Riverbank Restoration and Stabilization
Trihydro restored and stabilized two segments of eroded riverbank, providing construction, revegetation, pollution prevention, and regulatory compliance services. Despite encountering several unanticipated obstacles, Trihydro completed construction more than 7 weeks early on one segment and more than 10 weeks early on the other segment.
This project focused on the environmental restoration and stabilization of two segments of eroded riverbank along the St. Jones River in Delaware. Trihydro was the prime contractor for the project team.
The scope of services performed by the Trihydro team for the riverbank segments included:
- Construction and contract management
- Clearing dense vegetation and small trees
- Placing Soil Erosion Controls (SECs) and pollution prevention measures to protect St. Jones River water from erosion and runoff during construction
- Installing toe revetment
- Backfilling and grading
- Placing topsoil and constructing live soil lifts
- Planting and seeding
- Conducting final inspections
- Preparing a summary report with as-built drawings
Work was conducted around significant tidal variations in river elevation and seasonal conditions that prevented construction during winter months.
For one of the segments, Trihydro expedited work and prevented further riverbank degradation through the initial implementation of minor surface grading, fill, and installation of coconut netting during the initial, winter period of non-construction. Based on surveys of previously planted areas, Trihydro proposed and implemented no-cost quality changes in the bank protection design by substituting potted plants for plant bundles and live-staking indicated in the plans. Implementation required negotiation of species and planting program changes with representatives from the Delaware Department of Natural Resources and Environmental Control. Even with these negotiations and changes, construction was completed 51 days ahead of schedule.
For the other segment, several unanticipated obstacles were encountered during the clearing and grubbing, including a large amount of concrete. The concrete was excavated, stockpiled on site, and hauled off site for appropriate disposal at no additional cost. The crew discovered a 15-inch stormwater outfall pipe, which was not designated in the plans. A no-cost modification was made to the work plan to taper the bank fill around the outfall pipe and add rip rap protection in front of the outfall to dissipate the water flow as it enters the fringe marsh. Despite changed conditions, construction was completed within budget and 75 days ahead of schedule.
