While the swirling, iridescent patterns of oil floating on water can be beautiful, their environmental impacts can be severe. An acre (0.4 ha) of parking lot typically collects as much as 4 gallons (15 l) of oil and other hydrocarbons annually—and much of that gets washed into the stormwater system, usually making its way into our streams, rivers, and lakes. In many developed areas, stormwater runoff is the single largest source of water pollution.

Following up on our past feature on stormwater management (see

EBN

Vol. 3, No. 5), this article takes a look at the contaminants that show up in stormwater and strategies for removing them. This topic has relevance to both commercial and residential buildings—any project involving impervious surfaces that contribute to runoff.