Soil Conditions in Redlands
San Bernardino County sits at the transition from coastal influence to high desert — creating a wide range of soil conditions and seismic considerations. Here's what we typically find.
San Bernardino Mountains Alluvial Fan
Redlands is located on alluvial fan deposits from the San Bernardino Mountains, with soils ranging from coarse gravels and sands near the mountain front to finer-grained silts and clays in the lower elevations. The relatively undisturbed soils in areas with citrus grove heritage often provide good bearing conditions, though site-specific investigation is always needed.
Redlands Clay — Expansive Soil
Portions of Redlands, particularly in the southern and central areas, contain expansive clay soils locally known as Redlands clay. These soils undergo significant volume change with moisture fluctuations, causing heaving and cracking in foundations and flatwork. Post-tensioned slabs, moisture barriers, and select fill are common mitigation measures.
San Andreas, Mill Creek, and Mission Creek Faults
Redlands is bounded to the north by the San Andreas fault system, with the Mill Creek and Mission Creek strands passing through the northern portions of the city. These active faults place Redlands in a high seismic hazard zone, and properties near the fault traces may require Alquist-Priolo fault rupture investigations.
Citrus Grove Heritage — Relatively Undisturbed Soils
Many parcels in Redlands have a history of citrus cultivation, and in areas where groves were not heavily regraded, native alluvial soils are relatively undisturbed at shallow depths. However, irrigation infrastructure removal and orchard clearing can leave localized fill pockets that require evaluation during grading.
What We Do in Redlands
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 and BMP design for stormwater compliance.
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 Redlands
Custom Single-Family Homes
New homes on individual lots throughout Redlands, including infill parcels on former citrus groves. Geotechnical investigation must address expansive soils and seismic hazards specific to each lot.
ADU / Accessory Dwelling Unit
Detached ADUs and garage conversions on established residential lots, requiring soils reports to address Redlands clay expansion potential for new foundations.
University-Adjacent Development
Mixed-use and student housing projects near the University of Redlands, requiring geotechnical investigation, grading plans, and stormwater compliance.
Historic District Renovation
Renovation and adaptive reuse of structures within the downtown historic overlay, requiring geotechnical evaluation of existing foundations and soil conditions for proposed modifications.
Commercial & Retail
Retail and office development along major corridors including Redlands Boulevard, Orange Street, and Tennessee Street, requiring standard geotechnical and civil engineering services.
Working With City of Redlands Development Services Department
The City of Redlands Development Services Department reviews geotechnical reports, grading plans, and stormwater compliance documents for new construction and grading permits. Redlands maintains a thorough review process with attention to soil expansion, seismic hazards, and compatibility with the city's historic character in designated areas.
What Makes This Jurisdiction Distinct
Expansion index testing required — Redlands clay is prevalent in portions of the city and may require enhanced foundation design
Historic preservation overlay in downtown and Smiley Park areas may impose restrictions on grading, excavation, and site disturbance
Alquist-Priolo fault rupture investigation required for parcels near Mill Creek and Mission Creek fault traces
Drainage and hydrology study required to demonstrate no adverse impact on adjacent properties from increased runoff
Projects within the historic preservation overlay should consult Development Services early to understand additional review requirements. Geotechnical reports for sites with known expansive soils should clearly state the expansion index and provide specific foundation mitigation recommendations.
Common Questions — Redlands
Building in Redlands?
Tell us about your project and we'll send you a fixed-fee proposal — typically within one business day.