Mariculture
VerifiedNWP 55: Seaweed Mariculture Activities
Structures in marine and estuarine waters, including structures anchored to the seabed in waters overlying the outer continental shelf, for seaweed mariculture activities. This NWP also authorizes structures for bivalve shellfish mariculture if shellfish production is a component of an integrated multi-trophic mariculture system (e.g., the production of seaweed and bivalve shellfish on the same structure or a nearby mariculture structure that is part of the single and complete project).
Acreage limit
The 2026 rule states no acreage limit for NWP 55. Eligibility turns on the activity description in the rule text and the general conditions that apply, not on a numeric cap.
Pre-construction notification: Always required
Every use of NWP 55 requires a pre-construction notification to the district engineer before work begins. There is no minimum-impact threshold that exempts a project from this requirement.
If a PCN is required, general condition 32 gives the district engineer 30 calendar days to determine whether it is complete, then up to 45 calendar days from receipt of the complete PCN to respond before the permittee may proceed. Those are two separate clocks, not one.
Source
- Federal Register citation
- 91 FR 768
- Effective date
- March 15, 2026
- Cited text
- 91 FR 768 - Reissuance and Modification of Nationwide Permits (final rule, 8 Jan 2026) Read the rule
What this page does not tell you
- District regional conditions. Any of the 38 USACE districts can narrow NWP 55, add a notification requirement beyond general condition 32, or revoke the permit entirely inside its boundaries. PermitBird holds no compiled regional conditions yet. Check the district.
- State Clean Water Act Section 401 certification. Each of the 54 states and territories must certify, condition, waive or deny use of this permit before it authorises a discharge there. PermitBird holds no compiled certification yet. Check the state.