Collection and treatment systems are typically designed to reduce the need for pumping wastewater and utilize gravity flow to the extent possible. Treatment facilities are normally located near rivers or streams for two reasons: low-lying areas allow the collection system to utilize gravity to deliver wastewater to the treatment facility, and it locates the facility to discharge the treated effluent to the receiving body of water.
The City’s WWTP was originally located and built in the 1950’s in its current location on the Grand River. The facility has undergone subsequent improvements projects in 1971 and 2012 to expand the facility and its treatment capabilities. Building a new WWTP in a different location would be prohibitively expensive for the City and would increase long-term operating costs of the system as wastewater would have to be pumped continuously versus using gravity flow. The more cost-effective solution is to upgrade the existing facility while implementing measures to address discharge during high river stages.
As part of the planning process for the current project, the City and its engineering team reviewed the impacts of sustained high river levels (such as during the 2019 ice jam) on the WWTP’s ability to continuously treat the wastewater and process the influent flows received throughout the collection system.
The proposed improvements include repairs in the collection system to reduce inflow and infiltration (I/I) that must ultimately be treated at the City’s WWTP. I/I can be defined as clean water that enters the collection system through cracks or seepage in the pipes from storm runoff, groundwater infiltration, or inflow from high water events. Decreasing the amount of I/I from the collection system to the WWTP frees up available hydraulic capacity for wastewater that needs to be treated. In addition, the proposed project includes hydraulic improvements and implementing provisions to enable the City’s operations staff to pump treated effluent to the river during high river stages.