Turbidity Dredge Monitoring

Project Overview

A large Midwest consulting firm was contracted to remove contaminated sediments from an embayment of Lake Michigan. As part of the regulations, the firm was required to monitor turbidity at two depths and five locations surrounding the dredge in order to ensure that contaminated sediment levels did exceed a specified range in the water. If sediment levels did fall outside of the range, the dredge operator would have to be notified to slow down or alter the dredging operation.

As an embayment of Lake Michigan, with significant wave action and harsh weather conditions, the dredge site offered significant challenge for deploying and maintaining the monitoring sensors. The consulting firm selected Fondriest Environmental, Inc, a sensor and environmental consulting company with offices in the Great Lakes region. Fondriest engineered a buoy based systems with real-time data telemetry.

System Description

Fondriest Environmental application engineers configured and setup a notification system that met the requirements of the consulting firm?s specifications. Using the NexSens MB-400 environmental monitoring buoy, NexSens 4100-iSIC data loggers with radio telemetry and D&A Instruments OBS3 turbidity sensors, five data buoys were strategically anchored around the dredge. The OBS3 sensors were set to measure turbidity at both 5 and 10 meter depths.

During the dredging operations, this data was collected at constant intervals and sent through license-free, spread spectrum radio to the base station, where turbidity levels were being closely monitored in real-time using NexSens iChart software. When turbidity exceeded the regulatory limits, the dredge operator was immediately notified using a handheld radio.

Thanks to Fondriest application engineers and the NexSens real-time turbidity monitoring system, the contractors were able to safely and successfully dredge the embayment without incident.