Jeff & Rob
A quick trip pre-monthly meet to check out what happened after the last attack and to redo if necessary. Prebeers and chips got us prepared and we headed straight down to the Black Jack choke.
Thankfully it looks like nothing has moved in the choke and the rock that we had drilled had indeed slit nicely into two. Unfortunately the bigger half was still under pressure and it was unsafe to do anything there. So we drilled it again and used some different technology this time to see what effect that would have. Big 16mm holes and stemming take a while, which feels like forever when at the pointed end of this choke!
We retreated back to a safe distance and let her go. A good pop but again no big collapse. Rubbish! I went back for a careful look, against Jeff's best advice. Great news that the air was totally clear (within 3 minutes) so the draught is obviously working well. The offending rock was completely obliterated into about 10 different chunks. However they were all still in place! The whole place was creaking and spitting rocks so i retreated to a safe distance. I prodded it with the longest scaf bar we had (only 1.5m) but nothing was budging. It must be holding up the whole hillside!
We will return with a much longer bar, although i hope it will have all collapsed by then...