A large-scale field experiment on natural gradient transport of solutes in ground-water was conducted in the saturated zone of an unconfined sandy aquifer located at the Canadian Air Forces Base in Borden, Canada. A relatively well-defined initial condition was achieved by pulse injection to the saturated zone of known masses of two inorganic tracers and five halogenated organic solutes. By design, the organic solutes varied in mobility and potential for biotransformation. A dense, three-dimensional monitoring network of over 5000 sampling points, designed to yield representative ground-water samples without significantly altering the natural flow field, was sampled intensively over time. Over 19,900 samples were collected from the sampling points over a three-year period. The goal of the monitoring program was to accumulate a detailed set of concentration data, corresponding to well-defined points in space and time, whose accuracy and precision could be estimated through parallel quality-assurance studies. Spatial moment analysis techniques were subsequently applied to the data to obtain quantitative estimates as a function of time of each solute mass in solution, the location centers of mass of the solute pulses, and the spatial variance of the solutes' concentration distributions about the centers of mass.

Study results were supplemented with field measurements of other parameters such as water level data and laboratory determinations of the physical, chemical, and microbiological characteristics of the aquifer within the experimental zone. The overall goals of the integrated field and laboratory efforts were: 1) to identify the physical, chemical, and microbiological processes controlling transport in ground-water at the experiment site; 2) to test laboratory-scale predictions of the behavior of synthetic organic compounds can be used to predict field-scale transport; and 3) to develop a data base useful for developing and validating mathematical models of ground-water transport, especially those explicitly incorporating the effects of chemical interactions, microbiological transformations, and the spatial variability of aquifer parameters.

The Borden Site study was partially funded by the U.S. Environmental Protection Agency, and was performed as a collaboration between the Civil Engineering Department of Stanford University and the School of Earth Sciences at the University of Waterloo, Ontario, Canada.

The Borden Data Set can be manipulated with commercial database programs, spreadsheets, or graphics packages. The data set is distributed as a compressed file on a DOS formatted disk. This file contains concentration data for the seven constituents of the injected tracer solution, along with sampling information and the x,y,z coordinates of the sampling location. The Stanford University Technical Report documenting the Borden study experimental procedures (field and laboratory), monitoring results, spatial analysis, and data base format is included with the data set.

SYSTEM REQUIREMENTS

Intel 80i86 based computer, 640 Kb RAM, minimum of 550 Kb free RAM, and about 2 Mb free disk space to uncompress data.

Authors: P.V. Roberts and D.M. McKay (Stanford University)