Project record

Oga-Katagami-Akita offshore wind marine installation programme

Official Oga-Katagami-Akita project illustration showing fixed-bottom offshore wind turbines off the Akita coast

Oga Katagami Akita Offshore Green Energy LLC

Japan's 315 MW Oga-Katagami-Akita project is moving through certified foundation design, base-port preparation, submarine-cable planning, navigation coordination, and a Sea Challenger charter for installation of 21 V236-15MW turbines ahead of a June 2028 operating target.

Project signal

Construction in Japan

Treat technical certification and the Sea Challenger charter as installation-readiness evidence, not proof of offshore construction. Track base-port acceptance, monopile and cable mobilisation, turbine-installation cadence, navigation controls, integrated testing, and commercial operation against the 30 June 2028 target.

Current status Design certification complete; base-port and offshore installation preparation active Source confidence Confirmed

Location

Japan / Asia Pacific

Segment

Offshore energy

Status

Design certification complete; base-port and offshore installation preparation active / Confirmed

Evidence reviewed

15 July 2026

Controlled taxonomy

Related sectors

The detailed segment above is the primary work classification. These broader sector links connect the project to related delivery and market research.

Knowledge context

Related knowledge topics

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Project anatomy

Scope, counterparties, and execution logic

Client / authority
Oga Katagami Akita Offshore Green Energy LLC
Delivery parties
Japan Offshore Marine, DEME Offshore, Penta-Ocean Construction, Kajima Corporation, Vestas, 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
Construction and base-port preparation are active; the published programme targets major offshore installation before commercial operation on 30 June 2028.
Works package
Marine delivery covers base-port staging, monopile foundation engineering and installation interfaces, submarine cable laying, transport and installation of 21 V236-15MW turbines using the Sea Challenger, navigation-safety coordination, testing, and commissioning.
Marine interfaces
The project joins a Japanese base port, large-component logistics, fixed-bottom foundation design, 15MW-class turbine installation, subsea cables, seismic design, navigation safety, and Ports and Harbours Act compliance in one constrained marine delivery system.
Commercial read
The award signal is broader than a vessel charter. Delivery depends on certification, base-port throughput, monopile readiness, cable and turbine sequencing, Japanese marine coordination, and effective integration between domestic civil contractors and international offshore capability.
Next milestone
Track base-port readiness, foundation installation sequencing, submarine-cable mobilisation, Sea Challenger arrival, and navigation-safety controls ahead of turbine installation.

Material change register

What changed, when, and what it proves

Only source-bound events that alter phase, scope, counterparties, delivery, completion, commissioning, or acceptance are listed. A change can advance the record without proving the next gate.

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.

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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.

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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, without proving mobilisation, component readiness, installation cadence, or offshore completion.

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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.

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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.

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Delivery watch

Evidence needed next

Track base-port readiness, foundation installation sequencing, submarine-cable mobilisation, Sea Challenger arrival, and navigation-safety controls ahead of turbine installation.

Decision watchpoints

  • Base-port completion and heavy-component arrival plan
  • Monopile installation and offshore foundation sequence
  • Sea Challenger mobilisation and turbine installation window
  • Submarine-cable and navigation-safety interfaces
  • Progress toward 30 June 2028 commercial operation

Related records 3

Project availability status

This public project page is a tracked market record rather than a tender notice, contractual commitment, or commercial instruction. Use the status, confidence label, evidence-review date, and source note together when judging how much weight to place on the signal.

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Record control

Evidence reviewed date is not a project-event date.

IMWO changes phase, participants, scope, completion, or acceptance wording only when a dated source establishes the change. The review date records when the evidence set was checked; it does not claim that physical work changed on that date.

Evidence reviewed 15 July 2026 Sources in this record 7

Source record

Oga Katagami Akita Offshore Green Energy's official project page defines a 315 MW fixed-bottom offshore wind scheme comprising 21 Vestas V236-15MW turbines off Oga, Katagami, and Akita, with commercial operation targeted for 30 June 2028. Its published schedule connects base-port use, foundation installation, submarine cable laying, turbine installation, commissioning, and onshore transmission works. The developer's 2 April 2025 update confirms Sawakigumi's base-port development contract, and its 16 May 2025 update confirms the Akita Port wharf lease with Akita Prefecture and the Tohoku Regional Development Bureau under the Port and Harbor Act. Penta-Ocean's 29 May 2026 release says the developer chartered the 1,600-tonne-lift Sea Challenger from Japan Offshore Marine, the DEME Offshore and Penta-Ocean joint venture, for turbine installation. The developer's 1 July 2026 update confirms completion of conformity assessment against Japanese technical standards and an earlier Ports and Harbours Act technical-compliance certificate, and identifies Kajima with Kobori Research Complex and COWI on monopile foundation design, Vestas and MHI Vestas Japan on turbine and tower design, and Arup Japan as owner's engineer support. The 30 June 2026 Navigation Safety Committee establishes a live stakeholder process covering the construction plan, surrounding waters, port and fishing-harbour use, marine traffic, and navigation safety; it does not establish approved navigation controls. JERA's February 2026 update adds that base-port development was under way ahead of major offshore equipment arrival.

Phase: construction. Evidence reviewed: 15 July 2026.

Project sources 7