Soil Conditions in Orange
Orange County presents a range of subsurface conditions. Here's what we encounter most frequently.
Alluvial Fan Deposits from Santiago Creek
The City of Orange sits at the base of the Santa Ana Mountains on alluvial fan deposits from Santiago Creek. These Quaternary-age soils consist of gravelly sands, silty sands, and clays transported from the canyon uplands. Near the surface, these deposits generally provide good bearing capacity with moderate lateral variability.
La Habra Formation (Eastern Orange)
The eastern portions of the city, including areas near Santiago Hills and Peralta Hills, are underlain by the Pliocene-age La Habra Formation. This unit consists of poorly indurated sands, silts, and conglomerates that can be settlement-prone and may require over-excavation and recompaction for foundation support.
Expansive Clay Soils
Moderately to highly expansive clay soils are common throughout the Orange flatlands and lower hillside areas. Expansion indices of 50 to 90 are not uncommon, and foundation designs for structures on these soils typically require post-tensioned slabs, deepened footings, or moisture-conditioned subgrade to manage volume change.
What We Do in Orange
Soils Reports
Geotechnical investigation and foundation recommendations for building permits.
Learn more →Grading Plans
Precise and rough grading design with drainage and earthwork calculations.
Learn more →Compaction Testing
Field density testing and fill certification for construction.
Learn more →Stormwater / LID / WQMP
WQMP preparation, LID compliance, and BMP design.
Learn more →Hydrology Reports
Drainage analysis and flood risk assessment.
Learn more →Subsurface Exploration
Drilling, CPT, and test pit programs.
Learn more →Erosion Control Plans
SWPPP and erosion control for grading permits.
Learn more →Street Improvements
Frontage, curb, gutter, and sidewalk design.
Learn more →Utility Plans
Water, sewer, and storm drain design and coordination.
Learn more →Project Coordination
One point of contact managing structural, MEP, surveying, and specialty consultants.
Learn more →We also coordinate with your structural engineer, architect, MEP consultants, and other project team members to ensure our deliverables integrate with the overall design — one point of contact for your geotechnical and civil engineering scope.
What People Build in Orange
ADU / Accessory Dwelling Unit
Soils reports and grading plans for ADU construction in Orange's established residential neighborhoods, including Old Towne and surrounding areas.
Hillside Custom Home
Slope stability analysis, retaining wall design, and grading plans for custom homes in Santiago Hills and the eastern hillside communities.
Infill Residential
Geotechnical investigation and civil engineering for lot splits and small subdivision projects replacing older single-family homes.
Commercial / Mixed-Use
Foundation investigation and site engineering for mixed-use and commercial projects along Tustin Street, Chapman Avenue, and The Village at Orange.
Working With City of Orange Community Development Department
The City of Orange Community Development Department processes building and grading permits, with plan check conducted by both in-house staff and contract reviewers. Geotechnical reports are reviewed by the city's contract geotechnical consultant. The city maintains a collaborative approach to plan check with staff generally available for pre-submittal discussions.
What Makes This Jurisdiction Distinct
Old Towne Orange Historic District projects require Design Review Committee approval
Hillside development in eastern Orange requires slope stability analysis and enhanced grading design
WQMP required per Santa Ana Regional Water Quality Control Board MS4 permit
Santiago Creek flood zone setbacks apply to parcels near the creek corridor
Street tree preservation requirements may affect grading design near public rights-of-way
The City of Orange accepts electronic submittals through its permitting portal. Plan check timelines are typically 3 to 5 weeks for residential projects and 5 to 7 weeks for commercial projects. The Community Development counter is open for walk-in questions during regular business hours.
Common Questions — Orange
Building in Orange?
Tell us about your project and we'll send you a fixed-fee proposal — typically within one business day.