Sunset/Huntington harbour Dredging and Waterline Project
- Project Location:
Huntington Beach/Seal Beach
- Project Description:
Periodic maintenance dredging is required for safe navigation for recreational vessels within Huntington Harbour, resulting in dredge material that must be removed, creating both challenges and opportunities. The County agency and project engineers worked collaboratively with local entities, resource and regulatory agencies to maximize efficiencies to be able to utilize the dredge material for beneficial reuse on adjacent sites. In addition, the City of Huntington Beach was able to take advantage of a mobilized dredging contractor to complete a much needed water infrastructure project by installing a 16-inch waterline crossing a busy harbor channel.
A total of 197,000 cubic yards of material was removed from the harbor to restore channels. A complex sediment characterization analysis determined approximately 47,000 cy was clean sandy material suitable for nearshore at Surfside/Sunset Beach. Marsh restoration utilized 47,000 cy of finer grained material, 7,000 cy was used for cut and backfill of the waterline trench and the remaining 129,300 cy was placed at an open ocean disposal site (LA-2).
U.S. Fish and Wildlife Service manages the Seal Beach National Wildlife Refuge located on Navy property adjacent to the project. The site had been experiencing increased inundation as a result of a reduction of sediment inputs, land subsidence from subterranean fluid extraction and tectonic action and sea level rise. The elevation of the site was raised by applying 10 inches of clean sediment over the 10-acre low salt marsh project site to enhance the quality of the cordgrass-dominated salt marsh habitat and improve nesting opportunities for the federally endangered light-footed Ridgway’s rail.
A new 670 feet of 16-inch HDPW waterline was installed to improve water redundancy and reliability. Prior to this project, an older 12-inch ductile iron pipe was the only primary feed to provide adequate fire flow protection in the region. A pipeline failure or shutdown would create significant reduction to flow capacity. The new pipeline will now provide redundancy, allowing the City ample time in the future to replace the 12-inch DIP when it has reached useful life.
- Project Justification:
The dredging project demonstrates an effective and beneficial use of resources. Previous dredging cycles placed the material at an offshore open ocean site. In this project, beach compatible sediments were placed back into the littoral zone along Surfside Beach to provide nourishment to downcoast beaches. It also created and opportunity to use finer grain sediments deemed unsuitable for beach nourishment to be used for marsh restoration and to serve as a pilot project for future West Coast applications for sea level rise adaptation.
The project allowed the City a unique opportunity to take advantage of the cost of a mobilized dredging contractor to excavate a trench area under water for a waterline installation project and to piggy-back on the County’s environmental document.
- Special Circumstances:
A unique collaboration formed among the agencies on unrelated projects to maximize efficiencies, reduce project costs and conserve staff time and resource.
Obstacles include sediment compatibility issues (grain size, contaminants); biological issues (impacts to sensitive species, environmental windows) constructability (tight tolerances, containment method, equipment) site access (boat traffic, placement near small arms firing range, Naval Weapons Station property, monitoring equipment)
City of Huntington Beach received an APWA B.E.S.T. award for the Waterline Project
- Project Attachments:
- Award Citation::
A maintenance dredging project by the County of Orange to restore navigation to a recreational harbor resulted in achieving multiple benefits through partnering and outreach. The City of HB was able to successfully implement a much needed infrastructure improvement project, the City of Seal Beach achieved replenishment of beaches, and the USFWS restored marshland for critical habitat while demonstrating thin layer placement as a model for other wetlands’ response to climate change.
- Suggested Award Summary:
With the increase in environmental awareness, and in combination with more restrictive regulations, traditional solutions to the management of dredged sediments, such as dumping at sea, have become more inadequate. Alternative solutions, such as beneficial use were incorporated into the design of a regular maintenance dredging project in Huntington Harbour.