ROV NEWS: SeaBotix LBV recovers sunken boat in 387ft of water
Posted on 16.02.2007 - 10:00 EST in ROV NEWS by Rons_ROV_Links
LAKE POWELL, Ariz. - San Diego Vessel Assist used a remote operating vehicle (ROV) to retrieve a sunken 30-ft. powerboat from more than 400 ft. of water in Lake Powell Nov. 11. The boat was salvaged at the behest of an insurance company after the vessel's hull allegedly split Sept. 15, killing a Colorado woman. The accident occurred in an area known as The Narrows, at the southwest portion of Lake Powell, near Page, Ariz.
"The boat was attempting to pass another vessel when it reportedly hit a wake at a high rate of speed, causing the hull to split," stated a Glen Canyon National Recreation Area release. The body of Nancy Hoff, an employee of MarineMax in Fruita, Colo., was recovered the day after the accident in 387 ft. of water by a National Park Service ROV.
The retrieval of the stricken vessel, a 30-ft. Baja, took a week to coordinate and execute beginning Nov. 4, said San Diego Vessel Assist owner Robert Butler.
To accomplish the deep-water recovery, Butler and his six-man crew purchased a SeaBotix LBV150 ROV, trailered their 24-ft. tow vessel from La Jolla to Lake Powell and rented a houseboat to use as a floating base.
Although weather cooperated for the most part, the recovery was stubborn, at best. "We located the wreck using coordinates supplied by the National Park Service's ROV," said Butler. "They were able to mark the boat within about 100 ft."
Using the GPS coordinates supplied, Butler and his crew were able to position their vessel above the wreck. They then pinpointed the wreckage on their sonar, dropped a weighted buoy line to the bottom and sent the ROV down. Using a remote control joystick, they piloted the ROV in a spiral search pattern. Visibility at the surface was about 50 ft., but only 3 to 5 ft. at the bottom. The current was negligible, Butler said. Within a half hour, the hulk's ghostly image showed up on the ROV camera. But this early success was followed by a series of letdowns, beginning with a broken shackle.
Eventually, Butler and his crew got the boat lifted about 100 to 150 feet off the bottom before the D ring pulled out of the Baja's transom. Butler believes the force of water pushing on the flat transom as the boat was being lifted upward was simply too much for the fitting to bear.
"We sent the ROV back down, and located the boat again," Butler said. The boat had settled stern-first, giving the ROV ample access to the bow eye again. "This time, we zip-tied two carabiners together to double the strength and figured out the angle and the best way to attach them," Butler said. "We got the boat all the way to the surface and attached our flotation bags to the swim step, which was through-bolted to the transom with backing plates."
With success nearly at hand, the stricken vessel's swim step suddenly tore away from the transom. The boat plummeted 400 ft. to the bottom again, nearly taking the rescue vessel with it. "The line I was using was one-half-inch diameter Spectra braided line, which has 32,000 pounds of breaking strength," Butler said. "As the boat was going down, one of the loops on the Spectra caught on a cleat on my boat. The added weight was enough to throw everything - all of our gear and all of our weight - to one side of the boat."
One of the three men on board the rescue boat fell overboard, and the entire port side dipped beneath the water briefly before the hoist line loop slipped off of the cleat. "We had a couple hairy seconds where my boat started taking on water," Butler said. "All three of us on board at the time thought 'Uh, oh, we're going to have two salvages here.'"
The following day, they relocated the wreck, recovered their still-attached hoist line and brought the 30-foot Baja to the surface. By Jack Innis