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Surface Water Quality Standards
The Federal Water Pollution Control Act (aka Clean Water Act of 1972 and subsequent amendments) requires states, territories, and authorized Indian tribes to establish surface water quality standards in order to meet the goals of the Act to “restore and maintain the biological, physical, and chemical integrity of the Nation’s waters” and “…provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water…”. Water quality standards are a cornerstone to protecting public health and the environment.
Water Quality Standards include three key elements. These are:
- Designated uses
- Criteria to protect the designated uses
- Antidegradation requirements to maintain the quality of the water
Designated Uses (40 CFR 131.10)
Designated uses “are those uses specified in water quality standards for each water body or segment whether or not they are being attained. Categories of uses include the following:
- Drinking water source – the source of water may be used for drinking water assuming appropriate treatment
- Consumption of aquatic organisms caught in those waters
- Recreation in and on the water – Includes swimming, boating, and fishing
- Aquatic life protection – protection and propagation of fish, shellfish, and wildlife
- Agricultural, industrial, navigational and other purposes – This can include water for agricultural irrigation, livestock watering, and industrial uses
Designated uses may be assigned based on past (i.e. existing) uses of a water body. However, a use attainability analysis (UAA) must be performed to determine if the water is attaining that use based on the current water quality. A use attainability analysis is a structured scientific assessment of the factors affecting the attainment of the use which may include physical, chemical, biological, and economic factors. The following diagram describes a use attainability analysis.
Diagram taken from EPA website.
UAA regulatory requirements can be found at 40 CFR 131.10(g) and …(j).
Criteria (40 CFR 131.11)
Criteria provide a description of the condition of a waterbody to achieve a given use. Criteria may be a numerical value for a pollutant in the water or a narrative description of the condition to meet a designated use.
The U.S. Environmental Protection Agency recommends numeric water quality criteria to assist states in developing standards. Separate criteria are established to protect human health and aquatic & wildlife uses.
Human health-based criteria protect individuals who consume the water (mostly after treatment), consume aquatic organisms taken from the water, or have full-body or partial body contact with water (e.g. swimming, wading), where there is potential to consume small quantities of water.
Aquatic & wildlife (A&W) criteria are established to protect aquatic organisms (i.e. those that spend all or a portion of their lives in the water) and wildlife that drink and bath in the water. These criteria address both acute (short-term) and chronic (long-term) exposures to pollutants.
Federal acute criteria are called Criterion Maximum Concentration (CMC), whose purpose is to protect aquatic life from the harmful effects of short-term [relatively high concentration] exposure to pollutants. The duration of a CMC is typically a one-hour average.
Federal chronic criteria are called Criterion Continuous Concentration (CCC) and are established to protect aquatic life from the harmful effects of long-term [relatively low concentration] exposure to pollutants. The duration of a CCC is typically a four-day average.
For a given pollutant, chronic criteria are generally much lower than acute criteria and, therefore, become the key value for enforcement of standards. More on this in a future article titled “National Pollutant Discharge Elimination System 101”.
EPA has published tables for both human-health and aquatic life criteria. These can be found at https://www.epa.gov/wqc.
The criteria include inorganic, volatile organic, and semi-volatile organic chemicals, including pesticides. Various physical and chemical factors influence site-specific values of criteria. Examples include:
- Criteria (i.e. concentration) for certain metals (i.e. cadmium, chromium III, copper, lead, nickel, and zinc) are dependent on the hardness of the water
- Criteria for pentachlorophenol are dependent on the pH of the water
- Criteria for ammonia are dependent on the temperature and pH of the water and whether, or not, Unionid Mussels (i.e. freshwater mussels) are present or absent (Unionid Mussels are particularly sensitive to ammonia).
Water quality standards tables account for these dependencies and/or provide conversion factors and equations to calculate the standard for the water body in question.
States also establish narrative criteria. These provide a description of the condition of a water to attain a designated use. Narrative criteria include statements such as the waters being “free from”:
- substances toxic to humans and aquatic organisms
- oil, scum, color
- or substances that can create odor in the water or off-tasting of aquatic organisms
EPA publishes guidance to states and tribes on how to develop Nutrient Water Quality Criteria, Biological Water Quality Criteria, and others.
Individuals subject to federal criteria and ultimately to state standards are encouraged to become familiar with these regulations.
Antidegradation (40 CFR 131.12)
Antidegradation requirements are another important element for water quality standards. These establish a base quality for water bodies that shall not be exceeded. Water bodies are organized into categories called Tiers based on the existing quality of the water compared to the associated final water quality standards.
- Tier 1 – Protect existing uses by maintaining base water quality to support those uses
- Tier 2 – Protect “high quality” waters, where the quality of a water is better than the criteria or standards established to support the uses
- Tier 3 – Protect Outstanding National Resource Waters (ONRWs), where the waters are of significant recreational, environmental, or ecological importance. States and tribes may give these waters different names.
States must adopt federal water quality criteria or establish state standards using site-specific conditions or other defensible scientific methods. States and tribes must obtain approval from the EPA before they can finalize their standards. See diagram below.
Diagram taken from the EPA website
More information can be found at https://www.epa.gov/wqs-tech/what-are-water-quality-standards.
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About The Author
At NJBSoft, we’re proud to collaborate with experts like Robert Hollander, P.E., whose extensive experience in water quality and regulatory compliance allows us to design SAMS in order to meet industry needs. Bob’s leadership and deep industry knowledge supports utilities in staying organized, compliant, and focused on protecting public health every day.
Robert Hollander
- 45 years of experience in water quality, regulatory compliance, and utility management
- President of Hollander Consulting Services
- Held senior roles at the City of Peoria, City of Phoenix, and the Arizona Department of Environmental Quality
- Served as President of the AZ Water Association and the Western Coalition of Arid States
- Licensed Professional Engineer in Arizona with multiple Grade 3 operator certifications
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