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Getting Green with CSOs

Winter 2012 Issue

The topic of wet weather makes me think of the many communities across New York struggling with combined sewer system issues. In the past, some sewer systems were designed to collect stormwater runoff, domestic sewage and industrial wastewater in the same pipe. Most of these combined sewer systems were constructed before the advent of wastewater treatment.

The legacy of combined sewers has left us with major challenges to restore water quality in urban areas. During wet weather events, excessive stormwater enters the sewers and can overwhelm the system, causing under treated waste to be discharged into waterbodies. These combined sewer overflows (CSOs) - which can contain high levels of pollution and exceed NYS water quality standards - may pose risks to human and aquatic health and cause beach closures, shellfish bed closures or algae blooms.

Unfortunately, about 10 percent of CSOs in the US occur in New York. The state addresses CSO discharges by requiring them to have a State Pollutant Discharge Elimination System (SPDES) permit, which includes best management practices to optimize the combined sewer system to reduce CSOs. The SPDES permit also requires the development and implementation of a Long Term Control Plan to meet the water quality goals of the Clean Water Act.

Addressing CSOs can be an onerous task for a community. However, we are finding that green infrastructure can effectively complement grey infrastructure to reduce CSOs while providing additional benefits, such as green space in urban areas. The City of New York and the City of Syracuse are two communities that are working to address their CSOs by incorporating green infrastructure into their plans.

New York City was required under a 2005 Order on Consent to reduce CSOs from its sewer system to improve the water quality of its surrounding waters, such as Flushing Bay, Jamaica Bay, tributaries to the East River, Long Island Sound and Outer Harbor. In 2011, the NYS Department of Environmental Conservation (NYSDEC) and NYC modified the existing Consent Order to integrate green infrastructure into the city's Long Term Control Plan. Underway with planning and initial implementation, the city's use of green infrastructure to treat the CSOs looks promising.

In 2009, Onondaga County's Syracuse became the first community in the US to be legally required to reduce sewage overflows using green infrastructure. Onondaga County partnering with Syracuse implemented a strategy to use about two-thirds green infrastructure and one-third grey infrastructure to meet its CSO requirements. Implementing the plan is not cheap. The green infrastructure investments to date total nearly $80 million and are funded through sewer fees, low-interest loans and state grants. Currently 60 projects have either been completed or are under construction.

As more communities explore green infrastructure to address CSOs, the state is making more project funding available. For example, the Water Quality Improvement Projects program, the Green Innovative Grants Program and some NYSDEC watershed programs have offered subsidies for green projects in their last round of funding.

I encourage all communities to consider green infrastructure to help tackle their wet weather issues.