By David A. Fahrenthold
Washington Post Staff Writer
Tuesday, November 11, 2008 11:28 AM
Development in the Potomac River's watershed means that much rainwater now bypasses natural filtering systems and washes off of roofs, parking lots and streets carrying a variety of harmful pollutants, according to a report released today.
In its second annual "State of the Nation's River" report, an environmental group called the Potomac Conservancy gave the river an overall grade of D-plus -- the same as last year's. In this report, the group focused on problems from "impervious surfaces," the concrete, asphalt and shingles that keep rainwater from seeping through roots, dead leaves and soil.
When it flows over these hard surfaces, the group said, the water turns "fast, hot and dirty," and its high speed, warm temperatures, and contamination with road grease, fertilizer and even raw sewage are all problems for the Potomac.
They recommended that governments force new developments to clean up, and that new or redeveloped projects control storm water with "green roofs," rain gardens and highway medians full of water-absorbing plants.