Monday, October 12, 2009

Minnesota Statewide Mercury TMDL - Proposed MPCA Amendement

The Minnesota Pollution Control Agency (MPCA) has recently proposed adding a total of 126 lakes, streams and rivers to its list of mercury impaired water bodies. Excess mercury in fish from these additional water bodies will be addressed under the existing Statewide Mercury TMDL, or under a water body specific TMDL, depending on fish tissue concentrations.

The MPCA Mercury TMDL relies on a reduction goal for mercury atmospheric deposition. The TMDL contains the list of lakes and river segments covered by the TMDL. The Statewide Mercury TMDL also contains the list of NPDES permittees covered by the TMDL.

The 2008 Mercury TMDL listed 998 water bodies. Subsequently, three water bodies were split, resulting in a total of 1001 water bodies. An additional 95 waterbodies are being added in the 2010 cycle, resulting in a grand total of 1096 water bodies in the 2010 revision the EPA-approved Mercury TMDL.

The water bodies listed in the Statewide Mercury TMDL have fish tissue concentrations greater than 0.2 mg/kg [the Minnesota State water quality standard] and equal to or less than 0.572 mg/kg. Fish tissue concentrations that exceed 0.572 mg/kg are not eligible to be included in the Statewide Mercury TMDL. Those mercury impairments are subject to a future TMDL studies. In 2010, MPCA is proposing to add 28 water bodies to the list of mercury impaired waters not eligible to be addressed under the Statewide Mercury TMDL, bringing the total to 326.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address water quality standards, wastewater permitting and assessing potential impacts of chemicals in the aquatic environment.

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