Successfully mitigating sanitary sewer overflows involves more than trenchless rehabilitation; it includes catching “red flags” and utilizing multiple technologies

By Robert Cook, Professional Engineer, CH2M HILL, Dwayne Frye, Senior Project Engineer, Knoxville Utilities Board and Sharon Deane, Project Engineer, Knoxville Utilities Board.

Robert Cook, along with co-authors Dwayne Frye and Sharon Deane of the Knoxville Utilities Board will present their paper “Avoiding the Rehab Rut” on Tuesday, July 16 at 3:45 p.m., during the 2013 Kentucky/Tennessee Water Professionals Conference in Louisville, KY. Learn more about CH2M HILL’s participation and presentations at KY/TN 2013.

In the current era of sewer consent decrees and annual rehabilitation programs, it is easy to fall into the “rehab rut” by defaulting to trenchless rehabilitation technologies to mitigate known sanitary sewer overflows (SSOs). It is true that many times SSOs can be mitigated by reducing the amount of rain inflow and ground water infiltration (I&I) into the sewer system through aggressive trenchless rehabilitation technologies.

All too often however, rehabilitation efforts alone will not mitigate the SSOs because of the underlying system characteristics. Such was the case with the Knoxville Utilities Board (KUB) Mini-basins 08B3 and 24B1 which were identified as having multiple reoccurring SSOs along their mainline collector pipe.  The basins have a total of 65,000 linear feet of collector pipe and elevated R values of 9.1 and 13.9 percent, respectively.

In evaluating the basin and reviewing the maintenance history, several “red flags” directed the team to conduct a more detailed analysis of each basin. Our presentation will discuss the concerns that revealed multiple SSO factors that would not have been addressed with trenchless rehabilitation technologies. The engineered solution involved aggressive rehabilitation efforts upstream of the SSOs in conjunction with the downstream capacity improvements.

Utilizing strategic evaluation of system projects is imperative when working on any SSO project. By watching for initial “red flags” and conducting subsequent detailed analyses, project teams can avoid the “rehab rut” and provide a basis for an engineered solution rather than solely relying on rehabilitation technologies.

Robert Cook is a Professional Engineer, currently serving as the local Area Manager for CH2M HILL’s Knoxville Office. An environmental engineer, he has 13 years of experience, specializing in wastewater SSO abatement design and project management involving the rehabilitation and reconstruction of sanitary sewer infrastructure. Cook was recently named as the Tennessee Society of Professional Engineers’ (TSPE) Knoxville Chapter Young Engineer of the Year and is currently serving as the TSPE Knoxville Chapter President.