In an unusual example of regulatory cooperation, industry and environmental groups, with the encouragement of the U.S. Environmental Protection Agency, have reached agreement on a draft plan covering how to deal with sewage flow diversions during rainy weather. The National Association of Clean Water Agencies and the Natural Resources Defense Council announced Oct. 27 that they had agreed on draft guidance for such diversions. The two groups have sent their proposed language to the Environmental Protection Agency, which will determine whether to issue it as formal federal interpretive guidance.

NACWA says that during large storms, flows of influent sometimes exceed the capacity of the secondary treatment units in many localities. Those flows then can be diverted around those facilities and with flows from the secondary treatment units or discharged from the plant directly into waterways.

The proposed joint guidance applies only to the flows from separate sanitary sewer systems as they are recombined. (To read the draft language, click here and here )

The NACWA-NRDC plan follows a EPA policy that the agency proposed in 2003 and withdrew last May. The House of Representatives had voted to bar the policy from becoming final. NRDC had contended that the EPA "blending" rule would have allowed wastewater facilities to discharge untreated sewage into water bodies "virtually any time it rains."

EPA encouraged NACWA and NRDC to meet and develop mutually acceptable language for the flow diversions. Nancy Stoner, director of NRDC's Clean Water Project, says, "We put our heads together and came up with a workable plan that will protect public health."

NACWA Executive Director Ken Kirk says that the proposal "demonstrates that sound policy can result when organizations stay focused on the critical mission of improving water quality and protecting the public health."

Under the draft language, a permitting agency can allow peak wet weather diversions if the wastewater treatment plant can show there are "no feasible alternatives" to that diversion. The publicly owned treatment works must file an analysis to the permitting authority that evaluates alternatives to a diversion, such as storage; have limiting collection-system extensions or slug loadings from indirect dischargers; using technologies such as biological or chemical treatment, ballasted flocculation, deep bed filtration and membranes; and the local area's ability to finance such improvements.

The proposed regulatory guidance also includes provisions for the permitting authority to follow in reviewing the facility owner's analysis and in making information available to the public.