BMLRR - how the railroad beds were built in swampy areas

From: alynry@hughes.net

Very interesting web site! Very informative. One question: I've always wondered how the railroad beds were built up in swampy areas (for example in Brooks close to the back Brooks Road? Tens of thousands of yards of gravel! Was this trucked in by dump trucks? Still quite a feat. Did the railroad have dump cars and built these areas up as the rail was laid? Or was this done by pick shovel and horses? At any rate, it's amazing. Keep up the good work.

—Allen Farrington