I/I Reduction Success – How lateral lining achieved 90% reduction in I/I
BLD Services is proud to have partnered with Jefferson County and Hazen to perform sewer rehabilitation for the Chapel Drive project which achieved outstanding results!
For years, municipal utility managers, public works directors and engineers across the country have realized that in order to mitigate inflow and infiltration (I/I) in the sewer collection system they must adopt a holistic approach to their rehabilitation efforts to include all aspects of the collection system. By only performing mainline CIPP rehab, the groundwater will eventually just get pushed to the next defect in the line, usually to the lateral/main connection.
Industry-leading organizations such as WEF and the EPA, have all published dozens of papers reinforcing comprehensive collection system rehabilitation to eliminate I/I, which not only has a positive fiscal impact on a municipality as less clear water is treated at the plant, but also reduces the occurrence of sanitary sewer overflows (SSO) resulting in a healthier environment for all of us. With the continuous emergence of new technologies in this sector, there are several, financially viable solutions available to municipalities to address the issues they face with their sewer systems. And as documented in this case study, Jefferson County utilized multiple rehabilitation techniques in the Chapel Drive pump station to achieve a result that went far beyond anyone’s expectations.
Background: Chapel Drive Pump Station No.2
Jefferson County Environmental Services Department (JCESD) is responsible for sanitary sewer collection and treatment in Birmingham, AL and the surrounding municipalities. During heavy rain events, JCESD noticed a huge increase in the influent flow rate and SSO’s in the Chapel Drive pump station even though 85% of the mainlines had been previously rehabilitated between 1996 – 2006.
In order to get a better understanding of exactly what issues the County was facing, JCESD teamed up with Hazen and Sawyer for an in-depth asset evaluation of their underground infrastructure. After performing a cost comparison between upsizing the pump station vs. a full system rehabilitation of the basin, JCESD and Hazen determined the most cost-effective solution would be to rehabilitate the remaining part of the system, ultimately less than half the cost of upsizing in this particular case.
After a full assessment of the 15,000 LF of the Chapel Drive basin, which included CCTV of all main lines, manhole inspections, and CCTV lateral launching inspection, Hazen concluded that:
- 26% of the system was newer ductile iron pipe;
- 60% of the main lines had been previously rehabilitated using CIPP;
- 14% was vitrified clay;
- the manholes adjoining the CIPP pipes had also been previously rehabilitated;
- the manholes adjoining the DI pipe were new concrete;
- NONE of the service laterals had been taken into consideration during JCESD’s previous rehabilitation program.
Current Rehab Project
The results of the assessment showed that more that half of the service laterals were inactive, and infiltration was gushing through this connection at an enormous rate. At this point, JCESD concluded that to see a significant reduction in I/I in this pump station, all the remaining issues needed to be addressed, including every service lateral connection.
- CIPP was installed on the remaining 14% of mainline VCP (appox 2000 LF);
- CIPP point repairs were installed to cover inactive service connections;
- open cut method on laterals that had severe structural defects;
- and BLD’s full wrap SCS+L CIPP liner with hydrophilic sealing was installed on the remaining active services.
I/I Reduction Results
JCESDs comprehensive approach, which included upfront spending for lateral launch CCTV to determine the best method of lateral rehabilitation, ultimately saved the County hundreds of thousands of dollars in the short-term and will save millions in treatment, pump run-times, and SSO abatement in the long-term. Preliminary data is already showing a remarkable 90% reduction in volume and 70% reduction in peak flow for the Chapel Drive Pump Station, requiring only minor upgrades to the station and not expensive capacity upgrades which were initially considered. By utilizing a holistic approach to sewer rehab, these results have persuaded JCESD to incorporate lateral rehabilitation into all future projects.