This is doable. Many coastal wastewater systems already have large pipes that extend miles to sea (1), and that's a rounding error compared to the many more mil

This is doable. Many coastal wastewater systems already have large pipes that extend miles to sea (1), and that's a rounding error compared to the many more miles of pipe routing sewage to the plant (2, pg A-3) (1) https://www.wateronline.com/doc/new-10-mile-long-sewage-tunnel-takes-treated-0001 https://www.wateronline.com/doc/new-10-mile-long-sewage-tunn... (2) https://www.sandiego.gov/sites/default/files/ploovol4_15.pdf https://www.sandiego.gov/sites/default/files/ploovol4_15.pdf Pipes tend to last a long time, in large part because it's relatively straightforward to manage the chemistry problem in the pipes.