Under
Section 303(d) of the Clean Water Act, states are required from "time to time" to submit a list of waters for which effluent limits will not be sufficient to meet all state water quality standards. EPA has defined "time to time" to mean April 1 of even numbered years. The failure to meet water quality standards might be due to an individual pollutant, multiple pollutants, "pollution," or an unknown cause of impairment. The 303(d) listing process includes waters impaired by point sources and non-point sources of pollutants. States must also establish a priority ranking for the listed waters, taking into account the severity of pollution and uses. The EPA regulations that govern 303(d) listing can be found in the Code of Federal Regulations
40 CFR 130.7.
The Iowa Department of Natural Resources TMDL and Water Quality Assessment Section compiles this impaired water list, or 303(d) listing. The 303(d) listing is composed of those lakes, wetlands, streams, rivers, and portions of rivers that do not meet all state water quality standards. These are considered "impaired waterbodies" and states are required to calculate
total maximum daily loads (TMDLs) for pollutants causing impairments.
Additional Resources
Current 303(d) Listing
2010 Impaired Waters List
Iowa DNR submitted its final 2010 Integrated Report, including Iowa's 2010 list of impaired waters, to U.S. EPA for approval on May 27, 2011. Iowa DNR received final approval of the May 2011 submittal from U.S. EPA on June 29, 2011.
Public comments were sought on Iowa’s draft 2010 list from January 18, 2011 through April 4, 2011. Comments were submitted to IDNR by one government agency (U.S. EPA) and two individuals. Changes were made to the draft list based on the comments received. Iowa's final 2010 Section 303(d) list, as submitted to U.S. EPA on May 27, 2011 for review and approval, contained 474 waterbodies with a total of 628 impairments. This version of the list was approved by U.S. EPA on June 29, 2011.
All states submit their Integrated Report and list of impaired waters every two years as required by Sections 305(b) and 303(d) of the Clean Water Act. Iowa’s 2010 Integrated Report was prepared according to U.S. EPA guidelines that combine (integrate) requirements of Sections 305(b), 303(d), and 314 of the federal Clean Water Act. These guidelines suggest that states place all their waters (lakes, wetlands, streams, and rivers) into one of five general categories of their Integrated Report:
- Category 1: All designated uses* are met.
- Category 2: Some of the designated uses are met but insufficient
information exists to determine whether the remaining uses are met.
- Category 3: Insufficient information exists to determine whether any uses are met.
- Category 4: The waterbody is impaired but a total maximum daily load (TMDL) is not required.
- Category 5: The waterbody is impaired and a total maximum daily load (TMDL) is needed.
Category 5 is the state’s Section 303(d) list of impaired waters.
Iowa’s 2010 Section 303(d) list (Category 5 of the Integrated Report) is the fifth such list to be developed under Iowa's Credible Data Law. This law, passed by the Iowa Legislature in 2000, requires that listing decisions be based on scientifically valid chemical, physical, or biological data collected under a scientifically accepted sampling and analysis plan, including quality control and quality assurance procedures. The Department believes this “credible data” law has been implemented in conjunction with the federal listing requirements such that all readily available and existing water quality related data and information have been used for list development.
As provided for in Iowa's credible data law, the Department is to maintain a separate list of waters that require further investigative monitoring. As specified in the credible data law, this list is not part of the Section 303(d) process in Iowa and includes waterbodies where limited information suggests, but does not conclusively (credibly) demonstrate, that a water quality impairment exists. If the results of further investigative monitoring demonstrate, with data of sufficient quality and quantity, that a water quality impairment exists, the affected waterbody can be added to Iowa's Section 303(d) list. Iowa's final 2010 list of waters in need of further investigation (WINOFI) contains 254 waterbodies. Iowa’s previous (2008) list of waters in need of further investigation contained 220 waterbodies. While 209 of the waterbodies from the 2008 WINOFI remain on Iowa’s 2010 “further investigation” list, 11 waterbodies were moved to other categories of the 2008 Integrated Report as follows:
- TMDLs were prepared for two waters, and these waters were placed in Category 4a;
- Nine waterbodies were assessed as “impaired” and in need of a TMDL and were placed in Category 5 (=Section 303(d) list).
The following materials comprise Iowa's final 2010 Integrated Report that was approved by U.S. EPA on June 29, 2011. The Section 303(d) list (Category 5) is the only EPA-approvable part of the Integrated Report.