The City of Franklin had one subdivision that was experiencing unusually high peak to average sewer flows. A hundred homes were 1950’s vintage, the subdivision was rural cross section with ditches, and there were known homes with hung plumbing and possible cross connections. The Milwaukee Metropolitan Sewerage District (MMSD) had notified the City that peak flows within the subdivision sewershed were non-compliant and that the City would need to address the issue and fix the sewers.
The City began by televising all of the sanitary sewer mains within the subdivision and determined there were a number of defects within the mains that needed repair. The defects consisted of cracks and separated joints that were not severe enough to warrant an open cut rehabilitation. The City decided to line every main with cured in place pipe (CIPP) and then anxiously awaited the updated flow metering results. Much to everyone’s disappointment, the peaks were still there.
Next, the City turned to the private property part of the system and investigated the laterals and performed interior and exterior home inspections as part of the MMSD Private Property Inflow and Infiltration Program. The inspections and corresponding rehabilitation were funded through the program with no costs to private property owners, so the City saw a 100% participation rate.
The inspections showed that the laterals and private property were the source of clear water into the system. The City embarked in a three-year rehabilitation project that lined or open cut replaced every lateral within the subdivision. In addition to the laterals, the illegal clear water connections were disconnected.
The flow meters were installed after the projects were completed and the results speak for themselves. Gone are the peak flows that were indicative of inflow and infiltration as a result of rainfall events in the adjacent area. The project was a success in removing clear water from the sanitary sewer system.
Unintended Consequences
There is an old term – “no good deed goes unpunished”. The clear water that was removed from the sanitary sewer system didn’t just disappear – it collected in the utility trenches and eventually made its way to the surface and collected in the ditches. The surrounding area doesn’t allow for simple grading of the ditches and directing the storm water to a nearby outfall, so the City is working with Ruekert & Mielke, Inc. (R/M) on a design of underdrains and storm sewer that will direct the storm water and clear water flow toward a new basin that will be constructed.
This storm water project will be constructed in spring and will result in a sanitary and storm sewer system that is essentially new and will function as the original system from the 1950’s was intended to.
Learn More
R/M is hosting a seminar next month in our Waukesha office and in Menasha at the Elisha D. Smith Public Library that will cover these methods and when they should be considered. Click here to learn more.
About the Author
Jerad J. Wegner, P.E.
Team Leader/Project Manager
Jerad has extensive experience with a wide variety of projects, including street and highway design, intersection analysis, transportation facilities, storm sewer design, storm water management plan and review, sanitary sewer design, sanitary sewer capacity analysis, sanitary sewer rehabilitation, water main design, plan reviews, cost estimating, quantity take-offs, State and County permitting, and on-site construction review of sanitary and storm sewer, water main, pavement and curb and gutter. Jerad is PACP Certified (Pipeline Assessment Certification Program).
