Grain Size Analysis (Sieve + Hydrometer) in Nanaimo, BC

Soil classification on Vancouver Island starts with a reliable grain size distribution. In Nanaimo, where glacial till, marine clays, and colluvial deposits often appear in the same borehole, the combined sieve and hydrometer method (ASTM D422 / D7928) eliminates guesswork. Our lab runs the full curve from coarse gravel down to the clay fraction. Contractors and geotechnical consultants use these results to confirm fill suitability, predict drainage behavior, and satisfy NBCC and CSA A23.3 requirements for foundation design. The test pits crew logs the field sample; we complete the picture in the lab. When a project involves deep excavations in the Departure Bay formation, the hydrometer fraction becomes critical for assessing settlement potential and soil reactivity.

A complete grain size curve turns a ‘silty sand’ guess into a defensible engineering classification.

Technical details of the service in Nanaimo

Nanaimo’s geology is diverse. Glacial advance-retreat cycles left a mix of Vashon till, glaciomarine stony clay, and outwash sands that can fool a visual classification. A single bulk sample from the Chase River area might contain 40% gravel, 35% sand, and 25% fines—a gap-graded material that drains unpredictably. The sieve analysis quantifies the coarse fraction; the hydrometer captures silt and clay percentages below the No. 200 sieve. Together they give the full particle-size curve needed for USCS classification. We pair this data with Atterberg limits to define the plasticity of the fines, which matters when the material is destined for a structural fill or a retaining wall backfill. The entire process is run under the same quality system that governs our triaxial and consolidation testing.

Grain Size Analysis (Sieve + Hydrometer) in Nanaimo, BC

Parameter	Typical value
Test method	ASTM D422 (sieve) / D7928 (hydrometer)
Sieve size range	75 mm to 75 µm (No. 200)
Hydrometer range	75 µm to approximately 1 µm
Classification standard	USCS per ASTM D2487
Minimum sample mass	500 g (fine soils); up to 20 kg for gravels
Dispersing agent	Sodium hexametaphosphate per ASTM
Reporting	Semi-log plot, D10-D30-D60, Cu, Cc

Risks and considerations in Nanaimo

A common mistake on Nanaimo jobsites is accepting a visual-manual classification for structural fill without a lab curve. A ‘sandy gravel’ that actually contains 12% clay can hold pore pressure, fail compaction specs, and cause pavement distress within two winters. Even worse, assuming a clean sand based on feel and skipping the hydrometer leads to missed fines content that triggers liquefaction susceptibility under the NBCC seismic provisions. We have seen otherwise well-compacted pads fail density re-tests because the proctor was run on a poorly characterized material. The grain size analysis removes that uncertainty. It is the cheapest insurance against a failed subgrade inspection or a redesign halfway through construction.

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Email: info@geotechnicalengineering.vip

Applicable standards: ASTM D422 – Standard Test Method for Particle-Size Analysis of Soils, ASTM D7928 – Standard Test Method for Particle-Size Distribution of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis, ASTM D2487 – Standard Practice for Classification of Soils for Engineering Purposes (USCS), NBCC 2020 – Seismic site classification per Table 4.1.8.4.A, CSA A23.3 – Design of concrete structures (aggregate suitability)

Our services

We run the full particle-size package for projects across central Vancouver Island. Turnaround is typically 3 to 5 business days after sample delivery.

Sieve + Hydrometer Package

Complete ASTM D422/D7928 analysis from coarse gravel to clay fraction. Includes semi-log plot, D-values, uniformity and curvature coefficients, and USCS classification.

Wash Sieve Only (No. 200)

Rapid determination of fines content for granular materials. Used for fill acceptance and filter compatibility checks on Nanaimo-area developments.

Hydrometer Testing

Standalone sedimentation analysis for fine-grained soils. Delivers clay and silt fractions needed for seismic site class determination per NBCC.

Quick answers

How much does grain size analysis cost in Nanaimo?

A standard sieve plus hydrometer package runs CA$130–CA$220, depending on whether the material is predominantly granular or fine-grained and how many sieve sizes are requested.

What sample size do I need for the lab?

For fine soils, 500 grams of representative material is enough. If the sample contains gravel up to 75 mm, we need at least 15 to 20 kg to get a statistically valid split for the coarse fraction.

How does the hydrometer analysis work?

We disperse the minus-No.-200 fraction in a sodium hexametaphosphate solution and measure density changes over time with a calibrated ASTM 152H hydrometer. Stokes’ Law converts the readings to particle diameters, giving the silt and clay percentages.