Policy 11: Inflow and Infiltration Policy
Inflow and infiltration is systematically addressed in the regional wastewater conveyance system to reclaim and ensure capacity, improve efficiency, and better utilize capital funds.
Inflow and infiltration is stormwater and groundwater that makes its way into sanitary sewer pipes, mixes with sanitary wastewater, and gets unnecessarily treated at water resource recovery facilities. Inflow is clear water that enters the wastewater system through rain leaders, sump pumps, or foundation drains that are illegally connected to sewer lines. The largest amount of inflow occurs during heavy rainstorms. Infiltration is groundwater that seeps into cracked or broken wastewater pipes.
Unaddressed inflow and infiltration can cause public and environmental health concerns, mainly through sewage backups resulting from limited system capacity. It can be costly to communities and utility rate payers through both increases in billed volume of water treated at the water resource recovery facility and additional investments to expand the system to accommodate capacity.
Inflow and infiltration from private property has been an under investigated and under-supported area of mitigation. Mitigation efforts have not been as robust primarily due to a lack of dedicated and reliable funding sources to incentivize this work. Opportunities abound to address inequities in historically marginalized and overburdened communities due to the high costs of private inflow and infiltration remediation and risks of displacement when those concerns are not addressed.
Environmental Services continually works to maintain the capacity of the conveyance and treatment system to prevent unnecessary, costly expansions. Efforts like private and public inflow and infiltration mitigation, regular assessments and maintenance of wastewater infrastructure, and support of water conservation efforts are all successful ways to maximize the current conveyance and treatment capacity and reduce premature costs.
Climate change has the potential to impact these efforts to keep clear water out of the wastewater conveyance and treatment system. Changing precipitation patterns may stress the regional conveyance system and could lead to increasing issues with inflow and infiltration. Rising groundwater levels could inundate pipes that were originally above the groundwater table. With the uncertainty of climate change impacts, it is critical to continue addressing inflow and infiltration to reclaim capacity in the conveyance and treatment system.
Desired outcomes:
- Ongoing inflow and infiltration mitigation work results in reclaimed capacity in the wastewater conveyance and treatment system.
- Capacity enhancements are not made to accommodate excess inflow and infiltration.
- Municipalities are supported in both public and private efforts to reduce inflow and infiltration.
- Funding is consistent and reliable for inflow and infiltration mitigation efforts.
Actions
Actions are grouped under the categories of Partner, Plan, and Provide to better tell the story of how policy produces results.
Partner
- In partnership with communities, continue developing inflow and infiltration goals for all communities served by the regional wastewater system.
- Partner with the state to make funds available for inflow and infiltration mitigation and promote statutes, rules, and regulations to encourage inflow and infiltration mitigation.
- Continue to support, advocate, and coordinate with Metro Cities for state bond funding for municipal public system inflow and infiltration grants.
- Continue to advocate and seek funding for communities working to reduce inflow and infiltration from private property sources.
- Partner with our Housing and Livable Communities division to develop criteria to prioritize private property inflow and infiltration grant funding to applicants that show a dedicated effort to prioritize low-income and historically overburdened households.
Plan
- Limit expansion of wastewater service within communities where excessive inflow and infiltration jeopardizes the Met Council’s ability to convey wastewater without an overflow or backup occurring or limits the capacity in the system to the point where the Met Council can no longer provide additional wastewater services. The Met Council will work with those communities on a case-by-case basis, based on the applicable regulatory requirements.
- Coordinate private sewer lateral rehabilitation with other programs, projects, or construction that may provide an opportunity to address multiple infrastructure needs, for example, lead service removal programs or street improvement programs.
Provide
- Met Council facilities and interceptors will be maintained and rehabilitated to minimize inflow and infiltration.
- Institute a demand charge for those communities that have not met their inflow and infiltration goal(s), if the community has not been implementing an effective inflow and infiltration reduction program as determined by the Met Council, or if regulations and/or regulatory permits require Met Council action to ensure regulatory compliance.
- Use the demand charge to cover the cost of wastewater storage facilities and/or other improvements necessary to avoid overloading Met Council conveyance and treatment facilities and for use of capacity beyond the allowable amount of inflow and infiltration.
