A contracter that I do work for is pouring a 120 ft concrete retaining wall about 4 ft high. What would you guys suggest for drainage on the backside? I was thinking weepholes every 10-15ft with 4 inch PVC and then also 4 inch drainpipe covered with gravel the length of the wall. Any suggestions? It isn't going to catch alot of water, but just the same, I would want to make sure that it doesn't have any problems.