Section 212.75. Developing TMDLs for Great Lakes systems tributaries and connecting channels.

  This section describes conditions for deriving TMDLs for tributaries and connecting channels of the Great Lakes system as defined in s. NR 102.12 (1) that exhibit appreciable flows relative to their volumes. This section applies to TMDLs for all pollutants excluding the following: alkalinity, ammonia, bacteria, biochemical oxygen demand, chlorine, color, dissolved oxygen, dissolved solids, pH, phosphorus, salinity, temperature, total and suspended solids, turbidity, and whole effluent toxicity. In addition to the requirements specified in s. NR 212.73 , TMDLs in this section shall also meet all of the following:

(1)  TMDLs shall reflect, when appropriate and when sufficient data are available, contributions to the water column from sediments inside and outside of any applicable mixing zones. TMDLs shall be sufficiently stringent so as to prevent accumulation of the pollutant of concern in sediments to levels injurious to designated or existing uses, human health, wildlife, and aquatic life.

(2)  TMDLs shall reflect, when appropriate and when sufficient data are available, discharges resulting from wet weather events.

(3)  TMDLs shall reflect, when appropriate and when sufficient data are available, background concentrations of pollutants stemming from atmospheric deposition, sediment release or resuspension, or as a result of chemical reactions.

(4)  Design flows shall be used unless data exist to demonstrate that an alternative stream design flow is appropriate for stream-specific and pollutant-specific conditions. For purposes of calculating a TMDL, the stream design flows shall be all of the following:

(a) The 7-day, 10-year stream design flow (7Q10), or the 4-day, 3-year biologically-based stream design flow for chronic aquatic life criteria or values.

(b) The 1-day, 10-year stream design flow (1Q10), for acute aquatic life criteria or values.

(c) The harmonic mean flow for human health criteria or values.

(d) The 90-day, 10-year flow (90Q10) for wildlife criteria.

(e) TMDLs, calculated using dynamic modeling are not required to incorporate the stream design flows specified in pars. (a) to (d) of this procedure.

(5)  The loading capacity is initially calculated at the farthest downstream location for the impaired reach by multiplying the applicable criterion or target value by the flow condition described in sub. (4) . The loading capacity is then compared to the loadings at sites within the basin to assure that applicable numeric criteria or values for a given pollutant are not exceeded at all applicable sites. The lowest load is then selected as the loading capacity to be consistent with the attainment of each applicable numeric criterion or value for a given pollutant.

History: CR 15-085 : cr. Register August 2016 No. 728 , eff. 9-1-16.