The ROV for Dam Inspection

CASE STUDY: Small submarine cameras are saving money and increasing safety during underwater operations for the U.S. Army Corps of Engineers.

Human dives are expensive and hazardous, and the costs of accidents are tremendous. Pressure differentials and penetration dives (going inside a structure) are at the top of the list for hazards and expense when working around dams. Human divers remain the most popular way to perform routine and emergency inspections, but ROVs (remotely operated vehicles) are becoming popular as an inspection tool.

Jeffrey Byars, master of Mobile District's snagboat Ros, has worked with ROVs for a decade. He saw his first ROV pictures in diving school in the early 1980s. In 1992, while attending the U.S. Army Corps of Engineers' Diving Supervisory School at Key West, Fla., Byars learned that ROVs were a real alternative to sending people underwater. The next year, shocked by the prices of commercial ROVs ($60,000 to $150,000 at that time), he began building his own.

Byars built his first ROV for about $5,000 using off-the-shelf materials - PVC pipe, trolling motors, lights, and a video camera. He got good service from his homemade ROVs, but in 2000 Mobile District bought a commercial mini-ROV called a VideoRay. It is quite different from the ROVs that explore the shipwrecks of the Titanic and Bismarck. Those cost millions of dollars, require a ship to mobilize, and need specially trained operators.

Mobile District bought the VideoRay Pro II model, which is about 14 inches long, weighs about eight pounds, and has a control unit as simple as a video game. It is equipped with two 20-watt halogen lights, and its three thrusters make it highly maneuverable with a top speed of two knots (a little more than two miles per hour).

The ROV costs about $11,500, but "Each time we use it, depending on the job, we save anywhere from a couple of thousand dollars a day to about $23,000 a day that would be spent on divers," Byars said. "It can pay for itself very quickly."

There are several ROVs in the Corps, according to Mac Wimbish, Chief of Safety and Occupational Health in Vicksburg District. There are ROVs in Pittsburgh, Seattle, Mobile, and Wilmington districts. John Day and The Dalles dams in Portland District have one each. Nashville District has an ROV on order.

Mobile District's ROV has proven itself in a range of both routine and emergency inspections. Byars had just received the ROV and had no time to familiarize with it when he was called out to inspect an accident that had holed a ship. He arrived on the scene and lowered the submersible into the water, watching a monitor showing what the ROV saw underwater.

Byars' lack of experience proved to be no problem with an ROV this easy to use. Swimming the ROV around the scene, videotaping the exploration through the camera's eye, Byars quickly identified the abandoned dredge pipeline that caused the accident. "The unit worked great, and the video is getting a lot of attention," Byars said. The shipping company named the Corps in a lawsuit, along with several others, but the video shows that the old dredge pipe was well outside of the navigation channel.

Byars also uses the ROV for more routine tasks. He can inspect underwater construction, repairs, and corrosion more often than he could with divers. He can spot problems sooner, and he avoids the usual dive hazards, paperwork, and logistics of diving operations.

For example, an erosion area in the culvert system had been discovered and repaired during a scheduled dewatering of one of Mobile District's high-lift navigation locks. Byars wanted to inspect the area frequently (three-to-six months) during operation to see if the repair stayed in place. Bids for divers to inspect the repair were $23,000 and it would be a hazardous 175-foot penetration dive. According to Byars, he can inspect the area using the mini-ROV as often as he wants, with no hazards, and at a fraction of the cost.

Byars reports using the ROV on locks, dams, and powerhouses to inspect crest gates, intake structures, and clear bulkhead and stoplog recess areas. He often slips the little submersible in the water to inspect navigation hazards, and inspect Corps boats and barges.

The ROV can't replace divers for everything. Their slow speed and the drag of their control tethers make them difficult to handle in a current.

But even when divers must go down, Byars still sometimes uses the ROV as a safety scout to spot and warn them of hazards.

"The mini-ROV industry has made great strides in providing a tool that can help avoid the hazards of diving," said Byars. "The VideoRay has provided the opportunity to inspect and prepare for diving operations, provide quality control and inspection after diving operations, and save money in the process."

(Tim Dugan of New England District also contributed to this article. Photos courtesy U.S. Army Corps of Engineers Mobile District.)

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Related Articles:

• "Mini-subs handle underwater chores", in Engineer Update, published by the US Army Corps of Engineers.
• In Commercial Diver International's November 2004 issue, "Micro-ROVs Overcome Diver Safety Concerns."
• "Alert Diver" Magazine Highlights Role of ROVs in Hazardous Environments

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Suggested Configurations

For dams, we recommend the VideoRay Pro III with:

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