Step 15. Lightning Protection System
The intensity of the lightning storm that occurs in the 24-hours after a large impact may be beyond anything experienced during the history of mankind. Lightning strikes present a danger even to those sheltered underground. For this reason, it is advisable to install a lightning protection system to pull the charge away from the shelter complex. The proposed design will pull and bleed off ground charge to the high point, effectively pulling lightning strikes away from the shelters. A lightning protection system should be constructed at each of the four-corners of the complex of 20 personnel shelters.
The lightning protection system shall be constructed as follows: Identify a location 30 feet from each corner of the complex of personnel shelters. Refer to the drawing. This location shall be away from the complex at a 45-degree angle. As the shelters are excavated, move the earth to this location and form a large circular mound. Once the 4 mounds have been created (one at each corner), drive a grounding rod (upside down – pointed end up) five feet into the center (highest spot) of each mound. Three feet of the grounding rod will remain exposed. Exercise care to avoid damaging the pointed end of the grounding rod. Next, for each mound mark off three locations, each precisely 20 feet from the central grounding rod. At these three locations, drive a grounding rod fully into the ground. Cut a 21-foot length of cable and separate the main strands. This will produce three AWG 4-0 aluminum cables. Strip all the insulation from each strand. Connect one side of the cable to the grounding rod driven into the ground and the other side of the cable into the upside down grounding rod located at the top of the earth mound. Use aluminum split bolts 4/0 to join the cable to the grounding rods. After connections are complete, bury the rest of the cable between the two grounding rods.
