Communities commit to solving wastewater problem

Council defers inflow and infiltration surcharges for one year

Communities with excessive inflow and infiltration (I/I) of clear water into the regional sanitary sewer system are taking action to reduce the problem. A handful have already identified and eliminated the source of inflow in their wastewater systems.

The Metropolitan Council one year ago adopted a program to impose a surcharge on regional wastewater bills starting in January 2007 for communities with excessive clear water flows into the regional wastewater system. Communities could choose to undertake a program to reduce the I/I in lieu of the surcharge.

“The responses couldn’t have been better,” said Bill Moore, general manager of the Council’s Environmental Services division. “All of the communities either submitted a reduction plan or passed a resolution that commits them to creating a work plan and taking action in 2007. It’s a great start.”

Reducing excessive I/I at the local level will lessen the need for more costly construction of regional sewer pipes and expansion of treatment facilities.

closeup of metro area map showing communities I/I status - links to full map

Section of metro area map showing communities' I/I status. See full metro area map with legend (pdf)

Council works with communities to solve problem

The Council identified 49 communities with excessive I/I by monitoring wastewater flow into the regional sewer interceptor system during intense rainfall events between May 2004 and June 2006. The flows were compared with flows during periods with average or no precipitation. Communities were notified in July 2006 and had until Sept. 15 to submit work plans and credits for work already completed. The Council evaluated the submissions and responded to the communities in November.

The Council created an online “toolbox” that provides potential solutions to communities who are working to reduce I/I. During 2007, communities can submit documentation to the Council of expenses for I/I reduction activities. If the expenses are deemed eligible, the costs are credited against the surcharge, explained Kyle Colvin, assistant manager of the Council’s engineering planning group.

The Council will continue to monitor I/I during rainfall events and, if a community reduces its I/I below an established threshold, the Council will suspend the surcharge for two years. If the community maintains levels below the threshold during the two-year period, it can get out of the program entirely.

Starting in 2008, the surcharge will continue to apply to communities that do not eliminate excessive I/I in 2007. However, these communities can continue to get reductions in the surcharge for eligible expenses until they’ve solved the problem. Clear water in system reduces future growth capacity

Clear water getting into wastewater pipes

reduces capacity in the regional wastewater collection and treatment system and, in intense rainfall events, can cause sewer backups and overflows. In the future, excessive I/I could — if not reduced — limit growth in the region. If successful, the Council’s program will help the region avoid these problems with local investments estimated at $150 million. Adding capacity at the regional level to collect and treat the excess clear water would cost more than $900 million and may not have even been feasible because of capacity constraints at the Metro Plant in St. Paul.

“We’re getting a big problem taken care of that at one time we weren’t sure was solvable,” said District One Council Member Roger Scherer. “The program is progressing and the work is getting done.”