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Highland Heights, Silver Grove Target of New SD1 Tanks to Address Overflows

In an effort to eliminate about 21 million gallons of annual sanitary sewer overflows (SSOs), Sanitation District 1 (SD1) hopes to begin constructing equalization (EQ) tanks in Highland Heights and Silver Grove next spring.

The EQ tanks will store excess flow during significant rain events and gradually release the flow back into the SD1 sewer system once the wet weather has stopped. This will minimize the risk of increased volume overwhelming the system and causing overflows, SD1 said in a news release.

“This marks a shift in strategy for SD1,” Executive Director Adam Chaney said. “We are moving toward a controlled storage approach, meaning that we will be strategically storing flow in EQ tanks, pipes and other structures and controlling how and when that flow is reintroduced into our system. This approach, combined with targeted upsizing of pipes, is the most cost-effective strategy to address overflows and meet the requirements of our amended consent decree.”

Under the terms of that agreement, SD1 must completely eliminate all SSOs during a typical year rainfall by the year 2040. Currently, the system experiences about 115 million gallons of SSOs in a typical year. The agreement also requires SD1 to recapture at least 85 percent of combined sewer overflows by 2040.

The Highland Heights/Silver Grove project also includes the construction of new pump stations at both sites. The new pump stations and EQ tanks will reduce about 18 percent of the baseline sanitary sewer overflows established by the amended consent decree.

The two tanks will be located at the intersections of Rt. 8 and Blangey Road in Highland Heights and Rt. 8 and Industrial Road in Silver Grove. The Highland Heights tank will stand about 39.5 feet above ground and hold about 1.4 million gallons when full. The Silver Grove tank will stand about 35 feet above ground and hold about 1.6 million gallons when full.

SD1 officials said the tanks will accept flow only during rain events. The EQ tanks will have flow in them 3-4 days per month, but should only completely fill once during a typical year.

SD1 expects to break ground on the EQ tanks and pump stations next spring pending final approval from the Environmental Protection Agency, and construction is expected to be completed by spring 2022 for an estimated cost of about $10 million.

“We’re excited to begin work on this project,” Chaney said. “This work allows us to improve the quality of our local waterways and make significant progress toward the requirements of our amended consent decree at about half the cost of what was originally anticipated. That’s good news for our ratepayers and our community.”

-Staff report