Across Haʻikū, Huelo and other parts of East Maui, the water comes off the roof. A catchment tank holds tens of thousands of pounds of water, and the pad under it is an excavation job worth doing right.
Catchment in Hawaiʻi
The University of Hawaiʻi's College of Tropical Agriculture and Human Resources (CTAHR) estimates that 30,000 to 60,000 people in Hawaiʻi depend on rainwater catchment. The state Department of Health says it does not regulate catchment systems on individual homes, and it points owners to CTAHR's Guidelines on Rainwater Catchment Systems for Hawaiʻi.
Why the pad matters
Water weighs about 8.3 pounds per gallon, so a full 10,000-gallon tank puts more than 80,000 pounds of water on the ground. If part of the pad settles, the tank can lean, the liner can tear, or the wall can fail. CTAHR's guidelines also cover earthquakes, a real consideration on a volcanic island.
What a good pad looks like
- Level and compacted: soft topsoil and organic material removed, the base built up in compacted layers and checked for level.
- Sized right: follow the tank manufacturer's foundation spec. Some tanks need a concrete slab, others a compacted gravel or sand bed with a ring.
- Drained: overflow and runoff routed away from the pad so it doesn't undermine the base.
- Uphill when possible: elevation can help with gravity pressure. Plan the line to the house, and call 811 before trenching. See 811.
- Reachable: leave access for a water delivery truck in dry spells. CTAHR's guidelines include firefighting concerns, so keep a clear approach for fire crews too.
Wet-side realities
Haʻikū's clay turns slick and soft in the rain. Schedule pad work for a dry stretch, and keep sediment from washing off the site. See erosion control.
Find contractors in Haʻikū and East Maui.