Total Maximum Daily Loads for Algae, Turbidity, and Chlordane, Ottumwa Lagoon, Wapello County Iowa, 2005

(2005) Total Maximum Daily Loads for Algae, Turbidity, and Chlordane, Ottumwa Lagoon, Wapello County Iowa, 2005. Natural Resources, Department of

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Abstract

The Federal Clean Water Act requires the Iowa Department of Natural Resources (IDNR) to develop Total Maximum Daily Loads (TMDLs) for waters that have been identified on the state’s 303(d) list as impaired by pollutants. Ottumwa Lagoon has been identified as impaired by algae, turbidity and chlordane. As later explained in Section 3 of this document, the algae and turbidity impairments are symptomatic of excessive phosphorus and suspended solids loading to the lake. Phosphorus, which is related through the Trophic State Index (TSI) to chlorophyll and Secchi depth (a measurement of water clarity), is targeted to address the algae and turbidity impairments. Suspended solids, which are composed of both organic and inorganic particulate matter, are the primary transport mechanism for phosphorus. Load and wasteload allocations for suspended solids are not included in this TMDL. However, reductions in phosphorus loading should produce corresponding reductions in the suspended solids load. The purpose of the TMDLs included herein is to determine the maximum allowable phosphorus and chlordane loads that the lake can receive and still meet water quality standards.