Tracing dyes have been used extensively in ground water and surface water hydrology investigation and experiments since the early 1960s. Tracing dyes may also be useful for conducting investigations of problem drinking water wells. An improper grout seal between the casing and the outer wall of the borehole, called the annular space, can allow the rapid infiltration of surface water or shallow ground water into the aquifer. When rapid infiltration occurs, the natural attenuation of microorganisms does not take place.
Wells may be dye tested when there is a question about the integrity of the annular space grout seal. Wells may also be dye tested when there is a question about the proper installation of the pitless adapter. Because the excavation made to install the pitless adapter is usually backfilled loosely with natural soil, improper installation of the pitless adapter inside and outside gaskets, or a roughly constructed hole, may provide an avenue of entry for surface water.
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