Hey everyone! I am new to the forum and to pond-building in general. We are looking to build about a .75 acre pond in our 2 acre back yard, but have been running into roadblocks primarily relating to a drainage plan. We are on a slope, with neighbors below us. The neighbors have declined to give us permission to use their property in any way for drainage because they have serious water problems as it is (because they live at the bottom of a hill). We've explained that a pond would probably help with their water problem by catching much of the surface water coming down the hill, but they are concerned about what could happen if the pond overflows. So, we are trying to figure out a drainage plan that does not require us to get permission from neighbors. We've been in touch with various engineers, but I thought I would ask the internet for its opinions.

It is still unclear to me whether I could just disperse any overflow throughout the backyard, or if that would require any sort of agreement with the neighbors. That would certainly be the easiest route.

We've also considered the use of a pump to run overflow uphill to the storm sewer on the road. The pond is probably 20-30' below the level of the storm sewer on the road, and the pond would be a good 300' away from the road. Presumably running a pipe from the pond to the road, with a pump that turns on when the water level hits a certain point, would be quite expensive? I also don't know how much it would cost to actually run the pump.

Anyone have any ideas?

Thanks!
MattInOP