Posts Tagged ‘water quality’

The economic downturn has hastened the move to stormwater green infrastructure (GI) approaches (e.g., permeable paving, vegetative swales, rain gardens, green roofs) as a way to combat combined sewer overflows (CSOs) in the United States. Federal policies that mandate water quality improvements in cities have commonly been met with arguments about how the new measures will not be financially feasible (even in the pre-Clean Water Act days when urban creeks might be called “bubbly” because of methane discharge from rotting waste). However, the financial argument carries weight even with regulators in today’s fiscal environment, and U.S. EPA is now signaling a willingness to be more flexible in the arrangements it makes with cities. EPA’s embrace of stormwater green infrastructure has been apparent for some time, and that trend appears to be set for the foreseeable future. Greenwire, a subscription service, reports on new guidance to regulators from EPA’s water chief, Nancy Stoner, and uses the following example of past agreements with major cities:

Over the past 10 years, EPA and the Department of Justice have sought to stop the overflows by suing cities and striking settlement agreements that require massive upgrades. As a result, at least 40 cities or sewer systems across the United States have entered into such agreements with EPA since 1999.

The agreements tend to require rebuilding pipelines, expanding treatment plants and digging underground tunnels big enough for subway trains. The tunnels act as storage tanks for stormwater that would normally pour into waterways and allow time for treatment plants to clean up the mess.

As part of its 2003 consent decree with the federal government, Washington, D.C., broke ground last month on a $2.6 billion tunnel-building project, the largest since construction of the metropolitan area’s subway system. The tunnel will be 23 feet wide and 100 feet deep and will extend 4.5 miles from the sewage-treatment plant along the east bank of the Potomac River, crossing under the Anacostia River and extending to RFK Stadium on the city’s east side. [Emphasis added.]

With eye-opening treatment options like that, it is no wonder that cities are interested in hosting GI experimentation. Hoping to head off even more tunnel construction, the Washington, D.C. Water General Manager is enthusiastic about contributing to the GI body of knowledge!

“No city or utility has ever done a sustained and large-scale pilot study of green roofs, trees and porous pavement to help in those areas,” D.C. Water General Manager George Hawkins said. “We hope to do just that.”

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What do you do when historical data is no longer useful for predicting the future? Climate change is making the already-difficult proposition of predicting environmental phenomena even harder. Consider societal efforts to manage the flood system. The concept of a 100-year flood is based on the idea that history is useful indicator of future states and “most likely” scenarios. A 2010 paper by Gersonius et al.* tackles the question of how we might begin to plan for shifts in flooding regimes by using adaptive management strategies. This paper is at the leading edge of climate adaptation design research, and there is a need for much more.

Gersonius et al. contrast the traditional approach with an adaptive approach. They say that traditional approaches are based on the assumption “that it is possible to define a singular optimum adaptation strategy according to the ‘most likely’ or average future projection” (p.15). Big investments of public dollars are common with the traditional approach – essentially a large bet on the promise of a singular optimum strategy (one-off interventions). The paper’s authors argue for an adaptively resilient approach instead, an approach better suited to the uncertainties of climate change.

Rather than taking a traditional approach, responsible climate adaptation requires an alternative approach that attempts to assess and manage the resiliency of the flooding system for long-term future change. The aim of this approach is to keep the system within a configuration of states that give at least acceptable functioning despite the occurrence of possible changes (Walker et al. 2002**). This means that the approach acknowledges that projections are ‘always wrong’ and that it is necessary to plan for a range of possible future conditions.

The authors’ modeling results suggest that adaptation decisions that include LEARNING about future climate parameters could reduce overall costs between 5 and 17% over a single high risk traditional, or “robust,” intervention. The figure below illustrates the concept.

(a) Adaptively resilient approach contrasted with (b) traditional "robust" approach

*Gersonius et al. 2010. Managing the flooding system’s resiliency to climate change. Proceedings of the Institution of Civil Engineers ES1: 15-22.

** Walker et al. 2002. Resilience management in social-ecological systems: A working hypothesis for a participatory approach. Conservation Ecology 6:14.

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And you get an article in the New York Times. (The shooting stick reference is found in this earlier post.) The Times featured a proposal by the architectural firm, Taller 13 Regenerative Architecture, to daylight three rivers in Mexico City and turn the now-buried rivers into urban amenities. If you read between the lines, the article reveals both the promise of this landscape urbanist vision (a bold re-imagining of the cityscape that is intoxicating in its sweep) and the pitfalls if the proposal is totally unrealistic. At some point, bold vision has to meet scientific knowledge, technical expertise, and implementation savvy. From the article, “Prophets and young dreamers are rarely very good at diagnosis.” Where is the balance found between dreamy proposals and practical issues of implementation?

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Syracuse is hoping the nickname “Emerald City” sticks, and that “green” is an identity that will distinguish it from its urban competitors. In April, the U.S. Environmental Protection Agency helped add substance to the claim by naming Syracuse one of 10 EPA Green Infrastructure (GI) partnership communities. The designation came in response to an ambitious effort by the City of Syracuse and Onondaga County to use stormwater-focused GI techniques (green roofs, rain gardens, rain barrels, and so forth) on an unusually extensive scale – throughout the urban watershed of the City’s main tributary, Onondaga Creek. The Save the Rain program aims to improve water quality in Onondaga Creek and Onondaga Lake by reducing stormwater runoff that is currently causing combined sewer overflows, a situation common in many U.S. cities. Commitment to the effort, driven by a 2009 amended consent order between NYS Department of Environmental Conservation (DEC) and Onondaga County, the urban context, and scale of the intervention make this an example worth watching.

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