A continuous submersible monitor using a cyclically purged electrical conductivity probe capable of long-term deployment even when buried in sand or silt has been conceived, designed, and tested. The submersible unit, which is battery-powered and has no connection to the shore-based receiver, will transmit the conductivity data via ultrasonic transmission. The unattended design life of the monitor will be 1 year. Based upon the reflection principles of high-frequency underwater acoustics, a commercial 200-kHz depth-finder system has been extensively modified and tested. Laboratory tests have indicated that the system is capable of resolving the echoes from the surface of a 1-cm-deep layer of carbon tetrachloride (CCl4) from those returning from a hard, sandy or muddy bottom. Field testing indicated that few precursors to the bottom echo return are present that might mask or interfere with the detection of an echo from a pollutant pool. Return echoes were evaluated by 16-mm motion picture photography and a computer-based comparator-counter technique has been developed for data management. Recommendations for further development and rapid deployment of the pollutant mapping system are also presented.

Bibliography: p. 47.