Use Attainability Analysis (UAA)

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What is a UAA?

A use attainability analysis (UAA) is a structured scientific assessment of the factors affecting the attainment of uses specified in Section 101(a)(2) of the Clean Water Act. The factors to be considered in such an analysis include the physical, chemical, biological, and economic use removal criteria described in the EPA' s water quality standards (WQS) regulation at 40 CFR 131.10(g)(1)-(6).

A UAA must be conducted for any waterbody when a state or authorized Tribe designates uses that do not include the uses specified in section 101(a)(2) of the Act or when designating sub-categories of these uses that require less stringent criteria than previously applicable.  States and authorized tribes must hold public hearings for the purpose of reviewing the applicable WQS at least once every 3 years and when revising water quality standards.  States and authorized Tribes must also re-examine waters that do not include the uses specified in section 101(a)(2) of the Act to determine if new information has become available.  If new information indicates that the uses specified in CWA section 101(a)(2) are attainable, then the state or authorized Tribe must revise its WQS accordingly to designate such uses.

Graphic: What is a Use Attainability Analysis (UAA)?

Diagram: What is a Use Attainability Analysis (UAA)? (pdf) (335.56 KB, May 2024, 823-F-24-006)

What are the 6 Factors Under 40 CFR 131.10(g)?

Under 40 CFR 131.10(g) states may remove a designated use which is not an existing use, as defined in § 131.3, or establish sub-categories of a use if the State can demonstrate that attaining the designated use is not feasible because:

  1. Naturally occurring pollutant concentrations prevent the attainment of the use; or
  2. Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State water conservation requirements to enable uses to be met; or
  3. Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; or
  4. Dams, diversions or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in the attainment of the use; or
  5. Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or
  6. Controls more stringent than those required by sections 301(b) and 306 of the Act would result in substantial and widespread economic and social impact.

UAA Process Diagram with Tips for Combined Sewer Overflow (CSO) Receiving Waters

This interactive diagram is intended to help states, authorized tribes, and territories establish or revise designated uses by addressing the steps and questions they should consider while conducting a UAA.  It includes tips for use revisions related to combined sewer overflows (CSOs).

What are some examples of UAAs? (Case Studies)

Case Study
 		 Complexity Type of Action 131.10(g)
Factor(s)
Overview
Crosby Creek in Kansas: The Kansas Department of Health and Environment (KDHE) has developed a worksheet to conduct many simple use attainability analyses (UAAs). The worksheet provides reviewers with information such as the name, location, and description of the waterbody; an assessment of its current recreational uses; and observations of aquatic life. Users can evaluate this information and develop a justification for retaining or changing designated uses. One example of using this worksheet is the Crosby Creek UAA conducted in 2001. In the UAA KDHE proposed primary contact recreation use for Crosby Creek, an upgrade from the secondary contact recreation use designated previously. KDHE also proposes to maintain the current aquatic life use designation. Kansas adopted this change their water quality standards and EPA approved it.
 very simple Assign primary contact recreational use n/a
Overview
Antelope Creek in Kansas: KDHE's UAA worksheet was used for the Antelope Creek UAA conducted in 2001. In that UAA, KDHE did not recommend primary contact recreation as a designated use for this water because of the low flow conditions in the stream (131.10(g) factor 2). The segment fits Kansas' definition of an ephemeral stream, grass or vegetative waterway, culvert, or ditch. Photos are provided with the worksheet to show the dry conditions in the streambed. This change was adopted into Kansas' water quality standards and approved by EPA.
 very simple Redefined as ephemeral stream 2
Overview

Tributary of the Seneca River, NY: The New York State Department of Environmental Conservation (NYSDEC) has used a simple worksheet to document UAAs for aquatic life use support. These worksheets were developed as part of an overall 1985 State "Water Quality Standards Attainability Strategy," which included specific guidance for field biologists on assessing fish propagation for various habitats. The worksheet contains the name and location of the waterbody, a checklist of reasons why the waterbody cannot attain full aquatic life designated uses, and space for additional comments or recommendations. One example is a 1992 UAA for a tributary of the Seneca River in New York. Some segments were changed from Class D to Class C (supportive of both aquatic life and recreational uses), and others were determined incapable of attaining Class C on the basis of 131.10(g) factor 2. The worksheet documents the Department's proposed changes to the designated uses.

 very simple Aquatic life use support 2
Overview

Los Angeles Channels: The Los Angeles Region has many rivers and streams that have been straightened, concrete-lined, or both to move floodwaters from urban areas to the ocean. These channels transport large volumes of water that might not be of adequate quality to support Clean Water Act (CWA) section 101(a) uses (i.e., "fishable/swimmable"). The water quality goals set forth in the Los Angeles Region's Basin Plan specify that all waters in the state should be "fishable/swimmable."

Under certain conditions recreational uses are inappropriate for these channels. During high flow flood conditions, it is not safe to swim in the waters; during summer dry periods, the flow is insufficient for swimming. The Los Angeles Region has opted to issue a suspension of recreational use during periods of high flow. Through a revision to its water quality control plan, the Los Angeles Region established that during high flow events, when it is not safe to be in the modified channels, these waterbodies do not have to meet bacteria criteria. The suspension of recreational uses applies under the rainfall conditions that trigger the Region's swift-water protocols (i.e., rescue squads are on alert if someone should happen to enter the water). With this use attainability analysis, EPA approved the revision to the Water Quality Control Plan for the Los Angeles Region.

 simple Temporary suspension of recreational use 2, 4
Overview

Valley Creek UAA: In this 2001 use attainability analysis, the Alabama Department of Environmental Management (ADEM) provided evidence to support the proposed change for the upper segment of Valley Creek from Agricultural and Industrial Water Supply (A&I) to Limited Warmwater Fishery (LWF). The corresponding water quality criteria are more stringent for waters classified as LWF than for A&I waters. The key element of the LWF classification establishes seasonal uses and water quality criteria for waters that otherwise cannot maintain the more protective Fish & Wildlife (F&W) classification year-round. The LWF classification does not fully meet the water quality uses and criteria associated with the "fishable/swimmable" goal, and therefore a UAA was necessary. In the UAA, ADEM provided information on the physical, biological, and chemical characteristics of Valley Creek; water quality data from sampling stations; discharge monitoring reports from the point source dischargers; and water quality modeling results. EPA approved the revision to Alabama's water quality standards to reclassify Upper Valley Creek for LWF and Lower Valley Creek for F&W.

 simple Assign limited warmwater fishery use 3, 5
Overview

New York Harbor Complex UAA: A 1985 use attainability analysis documents the assessment of waters in the New York Harbor Complex that were not thought to meet Clean Water Act (CWA) section 101(a)(2) goals. In the UAA the New York State Department of Environmental Conservation (NYSDEC) presents historical data on total and fecal coliform and dissolved oxygen, as well as the results of steady-state modeling. The segments considered are effluent-limited waters (i.e., the technology-based effluent limitations required by the CWA are inadequate to meet the water quality standards), with impairment from urbanization, combined sewer overflows (CSOs), and other point and nonpoint source discharges. In the UAA NYSDEC recommends that several segments should be assigned both aquatic life and recreational uses. NYSDEC also recommends that some uses be retained and proposes future monitoring and assessment.

 medium Assign aquatic life & recreational uses 3
Overview

Red Dog Mine UAA: A use attainability analysis (UAA) was performed on Red Dog Creek, which runs through the site of Red Dog mine, the largest zinc mine in the world. Red Dog Creek flows only 3-4 months of the year. Several parts of the creek are affected by mining discharges and some acid rock drainage. In addition, the area contains natural ore bodies, resulting in naturally high concentrations of cadmium, lead, zinc, aluminum, and other metals. Pre-mining surveys done in this area indicated that aquatic life uses were not present because of the toxic concentrations of metals, as well as naturally low pH. The UAA for Red Dog Creek demonstrated that aquatic life uses should be removed because of the naturally occurring pollutants. Because of the natural conditions, the criteria for cadmium, lead, zinc, aluminum, and pH cannot be met without human intervention, precluding that aquatic life uses being met. However, treatment of mine wastewater had led to the presence of Arctic grayling that should be protected. A site-specific criterion for total dissolved solids (TDS) was developed to protect the grayling when spawning. EPA approved these changes to Alaska's water quality standards.

 medium Removal of aquatic life uses & development of site-specific criterion 1, 3
Overview

New World Mining District: Montana's Water Quality Act allows for application of temporary modification of water quality standards where a waterbody is not meeting its designated use. The ultimate goal of the temporary modification is to improve water quality to the point where designated uses are fully supported. As such, temporary standards play a key role in the remediation of damaged water resources, because the underlying designated uses and criteria are established as goals which drive water quality improvements. The duration of temporary standards is set based on an estimate of the time needed for remediation at a specific site, and because the clean up of legacy pollutants often takes time, temporary standards can be and are issued for multiple years. The state uses 20 years as its time horizon for estimating future watershed remediation opportunities, and therefore, temporary standards could be issued for as much as 20 years. The New World Mining District is an example of a well-funded and successful project. The waters were classified as suitable for a number of uses, including drinking water, recreational, and aquatic life uses.

 complex Temporary standards for multiple uses during remediation 3
Overview

Chesapeake Bay: Chesapeake Bay waters have been impaired by nutrients and sediment from point and nonpoint sources. These impairments have led to low levels of dissolved oxygen and inability to meet designated uses. Two use attainability analyses were conducted, with several states involved, to evaluate three of the 131.10(g) factors: natural conditions, human-caused conditions, and economics. Maryland collected a significant amount of monitoring data and developed a model to use the data to assess whether the bay's waters were meeting their designated uses. One result of the UAAs was the decision to refine the aquatic life uses. Five designated uses were identified, and the seasonality of each was considered. Maryland promulgated these designated uses in its water quality standards, and EPA approved the new standards in 2005.

In addition, restoration variances were added to Maryland's proposed water quality standards as refinements to proposed criteria. These variances can be applied over an entire segment of the Bay, rather than directed at a specific discharger or group of dischargers. The temporary modifications allow for realistic recognition of current and attainable conditions while retaining the designated use and setting full attainment as a future goal. In addition, the variance allows for incremental improvements in water quality goals.

 very complex Refined aquatic life uses & restoration variance 1, 3, 6

Download all of the case studies. This file includes 2005 Case Studies of Alternatives to Use Removal. Please note that the purpose of this document is to provide examples of UAAs that states have conducted.  States may conduct UAAs and then choose not to finalize the use change.  For example, MD never adopted a final use change for the Patapsco River following the UAA described on pg. 38 of the document.

What about Potential Economic Impacts?

Refer to the EPA’s Economic Guidance for WQS for assistance in assessing the degree of economic and social impact of potential WQS decisions.

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Last updated on May 15, 2024