Grading & Drainage: Urban Honolulu vs Waipahu
How do grading & drainage rules compare between Urban Honolulu, HI and Waipahu, HI?
Urban Honolulu and Waipahu have similar restriction levels.
Urban Honolulu, HI
Honolulu County
Tower excavations and infill projects in Urban Honolulu must obtain grading permits under ROH Chapter 18A, with dewatering, shoring, and drainage coordination critical in Kakaako and Ala Moana's high water-table conditions.
View full Urban Honolulu rules →Waipahu, HI
Honolulu County
Waipahu land disturbing activities require grading permits under ROH Chapter 18A, which governs permits, bonds, inspections, and drainage review for all qualifying work.
View full Waipahu rules →Key Facts Comparison
| Fact | Urban Honolulu | Waipahu |
|---|---|---|
| Authority | ROH Chapter 18A | - |
| Application | Sec. 18A-2.2 | - |
| No-permit penalty | Sec. 18A-2.4A | - |
| Urban concern | Dewatering, shoring | - |
| Bonds | Required | - |
| - | - |
Highlighted rows indicate differences between cities.
Urban Honolulu FAQ
Does a Kakaako tower need a grading permit even on a small lot?
Yes. Basement excavation easily exceeds Chapter 18A thresholds, and Sec. 18A-2.2 requires a full permit application including hydrology and shoring plans before work.
How is dewatering handled in Urban Honolulu excavations?
Grading plans must coordinate with ROH Chapter 43 Article 11 stormwater rules. Dewatering discharges typically require separate NPDES coverage and cannot be released untreated.
Waipahu FAQ
Does adding fill for a small Waipahu addition need a permit?
Yes, if the fill or grading exceeds thresholds in Chapter 18A. Even modest grading associated with additions typically requires a grading permit, so confirm with permitting before starting.
Can my neighbor's runoff come onto my lot?
Grading permit drainage review is intended to prevent concentrated runoff onto neighbors. If your neighbor's grading changed drainage, document it and contact the Department of Planning and Permitting.
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