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Write TMDLs with the Right Water Quality Standards
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Pp. 220-220 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA) 701P0102.(doi:10.13031/2013.7561)
Authors: Mark Landry, Gerald Stedge, and Leonard Shabman
More than 20,000 water bodies nationally do not meet state water quality
standards. The Clean Water Act requires states to list these impaired water
bodies and develop a Total Maximum Daily Load (TMDL) for each. Historically,
states were directed to list impaired water bodies promptly due to imminent court
actions. Across the U.S. emphasis has focussed on the cost, feasibility,
efficiency, and necessity of developing TMDLs based on the scope of the policy.
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A TMDL is a policy instrument for states to meet their own water quality
standards. Most often state water quality standards are not site- or state-specific
and may not even be intended for the designated use of the impaired water body.
A more sensible approach would be to undertake an integrated assessment of
the physical, biological, and economic impacts of the designated use of the water
body to ascertain the appropriate designated use and associated water quality
standards. Then, if ambient water quality standards are not met, a TMDL can be
established. This approach will ensure that state resources are targeted towards
water bodies where the TMDL approach is most effective and most appropriate.
For example, most surface waters are designated for recreational use under the
primary contact standard (fishable and swimmable). In many instances a state
may demonstrate to EPA after performing a Use Attainability Analysis (UAA) that
the intended use is not appropriate, thus satisfying the Clean Water Act because
a lesser use (fishable only) is the best use that is attainable. Findings of a UAA
may merit a use downgrade due to declining economic or social conditions
associated with improving water quality. A second outcome of a UAA may
warrant antidegradation, which is lowering the water quality standard to
accommodate economic or social development in the area.
Guidelines for conducting UAA have already been developed by EPA and the
Water Environment Research Foundation. This study outlines the steps and
procedures necessary for states to target and use UAA in conjunction with TMDL
development and implementation. The objective of this analysis is to critically
assess how UAAs can be used by states to establish, review, or modify
designated uses and water quality standards. Previously conducted UAAs will be
reviewed to estimate the effectiveness of developing site-specific designated
uses and water quality standards. A national overview of the potential impacts of
UAA on TMDL development and implementation will be presented. This analysis
suggests that states should consider conducting UAAs to comprehensively
assess pollution-impaired water bodies and to aid in cost-effectively applying the
TMDL approach to meet water quality standards.