Nuclear Industrial Directory of Japan

Nuclear Industrial Directory of Japan

Penta-Ocean Construction Co., Ltd.


2-2-8, Koraku, Bunkyo-ku, Tokyo 112-8576, Japan

Contact Person
Mr. Yoshiteru Tsuriya

Corporate Information

Paid-In Capital : 30,449 million yen
Employees : 2,945(as of Sep 30, 2019)
President, CEO and Representative Director : Takuzo Shimizu

Penta-Ocean Construction Co., Ltd. has been continuously evolving since its founding as Mizuno-Gumi in Kure City, Hiroshima Prefecture in 1896. Our initial business in marine civil engineering works has significantly expanded to land civil engineering and building construction works. Also, we have had historical involvement in numerous and notable major projects overseas, particularly the Suez Canal Widening and Deepening project in Egypt, etc. We are now aiming to become a global No.1 contractor in port, coastal and waterfront areas.

Corporate Characteristics

Penta-Ocean is known for possessing the most-advanced technologies in marine construction and owning work vessels equipped with cutting-edge technologies that can meet the increasing demands for large-scale waterfront development.

Major Works

Penta-Ocean has the most advanced construction technologies and pioneering expertise in marine engineering works that deal exclusively with the construction of harbors for nuclear power plants.
The following are major power plant projects undertaken by Penta-Ocean.


Penta-Ocean Construction has developed a number of advanced techniques related to the construction and maintenance of infrastructure, including nuclear power plants. One of these techniques is the Permeation Grouting Method(PGM), which is a unique soil improvement method that minimizes deformations on the ground surface. This method enhances the strength of the ground and reduces the likelihood of liquefaction during an earthquake. Controlled Curved Drilling is a new technique developed by Penta- Ocean that is applicable to the ground located under existing structures. A schematic illustration of this technique is shown in the figure below. This technique has already been applied in several existing types of infrastructure, including the subsurface of runways at Fukuoka International Airport and Tokyo International Airport. The prevention of liquefaction at nuclear power plant sites is critical for ensuring their safety during and after an earthquake. Consequently, the application of Controlled Curved Drilling in PGM may be a suitable choice for improving the ground foundations for nuclear power plants.

Schematic illustration of controlled curved drilling for application of PGM