LID for All: Stormwater Treatment Changes for Federal Projects (Part 1)

No Photo Available By: Charlene Harper

The Energy Independence and Security Act of 2007 is an “omnibus energy policy law that consists mainly of provisions designed to increase energy efficiency and the availability of renewable energy.”  Amid the provisions requiring a CAFE standard 35 mpg by model year 2020 and a 30% decrease in total energy use in federal buildings by 2015 is a small paragraph calledSection 438.  Section 438 simply states that federal facility development projects exceeding 5,000 sf must use site planning, design, construction and maintenance strategies to maintain or restore, “to the maximum extent technically feasible,” the predevelopment hydrology of the site.  This is a far bigger deal than it might appear at first reading.

In December, 2009, the USEPA issued guidance on meeting Section 438 with two purposes:  first, to define “maximum extent technically feasible;” and second, to adopt a process for restoring or maintaining the predevelopment site hydrology.  The method is Low Impact Development (LID), a design technique in which treatment measures are integrated throughout the site layout to capture stormwater as close to where it falls as possible.  These pockets of retention and treatment help recharge groundwater and mimic the natural site’s ability to absorb rainfall before runoff begins (a.k.a. initial abstraction).

The treatment measures, which infiltrate, evapotranspirate and/or harvest and reuse stormwater, are known as “green infrastructure” and a palette of these options are as follows:

  • Conservation and/or reforestation of riparian buffers and floodplains
  • Infiltration
  • Rain gardens/bioretention
  • Amended soils
  • Tree box filters and flow through planters
  • Vegetated swales
  • Vegetated medians and islands
  • Porous and permeable pavements
  • Green roofs
  • Rainwater harvesting/cisterns/rain barrels

Part 2 of this series will explore the sizing goals for these measures and how section 438 guidance dovetails with both LEED and the runoff reduction method…