Kai--The National Electric Safety Code (NESC) establishes the minimum safety requirements for electric lines. Suggest you look at IEEE Standard C2-2002 as a start. Rick Richard F. Orthen, CHMM Senior Project Manager Civil & Environmental Consultants, Inc. Four Triangle Lane, Suite 200 Export, PA 15632-9255 724/327-5200, ext. 231 <http://www.cecinc.com> www.cecinc.com