Detroit's Existing Storm Water Conveyance System
Storm Water Conveyed through Combined Sewers
Most of the storm water runoff from the City of Detroit is conveyed through the City's combined sewer system which uses a single pipe to convey sanitary waste from residences, industries and businesses, along with storm water drainage. The combined sewers convey all dry weather flow, and a large portion of the wet weather flow to the wastewater treatment plant. During some wet weather events, combined sewage is discharged at permitted locations along the Detroit and Rouge Rivers when the transport and treatment capacity of the collection system and the wastewater plant is exceeded. The City is implementing a Long Term CSO Control Program to ensure that combined sewage discharges receive adequate treatment, consistent with state and federal environmental regulatory requirements.
Municipally Owned Separate Storm Sewers
In addition to the combined sewer system, Detroit has a small number of municipally-owned separate storm sewers. These sewers have a very limited drainage area consisting primarily of parkland with river frontage, and a few roadways where City streets are adjacent to the Rouge River or from bridges over river crossings. A comprehensive investigation of the City's MS4 system has identified 50 municipally-owned storm sewers including 22 outfalls to the Detroit River and its tributaries, and 28 outfalls to the Rouge River.
The city of Detroit's storm water discharges are regulated by a general storm water discharge permit issued by the State of Michigan. The discharge permit requires that the permittee develop and implement a Storm Water Management Program Plan (SWMPP) to reduce the discharge of pollutants from its municipally-owned separate storm sewers to protect water quality. The permit outlines "Six Minimum Measures" to be carried out by the permittee. The Six Minimum Measures include:
Education and outreach on storm water impacts - public education program;
Public involvement and participation;
Illicit discharge elimination program;
Post-construction Storm Water Management Program for new development and re-development projects;
Construction storm water runoff control;
Pollution prevention/good housekeeping for municipal operations.STORM WATER MANAGEMENT PROGRAM PLAN
To comply with these regulatory requirements the city of Detroit's Storm Water Management Program Plan has been developed and is being implemented through a coordinated multi-agency effort by representatives from several City Departments. Because storm water is not the sole responsibility of any one Department, the SWMPP activities involve many entities including the Water and Sewerage Department, the Recreation Department, the Planning and Development Department, the Department of Public Works, the Building and Safety Engineering Department, the Department of Environmental Affairs, the Detroit Economic Growth Corporation, the Greater Detroit Resource Recovery Authority, the General Services Department and Corporation Counsel.
The STORM WATER MANAGEMENT PROGRAM PLAN .pdf
Management and control of storm water discharge will be achieved in a manner consistent with the efforts already underway by the city of Detroit to control wet weather discharges from its combined sewer system. Once the Long Term CSO Control Plan has been completed and the Storm Water Management Program Plan has been implemented, it is anticipated that the wet weather impacts on the Detroit River and the Rouge River will have been minimized to the maximum extent possible.