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Section No 6 . <br /> Revision No 1 <br /> Date January 13, 1992 <br /> Page 54 of 55 <br /> Fnllnwinc the completion of cone penetrometer exploration at each <br /> borehole, the cone penetrometer will be withdrawn from the ground and the <br /> hole will be grouted. Grouting will be accomplished by re-entering the hole <br /> with a probe which is advanced to the total depth of the hole and then <br /> removed as grout is pumped into the probe hole Alternatively and <br /> preferably, because of recent equipment design changes, grouting will be <br /> performed concurrently with cone penetrometer withdrawal <br /> 6 10 3 Geophysical Logging <br /> Deep boreholes drilled using rotary-wash methods will be electrically <br /> logged using geophysical methods The geophysical techniques to be employed <br /> are contained within the U S Geological Survey National Handbook of <br /> Recommended Methods £or Water AMuisition (1977) The geophysical techniques <br /> to be e-played include snontaneous potential and resistivity logging <br /> Spontaneous potential (SP) is used to evaluate bed thickness, <br /> differentiate porous from non-porous materials, and evaluate water quality <br /> The SP log is a graphic plot of the small differences in voltage that develop <br /> at contact between borehole fluid, clay deposits , and water in aquifers <br /> Resistivity logging measures the electrical resistivity of a known or <br /> assumed volume of subsurface materials under the direct application of an <br /> electrical current This logging is useful in evaluating formation <br /> resistance, formation porosity, and cake resistivity, and water saturation <br /> The methods that will be used are the single point and long (72-inch) normal <br /> logs <br /> 6-54 <br />