Masters Theses

Date of Award

5-1993

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

Wayne T. Davis

Committee Members

Terry Miller, Gregory Reed

Abstract

Martin Marietta Energy Systems, Inc., manages three large installations for the Department of Energy (DOE) on the Oak Ridge Reservation (ORR): Y-12 Plant, Oak Ridge National Laboratory, and K-25 Site. The ORR is located in moderately complex terrain with a series of ridges and valleys separating the major facilities. These large and multi-faceted production and research facilities have historically evaluated air pollutant emissions independently. However, with increasing emphasis on risk-based health standards for hazardous air pollutants, it is becoming necessary to integrate the cumulative effects of emissions from each installation on all receptors around the ORR. Historic modeling on the ORR has used the Industrial Source Complex (ISC) dispersion model, a straight-line Guassian model that assumes a uniform wind field.

This study compared meteorological data at four monitoring sites typically used for dispersion modeling on the ORR. Annual joint frequency data and hourly data were compared and correlated. Parameters evaluated included wind direction, wind speed, and stability category since these parameters are used directly in dispersion models. Review of annual frequency data found significant differences in wind direction between the sites, especially when the two towers at the Y-12 Plant were compared. It appears that the Y-12 Plant East tower is highly influenced by an adjacent flow-equalization basin and valley cross- roads. The evaluation of hourly data found that wind direction varied significantly from one site to another, especially during light winds and stable conditions. During high winds and neutral conditions, wind direction data compared more favorably. Although wind speed and stability categories also showed some variation, the variations were not as significant as wind direction.

Dispersion modeling of unit releases (1 g/s) using ISC was conducted for three hypothetical emission points at the Y-12 Plant, ORNL, and K-25 Site. In addition, a unit release was also modeled for the Toxic Substance Control Act Incinerator at the K-25 Site. Each emission point was modeled using each of the four sets of meteorological data. Therefore, actual modeling results served as another tool in comparing the difference in the combined effect of all meteorological parameters.

Annual and 1-hour average concentrations were evaluated because they represent the most commonly used averaging periods when evaluating hazardous air pollutants. For all emission points, maximum annual concentration varied by approximately a factor of two when using each of the meteorological data sets. Maximum 1-hour concentration varied from less than 10 percent to 30 percent, depending upon the meteorological data used. The magnitudes of maximum concentrations did not show as significant variation as the meteorological data. However, the locations of maximum concentration showed greater variability when using the different meteorological data. Locations of annual average concentrations were most greatly affected by the primary wind directions and proximity from the source to the ORR boundary. Locations of maximum 1-hour concentrations were significantly affected by the elevation of the receptor. In only one case, did maximum 1-hour concentration occur at the receptor nearest to the source. In all cases, maximum 1-hour concentration occurred at receptors near or above the stack height.

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