Iowa’s Section 303(d) Impaired Waters Listings

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.

Draft 2016 Impaired Waters List - Request for public comments

Iowa DNR has prepared a draft 2016 list of impaired waters as required by Section 303(d) of the federal Clean Water Act. This list is also known as “Category 5” of Iowa’s 2016 Integrated Report. Iowa DNR is now seeking public comments on this draft list. Public comments will be solicited from April 14, 2017 through May 29, 2017. Following the end of the public comment period, the draft list will be modified based on the comments received, and the revised list will be forwarded to U.S. EPA for their review and approval or disapproval. Please mail comments to:

Iowa Department of Natural Resources Attention: Dan Kendall
Water Quality Monitoring & Assessment Section
Wallace State Office Building
502 East 9th Street
Des Moines, IA 50319

Comments can also be e-mailed to Dan Kendall at the following address:

Materials for review

Iowa’s draft 2016 list of Section 303(d) impaired waters (Category 5 of the Integrated Report). The list contains 608 waterbodies with a total of 818 impairments. There were 571 waterbodies with 754 impairments on Iowa’s 2014 final EPA-approved list. For all impaired Iowa waters (combined Category 4 and Category 5), there are 750 waterbodies with 1096 impairments. The 2014 combined Category 4 and Category 5 impaired waters contained 736 waterbodies with 1062 impairments.

This draft list, along with lists of waters in other Categories of the Integrated Report, can be found in Iowa's water quality assessment database, ADBNet. This database contains a location map and a water quality assessment for each individual impaired water. The database also provides summary information for the draft 2016 list of impaired waters and Integrated Report (charts and graphs). A map of all draft 2016 impaired waters is available, as is a fact sheet providing additional background information on Iowa's draft 2016 list of impaired waters and Integrated Report. The draft list was prepared according to Iowa DNR's updated assessment and listing methodology

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 2014 Integrated Report and list were 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 (e.g., for water contact recreation, aquatic life, and/or drinking water) 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 required. 

Category 5 is the state’s Section 303(d) list of impaired waters

Iowa’s 2014 Section 303(d) list (Category 5 of the Integrated Report) is the seventh 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 draft 2016 list of waters in need of further investigation contains 476 waterbodies with 531 potential impairments.

Additional Resources

Previous Integrated Report Documentation