Guidance for meeting temperature TMDL MS4 permit requirements

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DRAFT Temperature TMDL WLA Guidance (MS4 General Permit Section XX)

Total Maximum Daily Loads (TMDLs)

Currently there are two approved TMDLs for Brown’s Creek and Miller Creek that include MS4 WLAs for thermal loading. Brown’s Creek is impaired for aquatic life due to a lack of cold water fish assemblage. Miller Creek is impaired for aquatic life due to a lack of cold water fish assemblage and elevated water temperature.

Requirement (Permit Section 21.10)

If the permittee has an applicable WLA for temperature that includes a reduction greater than zero percent, the permittee must maintain a written plan that identifies specific activities the permittee will implement to reduce thermal loading during the permit term (Table 1). The written plan may include, but is not limited to:

• a. implementation of infiltration BMPs such as bioinfiltration practices;
• b. disconnection and/or reduction of impervious surfaces;
• c. retrofitting existing structural stormwater BMPs; and
• d. improvement of riparian vegetation.

MS4s with applicable temperature WLAs
Link to this table

TMDL Project	MS4 with a WLA for temperature
Browns Creek TMDL	Stillwater City
Miller Creek TMDL	Duluth City
	Hermantown City
	Rice Lake City
	MnDOT Outstate
	St. Louis County
	University of Minnesota-Duluth
	Lake Superior College