My idea of a better remedy for leaky tunnels: A bypass tunnel. This is exactly what was done for the leaky parts of the 2.5 mile long Delaware Aqueduct 600 feet under the Hudson River between the towns of Newburgh and Wappinger. Repair cost $1 billion.

https://recordonline.com/story/news/2021/03/25/concrete-linings-delaware-aqueduct-bypass-tunnel-completed/7004863002/