Water Storage
Vai Koko: The Cocoon Tank of Life
Overview
Vai Koko (“Water Cocoon”) is a semi-submerged, modular water tank system designed for Tuvalu’s lagoons. Serving as the primary off-body water storage solution for Vai Tapu desalination nodes, Vai Koko combines infrastructure, ecology, and culture. It is both a practical engineering solution and a sacred civic presence. The outer Reefskin layer, applied by local stewards during deployment, also serves as an underwater ecological growth zone—encouraging marine life colonization and fostering community engagement.
Key Functions
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Stores up to 20,000 liters of clean water
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Submerged for cooling, space savings, and flood resilience
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Hosts coral propagation on crown module
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Connected to Vai Tapu desalination units via 4" HDPE lines
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Integrated with Guardian for monitoring and status lighting
Why This Was Never Done Before: Reframing Infrastructure as Ecology
Using water tanks as lagoon infrastructure may seem obvious now, but it has rarely been attempted. This is not due to technical limitations—but due to perception, discipline boundaries, and institutional momentum.
Tanks are Seen as Utility Hardware
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In most engineering contexts, tanks are considered passive containers—not structural building blocks. Their role is assumed to be storage only.
Silos Between Disciplines
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Civil, marine, water, and ecological engineering are rarely combined into one design process. The idea of embedding coral nurseries into civic water infrastructure is still unfamiliar to most planners and funders.
Design Bias Toward Permanent Monuments
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Traditional harbor or lagoon construction favors heavy, expensive, and overbuilt materials—concrete, steel, and geo-composites. These come with long timelines and little flexibility.
Lack of Precedent
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Decision-makers often rely on proof from past projects. If no one has done it, few are willing to try—especially in risk-averse or low-resource settings.
Cultural Framing Was Missing
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What Vai Koko introduces is a sacred reframe: these are not just tanks—they are vessels of memory, ecology, and continuity. The combination of ritual, coral growth, and civic integration is what makes this approach not just viable, but visionary.
Technical Architecture
Volume Capacity
~20,000 liters per unit
Material
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UV-resistant, food-grade polyethylene with outer marine-safe resin coat
Form Factor
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Vertical capsule shape
Height: 2350mm
Diameter: 3300mm
Wall Thickness: 10–15mm
Submersion & Cooling
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Lower half of tank embedded ~1.2–1.5 meters in lagoon sand. Passive cooling via submersion and optional shade canopy.
Access & Maintenance
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Top Hatch: 0.5m gasket-sealed, lockable
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Internal stainless ladder for service entry
Piping & Ports
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4-inch inlet/outlet HDPE stub-outs (low on sides)
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Overflow channel for safe discharge to halophyte beds
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Sensor port for Guardian node
Status Lighting
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Solar-powered RGB light ring mimics bioluminescence
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Shows water level, alerts, and ritual statuses
Known Risks & Mitigations
Biofouling & Algae Growth
Marine organisms may attach to the tank surface, affecting light rings or coral growth.
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Mitigation: Periodic cleaning, eco-safe antifouling coatings.
Sediment Shift & Erosion
Lagoon sands may shift, exposing or destabilizing buried tanks.
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Mitigation: Deep anchor skirt, geotextile base mesh, and bio-stabilizing vegetation.
Storm Surge & Buoyancy
Tanks may lift during high tides or storms if not fully anchored.
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Mitigation: Weighted ballast sleeves, tie-down straps, Guardian position tracking.
Material Degradation
Polyethylene surfaces may degrade over time from sun and salt exposure.
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Mitigation: Marine-grade resin, Guardian maintenance tracking, scheduled surface inspections.
Coral Health Risks
Overcrowding or poor positioning could reduce coral success.
Mitigation: Marine biology consultation, varied slot testing, seasonal tracking.
Maintenance Access Challenges
Top entry and lagoon setting may complicate maintenance.
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Mitigation: Add external flushing ports, modular ladder kits, dry-entry protocols.
Sensor or Lighting Malfunction
Water intrusion or salt corrosion could affect electronics.
Mitigation: Marine-rated enclosures, dual-gasket seals, Guardian alert failover.
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Smart valve control (remote/manual)
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Enhanced Guardian coral sensors (nutrients, pH)
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10,000L compact variant for remote sites
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Floating version for deeper atolls or mobile use