Ozone Article

Clearing the Air:

Bringing South Carolina’s Ozone Problem under Control

John Gardner

Introduction

In April 2004, five South Carolina counties were designated as nonattainment areas for ground-level ozone under the Clean Air Act. The designation was a wake-up call, serving notice that the state's largest metro areas not only are experiencing rapid growth and developing big-city traffic problems, but also the air quality problems that go along with congested highways.

The U.S. Environmental Protection Agency (EPA) designates an area as nonattainment if the air quality monitoring system for the area shows violations of the National Ambient Air Quality Standard (NAAQS) for ozone over a three-year period. All of Anderson, Greenville, and Spartanburg counties comprise a single Upstate nonattainment area, while the urbanized portions of Richland, Lexington, and York counties also were declared nonattainment areas.

The good news: The effective dates of the nonattainment designation and its regulatory consequences have been deferred in the Upstate and Midlands areas. This deferment is possible because both regions elected to enter into an Early Action Compact with EPA and the state's Department of Health and Environmental Control (DHEC). In York County, the Rock Hill urbanized area became ineligible to participate in the Early Action Compacts, because it is now combined with the Charlotte metro area for air quality planning purposes. The Charlotte region has had ozone problems for too long to be eligible to participate in the Early Action process.

The public benefit of Early Action Compacts is that they require communities to develop plans to reduce air pollution at least two years earlier than required by the Clean Air Act. The plans must include specific criteria and milestones for reducing ozone-forming emissions, and as long as the participating counties meet these milestones, the effective date of ozone nonattainment designation continues to be deferred. If air quality monitoring shows that the areas meet the ozone standards by December 2007, the nonattainment designation is withdrawn.

The Early Action Compacts (EACs) already have produced important benefits for the Midlands and Upstate regions, as a result of the cooperative efforts of government and industry to cut emissions as quickly as possible. South Carolina is the only state in the U.S. where 95% of the counties signed and are implementing the EACs. Most of the counties are at no risk of becoming nonattainment areas, but their participation helps reduce the regional emissions that may make the difference between attainment and nonattainment for the Midlands and Upstate. DHEC management and staff has worked very effectively through the EAC process to build relationships that will help keep the Upstate and Midlands regions -- and the entire state -- focused on maintaining clean air beyond 2007. Better communications among local, state and federal transportation and air quality agencies is helping to clarify the relationships among transportation planning, regional growth, and air pollution. And of course, the regulatory burdens on industry and government that accompany nonattainment designation will be avoided if the EACs succeed.

Business and industry groups worry that nonattainment status will hinder economic development efforts, as new or expanding industries are subjected to more stringent air pollution permitting requirements through the New Source Review process. Transportation interests fret that federal highway improvement funds will be lost. And while these are valid concerns, there is no evidence that nonattainment designation has negatively impacted growth in neighboring regions. Atlanta and Charlotte were designated nonattainment areas years ago, and designation has had little discernable impact on growth and development or the pace of transportation improvements. Both regions have continued growing rapidly, and have continued making major investments in both highways and mass transit facilities. One clear affect on transportation planning has been that both Charlotte and Atlanta have focused greater attention on developing more effective regional transit systems. Business and government leaders in both areas now are quick to point out that their regions waited far too long to begin planning seriously for mass transit.

Why the Ozone Standard Was Lowered

Nonattainment designation has created the misconception that air quality is deteriorating in South Carolina, when what really has happened is that EPA has implemented a stricter air quality standard. Prior to 1999, ground-level ozone concentrations were limited to 12 parts per billion, measured hourly. But EPA's research into ozone's health effects was showing that the duration of exposure to ozone also was a critical factor. In response, the new standard limits ozone to just 8 parts per billion, measured as an average of the eight highest consecutive hourly readings each day. The result of the tighter "eight-hour standard" is that many areas that attained the old "one-hour" standard now exceed the new standard.

An Ozone Primer

Ozone is made up of three oxygen atoms (O₃) instead of the usual two atoms, and is a powerful oxidant. It is commonly used in water purification and industrial purification processes, where it works by giving up one oxygen atom to oxidize bacteria and contaminants. In the stratosphere, ozone shields the earth from ultraviolet radiation. But at ground level, human exposure to high levels of ozone causes respiratory problems, decreases lung capacity, and aggravates asthma. Repeated short-term ozone damage to children's developing lungs may lead to reduced lung function in adulthood, according to EPA. In adults, ozone exposure may accelerate the natural decline in lung function that occurs with aging.

Ground-level ozone is not directly emitted from smokestacks or tailpipes, but is formed when oxides of nitrogen (NOx) chemically react with volatile organic compounds (VOC) in heat and sunlight. Automobiles, trucks, buses, and construction equipment are the largest producers of NOx in urban areas, contributing about half of all emissions. Electric generating plants and industrial operations add about a third, with the balance being produced by home furnaces, water heaters, lawn mowers, open burning, and other miscellaneous combustion.

Human activities, however, are only partly responsible for the VOCs in the biosphere. Trees and plants, through transpiration, produce about half of the total VOCs in South Carolina's air. The isoprenes[1] that your back yard oak trees emit may smell much better than the exhaust from a neighbor's rusty old pickup truck, but they combine with NOx to form ozone just as effectively.

This is not to suggest that cutting down trees is part of the solution to the ozone problem. Even if we eliminated most man-made VOCs, we would likely still have an ozone problem. The key to reducing ground level ozone is to reduce NOx.

While the Upstate, Midland, and Rock Hill areas were designated as nonattainment areas in 2004, all three regions met the EPA ozone standard in 2005. One reason was the frequent rains that fell across the state during the last three summers. Rain washes ozone-forming pollutants out of the atmosphere, and thunderstorms cause mixing among the upper and lower layers of the atmosphere, which also curbs ozone formation. But another reason for the lowered ozone levels is that clean air efforts are producing results.

DHEC publishes the most recent ten years of ozone monitoring data on its Website. The data clearly reveal that ozone levels are highest in drought years. The dry summers of 2000, 2001, and 2002 produced high ozone levels, which were responsible for the 2004 nonattainment designations. Frequent thunderstorms characterized the summers of 2003, 2004, and 2005 -- at least until mid-August of 2005. Only one annual exceedance of the ozone standard occurred in these past three years, in northeast Richland County, and by just two parts per billion. Statewide, all air quality monitors now meet the NAAQS for ozone, which is computed as a three-year average of annual levels.

While ozone levels generally reflect weather patterns, there is a trend toward lower readings in the last ten years. A statewide drought was declared in July 1998, and continued into the spring of 2001. During this three-year period of moderate drought conditions, the annual ozone readings at the four most problematic sites in the state -- North Spartanburg and Powdersville in the Upstate, and Parklane and Sandhill in the Midlands -- peaked in 1998 at between 96 parts per billion (ppb) and 102 ppb, averaging 98 ppb. In June 2002, a severe drought was declared, and upgraded to extreme drought in August. At the four monitoring stations listed above, 2002 ozone levels ranged between 84 and 93 ppb, averaging 91 ppb. The past three years have had the lowest ozone levels of the last ten years, ranging in 2005 from 82 to 86 ppb at the four worst Midlands and Upstate locations, and averaging just 83 ppb.

Table—Ozone Monitoring Data for the Upstate and Midlands Areas

Parts per million

Year	Powdersville	Parklane	Sandhill	N. Spartanburg	Average
1993	0.090	0.089	0.094	0.081	0.089
1994	0.087	0.082	0.085	0.083	0.084
1995	0.093	0.080	0.081	0.086	0.085
1996	0.086	0.082	0.079	0.086	0.083
1997	0.086	0.086	0.082	0.088	0.086
1998	0.102	0.098	0.096	0.096	0.098
1999	0.099	0.094	0.093	0.100	0.097
2000	0.084	0.096	0.097	0.089	0.092
2001	0.088	0.082	0.091	0.090	0.088
2002	0.093	0.084	0.093	0.093	0.091
2003	0.078	0.075	0.083	0.079	0.079
2004	0.076	0.082	0.082	0.082	0.081
2005	0.082	0.082	0.086	0.082	0.083

Source: S.C. Department of Health and Environmental Control, Bureau of Air Quality

Progress to Date

Both the Upstate and Midlands can credit our neighbors to the southeast for helping clean up South Carolina’s air. Atlanta, with the nation’s longest average commutes and some of the most congested travel conditions in the country, is finally showing some improvement in its notoriously bad air quality. Cleaner air in Atlanta means cleaner air in South Carolina, because ozone-forming pollutants can travel hundreds of miles on wind currents, and typically, the Palmetto State is “downwind” of Atlanta in the summer. The windborne transport of NOx is almost surely the reason that air monitors in some rural places like Due West in Abbeville County -- which produce very little NOx locally -- have teetered on the brink of nonattainment in recent years.

Several initiatives are already helping to clean up the air in the Midlands and the Upstate. Upgraded boilers at Duke Power's Lee Steam Plant will cut NOx produced by electricity generation by 850 tons per year at that facility. The Transcontinental Gas Pipeline Corporation (TransCo) natural gas pipeline through the Upstate uses massive internal combustion engines to operate compressors, which maintain pressure to move natural gas through the pipeline. TransCo will complete upgrades to the pipeline's compressors in December 2005 that will lower NOx emissions by 67%. In the Midlands, SCE&G's Wateree electric generating plant will install upgrades to reduce NOx emissions, and International Paper has agreed to 1,000 tons per year reduction in permitted emissions.

Statewide, DHEC has implemented a statewide “Control of NOx" regulation and an open burning regulation. The Control of NOx rule requires use of Best Available Control Technology (BACT) on all stationary sources of NOx, and applies even to small sources -- less than 100 tons per year -- such as industrial boilers that are normally unregulated. The open burning rules eliminate burning of household garbage and commercial construction debris, and prohibit burning of residential construction debris during ozone season.

National Initiatives are Critical

The largest stationary sources of NOx emissions are coal-fired power plants. Many of these plants, built before passage of the Clean Air Act (CAA), were exempt from CAA emissions standards. But after several northeastern states convinced EPA that emissions from some of these plants in the southeast were hindering their efforts to improve air quality, EPA required new NOx controls to be installed on these older coal-fired plants, including those in South Carolina and all of our nearest neighbors.

Cleaning up the emissions from these coal plants will play a big role in reducing ozone levels across the southeast. It turns out that tall smokestacks actually work as intended: they disperse emissions over long distances. Some of the NOx that's combining with VOCs on South Carolina’s hot August afternoons probably came from a smokestack in the next state, so reducing the NOx coming from out-of-state smokestacks will reduce ozone levels here.

The biggest player in the NOx game, however, is automobiles and trucks. To get the emissions reductions needed from highway vehicles, EPA is regulating both vehicles and fuels to produce dramatically lower emissions, through the Tier II/Low Sulfur Fuels program. On the vehicle side, the Tier II emission control requirements that became effective in 2004 will reduce VOC and NOx emissions by about 60% compared to the Tier I standards. Beginning in 2007, the heavy-duty diesel engines in tractor-trailer trucks also will produce only about 30% of the NOx emissions of older models.

The key to achieving these vehicle emission reductions is reducing sulfur in gasoline and diesel fuel to a fraction of previous levels. High-sulfur fuels produce sulfur oxides (SOx) that limit the effectiveness of catalytic converters, and would clog the higher-efficiency catalytic converters required to meet the strict emission standards on Tier II vehicles and 2007 trucks. Low-sulfur fuel will have 15 ppm of sulfur, while the old standards allowed up to 500 ppm.

EPA expects that, for most “marginal” ozone nonattainment areas like the Midlands and Upstate, just the new power plant controls and the Tier II/Low Sulfur Fuels program will reduce emissions enough to attain the 8-hour ozone standard. Low-sulfur fuel also will help reduce particulate emissions, which have been a concern in parts of the Upstate and the Midlands, although neither area has been designated nonattainment for particulate matter.

Smart Highways

One innovative component of the Early Action process in South Carolina is an analysis of transportation emissions called "Smart Highways." The technical analysis for Smart Highways is essentially the same as that required for the “transportation conformity” determinations that nonattainment areas must make in order to continue funding most highway projects. In general terms, the Smart Highways analysis, like a Transportation Conformity analysis, shows how planned transportation projects will affect transportation emissions. A regional travel demand model is used to predict vehicle miles of travel and average speeds on each class of roadways -- freeways, arterials, and collectors -- in the region. EPA’s emissions model then provides per-mile emissions estimates for each class of roadways based on average speeds, and these emission factors are multiplied by the predicted vehicle miles to estimate total emissions from on-road vehicles.

The long-range transportation plans for the Upstate and Midlands were analyzed to estimate and predict the emissions from the metropolitan highway systems in 2000, 2002, 2007, and 2025. For the Greenville area, vehicle miles of travel are predicted to increase by 57% through 2025, while increased traffic congestion will reduce average speed on the regions roads by 16%. Despite these factors, EPA’s emissions model predicts that NOx emissions will decline by 78%, while VOC emissions will decline by 62%. Similar results are predicted for the rest of the Upstate and the Midlands.

The emissions reductions predicted by the Smart Highways analyses are in line with the emissions reductions predicted in other mid-size cities across the country. The dramatic declines are produced almost entirely by EPA’s low-sulfur fuel requirements, Tier 2 standards for cars and light-duty trucks, and the new emissions rules for heavy-duty diesel trucks.

Maintaining Clean Air

Reduced emissions from cars and trucks, along with cleaner electric power plants, is expected to put the Upstate and Midlands into attainment with the 8-hour ozone standard in 2007, but with little margin for error. And while EPA’s emissions models indicate that tighter vehicle emissions standards will produce huge reductions in highway-related air pollution, if the EPA models turn out to be overly optimistic, air quality may not improve as much or as fast as predicted. The nonattainment threat may not easily go away.

The most difficult long-term challenge for reducing emissions and energy consumption in southeastern cities is regional sprawl. In both the Upstate and the Midlands, subdivisions are exploding across the region, with little or no discernable pattern. While individual developments usually are carefully planned, no overarching structural plan exists to guide development of the regions.

Sprawl happens because most people choose houses on large lots in suburban or semi-rural settings over small lots or townhouses in urban settings, when all else is equal. As a result, semi-rural areas at the urban fringe continue to be transformed, as subdivisions multiply and strip malls move in. Soon, the people who moved "to the country" are surrounded by the traffic-choked suburbia they wanted to escape.

Changing this entrenched sprawl development pattern will not be easy. But increasingly, people say they prefer walkable communities over those which force us to drive everywhere. As local leaders refocus development efforts on downtowns, more people are choosing urban condos, townhouses, and small-lot traditional urban neighborhoods over large houses on a half-acre of former cornfield. More of us are trading an active urban neighborhood for suburban isolation, a 10-minute walk to work for a grinding half-hour freeway commute, and a short walk to a local deli for idling at the drive-through window.

Better planning will produce more livable cities, reduce energy consumption, and improve air quality. The key ingredients include well-developed street networks, with local street connections among subdivisions, schools and neighborhood shopping areas; management of driveway access to regional highways, so they don't become choked with local trips to hamburger stands and super stores; complete networks of sidewalks and bike lanes; smaller schools that are integrated with the surrounding neighborhoods; convenient local bus services feeding regional light rail transit or bus rapid transit networks; and “walkable” commercial centers built around transit stations.

Most readers have observed the sprawl development process, and have seen the results. South Carolina's largest urban regions are still in a position to choose to avoid the mistakes made by cities like Charlotte and Atlanta, to build regions that are efficient, to develop transportation choices and alternatives to driving alone, to begin planning and building “walkable” communities with rational patterns instead of continuing to spread fragmented subdivisions and strip malls across the landscape. Choosing business as usual will replicate Charlotte's and Atlanta's traffic problems -- and perhaps their air quality problems -- in the Midlands and Upstate. Choosing to change will require vision and leadership.[2]

About the Author

John Gardner is the senior transportation planner for the Greenville County Planning Commission. He previously served as the chief of statewide planning with the South Carolina Department of Transportation, Office of Planning. He holds a bachelor's degree in political science from Furman University, a master's degree in city and regional planning from the University of North Carolina, and is a member of the American Institute of Certified Planners. He has 18 years of experience in multimodal transportation planning and operations, and his work includes university campus transportation planning, transit system planning and management, travel demand forecasting, and air quality planning.