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Academics and industry team up for marine UXO surveys

Company borne out of an academic collaboration benefits both students and industry doing offshore UXO surveys in the North and Baltic Seas.

by Graham Chandler on March 8, 2013 applied

[Click to enlarge]

Cleaned, IGRF corrected and detrended data, using an upward continuation filter. The data have been recorded with a single magnetometer and a profile spacing of 80 m. The profiles are oriented N-S.

Two merging lines of strong anomalies can be seen in the gridded data. The anomalies match with the location of a filled glacial channel system, which was detected by means of reflection seismics.

[Click to enlarge]

Cleaned, IGRF corrected and leveled magnetic data, recorded with a single magnetometer and a profile spacing of 300 m. The profiles are oriented NE-SW. In the gridded data a line of strong anomalies can be seen above a buried pipeline, which runs from NW to SE.

When the volume of offshore UXO surveys in the Baltic and North Seas began to expand with the growth of offshore wind farms in the late 2000s, a professor at the University of Bremen’s MARUM (Center for Marine Environmental Sciences), Dr Tobias Moerz, decided to spin off an independent company. The new company, GmbH, was formed in February 2009 and it enjoys the benefits of close contact and association with the university and its scientific expertise within MARUM and the Department of Geosciences.

Starting in 2006, the university and MARUM carried out industry-related geotechnical and geophysical surveys under the working group known as Marine Ingenieurgeologie, headed by Moerz. As volumes quickly increased, the rapidly growing workload created other concerns. “The increasing risks and liability requirements related to vessel charter for geophysical surveys and exploration of offshore wind farms necessitated the creation of a legally independent company,“ says Bastian Kuehl who works in project development and applied geophysics for Geo-Engineering. He adds that the new company has signed a co-operation agreement with the university and MARUM.

Johannes Brock, who is in the same department as Kuehl, says that since its founding the company has worked closely with offshore windpark developers in Germany. “The schedules of those developments are very strictly prescribed in documents by the German authorities,” he says.

The UXO surveys are prescribed by Germany’s Federal Maritime and Hydrographic Agency in its 2008 publication Standard Ground Investigations for Offshore Wind Farms. “UXO surveys are required and someone has to do them,” says Brock. “There are not many companies in Germany who are competing in this business, so we took our chances.”

Geo-Engineering maintains its strong ties with the University of Bremen and works closely with university personnel. That shows in the makeup of its staff, most of whom were recruited from university alumni after graduation, and in some cases even before. That strategy continues to be a recruiting advantage for the company. “We offer young innovative specialists in geology, geotechnics and geophysics the opportunity to use their skills directly in the industry,” Brock says.

It’s a win-win. The students are highly motivated to do applied fieldwork whereas Geo-Engineering benefits from their educated knowledge of the latest trends and technologies in the field. At the same time, the students can earn good money during their studies and secure valuable experience for their future careers. For example, a lot of offshore work is done in the summer between July and September, which happens to be the semester break for German universities. Some students stay on throughout the year. Many like the exposure to hands-on research in this field of ocean sciences, as it helps them make decisions about their career directions.Kuehl notes that for those students who wish to use project data for a bachelor‘s or master‘s thesis, the university and industry can permit them to use recorded data, usually with the proviso of deleting proprietary information such as geographic co-ordinates.

The university’s scientific expertise is made available as a result of the association between MARUM and the Department of Geosciences. For example, MARUM maintains a repository of core from international deep-sea drilling as well as advanced technology for ocean exploration. Examples of the latter include a deep-sea drill rig, remotely operated vehicles, and an autonomous underwater vehicle. All of which could be useful to Geo-Engineering in its UXO surveys.

Kuehl cites flexibility as one of Geo-Engineering’s competitive advantages. “Since our company is not very big, our staff in the fields of civil engineering, geology, engineering geology and geophysics work closely together,” he says. “In this way, we are able to find unconventional solutions for our customers.”

Geo-Engineering customers include clients who require offshore UXO surveys to support wind farm installations. Generally, these clients must first carry out (or contract out) the required preliminary research to ascertain where potential seabed targets might lie. The research might entail searching military archives and libraries. Armed with these data, the client will then engage an offshore survey contractor such as Geo-Engineering.

This is where the students’ hands-on experience begins. Geo-Engineering takes one or two students on board who are able to gain valuable practical field experience right from the start. They take part in the initial magnetic gradiometer and side-scan survey, wherein the company uses steel survey boats with the gradiometer on a cable about three to five times longer than the boat. “For the cleaning survey, we use larger boats with the capability to host working class ROVs (remotely operated vehicles),” says Brock. “For near-shore or in-shore work, we use our own 7-metre-long, gfk [glass-fibre-reinforced plastic survey boat [which is non-magnetic].”

Students also have the opportunity to help with hardware and data acquisition equipment. “We use two GEOMETRICS G-882 Cesium Magnetometers in a transverse gradiometer configuration,” explains Brock. From the measured total field data, the quasi-analytic signal (QAS) is calculated, a common technique for interpretation of magnetic data. Then a dipole modeling is calculated using the two total field data records per profile line. “This method guarantees the best possible location information, especially for small objects which are located between two profile lines,“ notes the company’s brochure.

Brock notes that “for the preliminary geophysical survey, we generally use our gradiometer together with a side-scan (Cmax CM2) on high-resolution settings for the visual verification of the target”, adding that seismic pingers are seldom used owing to their poor resolution. Other offshore techniques such as multi-beam bathymetry are in most cases not necessary.

Students observe optimum setups for surveys (for example, the distance between the two magnetometers, which is normally one metre). They also learn how to determine line spacing. “The line spacing depends on the requirements of the customer,” says Kuehl, “for example, the size of the objects which we want to detect. To locate small objects we recommend a line spacing of 10-20 m.”

It’s not only offshore where students gain useful experience—they participate in data processing too.

“For data processing, interpretation and imaging, we use Geosoft’s Oasis montaj together with the extensions UX-Detect, UX-Process and UX-Analyze,” says Kuehl. “This package is quite a complete and powerful tool. We also look forward to the implementation of the TVG workflow, which will enable us to use two total field records per profile line for a dipole inversion. For sparse profile lines, this can be an advantage against grid-based modeling.”

The surveys have their share of challenges.

“The biggest challenge is the diversity of possible UXO in the North and Baltic Seas,” says Brock. “The identification of a target after 70 years in salty water and sediment is most important for risk minimization.”

Indeed, experts estimate that ten percent of all military ordnance deployed during the Second World War has failed to explode. Danger still lurks in live naval mines from defensive barrage minefields not fully cleared at war’s end, as well as in torpedoes, land-to-sea artillery, air-delivered bombs, dumped munitions, and sunken ships.

Brock reckons this drives a need for more experts in the field. “Not only is the technical side a big challenge but it is also essential to build up a network of specialists for UXO Identification”,  he says.

Meanwhile the rapid growth of offshore wind farms continues. The European Wind Energy Association reports that installed wind generation capacity in the European Union has increased by 523 megawatts to exceed 100 gigawatts for the first time. Close to a quarter of that capacity is in Germany. The EWEA says there is enough European offshore wind farm potential to power Europe seven times over.

More and more offshore areas are being scouted for wind farms. “Many of these sites contain the theoretical risks of UXO, especially in the North and Baltic Seas,” says Brock. “There is a lot of work to do out there.”

And along with it, a lot of potential experience for students interested in UXO surveying.

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