Benjamin Ross

Efficiency of air inlet wells in vapor extraction systems

Vapor extraction is often used to remove volatile organic chemicals from unsaturated soils. Air inlet wells, which are left open to atmospheric pressure, are commonly installed around the extraction well to accelerate the removal of volatile contaminants. We employ the method of images in radial coordinates and the principle of superposition to develop an analytical solution for calculating the amount of air drawn in by inlet wells evenly spaced around an extraction well. Field tests of proposed vapor extraction systems can be compared with this solution to help evaluate whether gas flow will permeate the entire soil or will be concentrated in localized channels.

A statistical approach to modeling transport of pollutants in ground water

The transport of pollutants in the subsurface can be affected by random geologic events. Prediction of such transport therefore requires the solution of a partial differential equation whose coefficients are random processes. A method of finding the expected (mean) values of solutions of such equations is derived. This method is used to assess the impact of fault movement and formation of breccia pipes on risk from radioactive waste disposal. Preliminary results indicate that these events, considered probabilistically, do not make a large contribution to risk.

Tidal inflow to aquifers

Where an aquifer discharges into a tidal estuary, flow can reverse at high tide. When the aquifer and estuary waters differ chemically, it is useful to know whether flow reverses and, if so, how much. For the case of a confined aquifer discharging into a tidal estuary, a formula for the ratio of inflow to outflow during one tidal cycle is derived.