k0ua
Epic Contributor
Here is something I would try.. I cannot guarantee it would work, but it would not be much trouble to try. Get a piece of brake line about 2 foot long, and drop it on top of the 'gravel column" This is to serve as "makup air" conduit. then take your hands and cup over the 3/4 pipe with the regular vacuum hose and try to continue to suck out the gravel. I believe the brake line will let enough air down to the gravel column to create turbulence that the vacuum can then continue to suck out the gravel. Give this a try, and it would only take a few seconds to mess with it to see if it will or not. My next best bet would be the 3/4 hammer drill bit, and let it "eat" a little into the gravel and then yank it back rapidly to continue letting the spiral flutes push the materiel to the surface. Good luck and let us know how it all works out.
James K0UA
James K0UA