Waterways, Maintenance Dredging, and Contaminated Sediment Removal
Dredging is essential for creation or maintenance of navigation channels, as well as for removing contaminated sediments. The contamination of water by dredged sediments is regulated in most developed, and some developing countries. In the US, EPA’s Clean Water Act article 401, Sec.103 defines the regulations. Permits are required, and monitoring requirements are spelled out in the permits. For example, see guidelines by the US Army Corps of Engineers (regulating waterways) and EPA here.
Sequoia offers 3 instruments suitable for this application. Two are submersible, permitting vertical profiles or towed use. The third is a ship-board use portable instrument.
LISST-100X is the most accurate submersible instrument for measuring suspended sediment concentration and additionally, particle size distribution (PSD). PSD is important input in models for predicting pollutant transport. It is based on laser diffraction technology.
LISST-ABS is the first major advance in technology for measuring sediments since optical turbidity. It measures sediments via very high frequency acoustic backscatter technology. It is a small, submersible instrument that provides a measure only of the suspended sediment concentration. Its attractions: it spans a wide range of sediment concentration; is more stable in calibration than optical backscatter sensors, has a better response to larger grains where optical turbidity is blind, is less affected by fouling, and is less expensive and easier to use than the LISST-100X.
LISST-Portable |XR provides a ship-deck, truly portable capability to measure concentration and PSD, similar to LISST-100X above, but it is not submersible. It’s portability is unmatched worldwide. The instrument can be easily carried from ship to ship. Only a small water sample is needed. Software provides all needed results in a printout. The instrument is based on laser diffraction technology. It is powered by an internal rechargeable battery, and has a data storage computer. No external device is needed for data collection. Ruggedized, so it can be transported by car or as carry-on bag on airplanes.