I uploaded a lot of new photos and technical research pics at the "SparkGap" link to the right under "Research and Development."
The Sparkgap wall is now reaching 7 feet high averaging 8 inches thick after mixing and pouring about a million buckets of concrete. This was a good exercise for my planned book about building Vaults from scrap and salvage but next time I think I will hire a concrete truck and do it all in one day. It was a lot of work for one person. I am completing and capping Sparkgap by the end of January if God is willing.