Dr. Axel Gruhn is very familiar with chemical contaminations, unexploded bombs and semi-intact ordnance. His duties at the HPA Unexploded Ordnance Service extend well beyond his desk. He also goes out on site visits where his expertise is needed. We interviewed him so that you can get an idea of his explosive job at the HPA.

About him

Name:                       Dr. Axel Gruhn
At HPA:                     since 2009
Position:                   Member of the Unexploded Ordnance Services

Dr. Axel Gruhn studied geological sciences, the field in which he later earned his PhD from the University of Kiel. Until 2009 he worked for various engineering firms where he was responsible for investigating contaminated sites and water extraction. During this time he came into contact with military contaminants and decided that this was something he wished to pursue further. After starting at the HPA in 2009 and working on the “Altenwerder” project, he moved to the Construction Oversight and Environment department. There he helped to develop the Unexploded Ordnance Service where he continues to contribute his valuable experience to this day.

Dr. Gruhn, what does a typical working day at the Unexploded ordnance Service look like?

„For one thing there are plenty meetings with colleagues planning a building project. We discuss their plans together: What are they planning to build? What kind of construction is it going to be? Is it a quay wall, lock, dike, road, railway line, building, area or even the replenishment of a port basin or canal? Afterwards we check whether there's the suspicion of unexploded ordnances. If this hasn't been checked before, the construction site manager is obliged to ask the fire brigade for an aerial photograph interpretation to scout the area. And that's when I'm also giving my advice to determine which areas to examine. Finally, the draw up of a concept for the ordnance cleaning can start. 

“The working day consists of more than just meetings, it also involves giving new plans thorough and critical consideration. These plans can be up to 50 pages long and accompanied by 10 to 20 annexes providing drawings that illustrate the circumstances. I then discuss with project managers the extent to which the plan can be taken forward or whether any changes are needed. Finally, we put out an invitation to tender for the required unexploded ordnance surveys. To get offers from unexploded ordnance disposal companies, some of these tenders are put out throughout Europe, others nationally throughout Germany, or we make limited enquiries with a few companies. This is also an area in which my colleagues come to me for advice on writing the tender document. This ensures that the required services are described in sufficient detail and misunderstandings are avoided.”

How often is help of the Unexploded Ordnance Service required?

“Various different enquiries come in. These are not just specific building plans, but also strategic planning documents such as feasibility studies. A typical enquiry from a colleague might be, for example: I have a plot of land for which I want to make plans, are there any issues with unexploded ordnance there? It’s also not just large-scale construction plans, but also maintenance work. For example, a colleague might need to lay electrical lines 1.2 m below the ground and asks: Is it safe to dig a ditch in this location? In this case we must first ask: Do we suspect that there might be unexploded ordnance there? Or is it simply a case of replacing the lines in an existing cable duct? Was the ground level at this location significantly lower during the war than the intended depth for the building works? These are rather short enquiries, but which end up taking a couple of hours to research, consider and provide an answer. So on average I’m working on about ten different projects each week. Many I work on from my desk, but now and again I also make appointments with colleagues to go out for site visits to get a better idea of the local situation.”


“Defusing, removal and disposal of ordnance is done by the fire department’s ordnance disposal service. The materials removed are usually stored temporarily in a bunker in Hamburg, especially those which can be safely stored for a couple of weeks. Unstable objects are transported straight to official decommissioning stations in Schleswig-Holstein or Niedersachsen.”

Is there a special training for the unexploded ordnance service?

„The stories are usually pretty individual. Geoscientists are predestined for this job since they are familiar with the behavior of the subsoil. Furthermore, they have already learned to see in a three-dimensional way. The topic as such depends on the layer structure of the subsoil. Besides, they also learn certain engineering skills depending on their life story. Many people, also in engineering firms, who are working on the topic, are geoscientists. The search for unexploded ordnances is carried out by physical methods since those ordnances influence the earth's magnetic field. Therefore, you can detect anomalies with a magnetometer. This anomaly might be a bomb, but it might also be an old steel pipe, a metal bucket, a rope or something similar. Furthermore, there's the radio detection, electromagnetics; those are all methods geoscientists usually use for their natural resources search. And that's why it's easier for us to understand the work procedures of ordnance clearance companies. In addition, the Bundeswehr University in Munich offers an official training course for specialist planners for ordnance clearance."

Can you name a current project?

„There's always more than just one project on the go. The most famous one is the fairway adjustment. HPA expects any legal concerns to be cleared up soon. When this day comes, we want so prepared perfectly to that the work can start immediately. Therefore, we are working on solutions concerning companies to work with and whether to publish an invitation to tender or not. By now we have already prepared the ground well. The construction work doesn't only apply to the subsoil waterside but also landside. Even dolphins are affected. In conclusion the preparation is very complex since there is so much structural extra work. You see, my colleagues keep me very busy with looking through concepts and invitations to tender." 


“There was this huge technical challenge where an anomalous mass, thought to be unexploded ordnance, was discovered under a bridge and had to be recovered. This was really difficult. The objects were at a depth of eight metres, and the bridge was only five metres above the ground. Normally we would need to bore large shafts into the ground. But in this case we had to opt for smaller shaft segments and do without a drilling tower. This was certainly a special bore drilling and clearance process. We ultimately found a 500 lb bomb and steel pipe. The A7 motorway had to be closed for several hours whilst the bomb was made safe. In most cases we only find metal fragments, we rarely come across an actual unexploded bomb. We generally find between one and four unexploded bombs each year in the port area.

Another time a tenant called to warn me about a bomb on his leasehold property. After I asked him about the type of the bomb, I learned that nobody found an actual bomb so far but just an anomaly. Therefore, at this point you could only tell that there was a magnetic impediment hidden in the subsoil. You couldn't see, hear or touch it. It wasn't even proven to be of relevant size. I expected that a competent ordnance specialist had already given an exact evaluation and had therefore called the police and the unexploded ordnance service. So, this surprising call caused quite a lot of agitation at first because it was expressed in a dramatic way."


"Of course, I'd like to show him the port with a boat trip around the port. But also, the stair quarter in Blankenese, a tour around the outer Alster lake and maybe a visit of the municipal park. The park of the cemetry in Ohlsdorf is also very impressive. In former times I used to go to the Telemichel, the TV tower with my visitors. Unfortunately, the cafeteria with its offer of all the cake you want doesn't exist at the moment."

Thank you for the interview.

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