Seeking clarity: EPA proposes suspension of numeric turbidity limitation for stormwater discharges from construction sites

Late last week, EPA proposed suspending its efforts to impose a numeric limitation on the allowable level of turbidity in stormwater discharges from certain construction sites as part of a settlement with several industry groups who had challenged a 2009 final rule establishing such a limitation.

Turbidity describes the cloudiness of a liquid caused by suspended solids. High turbidity can create conditions that are inhospitable to aquatic life, such as increased water temperatures and reduced dissolved oxygen levels. When suspended solids clog fish gills, they can reduce resistance to disease, lower growth rates, and disrupt egg and larval development. When suspended solids settle on stream bottoms, they can smother fish eggs and the bugs that support other aquatic life.

An interesting property of suspended solids is their tendency to scatter a beam of light that is focused on them. An instrument called a nephelometer, which contains a detector that receives more light in the presence of more suspended solids, can be used to measure turbidity in units called nephelometric turbidity units, or NTUs.

In 2009, EPA promulgated Effluent Limitations Guidelines and Standards for the Construction and Development Point Source Category (commonly referred to as the C&D rule). In addition to imposing non-numeric/best management practice (BMP) requirements on certain construction and development activities, the C&D rule required discharges associated with certain construction sites not to exceed an average turbidity of 280 NTUs, a limitation based on passive treatment control technologies, including polymer-added settling.

Not long after promulgation of the C&D rule, the Wisconsin Home Builders Association, the National Association of Home Builders (NAHB) and the Utility Water Act Group challenged the rule in three separate actions that were consolidated in the U.S. Circuit Court of Appeals for the Seventh Circuit in a case captioned Wisconsin Builders Association, et al. v. EPA, Nos. 09-4113, 10-1247, and 10-1876 (7th Cir.).

In late 2010, after being presented with potential deficiencies in the dataset that it used to support its decision to adopt the numeric turbidity limitation, EPA issued a final rule to stay the limitation indefinitely. Late last year, EPA entered into a settlement agreement to resolve the litigation.  The settlement agreement required EPA to propose for public comment certain changes to the C&D rule by April 15, 2013. EPA issued the proposed rule last week, which was published in yesterday’s Federal Register.

Changes to the non-numeric/BMP portion of the C&D rule include the addition of a definition of the term “infeasible” and revisions to certain effluent limitations, both intended to clarify the requirements of the rule.

The definition of “infeasible” in the proposed rule is an amalgam of EPA’s preamble language from the 2009 final rule and language from the 2012 Construction General Permit that EPA issued in February 2012 (also challenged by the NAHB). Under the proposed rule, “[i]nfeasible means not technologically possible, or not economically practicable and achievable in light of best industry practices.”

Changes to the effluent limitations in large part serve to more closely tether their requirements to the Clean Water Act goal that they are seeking to implement – the minimization of pollutant discharges to navigable waters from construction sites before site stabilization, consistent with intended site functionality.

The additional clarity provided by the proposed rule’s changes to the non-numeric/BMP portion of the C&D rule is mere icing. The cake is the proposed rule’s withdrawal of the C&D rule’s numeric turbidity limitation. That cake, however, may have a short shelf-life. The summary of the proposed rule provides that “EPA is proposing to withdraw the numeric limitation but reserve the paragraphs in the regulation in the event that a numeric limitation is proposed and finalized in the future.”

EPA is still considering data and information regarding numeric discharge standards for construction sites. So while numeric standards need not be incorporated into permits today, a new rulemaking implementing numeric standards may yet be on the horizon.

Today, industry may enjoy its cake. Tomorrow, it may have to eat its vegetables.