Abandoned domestic, agricultural, or industrial well.
Well randomly drilled for dye injection.
To save the trouble and expense of a wasted dye test, percolation or slug tests should
be conducted at the injection point to determine if the injection point is open to the aquifer
and to see how rapidly it drains. The tracer injection point should be on, or as near as is
practicably possible to, the facility property. The use of injection sites that are not near the
facility property will most certainly be questioned by the regulatory authority because of the
possibility that the monitoring locations identified by the tracer test are not hydraulically
connected to the facility.
The detection limit for fluorescent dyes is lower than nonfluorescent dyes, therefore, in
general, less fluorescent dye is required for tracer tests (Quinlan, 1987). Although fluorescent
dyes exhibit many of the properties of an ideal tracer, a number of factors interfere with
concentration measurement. These factors include suspended sediment load, temperature, pH,
CaCO concentration, salinity, etc. (Quinlan, 1987). At the sampling point, preferably a
spring, grab samples can be taken or small pockets of nylon can be filled with activated
charcoal and suspended in the water. The dye adsorbs very strongly on to the charcoal and is
later desorbed in a lab and analyzed. To detect dyes, a filter fluorometer can be used in the
field or a spectrofluorometer can be used in the lab. For additional discussions of
ground water tracing, the reader is referred to Davis et al. (1985), and the EPA documents
Application of Dye Tracing Techniques for Determining Solute Transport Characteristics of
Ground Water in Karst Terranes (1988), and Ground Water Monitoring in Karst Terranes
(1989). In addition, Quinlan (1990) discusses the special problems of ground water
monitoring in karst terranes.
Figure 12 is a map that shows how the results of a dye tracing study can be displayed
graphically. The most important information to depict is the location of: all points where
dye was introduced (sinkholes, sinking streams, wells, etc.); all springs and wells in the area;
and those springs and wells where dye was recovered. The routes travelled by the dye are
usually shown as straight or curvilinear lines that connect the tracer injection points and the
springs. In most cases, straight lines should be used to schematically depict the routes
travelled by the dye, unless extensive data have been collected to justify the depiction of the
ground water flow paths as curvilinear lines. Line drawings of known cave systems with
hydraulically connected streams that occur between the surface introduction points and the
springs or wells where dye was recovered also are useful for such a map.
Sampling Frequency in Aquifers Dominated by Conduit Flow
Under 40 CFR Part 264 Subpart F, ground water monitoring frequency is specified by
the Regional Administrator in the facility's permit and either must at a minimum include four
samples collected semi annually during detection and compliance monitoring periods pursuant