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

California Building Code Appendix J (Grading) sets the framework adopted by HMC Title 15 — grading permits are required before any grading activity, with limited exemptions (excavation for foundations, utility trenches, agricultural grading on land used for agriculture). Per CBC Appendix J §J104, applications must include plans showing existing and proposed contours, drainage patterns, erosion control measures, and soil engineering reports for cuts over 5 feet or fills over 3 feet. Cut slopes generally cannot be steeper than 2:1 (horizontal:vertical) per §J106, with exceptions allowed via geotechnical report. Fill slopes have similar 2:1 limits per §J107. CBC Appendix J §J109 requires drainage and terrace design — terraces every 30 vertical feet on slopes over 30 feet high, swales to intercept runoff, and discharge to an approved drainage system. The Hesperia Engineering Department reviews drainage studies showing pre- and post-development runoff (typically using HEC-HMS or San Bernardino County Hydrology Manual methods) and ensures no increase in downstream flows. Post-construction BMPs (WQMPs) implement the Phase II MS4 Permit's post-construction provisions. The 2022 California Building Code adopted by Hesperia is enforced through the Building & Safety Division.