By Melinda Baird, email@example.com
Designs for the roughly $5 million improvements planned for the city of Dexter’s wastewater treatment plant are 60% complete. Fleis & VandenBrink’s project manager Dave Harvey provided the city council with an update of the project during a February 12 work session.
The firm was hired last year to study the headworks and tertiary filtration system at the city’s wastewater treatment plant after Public Works Superintendent Dan Schlaff reported serious concerns. F & V’s report and recommendations were submitted to the council in August. In December, the city announced its intent to issue general obligation limited tax bonds in an amount not to exceed $5.5 million to fund the project.
The system, constructed in 1977, is dependent on two unreliable, and now obsolete, screw pumps responsible for pumping wastewater to the primary and tertiary treatment systems. Both are failing, Schlaff has reported.
At the “head” of the plant, the grit removal system responsible for removing larger debris from incoming sewage has been non-functional, requiring workers to manually remove grit. Improper grit removal has led to early wear and tear on plant components further down the process stream not intended to deal with larger debris.
“So [these improvements] means folks won’t have to be hanging off the catwalk of the primary clarifiers with a butterfly net?” councilman Zach Michels quipped, referring to the precarious and practically impossible task of manually removing grit.
Also, in the final step of the treatment process the wastewater flows through sand filters, which are an important part of phosphorous removal. With a failing steel structure that can no longer be repaired, the sand filters won’t be adequate to meet new state phosphorous discharge limits.
F & V has recommended replacement of all process equipment that has reached the end of its useful life, including installation of a new influent and effluent submersible pump system to replace the screw pumps, new cloth-media disk filters to replace sand filters, and new screening and grit removal at an estimated total cost of $5.1 million.
The project involves tearing down existing structures and tankage then constructing a new Headworks building, allowing realignment of the roadway for tanker trucks, Harvey said. The building is designed to add extra equipment in the future should, for example, the city annex Baker Road property for development, sewer lead operator Eric Hartman confirmed.
To be clear, the currently planned capital improvements to the wastewater treatment plant won’t accommodate additional users, but rather replace failing equipment with a more efficient, cost-effective system that will also meet new state regulations – and will prepare the system for possible future capacity upgrades.
Designs for the system are anticipated to be complete by the end of March, at which time the city will solicit construction bids. Council will set the actual amount of the bonds that will be sold after the bids are received. After the closing on the bond scheduled August 7, construction will begin. Substantial completion of the project will likely occur in early October 2019.
The city’s original wastewater treatment plant was constructed in 1977 and converted to a conventional activated sludge plant in 2000. An equalization basin was constructed in 2009 to store high flows during wet weather events and, most recently, an anaerobic digester was upgraded for better biosolids treatment.