Multimedia Chemical Fate Model for Environmental Dredging

Abstract

Dredging the bed-sediment of rivers, lakes, estuaries, and harbors is a process of remediating contaminated sites. Whether used alone or in conjunction with in situ capping or natural recovery, its application results in the loss of contaminants to the surroundings. A steady-state multimedia box model has been developed consisting of a dredge element that initiates chemical release in a flowing stream and an algorithm for residue transport to air, water, and sediment, both with and without silt curtain containment. The model quantifies these losses and, commencing with the original in-place contaminant mass, determines the quantity targeted for dredging and the quantity “delivered to shore.” The latter is a measure of the efficiency of the dredging operation. The model was developed from experience gained studying the effectiveness of environmental dredging at three sites: Bayou Bonfouca (Slidell, La.), Grasse River (Massena, N.Y.), and Manistique Harbor (Manistique, Mich.). This paper describes the multimedia model theory and algorithm development and demonstrates its use in the application to the Bayou Bonfouca Superfund site, which was dredged for removal of creosote waste containing 16 polyaromatic hydrocarbons.