Infiltration and inflow (I/I) can cause significant problems for your municipality and its residents. We know that aging infrastructure and limited budgets make it particularly difficult to detect, pinpoint, and remedy the I/I culprits in your sanitary sewer system, however, the long-term issues created by unresolved I/I can add up fast.
Here are a few tips to help your community maintain an efficient and cost-effective sanitary sewer system by identifying, mitigating, and preventing I/I.
Identifying I/I
Inflow is the result of clear water entering the sanitary sewer system through direct pipe connections to the public sanitary sewer (i.e. downspouts, foundation drains, and sump pumps). Infiltration occurs when groundwater enters the sanitary sewer system through pipe defects like open joints, cracks, root intrusions, leaky manholes, and faulty connections.
Credit: CityofMilwaukee.gov
Telltale signs of I/I include:
Excessive spikes in flow during times of heavy rain events
A spike in flow that drops off right away likely indicates inflow
A spike in flow that drops off gradually likely indicates infiltration
Sanitary sewer overflows
Unusual increases in pump run times at lift stations during rain events
If you think you’re experiencing I/I, there are several ways to identify problem areas, including:
Manhole inspections to look for drainage issues, leaky covers, and joint leaks
Smoke testing (during the dry season
Dye testing
Pipe inspections
Flow metering to narrow down problem sewers
Common I/I Remedies
Routine inspections and scheduled maintenance can greatly reduce the likelihood of major I/I problems in your community. This may include:
Replacing manhole covers
Sealing leaky joints
Lining manholes
Developing a clear understanding of your sanitary sewer system is essential to helping you identify I/I. Regular flow monitoring will show the normal fluctuations in your system and allow you to quickly spot issues with I/I before they get out of hand.
I/I Prevention and Mitigation: City of Franklin
The City of Franklin recently noticed a flow increase through their sanitary sewer system. To locate the cause of this increase, the City worked with our experts to dye-water flood the laterals and identify I/I sources, ultimately leading to a full rehabilitation of a neighborhood’s sanitary sewer system. The City was able to complete the rehab work utilizing trenchless lining technology, which reduced the disruption to property owners.
The resulting improvements were so successful in removing the ground water from the sanitary system that the city has had to embark on a ditching and drainage improvement project to address the water that now fills the ditches.
Learn More
To learn more about how you can identify, mitigate, and remedy I/I, please join us for our upcoming seminar, Investigating Infiltration and Inflow.
WHEN: Wednesday, February 19, 2020
WHERE:
Ruekert & Mielke, Inc. • Waukesha, WI
W233 N2080 Ridgeview Parkway
Waukesha, WI, 53188
TOPICS INCLUDE:
Sewer Information Systems
Flow Monitoring Techniques
Sewer Evaluation Survey Programs
Evaluation of Collected Information
Case Studies
Addressing Private Property I/I
Empowering Compliance with Sewer Use Ordinance Provisions
Sewer Rehabilitation Techniques
PRESENTERS:
Taryn S. Nall, P.E.
Jerad J. Wegner, P.E.
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).
