Guidance for meeting bacteria TMDL MS4 permit requirements

Bacteria Total Maximum Daily Loads (TMDLs)

Escherichia (E). coli is an indicator bacteria, meaning that it indicates the potential presence of disease causing pathogens that can be harmful to human health. Currently there are X TMDLs that include MS4 WLAs for bacteria. Click here to link to MPCA's impaired waters website. A map illustrating U.S. EPA-approved listings for E. coli and fecal coliform is shown on the right (insert map).

The MS4 permit requires permittees that have an applicable wasteload allocation (WLA) for bacteria to:

1. Maintain a written or mapped inventory of potential areas and sources of bacteria (e.g., dense populations of waterfowl or other birds, dog parks) (Permit requirement 18.14).
2. Maintain a written plan to prioritize reduction activities to address the areas (Permit requirement 18.15).

Maintain a written or mapped inventory of potential areas and sources of bacteria (Permit requirement 18.14)

The written or mapped inventory should identify potential areas and sources of bacteria. Some common sources that will likely be identified include sanitary sewer overflow locations, areas that attract nuisance birds and/or wildlife (parks, golf courses, etc.), dog parks, known septic systems, etc. (see Table 1 for additional potential sources).

Link to this table Potential sources of bacteria and actions to address
Link to this table

General Category	Source	Action
Municipal Sanitary Infrastructure	Combined Sewer Overflows1	Replace infrastructure, if possible
	Sanitary Sewer Bypasses/Overflows	Line sanitary sewer pipes
	Inflow and Infiltration	Minimize and eliminate through repairing damaged sewers
	Illicit discharges from unsewered communities	Detect and eliminate illicit discharges
Human Sanitary Sources	Leaky/failing septic systems	Update and enforce subsurface sewage treatment system (SSTS) ordinances
		Educate homeowners on septic system maintenance and opportunities for replacement
		Implement higher standards for setbacks for installing septic systems near receiving water bodies
	Porta-potties	Ensure construction site temporary toilets have appropriate pollution prevention BMPs
Domestic pets	Dogs, cats, dog parks, walking trails, residential yard and sidewalk runoff (spring runoff after winter accumulation)	Establish pet waste disposal stations along trails, in dog parks, etc.
		Pass and enforce pet waste ordinances and educate pet owners about them
		Add infiltration BMPs downstream of parks/residential areas and upstream of stormwater pipes (i.e., somewhere between the park/residential area and the stormwater outfall so as to intercept and infiltrate some or all of the flow from these areas)
		Reduce transport from parks, residential, and other areas by the use of buffer zones and other disconnection of flow pathways (e.g. impervious surface, disconnection, downspout disconnection)
Urban wildlife	Rodents (raccoons, squirrels, etc.), deer, etc., birds (geese, ducks, swallows, etc.), areas where wildlife congregate such as fields, parks, and golf courses	Wildlife feeding bans and control of nuisance populations, including ducks and geese and other wildlife
		Remove community facilities such as vending machines for feeding ducks and geese
		Add buffers in riparian zones near waterbodies to deter waterfowl congregation
		Consider wildlife barriers if wildlife (e.g. raccoons) are found to be living in storm sewers
		When possible, use infiltration BMPs instead of detention ponds in residential developments and other areas where wildlife may congregate
Other Urban Sources (non-stormwater)	Excessive irrigation/overspray	Assess the extent to which irrigation over-spray occurs at city-owned facilities and eliminate overspray as appropriate
		Education on water conservation
MS4 Infrastructure	Illicit sanitary connections to MS4	Detect and eliminate illicit discharges
	Leaky sewer pipes	Line sewer pipes
	Biofilms/regrowth	Reduce dry weather flows, which provide conditions that promote bacteria growth. Dry weather flows could be from night time irrigation of lawns/parks or leaky stormsewer pipes.
	Decaying plant matter, litter, and sediment in the storm drain system	Enhance street sweeping program.
		Prevent the discharge of grit chamber clean out effluent
		Remove leaf litter and soil in street and gutters: implement an Adopt-a-storm drain program
Other Natural Sources	Stream Bank Erosion	Streambank restoration

¹Note only a few combined sewers remain in Minneapolis
*This table was created using information from the Upper Mississippi River Bacteria TMDL Study (2014) and Protection Plan and the Upper Mississippi River Bacteria TMDL Implementation Plan (2016), Pathogens in Urban Stormwater Systems (2014), and the Minnehaha Creek Bacterial Source Identification Study (2017).