MAN OH MAN are you lucky or Blessed. That is the most dangerous NON leaking dam I have ever seen. Most do not make it through in that condition. For my two cents, if you are on a budget, I would pack it from as low as you can where the backside of the dam get solid as close to the bottom as possible, with GOOD GOOD CLAY all the way to the top and widen that particular area/line, from the bottom to the top and pack it every 6" or so with a manual tamper if you cannot afford to rent a gas model. It looks about two foot deep or so so you could easily 4 or 5 layers packed. Then you recover with dirt for the grass to grow and hope it sticks.
As you know it would most likely NOT hold for many rains like that. That is my two cents on the cheap way. Let us know how it turns out.
