Differences Between Sanitary & Storm Sewers
Comparison at a Glance
The City of Midland has 2 separate but interrelated collection systems:
- A sanitary sewer system for wastewater
- A storm water collection system for rainwater runoff and snow and ice-melt
The aim of these two systems is to maintain a safe, sanitary and pleasant environment for all citizens within the City of Midland and the waters of the State of Michigan.
Sanitary Sewer System
The city's sanitary sewer collection system consists of pump stations and an intricate maze of pipes constructed under city streets. The system collects wastewater (such as from the bathroom, laundry facilities or kitchen sink) and transports it to the City of Midland Wastewater Treatment Plant.
Some of the pipes used in this process convey sewage by way of gravity, while others pump wastewater under pressure; these pipes are called "force mains." Midland's sanitary sewer system also collects storm water from the footing drains of many homes and structures built prior to 1988.
Once at the Wastewater Treatment Plant, wastewater is treated in a complex system according to stringent State of Michigan regulations and is then discharged into the Tittabawassee River.
Pump Stations & Gravity Sanitary Sewer Pipes
The Wastewater Treatment Plant is responsible for 41 pump stations ranging in size from 20 to 5,500 gallons per minute capacity. Approximately 987,474 feet of gravity sanitary sewer pipes run throughout the city. These pipes range in size from 6 to 48 inches in diameter.
The City's sanitary sewer system is cleaned on a two-year rotation with some areas cleaned more often. Wastewater staff also video inspect sewers to evaluate their condition. In addition, smoke is blown through pipes in various sections of the city as needed to help locate any sewer line breaks or defects and identify locations where storm water unnecessarily enters the sanitary sewer system.
Storm Water Collection System
The City's storm water collection system is separate from the sanitary sewer system and is constructed primarily under city streets, with some areas in the city utilizing ditches and streams for water runoff. There are approximately 170 miles of storm sewer pipe in the City's storm water collection system.
The City's storm water system collects precipitation runoff from rooftops, streets, yards and parking lots and discharges it to local rivers, streams and drains. Footing drains that are constructed along the exterior of a structure's foundation intercept groundwater and drain it away from a structure's basement to prevent moisture from seeping through the walls. These footing drains are connected to the City's storm sewer system. Water that is collected through the City's system is conveyed to the Tittabawassee River.
Most homes and structures built prior to 1988 discharge storm water directly into the sanitary sewer collection system. Homes and structures built in 1988 or later discharge footing drain water into the storm water collection system.
The City's storm water collection system is made up of three major drainage basins identified by the location of their respective outfall. These basins are the Sturgeon Creek Basin, the Snake Creek Basin and the George Street Basin.
To ensure the effective, efficient flow of storm water, Wastewater Department staff clean the storm water system on a four-year rotation. Catch basins are also cleaned on a 4 year rotation schedule. Video equipment is used to aid in locating system defects and tree root intrusion, and, as necessary, Wastewater staff remove roots from the City's portion of the storm water system.
Midland homeowners and property owners are responsible for removal of tree roots or other vegetation that can cause blockages in sanitary sewer piping from a home or structure to the City's storm water collection system.