City Talks Solutions For Fixing Sewers
By Beth Milligan | July 28, 2020
Following three major recent rain events that overwhelmed Traverse City pipes and caused raw sewage to flow into the Boardman River, city commissioners and staff Monday discussed both short and long-term fixes to address the sewer system failures. While immediate improvements are planned to help prevent spills at a site near Front and Union where all three recent releases occurred, modernizing the city’s overall aging infrastructure could take years and cost millions of dollars. It's an undertaking exacerbated by climate change, high waters, illegal basement pump systems, and more than seven miles of city pipes now buried lower than lake levels – increasing their risk of submersion.
City Director of Municipal Utilities Art Krueger told commissioners that the three recent storms on May 28, June 10, and July 18 responsible for sewage overflows included one 200-year-storm and two 50-year storms, dropping 2.5 to 3 inches of rainfall on the city in 30 to 60-minute windows. Because water levels are already at record highs and the earth is saturated, the rain had nowhere to go, said Krueger. That caused the city’s downtown pipes to become choked with enormous amounts of water too quickly for the system to keep up, forcing sewage back up through a manhole and into the nearby Boardman River. A failure at the city's Front Street lift station (pictured) further exacerbated the situation during the May 28 storm. An estimated 54,000 gallons of sewage were released into the Boardman on May 28, 2,500 gallons on June 10, and 1,200 gallons on July 18. Prior to 2020, the city had only experienced two large-scale overflows caused by storms, both of which dumped more than four inches of rain on the city: one in September 2000 and one in July 1999.
This year, “many of the city’s storm sewers are inundated from the impact of record high water levels and cannot drain at their normal capacity,” Krueger outlined to commissioners. “Therefore, during these large storm events, many streets are flooded for extended periods of time, allowing more infiltration and inflow into sewers.”
Inflow and infiltration are the two main culprits plaguing the city’s sewer system, Krueger said. 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. According to city data, more than 7.1 miles of city sewer pipes are below Lake Michigan’s record-high water levels this year – meaning likely increased groundwater pressure on all those lines.
Krueger said the city is taking immediate steps to address the vulnerable overflow spot near Front and Union. In addition to just over $132,000 approved by commissioners in June to pay for new auxiliary pumping equipment and suction and discharge piping for the Front Street lift station – which directly connects to the overflow site – staff today (Tuesday) will start building a containment area around the system’s low point near the Traverse City Record-Eagle building. That containment area, which Krueger compared to a type of bathtub, can hold 3,500-3,700 gallons to keep potential overflow contained during rain events. City vacuum trucks – which can hold 2,000-2,500 gallons each – are also being readied and can be deployed as additional backup if a hard rain causes the containment area to near its maximum capacity. City staff are also working with a consulting firm to evaluate the downtown system and are installing new flow meters to better collect system data.
Those fixes are in addition to other projects underway since June, including reconstructing failing lines under Randolph Street as part of a street reconstruction project, cleaning sanitary trunkline, completing inspections to look for illicit sump pump connections (it’s illegal for residents and businesses to pump out their flooded basements into the city’s system), and sealing manhole rims to prevent inflow. Staff also raised the stops logs on the Front Street lift station by 22 inches to prevent water from the high Boardman River from inundating the station – a scenario Krueger said could have resulted in significantly more catastrophic spills. In the coming months, the city plans to step up enforcement efforts against illicit sump pumps, conduct another 400 inspections to look for additional sump pump connections, and calibrate the city’s west sewer trunkline based on flow data from the new meters.
Longer-term solutions over the coming years could involve significantly more expensive projects, like increasing the overall size and capacity of downtown sewer pipes, installing a new lift station near Sixth and Locust, installing new liners in sewer pipes to stop infiltration, and installing an underground equalization tank in the Warehouse District to provide peak storage volume during high flows. The amount of repairs needed will likely require raising the city’s sewer rates, in addition to possible funding options like bonding to bundle major projects together upfront. Staff and commissioners agreed to work together in the coming months to create a detailed list of potential projects with cost estimates to begin prioritizing what improvements will be made when – and how they’ll be funded. City Manager Marty Colburn also said he plans to bring surrounding townships into the discussions to take a more collaborative regional approach to the issue, noting that Traverse City essentially sits at the bottom of a basin surrounded by elevated townships – with water flowing down into the city core from all directions.
Mayor Jim Carruthers agreed, adding that the city and other partners – including other coastal municipalities across Michigan similarly affected by high waters who are seeking state and federal funding to help address the issue – would likely “be talking about this (issue) for quite some time.” Addressing public comments expressing frustration with the city's management of its sewer system and the recent spillage events into the Boardman, Carruthers said: “I think the public needs to understand none of us commissioners or staff want to be polluting our fresh water. We don’t want this to be happening, and we’re doing our darndest to support what we can do. It’s not because of a lack of understanding or a lack of due diligence…we’re challenged by Mother Nature, and we’re challenged by the change in our climate. So we’re working as best we can, and I think we can do better. I think we’re going to prove hopefully in the next few months that we are going to do better here.”Comment