Why was the construction of the Erie Canal such a great challenge?

The Erie Canal had no engineers working on it in many sections. The amateurs in charge of it could only survey with the compass, chain and level. Men would agree to be responsible for a section at a time. They would dig by hand and uses horses to haul the dirt away. There was a problem when they got to Lake Erie because the Hudson River was 600 feet below the Lake Erie. They had to dig through limestone and mountains to get to Lake Erie. They lost 1000 workers in one season due to malaria.