By Scott Kriner, Green Metal Consulting
Washington State recently announced plans for a second phase of investigation on toxic chemicals in rainwater runoff from roofs. The original project started in 2013 with the Washington state Department of Ecology receiving a grant for their work to determine if roof runoff was contributing to the pollution in the Puget Sound. Mock-ups of a variety of steep-slope and low-slope roofing systems were built near the Department of Ecology building. Those mock-ups included prepainted hot-dip galvanized, unpainted Zincalume®, and copper. In the non-metallic category asphalt shingle, tile, wood shake and membrane roof systems were also included.
Over several rain events, rainwater runoff from the surfaces of all mockups was collected and analyzed for metals and organics. Specifically, concentration of metals such as Arsenic, Cadmium, Copper, Zinc and Lead were analyzed. For organics, concentration of PAHs, Phthalates and PBDEs were analyzed.
The final report from that initial project was prepared with results of the concentrations of metals and organics for each roofing system. However, the results did not definitively indicate which, if any, of the concentrations of various items of analysis were dangerous to aquatic life in the Puget Sound.
Three years later the metal construction industry was informed that new funding had been received by the State of Washington to continue the project, with some changes. A new grant to the WA Stormwater Center at WSU Puyallup allowed the project to move into a new phase. The Roofing Industry task group was called into action with a presentation by the Stormwater Center on the recommendations for the next phase of evaluation.
The plan for 2016-2017 is to use the same roof mock-ups that were used in Phase 1 to represent aged surfaces with rainwater runoff being evaluated again. Over the course of one year, rainwater runoff will be analyzed after at least six rain events. Chemical analysis of the runoff with regard to metals and organics will once again be analyzed. More importantly, this time toxicological analysis will be done on the runoff specimens from each roof surface. Aquatic toxicity will be analyzed using the impact on Ceriodaphnia dubia for acute toxicity, Zebra fish embryos for lethal and sub-lethal toxicity and Coho salmon for acute toxicity.
This is a significant addition to the test program, compared to the initial phase in 2013. But there remain some concerns on the part of the roofing industry. For example, the new location for the roof mock-ups raises question about the difference in the environment compared to the location of Phase 1. Could the pH of the rainwater be different compared to the rainwater used in the initial project? And there are questions related to the difference in the water at the drip edge of the roof surfaces compared to the water that makes its way through the watershed before entering Puget Sound. The grant for this second phase of the runoff project may not be enough to model or calculate how (if) the concentration of metals, organics or other contaminates changes between the Stormwater Center sample and the Puget Sound through fate, transport and absorption.
We expect that the Roofing Industry task group will have meetings with the Stormwater Center throughout the sample collection and testing period. Input from the roofing industry will be included in a final report that should be issued later in 2017.