This dam was built by approximately 700 Chinese workers in 1883-84 (three months/24 hours a day, according to information in the book River in Ruin by Ray March). According to a reporter from the Salinas Index who was at the dam site while it was being built, the dam is six feet wide at the top and twenty-one feet wide at the bottom. It is made from marble and granite gathered and hewn onsite, held together with Portland cement. A pipeline was installed to capture the river water to be piped twenty-five miles to Monterey and the Hotel Del Monte. (The bridge was built at a later date.) The dam cost just 2,267.21 to build!
The current project to dismantle the two dams and reroute the river will cost 84 million! Here is a link to the River in Ruin book publisher.