Overview
When Moffatt & Nichol brought the company’s engineering expertise to recent marsh-restoration projects along Alabama’s Gulf Coast, they selected In-Situ equipment for real-time turbidity monitoring during dredging operations.
Challenge
Depending on where you are in the world, if you’re running a coastal dredging operation, you’re most likely required to monitor turbidity in order to keep total suspended solids levels within prescribed limits and minimize damage to aquatic life within the dredge zone.
For international engineering firm Moffatt & Nichol, two recent projects along the heavily developed and ecologically fragile Alabama Gulf Coast required continuous water quality data collection in order to meet regulatory requirements and avoid costly project delays.
For international engineering firm Moffatt & Nichol, two recent projects along the heavily developed and ecologically fragile Alabama Gulf Coast required continuous water quality data collection in order to meet regulatory requirements and avoid costly project delays.
Solution
Dr. Don Blancher, Supervisory Coastal Scientist with Moffatt & Nichol, led monitoring efforts for Alabama’s Lightning Point and Graveline shoreline restoration projects.
The Lightning Point project in Bayou la Batre, a boat-building hub and the state’s seafood capital, entailed construction of a living shoreline with about 42 acres of new marsh, tidal creeks and upland habitat to support a wide variety of fish, shellfish and birds, including an oyster nursery.
To monitor turbidity, temperature and salinity during dredging operations, Blancher and his team deployed an Aqua TROLL 500 Multiparameter Sonde and a VuLink telemetry device on a well-positioned piling just outside the project’s mixing zone. For the better part of a year, the team used In-Situ’s HydroVu data services to access water quality data in real-time.
“State requirements are that during dredging operations you can’t be more than 50 NTU above background,” says Blancher. “We had the continuous data from the Aqua TROLL and VuLink, a local university had a unit some distance away that we used for background, and we used a roving unit to monitor the plume by boat. So, that gave us everything we needed to make sure we were in compliance.”
Google Earth - Bayou le Batre image
Moffatt and Nichol used dredged material to construct more than 40 acres of marshland near Bayou le Batre, along the Alabama Gulf Coast.
A second shoreline project in the Gulf was in Graveline Bay, near Dauphin Island. There, Moffatt & Nichol replaced eroded marsh with a cluster of sandy mounds. The newly constructed marshland restores habitat and helps protect the homes behind it from northwest winds that eat away at the shoreline.
“We’ve already heard from some homeowners that this was the first year they haven’t had to bring in fill to replace what was lost,” says Blancher.
For this project, Blancher and his team installed an Aqua TROLL 500 and a VuLink on a residential pier just west of the turbidity curtain and east of a nearby oyster farm. VuLink transmitted data from the sonde back to Blancher’s office through HydroVu, making it easy to correlate with grab samples in the lab, satellite images and other data to make sure they have a good handle on suspended solids content.
With new plantings now taking hold on the crafted landscape, Blancher continued to collect data from the sonde months after the project began, securing a continuous record of conditions in the area.
Google Earth – Graveline Bay image:
In Graveline Bay, near Dauphin Island, newly constructed marsh habitat offers added protection from intense weather for homes along the coast.
The Lightning Point project in Bayou la Batre, a boat-building hub and the state’s seafood capital, entailed construction of a living shoreline with about 42 acres of new marsh, tidal creeks and upland habitat to support a wide variety of fish, shellfish and birds, including an oyster nursery.
To monitor turbidity, temperature and salinity during dredging operations, Blancher and his team deployed an Aqua TROLL 500 Multiparameter Sonde and a VuLink telemetry device on a well-positioned piling just outside the project’s mixing zone. For the better part of a year, the team used In-Situ’s HydroVu data services to access water quality data in real-time.
“State requirements are that during dredging operations you can’t be more than 50 NTU above background,” says Blancher. “We had the continuous data from the Aqua TROLL and VuLink, a local university had a unit some distance away that we used for background, and we used a roving unit to monitor the plume by boat. So, that gave us everything we needed to make sure we were in compliance.”
Google Earth - Bayou le Batre image
Moffatt and Nichol used dredged material to construct more than 40 acres of marshland near Bayou le Batre, along the Alabama Gulf Coast.
A second shoreline project in the Gulf was in Graveline Bay, near Dauphin Island. There, Moffatt & Nichol replaced eroded marsh with a cluster of sandy mounds. The newly constructed marshland restores habitat and helps protect the homes behind it from northwest winds that eat away at the shoreline.
“We’ve already heard from some homeowners that this was the first year they haven’t had to bring in fill to replace what was lost,” says Blancher.
For this project, Blancher and his team installed an Aqua TROLL 500 and a VuLink on a residential pier just west of the turbidity curtain and east of a nearby oyster farm. VuLink transmitted data from the sonde back to Blancher’s office through HydroVu, making it easy to correlate with grab samples in the lab, satellite images and other data to make sure they have a good handle on suspended solids content.
With new plantings now taking hold on the crafted landscape, Blancher continued to collect data from the sonde months after the project began, securing a continuous record of conditions in the area.
Google Earth – Graveline Bay image:
In Graveline Bay, near Dauphin Island, newly constructed marsh habitat offers added protection from intense weather for homes along the coast.
Results
"The system has worked well,” says Blancher, adding that fouling is always the biggest challenge with long deployments. “We had the sonde with the wiper and the copper restrictor. But at Lightning Point we had a colony of barnacles that grew right over the sensors. Fortunately, with the data coming in through HydroVu, we could see that the signal was getting degraded, so we went out there and took care of it.”
Blancher says that with good data at their fingertips, the firm was able to maintain compliance through both projects; the only time they had to pause operations was to reinstall a turbidity curtain that had been dislodged.
Dredging to reshape and restore shorelines and rebuild lost or degraded coastal habitat delivers significant benefit but not without environmental risk. As these projects become more common and funding for them increases, effective water quality monitoring during dredging operations will be essential.
With new projects afoot in the Northeast U.S. and elsewhere, Moffatt & Nichol have the expertise and the instrumentation they need to tackle new design challenges and the regulatory hurdles that accompany them.
Blancher says that with good data at their fingertips, the firm was able to maintain compliance through both projects; the only time they had to pause operations was to reinstall a turbidity curtain that had been dislodged.
Dredging to reshape and restore shorelines and rebuild lost or degraded coastal habitat delivers significant benefit but not without environmental risk. As these projects become more common and funding for them increases, effective water quality monitoring during dredging operations will be essential.
With new projects afoot in the Northeast U.S. and elsewhere, Moffatt & Nichol have the expertise and the instrumentation they need to tackle new design challenges and the regulatory hurdles that accompany them.
fearured products
Aqua TROLL 500 Multiparameter Sonde$1,495.00Pricing only valid in the U.S.A fully customizable five-port multiparameter sonde with capacity for four interchangeable sensors and an antifouling wiper. A smartphone interface delivers accurate data and enables simplified calibration, panoramic data view and report creation. Ideal for spot-checking and profiling applications when used with a Wireless TROLL Com or for long-term monitoring with VuLink telemetry.
VuLink$895.00Pricing only valid in the U.S.VuLink® cellular telemetry makes remote monitoring practical, secure and effective, for less than you’d expect.
HydroVu Data Services$0.00Pricing only valid in the U.S.Interface with In-Situ instruments and telemetry for secure access to your data, when and where you need it.
