Hello! I have some experience in diy reno work inside my home, but haven't yet taken on something this big outside! I have a retaining wall behind a concrete tennis court that is unstable. It is about two feet tall and runs the full length of the tennis court. The ground around the retaining wall and tennis court is usually quite damp, and the retaining wall has begun to sink on one end! I've been unable to contact the previous owners to find out exactly how they built it. I know the tennis court was installed professionally, but I know nothing about the wall. It is made of treated wood and that is all I can see. The top course of wood in one corner is now leaning away from the tennis court. I really don't want to take the chance that it won't survive another freeze/thaw cycle. Some issues to consider: frost, poor drainage, and the fact that it is at the back of our property and not easily accessible by heavy machinery, since I am now concerned about the stability of the tennis court as well. Suggestions? Thanks!