Why rehabilitate sewer laterals? 

The City Of San Luis Obispo wastewater collection staff conducted a study to address the inflow and infiltration problems experienced during the rainy season.  For short durations during rainstorms, our sewer flows could increase from a daily average of 4.5 million gallons a day to over 30 million gallons a day.  This problem was pushing our water reclamation facility over its design limits.

To develop a solution, staff mapped the City’s collection system and drainage areas by tracing where branch systems tied into trunk systems.  A drainage basin map was created and the city was divided into 14 separate areas.  Each drainage basin was flow-monitored to pinpoint which drainage basin was the biggest contributor to inflow and infiltration.

The largest contributor was drainage basin “area-B”.  The homes and sewer system in this area were constructed from about 1930 to 1965. There are no major commercial structures in the area.  The next step was to video inspect the sewer mains to determine where the defects were and how they contributed to the City's inflow and infiltration ("I and I") problem. 

The inspection phase of the project lasted from 1991 to fall 1994.  We discovered during our main line investigation that the major contributor to I and I is the private sewer laterals.  We observed laterals that were dry during normal season conditions could have flows equal to a garden hose running during rainstorms.  Cross connections with downspouts and yard drains were suspected, but smoke testing revealed that illegal connections were few and far between.

A small sampling of sewer laterals in the area revealed that failures were mostly due to pipe construction materials available at the time the area developed.  The number one construction material problem was orangeburg pipe, with mortared joint failure of clay pipe, number two.  We also learned that the homeowners were consistently having repeat problems with their sewer laterals, although laterals weren’t getting replaced until they completely failed.  

With the data, our department felt the best way to address the "I and I" problem was to institute a sewer lateral rehabilitation program.  The Utilities department conducted community hearings and meetings to help develop our current Voluntary Sewer Lateral Rehabilitation Program (VSLRP).  The program was adopted and implemented in July of 1997.  The program started officially accepting applications for video inspections of private laterals in September 1997. Between 2004 and 2007 the program ran out of funding until July 1, 2007 when the program was reinstated.

Our City preferred that the program be voluntary, because the homeowner owns their lateral from their house to the wye connection at the city main.  The City assumes no ownership of any portion of sewer laterals . The staff wants to groom a positive relationship with its residents rather than an adversarial relationship that would have resulted from requiring lateral replacement. 

Who It Helps

Our program is designed to be mutually beneficial to both the city and the homeowner.  The homeowner benefits by receiving from the city free of charge:  free construction permits, free technical advice and a rebate of  one-half  the cost of replacement or repair up to a maximum of $1,000 per property.   The City benefits from the fixed lateral, (reducing I and I) and a happy taxpayer is more likely to support ongoing capital improvements of our aging infrastructure.
 

Long Term Goals

The city’s long-term goals are to reduce treatment costs of sewage by reducing I and I, and to prevent any more required plant expansions due to capacity issues. These goals also address some environmental issues related to sanitary sewer overflows caused by the collection system being over capacity.  

For more information:

Voluntary Service Lateral Rehabilitation Program - Customer Information

Voluntary Service Lateral Rehabilitation Program - Technical Evaluation and Program Information