A successful depth of burial (DOB) survey of natural gas pipelines crossing the Columbia River near Portland, Oregon, hinged on the high-resolution capabilities of the NORBIT WINGHEAD i80S Long Range multibeam system. This advanced equipment, featuring integrated Applanix Oceanmaster INS/GNSS and an AML sound velocity sensor, played a pivotal role in capturing the detailed bathymetric data needed to guide and verify the sub-bottom profiling effort.
Working in tandem with the NORBIT system, an Innomar medium-100 parametric sub-bottom profiler was deployed to detect the buried pipelines and determine their depth below the riverbed. The survey area – located in a stretch of the Columbia River with depths ranging from 5 to 15 metres – was mapped using several parallel survey lines aligned with the river’s flow.
Mounted on an 8m survey vessel, the NORBIT PORTUS system was pole-mounted over the side to ensure optimal data acquisition. To complement the setup, the sound velocity profiler was used to collect accurate water column data, ensuring reliable acoustic performance.
Combined approach
This combined approach proved effective in a challenging riverine environment, with the NORBIT system providing the precise bathymetric context needed to interpret the sub-bottom data and confirm the pipelines’ positions and depths. The result was a comprehensive and dependable survey, demonstrating the value of integrating cutting-edge multibeam and sub-bottom profiling technologies.
The Innomar medium-100 system is a portable high-power and high-resolution sub-bottom profiler. It utilizes non-linear acoustics, which provides a narrow sound beam for low frequencies and very short transmit pulses without ringing. This ensures excellent vertical resolution and high ping rates, suitable for object detection. The system consists of a transducer (over-the-side, bow or moonpool mountable) and a transceiver (19” with 9 HE) containing transmitter, receiver and a control PC running MS Windows for setup, interfacing and data storage. The primary high frequency is 100kHz (for bathymetry measurements) and the secondary low frequency is user-adjustable during operation from 4–15kHz (for penetrating sediments). The sound beam is as narrow as three degrees (valid for both the high and low frequencies) and actively stabilized for transmission and reception in real time. The system can be operated in water depths of 1–2,000m. Depending on the water depth, the ping rates can be as high as 40 pings per second.
The WINGHEAD i80S LR is a compact, fully integrated multibeam survey system with an up to 600m range performance offering 0.5×0.9° beam widths at 400kHz and 1.0×1.8° at 200kHz. The sonar is frequency agile from 200–700kHz and generates 1,024 dynamically focused beams per ping. The IMU is tightly embedded within the sonar head. NORBIT’s steerable transmission technology provides full motion stabilization (roll, pitch and yaw) to ensure uniform sounding coverage in dynamic sea states. Dual swath provides up to 2,048 beams, allowing higher sounding density and reduced survey time. The system weighs 8.0kg in air and connects to a compact topside unit via a single cable, allowing rapid mobilization.
Installation
The Innomar medium-100 transducer was mounted over the side on NORBIT’s survey vessel SheHorse using the NORBIT PORTUS mounting pole. The transceiver was rapidly mobilized, connected to the INS/GNSS with a network cable and configured via the NORBIT GUI. The INS/GNSS provides RTK-corrected position, roll/pitch/heave/heading data for the sub-bottom profiler for real-time beam stabilization, heave correction and time stamping. The Innomar medium-100 requires no calibration prior to the survey. The speed of sound was set to 1,500m/s, and all given depth values are related to this velocity. The acoustic parameters were a transmit frequency of 8kHz (low frequency channel) and a signal length of 125µs (the length of a single 8kHz sinus cycle) with a recording range window of 5–25m below the transducer (providing a ping rate of about 25 pings per second).
Subsurface findings and riverbed dynamics
Three natural gas pipelines cross the Columbia River near Portland: two in parallel, each about 16 inches in diameter, and a third 14-inch line further south. The riverbed in this area is made up of sandy sediments, shaped into ripples and dunes of varying size by strong, shifting currents. These dynamic conditions lead to a highly complex and continuously changing subsurface environment.
While the parametric sub-bottom profiler offered penetration depths of up to 10m, the survey focused on the upper layers (about 1–4m below the riverbed), where the pipelines are located. The short transmit pulses of the parametric system enabled a vertical resolution of approximately 10cm – fine enough to resolve individual sediment layers and clearly identify the buried pipelines in this challenging setting.
Data processing and visualization
The acquired data was processed using ISE, Innomar’s proprietary software, which is designed for handling parametric sub-bottom profiler data. The data can also be exported to the industry-standard SEG-Y format, for further analysis in any compatible third-party processing environment.
Since the system applies band-pass filtering during acquisition, the data typically requires no additional filtering or complex seismic processing. Interpretation is straightforward: hyperbolic reflections – commonly associated with buried objects such as pipelines – are visually identified by the operator, relying on the clarity of the raw acoustic signal rather than automated detection algorithms. The detected hyperbolic reflectors are picked with a mouse and exported as XYZ ASCII data, which is easy to import into any GIS application or third-party software for mapping or visualization. QPS Fledermaus software was used to generate a 3D representation of the acquired MBES dataset, the vertical 2D seismic sections and the picked pipelines. Pipeline diameters are not shown to scale in the 3D view, just the top of the pipelines, so the hyperbolic features in the seismic sections remain visible.
Conclusion
The Innomar medium-100 parametric sub-bottom profiler proved to be a highly effective tool for measuring the DOB of pipelines and cables. Designed with practicality in mind, the system is compact and portable, making it well-suited for deployment from small survey vessels using over-the-side mounting.
Its flexibility extends beyond physical setup. The profiler integrates easily with existing NORBIT multibeam systems or can be paired with standalone INS/GNSS units, allowing it to fit seamlessly into a range of survey configurations. What also sets the system apart is its efficient data workflow, as there is no need for extensive seismic processing.
More information:
norbit.com/product/norbitwinghead-i80s/
innomar.com/innomarflyer/innomar-medium-100.pdf