I have a 1 ac. pond thats 4 years old, and its got a slump in the dam near the drain tube.

The dams is about 70 yards across and the slump is about 25 yards of that.

The spillway is on the other side of the dam and just by eying it, it looks like the slump is lower than the spillway.

The pond holds water to the bottom of the drain tube but it apears that the drain tube is sinking.

What do I need to do to repair the slump and raise the drain tube to the proper water level.
Thanks for your input.