Manhole sewer covers are typically made of cast iron and weigh approximately 100 pounds. They need to be heavy is so that when vehicles drive over them, they don't dislodge. Sewer covers provide entry to a vast underground world of water mains, sewers and power/communication lines. To contact a plumber for sewer cleaning in Santa Cruz, visit this website http://www.albertsplumbing.net/sewer-cleaning-repair