Detection of UXO in Underwater Sites Using Towed Array Resistivity/IP Measurements

This research has been conducted in response to the statement of need UXSON-02-04 calling for research into new techniques for locating UXO in underwater environments. Electrical methods, particularly the induced polarization response (IP), respond to metal objects. But on land, electrical methods have low productivity and require the intrusive placement of electrodes into the ground. If for no other reason, this requirement for making galvanic electrical contact with the earth would seem to preclude the use of these methods over land. Water, however, is a medium that provides good galvanic contact and therefore permits electrical methods including the dynamic measurement of resistivity and IP. Hence, in principle, there are neither safety nor productivity issues with deploying these methods should they prove useful. Induced Polarization (IP) is an electrical phenomenon associated with capacitive-like effects at interfaces between electrolytic pore fluids and solids. Media containing small amounts of metallic minerals (e.g., metallic sulfides) or clay minerals will have an associated IP response. The presence of IP associated with disseminated mineralization provides the basis for a very successful method of mineral exploration. It is well known, however, that IP responses are also associated with buried metallic culture (e.g., fences, well casing, pipes, and culverts). In mineral exploration, this cultural noise is to be avoided. In the context of the detection of UXO, however, this cultural noise is the desired target. Thus, in principle, galvanic electrical measurements, IP in particular, can be used for the detection of UXO. The original document contains color images.