US EPA

Coastal aquifers can be difficult to remediate because conventional pump-and-treat systems may exacerbate ground-water quality problems by inducing upward migration of denser saltwater into the freshwater zone, an occurrence commonly known as interface upconing. nterface upcoming occurs because pumping solely from the freshwater zone in a coastal aquifer causes a redistribution of the hydraulic head potentials established in the two fluids. nterface upcoming may be overcome by use of multi-level pumping-wells which consist of one well installed in the freshwater zone and.one well installed in the saltwater zone. y pumping both wells simultaneously, hydraulic head gradients can be maintained throughout the entire aturated thickness of the aquifer which will prevent any net movement of the freshwater/saltwater interface. he approach to solving the upcoming problem has been to take proven analytical equations describing the process of upcoming and modi@g these to take into account the effect of two wells pumping from a coastal aquifer, one well above the freshwater/saltwater interface and one well below the interface. he net effect should be a steady interface. est results from various sources indicate that the method proposed herein can be very useful in roughly predicting the likely response of implementing a multi-level pumping-well system prior to initiation provided the input parameters are relatively realistic and the user has a reasonable idea of what to expect from the model.

Field, M. AND M. Critchley. Multi-Level Pumping Wells As A Means For Remediating A Contaminated Coastal Aquifer. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-93/209 (NTIS PB95138301).

Project Officer: alcolm S. Field