Project record

Oga-Katagami-Akita offshore wind marine installation programme

Official Oga-Katagami-Akita offshore wind illustration showing Vestas V236-15MW turbines off the Akita coast

Oga Katagami Akita Offshore Green Energy LLC

Japan's 315 MW Oga-Katagami-Akita project now has certified foundation design, a 2,500-tonne crawler crane and multi-axle transporters at Iijima Wharf, named base-port logistics contractors, and dedicated vessels for foundation and turbine installation. Offshore mobilisation and installed work remain future milestones for the 21 V236-15MW turbines.

Project signal

Construction in Japan

Current status Design certified; Iijima Wharf heavy-lift and component-handling workfront active Source confidence Confirmed

Location

Japan / Asia Pacific

Segment

Offshore energy

Status

Design certified; Iijima Wharf heavy-lift and component-handling workfront active / Confirmed

Last checked

28 July 2026

Coverage

Related sectors

Offshore energy is the primary work classification. Related sectors connect this record to adjacent marine delivery and market coverage.

Subject index

Related subjects

These subject pages bring together related projects, technical articles, reports, and evidence methods.

Project anatomy

Contract scope and delivery roles

Client / authority
Oga Katagami Akita Offshore Green Energy LLC
Delivery parties
Japan Offshore Marine, DEME Offshore, Penta-Ocean Construction, Kajima Corporation, Sawakigumi, Kamigumi, DENZAI, COWI, Vestas, MHI Vestas Japan, Arup Japan
Contract route
Publicly selected developer consortium with developer-led multi-package contracting and a dedicated vessel charter through Japan Offshore Marine
Execution window
Base-port and onshore construction are active; heavy-lift and transport equipment are at Iijima Wharf, while the published programme targets offshore installation before commercial operation on 30 June 2028.
Works package
Marine delivery covers Sawakigumi's base-port development, turbine-component unloading and tower pre-assembly by Kamigumi and DENZAI, monopile design and foundation works led by Kajima with COWI and CP-16001 interfaces, submarine cable laying by a contractor not publicly identified, and installation of 21 V236-15MW turbines through Japan Offshore Marine using Sea Challenger.
Marine interfaces
The project joins Iijima Wharf heavy-lift logistics, component laydown and pre-assembly, CP-16001 foundation works, 15MW-class turbine installation, subsea cables, seismic design, navigation safety, and Ports and Harbours Act compliance in one constrained marine delivery system.
Commercial evidence boundary
The live chain is broader than a vessel charter: Sawakigumi, Kamigumi and DENZAI cover distinct base-port functions; Kajima links certified monopile design to CP-16001 foundation works; and Japan Offshore Marine links Penta-Ocean and DEME capability to Sea Challenger turbine installation. Cable award and offshore mobilisation remain open evidence gaps.

Project timeline

Material developments

Dated events that changed scope, counterparties, delivery, commissioning or operating status.

Open this project in the Change Log

Iijima Wharf heavy-lift and component-handling workfront inspected

The developer recorded a 2,500-tonne crawler crane, multi-axle transporters, and the planned component delivery and storage area at the base port. The visit confirms equipment and an active workfront, not completed berth acceptance, component arrival, or offshore mobilisation.

Source

Technical conformity certification completed for the wind facilities

The certificate closes the published design and certification process under Japanese technical requirements, while fabrication release, installed foundations, offshore construction, commissioning, and commercial operation remain separate delivery gates.

Source

First navigation safety committee convened for construction planning

The meeting records formal discussion of project waters, related ports and fishing harbours, marine traffic and navigation safety. Final controls, work windows and permits were not approved by this record.

Source

Sea Challenger turbine-installation charter contract concluded

The charter fixes the named 1,600-tonne-lift installation vessel and Japan Offshore Marine interface for 21 turbines. The same release schedules CP-16001 for foundation works under Kajima management, without proving either vessel's mobilisation or offshore execution.

Source

Base-port lifting and pre-assembly contractors identified

The developer placed a 2,500-tonne DENZAI crawler crane at Iijima Wharf and named Kamigumi and DENZAI for turbine-component unloading and tower pre-assembly. This is a contracted logistics workfront, not evidence that turbine components have arrived.

Source

Akita Port wharf lease agreement signed

The agreement grants project use of the designated base port and sets the public-authority access framework. Berth preparation, heavy-component handling readiness and offshore construction remain future evidence.

Source

Sawakigumi base-port development contract signed

The contract names the base-port works counterparty and moves the port interface into contracted preparation. Completed construction, accepted facilities and installation-base availability remain unreported.

Source

Evidence gap

What remains unverified

Outstanding evidence

  • Iijima Wharf acceptance and first heavy-component delivery
  • CP-16001 mobilisation and monopile installation sequence
  • Sea Challenger mobilisation and turbine installation window
  • Submarine-cable contractor, vessel and navigation-safety interfaces
  • Progress toward 30 June 2028 commercial operation

Related records 3

Reporting status

Construction, confirmed confidence

Last checked 28 July 2026 across 9 cited sources. The dated timeline above carries the project events.

Last checked 28 July 2026 Cited sources 9

Sources and related records

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Source collections

Project sources 9