Grey vs. Green Infrastructure

Date = February 6, 2014
Tags <ESM102>


Grey infrastructure are engineering projects that use concrete and steel.
Green infrastrure are projects that depend on plants and ecosystem services - but they may be totally constructed and artificial.

Example 1: Cooling tower vs. Wetlands

Heat load into rivers and streams is one of the biggest pollution problems in Oregon.

Can use cooling towers or other engineering technology to treat the water from domestic and industrial waste sources.

cooling tower

Alternatively, can employ wetlands with plants and waterfalls to cool the water, such as this picture from the Talking Water Garden in Albany, OR

water fall


  • Cooling towers are a known technology that have been employed and tested.
  • Wetlands have been shown to work but they are more "experimental.
  • Wetlands may have other anticipated issues such as diseases (West Nile, Malaria, etc.).
  • The conditions that lead to cooling tower failure or underperformance are not necessarily related to ecosystem stresses.
  • Wetlands might fail for ecological or biological reasons, putting the ecosystem that is recieving the warm water in danger. This could have a compounding effect on overall ecosystem stress.
  • Cooling towers are basically ugly.
  • Wetlands can be beautiful and provide an asset for biodiversity and recreation.
  • Businesses can be fined if their effluent is not treated but they are not compensated for aesthetic and recreational ammenities.


Example 2: Watersheds vs. engineered treatment and storage

Clean and reliable water may be provided by purifying and storing the water or by using forested watershed or marshes.