Increasing demands on diminishing water supplies and the movement for urban areas to use more local water supplies has intensified interest in alternative water sources (e.g., roof runoff). However, lack of data on potential human health risks of these alternative water sources and treatment required to meet water quality standards has impeded use of these sources for both potable and non-potable applications. Data on pathogens in roof runoff is limited due to the need for a rigorous sampling campaign encompassing a large of number roofs in multiple regions and the complexities associated with measuring human pathogens. Your participation in this project will advance the latest science on microbial quality of roof runoff and help inform decisions regarding appropriate roof runoff use.