Guest Column: Eastern Penobscot Bay Hydrographic Survey Completed

Fugro recently concluded its second consecutive field season in Penobscot Bay. Working under contract to the National Oceanic and Atmospheric Administration (NOAA), the company collected 89 square nautical miles of hydrographic survey data over a period of three months to update navigational charts in the region.

Having successfully surveyed western Penobscot Bay during the summer of 2016, this summer’s eff orts were focused on the bay’s eastern region. “It is without a doubt one of the more difficult projects we’ve ever been assigned by NOAA,” said Dean Moyles, senior hydrographer and project manager for Fugro.

In addition to a notoriously rugged coastline, Moyles pointed to the high density of commercial activity in the region as challenging factors in this year’s survey. “We were able to test the waters, so to speak, last year while working on the western side of the bay. Our experiences there were incredibly helpful to planning and executing a successful survey in the more congested waters of the eastern Penobscot this year,” Moyles said.

From Fugro’s perspective, project success meant conducting its surveys safely and with minimal impact to local fishing operations. This was achieved in large part through careful collaboration with the Maine Lobstermen’s Association (MLA) prior to and during survey activities. As with the 2016 survey, the company started its work in the air, using a small aircraft equipped with LIDAR technology to identify uncharted rocks, shoals, and other obstructions in advance of the vessel-based surveys.

For the marine portion of the project, Fugro used two jet-drive catamarans, the R/V Th eory and the R/V Westerly, with two multibeam sonars mounted on each boat. Typical hydrographic surveys use just one sonar system per vessel. A dual-mount setup on this project allowed Fugro to cover more area per survey line, which significantly reduced the overall time required.

The company communicated closely with the MLA throughout the mission, providing weekly updates from the surveyors in the field directly to MLA executive director Patrice McCarron. These updates highlighted the specific work areas for both vessels for the upcoming week to help ensure the lobstermen had ample notice of any potential survey work near their gear. Moyles noted many positive interactions between the survey crews and local fishermen throughout the summer. “We really appreciated their understanding and cooperation,” he said. Based on the high concentration of activity in the survey area, the company spent more time this year than last navigating in and around fishing gear. “We did have snags that we carefully untangled, but we caused no real damage to fishing equipment, and for that we are grateful,” Moyles said.

While data processing and reporting for the survey season is not yet finished, Fugro reports a decidedly productive survey, having verified over 3, 100 charted features and having issued 89 “dangers to navigation” areas for review by NOAA. This large number of “dangers to navigation” is due both to the nature of the area, which comprises a large number of islands, rocks, shoals, and drying reefs, as well as to the age of existing nautical charts, which were created between 1875 and 1911.

Surveys at that time were conducted using lead lines. With this technique, ropes weighted with lead were lowered to the seafloor to allow for manual depth readings. “The methodology was state-of-the-art at the time and allowed for accurate measurements. However, due to the time required to make these measurements, relatively few readings over a given survey area were acquired,” Moyles explained. In a location as dynamic as Penobscot Bay, that meant many features and hazards were left unmapped.

Today, multibeam sonar makes it possible to acquire bathymetric measurements over the entire seafloor, thus minimizing the chance of uncharted shoals or other hazards to navigation. Multibeam data collected by Fugro this summer is now being processed in the company’s Houston data center. Upon completion, final data and reports will be sent to NOAA for final review and the agency will then make updates to all applicable electronic charts. It is yet unknown whether additional work in the region will be prioritized for NOAA in 2018. Over the past two years there has been good progress in making these Maine waters easier and safer to navigate and NOAA acknowledges there is more work to be done. When the time comes to continue updating nautical charts in this region, Fugro is ready to take on the challenge.