I decided to leave the other pipe in and I will put two of the rubber anti seep collars (just for a little added security) in the middle of the bank about three to four feet apart. This way I only have to dig one hole.

I am also going to use a bentonite/topsoil mix to pack all around them.
I found a bentonite website that said to mix 1 part bentonite to 5 parts soil for big holes and/or cravases.
This seems a little on the low side, but they know better than me.

Any suggestions would be appreciated, if not I will let you know how I made out when I am done