fracture trace or lineament, or at the intersection of such linear features, will intercept a cave
Wells that were originally sited without consideration of conduit flow should be used
for monitoring only if tracing has first proven a connection from the waste management
facility to each of the monitoring wells under varying flow conditions. Domestic,
agricultural, and industrial wells are sited and installed for purposes other than ground water
monitoring. Even previously installed monitoring wells designed to detect contaminants, to
intercept contaminant plumes, or to function as upgradient monitoring wells should be
considered randomly located unless they were deliberately sited along fracture traces or
fracture trace intersections. Piezometer clusters are excellent in porous media, but will
provide relatively little information in most karst terranes. Piezometer clusters do have value
in defining the diffuse flow component of a karst aquifer, but this could lead to (1) incorrect
interpretation of subsurface flow characteristics, and (2) greatly added site characterization
expenses. Randomly located and non randomly located wells not intended for aquifer testing
or ground water tracing should be used as monitoring wells only if tracing shows a direct link
to the conduit system to be monitored. Such wells should not, however, be used as
monitoring wells for a facility above an aquifer dominated by conduit flow or diffuse flow,
unless tracer studies show that the well is downgradient from the facility to be monitored.
Tracing to Identify Monitoring Sites in Aquifers Dominated by Conduit
Ground water tracing is a well developed tool that enables catchment boundaries to be
delineated, ground water flow velocities to be estimated, areas of recharge and discharge to be
determined, and sources of pollution to be identified. Ground Water Tracers, by Davis et al.
(1985) is an EPA sponsored compendium that discusses many facets of ground water tracing.
Another good reference concerning ground water tracing is Quinlan (1990). It is important to
consult an individual who is experienced in ground water tracing, and to get approval from
the appropriate regulatory authorities before any tracer study is initiated.
A tracer should have a number of properties to be considered useful, including the
Its potential chemical and physical behavior in ground water should be
It should travel with the same velocity as the water and not interact with solid
It should be nontoxic for most uses;
It should be inexpensive;