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<br />Minnesota <br />Pollution <br />Control <br />Agency <br />13 <br />Background <br />Daily Loads <br />on Total Maximum <br />General Public # gp5.13 August 2008 <br />water body is "impaired" or <br />polluted if it fails to meet one or <br />more water quality standards. <br />Federal standards exist for basic <br />pollutants such as sediment, bacteria, <br />nutrients and mercury. The Clean Water <br />Act (CWA) requires the Minnesota <br />Pollution Control Agency (MPCA) to <br />identify and restore impaired waters. <br />Minnesota's Impaired Waters list <br />(updated every two years) identifies <br />assessed waters that do not meet water <br />quality standards. The 2008 Impaired <br />Waters list contains 1,475 total <br />impairments on 336 rivers and 510 lakes. <br />Water quality assessments are complete <br />on a small percentage of Minnesota's <br />river miles and lakes. <br />What is a TMDL? <br />For each impairment on the list, the <br />CWA requires completion of a Total <br />Maximum Daily Load (TMDL). <br />The term "TMDL" describes both a <br />process and a number. The process <br />typically involves two to four years of <br />technical study and intensive stakeholder <br />and public input. The number is a <br />calculation of the maximum amount of a <br />pollutant the water body can receive and <br />still meet water quality standards. <br />A TMDL results in a pollution reduction <br />plan. The pollution reduction plan <br />identifies all the sources of the pollutant in <br />the watershed and allocates needed <br />reductions among them. The plan also <br />includes a margin of safety to account for <br />uncertainties in the calculations and <br />seasonal variability in water quality. In <br />addition, the plan may factor in a reserve <br />capacity to allow potential future <br />expansions in discharge. <br />Assess the state's waters <br />List those that do not meet standards <br />Identify sources and reductions needed <br />(TMDL study) <br />Implement restoration activities <br />(Implementation Plan) <br />Evaluate water quality <br />Related information Impaired waters <br />Background paper available on-line at: <br />http://www,pca. state. m n. us/newscenter/background. <br />html. <br />Minnesota's Impaired Waters list available at: <br />>~://www.pca.state.mn.us/water/tmdl/tmdl- <br />303dlist.html. <br />View the list of TMDL project underway in <br />Minnesota at: <br />http://www.pca. state.m n. us/water/tmdl/index. html# <br />rp oiects. <br />Minnesota Pollution Control Agency 520 Lafayette Rd. N., St. Paul, MN 55155-4194 www.pca.state.mn.us <br />651-296-6300 800-657-3864 TTY 651-282-5332 or 800-657-3864 Available in alternative formats <br />The TMDL Process <br />