Weathering the Storm: City Measures Infrastructure Impacts from Flooding

In 2023, the City of Traverse City upgraded a a sewer line in the 100 block alley of Front Street and moved it south – away from its vulnerable location along the Boardman River wall. That project may have single-handedly prevented 1.5 million gallons of raw sewage from discharging daily into the Boardman and Grand Traverse Bay during this year’s April flooding. Traverse City commissioners will hear more from staff about how city infrastructure was impacted by the flooding at their 7pm study session tonight (Monday).

City Director of Municipal Utilities Art Krueger and Mark Huggard of Jacobs – the firm that operates the city's wastewater treatment plant – will give a presentation on how recent investments in the city’s water, sewer, and wastewater systems helped prevent a “major environmental event” during the April floods. The presentation is an “opportunity to celebrate the wins the city experienced while weathering” the storm, Krueger says, which “demonstrated the importance of proactive infrastructure investment and long-term resiliency planning.”

The flood was considered a 500-year event, which equates to a 0.2 percent chance “that a flood of this specific magnitude will occur or be exceeded in any single year,” according to the presentation. Until this spring, the previous peak record flow for the Boardman was documented in 2014 at 583 cubic feet per second (cfs). But on April 14, the Boardman surged to 1,120 cfs above Brown Bridge Road – a 92 percent increase over the prior 77-year record. Downtown at the former Union Street Dam site, FishPass water levels “approached a near 500-year flood elevation,” according to Krueger and Huggard, coming within a half inch of those modeled conditions.

However, the FishPass weir was able to convey “significantly greater flows” than Union Street Dam, the duo wrote, which was rated in fair-to-poor condition before its removal. An engineering analysis indicated the old dam could have been overtopped in April, with the potential of structural failure and “uncontrolled flooding of Boardman Lake into downtown,” according to the city. The $25-million plus investment in FishPass “prevented threats to human life and hundreds of millions (in) property damage downtown,” staff said.

Sewer investments in recent years also paid dividends, according to staff. Moving the aging 24-inch trunkline in the 100 block alley of Front Street away from the river wall to the middle of the alley and upgrading it to a 30-inch line was one key project. That multi-million-dollar effort, which won the city a national environmental award from the American Public Works Association, was made because of fears about the vulnerable section of river retaining wall and a possible catastrophic sewer failure.

That turned out to be prescient: During the April flooding, a sinkhole formed in the alley and exposed the abandoned line, which was discovered to have a six-inch hole in it (pictured). Had that pipe still been serving as the main sewer line, an estimated 1.5 million gallons of raw sewage could have discharged daily into the Boardman and Grand Traverse Bay, according to staff.

The city has also invested $1.2 million in lining 9,000 feet of sewer throughout the system in recent years, which helped reduce groundwater infiltration and lowered peak flow contributions at the wastewater treatment plant during the flood. Even still, the plant experienced a 60 percent increase above its normal daily flow in April. During peak flows, the level in the UV channel – which provides a final “zap” to the treated water as it exits the plant – raised to over five feet, meaning a portion of the outgoing flow may have not received that final UV light. However, that system is a secondary level of treatment, with testing showing the discharge remained compliant and the membrane system continued to remove 99.99 percent of E. coli, staff wrote.

All in all, the April flooding demonstrated that “core infrastructure investments matter,” according to Krueger and Huggard. Tens of millions of improvements in recent years “protected public health and safety,” “reduced environmental risk,” “reduced flooding severity,” “maintained utility operations,” and “increased resiliency to extreme weather,” the duo wrote. More projects are still to come, including UV system capacity improvements at the plant, more sewer rehabilitation, climate resiliency integration, a regional approach to planning that includes collaboration with the Watershed Center, and stormwater master planning, according to the presentation.

Also at tonight’s study session…
> Piggybacking on the infrastructure presentation, City Attorney Lauren Trible-Laucht and Grand Traverse County Drain Commissioner Andy Smits will give a “brief overview” of the drainage code and stormwater management, according to Trible-Laucht. The city has been pursuing creating the city’s first drainage district in the Eighth Street area, which has experienced high flows during rain events and quality issues where polluted water runs off into East Grand Traverse Bay – the source of the city’s drinking water. The process to create such a district is a lengthy one, which will be reviewed with commissioners again tonight.

> Commissioners will discuss their planned process for interviewing firms to become the city’s new legal counsel. Commissioners plan to interview three firms – The Kelly Firm, Foster Swift, and Secrest Wardle – at special meetings tentatively scheduled for Thursday and Friday. Staff will also interview the firms, with their recommendations provided to commissioners. Commission interviews are expected to last 45-60 minutes and will be public but not televised. Commissioners are set to deliberate and then choose a firm immediately after the interviews. That company will replace Trible-Laucht, who is stepping down at the end of this month.

> Finally, the board will review city commission rules tonight. Two specific items have been flagged for review, including how agenda items are added and the publication time of the commission meeting packet. Currently, it only takes one commissioner to add an agenda item at a regular meeting (calling study sessions or special meetings requires three commissioners). Commissioners could change that rule to require support from multiple commissioners in order to get agenda items added. The commission will also look at the packet publication rule, which now says packets must go out before 11:59pm Thursday for a regular meeting or 5pm Thursday for a study session. City Clerk Sarah Lutz noted that “because these rules are established by the commission, they may be amended at the commission’s discretion.”

Photo credit: City of Traverse City