Inflow and Infiltration
Minnetonka’s wastewater collection system under scrutiny
Minnetonka, often on the forefront of environmentally friendly actions, now finds itself facing another challenge—reducing its flow of clear water into the Met Council’s overburdened sanitary sewer collection system.
The cause of the problem is the flow of clear water such as rain water or groundwater into the sanitary sewer system—commonly called inflow and infiltration or I and I. During major rain events, this additional surge of water can consume the capacity of sewer pipes resulting in home backups and overflows into creeks and wetlands in addition to the Mississippi River.
A flow study completed in 2005 identified a number of areas in the community that contribute to the problem. To encourage communities to address this issue, the Met Council is implementing a surcharge for the excess flow. Under the currently proposed surcharge system, Minnetonka will be charged about $377,000 annually to treat the city’s waste.
That’s the bad news.
The good news is the city has five years to correct the problem. During that time, the city can use the money it would have paid in surcharges to implement an education, inspection and repair program designed to reduce the I and I problem. This will include home inspections to identify sump pumps and foundation drains that might be incorrectly connected to the sanitary sewer system. The city is developing a grant program that will assist home owners with the costs of repairs if corrections need to be made. In addition, a thorough inspection of the city’s manholes by a consultant engineering firm has already begun, to be followed by inspection of sewer lines and lateral connections.
At the same time, residents will receive new water meters which will allow for automatic reading of the meter and can provide residents with more timely information on water use.