Hydrographic surveys reveal detailed images of offshore industry wreckage
It might surprise some companies engaged in the maritime industries to learn that many official nautical charts of US territorial waters have not been updated for 60 years or more. What’s more, navigation specialists at the National Ocean and Atmospheric Administration (NOAA) estimate that a significant segment of navigable waters off the Gulf Coast have not been surveyed even since the 1800s.
Having to refer to such outdated charts in some cases exposes users to significant risk potential. Some digital charts covering sections of the outer continental shelf along the East and Gulf coasts do not accurately pinpoint shipwrecks or offshore petroleum industry debris left on the ocean bottom by hundreds, perhaps thousands of heavy gales and hurricanes that have plagued those regions for decades.
But new hydrographic survey technology is being applied to aid updating of official navigational charts, although NOAA admittedly acknowledges that the job will take many years to complete. One of the principal companies involved in this massive chart revision effort is David Evans and Associates Inc. (DEA), a 32-year-old engineering firm with headquarters in Portland, Oregon.
A newly created subsidiary, David Evans Marine Sciences Inc., based in Vancouver, Washington, is heading up one of eight contract hydrographic survey teams engaged in a $250 million project to assist NOAA in assuring safer navigation in more than 3.4 million square nautical miles of US territorial waters.
The company is nearing completion of its role in Gulf Coast debris surveys of near-shore areas off Louisiana and Alabama, a $44 million project mandated by Congress to identify the impact of the 2005 hurricanes, Katrina and Rita.
Multibeam sonar map of the same collapsed derrick.
David Evans Marine Sciences uses small boats equipped with side-scan sonar and multi-beam bathymetric sonar technology, global positioning systems, and motion sensors to create underwater maps of the area ravaged by the two hurricanes, whose combined damage to offshore petroleum infrastructure alone is estimated to have totaled some $17 billion.
Use of autonomous vessels
Jon Dasler, DEA vice president and director of marine sciences, said the sea craft used in the Gulf survey ranges from small boats towing a side-scan sonar towfish to autonomous vessels equipped with a side-scan sonar as small as a sea kayak that run autonomously over pre-programmed survey lines. Combined, the vessels have surveyed assigned segments of the Gulf bottom ranging from extremely shallow water (4-ft [1.2-m] curve) out to some 100 ft (30 m) of water.
Using side-scan sonar to identify contacts protruding above the sea floor, along with multi-beam bathymetric sonar for detailed mapping of significant contacts, the company contributed hundreds of detailed images of sunken vessels of all sizes, as well as wrecked drilling and production platforms and related equipment. Also detailed were points at which storm-related surge currents and seafloor avalanches unearthed buried pipelines or where multiple pipelines were heaped into a spaghetti-like jumble.
“The state-of-the-art in ocean bottom survey technology demonstrates itself in extreme accuracy in detailing both the image and elevation of objects of interest on the ocean floor,” Dasler said. “The multi-beam image is three-dimensional, which allows us to depict the distance between the top of a debris item and the water surface at Mean Lower Low Water, the tide level used for chartering.”
According to Dasler, such high-resolution mapping ultimately will benefit a wide range of users, from sport and commercial fishermen to shrimpers to maritime interests, as well as to most segments of the offshore petroleum industry. The need by vessels of all types to avoid obstructions left by storms, of course, is a basic driver for mapping them accurately, he said.
Don Fusilli, president and CEO of David Evans Marine Sciences, said reliance on government contracts has served the firm well, but the company is diversifying its client base, pursuing projects in the private sector, as well.
Seeking private contracts
According to Fusilli, private companies can effectively take advantage of contracting hydrographic surveys of their own damaged or lost equipment immediately after storms, not only for insurance purposes, but also to help determine whether the equipment must be removed as a navigational hazard or is perhaps even salvageable.
The company is modifying its array of equipment for use in autonomous vessel surveys to accommodate customers engaged in deep and ultra deepwater marine construction and petroleum industry projects, said Fusilli.
The parent company has more than 25 offices in seven state and nearly 1,100 employees, he pointed out. Its underwater surveys have assisted in production of big-budget motion pictures in the 1990s (Waterworld), have mapped ancient underwater pyramids in Guatamala, have located debris from a former bombing range at Pyramid Lake in Nevada, and have assisted in helping to determine an environmentally sound path for bringing electricity to the San Juan Islands off the coast of Washington.
The company’s work in hydrographic surveying and other marine services has grown steadily for the last 20 years, said Fusilli. The DEA staff has conducted hydrographic surveying projects in coastal areas and inland waters throughout the US and in the Caribbean, he said, adding that the founding of the David Evans Marine Sciences subsidiary demonstrates the growing demand for increased accuracy in subsea imaging.
