Update 16 May: The platform was righted on 14 May. Professor Takeshi Ishihara of Tokyo University, and technical adviser to the Fukushima Forward project said turbine installation is set to go ahead, reducing delays to less than five days.
The floater is an advanced spar type, approximately 50 metres high and wide, weighing 8,000 tonnes.
The platform keeled over in waters one kilometre from Sumoto Port as seawater was taken on as ballast to sink the base to the seabed for testing, reported the Kobe Shimbun and Yomiuri Shimbun newspapers.
Civil engineering and construction company Yoshida-Gumi was responsible for the installation process. It contacted the coast guard on 9 May to report it could no longer control the platform. Yoshida Gumi is attempting to right the floater.
The coast guard for the Kobe region said the sea was calm, with little risk of the floater drifting.
The original delivery date in Fukushima was set for July, but it is expected to face delays of about five days as a result of the incident.
Work on the wind turbine portion has yet to commence. A 5MW turbine manufactured by Hitachi is set to be installed on the platform.