via: MN Pollution Control Agency

Inflow and infiltration were once big problems for the small town of Good Thunder in Blue Earth County in southern Minnesota. By being persistent and working as a team, city councilors and staff were able to take advantage of opportunities and detect major sources of I & I.

The town of 583 people has a pond system designed to treat an average of 50,000 gallons per day (gpd) of wastewater, and up to 85,000 gpd during wet weather. But a large rain event or spring thaw would result in 300,000 gpd going through the system. That meant many discharges to the Maple River during the spring and fall to keep up with the overload. It also meant extra expenses for Good Thunder and a lot of worry for Brian Severns, wastewater operator for the town.

In the last year, Good Thunder has decreased its influent flow by more than half, saving the town money through:

 

• Less water flowing through the drinking water and wastewater treatment systems
• Fewer hours of staff time managing the system
• Less need for pumping, meaning reduced wear on equipment and lower electrical costs
• Avoiding the cost of buying land and building a new pond to accommodate the hydraulic overload

 “It saves me a lot of worry at night,” Severns added with a laugh.

 

The town took a multi-faceted approach to solving the problem.

 

When the state of Minnesota reconstructed Highway 66 that runs along the eastern edge of Good Thunder, it recommended replacing or lining the town’s sewer main. The town chose lining and that stopped the major source of I & I to the pond system.

 

Good Thunder also worked with the Minnesota Rural Water Association to look for leaks in its drinking water lines. It found many small and one big residential leaks that, once corrected, dramatically dropped the amount of water being treated and pumped for drinking as well as the water flowing to the wastewater system for treatment.

 

In addition, the town inspected sump pump systems, contracted a company to inspect the sewer lines with cameras, and educated residents and businesses on I & I issues through newsletters and utility bill messages.

 

“Even though we got the big stuff, we’re going after the little stuff,” Severns said.

 

Instead of discharging the ponds twice in the spring and three times in the fall, he is hoping that drops to one per spring and per fall. That’s good news for the river too because a longer retention time means a bigger reduction in phosphorus levels in the discharges.

 

Severns has sound advice for other cities tackling I & I problems:

 

• Provide the city council with a visualization of the data behind the problem. Using an Excel spreadsheet, Severns tracked rainfall, drinking water pumped from the town’s well, and water influent to the wastewater system.  He then provided a bar graph of the data to the city council every month so it could visualize the problem and see progress with each step taken.
• Educate residents and businesses on the importance of I & I.
• Use cameras to look for leaks in pipes.
• Take a team approach with the city council and maintenance staff. Severns credits Good Thunder’s maintenance worker, Brian Beckel, with doing much of the work.
• Take advantage of Minnesota Rural Water Association resources. Severns called this association “essential” to the problem-solving.

 

“Patience is a virtue because sometimes it takes a lot of detective work to fix. By doing due diligence, you’ll figure it out,” he said.