There was constant column footing replacement going on since the early
80's. On any given day 2 or 3 were under repair, usually nowhere near
each other. Each one took about a week to do, between digging out the
old one and pouring the new one. However, at that rate it would have
taken 50 years to do all of them. During rebuilding they were done 20 at
a time. They would do every other one of a consecutive group of 40, then
when those were done do the other 20, then move across the street and do
the same on the other side, then move down to the next group of 40. This
way all 20 were dug up in a few days, and all 20 were poured in a couple
of days. Even then, it took a good six months to do the line.
Blue Line between Evergreen and Sacramento, a much smaller stretch,
still took almost 5 years to do, as they were done three at a time.