During rain or heavy snow melt events (known as "wet weather") the 3RPORT will collect and transport the combined sanitary sewage and stormwater runoff that would otherwise be discharged to the St. Marys and Maumee Rivers. During dry weather, sanitary sewage from the combination sewer area will continue to be carried through existing sewer lines treatment plant to be treated. However when it rains, the tunnel will collect the combined sewage that cannot be carried to the treatment plant by the existing sewer system. The combined sewage will travel through the tunnel to the plant where it will be stored temporarily and treated after the wet weather event when the plant has sufficient capacity.
See a Tunnel Works diagram