Turbidity Alert System - Ashtabula River DredgingProject Overview
The Ashtabula River is located in northeast Ohio and flows into Lake Erie's central basin at the city of Ashtabula. From the 1940's to the late 1970's, the area surrounding the mouth of the river experienced significant development from various industries. Throughout this time frame, unregulated discharges into the river and mismanagement of hazardous waste from local industries prompted the International Joint Commission to label the river an Area of Concern (1).
In 2006, a large US consulting firm was contracted to dredge contaminated sediment out of the river. The consulting firm chose NexSens buoy-based cellular data logging systems to monitor this process and ensure that the contaminated sediment levels do not exceed specified ranges.
System Description
Surrounding the dredging operation, three NexSens data buoys were strategically located to monitor the suspended solids generated from dredges. The rugged buoy platforms are constructed of an inner core of cross-linked polyethylene foam with a tough polymer skin coating. The topside instrument mast houses the cellular data logger, solar panel, antenna and navigational beacon. Top and bottom mounted stainless steel eye-nuts accommodate moorings and lifting rigs for quick and easy deployments.
YSI 600 OMS (Optical Monitoring System) sondes with optical turbidity probes were chosen to sense turbid water. The YSI 6136 turbidity probe features a self-cleaning wiper to provide accurate turbidity measurement in fresh, brackish, and sea water. Before taking a reading, the mechanical wiper cleans the sensing optics to ensure that the measurement is not affected by fouling sediment debris. All YSI 6-Series instruments facilitate direct connection to NexSens data loggers via MS-8 connector on the bottom of the NEMA 4X enclosure.
Further upstream, a remote stream gaging system was installed to monitor changes in river water level. This system consisted of a YSI 600LS vented level sonde connected to a NexSens 3100-iSIC cellular data logging system.
During dredging operations, all data from the NexSens systems is sent in real-time to a PC running NexSens iChart software. iChart serves as the centralized database for all incoming data. In addition, it features 'Alarm Notification' to quickly notify project members if turbidity levels exceed a specified range.
The NexSens WQData web datacenter is automatically generated from iChart software and provides an online interface for viewing data. The datacenter allows project members to experience project information and data, as well as facilitate direct communication using the online forum.
With this system in place, dredge operators can be notified immediately of high turbidity levels and slow down or alter the dredging operation until levels fall back within range. Additionally, the historical data can be tracked and correlated to dredge operations so that the consulting firm can improve upon future dredging operations.
(1) Source: "Great Lakes Area of Concerns (AoCs): Ashtabula." U.S. EPA. URL: http://www.epa.gov/glnpo/aoc/ashtabula.html | NexSens 1001 | iChart software | NexSens WQData-6 | Annual data hosting package for up to 6 field sites, additional site expansion available | NexSens MB-300 | Monitoring buoy, 30" dia. polymer-coated foam hull, 300 lb. buoyancy | Carmanah 501-A15 | LED Beacon with solar power, 15 flashes per minute (064), amber | NexSens 3100-iSIC | iSIC data logger with cellular modem telemetry | NexSens A20 | Solar power kit, 5-watt. Includes solar panel, regulator, 8.5 A-Hr battery & watertight enclosure | NexSens A49 | High gain antenna, cellular frequency, tri-mode, 2 dBd | NexSens A36 | RF cable, micro-loss, 6' | YSI 600-01 | YSI 600OMS V2 Sonde with temperature/conductivity sensor | YSI 6136 | Turbidity sensor with self-cleaning wiper | YSI 6091 | Field cable, 25 ft. | NexSens 3100-iSIC | iSIC data logger with cellular modem telemetry | NexSens A55 | Pole/wall mounting kit | NexSens A38 | Ground kit | NexSens A22 | Solar power kit, 20-watt | NexSens A49 | High gain antenna, cellular frequency, tri-mode, 2 dBd | NexSens A36 | RF cable, micro-loss, 6' | YSI 600-10 | YSI 600LS Sonde with temperature & shallow vented level sensor | YSI 6191 | Vented field cable, 25 ft. |
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