Multibeam Hydrographic Surveys Accurately Assess Reservoir Storage Capacity
Substructure has completed a series of high-resolution multibeam and sub-bottom profile surveys of drinking water reservoirs, as commissioned by Pennichuck Water Works of Merrimack, NH. During May 2011, Substructure conducted the hydrographic survey work in Nashua, NH, on Bowers Pond and Harris Pond, reservoirs created in the late 1800’s by damming portions of Pennichuck Brook. The surveys are being used to update Pennichuck’s engineering drawings and to provide the water company with an accurate assessment of available water-storage capacities.
All of the multibeam and sub-bottom profiling survey operations were conducted aboard Substructure’s portable survey barge, a stable marine platform configured by the firm to meet strict environmental standards for operations within a drinking water storage impoundment (Figure 1).
Figure 1
“Substructure provided us with high-resolution multibeam surveys that give a highly detailed view of below water topography, enabling us to make more informed water management decisions moving forward,” said Pennichuck Water Works Chief Engineer John Boisvert. “These data allow us to accurately update our existing engineering drawings and storage capacity estimates, and to better plan for future enhancements and water quality monitoring needs at both ponds. Most of our previous depth information for these ponds was based on original topographic survey work, prior to inundation around 1895.”
Results from the multibeam data clearly depict the complex bathymetry within the ponds and also reveal that the channel of Pennichuck Brook remains a prominent feature throughout the length of both ponds (Figure 2). Prior to this survey, it was thought likely that sedimentation had filled in much of the former meandering brook channel. A variety of data products have been created by Substructure to clearly depict the results of these surveys and to enable Pennichuck Water Works to evaluate the data from a variety of perspectives.
Figure 2
The primary hardware components for the survey operations were an R2Sonic 2024 multibeam echosounder, an Applanix POSMV 320 vessel position and orientation system, and a Knudsen 3212 Chirp sub-bottom profiling system. A local Global Positioning System (GPS) base station was established over a control point on Harris Dam to provide Real-Time Kinematic (RTK) DGPS correctors to the survey barge.
Previous article: Substructure Fabricates Sonar Mounts for Army Corp
Next article: Substructure Awarded Engineering Work at Manufacturing Power Plant
