While geophysical methods provide a non-invasive way of obtaining subsurface information, there is often a need to collect samples of pore fluid and measure material properties at depth. Because conventional drilling can aggravate the environmental problem by creating new pathways for contaminant flow, there has been a large effort by the U.S. Army Corps of Engineers to develop a device called the cone penetrometer [ Koester et al., 1993]. This device consists of a hollow steel rod that is pushed into the ground. When the rod is extracted, the resulting hole is filled with grout. Instrumentation records several parameters related to difficulty of insertion, formation pore pressure, and electrical resistivity. These data can be interpreted to obtain information about subsurface geology [ Puppala et al., 1993]. Several groups are developing instruments to be used with the probe to make in situ measurements.