original_query: What were some mishaps that occurred during the construction of the Severn Tunnel?
query: What were some mishaps that occurred during the construction of the Severn Tunnel?
answer: During construction, significant flooding occurred from "The Great Spring" in 1879 and again in 1883.  There was also an unintentional breakthrough into the Salmon Pool on the English side, leading to high water pressure that pushed out some bricks from the tunnel lining in 1885.