A 2001 archaeological survey by BP and Shell prior to construction of a natural gas pipeline confirmed discovery of U-166 about 45 miles off the Louisiana coast.

Petroleum companies operating in the Gulf of Mexico’s outer continental shelf routinely provide the government with sonar data for areas with potential archaeological potential value.

Several federal agencies review oil and natural gas-related surveys every year, and over the years the data have revealed more than 100 historic shipwrecks in U.S. waters. In 2001, scientists at the Minerals Management Service noted that “a German submarine definitely got our attention.”

During World War II, U-boats prowled the Gulf of Mexico to disrupt the vital flow of oil carried by tankers departing ports in Louisiana and Texas.

In just one year, the Kriegsmarine sank 56 Allied ships, including 17 tankers, while losing only one submarine – the Unterseeboot 166.

German submarine predations so threatened the war effort that American government and industry responded with the longest petroleum pipeline project ever undertaken, building the “Big Inch” and “Little Big Inch” from East Texas to Illinois, and as far as New York. See WW II Big Inch and Little Big Inch Pipelines.

But for the U-166, the war was over. Its final resting place remained a mystery for almost 60 years.

The last victim of the U-166 was the passenger freighter Robert E. Lee, sunk by a single torpedo on July 30, 1942, while on its way to New Orleans. Her Naval escort ship, PC-566, rushed in to drop ten depth charges. The U-166 was believed to have escaped. It did not.

Commissioned on March 23, 1942, U-166 today is a war grave in the Gulf of Mexico.

Finding U-166

In 1986, a Shell Offshore vessel using a deep-tow system of the day recorded two close wrecks about 45 miles off the Louisiana coast in 5,000 feet of water.

Thought to be the Robert E. Lee and cargo freighter Alcoa Puritan, it was May 2001 before an autonomous underwater vehicle (AUV) using side scan sonar revealed the U-166. The lost World War II submarine was separated from Robert E. Lee by less than a mile on the sea floor.

The U.S. petroleum industry remains a principle user of advanced underwater technologies for seafloor mapping.

The AUV, which required no cable connection to its mother ship, found the Alcoa Puritan 14 miles away. Learn more about the petroleum industry’s offshore robotics in ROV – Swimming Socket Wrench.

Six other World War II vessels have been discovered in the course of Gulf of Mexico oil and natural gas surveys.

As a result of the U-166’s discovery, BP and Shell altered their proposed pipeline to preserve the site and government archaeologists notified the U.S. Navy Historical Center of the discovery. “They, in turn, notified the German Embassy and military attaché,” the MMS article explains. “Since the remains of the U-166’s 52 crewmen are still on board, the German government has declared the site to be a war grave and has requested that it remain undisturbed.”

Editor’s Note – Since 2011, the Minerals Management Service has become the Bureau of Ocean Energy Management and the Bureau of Safety and Environmental Enforcement.
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