As a precautionary response to COVID-19, Ohio EPA is currently operating with most staff working remotely. If you are working with our staff on a current project and you know the name of the employee you are working with, email them at firstname.lastname@epa.ohio.gov or call them directly. The Agency website has contact information for every district, division, and office. In order to reach us, please contact Ohio EPA’s main phone line at (614) 644-3020 or the main line for the division or office you are trying to reach.

After March 23, our district offices and Central Office will be temporarily closed and will have increasingly limited ability to receive deliveries, plans, etc. All entities are encouraged to submit plans, permit applications, etc., electronically where there are existing avenues to do so, such as the eBusiness Center (eBiz). Please refer to the list of available services on the main eBiz webpage. We encourage you to make use of all that apply, even if you have not used eBiz in the past. Plans under 25 MB can be emailed. For large plans over 25 MB, entities should work with the reviewer/division to upload via LiquidFiles. Directions for submitting docs via LiquidFiles is available on YouTube. We apologize for the inconvenience and thank you in advance for your understanding. If you wish to send hard copies of documents to any of Ohio EPA’s district offices, the best method to ensure we receive these documents is to send them via U.S. Mail. Since all offices are closed, deliveries outside of U.S. Mail (FedEx, UPS) will likely be returned because the offices are closed and deliveries cannot be made.

To report a spill or environmental emergency, contact the spill hotline (800) 282-9378 or (614) 224-0946

Water Quality Standards Program

Our water quality is constantly threatened by many different sources and types of pollution. Under the Clean Water Act, every state must adopt water quality standards to protect, maintain and improve the quality of the nation's surface waters. These standards represent a level of water quality that will support the goal of "swimmable/fishable" waters. Water quality standards are ambient standards as opposed to discharge-type standards. These ambient standards, through a process of back calculation procedures known as total maximum daily loads or wasteload allocations form the basis of water quality based permit limitations that regulate the discharge of pollutants into surface waters under the National Pollutant Discharge Elimination System (NPDES) permit program.

U.S. EPA's water quality standards website is at https://www.epa.gov/wqs-tech.

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
  • antidegradation provisions.

Brief summaries of these components are below.  For a more detailed summary, see:

Implementation of Ohio's water quality standards set forth in Chapter 3745-2 of the Ohio Administrative Code (OAC), includes rules for developing water quality based effluent limitations in NPDES permits for point sources and total maximum daily loads (TMDLs) for discharges of any pollutant requiring control, including toxic, carcinogenic, and organoleptic pollutants.

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.

Ohio drainage basins and associated rule numbers in OAC 3745-1

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.

Chemical 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 rule 3745-1-44, rule 3745-2-09, and paragraph (B) of rule 3745-33-07 of the OAC.

Biological Criteria

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 (C) 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.

Summary Tables

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 Feb. 3, 2017. The Ohio River table was last updated on February 3, 2017.


Information about the Great Lakes Initiative, including the GLI Toxicity Data Clearinghouse, is on the U.S. EPA Great Lakes Initiative (GLI) Clearinghouse website.

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 water quality criteria are in rule 3745-1-33 (public water supply) and rule 3745-1-34 (fish consumption). The numerical aquatic life and wildlife water quality criteria and other types of numerical water quality criteria are in rule 3745-1-35.  Criteria to protect the recreation use (E. coli) and aesthetic conditions are found in rule 3745-1-37. These rules are available here:

  • 3745-1-33 Water quality criteria for water supply use designations      
  • 3745-1-34 Water quality criteria for the protection of human health [fish consumption]      
  • 3745-1-35 Aquatic life and wildlife criteria
  • 3745-1-37 Water quality criteria for recreation use designations and aesthetic conditions

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.

  • 3745-1-40 Methodologies for development of aquatic life criteria and values
  • 3745-1-42 Methodologies for development of human health criteria and values for the Lake Erie drainage basin
  • 3745-1-43 Methodology for development of wildlife criteria for the Lake Erie drainage basin
Water Quality Standards
Rush, Audrey Manager, Water Quality Standards, Human Health Criteria (614) 644-2035
Hood, Mariah Fish Tissue Contamination, Sediments (614) 644-2865
Miltner, Robert Nutrients, Statistical Analysis (614) 836-8796
Skalski, Chris Aquatic Life Criteria, Bacteria, PHWH, Use Designations (614) 644-2144