TRAVERSE CITY — Designs are coming together for upgrades to the Traverse City Regional Wastewater Treatment Plant that could cost tens of millions of dollars.
City commissioners on Monday will hear the latest from design team Commercial Contracting Corporation and Fleis & VandenBrink, the firms the city tasked with planning replacements for the plant’s first and last treatment stages.
For $2.2 million, the firms evaluated replacement options for the plant’s preliminary screening equipment, grit separation process, primary clarifying stage and primary effluent pumps. No decisions on the design are set for Monday’s special meeting.
Those are all on the front end of the plant’s treatment process and aim to eliminate debris, sand and grit from sewage before it continues to later treatment stages, plant documents show. After further treatment that includes being drawn through membrane trains that filter out suspended solids and pathogens, the plant’s output is disinfected with ultraviolet light before flowing into Boardman Lake.
That UV disinfection system also needs work, including the raising of its electrical equipment to protect it from damage when water levels are high, documents show. After analyzing a handful of alternatives for each process needing upgrades, the design firms narrowed them down into two different combinations of potential upgrades. One would cost $26.1 million, while the other would cost $35.8 million, according to preliminary estimates.
While the second comes with a higher price tag, it would emit less carbon dioxide over 20 years, cost tens of thousands of dollars less to maintain per year and have a longer useful life. Paying for it would require either a low-interest loan from the Clean Water State Revolving Fund or borrowing money by issuing municipal bonds, the second of which would cost more in interest.
Designs are still at the 30-percent stage, and construction is envisioned for 2025, documents show.