Copper Roof Stormwater Runoff - Corrosion And The Environment

H.T. Michels, Copper Development Association Inc.
Bryan Boulanger, Department of Civil and Environmental Engineering, University of Iowa
Nikolaos P. Nikolaidis, Department of Environmental Engineering, Technical University of Crete


A well defined watershed was utilized to determines copper concentration, speciation and aquatic toxicity in stormwater runoff. Stormwater runoff samples were collected during 16 storm events from a copper roof, and simultaneously at several other locations within the watershed, in order to better understand the sources and fate of copper. Copper concentration, pH, and hardness were measured.

Acute toxicological evaluations indicated, that although runoff was toxic at the bottom of the downspout, it exhibited no acute toxicity by the time it flowed into a stream, a state regulated waterway. Dilution, interaction with the piping materials, dissolved organic carbon and other complexing agents and debris have reduced the concentration of the potentially harmful ionic copper.

Because corrosion products may be released in stormwater, corrosion engineers should play role in establishing relevant and meaningful metals discharge criteria, which protect the environment, but do not unnecessarily restrict the use of metals.


Copper is a widely used industrial metal whose applications include electrical wiring, plumbing and air conditioning tubing and roofing. The properties of copper, which make it suitable for these applications, include high electrical and thermal conductivity, good corrosion resistance, ease of fabrication and installation, attractive appearance, ready availability, and high recyclability. Additionally, copper, which is an essential nutrient to humans and other life forms, is biostatic/biocidal to certain organisms. A common application of the latter is its antifouling properties in seawater.

The State of Connecticut Department of Environmental Protection (DEP) has found that most of the major rivers in that state exceed the copper water quality criteria several times a year, leading to concerns about the potential adverse effect of copper on aquatic life. This resulted in the Copper Development Association Inc. (CDA) and the DEP collaborating in developing a better understanding of the mobility, fate and forms of copper in an urban watershed, and the relationship between copper exceedance of regulatory limits and the lack of, or degree of, toxicity observed in freshwater systems.