Sequoia Scientific

Sequoia Scientific, Inc., Ocean Instruments, and Geometius Deliver Sediment Dredging Measurement System

January 20, 2021

Sequoia Scientific, Inc. (Bellevue, WA), Ocean Instruments (Fall City, WA), and Sequoia’s Dutch distributor, Geometius, have delivered a Fast Oceanographic Automated Measurement (FOAM) system for dredge monitoring.

The FOAM system is composed of a pump and winch with a fluid rotary joint, 100 m hybrid cable with hose and conductors, a tow sled with an RBR CTD and a Sequoia LISST-ABS, and a topside mounted Sequoia LISST-200X running in flow-through mode.

The sled is towed through the dredge plume, while water is continuously pumped through the hybrid cable and winch to the topside LISST-200X. This unique setup delivers particle size, concentration (from laser as well as acoustic backscatter), and other pertinent parameters from the CTD in real-time as the sled is being towed and yo-yo’ed through the dredge plume from a vessel of opportunity.  In addition to real-time measurements, this specialized system allows for co-located water samples to be collected on deck for ground-truthing sensor data.

The FOAM system itself was initially designed by Ocean Instruments for un-biased water sample collection and in-line measurements on an underway vessel. A number of systems have been delivered for moving vessel particle sampling. To name a few: Chlorophyll sampling for harmful algal blooms in the Puget Sound, suspended sediment monitoring in the Caspian Sea, and oil spill response studies in Mexico.

For the present system, Sequoia’s LISST-200X and LISST-ABS was integrated into the system and tested prior to delivery. The complete system: instrumentation, winch, hybrid cable and tow sled, together with spares, was delivered by Sequoia to Geometius. Installation, commissioning and training was originally planned on-site in Europe. However, due to the COVID-19 outbreak it was performed virtually by Ocean Instruments and Sequoia via a series of rapidly produced training videos and online training sessions.