Symposium on operation of the Boulder Dam transmission line — Insulation and lightning protection

THE Boulder Dam-Los Angeles transmission system of the Bureau of Power and Light traverses country presenting a wide variation in geological and climatological conditions. Starting from practically sea-level conditions at the Los Angeles terminus, the line passes through low-lying alluvial valleys, with their accompanying fogs, through the foothill sections and across the gravelly and rocky talus slopes at the base of the San Gabriel Mountains. Passing over Cajon Pass at an elevation of 4,415 feet, the line drops gradually into the Mojave Desert area for the remainder of the 190 miles to the Boulder power plant. For those unfamiliar with this territory, it is a mingling of mountain ranges, large sloping valleys of a generally rocky character with occasional sinks or dry lakes that are flooded at two-to four-year intervals by desert storms. In this section the line varies in elevation from 800 to 4,862 feet with the general trend being between 2,000 and 3,000 feet. The average rainfall in this territory is between one and six inches per year which usually comes in one or two storms of cloudburst proportions.