Eric Tate  
Risk Assessment Proposal:
American Creosoting Site

etate@mail.utexas.edu 


Site Background
The American Creosoting site, is a former wood-treating facility that operated for about 30 years from the 1940's to the 1970's. Wood products were treated on the property using creosote, pentachlorophenol (PCP), and chromated copper arsenate. Process wastewater was discharged to adjacent drainage ditches. Previous site investigations have found site-related chemicals in areas adjacent to the site and historical drainage pathways. The site is currently surrounded by numerous residential properties. Based on concerns by EPA, I have agreed to change some basic identification details about the site. Hence, I've changed the site name, location, and dates of operation.

Source Characterization
The previous investigations have described the source fairly well. The contaminated soil and drainage ditch sediment near the site are the result of transport and re-deposition from the original waste source. Numerous soil and sediment samples were collected over a 5-week period at depths of 0 to 6 inches and 0 to 24 inches. The primary contaminants of concern were determined to be polycyclic aromatic hydrocarbons (PAHs), PCP, copper, chromium, arsenic, polychlorinated dibenzodioxins, and polychlorinated dibenzofurans.

Chemical Screening
The contaminants of concern for the risk assessment will be determined by eliminating chemicals if the constituent was not detected in any samples or the frequency of detection is below 5%. In addition, samples with concentrations below background levels will not be evaluated.

Exposure and Receptor Scenarios
Dermal contact, incidental soil ingestion, and ingestion of garden vegetables will be evaluated for residential children and adults. Dose calculations will be performed accordingly. Typically, both reasonable maximum exposure (RME) and central tendency exposure (CTE) are considered for a risk assessment. I intend to work based on the RME scenario, which is designed to be a measure of “high-end” exposure.

In Closing
At this point, I think the scope of my proposed risk assessment is a bit too ambitious to be completed in the time frame allowed by this course. As such, I'll likely eliminate certain aspects during the course of the assessment to save time. Examples of such cuts may be expanding the number of chemicals screened out and eliminating an exposure or receptor scenario.

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