After much deliberation, we finally decided what to do about the otters. We decided a 4' fence would be too costly and labor intensive to make, so we opted for a 1 ft, 3-wire electric fence. The fence has wires placesd 4", 8", and 12" above the ground. The middle wire is a ground, so they'll even get shocked trying to jump/climb over the top. We used 2.5' PVC pipes with 3 drill passages to thread the wires (tiny gauge for a good zap). The cost of the project was about $250 (we had the PVC already).
Picture below
http://photos-c.ak.fbcdn.net/photos-ak-sf2p/v652/198/67/798761648/n798761648_1218226_7301.jpg
