Soggy yard from neighbors leaking pipe

Our backyard is a soggy mess, we discovered water bubbling out of the ground. We now realize it is the neighbors sump pump and the pipe runs across our backyard. This runs through a good portion of our yard. We both back to township property and he even has a ditch area that could handle this water. The distance is at least 2 or 3 times greater to go through my yard. I was not aware of this pipe until it started leaking and there is a ton of water bubbling out. We have asked him to remove this from our property and run it straight back to the woods behind his home(into the ditch would be a no brainer). We have only lived here a little over three years and he says he isn't sure when he found out the pipe was on our land. Not believing much he has to say since he didn't come clean when we first found the leak. He says we should pay half to move the pipe since our trees caused the problem with the pipe - never mind that the pipe is in my backyard. It doesn't even make sense to me. The pipe should not even be in my yard.
Help.

You likely can cut and block that pipe if you need to.

But discuss it first and try to fins some solution. He has no right to have that pipe on your land unless it is provided for in the deeds.

Thanks for your reply. I guess my next question would be can he sue me for damages if his basement floods. When we first talked to him about fixing the problem he stated that the pipe was on my land so it was my problem. My answer at that point was the pipe could be sealed at our property line but I wouldn't want to do that because his basement would flood. A few days later he phoned with the notion that he would sue for damages if his basement flooded. I do not want to take drastic measures. I even gave him the name of my landscape guy. I could send a registered letter with our intent to seal the pipe after a certain date (hopefully giving him time to get it moved). Would this also give us legal protection?
Thanks