Delineation of pipeline river crossing using cable and pipe locator with real-time differential GPS
- Golder Associates Ltd., Burnaby (Canada)
The location and depth of cover over pipeline river crossings must be checked periodically to ascertain that the pipeline remains undisturbed and adequately covered. We have developed a technique to determine pipeline plan location and depth of cover utilizing a combination of electromagnetic detection and echosounding with real-time navigation, in this case differential GPS. The technique offers an alternative to acoustic location methods where small pipe size or the presence of acoustically opaque sediments prevent pipe detection. In addition, the technique can be used in fast-flowing rivers or in heavy marine traffic where anchoring is an unlikely option. We have successfully applied the method to locate and profile a 168 mm steel pipeline crossing under the Fraser River, near Vancouver, Canada. Site conditions consisted of a 250 m wide river with 3-5 knot current. The 168 mm steel pipeline was buried in silts from 2-6 m thick below water up to 9 m deep. In addition, approximately 80 m of the river surface was permanently covered by log booms and hence inaccessible by boat. Initial attempts to locate the pipe using an acoustic sub-bottom profiler were unsuccessful. The 3.5 kHz system used did not provide sufficient penetration to delineate the pipe, probably due to the presence of biogenic gas in the river-bottom sediments. A Radiodetection{reg_sign} cable and pipe locator system was used to establish shoreline and shallow water locations. Unfortunately river currents and marine traffic prevented accurate location and depth determination using standard location techniques. The development of digital pipe locators with RS-232 interfacing permitted us to develop a technique utilizing simultaneous recording of digital magnetic field strength and real-time differential GPS location data. The Radiodetection{reg_sign} transmitter was connected to a riverside pipe valve.
- OSTI ID:
- 381494
- Report Number(s):
- CONF-960477--
- Country of Publication:
- United States
- Language:
- English
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