Gresham Smith’s System Modeling Helps City of Springfield Balance Overflows
Gresham Smith announces the completion of the major sanitary sewer rehabilitation projects and the start of significant conveyance and offline wastewater storage projects for the City of Springfield. These projects are part of the City’s initiative to fulfill its Administrative Order on Consent (AOC) with the U.S. Environmental Protection Agency (EPA) and eliminate dry weather and wet weather sanitary sewer overflows (SSOs).
The firm’s expertise enabled the City to complete seven rehabilitation projects encompassing nearly 33 miles of sanitary sewers, about 25 percent of the total sanitary sewer system. The City’s goal is to eliminate SSOs, which necessitates effective system maintenance and operations programs to eliminate dry weather overflows and a reduction of inflow and infiltration (I&I) to eliminate wet weather overflows during the design storm event. Thus far, the rehabilitation projects have reduced design storm I&I volumes by 75 percent and reduced peak hour flows by approximately 4.4 million gallons per day (mgd). These projects have also significantly reduced the number of dry weather overflows from 224 per year when the AOC was negotiated to fewer than 15 in 2017.
“Our community is already seeing the benefits of the sewer rehabilitation design and construction work that has been possible through a great partnership with Gresham Smith,” said Terry Beers, director, Springfield Water & Wastewater Department. “After completion of the first phase of sewer rehabilitation work, wastewater treatment plant (WWTP) operators commented on a noticeable reduction in wet weather flow to the plant. The WWTP is receiving the lowest flows since initiation of operation, which ultimately decreases costs and maintenance for the plant. We look forward to continuing to work with Gresham Smith to complete our conveyance and storage projects.”
Through system modeling, Gresham Smith came to an optimal solution that balances rehabilitation, conveyance and storage. To fulfill the remainder of the AOC requirements and eliminate wet weather overflows, the City and Gresham Smith are beginning the conveyance and storage projects. These projects include the design and construction of two new wastewater storage tanks with 4 and 5 mgd capacities and upsizing approximately 16,000 linear feet of trunk sewer line. As the AOC program manager, the firm is serving as Owner’s Agent for the design and construction of the storage tanks and overseeing conveyance projects.
“We are pleased to see such strong results from the rehabilitation portion of our overall improvements and the positive impact that it is having on the Water & Wastewater Department operations and the community at large,” commented Ken Baker, senior vice president and principal, Gresham Smith. “Our ability to put together a highly technical approach that was actionable and has proven effective, with limited comments from the EPA is something we are extremely proud of. We look forward to our continued work in Springfield as we continue to execute on our solutions to fully eliminate overflows to provide the City with a more robust sanitary sewer system.”