Chippewa River, Minnesota Technical Support for Un-ionized Ammonia TMDL

The lower segment of the Chippewa River (segment 07020005-501, first listed in 1998 as segment 07020005-001 see note below), running from the confluence with the Minnesota River upstream 12.6 miles to the Watson Sag Diversion, has been listed by the State of Minnesota as not supporting designated uses due to elevated concentrations of un-ionized ammonia. Un-ionized ammonia is toxic to fish and other aquatic life, and Minnesota has established a water quality criterion of 0.04 mg/L or less of un-ionized ammonia instream to protect aquatic life. Because the waterbody has been formally listed as impaired on Minnesota's Clean Water Act Section 303(d) list submitted to EPA, this segment of the Chippewa River has been scheduled for development of a Total Maximum Daily Load (TMDL), specifying how much ammonia can be loaded to the river without contravening water quality standards, and how that ammonia load should be allocated among point and non-point sources. This document, developed under the auspices of U.S. EPA Region 5, is intended to provide technical support to Minnesota for the estimation of the TMDL