WEDA Environmental Excellence Awards Focus on Contaminated Sediment Removal, Mechanical Dredging and Salt Marsh Restoration
Improving waterways through dredging and protecting the environment can be achieved simultaneously as proven by the dredging projects that were honored during the Annual Summit & Expo of the Western Dredging Association (WEDA) held in Norfolk, Virginia, in late June. The Environmental Excellence Award winners were chosen by WEDA’s Environmental Commission and presented in three categories: Environmental Dredging,
Navigation Dredging, and Mitigation and Adaptation to Climate Change. Two projects from Florida and one from Rhode Island captured the awards from ten projects submitted.
These prize winners met the stated criteria of the Environmental Commission to “promote communication and understanding of environmental issues and stimulate new solutions associated with dredging and placement of dredged materials such that dredging projects, including navigation and environmental, are accomplished in an efficient manner while meeting environmental goals.”
The 2018 WEDA Environmental Excellence Award for Environmental Dredging went to the project team for Wagner Creek and Seybold Canal Restoration Project, City of Miami, Miami-Dade County, Florida. The project team members were the City of Miami, Sevenson Environmental Services Inc., AECOM, and CH2M Hill Constructors Inc. Wagner Creek and Seybold Canal are designated by the State of Florida as an Outstanding Florida Water (OFW), that is a waterbody worthy of special protection because of its natural attributes. Despite this, Wagner Creek was deemed Florida’s most polluted waterbody.
These waterways drain directly into the Miami River, which discharges into the Biscayne Bay Aquatic Preserve and nearby Manatee Protection Zones. They have had a protracted history of dioxin contamination in Wagner Creek and sediment build-up. Their location in one of Miami’s most populated urban areas added to the numerous logistical challenges that prevented the removal of these sediments for decades. Some of these challenges included facing rigorous permitting requirements for dredging contaminated sediments in a densely populated area. Dredging activities in manatee habitats required the utmost protection and preventive measures to avoid any injury or adverse impacts to these threatened marine species.
Sevenson Environmental Services and AECOM (engineer/designer) provided a design-build service to the City of Miami to develop an effective dredge plan that allowed for these historic and vital waterways to finally be restored. A dredging solution was needed that could be permitted within 90 days from contract award. Hydraulic dredging was deemed too costly and the regulatory agencies – Miami-Dade Department of Environmental Resources Management (DERM), Florida Department of Environmental Protection (FDEP), and the U.S. Army Corps of Engineers (USACE) – would not permit for it. An innovative approach was found that allowed for a mechanical dredge solution, which complied with the strict environmental, logistical and time-constraint requirements.
According to the project team, the dredge work was performed without causing adverse impacts to the 156-aging seawall and revetment structures that are in various forms of disrepair and are vulnerable to collapse at any time. A healthy and safe work environment was maintained without incidents (60,000 safe man-hours). Associated public outreach activities successfully promoted communication between the project team, boat owners, civic groups, businesses, residents and regulatory agencies. Public meetings stimulated meaningful discussions and a deep understanding of environmental issues affecting the surrounding neighborhoods and a mixed-use urban zone known as the Health District that contains a hospital complex.
As an added value, the environmental restoration of Wagner Creek and Seybold Canal stimulated innovative solutions for protecting marine, residential and industrial communities that can be applied to future dredging work in other densely populated urban areas.
The second award was WEDA’s 2018 Environmental Excellence Award for Navigation Dredging, and it was granted to the project team for the Florida Inland Navigation District Intracoastal Waterway Deepening in Fort Lauderdale, Broward County, Florida. The project team members were the Florida Inland Navigation District, Taylor Engineering Inc., and Cashman Dredging and Marine Contracting Company, LLC.
Taylor Engineering designed, permitted and provided construction administration for a Florida Inland Navigation District (FIND) project to deepen the Intracoastal Waterway (ICWW) in Fort Lauderdale. “FIND” is a special state taxing district for the continued management and maintenance of the Atlantic Intracoastal Waterway.
Deepening took the ICWW from -10 feet Mean Low Water (MLW) to -17 feet MLW, plus 2 feet of allowable over-dredging, while avoiding environmental impacts and reducing long-term maintenance requirements. The project site, which is part of a federally authorized 403-mile navigation channel along Florida’s East Coast, lies within a densely populated, highly urbanized area. Marine traffic ranges from small recreational vessels to commercial barges and superyachts, creating a difficult work environment. In the 2.9-mile-long project area, the federally authorized project depth had become insufficient for safe navigation.
Throughout the project, the team remained conscious and considerate of all relevant environmental, technical, regulatory and social aspects that influenced the design, permitting and construction. Project phases included: a conceptual alternatives analysis that considered the channel footprint and dredging volume; dredging equipment and dewatering practices; long-term maintenance requirements; dredged material disposal alternatives; safe off-site material tr
ansport from the dredged material management area (DMMA); benefits of alternative designs to local marine industries and recreational boaters; direct and indirect impacts to seagrass and hard coral, as well as to smalltooth sawfish, manatees, and state and county park; and the engineering design of the selected alternative.
Other priorities were to cultivate effective working relationships with all stakeholders, including private citizens; industries; and local, state, and federal agencies; and to achieve design objectives, by maximizing long-term channel design benefits, avoiding natural resource impacts, and minimizing impacts that were unavoidable. Noteworthy as well was the ability to construct the project safely and efficiently, within budget and schedule, and modify the project methods and associated permit conditions when necessary. All in all, the project team was able to rehabilitate the channel in such a way that it protected and preserved the ecosystem and simultaneously improved navigation safety.
WEDA’s 2018 Environmental Excellence Award for Mitigation and Adaptation to Climate Change was presented to the project team for Ninigret Marsh Restoration Project, Rhode Island. The project team members were J.F. Brennan Company Inc., Rhode Island Coastal Resources Management Council, Save The Bay, Narragansett Bay, Town of Charlestown, Rhode Island, and Fuss & O’Neill Inc.
Sea level in Rhode Island has been rising steadily – particularly over the last 30 years – at an increasing rate. Observations by the Coastal Resources Management Council (CRMC) in many of Rhode Island’s salt marshes, including the marshes in Ninigret Pond, conﬁrm that salt marshes are beginning to drown in place. They are being converted to mud ﬂats or open water. The loss of these salt marshes translates into the loss of a natural buffer to storms and creates difficulties for the coastal protection of communities along the shorelines. Salt marshes also filter nutrients that would otherwise pollute waterways, and they absorb carbon, which contributes to climate change.
Within the Charlestown breach-way in Ninigret Pond, sand has been accumulating as it is swept in by shoreline currents. As it enters the pond, it covers important eelgrass beds and makes navigation difficult for boaters who enjoy the ponds’ resources including fishing, clamming and hunting. To resolve the problems the CRMC and their partners designed a project that used sediment dredged from the breach-way channel to build up the elevation of the adjacent marsh. The project has preserved the functions of the existing salt marsh, making it more resilient to future sea level rise and storm events, it has slowed the entry of sediment into the pond, and has improved navigation by creating a deeper breach-way channel. Bird and fish habitats and ecosystem stability have also benefited.
J. F. Brennan brought a number of innovations to bear on the Ninigret project. The RTK-GPS used for dredge positioning with live updates ensured that it was meeting the required dredge cuts. A state-of-the-art, high resolution single-beam bathymetric system (SBES) was utilized for the hydrographic survey, QA, and QC survey operations. Marsh layout included the use of an RTK-GPS rover pole to conduct land surveys and gather data points in shallow water. Drone technology was used to monitor the work but also employed volumetric capability to provide some preliminary information prior to the final survey. A marsh excavator was used to move the pipelines and assist in the grading. The marsh excavator allowed controlled discharge, increased production and final grading by monitoring elevation increasing at discharge.