ONP Management

Comprehensive offshore and civil engineering expertise.

ONP Management GmbH (ONP) was founded with the aim of assisting our clients in the development, financing, construction and operation of offshore wind farms as well as infrastructure projects. We achieve this by providing expert advice combined with hands-on support.

ONP's Value Proposition

Extensive individual know-how and hands-on experience in offshore wind and civil engineering
Independent and individual client support in all project phases
Risk-conscious and value-focussed approach
Commitment to technical innovation in offshore wind with a consistent focus on project lifecycle costs
Market penetrating industry network

ONP's expertise

Our clients benefit from our comprehensive expertise in the areas of offshore wind and infrastructure projects, which we put at their disposal, promptly and efficiently - and always with the success of the project in mind. ONP's integrated approach and broad experience in the active development and realization of numerous offshore wind projects is accompanied by a market-penetrating network of competence.

ONP's guiding principle

Whether seeking assistance for specific questions or the management of an entire project, our clients can always rely on our project management competency as well as our unbiased expert advice. Uncompromising customer orientation is our guiding principle. With this in mind, we ensure that the goal-oriented co-operation with our clients is both open and transparent.

Our team

All of our senior team members have extensive individual experience in design, engineering and project management in the areas of offshore wind and civil engineering. Our know-how and experience is complemented by an excellent individual network in the offshore wind industry.

Our management has a long individual track record in offshore wind projects and major maritime infrastructure projects.

Dipl.-Ing. Martin Rahtge, Managing Partner

Dipl.-Ing. Martin Rahtge
Phone +49 40 3602 527-13
Mobile +49 172 420 8640
Mail: Martin.Rahtge@onp-management.de

Martin Rahtge has, as from 2024 together with Knud Grimm, overall responsibility for the areas of technology and project management, risk and contract management as well as all issues related to project finance.

Following his vocational training in the construction industry, Martin Rahtge studied civil engineering at the Bremen University of Applied Sciences. For three years, from 1981, he worked at Philipp Holzmann AG. Thereafter, he continued his civil engineering studies at the Technical University of Berlin.

From 1988 to 2002, he once again worked for Philipp Holzmann AG, where for the last four years he managed the company's Bremen branch. Thereafter, he joined Hochtief Construction AG, initially as its Bremen branch manager, then as a member of the Hamburg senior management, and finally as its chairman. In this position, Martin Rahtge was responsible for some 450 staff and revenues in excess of 200 million euros per annum.

His vast technical and project management expertise is based on more than 40 years of professional experience, particularly in the area of complex water engineering projects. As early as the 1990s, Martin Rahtge managed large-scale projects involving the construction of sluices, shipyards and port facilities. After the turn of the millennium, he also headed international harbour, bridge and dam engineering projects.

Martin Rahtge developed a particular passion for the field of offshore wind power plant construction, where he, together with his management team, advanced the Offshore business division from its modest beginnings to the market leader of the German offshore wind power industry. Along with his experience in managing large-scale projects, Martin Rahtge also expanded his expertise through the planning, construction and operation of two of the largest and most powerful jack-up vessels in the European market.

In 2014, Martin Rahtge, together with other high-ranking executives from the Offshore business division, launched ONP Management GmbH in order to put his vast knowledge and practical expertise at the disposal of clients engaged in the development, financing and realisation of offshore wind power plants.

Dipl.-Ing. Knud Grimm, Managing Director

Dipl.-Ing. Knud Grimm
Phone +49 40 3602 527-15
Mobile +49 172 265 8558
Mail: Knud.Grimm@onp-management.de

Together with Dipl.-Ing. Martin Rahtge, Knud Grimm is responsible for the areas of technology and project management at ONP Management GmbH.

Knud Grimm is an experienced Project Manager who started his career in the international division of Bilfinger AG in 1991, with the intention to manage complex international civil projects. In 1994, Knud Grimm joined the international Bilfinger team in Far East and worked there as a Site- and Project Manager for large tunneling and bridge construction projects in Taipei and Bangkok, later on for several other civil projects in Germany.

In 2005, Knud stepped into the world of offshore wind joining HOCHTIEF's young offshore department as second in charge. He took an active role, together with Martin Rahtge, to build up the small offshore wind team within HOCHTIEF until its final strength of more than 400 people in 2014, with own jack-up installation vessels and several awarded projects. By continuously supporting the inhouse team and competency build-up Knud was responsible for several international offshore wind tenders - with main focus on foundation EPCI work packages. Knud was project manager of the Horns Rev Foundations Improvement project, a technically and logistically challenging offshore project awarded in 2007.

In 2010 Knud and his team secured the first industrial-size offshore EPCI project for HOCHTIEF. Consequently, Knud was appointed Project Manager for the Baltic 2 foundations and T&I project until 2012 when he took over a project management role for the Cape Wind project in the US.

Being a civil engineer with an extensive project management background on various technically challenging international projects, Knud Grimm has continuously expanded his technical expertise and management skills, maintaining strong focus on pragmatic solutions for overall project success. Until HOCHTIEF main shareholder's strategic decision to step out of the offshore wind sector until late 2014, he was in charge for several other offshore wind project tenders, mainly in UK waters.

As a core member of ONP's management team since its inception in early 2015, Knud Grimm has played a pivotal role in establishing the professional organization of ONP. Knud has undertaken several complex management roles in both offshore wind and civil projects. In early 2022, Knud was appointed General Manager of ONP, taking on additional management responsibilities within the company. In early 2024, Knud was promoted to Managing Director to support Martin Rahtge in guiding ONP towards a successful future.

Michael Berges

General Manager, QM-Officer

graduated Civil Engineer (B.Eng.) Civil Engineering /

Infrastructure Projects : since 2007

Offshore Wind: since 2011

Green Hydrogen: since 2021

Michael brings extensive project management experience from international civil engineering and offshore wind farm projects. As General Manager, he supports the ONP management team with his well-structured and organized approach. Michael is known for his pragmatic solutions, unwavering commitment, and strong focus on quality and efficiency.

He actively participates in global projects across ONP's three business sectors: Offshore Wind, Maritime Infrastructure, and Green Hydrogen.

Dieter Bielfeldt

General Foreman

Work experience infrastructure: since 1976

International civil projects: since 1983

Dieter is an experienced General Foreman with employments on a variety of national and international large-scale infrastructure projects.

These days Dieter strengthens the ONP team of local construction supervisors for the client DEGES on the Weser crossing A 281, B4 tunnel project, monitoring the production of reinforced concrete tunnel elements. His broad experience and dedication make him a valuable asset to our team.

Laurenz Boberg

Senior Project Manager, graduated Civil Engineer

Work experience: since 1993 Site Manager

Infrastructure: since 1995 Project Manager

Infrastructure: since 2002

Offshore Wind: since 2011

Laurenz is an experienced project manager with vast expertise in tunneling and international large-scale infrastructure projects. For ONP, Laurenz leads the project management team of the Weser-Crossing tunnel project A281, BA 4.

Youssef Chaouch

Senior Project Engineer, graduated Civil Engineer (M.Eng.)

Work experience: since 2016

Major Civil and Infrastructure Projects: since 2016

During his career, Youssef was involved in the development of large-scale port & international infrastructure projects, in 13 different countries. His expertise covers infrastructure design & engineering, tendering and project management. Youssef is currently acting as Senior Project Engineer on the Weser-Crossing tunnel project A281, BA 4.

Andreas Clausen

Senior Project Manager, graduated Civil Engineer

Plant Engineering and Power Plant Construction: since 2003

Offshore Wind: since 2012

Andreas has been acting as project manager in the plant engineering and energy sector since 2003. His experience is covering the management and coordination of both onshore and offshore construction projects in respect to time, cost, safety, quality and interfaces. Andreas has a thorough understanding of all aspects of a construction phase. With his extensive knowledge and goal-oriented approach Andreas enables successful project execution.

Jutta Cohrs

Team Assistant, graduated Translator

Work experience: since 1994

Jutta joined ONP from the beginning and is both the personal assistant to the management and the team assistant for the entire ONP team. She manages the head office and ensures a safe and efficient work environment, organizes company events and travel arrangements along with all administrative processes.

Arne Frerichs

Senior Project Manager, graduated Civil Engineer

Site Manager Infrastructure: since 1999

Offshore Wind: since 2011

Arne is an experienced project manager with vast expertise in complex, international tunneling projects. He also took responsibility for the BoP scope on several offshore wind projects during bidding and project execution. Arne is currently acting as Client’s Representative / Construction Management on the Weser crossing A281, BA 4 tunnel project.

Bernd Füchtmann

Senior Project Engineer, graduated Civil Engineer (M.Sc.)

Work experience: since 2013

Civil Engineer Marine Infrastructure: since 2018

Since 2020 Bernd is working on the Weser-Crossing tunnel project A281, BA 4 in Bremen, Germany. Bernd was responsible for preparation of tender documents, overall construction schedule as well as project organization and document management.
In the current execution of the project, he is responsible for the client's design coordination and management.

Vishal Gangore

Senior Project Engineer, graduated Mechanical Engineer (M.Sc.)

Offshore planning & production engineer: since 2017

Offshore wind & green hydrogen: since 2022

Vishal commenced his career as a design engineer and production planning engineer in the Persian Gulf. He also acted as offshore installation engineer in the oil & gas industry. In 2019 he moved to Germany where he completed his Masters in Management and Engineering in Production Systems at RWTH Aachen University.

At ONP, Vishal is working as a project engineer mainly in the field of green hydrogen in combination with offshore wind energy but also as a specialist for financial modelling and production reviews.

Katrin Kiehn

Project Engineer, graduated Civil Engineer M.Eng.

Work Experience: since 2020

Katrin commenced working at ONP during her studies. With her Master Thesis on the interaction of spudcan and soil properties for Heavy Lift Jack-Up Vessels, Katrin contributed to the development of the FEEDERDOCK Project, a novel offshore wind installation vessel for the US and European Markets. She is currently supporting ONP in project development and project management activities for several clients.

Henrik Kolberg

Senior Consultant Offshore Wind, graduated Construction Manager, Environmental Systems Engineer (M.Sc.)

Construction Industry: since 1999

Offshore Wind: since 2012

Henrik is a senior consultant with over 13 years of dedicated offshore wind experience, supported by more than 20 years in the construction sector. At ONP, he advises international clients on project development, due diligence, CAPEX/OPEX analysis, financial modelling, and strategic planning.

He previously served as Permit Manager for Parkwind’s Arcadis Ost 1 offshore wind project and in 2025 worked as Site Manager in Thyborøn for the Thor offshore wind farm. Henrik is also part of the FEEDERDOCK development team.

Bernd Löhden

Senior Project Manager, graduated Civil Engineer

Technical Office: since 1989

Site Manager: since 1996

Renewable Offshore: since 2007

Head of Department Marine Offshore Technology: 2012-2015

During his career, Bernd gained project management experiences on many technically challenging projects, e.g. building shipyards, bridges, ship locks, harbours and various offshore wind projects. Bernd is currently supporting the new Köhlbrand-Crossing Project in Hamburg.

Eike Mantei

Senior Project Engineer, graduated Civil Engineer

Work experience in construction: since 1982

Construction Manager Civil Works: since 1991

Offshore Wind: since 2007

Eike is an experienced construction manager with a track record in marine and tunneling projects. He also worked on several offshore wind projects in Denmark, UK and Germany. Eike is currently part of the construction management team on the Weser-Crossing tunnel project A281, BA 4.

Lasse Mindermann

Project Engineer, graduated Mechnical Engineer (M.Sc.)

Energy and Process Engineer: since 2021

Lasse Mindermann commenced working at ONP in early 2025 as a project engineer. During his studies, he worked on various models and simulations on energy storage, electrolyzers and fuel cells at university, which enabled him to build up in-depth expertise in the field of renewable energies, especially hydrogen. For ONP, Lasse is mainly working in the project management team of the NorthH2 project.

Heiko Missfeldt

Senior Project Engineer, graduated Civil Engineer

Cost estimator: since 1992

Project Scheduler: since 1993

Renewable Offshore: since 2007

Heiko assembles a wide expertise in the field of planning, work preparation and time scheduling for major infrastructure projects, offshore wind and civil engineering projects. On offshore wind projects he is familiar with the development of installation equipment. He is an expert for all professional planning tools including time chainage diagram and process simulation. Currently Heiko is responsible for time scheduling and construction methods of the Köhlbrand-Crossing project in Hamburg.

Stefan Müller

Senior Engineering Manager, graduated Civil Engineer

Civil Engineering: since 1995

Renewable Offshore: since 2006

Head of Technical Department: since 2012

Stefan started his career as a Structural Engineer. He worked on various international civil engineering projects where he has been responsible for the overall coordination of design and interface management for complex civil engineering projects involving contract and claim negotiations. Stefan is currently supporting the HPA and ReGe on infrastructure projects in Hamburg.

Heiko Obst

Senior Project Manager, graduated Civil Engineer

Civil Engineering: since 1995

Site Manager Infrastructure: since 1997

Project Manager: since 2001

Heiko assembles a wide expertise as construction and project manager in the field of work preparation and execution of complex infrastructure Projects such as port constructions, ship locks and container terminals. In his former role as a managing director, he developed leadership and management skills. As Client’s Representative and member of the project management team Heiko is acting as Senior Project Manager on the Weser-Crossing tunnel project A281, BA 4 for the construction of the concrete tunnel elements in Bremerhaven.

Magnus Reinke

Senior Offshore Technician, Graduate in Concrete and Steel Construction and Crane Operator Certificate

Work experience in construction: since 2001

Offshore Wind: since 2007

Since starting his career in offshore wind Magnus has worked on numerous vessels during construction and maintenance throughout Europe. From 2016 until 2022 Magnus was crane operator on the HLJV Innovation. He joined ONP as Senior Offshore Technician for the development of the FEEDERDOCK Project, a novel offshore wind installation vessel for the US and European Markets. He is currently acting as Offshore Installation Manager for the foundations package at the 960MW OWF He Dreiht for EnBW.

Katrin Renken

Commercial Manager, Degree in Banking

Work experience: since 1999

Work experience in UK: 2006 – 2018

Katrin is responsible for all commercial matters within ONP, such as accounting and controlling, including month-end and year-end reporting, preparation of quarterly reports for shareholders, budget planning and insurances.

Katarzyna Maria Sauer

Senior Legal Counsel/ Contract Manager, LL.M.

Plant Engineering and EPC Projects: since 2006

Kate is an experienced contract & risk manager having worked on large Engineering and EPC projects in the Plant and Process Engineering, Power generation and Materials-handling industries for the companies Lurgi, Alstom, Thyssenkrupp and Hochtief. She has a thorough knowledge of the FIDIC and NEC forms of contract and acts as legal advisor and contract administrator for all ONP assignments.

Meik Schacknies

Senior Project Engineer, graduated Civil Engineer

Structural Engineer in onshore wind: since 2001

Section Manager offshore wind: 2011 - 2014

Engineering Manager offshore wind: since 2015

At ONP Meik is working as senior project engineer with focus on technical package management of wind turbines as well as offshore T&I activities. He is currently acting as lead engineer in the FEEDERDOCK Project, a new development of a jones-act compliant offshore wind installation vessel for the US and European Markets.

Boje Schirmacher

Senior Project Engineer Infrastructure, graduated Civil Engineer, International Welding Engineer (IWE)

Hydraulic Engineer: since 2001

Offshore Wind: 2012-2014

Boje is an experienced project engineer with vast expertise in the implementation of marine construction infrastructure projects. Between 2014 and 2020 Boje worked on a major PPP project, as construction manager and in the technical back office. Boje is currently acting as senior project engineer on several quay wall projects of the Hamburg Port Authority.

Michael Schreier

Senior Project Manager, graduated Civil Engineer

Construction Manager: since 1988

Marine Works: since 1991

Project Manager Infrastructure: since 2014

Michael assembles a wide expertise as construction manager in the field of bid preparation and execution of complex infrastructure projects. Since 2011 he has been heading major tunnel engineering and bridge construction projects. As member of the project management team Michael is acting as Senior Construction Manager on the Weser-Crossing tunnel project A281, BA 4.

Heike Timm

Senior Project Manager, graduated Civil and Environmental Engineer

Wind Energy: since 2001

Project Lead Infrastructure: since 2018

Heike is an experienced senior project manager. She has been responsible for the development of towers and foundations at DeWind and Nordex. In 2018 she took over the team and project lead for the Fehmarn Belt crossing at DB Netz. In order to manage the wide number of planning offices, external experts and stakeholders she implemented BIM, AGILE and LEAN methods. At ONP, Heike leads the development of a large offshore project and supports our customers in the energy and infrastructure segment in the implementation of BIM and LEAN.

Nils Wehner

Senior Project Manager, graduated Civil Engineer, PMP®

Plant Engineering and Construction: since 2001

Energy Generation: since 2007

Heading Departments: since 2008

Nils is a versatile Project Manager with extensive experience in the field of heavy industrial plants, energy generation and infrastructure projects. He has been responsible for project and engineering management on the part of investors and general contractors on numerous international CapEx projects, managing multi-discipline teams in regionally spread organisations.

Frank Witte

Senior Project Manager, Area Manager Americas, graduated Civil Engineer

Work experience: since 1998

Heading Technical Departments: since 2002

Wind Energy: since 2008

During his long-term leadership roles as a sales and business development manager with operative responsibilities, Frank has gained substantial expertise in business strategy, project management, marketing and sales and customer management. Frank has been building-up and managing international technology and sales teams throughout Europe, Asia and Americas. Since 2018 Frank is heading the FEEDERDOCK Project, a new development of a Jones-Act compliant offshore wind installation solution for the US and global markets.

Daniel Zonneveld Coltro

Senior Project Engineer, graduated Environmental & Safety Engineer

Contracts Management/ Liaison Officer: since 2011

Offshore Wind: since 2018

Daniel is a core member of ONP's technical competence team, where he assumes responsibility for simulations of wind conditions, electricity generation & green hydrogen production. Over the years he has contributed to several feasibility studies & supported the development of an offshore electrolyser project. Daniel is also part of the FEEDERDOCK development, a global marine logistics solution designed to enhance the efficiency of offshore wind installations. In 2025, he served as Site Manager in Thyborøn Port (Denmark) for the Thor Offshore Wind Farm.