Palo Alto, CA Environmental Rules: Grading & Drainage (2026)

Grading activities in Palo Alto are governed by California Building Code Appendix J and local amendments requiring grading permits for excavation or fill exceeding specified volumes (typically 50 cubic yards) or depths. Grading plans must show existing and proposed contours, drainage patterns, and retaining walls. California Civil Code Section 1976-style common law requires property owners not to divert surface water onto neighbors in ways that cause damage. Retaining walls over 4 feet in height (measured from bottom of footing) require engineered design and building permits, with tiered walls having separate calculations. Hillside properties face additional review and geotechnical requirements. Construction must include erosion and sediment control during grading (see erosion-control). Final drainage must direct runoff to approved outlets (street gutters, area drains) without pooling on neighbor property. Changes to lot drainage that flood neighbors create civil liability beyond code violations.