Surface Water Quality Standards

The National Clean Water Act of 1972 set in place a program that is intended to restore the chemical, physical, and biological integrity of the nation’s waters. To reach these goals, a series of steps were mandated by Congress for the Environmental Protection Agency and the individual States to take. The first step was for the States to set their own standards for their waters.

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Watershed Assessment and Management

Surface Water Quality Standards
(7 DE Admin. Code 7401)

Delaware’s Standards

As established under the Clean Water Act (CWA), water quality standards are the regulations which list designated uses, water quality criteria, and an antidegradation policy. The standards have been established to protect public health and welfare and enhance water quality in the State. While the standards are Delaware regulations, they must be approved by the EPA. If the EPA cannot approve the standards, then EPA is mandated to take over the process and set standards for state waters in a process known as promulgation. Failure by the state or EPA to implement the requirements of the CWA subjects the EPA to citizen lawsuits to enforce the provisions of the Act.

Designated uses are the water uses specified in water quality standards for each water body. The CWA requires that the uses are to be achieved and protected, even if they are not currently being attained. A water body can have more than one designated use.

Designated Uses in Delaware

Public Water Supply

Industrial Water Supply

Primary Contact Recreation (Swimming)

Secondary Contact Recreation (Wading)

Fish Aquatic Life and Wildlife

Cold Water Fish

Agricultural Water Supply

ERES Waters (Waters of Exceptional Recreational of Ecological Significance)

Harvestable Shellfish Waters

Fish Consumption

Water quality criteria are designed to ensure the achievement of the designated uses assigned to each water body or segment. The criteria are expressed as concentrations, parameter levels or as narrative statements. It is assumed that if criteria are met, designated uses will be protected.

To receive EPA approval, each state’s water quality standards must include an antidegradation statement and policy. The policy is intended to maintain existing uses and the level of water quality necessary to protect those uses. Under certain circumstances high quality waters may have their quality lowered, but their uses must still be protected and the public must be informed and involved in the decision to allow the quality to be lowered.

The final CWA requirement for state water quality standards is that a public review of them occurs every three years. This process is referred to as the Triennial Review and Delaware has promulgated new Standards based on that review. The most recent Triennial Review was approved on January 1, 2023.

DNREC monitors water quality in order to determine compliance with its standards. An annual monitoring plan is developed and implemented.

States are also required to document their progress every two years in a Combined Watershed Assessment Report (305(b) Report) and List of Impaired Waters (303(d) List). This document is submitted to the EPA every two years. EPA then rolls up all the States reports into a national report to Congress.

For waters that fail to meet their standards, Total Maximum Daily Loads (TMDLs) must be developed and watershed plans or strategies are developed to guide implementation actions.