thanks for the responses guys. So it seems that it is possible that the alum could be helping slow down or stop the leak.

My pond is .75 acres and yes I could see where the water was leaking out behind the dam in two different places. One place was about a 60L x 4W foot section on the west side of the pond at the bottom of the dam. The other was on the north side of the pond and was about 40L x 2W foot section at the bottom of the dam. The leaking areas were so long and wide that I could not see visible moving water but it would be standing in certain areas and the ground was real mushy. Mowing with my tractor would leave tracks that were real good indicators of where the water was coming through. The leak on the North side actually ran down my neighbors driveway and was starting to be a problem but they knew I was working on it. The leak on the West side collects in a ditch below and then runs through a pipe under the driveway mentioned above. It is the ditch that really showed the amount of water that was leaking because it collects all the water coming from the leak on the West side...not the north. The water loss was surely more than evaporation. I think it was double the evaporation rate.

Now, the pond is 3 inches below full pool which is higher than when the most water loss was observed before. Both the North and West leak areas are dry. No more water down my neighbors driveway and I can mow without seeing any tracks. I do however still see just a little bit of water in the ditch below the dam which leads me to believe that there is still just a little leak which I hope will continue to seal off.