Wastewater plant plans advance

Jun. 23—TRAVERSE CITY — Aging parts of the Traverse City Regional Wastewater Treatment Plant are due for an overhaul, and city leaders just passed what city Municipal Utilities Director Art Krueger called a "fork in the road" in planning for that project.

This week, Traverse City commissioners chose one of two sets of alternatives evaluated by project engineering firm Fleis & VandenBrink. The firm, along with Commercial Contracting Corporation as part of their $2.2 million design contract, considered different options to rebuild the plant's first and last treatment stages, grouped them into two sets and recommended the second one.

Commissioners followed that recommendation, choosing the set of projects over another with an estimated cost of $26.1 million. Despite the smaller price tag, Krueger and project engineers agreed the list of projects had shortfalls and would be "kind of a band-aid approach on old equipment."

"We feel as the design team that the recommendation for (the second alternative) is what should be done for the best interest of the plant in the long term," Krueger said. "And there's many reasons, there's pros and cons to both options."

For an estimated $35.8 million, plans are to build a new headworks with multi-rake bar screens for debris removal, the first stage of treatment at the plant and in the project. The current system lacks redundancy, and water overflows into a bypass channel during peak flow events, according to the engineering firm's report.

From there, water goes into grit removal stages, according to the report. Commissioners agreed to installing a stacked tray grit system, which would remove fine particles at a wide range of flow rates. Existing equipment does poorly at peak flows and is past its expected useful life.

Wastewater then flows into rectangular clarifiers, the report states. Settled solids on the bottom and scum on the top are both pumped to an anaerobic digestion system, while clarified water goes on for further treatment.

The report painted a woeful picture of the clarifiers — fiberglass covers in poor condition, piping showing heavy corrosion, valves that sometimes won't shut and clarifier mechanisms and sludge pumps so old that replacement parts are hard to find. What's more, they don't meet current design standards and a sump pump in the primary pipe gallery that can't keep up with overflows.

Plans are to demolish the existing rectangular clarifiers and parts of the primary pipe gallery, and build two new circular clarifier tanks. New sludge and scum collectors, tank covers, sludge pumps and other equipment would also be installed.

Two existing screw pumps that are also past their useful life — they date to 1971, while a third was overhauled in 2020 — would be replaced with the same types of pump.

After further treatment, including passing through membrane trains, treated water's last stop before flowing into the Boardman Lake is ultraviolet disinfection. The system is also the subject of an administrative consent order from the Michigan Department of Environment, Great Lakes and Energy.

That stems from a 2016 incident when high waters knocked the system offline, as previously reported. It's largely redundant because the membrane trains are so effective, but still required to ensure the plant's outflow is disinfected. Plans are to rebuild the system, which uses vertical UV modules, with a horizontal one that would also add capacity to match the maximum output of some pumps upstream.

Commissioners' 6-1 decision included Tim Werner's vote against. He told the board he wanted to see more data, especially quantitative, to back engineers' recommendation of one set of alternatives over the other. He pointed to a debate from years past over replacing the plant's membrane trains, one that led to their gradual replacement instead of doing so all at once.

Commissioner Mark Wilson said he trusted the expertise of Krueger and others in telling the commission if the alternative is something the plant needs, and that the plant users will get what they pay for — the project will be subject to cost-sharing between the city and townships that use and jointly own the plant's capacity, with the city to foot 55 percent of the bill and the townships, 45, Krueger said.

Both Werner and Commissioner Jackie Anderson said they'd like to see more attention paid to managing stormwater — Werner said stormwater infiltrating city sewer lines is causing issues at the wastewater treatment plant ranging from excess grit to unnecessarily high flows.

City leaders need to track growth both within the city and the treatment plant's service area, and if the wastewater plant's capacity can keep up, Commissioner Heather Shaw said. She pointed to a surge of new hotel rooms in the area as one indicator.

Project engineers should finalize the design by December 2024, and reach a guaranteed maximum price by February 2025, according to city documents. Krueger said after the meeting he expects that price to be at or below the $35.8 million estimate.

Funding options include a Clean Water State Revolving Fund loan, for which Krueger told commissioners the city stands a good chance. He said later that EGLE, which administers the fund, turned down a previous application in 2023. When other cities turned down their funding that year, the wastewater plant project design wasn't far enough along to accept a later offer from EGLE.

Krueger said the city should know by August whether it can borrow the money from the CWSRF. Otherwise, the city could borrow the money by issuing municipal bonds. That would come with a higher interest rate than a revolving fund loan.

But both options would come with annual payments comparable to a loan the city recently paid off, Krueger said. That loan financed the $31-million-plus project in 2002 to install the membrane bioreactor treatment systems. Annual payments cost the city about $2.2 million, compared to early estimates of $2.4 million to pay back a CWSRF loan.

For that reason, Krueger said he anticipates sewer ratepayers will pay more because of the project, but not by much. Rate increases would be based on a future analysis.

"So we're saying it's going to be a minimal impact," he said. "We don't know exactly how much but it's not going to be major."