This report presents the concepts of design value and expected number of exceedances (of the 120 ppb standard) as defined by the U.S. Environmental Protection Agency (EPA) for a single monitoring site and extends the concepts to a network of sites describing conditions throughout an extended urban area. Using those definitions, methods are described for calculating values from observed data. The methods apply nonlinear interpolation and Monte Carlo simulations (based on empirically derived conditional-probability distributions) to locate areas where the greatest numbers of exceedances and highest design values are expected and to calculate the values in those areas. The methods were applied to an extensive data base collected during special monitoring programs in four different urban areas: Houston, Los Angeles, Philadelphia, and St. Louis. The appendixes to the report provide all the necessary instructions (including computer programs) for applying the methods. The instructions encompass: Acquisition, screening, and preprocessing of data. Application of methodologies and computer programs for estimating design values and number of exceedances. Determination of the origins and concentrations of background ozone entering the city. Design of supplemental monitoring programs.
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