Communities served by the regional wastewater collection and treatment system can expect additional help in the next few years to reduce inflow and infiltration (I/I) from private property sources.
Inflow – When clear water enters the wastewater system through rain leaders, sump pumps, or foundation drains that are illegally connected to sewer lines. Inflow is greatest during major storm events.
Infiltration – When groundwater seeps into cracked or broken wastewater pipes.
I/I consumes capacity in the wastewater system, raises wastewater charges to communities, and can be a threat to public health and the environment due to sewage backups and spills.
There are an estimated 7,500 miles of privately-owned sewer service pipes that connect to the regional wastewater collection and treatment in the seven-county metro.
On Nov. 9, the Metropolitan Council accepted the report from a 19-member community task force charged with reviewing the Council’s ongoing I/I mitigation program. The Council authorized staff to implement the report’s recommendations.
Eight report recommendations fall into three categories:
“The discussions of the task force were very impressive,” said Council Member Sandy Rummel, who co-chaired the group. “The conversations were energized, people spoke honestly to each other about their differences, and they were clearly looking for ways to solve problems.”
Overall, the task force recommended that the Council “continue the regional planning policy of balancing regional standards with the needs of local communities to tailor programs to their individual circumstances.”
“The partnership between the Council and communities to reduce I/I is producing solid results,” said Bryce Pickart, Assistant General Manager, Technical Services. “We will continue working closely with communities to implement the new recommendations.”
Developing a model ordinance for communities
Task force member Chad Millner, Engineering Director for the City of Edina, emphasized the need for a model ordinance for private property inspections. Cities must pass local ordinances regarding inspection of private property or to require homeowners to fix leaky pipes.
Prior to 1970, the service lateral (private pipe) leading from a home or business to the city pipe in the street was commonly made of clay. As these pipes age, they deteriorate and the joints tend to start leaking, Millner said.
Private service laterals make up about 50% of Edina’s local sewer pipes. Even if the city repairs all the public sewer pipes, aging private service laterals could still cause the city to exceed its allowable limits for inflow/infiltration into the regional system, he said, and as it stands, the city would be powerless to do anything about it.
“Give us the tools, and we can figure out how to do it in a way that’s appropriate for our community,” Millner said.
The Task Force recommended that the Council work with League of Minnesota Cities, Metro Cities and local community representatives to develop a model ordinance.
I/I reduction demonstration project
Another recommendation in the technical assistance category is development of a private property I/I mitigation demonstration project. Such a project would improve the Council’s ability to measure the effect of I/I reduction efforts, and would be another tool for public education. The Council is beginning to think about the design of the project and will partner with cities to put it in place.
Educating the public on the impacts of inflow and infiltration
The report recommends development of a “robust public outreach program” that would include information about proper maintenance of wastewater collection systems, ownership of sanitary sewer service laterals, and impacts of excessive I/I during wet weather events.
Many residents don’t realize the impact of I/I. “If they haven’t seen a sewage backup in their basement, they probably aren’t aware of the problem,” Millner said.
“Metro Cities is very supportive of having more fully identified tools, best practices, and public education related to I/I,” said Patricia Naumann, executive director of Metro Cities, and a member of the task force. “These are all important pieces that over time can mean continued, significant progress on addressing private property sources of I/I.”
For some communities, financial help is essential
The Minnesota Legislature has provided some financial support for grants to communities to reduce I/I in publicly owned sewer pipes, and some funding in 2013 for private property I/I mitigation from the Clean Water Fund. The issue of private-property-source I/I requires additional, ongoing resources.
The Council has already begun discussions with Metro Cities related to the financial recommendations in the report. The two organizations will work to secure state bond funding and Clean Water Legacy funds to assist with both public and private I/I mitigation projects.
The report also asks the Council to consider providing regional funding, such as a small portion of municipal wastewater fees, to help fund private property mitigation.
“This idea needs further work and exploration,” Naumann said. “There are some differences of opinion among cities in the region about whether regional fees should be used, and what that approach should look like. We’ve secured money at the state level and will continue to advocate for that.”
The Council’s Environmental Services division (MCES) is developing a strategy to implement the recommendations, starting immediately.
I/I mitigation to date has led to reduced peak flows
Work to reduce I/I by communities and the Council to date has had a positive impact on peak wastewater flows, but continued efforts are needed, said Jeannine Clancy, community programs manager for the Council. The Council recognizes that private property infrastructure represents a significant portion of the regional wastewater system and contributes an unquantified and unresolved share of the excessive flows associated with I/I.
Why the region needs to reduce I/I
Some of the major challenges in the region associated with excessive flows attributable to public and private I/I include:
Public and environmental health concerns. When the combined amount of wastewater and clear water exceed the system capacity, untreated wastewater can back up into the basement of buildings or discharge into lakes, streams, wetlands or other areas.
I/I is costly to communities and utility ratepayers. The large regional pipes (interceptors) and wastewater treatment plants are designed for the needs of a growing region. Excessive I/I takes up capacity in the wastewater collection and treatment system intended to accommodate regional growth and increases wastewater treatment costs charged to communities.
I/I wastes the region’s valuable water resources. Clear water discharged to the wastewater system is no longer available to recharge groundwater.