Traverse City commissioners will receive an update tonight (Monday) on progress being made to address sewer overflow issues in the city, notably those caused by water inflow and infiltration affecting city pipes. Commissioners will also discuss an upcoming tree-trimming project around a major transmission line running from Barlow Street to Parsons Road, vote on approving allowing schools downtown, and considering using $160,000 to give staff additional paid time off at the holidays in recognition of their work during the pandemic.

Sewer Pipes
Significant rainfall events and high groundwater have contributed to infiltration and inflow into city pipes, causing excessive flows in the city’s sanitary sewer system, according to an update from consultant Hubbell, Roth & Clark (HRC) that will be presented to commissioners tonight. Inflow occurs when water gets into the system through manhole covers or illicit connections from roof drains or basement sump pumps to the system. Infiltration occurs through cracks or loose joints in pipes when surface water seeps into the ground and forces its way into the pipes. Infiltration is a particular risk when the pipe is submerged by groundwater, which puts pressure on the pipe. HRC’s report notes that the most intense infiltration is “observed in sewers installed at lowest elevations,” with downtown Traverse City essentially sitting in a basin surrounded by higher elevation areas.

According to HRC, limited capacity during high-flow events in the 24-inch sewer downstream of the Boardman River siphon is causing surcharging. High lake and groundwater levels are impacting the pipes, as is climate change, according to the report. “Climate change is directly correlated to a slower movement of storms, which increases the intensity and total rainfall of a storm event,” HRC wrote. “In Traverse City, high-intensity rainfall events with greater than 25-year frequency (i.e. four percent probability) occurred multiple times in the West Front sewer system from May 2020 to July 2021, which stresses the capacity of the city’s maintenance staff and installed infrastructure.”

The city and HRC have begun flow monitoring in the downtown sewer system and are working to identify both short and long-term solutions for addressing overflows. Work completed to date includes sewer lining on East Front Street, replacement of sewers in the South Cedar area, maintenance of storm sewer outlets in the Elmwood Avenue area, the sealing of manhole covers, and grant applications for funding to continue upgrading the city’s infrastructure (the city was recently approved for millions in low-interest state loans for wastewater repairs).

HRC’s report notes that private laterals – or the pipes that connect a home's private plumbing to the publicly-owned sanitary sewer line – can comprise up to half the length of a sewer system. Cracked or broken laterals can be a significant contributor to infiltration and inflow. To address the problem, the consultant recommends that when the city tackles sewer main replacement projects, it should also replace laterals between the main and the edge of the right-of-way. The city should also encourage homeowners to replace aging service laterals, according to the report. In addition to those steps, HRC outlines several next steps ahead for the city to address overflow issues downtown, including completing a CCTV inspection of the 24-inch trunk sewer near the Front Street lift station (pictured), completing sewer rehabilitation or replacement in “critical sewer areas” with high inflow and infiltration, completing a full-scale sewer model for West Front Street using the flow data collected, and completing an evaluation survey to identify sources of inflow and infiltration.

City Commissioners Brian McGillivary and Tim Werner requested that the update be on tonight’s agenda, noting that inflow and infiltration issues cost “the city hundreds of thousands if not millions of dollars annually in treatment and backups. Besides the devasting environmental impacts, these events have negative impacts on the city economically and cause city residents to mistakenly blame the problem on overdevelopment.” McGillivary and Werner said that rather than focusing “on the low-hanging fruit of inflow, such as illegal sump pumps,” the city should look at action steps to address “the documented problem of infiltration from private sewer leads.” The commissioners added: “We recognize this death from a thousand cuts is a much more difficult problem to address with no simple fix. But the math is obvious. If you have 10 leaky 4-inch leads in a 500-foot section of main, fixing the leaks in the main will not address the problem.”

Also on tonight’s commission agenda…
> Commissioners will hear details on an upcoming Traverse City Light & Power (TCLP) maintenance project around a major transmission line running from Barlow Street to Parsons Road. According to staff documents, approximately half of the utility’s 13,000 customers are serviced by the transmission line, and a substation fed by the line is the main backup feed for all of downtown. The distribution circuit is also the main backup feed for the airport industrial park and the air traffic control tower. Without maintenance, there are several public safety risks related to the line, including downed high voltage lines, sparks from trees contacting energized lines, and stray voltages, according to staff documents.

TCLP will be undertaking a tree trimming and brush mowing project to clear the areas surrounding the transmission line. The mowing area will be on a section of line on Grove Street between Rose Street and Barlow Street. Staff will put up warning signs along the walking path at both Rose and Barlow streets and all streets in between, though the TART Trail will remain open in the area. Spotters will be used to “aid in traffic control and pedestrian control to assure the public is safe during the work,” according to staff documents, with other work completed using bucket trucks and wheel feed chippers. The mower that will be used on the site has a trap door on the front to deflect debris downward instead of forward, “keeping flying debris to a minimum.” While the project could be visually impactful – staff photos of similar line maintenance projects show wide ground clearance around lines ranging from 20-100 feet, as well as a broad aerial buffer – the project also calls for a restoration component to include planting native shrubs such as highbrush cranberry, blackhaw viburnum, and common lilac.

> Commissioners will consider voting to approve an ordinance change that would allow schools and universities to operate in the downtown district. The proposal has already been approved by the city’s planning commission and was discussed at a previous meeting by city commissioners, who voted 5-2 on October 11 to schedule an enactment vote for tonight’s meeting (Commissioners McGillivary and Roger Putman were opposed). Assuming commissioners vote along the same lines again tonight to formally approve the proposal, the change will go into effect eight days after the city posts a notice of adoption. The move will allow The Children’s House to relocate its junior high school to downtown Traverse City.

> Commissioners will consider a recommendation from Mayor Pro Tem Amy Shamroe to provide city staff with additional paid time off as part of a “Staff Appreciation Week” during the week between Christmas and New Year’s. The city would close its operations at the Governmental Center for the week, and staff would be awarded three additional days – or 24 hours – of paid time off. Employees unable to use the time during that week because of performing essential duties or for other reasons would be able to use the time off through June. The benefit would also be extended to TCLP and Downtown Development Authority (DDA) staff, provided those entities approve the proposal, and would be a one-time benefit to thank “all full-time employees after the tough one-to-two years we have experienced,” according to City HR Director Kristine Bosley. The estimated cost of the benefit is $160,000 and would come out of various funds associated with the city's payroll budget, according to Bosley.