The chemical fiber optic sensor is used to monitor in situ contami-
nant levels in soils (Figure 1.1). The sensor can be placed in a cone penetrometer or isolated via packers in discretely screened in-
tervals in monitoring wells.

The principle of detection for the sensor is a quantitative chemical reaction that forms visible light ab-
sorbing products on exposure to TCE. Absorption of light relative to reaction time is directly related to contaminant concentration. The measurement system has three major components: a pumping sys-
tem, an electro-optic instrument

that provides filtered light to the sensor and detects the returning transmission light, and the sensor.

Technology Needs

Current DOE policy requires char-
acterization of sites where TCE has been discharged into the soil and groundwater. Contaminated samples are currently collected and analyzed by an outside lab-
oratory. This is an expensive and time-consuming process. An al-
ternative is to use a sensor that can be put down monitoring or vadose zone wells or punched into the soil using a penetrometer type device. This allows measurements to be made continuously and at re-
latively low cost. In situ measure-
ments can also be made at am-