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Stormwater runoff is just too much of a good thing

2/17/2015 | Real Estate Blog

We have a friend in Baltimore who deals with water quality issues in the Chesapeake Bay. The bay has been plagued by algae blooms and dead zones for years. Neither the Delaware River nor Delaware Bay are in the same state of crisis as the Chesapeake Bay, but Philadelphia and surrounds face the same problems that got our “sister bay” to this point.

The bay, it seems, has too much of a few good things. Large concentrations of nutrients are promoting the growth of algae. All that algae reduces the amount of sun that filters through to support underwater life. When all that algae dies, it absorbs more than its share of oxygen, depriving underwater life — including fish and plant life — of the all-important nutrient.

Phosphorous has a similar effect. An overabundance blocks sunlight and fosters algae growth. As we said, the algae growth reduces the amount of oxygen necessary to support fish, shellfish and plants.

These nutrients don’t fall from the sky, but rain and snow do. If rainwater does not evaporate or soak in when it hits the ground, it picks up a lot of the stuff humans have added to the ground and heads for the river or the nearest waterway. The same process occurs when we mow our lawns or when farmers irrigate their crops. Some of the water is treated before it’s dumped into the river or the Delaware Bay, but some of it just runs off the paved areas and enters the watershed right away.

Federal, state and local governments have been aware of the runoff issue for some time, but it is not always possible to balance the needs of, say, agricultural interests with the priorities of environmentalists. Farmers need their fertilizer or they need to raise chickens or pigs to make a living. The chemicals in the fertilizer and the nutrients from the chicken or pig waste then become part of the runoff.

Commercial and residential development pose similar problems. Rainwater cannot soak into the vast paved surfaces — roads, parking lots, etc. — so it runs off quickly to enter the stormwater drain system.

Municipalities, including Philadelphia, have developed certain rules for developers that must then be contemplated in any development plan. Some of the old ways, however, may be giving way to the new.

We’ll continue this in our next post.

Source: The Chesapeake Bay Program, “Stormwater Runoff,” accessed online Feb. 13, 2015