Copper Roof Stormwater Runoff - Corrosion And The Environment


  • Corrosion product formation and its interaction with acid rainfall results in the release of copper in stormwater, but this does not necessarily lead to environmental harm.
  • Released copper can be characterized in terms of total, dissolved and ionic copper concentrations.
  • Ionic copper is the form of which has the potential to be toxic to aquatic life but this can be managed by binding and complexing so it is not harmful.
  • Ionic copper, at concentrations sufficiently high to cause acute toxicity of Daphnia pulex, are not observed in the watershed beyond the roof downspout and roof drain at the street, where toxicity was observed. Thus simply allowing the stormwater to flow through the drainage system lowers ionic copper concentration to the level that no environmental harm is observed.
  • The cast iron and concrete piping interacts with the ionic copper and reduced copper concentration.
  • Filters, containing iron filings, may prove to be a practical way of capturing and converting ionic copper so it does not cause environmental harm.
  • The drainage of roof runoff through soil also seems to be very effective in reducing ionic copper concentration.
  • The Lawn Area is the largest contribution to copper flux followed by the New Copper Roof and then the Parking Lot.
  • When a copper roof matures to the point where brochantite forms as an outer protective layer, copper release in terms of total copper and ionic copper, decrease to less than half of the release from a roof with only a cuprite outer layer.
  • Since corrosion of metals can lead to release to the environment, corrosion engineers and scientists should seek to play a larger roll in generating the data needed to develop the good science required to establish relevant and meaningful discharge criteria which protect the environment while not unnecessarily restricting the use of metals in architecture, buildings and construction.


Support and funding was provided by the Copper Development Association Inc. (CDA) and the International Copper Association (ICA). In addition, the State of Connecticut Department of Environmental Protection (DEP) provided funding for the acute toxicity testing. We would like to thank Dale Peters, Dan Sternthal, Ken Geremia, and Ray Arnold from the CDA: Chris Lee from the ICA: Tom Morrissey and Lee Dunbar from the DEP: Robert Carlely, Christopher Perkins, Mark Groszek, Elizabeth Fumal, Deb Thompsen, Susan Beres, and Michael Trahiotis from the University of Connecticut Environmental Research Institute; and Manos Anagnostou from the University of Connecticut Department of Civil and Environmental Engineering for their advice in the planning and execution of the project.