Conservation. Wooden manhole covers. Strength of the wooden manhole covers installed in Los Angeles County, California, is pointed out to Colonel Carl H. Reeves, superintendent of the Los Angeles County, California, Maintenance Department, by Alfred Jones, county surveyor. Treated to resist termites and decay, each wooden cover saves 500 pounds of metal. It may be manufactured without the use of extensive fabricating equipment. A War Production Board (WPB) order prohibits the use of iron and steel for manhole covers