Cynthia Estrop

This study examines the relationship between groundwater velocity and dissolved phase contaminant plume length on wood treating sites. The purpose of the work is to evaluate whether this relationship provides a valid method for estimating plume length.

Wood treatment industries have operated in North America for more than 100 years, producing treated products such as railway ties, utility poles and fence posts. Creosote is the oldest of the common wood preservatives. Its use dates back to the earliest wood treatment operations and it is still widely used today. At many older wood treating sites a substantial amount of creosote was spilled in the first half of the 20th century, before the advent of heightened environmental awareness and stricter regulations. The chemicals associated with creosote are a public health concern because they can be both toxic and carcinogenic. Once these chemicals dissolve into groundwater, they form mobile plumes that may extend hundreds of meters downgradient from the source.

Physical removal of plumes on wood treating sites is usually difficult and expensive. Consequently, natural biodegradation is often identified as the most practical means of cleaning up the groundwater, as long as the contaminants do not pose an unacceptable risk. This approach acknowledges that the groundwater will be contaminated for an extended period, possibly many decades. Over this period, there will be a long term requirement for groundwater monitoring.

The conclusions of this study are intended to contribute to the design of long term monitoring programs on wood treating sites. This study looked at four separate wood treating sites and compared the extent of the dissolved phase plumes at each of them. Naphthalene plumes were chosen for the comparison, as it is one of the main constituents in creosote and had the most extensive dissolved phase distribution. Simple modeling was done to evaluate the stability of the plumes studies. The result of the study shows a strong correlation between groundwater velocity and the extent of the dissolved plumes. These are still preliminary results, and as such, additional work to other sites and with other constituents is highly recommended.

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Pages: 40
Supervisor:  Anne-Marie Ryan