Heavy rainfall event results in sanitary sewer overflow
In order to protect Viroqua property owners from sewer back-ups, the City discharged wastewater from the collection to adjacent high flowing waterways. 24,000 gallons were discharged from a manhole on Rock Avenue and 18,000 gallons were discharged from the Lincoln Street Lift station. The wastewater was discharged on Wednesday, July 15th from 8:15 PM – 9:30 PM. The waterways enter the Springville Branch of the Bad Axe River and Bishop Branch of the West Fork of the Kickapoo.
The discharge was a result a short duration, heavy rainfall event that occurred starting at 7:00pm. In total, 4.4-inches of rain fell in less than 1 hour. This rainfall was preceded by an 0.5-inch rain event that happened midday, which saturated the soils, contributing to excessive clear water entering the collection system. Older wastewater collection systems, as seen in Viroqua, can take on large volumes of rainwater during high rain events. This causes excessive flows in the system. To prevent sewer back-ups in properties, the City relieved the system lift station and manhole by pumping some of the flow to adjacent storm waterways. These waterways were also receiving high volumes of rainwater at that time.
Wastewater releases to the environment are a last resort. The impacts are lessened in situations of heavy rain by the large volume of rainwater in the storm waterways and the large amount of rainwater in the wastewater itself. While no discharge of wastewater is good, the rainwater helps to dilute the wastewater which reduces impact to the environment.
The City continues to work on upgrading the wastewater collection system to minimize impacts of heavy rain events through reconstruction and sewer lining projects. Property owners can help by ensuring only wastewater is entering the sewer system and by removing any roof drains or other clear water connections to the sewer system. The City has also implemented at Clearwater Inspection Program to limit the rainwater entering the system. You can find the City’s clear water inspection program at http://viroqua-wisconsin.com/city-of-viroqua/departments/water-sewer/sewer-department/clear-water-inspections.