We replaced our railroad tie border with a retaining wall near our weeping acacia and now it's in big trouble. The workers said they didn't take out many roots, but they did pile about half a foot of soil to the original tree base. This was about a week and a half ago. Today I've dug up the soil back to the original tree base depth and added some fertilizer, water and topsoil. I'm in Southern California so the drought hasn't helped. Any suggestions on how to save my tree would be much appreciated.