Employee was replacing 2 of 5 pieces of 3""conduit that were in an 18"" ditch.The ditch was extremely wet.The conduit had 3-4"" gaps between each piece. While stepping on the conduit to climb out of the ditch the employee's foot slipped between conduit twisting right knee.Employee tore his miniscus and will be having surgery on 11/18/04 which will be his first day off.