of the problem we have several methods of rehabilitating the line.  A liner can be pulled from manhole to manhole to give the interior of the line a smooth, crack free surface.  The process will utilize a process similar to that shown in this cured in place plastic

link.  Another method is known as “pipe bursting.”  A new pipe made of high density polyethylene (plastic) is pneumatically pushed through the concrete line, obliterating the existing line (check out the pipe bursting process here).  The worst case scenario is excavation and removal of the old line and laying a new line.  The first two methods are preferred, but the condition of the line determines the method of rehabilitation. 

Affected Streets

Blue Heron Neighborhood

Funded by

This project is funded from the wastewater collection fees (bi-monthly sewer fees). 

Current Status

This project is substantially complete.  Currently, the City has identified a line segment in need of rehabilitation.  The contractor will be remobilized to the site in late November to complete the work.   If you have any questions about this project, please contact Matt Tipton, Engineering Technician or call him direct at 503.675.2533.