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EPA Proposes Limited Relief to City Sewer Plants Experiencing Storm Water Problems

By Rich Anderson
March 29, 2004

The U.S. Conference of Mayors' Environment Committee and Urban Water Council urged James Hanlon of the U.S. Environmental Protection Agency (EPA) to adopt a proposed clarification of the so-called "bypass and blending" policy. When wastewater treatment plant operators experience major storms and flooding they will divert ("bypass") storm water around certain treatment processes that could be damaged by flooding. Operators then "blend" the bypassed storm water into various parts of the treatment works with normal wastewater. Critics of the practice, and some EPA Regional Offices have expressed concern over the resulting water quality of the blended effluent.

Citing great uncertainty related to regulatory compliance and the need for costly capital improvements, mayors at the U.S. Conference of Mayors- Winter Meeting held in Washington, DC hand delivered a letter of support for EPA's proposed policy clarification. The National League of Cities, the Association of Metropolitan Sewerage Agencies and the Water Environment Foundation Similar submitted similar petitions to EPA.

Cities responsible for sewer plants (Publicly Owned Treatment Works-POTWs) have anxiously awaited action by the EPA concerning regulations governing storm related overflows. Regulations either in effect or being shaped now by the EPA could result in costly changes for cities. Even if a city is not responsible for the sewer works citizens ratepayers will shoulder the potential cost increases for water diversion systems or mandated capital improvements. The "bypass and blending" policy could substantially disrupt current wet weather overflow management practices.

The EPA proposed both an interpretation of and guidance for wet weather peak flow policy for POTWs on November 7, 2003. EPA acknowledged that cities and water authorities that hold National Pollutant Discharge Elimination System permits (NPDES) are experiencing confusion with state regulators and environmental activist groups over what the legal requirements are for handling potential overflows during and after wet weather episodes. What made the situation particularly difficult for the many cities around the nation trying to comply with the regulations was the fact that the 10 EPA Regions did not interpret or enforce the policy consistently.

"Bypass and Blending" — an Operational Practice

The heart of the issue involves wet weather peak flows where storm waters enter into the sewer collection systems and overwhelm the secondary and/or advanced treatment systems. Often times such overflows damage the treatment units and result in discharges of untreated sewage into receiving waters. Plant operators have for some time diverted some or all of the storm-flow around the secondary (biological) treatment units into excess primary clarification units for storage or to retention basins. This practice is called "bypass." When flows return to normal conditions the operators blend the stored storm water in with wastewaters that have been processed through the treatment system. This practice is called "blending." Some operators discharge the bypassed storm water directly into receiving waters.

EPA regulators in EPA's Regional Offices and state regulators have interpreted bypass and blending policy differently. Some regulators agree with plant operators that as long as the blended discharge meets effluent standards and the water quality standards of receiving waters there is no environmental degradation and all permit requirements have been met. Other regulators, however, contend that the bypass storm water must be re-directed to the treatment systems and undergo secondary and/or advanced treatment in the plant. The blended effluent must meet effluent limitations as well as the water quality standards of the receiving waters.

Plant operators argue that re-directing the bypass storm water to the secondary/advanced treatment systems of the plant is an unnecessary and costly step. They also argue that the bypass approach is necessary to prevent the secondary treatment from being damaged. Due to the unique conditions at various wastewater treatment plants operators have long advocated for bypass and blending policies that work for their particular situation, and that a "one size fits all" policy is unacceptable. In short, site'specific plans are necessary to identify the optimal mix of wet weather management flows.

EPA Proposes Policy Changes

Current EPA regulations prohibit bypass ("the intentional diversion of waste streams from any portion of a treatment facility") except when it is necessary to maintain or ensure the efficient operation of a plant. The prohibition against bypass may be waived if the resulting bypass does not exceed effluent limitations. Thus, water quality degradation is not likely.

The proposed policy addresses: 1) interpretation of the bypass provision as it applies to alternative wet weather treatment scenarios; and, 2) draft guidance on how the interpretation should be implemented at the permit level.

EPA elaborated six "principles" that must be followed in order for cities to take advantage of the bypass provision and protect water quality at the same time. The principles require that final discharges must meet effluent standards; permits must describe the bypass and blending plans including a demonstration that no feasible alternatives are available; monitoring and record keeping must be implemented to describe the bypass and blending activities; and, permits must provide plans to properly operate and maintain all treatment equipment at all times.

The EPA extended the comment period on the proposed rule to early February. Jim Hanlon, EPA's Director of the Office of Wastewater, told mayors attending the Urban Water Council meeting that the Agency will review public comments and make a determination if any changes to the proposal are warranted. No particular time frame was identified for completion of the proposed policy changes.

For more information, contact Kevin Weiss at 202-564-0742 or by email at The official Docket ID for the bypass and blending policy is ID No. OW-2003-0025.