By Ted Blahnick, PE
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.