Geotechnical
Engineering Services
Program Scope
The Soboba Band of Luiseño Indians is requesting proposals from qualified Geotechnical Engineering Consultants. This mission-critical project supports the construction of the Stormwater Drainage Line J system.
This project is strictly governed by FEMA funding regulations. Failure to meet the Phase 1 submission deadline of July 22, 2025, may result in grant revocation. Consultants must provide verified reports that adhere to federal reporting standards.
Selected consultants will execute a three-phase investigation including subsurface exploration, laboratory analysis, and reporting on geological hazards and structural foundations.
Proposal Requirements
California Board for Professional Engineers, Land Surveyors, and Geologists. Registration here is a prerequisite for bidding.
Technical Specifications
Phase 1: Field Exploration & Subsurface Analysis
- Drilling & Sampling Program: Consultant shall perform a comprehensive subsurface investigation consisting of a minimum of ten (10) borings at locations critical to the drainage line J path. Borings must be logged by a qualified engineer or geologist to accurately categorize soil stratigraphy.
- Standard Penetration Testing (SPT): Implementation of continuous or interval sampling using calibrated hammer systems to determine the N-values of soil layers, providing data on relative density and consistency of granular and cohesive materials.
- Infiltration/Percolation Protocols: Conducting field infiltration tests specifically within the footprint of proposed detention or retention basins. Data must follow local jurisdiction standards for stormwater management design.
- Corrosivity Suite: Laboratory testing of soil samples to determine chemical characteristics that affect underground infrastructure. This includes evaluating pH levels, minimum resistivity, and soluble sulfate/chloride concentrations to specify pipe materials and concrete types.
- Expansion & Strength Profile: Execution of laboratory tests for the Expansion Index (EI) and shear strength parameters. This data is essential for determining how soil will react to moisture changes under concrete slabs or asphalt paving.
- Moisture-Density Relationship: Establishing the optimum moisture content and maximum dry density (Proctor testing) for native soils intended for use as structural fill during the construction phase.
Standard Penetration Test. It measures how many "blows" from a hammer it takes to drive a tube into the ground, telling us how strong the soil is.
The ability of soil to "eat away" at buried metal pipes or concrete. High acidity or salt levels require special protective coatings.
Phase 2: Geotechnical Engineering Reporting
- Seismic Hazard Assessment: Comprehensive analysis of seismic risk based on proximity to local faults. Report must include Site Class identification and determination of seismic design parameters (Ss, S1) according to current Building Code standards.
- Liquefaction Vulnerability: Detailed assessment of the potential for soil liquefaction during a design-level seismic event, including lateral spreading and seismically induced settlement calculations for the drainage basin area.
- Structural Foundation Guidance: Engineering recommendations for the design of concrete slabs-on-grade, structural footings, and support for drainage structures. Includes allowable bearing pressures, friction factors, and lateral earth pressures (active, passive, at-rest).
- Pavement Section Design: Providing site-specific asphalt and base material thicknesses based on Traffic Index (TI) values. Parking areas shall be designed for a TI of 4.5, while fire access lanes and main drive aisles require a TI of 7.0 for heavy vehicle support.
- Grading & Site Preparation: Detailed specs for clearing, grubbing, over-excavation depths, and re-compaction requirements. Consultant must address the suitability of on-site soils for use as structural fill versus the need for imported materials.
- Surface & Subsurface Drainage: Professional recommendations for the control of surface runoff and the prevention of moisture intrusion into structural subgrades, ensuring the longevity of the Line J infrastructure.
When wet soil acts like a liquid during an earthquake, causing heavy structures to sink or tilt. Critical for basin safety.
A numerical value representing how many heavy trucks will use a road. A higher TI (like 7.0) means thicker asphalt and stronger base layers.