The Clean Water Act requires that wastewater discharges achieve instream water quality objectives that are “necessary to protect public health and the environment”. See Leather Industries of America v EPA, 40 F.3d 392 (D.C. Cir 1994). Such water quality objectives
may be expressed as either numeric or narrative standards. For TMDL purposes, the implementation of numeric standards is rather straightforward as the precise level of acceptable water quality is known. Narrative criteria, however, provide no objective basis for determining compliance. Consequently,
such criteria must be converted into a numeric value for TMDL calculation purposes. In essence, this requires the development of a site-specific numeric water quality objective for the parameter of concern, considering factors relevant to achieving the narrative criteria. Recently, both
the federal and state regulatory agencies have begun to impose very restrictive TMDLs for a range of pollutant parameters based upon alleged exceedances of narrative criteria. Such narrative criteria are often related to a “balanced indigenous population,” “excessive nutrient
enrichment,” “organic enrichment” or “excessive sedimentation.” Requirements for detention ponds and other storage facilities to reduce runoff loads and volumes will be mandated based upon these TMDLs for many communities. Putting aside the issue of whether such
impairment actually exists in such waters, the degree of control required through such TMDLs often does not properly implement the Clean Water Act and implementing regulatory requirements (e.g., 40 CRF §131.11). EPA and the states have begun to rely upon “reference sites”
that are unimpaired to establish the level of solids or nutrients allowed to be discharged. This approach allows the regulators to avoid development of complex studies to determine the pollutant levels needed to maintain uses, as is done with numeric criteria development. Such approaches have
one significant flaw – they are all legally deficient. The Act requires a demonstration that the pollutant levels at the reference sites are “necessary” to avoid impairment. Thus, an essential component is missing from these TMDL analyses and there is no basis to conclude
that these TMDLs are necessary to achieve narrative criteria compliance. This paper will review the legal requirements associated with proper implementation of narrative criteria, review three case studies where improper implementation occurred and discuss options for affected parties to
address these regulatory concerns.
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