Bayside can blame an April 18 sanitary sewer overflow of nearly 485,000 gallons of wastewater to Indian Creek on an obstruction inside a Milwaukee Metropolitan Sewerage District regional sewer, a district investigation has determined.
The obstruction was a metal sleeve inserted in a 15-inch regional sewer just six weeks earlier to hold a flow monitor in place, according to a district report released to the Journal Sentinel. The district is in the process of installing 150 peak flow monitors in sewers to record the volume of wastewater coming into its system from municipalities during storms.
April 18 was the second consecutive day of torrential rain that week in the metropolitan area, after several days of heavy rain the previous week.
High and fast flows of wastewater in the regional sewer beneath E. Brown Deer Road that day lifted the unfastened edge of the metal sleeve and it "folded over onto itself," the report says. The partial obstruction blocked wastewater from reaching a larger regional sewer at N. Regent Road.
As the Brown Deer Road regional sewer filled to its brim, wastewater rose up manholes several feet above the top of the pipe. This regional sewer collects sewage from village sanitary sewers serving homes and businesses in the northeastern and southwestern sections of Bayside.
Sewage flows in municipal sewers begin to slow and back up — like long lines of cars on entrance ramps to freeways during rush hour — if those pipes cannot empty into the regional system.
Steve Kolowith, owner of Bayside Garden Center, 400 E. Brown Deer Road., walked into the basement of his business at 6:45 a.m. that day and observed several inches of wastewater on the floor. He called the village immediately to report the sewer backup, and then he started pumping the water out, Kolowith said.
"We pumped all day long," he said. Fans, a dehumidifier and bulk liquid sprayers were among the equipment damaged.
Village crews responding to his call started the sanitary sewer overflow around 8 a.m. that day.
They pumped wastewater from two municipal sewers to nearby storm sewers for 61/2 hours in a successful effort to prevent widespread backups of sewage into basements of residences, Bayside Community & Utility Services Director Alex Henderson said in a notice to state environmental officials.
Wastewater flowed to a storm-water pond in the 600 block of E. Brown Deer Road that drains to the creek. The creek flows across the northwest corner of Fox Point and into River Hills before its confluence with the Milwaukee River.
By 2:30 p.m., after wastewater levels in the larger regional sewer along Regent Road subsided, village crews were able to pump wastewater from the smaller 15-inch regional pipe to the larger pipe and end the overflow, according to Henderson.
A district crew was not able to enter a manhole to the 15-inch sewer until April 20. They discovered the dislodged metal sleeve and removed the obstruction.
A prolonged series of storms — April 8 to 13, April 15, and April 17 to 18 — dropped a total of 6.5 inches to 8 inches of rain on most of the district's service area.
Bayside and 11 other communities in southeastern Wisconsin reported a total of nearly 53 million gallons in sanitary sewer overflows in the April 17 to 18 storms. The volume is in addition to the 524.9 million gallons of combined sanitary and storm sewer overflows on April 18 and 19 reported by MMSD.
In Bayside, flows in the 15-inch regional sewer beneath E. Brown Deer Road amount to an average of 580,000 gallons a day when the weather is dry, according to monitoring records. On April 10, when the monitor was in place and recording, maximum flows peaked at a rate of 5.17 million gallons a day, or nearly nine times average day flows.
The excess water is coming from rain leaking into private sanitary sewer laterals or entering municipal sanitary sewers.
Bayside is attempting to gauge the volume of storm water leaking into private laterals, Henderson said.
In 2012, the village lined laterals serving 14 east side homes and will monitor downstream flows to see if the work cut flows significantly, he said. Additional private laterals in other areas of the village will be lined this year as part of an ongoing study.
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