Temecula, CA Environmental Rules: Grading & Drainage (2026)

Temecula regulates grading and drainage under TMC Title 18 and CBC Appendix J. A grading permit is required for: any grading over 50 cubic yards, disturbance of 5,000+ square feet, cuts or fills exceeding 3 feet vertical, or any work on slopes steeper than 5:1. Permit applications require an engineered grading plan, drainage study, and (for hillside projects) a soils/geotechnical report. Drainage rules: lot grading must direct water away from foundations with a minimum 5% slope for the first 10 feet (or 2% for hardscape). Discharge must reach an approved outlet — public street, storm drain, or natural watercourse — without diverting historic flows onto neighboring property. California Civil Code §831 makes diverting surface water onto neighbors actionable as nuisance and trespass. Retaining walls over 4 feet (measured from bottom of footing to top of wall) require a separate building permit and engineered design. Walls supporting surcharge loads (driveways, structures above) need engineering at any height. Detention/retention basins may be required for projects increasing impervious area significantly. Final grading certification by a licensed surveyor or civil engineer is required before occupancy. Violations include stop-work orders, fines, and forced restoration.