A new major underground infrastructure project launched in Macomb County will result in fewer discharges of combined sewer overflows into Lake St. Clair following wet weather, Macomb County Public Works Commissioner Candice S. Miller announced Thursday.
“This is a very important project for us in Macomb County,” Miller said. “We are absolutely committed to reducing CSO’s. This project is all about clean water. Clean water equals quality of life.”
Known as the “in-system storage” project, an inflatable rubber dam will be installed inside the 11 1/2-foot-diameter 8 ½ Mile Relief Drain sewer interceptor that conveys the combined stormwater and sanitary sewage from all of Eastpointe and most of St. Clair Shores. When inflated during wet weather, the device acts as a weir to temporarily hold back, or “store”, up to 3.5 million gallons upstream of the dam. As the dam is deflated, the flow is gradually released and continues toward the Great Lakes Water Authority’s wastewater plant in Detroit for full chemical treatment -- instead of discharging it into the Chapaton Retention Basin on Nine Mile Road at Jefferson Avenue. When capacity in the underground basin at Chapaton is exceeded, the combined sewer overflow is treated with chlorine before being discharged into Lake St. Clair.
On Beaconsfield Avenue at Oak Avenue near Interstate 94 in Eastpointe, excavation of a rectangular access shaft which will be about 70 feet by 50 feet has begun. The shaft will be dug to a depth of 35 feet in order to reach the large interceptor pipe and cut away a section of the top of the pipe to install the device. Once installed, the bladder inflates in less than 10 minutes and can be operated remotely by the Macomb County Public Works operations team.
The project follows an engineering study that found CSO’s can be reduced by using space upstream in the interceptor to temporarily store the flow as wet weather and flow volume allows, to reduce overflows into the giant underground basin at the Chapaton Pump Station.
During dry weather, the dam remains deflated to allow for normal flow to the Detroit facility. During rain events, the bladder can be inflated to temporarily hold back the flow to reduce combined sewage overflows.
The project will increase upstream storage volume of 3.5 million gallons without an increased risk of basement flooding in the area and is expected to reduce overflows by 15%. Coupled with earlier operational changes inside the Chapaton Pump Station, CSO’s will be reduced by approximately 40%.
“Every gallon counts,” Miller said. “The engineering study that we initiated for this project is another example of our office being proactive. Combined sewer overflows are permitted by the state, and it’s been going on for decades. However, we just can’t keep doing things the same way. We want to improve Lake St. Clair and protect it for generations to come.”
The project construction cost is $9.9 million, and will be paid using federal, state and county funding under the American Rescue Plan Act with no anticipation of a sewer rate increase for residents and businesses in Eastpointe and St. Clair Shores. The 8 ½ Mile Drain Drainage District serves a total of 92,000 people in the two cities.
Construction is expected to be substantially complete by the end of 2023.
Original source can be found here.
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