Miraflores lock under construction

Lock Construction

A key aspect of the canal plan was the decision to use a series of locks to raise ships above sea level and into a lake upon which they would traverse the Panamanian interior before being lowered again on the other side. Lt. Col. Harry Hodges of the Army Corps of Engineers designed the lock chambers and gates, which would be the largest in the world with the greatest amount of lift. Hodges had worked with Goethals on the Muscle Shoals Canal and was familiar with a fairly new building material concrete. Although concrete was then rarely used in structural engineering (and even less so concrete reinforced with steel), Hodges chose to use mass concrete huge blocks of unreinforced cement, sand, rock, and water. His design relied on the pure mass of 4.5 million cubic yards of concrete to withstand the enormous water pressure on the locks.

On the Atlantic side at Gatun, engineers planned a three-step lock, the largest ever conceived, to raise and lower ships 85 feet between sea and lake. On the Pacific side, two locks, one at Miraflores and one at Pedro Miguel, equaled the task. To manage their construction, Goethals assigned two accomplished engineers Lt. Col. William Sibert (Atlantic) and Army civilian Sydney B. Williamson (Pacific). Furthermore, Goethals accurately predicted that assigning a civilian and an Army engineer would lead to friendly competition between the two teams.

To build the locks, Sibert and Williamson had to coordinate efficient delivery of materials cement from the U.S. and rock, sand, and water from Panama. At Gatun, Sibert had a system of electric rail cars that made constant loops from the mixing plant to the lock site. They hauled large buckets to cableways that could carry the buckets to pour sites, thus delivering 20 six-ton loads of cement every hour. Williamson had a similar setup but with enormous cranes instead of cables and small steam-powered rail cars that delivered the concrete and hauled away the empty buckets.

Each completed lock chamber was 1,000 feet long, 110 feet wide, and up to 81 feet tall. Each lock had sets of parallel chambers, which allowed for two-way traffic. The locks required 46 primary and secondary gates, with 2 leaves per gate. Each leaf was made of steel frames covered in steel panels and measured 7 feet thick, 65 feet wide, and between 64 and 82 feet tall. After a century of use, the locks remained in excellent condition and were still studied as engineering marvels thanks to their impeccable design and construction.

Sydney Williamson directing concrete pours
Depositing Concrete in Miraflores locks

Pedro Miguel lock gates
Lock Gates at Pedro Miguel