Objective

Acquire accurate multibeam and sub-bottom profile data within drinking water reservoirs to support comprehensive engineering and water-management projects.

Highlights

• Developed and implemented a robust and portable multibeam survey platform, compliant with American Water Works Association environmental standards

• Acquired full-bottom-coverage multibeam data that enabled detailed comparisons with pre-inundation survey data

• Adhered to rigorous survey methods that produced bathymetric data that satisfied International Hydrographic Organization (IHO) Special Order Standards

Project Details

Substructure was selected to conduct a series of high-resolution multibeam and sub-bottom profile surveys of drinking water reservoirs managed by Pennichuck Water Works of Merrimack, New Hampshire.  These surveys were the first true bathymetric data that Pennichuck had received since the pre-inundation surveys, which were conducted over 100 years ago.  For Substructure to collect survey data at these drinking water facilities, a new survey vessel had to be developed.  A stable marine barge was configured to meet strict environmental standards, including the use of an electric motor for propulsion and a propane-powered generator to provide electrical power to the survey equipment.

Survey equipment used for these multiple multibeam surveys included an R2Sonic 2024, an Applanix POSMV 320 vessel position and orientation system, and a Knudsen 3212 Chrip sub-bottom profiling system.  A local GPS base station was also established to provide real-time kinematic (RTK) differential GPS.

The survey data provided to Pennichuck Water Works inform improved water-management decisions and enabled engineers to update storage capacity estimates.  The high-resolution multibeam data was also used to help conduct water-quality monitoring studies, as well as to assist with planning for a dam repair.