bladder 110 is then inflated to place grout 120 under pressure during the injection step a suitable injection pipe is a standard tremie pipe having a 2 inch nominal diameter prior to the injection of grout 120 compressed air is used to flush any loose drilling materials from hole 80 and annular space 64 grout 120 is preferably injected at a pressure in the range of about 80 to about 120 psi and more preferably at a pressure of about 100 psi additional details well known in the art regarding installing pneumatic bladders prior to injection of grout can be found in britannia mine remediation 4100 level plug safety investigation plan dated december 2001 at the end of the initial phase of the injection step grout 120 has filled anchoring socket 80 the annular spaces between tensioning rod 96 and the inner wall of pipe 20 in lower section 30 and annular space 64 as shown in fig6 fig5 6 also show an upper section of rod 96 encased in a plastic pipe 130 preferably polyvinyl chloride pipe to prevent the outer surface of rod 96 from contacting grout 120 during the grout injection step in addition a plastic centering element 140 is tightened around the lower section of rod 96 within first hole 60 and is attached by nut 142 to the section of rod 96 within second hole 80 the portion of plastic centralizer 140 between first hole 60 and second hole 80 is bulged to fill the opening of hole 80 to provide centering of rod 96 during the grout injection step fig7 shows lower section 38 during the next phase of the injection step in which pneumatic bladder.