Construction, uneven water distribution at Sheboygan treatment facility one reason for overflow last week

SHEBOYGAN – Heavy rain and construction compounded the water levels of Sheboygan’s wastewater treatment facilities that led to an overflow at the end of June.

Partially treated water from three Sheboygan Regional Wastewater Treatment Plant sites reached Lake Michigan and part of Lakeview Park last week, as the city received 7 inches of rain within a few days. The park was closed June 25 and 26 to allow for cleanup.

“That volume of rain in such a short time will always create challenges for the plant,” Wastewater Superintendent Jordan Skiff said in an email.

Ongoing construction led to uneven waterflow through the facility

The facilities were greatly impacted by uneven distribution of waterflow to treatment basins as a result of construction, Skiff said.

The facility has several large structures, between 15 feet and 25 feet deep, that carry waterflow through the treatment process.

Skiff said heavy rain June 22 dislodged a seal that was diverting the water flow to the north half of the plant because the south basins were being kept empty to prepare for structural beam replacement and concrete repair. A contractor planned to start the work in a few weeks, but had scaffolding and equipment in the basin before the heavy rain.

When the south basins began to fill with rain, Skiff said it looked like a “manageable volume” June 25, so WWTP staff tried to divert most water to the north half and planned to drain south basins for the construction.

“Unfortunately, getting 1.95 inches of rain in a two-hour period on Tuesday morning led to high flows that sheeted over the top of the north concrete wall in three locations,” Skiff said.

Water had to be directed to the south basins, washing over the scaffolding. Since then, Skiff said the facility has kept the flows “evenly spread” across basins before emptying them for construction.

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WWTP communicated with the DNR about the overflow incident

The Wisconsin Department of Natural Resources was one of several stakeholders WWTP staff notified about the incident.

Skiff said he’s kept the department informed and filed a report.

The incident will be recorded in the wastewater treatment facility’s 2024 report to the DNR.

Rainfall should be 'manageable' when water levels return to normal

Asked if the city is expecting more overflow incidents, Skiff said rain should be "manageable" in the future. Drier days in the 10-day forecast will allow water flow to return to normal levels for the summertime, he continued, readying the facility to hold rainwater.

Skiff said, “We will only lower the basins again when the forecast is favorable and our daily flows have stabilized."

Sam Bailey contributed to this report.

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