THE AUTHORS ARE COMPLIMENTED ON THEIR PAPER COMPARING THE EFFECTIVENESS OF VIBROFLOTATION AND COMPACTION PILES MAKING CLEAR THAT COMPACTION PILES MUST BE SPACED CLOSER TOGETHER THAN VIBROFLOTATION POINTS TO DENSIFY SAND TO THE SAME RELATIVE DENSITY. HOWEVER, THIS IS NOT ALWAYS THE CASE EVEN FOR SIMILAR SOIL CONDITIONS. IN COMPARING THE EFFECTIVENESS OF COMPACTION PILES AND VIBROFLOTATION AS A MEANS OF COMPACTION, THREE VARIABLES HAVE TO BE CONSIDERED: RELATIVE DENSITY, SPACING, AND SIZE OF PILE AND VIBROFLOT, RATHER THAN JUST THE SPACING AND RELATIVE DENSITY. A FIGURE IS PRESENTED SHOWING A TYPICAL RELATIONSHIP BETWEEN RELATIVE DENSITY, SPACING AND SIZE OF PILE. IT IS APPARENT THAT THE SAME RELATIVE DENSITY CAN BE OBTAINED AT DIFFERENT SPACINGS, DEPENDING UPON PILE DIAMETER. SOME FIGURES PRESENTED BY THE AUTHORS INDICATE THAT BELOW A DENSITY OF 15 FEET, PENETRATION DISTANCE DECREASES WITH DEPTH; WHEREAS RELATIVE DENSITY INCREASES WITH DEPTH. ANOTHER FIGURE INDICATES THAT AS PENETRATION RESISTANCE INCREASES, RELATIVE DENSITY DECREASES. THIS IS CONTRARY TO MOST REPORTED DEPTH DATA, AND SHOULD BE ANALYZED FURTHER. THIS COULD HAVE BEEN CAUSED BY A NUMBER OF FACTORS: PARTIAL LIQUIFACTION OF SAND WHILE CONDUCTING THE PENETRATION TESTS, OVERPUSHING OF THE SAMPLER, AND RUNNING THE PENETRATION TEST BEFORE OBTAINING UNDISTRUBED SAMPLES. THE AUTHORS ALSO STATE THAT THE UPPER TEN TO FIFTEEN FEET WERE TOO DENSE TO SAMPLE WITH THE PISTON SAMPLER AND YET IT WAS SUCCESSFULLY USED AT TWENTY FEET WHERE THE SOIL WAS MOST DENSE. THE AUTHORS STATE THAT THE RESULTS OF THE CONTROL TESTING PROGRAM INDICATED THAT THE AVERAGE RELATIVE DENSITY AT THIRTEEN OF THE FIFTEEN LOCATINS EXCEEDED THE SPECIFIED MINIMUM REQUIREMENTS. HOWEVER, THE AVERAGE RELATIVE DENSITY BEFORE COMPACTION AS OBTAINED FROM THREE FIGURES, VARIES FROM 67% TO 71% WHICH IS WELL ABOVE THE SPECIFIED MINIMUM REQUIREMENT OF 65% EXCEPT UNDER FOOTINGS. AVERAGE RELATIVE DENSITY CANNOT BE USED AS A CRITERION FOR COMPACTION CONTROL ESPECIALLY INVOLVING SAFETY AGAINST LIQUIFACTION. THE AUTHORS RELIED ENTIRELY ON DENSITY RESULTS OBTAINED FROM CAREFULLY RECOVERED SAMPLES TO CHECK THE COMPACTION OF THE FILL. HOWEVER, TO MAKE THE SPECIFICATIONS MEANINGFUL DENSITIES WOULD HAVE TO BE DETERMINED TO AN ACCURACY OF ONE PERCENT WHICH IS RATHER DIFFICULT TO OBTAIN FROM IN SITU DENSITIES. REFERENCES: SAND DENSIFICATION BY PILES AND VIBROFLOTATION, CARL E. BASORE, JOSEPH BOITANO, ASCE PROC. PAPER 6892, NOVEMBER 1969