Apparatus for establishing {TAIL ~ electrical conductivity} between {HEAD ~ a reference electrode} and soil under a pavement layer comprising: 
Apparatus for establishing { TAIL ~ electrical conductivity } between { HEAD ~ a reference electrode } and soil under a pavement layer comprising :
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH