By Ryo Isobe, FLEACT Yokosuka Public Affairs
YOKOSUKA, Japan – Yokosuka Ship Repair Facility and Japan Regional Maintenance Center (SRF-JRMC) moved and moored caissons from dry docks 3 and 1 into dry dock 1 for an upcoming caisson inspection, May 16, 2016. The command’s carpenter shop, dock maintenance team and dry docks branch worked many hours to support this successful operation from planning to execution.
The evolution was just one more example of the SRF-JRMC mission to provide ship maintenance and modernization for Commander, Naval Forces Pacific and U.S. Pacific Fleet using advanced industrial techniques while keeping the U.S. 7th Fleet operationally ready.
Caissons are watertight structures which act as gates to allow movement of water into and out of the dry docks. The caisson, which is also called a “lock gate,” is used to regulate water by controlling the flow into and out of the basin when SRF-JRMC dry-docks ships for repair. By pumping water out of the caisson tanks, they float and are used to control the volume of water in the docks. The caisson’s lower and upper tanks are filled to act as ballast or weight for the caisson itself to balance in the water.
“It is mandatory every 10 years to inspect and repair [the dry docks] to meet the requirements for safe ship repair work,” said Masaki Fukuda, the command’s dock master and a naval architecture engineer, who oversaw the entire project.
To begin, the SRF-JRMC team handled lines, controlled and released caisson valves, observed flooding and coordinated other services as needed to execute the docking. The Fleet Activities Yokosuka’s Port Operations Office supplied pushers and a beaver boat that pulled caissons into and out of the docks.
“The purpose for moving and placing the caissons temporarily in dry dock 1 is to precisely measure the center of gravity for further repair and maintenance,” Fukuda said. “This repair task ensures SRF-JRMC’s capability to maintain and fix U.S. Navy vessels.”
Once dry-docking was complete, the SRF-JRMC team wound the ropes and securely moored the caissons into dry dock 1, and then contractors externally inspected them and certified the need for repairs.
After mooring, Assistant Dock Master and Engineering Technician Kei Miura said: “The safety and communication among the team and shops is the most important aspect. The repair may take a little while before we will move them back and seated securely at the docks. Until then, we can enjoy the view of these docks filled with water.”
While the command normally docks vessels in dry docks 2, 4, 5 and 6 for availabilities, flooding water into dry dock 3 is a rare occasion.
Yokosuka Naval Base’s dry dock 1 construction began during the Edo Shogunate era in 1867 and was completed during the Meiji period in 1871. It has since been modernized, though still considered Japan’s first ever dry dock. Dry dock 3, which was built after dry dock 1 in 1874, remains unchanged. Its frontal arched shape was a typical trait of its era, different from the modern diamond shape.