Metals Contamination in Stormwater from Common Roofing Materials

There is growing interest in the use of environmentally-sensitive construction materials as a low-cost component to stormwater management. Pollutant release has increased in recent years in correlation to increased development. A growing body of literature on the contributions of galvanized metal and wood products stormwater pollution loadings has concluded that these materials have the potential to release considerable levels of contaminants. Laboratory testing of these materials showed that a substantial "reservoir" of pollutants could be released. This earlier research was limited because the influence of wet-dry weathering and other environmental influences affecting the materials' degradation could not be investigated. The current project was designed to account for these limitations. The results for metals at days 10 and 41 of exposure show that lead levels are near background for all materials. The vinyl and plastic roofings also have no additional copper detected in the runoff, but the treated and untreated woods have runoff concentrations greater than 0.5 mg/L, even after 41 days of exposure and washoff. These samples are also being analyzed for zinc, chromium and arsenic. The ultimate goal of the project is to develop a model capable of predicting the metals' release from these materials over time.