Although federal and California regulations have introduced numeric effluent limits (NELs) for stormwater discharges, technical issues and an adverse regulatory environment have stalled these efforts. This article summarizes stormwater regulatory history and the current regulatory atmosphere.

In 1987, Congress amended the Clean Water Act to mandate the control of stormwater discharges in municipal, industrial, and construction arenas. In 1990, the United States Environmental Protection Agency (USEPA) first issued regulations defining stormwater discharges as point source discharges subject to a broad array of pollution control requirements under the National Pollutant Discharge Elimination System (NPDES). Most environmental professionals are now familiar with the stormwater pollution prevention plans and stormwater monitoring required by USEPA and state agencies with approved Clean Water Act implementation programs.

To control construction and industrial stormwater discharges, USEPA requires mandatory implementation of certain best management practices (BMPs) and reporting of stormwater discharge constituents to established USEPA "benchmark" values, known as water quality-based effluent limits (WQBELs). When stormwater discharges contain constituents in excess of the "benchmark " values, the discharger must review and revise the selection, design, installation, and implementation of control measures and must complete appropriate corrective actions to prevent recurrence of the exceedance.

This approach was explained by the directors of the USEPA Office of Wetlands, Oceans and Watersheds and the USEPA Office of Water in a November 22, 2002, memo as follows:

EPA expects that most WQBELs for NPDES-regulated municipal and small construction storm water discharges will be in the form of BMPs, and that numeric limits will be used only in rare instances...

...[I]n light of 33 U.S.C. §1342(p)(3)(B)(iii), EPA recommends that for NPDES-regulated municipal and small construction stormwater discharges effluent limits should be expressed as best management practices (BMPs) or other similar requirements, rather than as numeric effluent limits.

The use of BMPs and iterative monitoring seemed firmly established.

In response to a court ruling requiring USEPA to develop effluent limitation guidelines (ELGs) and new source performance standards (NSPS) for construction activities (NRDC vs. EPA), USEPA issued a new construction and development point source category rule in December of 2009. The rule established nationally applicable ELGs and NSPSs to NPDES permits covering stormwater discharges from construction sites, including best management practices and the first ever numeric limit for turbidity.  The State of California had pioneered the use of numeric effluent limits (NELs) in its general construction stormwater permit in September 2009, and it appeared that the USEPA was following its lead.

The USEPA construction point source category rule was quickly challenged in a lawsuit by industry groups and an administrative review petition by the Small Business Administration Office of Advocacy. One of the main claims in the challenge was that the turbidity limit was flawed. On November 5, 2010, the USEPA stayed the numeric effluent component of the construction point source category rule, pending a re-evaluation of turbidity data used during the development of the rule.

Nonetheless, further evidence of USEPA's changing perspective on NELs can be found in a memo issued in November 2010, revising the previous November 2002 memo, as follows:

...expectations have changed as the stormwater permit program has matured. EPA now recognizes that where the NPDES authority determines that MS4 discharges and/or small construction storm water discharges have the reasonable potential to cause or contribute to water quality standards excursions, permits for MS4s and/or small construction stormwater discharges should contain numeric effluent limitations where feasible to do so. EPA recommends that NPDES permitting authorities use numeric effluent limitations where feasible as these types of effluent limitations create objective and accountable means for controlling stormwater discharges.

This publication of this memo also spurred a strong response from the regulated community. Further concern grew as California issued a new draft general permit for stormwater discharges from industrial activities in January of 2011 that also included NELs.

The apparent introduction of NELs to stormwater discharges had significant setbacks in the latter half of 2011. In California, the newly created Senate Select Committee on California Job Creation and Retention focused its attention on the draft general permit for industrial activities. The committee scolded the state agency responsible for drafting the permit for creating a permit that greatly increased regulatory costs, was in conflict with newly enacted tax measures, and was created with little stakeholder input.

In December 2011, a California Superior Court invalidated the NELs established in the general permit for construction activities adopted in 2009. The Court found that NELs had been developed without sufficient scientific evidence; therefore, the state had not complied with federal laws when it established the limits in the permit. (Some observers felt that the Court was influenced by USEPA's recent stay of it NELs.)

Perhaps then it should come as no surprise that NELs were absent from USEPA's final issue of its new general construction permit in February 2012. USEPA indicated that NELs had not been included because the agency "is still in the process of collecting data to support the recalculation of the numeric turbidity limit."

When and if NELs will be established for storm water discharges by USEPA remains to be seen. In California, often a regulatory bellwether, proposed legislation revises state water agency permit issuance procedures and prohibits the establishment storm water effluent standards more stringent than provisions of the Federal Clean Water Pollution Control Act until January 1, 2017. The establishment of NELs for storm water discharges will most likely remain controversial for some time. 

Martin Bermudez, CHMM, is an STC Senior Program Director with over 20 years of experience in environmental, health and safety (EHS) regulatory compliance and management system development and implementation. His experience ranges from performing focused projects in chemical process safety management, hazardous waste management, facility closures, and EHS program risk assessments to broad-based projects in environmental management information system design and management system evaluation. Martin's clients include various industries-telecommunications, mining, medical devices, biotechnology, apparel, pharmaceutical, semiconductor, paint and coating, industrial tool manufacturing, automotive parts manufacturing, and electronic product assembly-in the U.S., Canada, and Mexico. He has evaluated and developed storm water pollution prevention plans for transportation, industrial manufacturing, residential development, and automobile dismantling sites.

To learn more about STC's stormwater compliance management services, contact Martin at (510) 909-5460 or via email at mbermudez@stcenv.com.