The document addresses urban stormwater runoff pollution, particularly its impact on water bodies like Willowbrook Creek and Fanno Creek in Tigard, highlighting various pollutants such as sediments, nutrients, and heavy metals. It outlines new permit requirements aimed at managing stormwater runoff through site-specific practices and low-impact development strategies. Additionally, it discusses the challenges and costs associated with implementing green infrastructure, such as tree planting in parking lots, to mitigate runoff effects.