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Skip Navigation LinksDNREC : Division of Watershed Stewardship : Watershed Assessment & Management : Watershed Assessment 305b and 303d Reports

Watershed Assessment Section: 305(b) and 303(d) Reports

Section 305(b) of the Federal Clean Water Act requires that states and other entities prepare and submit a Watershed Assessment Report to EPA on April 1 of every even numbered year. EPA is required to summarize these reports and prepare a report of their own to Congress. The 305(b) reports and monitoring data are used to compile a list of impaired waters, commonly referred to as the 303(d) list. 

Simply put, impaired waters are polluted waters. More technically, they are waters that do not meet water quality standards for their designated uses, such as recreation, fishing, or drinking.  Impaired waters could be suffering from excess nutrients, low dissolved oxygen, toxins, bacteria, heat, or any combination of these problems. The most common causes are pathogens, such as bacteria, and nutrients, especially nitrogen and phosphorus. Most impairments come from nonpoint sources, which are harder to control. 

When waters are identified as impaired on 303(d) lists, a Total Maximum Daily Load (TMDL) must be developed. Tributary Action Teams and other groups have recommended pollution control strategies and other types of watershed plans to improve the quality of our waterways.

All of the 305(b) Reports and 303(d) lists that Delaware has submitted to EPA are available below. The Watershed Assessment Section actively solicits information from a wide variety of sources and evaluates the information for inclusion in 305(b) reports. If you have or know of information that should be used in the preparation of the report or the 303(d) list, please contact the section.


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