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Bay Blog: impervious surfaces


Question of the Week: How do vehicles affect water pollution?

Welcome to this week’s installment of the BayBlog Question of the Week! Each week we'll take a question submitted through the Chesapeake Bay Program website and answer it here for all to read.

This week’s question comes from Roshni, who asked, “How does water become polluted when automobiles are used for transportation?”

The most important thing to understand is that almost everything we do as residents of the Bay watershed has an effect on the Chesapeake in the long run. With the movement of people from city centers to more suburban areas, we have had to rely more on traveling by car, which has led to the creation of more hardened “impervious” surfaces such as highways and parking lots.

Transportation and the roads, parking lots and driveways that facilitate it account for 55 to 75 percent of all paving in cities and towns. These lands used to be forested, and when they are paved over, there are fewer habitats for wildlife and fewer filters for Bay-bound pollution. Transportation infrastructure has also caused the land across the Bay watershed to become more fragmented over the past few decades, making it even harder for animals to find habitat or complete their migration routes. (Learn more about forest fragmentation.)

The act of driving vehicles also emits pollution into our air. The pollution from these emissions eventually falls back to the earth and is transported by runoff and groundwater into streams and rivers.

Stormwater runoff is a massive problem due to the ever-increasing amount of paved surfaces in the Bay watershed. Instead of rainwater being filtered and absorbed into the ground, it simply runs off hardened areas into nearby streams and rivers, eventually carrying the pollution into the Chesapeake Bay. In fact, stormwater runoff is the fastest growing pollutant to the Bay.

Remember, everything we do affects the Chesapeake Bay, beginning with your local creek or stream. But every little change helps! So help the Bay by starting a carpool with your coworkers or using public transportation to lessen the number of cars on the road and the amount of pollution being released into the air during your commute.

Do you have a question about the Chesapeake Bay? Please send it to us through our web comment form. Your question might be chosen for our next BayBlog Question of the Week!


Chesapeake Bay states push Congress for tighter highway runoff controls

The governors of the six Chesapeake Bay states, the mayor of Washington, D.C., and the chair of the Chesapeake Bay Commission have submitted a letter to the U.S. Congress to include in the reauthorized Federal Surface Transportation Act a policy to reduce polluted stormwater runoff from federal highway construction and reconstruction projects.

Nationwide, roads and related infrastructure make up at least two-thirds of all paved, impervious surfaces, according to the letter. These areas promote runoff because they do not allow water to naturally soak into the ground. When it rains, pollutants from tailpipe emissions, fluid leaks, break linings and tire wear are picked up in runoff and carried to the nearest sewer or waterway.

The letter points to a 2002 study in Maryland that showed highways in the state accounted for 22 percent of nitrogen and 32 percent of phosphorus coming from urban areas. The study showed that highways and mobile sources annually contribute 36 million pounds of nitrogen that pollute Maryland’s land, air and water. By comparison, wastewater treatment plants contribute 17 million pounds of nitrogen per year.

Most federally funded highways were constructed without the stormwater runoff controls needed to protect the health of local streams, creeks and rivers. As a result, 66 percent of the waterways listed on the national Clean Water Act 303(d) list of impaired waters are polluted because of highway runoff.

Today, the green infrastructure techniques that relieve these impacts are well-known and, according to the letter, should be included in the reauthorized Federal Surface Transportation Act.

The letter was addressed to Reps. James L. Oberstar (D-MN) and John L. Mica (R-FL), who serve as chair and ranking member, respectively, of the House Committee on Transportation and Infrastructure.

For more information, read the full letter to Congress.

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