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Subsurface Seawater Intakes: Beach Wells & Infiltration Galleries

Engineering Excellence for Marine Environments

Subsurface intakes draw seawater through natural sand and aquifer media, which acts as a slow sand filter. The result is feed water of very low turbidity and silt density index (SDI), little to no marine biofouling, and near-zero entrainment of marine life — dramatically cutting downstream pre-treatment for SWRO. Capacity is governed by local hydrogeology.

<2–3
SDI₁₅ achievable
~50,000
m³/h (galleries)
90%+
pre-treatment chemical cut
Near-0
entrainment

Subsurface Intake Types

Matched to coastal geology

Vertical Beach Wells

Drilled wells behind the shoreline; simplest and lowest cost where a permeable beach aquifer exists.

Horizontal / HDD Wells

Directionally-drilled laterals extending under the seabed for higher yield from a single onshore site.

Slant Wells

Angled wells drilled from the beach out under the sea floor — high yield, small onshore footprint.

Radial Collector Wells

Ranney-type caisson with radial laterals for large, consolidated yield in thick aquifers.

Seabed Infiltration Galleries

Engineered filter beds beneath the sea floor — high capacity where no natural aquifer exists.

Onshore Infiltration Galleries

Beach-buried collector pipes in graded media for medium duties with excellent water quality.

Type Comparison

Selecting the right subsurface option

TypeCapacityWater QualityBest Use
Vertical beach wellLow–mediumExcellent (SDI <3)Permeable beach aquifer, small/medium plants
Slant / HDD wellMediumExcellentLimited onshore land, higher yield
Radial collectorMedium–highVery goodThick consolidated coastal aquifer
Seabed galleryHighVery goodNo aquifer; engineered filter bed

Feasibility hinges on aquifer permeability, thickness and recharge — a hydrogeological survey and pilot well are essential before committing. Where geology limits yield, pair a subsurface intake with an open-ocean intake for the balance of flow.

Related Seawater Intake Topics

Continue across the seawater intake engineering series

Related Equipment & Services

Design your seawater intake

Talk to our marine engineering team about beach wells & galleries and a complete, compliant intake package — survivable, low-fouling and built for decades of service.

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