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Turbidity Monitoring for Naval Station Waterfront Improvements
ESS was contracted by Haskell, as part of a design-build project team for the US Coast Guard (USCG) and the US Navy, to provide turbidity monitoring during in-water improvement work at Naval Station Newport (NAVSTA). The improvement work was completed along the bulkhead between Piers 1 and Pier 2 at the NAVSTA facility, located in Coddington Cove, Newport, Rhode Island.
ESS developed and implemented a Navy- and EPA-approved turbidity monitoring plan to verify that the turbidity curtain was effectively minimizing the transport of suspended sediments outside the work area.
The proposed improvement work, including dredging and pile removal along the bulkhead, was anticipated to impact water quality by causing an increase in turbidity and suspended sediments. To contain suspended sediment and minimize transport outside of the work area, turbidity curtains were positioned around each active work area. The Environmental Protection Agency (EPA) also required additional monitoring during in-water activities.
ESS project scientists deployed three buoy-mounted water quality systems within Coddington Cove prior initiating dredging activities. Each buoy-mounted system was equipped with three water quality sondes containing turbidity sensors. Each buoy was also equipped with a mounted solar panel to power the associated monitoring equipment, as well as applicable warning lights and markers, as required by the USCG and Navy.
Two buoy systems were positioned approximately 300 feet from the turbidity curtain surrounding each work area. An additional location, positioned away from the influence of the in-water improvement work, was also monitored to characterize background conditions and provide the basis of comparison to the locations immediately outside of the turbidity curtain.
Real-time monitoring of conditions and turbidity measurements were recorded every 10 minutes and data was transmitted via cellular telemetry every 30 minutes to a secure webserver. Data from the monitoring locations, as well as the reference location, were monitored continuously for the duration of the in-water improvement work.
The project is located in Rhode Island Class SB waters, which have a turbidity standard of 10 NTU (RIDEM 2010). The monitoring system was configured to provide automated alarm notifications via text messages or email when the turbidity exceeded a predetermined limit (10 NTU).
If the turbidity value for the station located immediately outside the turbidity curtain exceeded the 10 NTU turbidity standard for two consecutive hours, ESS notified Haskell and the dredging contractors to assess the activity causing the exceedance. ESS also coordinated appropriate action to minimize the transport of suspended sediments outside the work area. Mitigation actions included inspecting the integrity of the curtain, temporarily ceasing work, and/or revising work procedures.
If the turbidity standard was consistently exceeded over a 24-hour period, additional turbidity measurements were collected from a vessel using a direct reading water quality meter at the monitoring locations outside of the turbidity curtain, as well as the reference location. If, after verifying the measurements, compliance could not be re-established within 48 hours, EPA and the Rhode Island Department of Environmental Management (RIDEM) were to be notified to discuss an alternative course of action.
ESS and the project team successfully designed, implemented, and conducted turbidity monitoring during in-water improvement work, and government officials marked the completion of NAVSTA waterfront upgrades in December 2015. By utilizing state-of-the-art technology, ESS was able to develop a cost-effective approach for monitoring in-water construction activities in support of Navy and USCG missions.