Trying to locate subsea power and communications cables has always been a difficult job. Regulations require cables be buried from several feet to several meters under the ocean bottom to prevent snagging by boat anchors and fishing trawls. The amount of overburden on a cable often means it's too deep to be located with conventional metal detection equipment. The device that has proved most effective in finding them is a cable tracker. This system has two parts, a signal injector and a probe. The injector is attached to the shore end of a line and induces a signal into one of the conductors. The probe is carried by a diver, or used from a boat in shallow water, and detects the electrical pulse transmitted through the wire.
One company that recently completed a job with help from this tool is WJ Castle and Associates, based in Philadelphia and serving the entire USA. Founder William Castle has been providing marine construction and structural engineering services for over 35 years, and has served on a number of industry boards including the International Association of Diving Contractors (IADC). Steve Gardner, a diver and engineer for the firm reports, "We were contracted by the Long Island Railroad (LIR) to find 15 subsea cables in Long Island Sound after a previous attempt by another contractor had failed to locate them. The cables ranged in diameter from 1 to 3 inches, and included power, signal and communications lines. Working closely with railroad electricians and a survey company our team utilized JW Fishers CT-1 cable tracking system to precisely pinpoint the location of all cables and tracked them with a high degree of accuracy along a portion of the bridge and through the main navigation channel under the bridge. The speed at which we were able to complete the job helped minimize channel restrictions and closures for the general public, and allowed us to provide LIR with timely information they needed to arrange future operations."
The US Navy's Underwater Construction Teams (UCT) are also using cable trackers in their projects. These construction teams were formed in 1974 when two detachments of Seabee divers were commissioned as UCT 1 and UCT 2. Their responsibilities include construction and installation of fleet moorings, pier/wharf damage assessment and repair, underwater blasting and demolition, pipeline inspection and repair, and cable laying. Both teams have purchased a quantity of Fishers CT-1 cable trackers to identifying the position of existing cables before new lines are laid down. The CT-1 also helps in pinpointing faults or breaks in the wires.
Located in the United Arab Emirates is Southern Gulf Surveys, a company with substantial knowledge and experience in Hydrographic, Topographic, and Geophysical surveys. Best known for their work in dredging and reclamation, they have provided services to many international clients. Recently the company was hired to find and track several power cables. Managing director Stephen Hart reports, "We were searching for 11 KVA, 50Hz cables and the CT-1 did its job. We got good signals both on the beach, and offshore, and found the cables 70 meters out of position and buried down 1.5 to 2 meters. They were supposed to be 15 meters apart and buried down half a meter. The client commented we've done what no one else managed to do!"
Nava19 Engineering in Thailand is having success with their CT-1 too. Owner Prajuab Riabroy reports, "We used the tracker probe to find a submarine power cable. The line was live, so we didn't need to induce a signal. The cable tracker located it very quickly, saving us time and money. On another project we induced a signal into a fiber optic cable with the Signal Injector Box; then our divers used the probe to track the cable along its entire six kilometer length. It's a good piece of equipment."