Dirt gives us life. But for all its contributions to human survival, it doesn't get much respect.
The old rhyme may say "dirt don't hurt," but we certainly know how to put the hurt on dirt. Whether it's in the form of industrial waste, commercial farming chemicals, or parking lot runoff, whatever gets in the ground has the potential to stay there, affecting life in the soil. Unlike air- and water-quality issues, soil pollution is generally more localized and easier to identify and clean up. Still, modern farming sterilizes the ground that we consider most valuable — that which grows our food. But the most imminent threat to the soil may be the pace at which we're covering it up with concrete and asphalt, new homes and strip malls.
Better farming through chemicals
"There are these two knives that are slightly curved, about 12 inches long, that slice through the soil and make the bed. Then a machine comes behind them and covers it with plastic," explains Brian Ward, a lab technician at Clemson's Coastal Research and Education Center on Savannah Highway. "At the same time, the knives are injecting methyl bromide into the soil. It quickly goes from a liquid form to gaseous, and basically spreads out through the soil's profile, sterilizing as it goes."
Across the nation, methyl bromide is commonly used on ground crops like tomatoes, watermelons, and strawberries, the type of things the moderately sandy soil of the Carolinas is famous for producing. As methyl bromide permeates the soil, it kills everything it encounters: weeds, pathogens, and tiny insects called nematodes that feed on roots and devastate crops.
But killing everything has its side effects. There are plenty of beneficial organisms in the soil that provide plants with the nutrients they need to grow. After sterilizing the soil, farmers then typically apply chemical fertilizers which add nutrients to the methyl bromide-treated fields.
Before the EPA limited farmers to using a mixture of 50 percent methyl bromide last year, those applying the chemical to the soil wore full-body hazmat suits and respirator masks. Though such protective gear is no longer required when using the diluted mixture, an oxygen tank is kept in the tractor. Farmers handling other commonly used agricultural chemicals like Telone still have to don full hazmat suits and masks.
At Boone Hall Farms in Mt. Pleasant, methyl bromide is used on crops like tomatoes and strawberries. Director of Agriculture Brock White says methyl bromide is highly effective as a fungicide and nematode-killer, but earthworms and soil-borne insects can return after the initial fumigation. He rotates his crops, a practice at the heart of any integrative pest management program because it prevents pest populations from building up on a particular crop from season to season.
Although the U.S. government deems methyl bromide-grown food safe for human consumption, they acknowledge its detrimental effect on the ozone layer — it has twice the allowable ozone depletion potential. An Environmental Protection Agency (EPA) ruling in 1991 mandated that all methyl bromide be phased out in stages by 2005. Annual reprieves in the last three years have extended the chemical's life, but with only 18 percent of 1991 levels allowed to be produced in 2008, stockpiles are running low and farmers are searching for cost-effective alternatives.
Clemson's Ward says they've experimented with new plastic, which keeps the methyl bromide in the soil longer before evaporating and is even more effective at sterilization. The lab is also using plastic that traps heat and moisture under it, an organic method which literally cooks pathogens out of the ground when it reaches 150 degrees Fahrenheit, but does little to control nematodes. Other methods being studied include individually grafting disease-resistant gourd roots onto melon plants and capturing cyanide-like gases from other decomposing plants like grapes and cabbage that are natural, but toxic, to pathogenic fungus and nematodes.
"Nothing can truly compare to methyl bromide as a fumigant — it's one chemical that's universally effective at doing lots of things," says Ward. "The phase-out has slowed because the alternatives are labor intensive and have been slow to develop."
Roger Francis, the lead agent for Clemson's Cooperative Extension program, regularly teaches farmers about the alternatives to expensive chemical treatments.
"One of the things we emphasize is the importance of bringing up the soil by using cover crops and putting composted organic matter back in," says Francis. "That helps reduce the farmers' dependence on chemicals."
Chemical farming is all that many farmers know. The pesticide/fungicide/fertilizer boom in the mid-20th century allowed one farmer to feed 50 people, whereas traditional practices kept that number closer to 10. But mass food production has lead directly to ozone depletion, water pollution as a result of fertilizer runoff, and the increased resistance of pests.
To alleviate those ills, Francis shows farmers which bugs are detrimental to plants and encourages them to take advantage of a growing market for organics.
"In nature you have a balance, where beneficial organisms keep the harmful ones under control, but when you kill both, you get a resurgence of the harmful ones and create a chemical-dependent cycle," says Francis. "The less chemicals you put in the soil, the less harm you do to beneficial insects. A tablespoon of healthy soil has millions of beneficial organisms, so when you increase organic matter content, you encourage them to grow. The things we teach the farmers can have a big positive impact on both the air and soil."
Although Clemson's outreach and research programs in Charleston are helping bring about changes in farming practices, Francis hesitates to say that nonpolluting methods of crop production will ever completely replace chemicals.
"Organic farming isn't going to feed the world. Conventional farming does, through technology that creates higher productivity," he says. "It's not only Americans depending on American farms to feed them — the whole world is depending on American agricultural production for food. As farmers lose some of the chemicals, they'll have to go back to sustainable practices, but I really don't know when it'll happen."
Fun with Superfund
EPA Project Manager Craig Zeller clearly gets excited when he talks about some of his dirtier cleanup jobs, like the former MacAlloy Corporation site on Shipyard Creek in North Charleston.
"We had Gatorade-green water coming out of the ground. Oh yeah! It was just funky," he exclaims. "There was this crazy wicking process in the soil — when it got cold enough and the moisture would come up to the surface, it would bring chromium with it, and you could see these green crystals forming all over the plants out there. It made it easy for us to know where to sample."
For much of the last century, the MacAlloy site smelted ferrochromium alloy, a key component of stainless steel, in plants along the Cooper River. After EPA inspectors found chromium and cadmium in the soil, along with over 80 million pounds of sludge that also contained lead, zinc, mercury, and manganese, the site became a national priority cleanup designated for the EPA's Superfund program.
Charleston County has three Superfund sites — one located at the former MacAlloy property, the others at sites previously used by Geiger (C&M Oil) on Savannah Highway and Koppers Co. Inc., across I-26 from MacAlloy on the neck of the Charleston peninsula. Since cleanup, all three spots now receive an EPA "OK" rating that states, "under current conditions at this site, potential or actual human exposures are under control."
While the MacAlloy site is once again home to industry (under more stringent regulations), the Koppers site was purchased by Magnolia Development, LLC, and is poised to become the downtown area's largest development to date. The Geiger site remains vacant.
Magnolia's 218-acre master plan includes 24 acres of parks, 4,400 housing units, 900 hotel rooms, and over 2 million square feet of office, retail, and civic space, all on top of an area that once housed a wood treatment plant where timbers were soaked in pits of the preservative creosote ("and made a stinking mess," says Zeller) and a phosphoric acid plant that manufactured early grade fertilizers.
Twenty-two thousand tons of contaminated soil were hauled from the Koppers site to a landfill in Pinewood, S.C., during the cleanup. Zeller says that apart from digging utility corridors for pipes and wires, which will require protective equipment and Tyvek suits, Magnolia won't be cutting into the existing ground surface. (Magnolia Development, LLC, declined to comment for this story due to ongoing public relations concerns with Charleston City Council.)
"It lends a degree of comfort to us (EPA) that the construction will be a net-fill project, where the entire area is going to come up about two feet," Zeller says. "Apart from that, concrete pavement makes a heck of a protective cover to mitigate the risk pathway from the soil." He says that education will be important for future residents, so they know not to dig an eight-foot hole in the ground and use the soil in their garden.
At the phosphoric acid plant, the EPA injected chemicals into the ground that reduced the toxicity of the soil and reduced the mobility of the contaminates to prevent further spreading. "We blend these magic dusts and juices with the contaminated soil," Zeller jokes. He emphasizes that when conducting risk assessments, the EPA assumes an average person is eating 50 milligrams of dirt a day.
"You've got to get this stuff in your mouth or skin to have an effect," he says. "The majority of us don't eat dirt, so there's a lot of conservatism built into the numbers."
Children playing in the yard would be an obvious concern to families living on a former Superfund site, but to gain approval for residential use, the contaminated ground would have to be well below the topsoil surface. Concerns have risen in the neighborhoods around the MacAlloy and Koppers sites before about lead in the soil poisoning children, the subject of a 1998 City Paper cover story, but subsequent EPA sampling of yards in the Rosemont neighborhood turned up nothing, even in areas occasionally flooded by Shipyard Creek.
Magnolia is owned by Cherokee Fund, an investment group that specializes in turning around environmentally blighted properties, and Zeller calls them the "varsity squad" when it comes to post-Superfund projects. The Coastal Conservation League has supported the development, encouraging it as responsible in-fill that takes pressure off the city's outlying rural areas.
"Years ago when I first heard about Magnolia and saw their slogan, 'Change Is Coming,' I looked at these people and said, 'You've got to be kidding me,'" says Zeller. "Boy, this is a big step for an area that was historically industrial. The change is here."
In addition to the three federal Superfund sites already remediated, there are 119 smaller contaminated areas and brownfields in Charleston County on the Registry of Conditional Remedies that still require cleanup. The sites include stores like the Harris Teeter on East Bay Street, Gerald's Tires on Rivers Avenue, and over a dozen operating gas stations and dry cleaners.
"Their soils do not meet EPA Region 9 residential preliminary remediation goals," explains S.C. Department of Health and Environmental Control spokesman Adam Myrick. "Very often, industrial sites remain industrial or commercial and groundwater is not used for drinking water, so we sign restrictive covenants with the property owner."
In other words, the site is deemed safe to purchase groceries or gas as it currently stands, but perhaps not to excavate and build a new home. That takes a dig-haul operation, in-fill, or "magic juices."
Paving in to growth pressure
Good soil has two properties, according to Carl Trettin, a scientist with the U.S. Department of Agriculture's Center for Forested Wetlands Research, based in Charleston. The first is the ability for water to infiltrate — healthy soil will let water drain freely with gravity. Second is the right balance of nutrients for plant growth. The Lowcountry's soil is sandier, and thus less fertile than more porous soil in the Midwest or California, but it's certainly proven suitable for a vast array of crops over the centuries. When we compact it by driving over it, building upon it, or paving it with asphalt, we render it useless.
The downtown peninsula has more pavement than open land, and the total impervious area on the Charleston Harbor watershed is nearing 15 percent. That's a cause of concern for scientists, environmental advocates, and planners mapping out the growth of our city. Impervious surfaces like roads don't absorb water. Fertilizers and automotive and industrial pollutants are picked up by the rain, where they are carried to a waterway or into unpaved soil areas that absorb increasing levels of chemicals in urban areas.
Among natural pervious surfaces, the most important places for controlling pollution in the Lowcountry are wetlands. Our sandy soil isn't as effective at absorbing pollutants as the ground is in other places, so our wetlands play catch-up. For much of the year, wetland forests are under water and have no oxygen in the soil. Trettin explains that organisms in an oxygen-free, or anaerobic environment, have different ways of breathing and metabolizing. Many require nitrogen, an element found heavily in fertilizers and runoff that can cause algal blooms in waterways. Wetlands absorb them, returning them to their natural state — after all, all chemicals were initially created from something in nature.
The growing understanding of the importance of wetlands has meant that any time a developer proposes a project that fills a wetland, opposition seems to appear. Wal-Mart learned that last month when their proposed expansion on James Island, which requires destroying 3.88 acres of wetland, was met with a petition against the plan signed by over 4,000 citizens; 200 residents attended a meeting of the Islanders for Responsible Expansion, a group that formed to oppose the plan.
James Island's Wal-Mart backs up to the wetlands, which are bordered on the other side by several home and condominium developments. It's an ecosystem surrounded by pavement.
"Isolated wetlands are very much still effective. What a wetland has the capacity to do is determined by some extent to what surrounds it," he says. "Just because it has a business on one side and a housing project on the other doesn't diminish its capacity to clean up water quality, even if the ability to provide wildlife habitat is lower. Wetlands are a natural way to mitigate runoff from impervious surfaces."
Hamilton Davis, a land use project manager with the Coastal Conservation League, stresses the importance of both urban green areas and protecting significant corridors of green space on Charleston's outskirts.
"The biggest problem with development patterns we've seen is the inefficient use of land space, where you've got a population that grew 80 percent from 1970 to 1995, while total developed land grew 380 percent," says Davis. "We generally prefer to see new development as in-fill. An urban green space is more to allow for the enjoyment of the community to get outside and interact than to protect biodiversity. But at the same time, we need to leave open large swaths of land that are capable of sustaining wildlife populations."
Davis says a project like Magnolia is exemplary of where to build, on a piece of land with no ecological benefit left to it. As we grow toward Summerville and east toward the Edisto River, however, he says it's important to leave open corridors for wildlife, especially between the Ashley River Historic District and the ACE Basin.
Charleston County recognizes the importance of green space as well. The Greenbelt Bank Board, established by the half-cent sales tax in 2004, has already protected 5,524 acres of rural land and 327 acres of urban area. Last week, the city of North Charleston purchased 139 acres along Noisette and Filbin creeks for $2.8 million, at least 120 acres of which will remain undeveloped.
Soil is resilient. Even after sterilizing a field with methyl bromide, life soon returns. Lands laid to waste by decades of harsh, under-regulated industrial practices are rebounding, with human help. Charleston is one of the fastest growing places in the nation, and with people come houses, roads, and pavement. The open soil that absorbs our waste and grows our food gets smaller every day. But unlike the scrubber in your sink that gets tossed in the trash when it gets too nasty, dirt isn't so easy to replace.