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New Strategies for Controlling Stormwater Overflows

With stormwater a major pollutant, cities are coming up with innovative "gray" and "green" ways to control its impact.

Portland, Ore.'s "Big Pipe" will soon be ready for action. Much of the untreated sewer and stormwater that spills into the Willamette River will begin flowing into the $430 million underground tunnel -- 22 feet wide and six miles long. The Big Pipe will greatly reduce the amount of raw sewage that sloshes into the river, fixing an older system.

As in many cities, Portland’s older neighborhoods were being served by a series of pipes that collect both sewage and stormwater, the latter being water that flows over impervious surfaces into the storm drain. When rain comes pouring down, these pipes are designed to overflow, sending millions of gallons of raw sewage straight into the river. Under this system, Portland has about 100 combined sewer overflows per year. With the help of the Big Pipe, which will store and divert overflows to a treatment plant, the number should drop to fewer than five. "It is," says Dean Marriott, director of the city’s Bureau of Environmental Services, "a 94 to 95 percent improvement."

Portland isn't the only city investing hundreds of millions of dollars to manage sewer overflows. Under federal mandate, dozens of municipalities are proceeding with mitigation projects, including "gray solutions," such as massive tunnels, as well as "green solutions," like eco-roofs and landscaped curb extensions that absorb stormwater before it ever enters the sewer system.

Triggered by environmental degradation (Portland’s Big Pipe grew out of a lawsuit filed by a clean water organization), the combined sewer initiatives spotlight the problems associated with stormwater, which is becoming a leading cause nationwide of water pollution. Regulators are taking note. The U.S. Environmental Protection Agency (EPA) is expected to enact new national stormwater regulations by 2012 -- and the agency already is beginning to issue specific pollution criteria for states, cities and developers. The rules could cost municipalities millions of dollars. Florida, for one, puts a number on that cost. In a lawsuit it filed against the EPA, it claims that new EPA standards, which, for the first time, set statewide limits on the amount of allowable nutrient pollution (from wastewater and stormwater), will cost Florida governments and industry up to $200 billion.

But if the costs -- and federal controls -- are sparking local pushback, the stricter regulations also are expected to create a more sustainable urban landscape, giving cities an economic boost in the process. As urbanization increases, so does the amount of stormwater runoff, explains Jon Devine, a senior attorney for the National Resources Defense Council water program. The obvious solution is to return the landscape to a more natural, permeable state -- an approach that will require an army of eco-friendly landscape architects and urban design professionals. "We think there is going to be an industry boom in meeting the new requirements," Devine says. "We're going to see a renaissance in urban and suburban green infrastructure."

The Problems Caused by Stormwater Runoff

Like sewage, stormwater is something of a dirty little secret, channeled out of sight through a network of underground pipes, only to emerge to contaminate lakes, rivers and streams. Combined sewer systems, which exist in about 700 cities, are only one part of the stormwater conundrum, which as Devine puts it, is "a multi-headed beast."

To understand what he means, consider the myriad problems urban rainwater creates. In a natural environment, rainwater is slowly absorbed into the ground. But in the concrete-covered city, the water has nowhere to go but into the sewer system, which discharges high volumes into streams, eroding banks and filling waterways with sediment.

There are other adverse impacts. As stormwater flows across asphalt and fertilized lawns, the runoff picks up oil, metal, pesticides and other contaminants, with toxic results for wildlife, habitat and people. About 13 percent of U.S. rivers, 18 percent of lakes and 32 percent of estuaries are classified as impaired by stormwater, which means they’re unsafe for swimming or fishing.

Under the current permitting system, the EPA issues guidelines for cities and states on how to manage stormwater impacts. But environmental groups have criticized those standards, which tell builders to reduce runoff to the "maximum extent practicable," as vague and ineffective. Monitoring of sewer overflow systems has also been weak, clean water advocates say.

Responding to those criticisms, the EPA is beginning to define its requirements more precisely. "The mechanisms in the Clean Water Act that deal with stormwater and overflows are beginning to be implemented in keeping with how other pollutants are regulated under the law," Devine says.

As oversight becomes more rigorous, states and localities are responding with varying degrees of compliance and resistance. Kansas City, Mo., for example, partnered with the EPA to craft a $2.4 billion agreement to reduce combined overflows, which results in annual discharges of 7 billion gallons of raw sewage into the Missouri, Blue and other rivers. “We are on this path because we knew intervention was coming,” says Francis Reddy, project manager for the Kansas City Water Services Department. "Instead of having the feds file a suit, we contacted them." The plan features a combination of tunnels, sewer rehabilitation, water treatment technologies and green infrastructure, including curbside gardens and rain barrels to sequester stormwater.

Staking a claim to innovation, Philadelphia aims to bypass the typical storage tunnels entirely. Instead, the city’s $1.5 billion plan focuses almost exclusively on eco-friendly solutions -- bioswales, permeable pavement, street trees -- as a way of reducing the city’s 15 billion gallons of annual overflow. According to Howard Neukrug, director of the Philadelphia Water Department’s Office of Watersheds, the city is "wrestling with the EPA" on details of the proposal, including the timeline and metrics for success.

For their part, EPA officials say the scale of Philadelphia's commitment to green infrastructure for wet-weather control is impressive. "We are working closely," says David Sternberg, a press officer for the EPA's Region 3 office. The EPA, he notes, wants "to ensure that this is an iron-clad model that advances green techniques while also ensuring full compliance with our combined sewer overflow policy."

On the subject of nutrient pollution -- one head of the stormwater beast -- Florida isn't working quite as companionably with federal regulators. Although the attorney general's office declined comment on the pending lawsuit the state filed against the EPA, Florida claims that states are responsible for water quality control and that the new rules, which stemmed from a settlement with environmental groups, infringe on Florida’s clean water program.

David Guest, an attorney with Earthjustice, a legal defense group that represented five environmental groups in the original case, notes that the federal clean water standards aim to reduce phosphorus and nitrogen deposits. These toxic deposits, he says, have created a "thick green slime" in Florida’s waterways.

Initially, local governments in Florida seemed more likely to embrace the new regulations. About 40 cities and counties have already taken steps to restrict use of urban fertilizer -- which contributes to the nutrient pollution. Nevertheless, in January, the Florida League of Cities, along with Pinellas County, also filed suit to stop the EPA limits. For their part, state legislators aim to pass a law this session that would roll back the local fertilizer ordinances.

Increased Utility Costs and Financial Incentives

The EPA has issued a statement that refutes Florida's "exaggerated doomsday claims" regarding the high costs that Florida municipalities and residents will assume as a result of the new rules. Instead of $200 billion, the agency puts the cost at about $130 million. Nevertheless, as more cities embark on stormwater and wastewater control projects, utility customers nationwide can expect higher utility bills. In Portland, one of the first cities to build a large tunnel -- the Big Pipe is actually one of two overflow tunnels the city built -- residents now pay among the highest sewer rates in the country. Average monthly rates that were $30 in 2001 clock in at about $55 today and are expected to reach $69 by 2016. The Kansas City overflow plan will increase sewer bills by 15 percent for five years and 13 percent for the following eight years.

To help mitigate the expense to residents and diffuse opposition to new stormwater initiatives, a few cities offer financial incentives for property owners who manage runoff onsite. Ensuring affordability is one of the main reasons Philadelphia is embarking on its "green first" stormwater and overflow strategy. In a budget-stressed and shrinking city -- Philadelphia’s population has declined by about 70,000 people in the past decade -- it makes little sense to invest $8 billion in a massive overflow tunnel, says Neukrug. Instead, he prefers taking a lower-cost, street-by-street approach to reducing stormwater, especially since it creates jobs, beautifies the city and increases property values.

It’s a compelling argument. No other city, however, has tried to use green strategies alone to combat combined overflows. Such tactics are considered ideal for new buildings but more difficult to apply in older urban areas with miles of impervious pavement. Portland, considered a leader in sustainable stormwater solutions, uses various infiltration techniques -- disconnected downspouts (they allow roof water to drain to gardens instead of sewers), vegetated curb extensions and porous pavement -- to sequester 35 percent of the total annual stormwater runoff in the combined sewer area; 39 percent is managed by the pipe system.

The green portion of the Kansas City plan targets a 100-acre residential neighborhood that has less asphalt than downtown. If that pilot project proves successful, the city will expand the use of natural stormwater management techniques to other parts of the city.

Certainties Regarding Stormwater Management

As local, state and federal officials debate the efficacy of different stormwater solutions, a few things seem certain. First, managing stormwater is becoming one of the most important environmental issues facing cities today. Second, new urban development policies will leapfrog oceans of concrete in favor of landscaping that is green, grassy and water absorbent. And finally, tighter regulations are expected everywhere -- in the stormwater discharge permit process, as well as standards governing sewers and treatment facilities. "We are," says Marriott, "seeing more and more attention to these issues -- by EPA and the state."

Tina Trenkner is the Deputy Editor for She edits the Technology and Health newsletters.
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