Foundations of Bridges and Buildings
Is an old textbook I must have picked up at a yard sale a few decades ago. It was updated in 1941 but most of the technology was from before the first printing in 1914. I decided to read a bit and got sucked in.
Among the many feats it lists a cassion built in 1888, a wood lined hole in the water 60 ft x 100 ft x 143 feet deep. There would have been steam powered pumps and winches but most of the labor would have been manual, supplemented by horses and mules. If you have cut firewood without the benefit of a chain saw you can appreciate the labor to provide boiler fuel. And the men and animals needed a little fuel from the farms too.
A common type of bridge foundation would have involved a hole like this thru some depth of water then thru the river bottom for some distance. Then a lot of wood piles would be driven thru the bottom of it for a further 30 to 150 ft (sometimes spliced). Sometimes this would be done with the cassion full of water and sometimes it was pumped out. Next a gazillion yards of concrete was poured in stopping just below water level. After that the easy part would begin.