Fixing filthy beaches
If you’ve been seeing more headlines about beaches closed due to bacteria or pollution, it’s not just your imagination. On June 27, the Natural Resources Defense Council reported that U.S. ocean and Great Lakes beaches had closed for a total of 23,000 days during 2011. That’s the third-highest level of health-related closures in the report’s 22 year history.
Louisiana and Ohio had the highest rates of closure, while Delaware and New Hampshire had the lowest.
Two-thirds of the closures were blamed on high levels of fecal bacteria — a tell-tale of untreated sewage — but beaches can also be closed due to chemical pollution or toxic algae.
“American beaches are plagued by a sobering legacy of polluted stormwater, trash, chemicals, oil, animal waste … that travel from paved streets into sewers and ultimately to the beach,” said Steve Fleischli, acting director of water programs at the environmental group (disclosure: author is a member of NRDC). “When people dive into the ocean, they can get a range of waterborne illnesses, stomach flu, ear-nose-throat infections, hepatitis, neurological disorders. Senior citizens, small children, and people with weak immune systems are the most vulnerable.
“Much of this filth is preventable,” Fleischli added, calling on the Environmental Protection Agency to “improve standards for beach water quality so it does not leave beachgoers unprotected and exposed to dangerous pathogens in the water.”
Polluted water doesn’t just disappoint or sicken beachgoers; it also harms tourism and fishing, and raises hazards and treatment costs if the water body supplies drinking water.
A problematic legacy
Water pollution seems to be a water problem, but the trouble usually traces to polluted runoff from land, especially eroding farmland and land covered by waterproof (“impermeable” or “impervious”) material. In general, water seeps rather easily into land covered by natural vegetation; when rainfall strikes roofs, parking lots, streets, highways and bare farm fields, it usually ends up in the nearest surface water.
The runoff problem is particularly acute in older cities, like New York, Philadelphia and Milwaukee, where the same pipe system carries stormwater and sewage. Heavy rain can overwhelm a sewage treatment plant, forcing operators to dump untreated sewage into surface water. According to NRDC, “hundreds of billions of gallons of wastewater, which includes sewage and stormwater, is released in combined sewer overflows annually.”
Could stormwater be treated as a resource? Could it recharge the groundwater and support trees and plants that make cities more beautiful, more livable? That’s the promise of green infrastructure — a group of techniques that would replace the hard-surface, concrete-rich urban landscape with more naturalistic structures designed to save money, reduce the need for stormwater plumbing, cool cities and protect the environment.
To name two key benefits, water that infiltrates the ground usually loses the sediment, nutrients and pollutants it carries, and that water need not be conveyed in sewers.
Methods for dealing with storm water have changed radically over the last century, says James LaGro, a professor of urban and regional planning at University of Wisconsin-Madison. “At one point, we were trying to eliminate malaria [by draining wetlands to kill mosquitoes], to create more sanitary conditions in the urban environment. We solved that problem, but overcompensated.”
Jeffrey Featherstone, director of the Center for Sustainable Communities at Temple University in Philadelphia, says “50 years ago the goal was to get water off people’s property and into a stream as fast as possible. We realized that was a huge mistake that would increase flooding and water-quality problems downstream, and a better approach was needed.”
Starting around 1970, the “get-rid-of-the-water-fast” paradigm began to shift toward an approach that used detention (“stormwater”) ponds — basins that detain stormwater for 12 or 24 hours before it enters sewers.
Now, green infrastructure techniques are going a great deal further to deal with the quantity and quality problems associated with stormwater. Let’s take a look at some key elements:
Seven steps to cleaner water
The infiltration creation: Getting water belowground
Planters for city streets
Buffering the stream
Philly’s phriendly to green infrastructure
Philadelphia is one of the older cities cursed with a combined sewer system that makes releases of raw sewage into surface waters inevitable. Facing an EPA requirement to cut this pollution, the city compared the costs and benefits of the traditional “gray” infrastructure, using concrete plumbing to deliver stormwater to surface waters, to the costs of promoting infiltration and on-site water treatment with green infrastructure.
Cost projections for the decades of excavation, earth-moving and concrete work necessary for a grey-infrastructure solution exceeded $20 billion, says Jeffrey Featherstone of Temple University. Instead, using a menu of green infrastructure tactics, Philadelphia expects to spend $2.5-$3 billion to avoid 85 percent of those overflows.
“Philadelphia looked at how much it would cost to prevent 100 percent of the overflows, and although water quality obviously would improve, it would not see any other benefits” for that $20-billion plus, says Featherstone. Instead, Philly benefited from EPA flexibility that allowed the water department “to get the water into the ground, so the urban environment behaves much more like a natural environment.”
Finding a better solution to pollution “has become a pocketbook issue that is driven by regulation,” Featherstone says. Because the city is surrounded by a ring of suburbs with large impervious areas, “We have to change the landscape, not just implement stormwater control.”
Rather than store rainfall in giant concrete chambers, Featherstone says, “The city focused on a triple bottom line: the economic, social and environmental impacts of greening the city.”
Over the long term, Featherstone expects multiple benefits from greening: reducing greenhouse gases, improving the value of real estate, creating more parks and open space, and cutting the “urban heat island effect” that warms cities as much as 10° F above the countryside.
Although the techniques used to promote green infrastructure, such as levies on impervious surface area, are not always popular, especially with businesses with large parking lots, “The overall benefit of greening will far exceed the ones from the traditional, gray-infrastructure approach,” says Featherstone. “We can make the urban environment mimic a much more natural environment.”
Healing the water by healing the land
Taking the long view
The Why Files talked with Kenneth Potter, a hydrogeologist and professor of civil and environmental engineering at the University of Wisconsin-Madison, and a long-time student of techniques for dealing with stormwater, about the promise and possible pitfalls of green infrastructure.
I think it’s true that plantings can beautify a city, but in terms of dealing with flooding, green infrastructure has its biggest impact on moderate rainfalls. When the skies open up, green infrastructure can only offer a marginal improvement. No rain garden will have much effect on a 100-year flood; it will fill up, and whatever comes in goes right back out. And all of these techniques are dependent on the location, the nature of the soil, the amount of water involved, and the politics and economics of the situation. Green infrastructure is a change in how we deal with stormwater, and change is always threatening. And while these improvements can be cost-effective in the long term, they can cost more at the beginning.
Stormwater ponds are still useful, as they reduce peak runoff rates and can be designed to trap sediments. But they are not well suited for infiltrating water, and hence do not mitigate the increase in the amount of runoff caused by impervious surfaces. Stormwater ponds can also become very hot in summer and hence endanger fish when discharging during storms.
Parking lots can be equipped with bioretention systems that infiltrate runoff, trap sediment and nutrients, and actually increase infiltration above natural rates. For example, if you pave 85 percent of a site and build an effective bioretention system on the remainder, both infiltration and groundwater recharge will be increased above the natural rate. Smaller bioretention ponds — say 5 to 8 percent of the area – can maintain natural infiltration and groundwater recharge rates.
Generally, most pathogens are filtered out when water passes through the ground. Plants in a bioretention system will take up some phosphorus, but eventually phosphorus will eventually start leaking back out, so it is important to avoid fertilizing a bioretention pond. Many factors need to be considered when designing and building green infrastructure. There is no free lunch, and every system has its pitfalls and promises.
It varies. There are hot spots in Wisconsin, Minnesota and Illinois — although it’s more challenging in Chicago, because it’s flat and the soils are tight. In the Mid-Atlantic – Maryland, Pennsylvania, there’s a lot of awareness, and some in New England, Washington, Oregon, and to some extent California. We like to think we’re always progressing, but there are areas where they don’t even use detention ponds, and sometimes we are tempted to go backwards. Still, it’s pretty hard to just pass the excess water downstream. It’s an issue of fairness, of flooding, of water quality, and the health of the ecosystem.
— David J. Tenenbaum