Boardman River Wall Stabilization Project
Department of Municipal Utilities
Project Update: 1/18/2023
Sheet placement for the Boardman River Wall Stabilization project has been completed and traffic patterns have returned to normal will return to normal. Additional sheet work and railing work will continue into February, weather pending.
The first project, the Boardman River Wall Stabilization and Sewer Relocation Project, of the City’s The Clean Water State Revolving Fund (CWSRF) Five Year Project Plan will kick off construction on December 13, 2022.
Along the frontage of the Lower Boardman River in the 100 and 200 block of Front Street a concrete retaining wall built in the 1930’s supports a sanitary sewer main and surface parking and sidewalks. The wall is a cantilevered retaining wall, itself supported by a series of timber piles. In recent years it has become apparent that the river is scouring out the soil underneath the wall footing, which was confirmed by an underwater video inspection of the wall. During the spring of 2020, depressions formed in the landscape areas, paving showed signs of failure, and signposts began falling over, all of which indicated that soil stability issues exist adjacent to the wall.
In June 2021, a site inspection was conducted of the retaining wall and the surrounding areas along the south edge of the Boardman River between Park and Union Streets (the 100 and 200 block alleys). The field inspection noted significant subsidence and settling along the back of the retaining wall (evidenced by sloped parking areas, cracked sidewalks, and reoccurring soil and pavement depressions). Based on this field inspection, as well as a review of the original wall design and the results of a 2018 dive inspection, it was determined that the subsidence and settling were likely due to a loss of soil material (i.e. backfill) within about a 10-foot zone from the wall through a gap below the footing and through the wall at locations of penetrations. The engineer noted that soil material loss was likely exacerbated by the high water level of the Great Lakes, which causes soil saturation and loss of consolidation of the backfill soils
It was also determined that the existing 24-inch sanitary sewer main is at risk and needs to be protected (or relocated) since it sits directly on top of the river wall foundation, which is supported by wooden piles. If the wall footing were to tip or move due to the lack of supporting soil beneath, it would likely cause a catastrophic failure of the sewer main allowing raw sewage to discharge directly into the Boardman River.
The Boardman River Wall Stabilization Study recommended that the existing 24-inch sanitary sewer running along the river wall between Union and Cass Streets be relocated to the south in the alley away from the wall. This would reduce the risk of sewer failure if the undermined wall and footing were to tip or move, which could cause a catastrophic sewer failure allowing a large volume of raw sewage into the Boardman River as this sewer conveys nearly half of the wastewater flow to the treatment plant.
Over the past 25 years, conditions in the alley have deteriorated. Recently, site conditions between the wall and sidewalk have deteriorated at an alarming rate with increased settlement and sidewalk instability issues. Due to the critical nature of the 24- inch trunk line sewer, it was recommended that the project is divided into two phases.
Design work was approved by the City Commission in October 2021 and awarded to the engineering consulting firm Hubbell Roth and Clark (HRC) for $16,785. The City will also focus on the critical segment of the project in the 200 block between Cass and Park Streets since the sewer is planned to remain along the wall through that area as there is very little room in the alley between the buildings and the river wall.
Project Begins December 13, 2022
The Boardman River Wall Stabilization & Sewer Relocation Project will begin with work in the 200 block north alley on E. Front Street. The project will include wall stabilization along the Boardman River to protect a trunk line 24-inch sanitary sewer main that serves the entire west side of Traverse City and portions of Garfield and Elmwood Townships. The initial work in the 200 block alley will begin at Cass Street and continue east, toward Park Street. The project will be conducted in sections daily between 7 am and 5 pm, and is anticipated to be complete by early February 2023, weather pending. Traffic will be maintained in the alley, but may be disrupted when workers are present. Beginning in March 2023, work will be conducted on the river wall and railing with an anticipation of completion in May 2023.
In August 2022, the City approved up to $8 million in bonds for year 1 in drinking (DWSRF) and clean (CWRSF) water project plans. Phase 1 and Phase 2 of the Boardman River Stabilization Project will total nearly $2,500,000 and will be funded through bonds through a State of Michigan program with low interest loan rates.
CWSRF & DWSRF
The City submitted a Clean Water State Revolving Fund (CWSRF) Project Plan in order to apply for low interest loan funding over the next 5 years. The Project Plan incorporated projects to address recommendations contained in the recent Stormwater, Asset Management, and Wastewater System (SAW) Programs, and other engineering evaluations that were completed. These projects are important to ensure the sanitary collection system and Wastewater Treatment Plant operates properly. Projects to reduce Inflow and Infiltration (I&I) and Sanitary Sewer Overflows (SSOs) are also considered with the project plan. The total estimated cost of potential improvements is $28,734,260 over a 5 year period.