Reference

Engineering Glossary

Name: Moment Engineering
Address: San Diego, CA, 92115, US
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Key terms in geotechnical and civil engineering — defined clearly for owners, architects, and contractors navigating Southern California projects.

APN (Assessor's Parcel Number): A unique number assigned to each parcel of land by the county assessor. Required on all permit applications and engineering plan sheets.
Bearing Capacity: The maximum load per unit area that soil or rock can support without shear failure or excessive settlement. Reported as an allowable bearing pressure (e.g., 2,000 psf) in a soils report.
Bench: A horizontal step cut into a natural slope before placing fill. Benching ties new fill into existing soil to prevent sliding failure at the fill-natural contact.
Best Management Practice (BMP): Structural or non-structural measures used to prevent, control, or treat stormwater pollution. Required on construction sites and development projects under the Clean Water Act permit program.
Boring Log: A detailed record of soil and rock encountered during a subsurface investigation. Documents depth, soil classification, blow counts (SPT), moisture content, and sampling locations.
California Bearing Ratio (CBR): A penetration strength test used to evaluate the load-bearing capacity of subgrade soils for pavement and slab design. Higher CBR values indicate stronger soils.
CBC (California Building Code): The state building code adopted every 3 years based on the International Building Code with California amendments. Sets minimum standards for structural, fire, accessibility, and energy requirements.
Compaction Testing: Field testing that verifies fill soil has been compacted to the required relative compaction (typically 90–95% of maximum dry density per ASTM D1557). Required during grading operations.
Cone Penetration Test (CPT): A continuous in-situ test that pushes an instrumented cone into the ground at a constant rate. Provides continuous soil profiling and estimates of engineering properties without sampling.
Cut and Fill: The process of excavating (cutting) earth in high areas and placing (filling) it in low areas to create a level building pad. Grading plans quantify volumes and specify compaction requirements.
Daylight Line: The line on a grading plan where a cut or fill slope intersects the existing ground surface. Used to establish the extent of grading and slope setback requirements.
Discretionary Permit: A permit requiring public review and agency approval (e.g., conditional use permit, variance). Triggers CEQA environmental review and typically requires a soils report as part of the application.
Expansive Soil: Soil that shrinks and swells with moisture changes, primarily due to clay minerals. Common in Southern California. Requires special foundation design, pre-saturation, or soil treatment.
Factor of Safety (FS): The ratio of resisting forces to driving forces in a stability analysis. A minimum FS of 1.5 is typically required for static slope stability; 1.1–1.2 for seismic conditions.
Finish Grade: The final elevation of the ground surface after grading is complete, as shown on the grading plan. Typically set to drain away from structures at a minimum 2% slope.
Geotechnical Investigation: The subsurface investigation program used to characterize soil and rock conditions at a project site. Typically includes borings or test pits, laboratory testing, and a written soils report.
Grading Permit: A permit issued by a local jurisdiction to authorize earthwork exceeding defined thresholds (typically 50–100 cy). Requires a grading plan stamped by a licensed civil engineer.
Grading Plan: A civil engineering plan that shows existing and proposed grades, earthwork quantities, drainage patterns, and construction notes. Required by most jurisdictions before issuing a grading permit.
Hydromodification: Changes to natural stormwater runoff patterns caused by land development — increases in peak flow, volume, and duration. San Diego County requires hydromodification management for projects disturbing ≥1 acre.
Keying: Excavating a trench at the toe of a fill slope and filling it with compacted material to provide a stable foundation for the fill and prevent slope creep.
Lateral Earth Pressure: The horizontal pressure exerted by soil on a retaining structure. Calculated using active, passive, or at-rest earth pressure coefficients depending on wall movement conditions.
LID (Low Impact Development): A stormwater management approach that mimics natural hydrology using on-site infiltration, evapotranspiration, and filtration. San Diego County requires an LID Report for most development projects.
Liquefaction: The phenomenon where saturated, loose sandy soil temporarily loses strength during seismic shaking and behaves like a liquid. California jurisdictions require liquefaction evaluation in mapped zones.
Maximum Dry Density (MDD): The highest dry unit weight achievable for a soil at its optimum moisture content, determined by Proctor compaction testing. Used as the reference density for field compaction testing.
NPDES Permit: National Pollutant Discharge Elimination System permit. Construction sites disturbing ≥1 acre must obtain a Construction General Permit (CGP) and implement a SWPPP.
Percolation Test: A field test that measures the rate at which water is absorbed by soil. Used to size seepage pits, leach fields, and stormwater infiltration BMPs.
Plan Check: The review of construction documents by a building or public works department to verify compliance with applicable codes and standards. Engineering reports are submitted with plans during plan check.
Priority Project: A category of development project subject to enhanced stormwater requirements under the San Diego County Model Stormwater Standards Manual. Includes new development ≥10,000 sf and certain land uses.
R-Value: A measure of soil resistance used in California pavement design (Hveem method). Determined by the Stabilometer test. Low R-values indicate weak subgrade requiring thicker pavement sections.
Relative Compaction: The ratio of field dry density to the laboratory maximum dry density, expressed as a percentage. Grading specifications typically require 90% or 95% relative compaction for structural fill.
Rough Grade: An intermediate grading stage where the site is shaped to approximate final grades, typically within 0.1 foot. Compaction testing is performed at rough grade before utility installation.
Section 1.8.8 Report: A soils and geology report required under CBC Section 1803 for projects in California. Also referred to as a Preliminary Geotechnical Investigation or simply a 'soils report.'
Setback: The minimum required horizontal distance from a structure or fill to a property line, slope face, or other feature. Geotechnical setbacks are often more restrictive than zoning setbacks.
Settlement: Downward movement of a structure due to compression or consolidation of underlying soils. Geotechnical engineers estimate total and differential settlement to ensure structures remain serviceable.
Site Class: A classification (A–F) per ASCE 7 that characterizes the seismic response characteristics of the upper 100 feet of soil profile. Used by structural engineers to determine seismic design parameters.
Slope Stability Analysis: Engineering analysis to evaluate the safety of a slope against failure. Uses limit equilibrium or numerical methods to calculate factor of safety for static and seismic loading conditions.
Standard Penetration Test (SPT): An in-situ test that drives a split-spoon sampler 18 inches into the ground with a 140-lb hammer dropped 30 inches. The blow count (N-value) correlates to soil density and strength.
Stormwater Retention/Detention: Retention permanently captures runoff on-site (no outlet). Detention temporarily stores runoff and releases it at a controlled rate. Both are used to manage hydromodification and water quality.
Swale: A shallow, vegetated or hardscaped channel used to convey surface stormwater drainage across a site. Grading plans show swale locations, dimensions, and slopes.
SWPPP (Stormwater Pollution Prevention Plan): A required plan for construction sites disturbing ≥1 acre that identifies pollutant sources and BMPs to prevent stormwater pollution. Filed with the State Water Board under the Construction General Permit.
Undrained Shear Strength: The shear resistance of a saturated fine-grained soil measured without allowing drainage. Represents short-term (end-of-construction) stability conditions in clays and silts.
WQMP (Water Quality Management Plan): A post-construction stormwater compliance document required in Orange County and Los Angeles County. Identifies permanent treatment control BMPs to address priority pollutants from the developed site.

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