Construction to relocate a U.S. military base began in Oura Bay in Okinawa Prefecture on August 20. 

A work ship carrying a crane started hammering metal cogs into the seafloor as part of efforts to solidify the soft seabed. 

The Japanese Defense Ministry plans to drive more than 71,000 sand piles into the seabed. 

The controversial work comes following the local Okinawa Prefectural Government’s disapproval of design changes to improve the ground. 

However, the central government won “execution by proxy” after a court case, overriding Okinawa’s strong objection.  

The Okinawa Prefectural Government had been demanding the construction not begin, citing concerns over environmental impact.