By Jubi Sheahan

What are the benefits of brownfield redevelopment? There are many, according to on-going research conducted by the U.S. Conference of Mayors, and the cities of Baltimore, Chicago, and Dallas-Ft. Worth, in cooperation with the U.S. Department of Commerce and the U.S. Environmental Protection Agency.

This effort, named the Clean Air/Brownfields Partnership Pilot, is intended to identify and quantify the benefits of brownfield (called infill) redevelopment. While infill development has long been attractive to local elected officials as a means to revitalize their local economies, it has only been recent that other benefits are being recognized and explored. The Pilot project, due for completion in January 2000, will identify what innovative land use strategies and policy choices are available to local officials to achieve the simultaneous goals of clean air protection and infill redevelopment in urban areas. These have been identified by the Pilot cities involved as key components of sustainable cities. The EPA and Department of Commerce have indicated their willingness to explore regulatory mechanisms that allow cities to take credit for the quantified air benefits.

The benefits of infill redevelopment have been largely intuitive to local decisionmakers for some time. The Clean Air/Brownfields Partnership Pilot has begun to actually quantify a variety of them. Notably, a recent draft report commissioned by EPA has revealed that infill redevelopment outperforms greenfield (urban fringe or suburban development) projects by a considerable margin for a number of clean air performance indicators.

Modeling Transportation Related Air Impacts

EPA's draft study entitled, The Transportation and Environmental Impacts of Infill versus Greenfield Development - A Comparative Case Study Analysis, compared key development factors for three case study areas: San Diego County; Montgomery County, Maryland; and West Palm Beach. Each case study involved a development project that could be located at an existing infill site, or an outlying area, (see Box 1). EPA's consultants applied an integrated transportation and land use (Geographic Information System - GIS) model to estimate the impacts on: transportation; infrastructure costs; environmental factors; and, more general community livability factors.

Results of the modeling indicate that the infill sites would outperform the greenfield sites in all cases, for almost all impact factors. The environmental impacts, for example, offered quantifiable benefits for a number of air quality indicators, (see Box 2).

Transportation related impacts on air quality in San Diego County would yield an overall avoidance of 4,174.2 tons per year (tpy) if the infill site was chosen instead of the greenfield site. The avoided air pollution impacts accrue from a combination of less congestion, lower average single-driver trip times, lower overall transportation energy use, and improved neighborhood "connectedness". Similar avoided emissions were estimated for the other case studies: Montgomery County - 8,678 tpy; West Palm Beach - 1,626 tpy.

Emissions Avoidance Through Land Use Planning - Criteria Pollutants

The integrated transportation - land use model provides a tool for local decisionmakers to quantify the air quality impacts of alternative project sites. The avoided air impacts can be helpful to cities that are trying to achieve attainment status as required by the Clean Air Act.

Four of the air pollutant parameters estimated from mobile transportation sources are among the criteria pollutants designated in the CAA as National Ambient Air Quality Standards. They are: carbon monoxide (CO); oxides of nitrogen (NOx); sulfur oxides (SOx); and, particulate matter (PM). Each of the infill sites offers avoided emissions for these criteria pollutants compared to the greenfield sites. One exception to this trend is for SOx in the Montgomery County case, which indicates equivalent emission levels for both infill and greenfield sites.

NOx emissions are important as a criteria pollutant, and also as a precursor of ozone, another criteria pollutant. There is a double benefit attached to reductions or avoided emissions for this pollutant.

PM emissions were also estimated to be lower for infill versus greenfield sites. The infill sites were estimated to range between 41% to 54% of the PM emissions associated with the greenfield sites.

Greenhouse Gas Advantages

Another important air quality indicator involves carbon dioxide, (CO2), often referred to as the single most important greenhouse gas pollutant. The infill sites reviewed in the study would produce roughly half of the CO2 emissions that would be generated by the greenfield sites.

The cumulative avoided emissions for this pollutant over a ten-year period would range from 15,000 to over 84,000 tons for the three case study projects. Thus, micro-scale land use decisions can have a significant impact on meso- and macro-scale air quality impacts over time.

Pieces of the Big Picture

The draft EPA study does not provide a comprehensive road map to understand the full array of development impacts. Rather, it offers insights to key components of development impacts and provides a measure of future outcomes.

Some limitations should be recognized when the model is applied. For example, not all environmental impacts (e.g., water use, water discharge, waste generation, etc.) are estimated in this particular model, although the model can be extended to measure these parameters as well. Also, the short list of air pollutants accounted for in this iteration of the model captures large volume criteria pollutant emissions, but not the small volume air toxics.

Another limitation of the model is that it does not estimate the air pollution impacts of the actual land use activities. It is limited, in this version, to the transportation related air quality impacts.

A particular advantage of the model, however, is that it estimates mobile source air emissions. Mobile sources are rapidly replacing stationary sources as the largest contributors to urban air quality impacts.

Stationary sources can, and sometimes do, emit 10, 100 or even 1,000 tpy of criteria and other air pollutants. The Clean Air Act Amendments of 1990 defines a major stationary source as a unit which emits 10 tons of a single pollutant, or 25 tons of combined pollutants. It can be stated, if granted wide liberty, that the 4,174.2 tpy avoided transportation related emissions estimated for the San Diego County infill site project could be roughly equivalent to the emissions of 1,669 stationary sources. A more conservative estimate based on criteria pollutant emissions would be units emitting 100 tpy. Thus stated, the San Diego County infill site project could be roughly equivalent to the emissions generated by 41 major stationary sources.

Continuation of the Clean Air/Brownfields Partnership Pilot

The cooperative Pilot project will continue to explore innovative strategies that are transferable to all cities, and which are intended to achieve air quality and economic development goals. Where possible, priority will be given to those tools, policies and strategies that can offer quantifiable benefits over and above what cities must currently do to satisfy federal air standards and State Implementation Plans. Both EPA and the Department of Commerce are working with the USCM and the three Pilot cities to eventually be able to offer credits and assistance to all cities that implement innovative clean air strategies that can demonstrate quantifiable air quality benefits.