Substances Detected

Relative Cost


Groundwater Monitoring Wells (wet wells)

Vapor (sniff) Wells

Dyes and Tracers

Wet wells are used to detect and determine the extent of contamination in ground-water tables.

Vapor wells are used to detect and monitor the presence of hazardous gases and vapors in the soil.

Substances with a characteristic color or other characteristics (e.g., radioactive tracers) that can be used to trace the origin of a spill.

Area-wide or local monitoring for groundwater contamination from underground storage tanks and pipelines. May be used for periodic sampling or may employ one of the sensors described above to detect leaks or spills.

Area-wide or local monitoring of the soil surrounding underground storage tanks and pipe-lines.

Area-wide monitoring of underground tanks and buried pipelines.

Any hazardous liquids which can be detected by on-site instruments or laboratory analysis.

Many different combustible and non-combustible gases and vapors.

Dye itself is detected visually or with the use of instruments.

Medium to High

Low Medium

The type, number and location of wet wells depends upon the site's hydrogeology, the direction of groundwater flow, and the type of spill containment and spill collection systems used.

The type, number and location of vapor wells depend upon the extent of the spill, the volatility of the product, and the soil characteristics. Vapor wells are subject to contamination from surface spills and cannot be used at contaminated sites.

Dye or tracer could be low in cost, but the time required to perform a study could be great. Also may require the drilling of observation wells to trace the dye of other material. Radioactive tracers require a license and approval from the Nuclear Regulatory Commission of the U.S. Department of Labor. Therefore they are generally discouraged.

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