Parameters necessary for groundwater or contaminant transport modeling exhibit great spatial variability within glaciofluvial aquifers due to their geologic heterogeneity. Porosity and storativity values usually vary within one order of magnitude while permeability can vary over several orders of magnitude. Contaminant migration is highly dependant on small scale variation in these parameters. Because detailed information on parameter values are difficult to obtain in subsurface aquifers, data from aquifer analog outcrops can be used to supplement aquifer data. Permeability information can be obtained with probe permeametry while other parameters can be measured by laboratory tests conducted on outcrop sediments.

The gravel pit walls at the American Aggregates plant near Richmond, Indiana contain remnant valley stream terraces of Late Wisconsinan glaciofluvial outwash. Most of the visible materials exposed in the walls are highly stratified outwash sands and gravels. Their stratigraphic framework and depositional environment make these sediments a good analog for the numerous glaciofluvial aquifers found in Ohio, Indiana and elsewhere.

Probe permeameter data showed mean permeability values of major lithofacies groups ranging from 5.60x10-2 cm/sec for the crudely bedded gravels to 2.84x10-3 cm/sec for the rippled sand units. Average LSAMP permeability values for the Richmond sediments were generally lower than permeability values obtained from pump tests in other glaciofluvial aquifers in this region. Most major lithofacies types had overall log-normal permeability distributions. Permeability variation coefficients ranged from .26 to .64. The permeability structure revealed by variogram analyses of individual transects of probe data is dependant on both the scale of the bedding structures and the sampling space interval. Porosity values from eight sediment cores taken from outcrop ranged from 25% to 41%. Specific yield values for these cores ranged from 3% to 23%. The assumed specific yield value of 20% commonly used for glaciofluvial aquifers in this region is consistent with these measured values. The disaggregation and repacking of selected cores resulted in slightly increased specific yield values for the coarse sand and gravels.

Falling head permeameter tests conducted on sediment from these cores showed permeability values ranging from 9.358x10-2 to 3.87x10-4 cm/second. Probe permeameter measurements on these same sediments produced slightly lower permeability values for the coarse sands and gravels and higher values for the finer sediments. The empirical permeability relationship developed by Hazen produced permeability estimates somewhat higher than the falling head permeameter or the LSAMP but consistent with the measured conductivity values derived from pump tests in other glaciofluvial aquifers.