I suspect it's too late for the original poster, but for anyone else digging a trench it's wise to drop in some PVC pipe or ducting, with a few strings run through them. You can then pull through whatever cables you need afterwards: second Cat5e? Not a problem. Fibre run in the future when 10gbit holographic video conferencing is the order of the day? No need to reach for the shovel.
If you felt especially cheeky, you could then run standard Cat5e through the tube: if it fails, you simply draw another through.