Modeling of a Contaminant Plume in a Tidally Influenced River Using Domenico’s Equation

Abstract

Currently, the mathematical code Modflow is widely used to simulate groundwater flow in aquifers. Due to the ease which exists today to create mathematical models through Modflow visual Interfaces, it is possible to obtain contamiant transport results which may not have much support, especially when simulating the transport of contaminants with little groundwater flow information. Domenico’s equation is an analytical solution for transport of contaminants in groundwater that can be used when not much groundwater flow information exists. The objective of this study is to model, using Domenico’s equation, a groundwater contaminant plume that discharges into a tidally influenced river. The study area was a wood treatment facility located on the bank of a river which is influenced by tides. Previous studies have found the presence of creosote in the subsurface and the formation of a groundwater plume that apparently discharges into the river. Domenico’s equation was selected to model this site because of the limited piezometric data available at the site to properly simulate the daily hydraulic gradient inversion due to the river tides. Domenico’s equation was successfully used to model this plume and reproduce the field distribution of naphthalene, benzene and 1-methyl-naphthalene. Two sources 40 minland had to be defined to properly simulate the plume behavior. It was determined through modeling that biodegradation plays an important role on the plume’s behavior. These were key issues in the conceptual model understanding of the plume at this site.