The International Building Code (IBC) and ASCE 7 standards require explicit soil classification for any structure in seismic-prone regions like Southern California. In Glendale, where the geology transitions from the crystalline basement of the Verdugo Mountains to deep alluvial fans along the Los Angeles River tributary, a simple visual classification is never enough. Our laboratory performs the full grain size analysis—mechanical sieving for the coarse fraction and hydrometer sedimentation for fines—following ASTM D2487. This dual approach is the only reliable way to distinguish between a well-graded gravelly sand and a silty sand with borderline liquefaction potential, a distinction that carries enormous weight in foundation design across the 91201 through 91208 zip codes. When we work on sites near the Brand Park foothills, we often combine this with an in-situ permeability test to verify how the graded soil profile actually drains during winter storm events.
In Glendale's alluvial soils, the coefficient of curvature from a complete grain size curve is often the single most reliable predictor of compaction performance and seismic response.
Scope of work in Glendale California
Risks and considerations in Glendale California
The most costly shortcut we see in Glendale is relying on a sieve-only report for a soil that has visible fines. A contractor excavates a hillside lot, sees some silt in the cut, but only orders a wash #200 to get a single fines percentage. Without the hydrometer curve, the clay fraction remains unknown. We reviewed a foundation failure in the Rossmoyne district where the geotechnical report classified the soil as silty sand, the structural engineer designed for a bearing capacity of 3,000 psf, but the actual material was a clayey silt with a liquid limit above 40 and a collapse potential upon wetting. The repair required underpinning the footings and installing a deep subdrain system. A complete grain size analysis with hydrometer would have flagged the plasticity risk before the first yard of concrete was poured. In a city with a population exceeding 190,000 and a building stock that mixes 1920s masonry with modern mid-rise steel, getting the soil index properties right is a public safety issue.
Our services
Our Glendale soil testing program integrates the grain size analysis with complementary index and performance tests to build a complete geotechnical model. Each service applies the same classification rigor across different project scales.
Complete Particle Size Distribution Package
Combined sieve and hydrometer analysis per ASTM D6913 and D7928 on a single representative sample. We report the full gradation curve, the USCS classification, and the coefficient of uniformity and curvature. This package is the baseline for every foundation investigation we perform in the San Fernando Valley and Verdugo foothills, from single-family residential additions to commercial podium slabs.
Fines Characterization with Atterberg Limits
When the hydrometer analysis shows more than 12% passing the #200 sieve, we automatically advance to Atterberg limits testing (liquid limit, plastic limit, plasticity index) per ASTM D4318. This step is essential for evaluating the seismic settlement potential of the silty soils common in the flatland areas of Glendale south of the Ventura Freeway.
Common questions
How much does a complete grain size analysis with hydrometer cost in Glendale?
For a standard composite sample with full mechanical sieve and hydrometer sedimentation, the laboratory fee ranges from US$100 to US$200. The exact cost depends on whether we are running a single sample or a batch from multiple depths, and whether companion tests like Atterberg limits are bundled. We provide a line-item quote before any work begins so there are no surprises.
Why can't I just use a sieve analysis without the hydrometer for my Glendale hillside project?
The hillside soils in Glendale, particularly the weathered granitic colluvium, often contain 10% to 30% material passing the #200 sieve. A sieve analysis alone tells you the total fines percentage but not whether those fines are non-plastic rock flour or active clay. Only the hydrometer analysis quantifies the clay-size fraction, which controls the soil's drained shear strength, its response to saturation, and its susceptibility to creep on steeper slopes. Skipping the hydrometer on a hillside lot can lead to an unconservative slope stability analysis.
How long does the hydrometer test take and does it delay my project schedule?
The sedimentation phase of the hydrometer test runs for a minimum of 24 hours, with readings taken at logarithmically spaced intervals. Including sample preparation, dispersion, and data reduction, a complete grain size analysis with hydrometer is typically reported within 3 to 4 business days. We coordinate the schedule so that the geotechnical report is never on the critical path for your Glendale building permit submission.