Ohio's water quality standards, set forth in Chapter 3745-1 of the Ohio Administrative Code (OAC), include four major components:
beneficial use designations,
narrative "free froms",
numeric criteria, and
Brief summaries of these components are below. For a more detailed summary, see:
How can I find the use designations for my specific water body of interest?
Go to rules 3745-1-08 to 3745-1-32 of the OAC. Each of those rules covers a major drainage basin. Use the Water Body Use Designation Index on that page to find the rule number and page number of your water body of interest.
Beneficial use designations describe existing or potential uses of water bodies. They take into consideration the use and value of water for public water supplies, protection and propagation of aquatic life, recreation in and on the water, agricultural, industrial and other purposes. Ohio EPA assigns beneficial use designations to water bodies in the state. There may be more than one use designation assigned to a water body. Examples of beneficial use designations include: public water supply, primary contact recreation, and aquatic life uses (warmwater habitat, exceptional warmwater habitat, etc.)
Use designations are defined in paragraph (B) of rule 3745-1-07 of the OAC and are assigned in rules 3745-1-08 to 3745-1-32 of the OAC. Attainment of use designations is based on specific numeric and narrative criteria. To ensure protection of those beneficial uses, Ohio EPA determines and assigns maximum concentrations for over 100 chemicals.
Narrative "free froms", located in rule 3745-1-04 of the OAC, are general water quality criteria that apply to all surface waters. These criteria state that all waters shall be free from sludge, floating debris, oil and scum, color and odor producing materials, substances that are harmful to human, animal or aquatic life, and nutrients in concentrations that may cause algal blooms.
Much of Ohio EPA's present strategy regarding water quality based permitting is based upon the narrative free from, "no toxics in toxic amounts." Ohio EPA developed its strategy based on an evaluation of the potential for significant toxic impacts within the receiving waters. Very important components of this evaluation are the biological survey program and the biological criteria used to judge aquatic life use attainment.
Numeric criteria are estimations of concentrations of chemicals and degree of aquatic life toxicity allowable in a water body without adversely impacting its beneficial uses. Although numeric criteria are applied to water bodies, they primarily are used to regulate dischargers through NPDES permits.
Numeric criteria consist of chemical criteria, whole effluent toxicity levels and biological criteria.
Aquatic life and human health water quality criteria for individual chemicals are derived from laboratory studies of biological organisms' sensitivity to specific chemicals or combinations of chemicals. In these studies, organisms are exposed to known concentrations of a chemical under varying conditions. For aquatic life water quality criteria, the organisms exposed are a variety of fish, benthic macroinvertebrates and zooplankton. For human health water quality criteria, the organisms exposed are mammals, usually mice or rats.
Based on these tests, guidelines or national criteria recommendations are established by U.S. EPA. Ohio EPA uses these national criteria recommendations in combination with the latest scientific information in setting the appropriate chemical water quality criteria for Ohio's surface waters. Summary tables of aquatic life and human health water quality criteria are available on the Water Quality Criteria & Values tab.
Another class of chemical criteria are those associated with the Agricultural Water Supply use designation. These criteria protect against long term adverse effects on crops and livestock as a result of crop irrigation and livestock watering.
Chemical water quality criteria are in Chapter 3745-1 of the OAC.
Whole Effluent Toxicity Levels
Whole Effluent Toxicity (WET) measures the harmful effects of an effluent on living organisms. A bioassay or toxicity test measures the degree of response of an exposed test organism to a specific chemical or effluent. WET can only be measured using living organisms, not by an instrument. WET consists of acute and chronic toxicity tests. Acute toxicity tests measure the responses of organisms that occur soon after exposure to a test substance. Chronic tests measure the long-term response to test substances. WET measures the accumulative effects of chemicals present in an effluent that cannot be assessed using chemical-specific criteria.
Provisions addressing whole effluent toxicity are in paragraph (C) of rule 3745-1-07, rule 3745-2-09, and paragraph (B) of rule 3745-33-07 of the OAC.
Biological criteria are based on aquatic community characteristics that are measured both structurally and functionally. These criteria are used to evaluate the attainment of aquatic life uses. The data collected in these assessments are used to characterize aquatic life impairment and to help diagnose the cause of this impairment.
The principal biological evaluation tools used by Ohio EPA are the Index of Biotic integrity (IBI), the Modified Index of Well-Being (MIWB) and the Invertebrate Community Index (ICI). These three indices are based on species richness, trophic composition, diversity, presence of pollution-tolerant individuals or species, abundance of biomass, and the presence of diseased or abnormal organisms. The IBI and the MIWB apply to fish; the ICI applies to macroinvertebrates. Ohio EPA uses the results of sampling reference sites to set minimum criteria index scores for use designations in water quality standards.
Provisions addressing biological criteria are in paragraph (A)(6) of rule 3745-1-07 of the OAC.
The antidegradation provisions describe the conditions under which water quality may be lowered in surface waters. Existing beneficial uses must be maintained and protected. Further, water quality better than that needed to protect existing beneficial uses must be maintained unless lower quality is deemed necessary to allow important economic or social development (existing beneficial uses must still be protected).
Provisions addressing antidegradation are in rule 3745-1-05 and rule 3745-1-54 of the OAC. Additional information is available at Antidegradation User's Guide - 2003.
Any interested individuals can have a role in the process of developing water quality standards. Ohio EPA reviews and, as appropriate, revises water quality standards at least once every three years. When water quality standards revisions are proposed, the public is notified of these revisions. A public hearing is held to gather input and comments.
These tables summarize aquatic life and human health numerical water quality criteria and values contained in and developed pursuant to Chapter 3745-1 of the Ohio Administrative Code. The Lake Erie table was last updated on October 20, 2009. The Ohio River table was last updated on January 12, 2015.
Surface water quality criteria and procedures to calculate water quality criteria are contained in Chapter 3745-1 of the Ohio Administrative Code (OAC). With adoption of rules in 1997 pursuant to the federal Great Lakes Initiative, the water quality criteria for many chemicals differ between the Lake Erie drainage basin and the Ohio River drainage basin. The Lake Erie drainage basin comprises roughly the northern third of Ohio. The Ohio River drainage basin comprises the rest of the state.
The numerical human health and wildlife water quality criteria are in rule 3745-1-33 (Lake Erie drainage basin) and rule 3745-1-34 (Ohio River drainage basin). The numerical aquatic life water quality criteria and other types of numerical water quality criteria are in rule 3745-1-07 (applicable statewide), rule 3745-1-31 (applicable only to Lake Erie) and rule 3745-1-32 (applicable only to the Ohio River). These rules are available here:
3745-1-07 Water Use Designations and Statewide Criteria
3745-1-31 Lake Erie Standards
3745-1-32 Ohio River Standards
3745-1-33 Water Quality Criteria for the Lake Erie Drainage Basin
3745-1-34 Water Quality Criteria for the Ohio River Drainage Basin
In addition to the numerical criteria in the rules, there are procedures allowing the calculation of additional water quality criteria. These procedures are in the following rules.
3745-1-36 Methodologies for Development of Aquatic Life Criteria and Values
3745-1-38 Methodologies for Development of Human Health Criteria and Values for the Lake Erie Drainage Basin
3745-1-39 Methodology for Development of Wildlife Criteria for the Lake Erie Drainage Basin