Broad Channel — The July 20 fire at the North River Wastewater Treatment Plant, on the shore of the Hudson River in upper Manhattan, shut the plant down for 64 hours while workers toiled feverishly to repair it. During that time, an estimated 200 million gallons of pure untreated sewage flowed directly into New York City's waterways – a little more than the capacity of two medium-sized oil tankers.

It was the city's highest-profile sewage disaster in years, but whether it was the worst is a matter for debate. Another– though less spectacular – candidate for that honor is the ongoing overflow of sewage and stormwater runoff that happens as a matter of course whenever there is heavy rain.

These releases, known as combined sewer overflows, or CSOs, stem from an antiquated city sewage system that channels household waste and storm runoff through the same pipes. When rainwater washing in from city streets fills the sewage system and threatens to overwhelm the treatment plants at the end of those pipes, officials divert the mixture into the city's rivers and bays.

The release is not as concentrated as the undiluted sewage from the North River spill, but it is dirty in other ways – besides the sewage, the storm runoff contains trash and chemicals from streets and storm drains. Also, there is more of it: about 27 billion gallons, or roughly 320 of those same oil tankers, into New York Harbor alone each year.

The good news, city officials say, is that they are working on the problem. In May, a $400 million facility opened at Paedergat Basin, in Brooklyn, that will temporarily store overflow in holding tanks underground, preventing the discharge of some 1.2 billion gallons a year into Jamaica Bay. Moreover, last September the city's Department of Environmental Protection unveiled its Green Infrastructure Plan, which aims to reduce overflows even further by stemming runoffs, using features like green roofs and permeable sidewalks on public and private sites around the city.

The bad news – aside from the hundreds of gallons of sewage and storm runoff in the water every year – is that implementing the plan will take time, and environmental advocates are raising questions about major parts of the city's approach. That, they say, fits with the overall story of water quality in the city – one of tentative steps forward against the backdrop of a queasily familiar status quo.

Plan faces hurdles
The Green Infrastructure Plan aims to reduce CSO volume by more than 12 billion gallons a year by the time it is fully implemented – a process that would take 20 years. Before the clock starts ticking on that implementation window, though, the plan must clear several procedural hurdles.

One is with the state Department of Environmental Conservation, which regulates city-run sewage treatment plants and the city's CSO abatement program, and which must grant its approval for the city to incorporate the Green Infrastructure Plan by amending existing rules. Negotiations between the city and state surrounding that approval are confidential, a DEC spokesman says, and have been going on for the last year. They are expected to yield a draft version of the new regulations soon, the spokesman says.

Even on matters that do not require state approval, the process of translating the concepts and broad goals of the Green Infrastructure Plan into detailed, binding law is laborious. Because much of the land where green infrastructure components can be installed is privately owned, the city is proposing an extensive set of incentives and regulations aimed at encouraging better stormwater control on private property. Many of the requirements – which would apply to new developments and modifications of existing buildings – are still in draft form, in a Department of Environmental Protection document called "Guidelines for the Design and Construction of Stormwater Management Systems.”

That document, some environmentalists say, is one place where the city's implementation of sewage overflow-prevention measures falls short of its lofty goals.

In a letter to the DEP this month, the Natural Resources Defense Council said it was "deeply concerned"that the draft guidelines not only would not encourage property owners to install green infrastructure, but could actively discourage them.

Among the group's objections, says Eric Goldstein, the group's director of New York City environment, is an emphasis on slowing the rate at which stormwater flows into the sewage system, rather than reducing its overall volume. The distinction is important: Slowing the water's entry into the system is a partial solution for controlling floods in some storms, he says, but would not do enough to reduce overall water pollution. Nor, he says, is there proof that simply delaying the release of stormwater into the sewage plants – rather than permanently diverting it, to be re-used, evaporated or absorbed elsewhere – will be enough to reduce CSOs.

"The whole heart and soul of green infrastructure," Goldstein says, "is to capture stormwater on your property and use it for other purposes, not simply to send it at a lower rate to sewage treatment plants.”

Besides, says Phillip Musegaas, Hudson River program director at Riverkeeper, reducing the volume of pollution should be the ultimate goal. In a recent regional water-quality sampling project, he said, the river failed tests for swimmable water quality 21 percent of the time – in contrast with a 7 percent failure rate for beaches nationwide.

"They have to be able to have a plan that really sets out a roadmap to getting back to clean water and making these waters fishable and swimmable,"he says. "Everyone agrees that the goal is reducing stormwater pollution. But we want to make sure they reduce it to the point that the Hudson River and the harbor meet water quality standards.”

Questions around incentives

Because of the guidelines' emphasis, the NRDC argues, developers who want to install green infrastructure elements like green roofs or other planted spaces receive little incentive from the city, and in fact may have to spend more money complying with regulations that the group calls misdirected. One example: the guidelines provide incentives for developers to build underground or rooftop storage tanks – which detain water only temporarily – but not green space or permeable pavement, which can absorb it permanently. And the proposed guidelines impose regulations on where infrastructure can be installed on private property, and the manner in which soil borings must be done, that strike the advocates as unnecessarily restrictive.