Launch Slideshow

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How to go green by 2013

How to go green by 2013

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    Porous pavers being laid to complete a stormwater plaza in Indianapolis.

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    TABLE 1/Per-unit control values Figures based on managing 80% to 90% of annual runoff volume in well-drained soils or poorly drained soils with underdrains .

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    TABLE 2/Installation unit costs Based on data from 29 suburban, urban, and green space retrofits in Indianapolis and Columbus, Ohio; the Center for Watershed Protection's Urban Stormwater Retrofit Practices Manual v1.0; Water Environment Research Foundation's BMP and LID Whole Life Cost Models v2.0 report; the Center for Neighborhood Technology's Green Values Calculator; and RS Means Site Work & Landscape Cost Data 2009, 28th Ed.Visit www.pwmag.com for direct links to these tools.

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    TABLE 3/Costs per square foot of impervious surface managed Dividing the installation cost (Table 2) by the area managed (Table 1) yields the budget manager's Holy Grail: C/I.

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    Figure 1. BMP annual runoff removal effeciencies for varying soil infiltration rates

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    Figure 2. Cost efficiency relative to intensity of application

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    Urban residential retrofit (no underdrains)

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    Downtown commercial retrofit (with underdrains)

By Ted Blahnick, PE

Glossary

BMP: best management practice

C/I: cost/square foot of impervious surface managed/square foot of BMP

GI: green infrastructure

ISA: impervious surface area

LID: low-impact design




To better comply with the Clean comply with Water Act, EPA is preparing to expand its reach beyond separate and combined-sewer communities to bring the nation under a new, uniform quality standard for old as well as new development. It's the next step toward replacing our patchwork of widely varying — city by city, state by state, region by region — control requirements with one standard that applies to all watersheds.

In addition to focusing on flood control — i.e., designing for individual events — regulators will expect National Pollutant Discharge Elimination System (NPDES) permittees to (NPDES) permittees also control annual runoff volume to mimic predeveloped watershed conditions for typical-year rainfall. The agency's strategies for managing nonpoint pollution emphasize “green infrastructure” that reduces impervious surfaces, increases infiltration, and/or reuses runoff.

The new requirements are expected to be released by November 2012, and they won't affect only stormwater operations. If you haven't already, start reaching out to colleagues in other departments to review and update standards for streets, subdivisions, and other land use.


Control measure metrics

How to calculate the potential cost and impact of best management practices.

The figures on this page represent standalone stormwater projects. But many operations are incorporating runoff-control measures into planned capital improvements like street or curb replacement, a new park, or a roof replacement.

In such cases, the “premium” for a green retrofit may be little or nothing. Which, along with being environmentally friendly, is one of the beauties of green infrastructure.