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CPRA scientist details mixed monitoring results for St. Tammany mitigation projects
Summary
CPRA scientist Alyssa Hemel reported on mitigation projects in Saint Tammany Parish, describing Turner-over outcomes, vegetation success criteria, reasons for shortfalls, and planned replanting or monitoring schedules for Milton Island, Fritchie Marsh (Zydeco Ridge) and a NOV-system marsh project.
Alyssa Hemel, a CPRA scientist in the New Orleans office, briefed the board on the status of Corps-constructed mitigation projects that CPRA now oversees as the non-federal sponsor. She summarized the federal compensatory requirement—type-for-type replacement—and explained CPRA’s 50-year oversight role for post-turnover operation, maintenance and monitoring.
On Milton Island (143 acres of intermediate marsh created with roughly 1,000,000 cubic yards of borrow), Hemel said the Corps achieved initial success vegetation criteria in 2019 but CPRA’s assessments at turnover in 2023 fell below the required 60% vegetation cover. Hemel cited an extreme 2023 drought and the encroachment of woody vegetation as likely causes; after additional monitoring in 2025 CPRA recorded intermediate vegetation success.
For the Fritchie Marsh Zydeco Ridge project (approximately 20 acres of marsh creation and 160 acres of bottomland hardwood creation using about 3,300,000 cubic yards of borrow), Hemel said the Corps found higher-than-expected elevations in 2021 and low survival of hardwood seedlings. Planners responded with dike degrading and gapping to improve hydrology and extensive plantings; marsh portions reached success criteria in 2023–24 but the bottomland hardwood area requires a full replant pending soil and salinity improvements.
Hemel also described a recent NOV-system marsh-creation project (about 294 acres) that completed construction in 2024 with a final inspection in Sept. 2025; the Corps plans terrace work and CPRA expects its first vegetation sampling in 2027 after settling.
Hemel emphasized the success criteria CPRA enforces—topographic/elevation ranges, percent native herbaceous vegetation cover, and invasive-species thresholds—explaining that projects often need larger mitigation footprints because created habitats do not fully match pre-impact quality. She told members CPRA will continue regular monitoring and coordinate future vegetation sampling and potential replanting schedules with federal partners.
