Hello Ken. To answer your question, I was not there during the appropriate time to see if the dam was "keyed in". The contractor had a very big dozer and a trackhoe on site but of course that doesn't mean he actually used the trackhoe for the purpose you discribed. At this point I am considering dumping granular bentonite through the water column. I have heard mixed reviews (mostly negative) regarding this application technique but it looks like the only option other than draining the pond. Any thoughts?