Supplement to a hydrologic framework for the Oak Ridge Reservation, Oak Ridge, Tennessee. Summary of groundwater modeling

Abstract

The information in this report should prove useful for flow and contaminant-transport modeling of groundwater and for evaluating the alternatives for remedial action. New data on porosity and permeability have been analyzed and interpreted to produce a better understanding of the relationships between unfractured rock, low permeability intervals, and relatively permeable intervals. Specifically, the dimensions, orientations, depths, and spacings of pervious fractures have been measured or calculated; the depths and directions of subsurface flow paths (Solomon et al. 1992, pp. 3--21 to 3--23) have been corroborated with new data; fractures near the water table have been shown to have different characteristics than those at deeper levels; and the relationships between groundwater flows in fractures and flows in the continuum have been described. This is the information needed for the numerical modeling of groundwater flows. Other information in this report should result in a better understanding of spatial and temporal differences in water chemistry, including changes in contaminant concentrations. Temporal changes in groundwater chemistry have been shown to occur mostly near the water table. These changes consist of a periodic dilution of chemical constituents by recharge and a slow increase in constituent concentrations between recharge events. At discharge locations, spatial differencesmore » in groundwater chemistry are integrated by mixing. The monitoring of water chemistry in streams near contaminant sources may produce a better indication of contaminant releases and trends than do the records obtained from a few upgradient and downgradient wells.« less