Nationwide Permit 55 authorizes the installation of structures in marine and estuarine waters, including those anchored to the seabed overlying the outer continental shelf, for seaweed mariculture activities. The permit covers the placement of buoys, long-lines, floats, anchors, rafts, racks, and similar equipment necessary for the cultivation of various seaweed species. This permit also allows for the inclusion of bivalve shellfish mariculture (such as oysters or mussels) on the same or nearby structures, provided the shellfish production is part of an integrated multi-trophic mariculture system. The scope is limited to the structures themselves and does not authorize discharges of dredged or fill material into waters of the United States, nor does it cover land-based support facilities like processing plants.
The 2026 reissuance of NWP 55 maintains the same national terms and conditions as the version originally issued in 2021. The Corps reevaluated the permit's criteria and determined that the mandatory pre-construction notification (PCN) for all activities remains a critical safeguard to ensure that new or expanding seaweed farms do not interfere with navigation, marine mammals, or other aquatic resources. While the regulatory text is unchanged, the supporting decision document has been updated to include current environmental baseline data. This includes the most recent national-scale assessments and status reports on marine environments, ensuring that the Corps' determination of 'minimal impact' is supported by the latest ecological science and reflects current usage trends in the emerging seaweed farming industry.
Aquaculture entrepreneurs, commercial seaweed farmers, and research institutions developing kelp or algae farms typically use this permit. It is the primary authorization for anyone placing structural arrays in navigable waters for the purpose of harvesting seaweed for food, fertilizer, or biofuel.
The Corps determined that the reissuance of NWP 55 results in a 'no effect' finding for federally-listed endangered or threatened species and designated critical habitat. This finding is anchored by General Condition 18, which requires project-specific ESA Section 7 consultation if an activity 'might affect' listed resources; no activity is authorized until that process is complete. This is particularly relevant for seaweed farms, which must be evaluated for potential whale entanglement or habitat displacement risks. Compliance with Section 106 of the National Historic Preservation Act is ensured through General Condition 20. Because every project under NWP 55 requires a PCN, district engineers are able to review each farm's layout for potential impacts to submerged historic properties, such as shipwrecks. Essential Fish Habitat (EFH) is protected through site-specific reviews and the application of regional conditions to ensure mooring systems do not damage sensitive seafloor habitats.
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