Terrain Tool Issue

I am experiencing an issue where the terrain tool is not working. I'm on a Dell Inspirion, and my game is updated. I'm on a lot where I'm trying to build housing and some amenities. The problem that I'm having is that I'm trying to build a pond, but the terrain tool is not working. I select the tool in build mode, but when I try use it, it does not work. I have tried to dig down to create the hole I need. I can hear the sound effects, but nothing happens. 

However, When I try to work on a pond that is already on a lot on which I am building, the Terrain tool works and allows me to adjust the pond or lake to what I desire.

Is this a known issue or is this a limitation of the game? I would appreciate any assistance.

Thank you,

SherylAnn BV