Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Study Update topic
No spam. Unsubscribe anytime.
Consultants: 2.4 million cubic yards planned for 2026; structures could cost $10–15M to reduce repeated renourishment
Summary
Engineers told the Isle of Palms committee the upcoming 2026 renourishment will place about 2.4 million cubic yards of sand, but historic and recent high erosion rates mean large replacement volumes could be needed within 5–10 years; structural options (groins, breakwaters) were presented with preliminary program costs of roughly $10–$15 million.
Consultants updated the Isle of Palms Beach Preservation Committee on the monitoring and alternatives study, presenting baseline choices, erosion‑rate scenarios and an assessment of structural and renourishment strategies.
Chris Creed, a coastal engineer working with the study team, said the study baseline will use the crest of the primary dune and three reference lines (a 50‑ft offset from seaward development, the 2017 SCDHEC line and planned dune construction) and that the team selects the most seaward occurrence to define a “minimum beach condition.” Using monitoring data, the consultants then applied low‑ and high‑rate shoreline change scenarios to the 2026 project distribution.
The consultants reported the planned 2026 sand placement totals about 2.4 million cubic yards distributed roughly as 800,000 cu yd to the southern reach (reaches 1–2), 800,000 cu yd in reach five and about 900,000 cu yd in reach six. They emphasized much of that material will be consumed to build the minimum beach baseline in areas where the beach has already eroded landward.
Under conservative (low) erosion rates, the team estimated that five years after construction the island could need nearly 1 million cu yd of additional sand to return the minimum baseline to target levels. Under the more recent high‑rate scenario, five‑year replacement could approach 2 million cu yd; a seven‑year interval could require on the order of 3.5 million cu yd. The consultants cautioned that these are scenario-based estimates using historical performance data and not deterministic forecasts.
Because renourishment alone may not maintain the minimum beach condition in the most erosive reaches, the consultants presented structural alternatives: short terminal groins with small breakwaters, longer terminal groins and combinations of T‑head groins and breakwaters in reaches five and six. Preliminary cost ranges presented to the committee were approximately $3.5–$5 million for a terminal groin option in one reach, $4–$5 million for a T‑head/breakwater combination in another reach and $2.5–$4 million for smaller reach‑six structures — an order‑of‑magnitude program cost of roughly $10–$15 million if multiple structures were implemented.
Consultants and committee members discussed tradeoffs — structures can protect infrastructure between nourishment events but may be visible and change beach access patterns; design choices (low‑profile, transmissive elements) can let sand move past structures to reduce adjacent impacts. The study team recommended further design and permitting work, a phased approach, and a field visit to comparable projects to inform local decisions.
The consultants said they will complete a life‑cycle cost analysis comparing renourishment intervals and structural alternatives and return to the committee with refined cost estimates and recommended phasing.
