Total Maximum Daily Load for Nitrate for Des Moines River, Iowa, 2009

(2009) Total Maximum Daily Load for Nitrate for Des Moines River, Iowa, 2009. Natural Resources, Department of

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Abstract

The Federal Clean Water Act requires the Iowa Department of Natural Resources (IDNR) to develop a Water Quality Improvement Plan, also known as a Total Maximum Daily Load (TMDL), for waters that have been identified on the state’s 303(d) list as impaired by a pollutant. The 2004 305(b) assessment reported that the designated drinking water use of the Des Moines River from Center Street dam in Des Moines to Interstate 80 bridge (segment 04-UDM-0010_2) was impaired due to nitrate-nitrogen (nitrate) concentrations. For the impaired segment, the Class C (drinking water) uses were assessed as “not supporting” due to the level of nitrate that exceeds state water quality standards and USEPA maximum contaminant level (MCL). The applicable water quality standard for nitrate is 10 milligrams per liter (mg/l). A Water Quality Improvement Plan has been developed to calculate the maximum allowable nitrate load for the impaired segments of the Des Moines River that will ensure compliance with water quality standards.