Issue Date: December 12, 2011
Cleaning The Chesapeake
The Chesapeake Bay is the largest estuary in the U.S. and home to an estimated 3,600 plant and animal species, including more than 300 types of fish. The 64,000-sq-mile bay watershed is also home to about 17 million people and worth an estimated $1 trillion in terms of fishing, tourism, shipping, and property values.
After more than 25 years of federal, state, and local efforts to improve water quality in the Chesapeake Bay, most of the Bay and its tributaries remain impaired. Excessive amounts of nutrients—nitrogen and phosphorus—continue to enter the Bay each year, leading to algal blooms and oxygen-depleted waters, or “dead zones,” that are uninhabitable for most species.
Fish such as striped bass can be seen gulping for air at the Bay’s surface when the bottom waters are severely depleted of oxygen. And water that was once crystal clear with an abundance of seagrass and oysters has turned murky and is laden with jellyfish and scum.
State and local officials are under the gun to develop plans to reduce the amount of pollution that enters the Chesapeake Bay. The Environmental Protection Agency is requiring the plans as part of its latest effort to improve the water quality of the Bay and make it “fishable and swimmable.”
EPA has a long history of working with Washington, D.C., and the six states— Delaware, Maryland, New York, Pennsylvania, Virginia, and West Virginia—in the Chesapeake Bay watershed to clean the Bay. But each time it has set goals for reducing pollution in the Bay and its rivers, the targets have not been met. The latest attempt, prompted by numerous lawsuits and a 2009 executive order issued by President Barack Obama, “is one that has some teeth in it,” says Donald Boesch, president of the University of Maryland’s (UMD) Center for Environmental Science.
EPA used its authority under the Clean Water Act to set a “pollution diet” or total maximum daily load (TMDL) for the Chesapeake Bay. The Bay’s TMDL, which EPA finalized in late December 2010, indicates how much nitrogen, phosphorus, and sediment the six states and Washington, D.C., can contribute to the Bay each year.
Those three pollutants are thought to be responsible for the systematic decline in the Bay’s water quality. The primary sources of these pollutants are agricultural runoff, wastewater treatment plants, storm water runoff, and deposition from air pollution.
It is up to each state to work with local partners to allocate the reductions in pollution from various sources in the state to meet the requirements. Those plans are due to EPA this month.
The Bay’s TMDL limits are 185.9 million lb for nitrogen, 12.5 million lb for phosphorus, and 6.5 billion lb for sediments. These limits correspond to a 24% reduction in the total amount of nitrogen that enters the Bay each year, a 25% reduction in phosphorus, and a 20% reduction of sediments compared with current loads. The six bay states and Washington, D.C., must implement pollution control measures to meet the requirements by 2025, with at least 60% of those actions completed by 2017. They must also commit to two-year milestones, as defined in their individual plans, beginning in 2012.
To meet the requirements, reductions will need to come from all sources, including wastewater treatment plants, agriculture, and urban runoff, Boesch says. In addition, reductions in the deposition of air pollutants such as nitrogen oxides from power plants and other industries may be necessary. “It’s going to be difficult for some of the sources” to take the actions needed to achieve the TMDL, Boesch says. Sewage treatment plants have already made significant investments to reduce their nutrient loads to the Bay, he notes, but “there are big challenges ahead for agriculture and for urban storm water.”
If states fail to make progress, EPA can require additional reductions, deny discharge permits, or require permits from currently nonregulated sources. Farmers, home developers, and some states are up in arms about that possibility and the fact that EPA, not the states, is calling the shots.
Just days after EPA released the Bay’s TMDL, the American Farm Bureau Federation and its Pennsylvania affiliate sued the agency for overstepping its authority under the Clean Water Act. The farm groups argue that EPA is unlawfully micromanaging the states, which are responsible for deciding how to improve water quality in their jurisdictions while taking into account the impacts on local businesses and communities.
The groups also contend that the computer models EPA used to develop the Chesapeake Bay TMDL are seriously flawed. Those models are managed and continuously updated by the Chesapeake Bay Program, a partnership among EPA and other federal agencies; the bay states; Washington, D.C.; academic institutions; and environmental groups.
The latest Chesapeake Bay watershed model incorporates data about land use, fertilizer applications, wastewater treatment plant discharges, septic systems, air deposition, farm animal populations, weather, and other variables to predict the amounts of nutrients and sediment that enter the Bay and where the pollutants originate.
But many of the innovative practices farmers in the bay watershed are using to control nutrient runoff are not included in the models, so farmers don’t get credit for using them, the farm groups say. And further, they contend, monitoring data used in developing the models are incomplete.
Farmers are not the only ones unhappy with the models EPA uses to estimate nutrient loads into the Chesapeake Bay. Last summer, the National Association of Home Builders filed a lawsuit against EPA challenging the Bay’s TMDL.
Like farmers, home builders say EPA overstepped its authority in setting the water quality limits for the bay states. They are worried that EPA’s Bay cleanup strategy would make it more difficult to obtain permits for residential and light commercial development. Days after the home builders filed their lawsuit, Judge Sylvia H. Rambo of the U.S. District Court for the Middle District of Pennsylvania consolidated the lawsuit with the farm bureaus’ case.
On the other side of the debate are several environmental groups, including the Chesapeake Bay Foundation and municipal clean water associations, which filed a motion last May to intervene in the farm bureaus’ lawsuit on behalf of EPA. The groups acknowledge that the computer model isn’t perfect, but it is better than nothing, they say.
Even Congress has gotten in on the action. Last month, a subcommittee of the House of Representatives Agriculture Committee held a hearing to examine the social and economic impacts of EPA’s Chesapeake Bay cleanup plan on rural communities surrounding the bay. Lawmakers questioned why EPA didn’t conduct a cost-benefit analysis before releasing the pollution limits, and they criticized the agency for using a flawed model.
EPA Region 3 Administrator Shawn M. Garvin testified that EPA is working on a cost-benefit analysis of the Bay’s TMDL with the U.S. Department of Agriculture (USDA) and the bay states. The results are expected in mid-2012, he said. Lawmakers promised to hold another hearing to assess the cost-benefit analysis when it is complete.
Garvin also defended the computer model EPA used to develop the pollution limits, but he acknowledged that it was developed at the larger, basinwide scale and may not be as accurate at the county level. He said the biggest problem with the model, however, is the lack of monitoring data.
With little data on nutrients in farm runoff, it is unclear how well conservation methods are working to reduce nutrients entering the Bay. As a result, the model does not account for many of those methods, Garvin said. EPA is working with the bay states and USDA to refine the model so that farmers get credit for such efforts, he noted.
The model does take into account some of the practices to reduce nutrients in farm runoff. But many of those practices aren’t effective, particularly at reducing phosphorus loads, says Joshua McGrath, an assistant professor in the department of evironmental science and technology at UMD College Park.
McGrath suggests that EPA throw out the bay model and start over. “The model was developed around a point-source paradigm,” he says. Point sources are discharges that come out of a pipe and can be controlled and measured, such as those from wastewater treatment plants. But farms are not point sources and should not be modeled as if they were, McGrath contends.
The model is plagued with similar problems in predicting how much nutrient and sediment pollution is entering the Bay from storm water runoff in developed areas. Urban and suburban development can contribute significant amounts of pollution to the Bay, but without actual data it is hard to say how much. Developers are implementing practices to deter some of the runoff from urban developments, but the current model does not give them credit for many of those practices.
The model also does not fully account for the role of wetlands and forests near streams in trapping pollutants before they reach the Bay, even though some research suggests such reductions can be significant. “Wetlands are very effective at trapping nitrogen and sediment,” says Thomas E. Jordan, a senior scientist who runs the nutrient lab at the Smithsonian Environmental Research Center (SERC) in Edgewater, Md.
At a stream that meanders through the SERC property and feeds into Maryland’s Rhode River, Jordan and colleagues collected about 15 years of nutrient and sediment data before a family of beavers moved in. The beavers built a dam that created a wetland upstream of the monitoring station around 1990. By comparing the data before and after the beavers moved in, the researchers discovered that wetlands do a good job of trapping nitrate and sediment.
But a lot of forests and wetlands have disappeared in the bay watershed. According to the Chesapeake Bay Foundation, the Bay has lost half of its forested shorelines and more than half of its wetlands since the early 1600s.
As scientists refine the bay model to better predict sources of pollution, other people are studying the effects of the pollution and looking for signs of improvement.
“We’ve really altered the watershed,” says Denise L. Breitburg, a senior scientist who heads the marine and estuarine ecology lab at SERC. “Way more sediment comes off of farms, cleared land, and places where there is construction than a forested area,” she notes.
Breitburg studies the effects of pollution in the Bay on fish, jellyfish, and oysters. Sediment is particularly problematic for restoring oyster beds in the Chesapeake Bay, she says. “Oyster larvae need to settle onto oyster shells in order to grow and form oyster reefs. They don’t just settle in the mud,” she notes. “If you have a fairly thick layer of sediment covering the shells, even if the adults can manage to keep clear, you don’t have any clean substrate for the larvae to settle on.”
But Breitburg is even more concerned about the effects of low levels of dissolved oxygen. “Because the oysters are so close to the bottom where oxygen concentrations tend to be lower,” they become more prone to disease, she tells C&EN.
Unlike oysters, which are stuck in one place, mobile species, such as fish and jellyfish, can move to more oxygenated waters. But interestingly, Breitburg says, jellyfish are much more tolerant of low oxygen than fish that are at the same level in the food chain. “By creating these low-oxygen areas in the Bay, we are essentially creating habitat that is suitable for jellies and not suitable for finfish,” she says.
Low levels of dissolved oxygen have affected the distribution and health of many fish species, but “the declines in our fisheries species have been because of overfishing, not because of low oxygen,” Breitburg notes. More than 500 million lb of seafood is harvested from the Bay every year.
“We have turned what is an amazing natural resource, the equivalent of one of our national parks but underwater, into a poorly managed agricultural system,” Breitburg says. “It still produces protein, it still produces fish, but we’ve really destroyed it as a healthy ecosystem.”
Many people are frustrated by the lack of progress made over the past 25 years to clean the Bay, but the news hasn’t been all bad. A close inspection of some of the data shows a few signs that restoration efforts are making a difference.
In a number of rivers, including Pennsylvania’s Susquehanna, Maryland’s Patuxent, and the Potomac, nutrient concentrations are in a downward trend, says Walter R. Boynton, an ecologist with UMD’s Chesapeake Biological Laboratory in Solomons, Md. The reason for the trend is unclear, but it could be related to decreases in atmospheric nitrogen deposition that are due to reductions in nitrogen oxide emissions from coal-fired power plants, he says.
A recent study by researchers at the UMD Center for Environmental Science and Johns Hopkins University also suggests that the health of the Bay is improving. The paper, published in last month’s issue of the journal Estuaries & Coasts (DOI: 10.1007/s12237-011-9413-7), examined 60 years of data and concluded that the average size of the Bay’s late-summer dead zone has been shrinking since the 1980s. The researchers attributed the decrease to reductions of nutrients to the Susquehanna River and other sources that affect the upper Bay. “We see the study as a leading indicator of the Bay beginning to change in a very positive way,” Boesch says.
In addition, many ideas that researchers are evaluating look promising for removing nutrients. For example, McGrath has had success using filters to remove phosphorus from farm runoff, particularly legacy phosphorus that has accumulated in soil because of decades of applying poultry litter as fertilizer.
Some of the filters contain steel slag, a waste product from the steel industry that looks like gravel, and others contain gypsum from coal-fired power plants. Both materials capture phosphorus. In some cases the phosphorus-trapping material is confined in metal boxes. At other times a tractor-trailer load of it is dumped onto a perforated pipe in a ditch bed.
McGrath is also experimenting with using artificial wetlands made from recycled soda bottles to remove nutrient pollution, and he is looking forward to a prototype of a dry-manure injector this month from engineers at USDA’s Agricultural Research Service. The equipment will inject poultry litter into the soil rather than applying it onto the surface. He is also excited about a technique called variable-rate nitrogen application, which uses an optical sensor to determine how much nitrogen a crop needs and varies the nitrogen application rate across the field in real time.
The way McGrath sees it, reducing nutrient and sediment pollution into the Bay “is going to cost farmers money one way or another. So they might as well spend money on something that actually benefits water quality.”
Other people are also optimistic that the health of the Bay is improving, but they caution that much more work is needed. “When we see some limited signs of restoration, it is worth getting excited about. They are good news,” Boynton says. But, he notes, “there is a huge amount left to be done.”
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