A stack of brass sieves sits on a mechanical shaker at the Richmond lab, each pan capturing a progressively finer fraction of soil. The full grain size analysis for Richmond BC projects requires both the sieve stack and a hydrometer cylinder—because the silts and clays of the Fraser River delta pass right through the finest mesh. The hydrometer test measures how long those suspended particles take to settle in a graduated cylinder, applying Stoke’s law to define the silt-clay boundary at 2 microns. In a city where the subsurface alternates between sandy channel deposits and soft marine silts, the combined D422 plus D6913 protocol delivers the continuous gradation curve that geotechnical engineers need for liquefaction screening and drainage assessment. For projects on River Road or near the dyke system, we often pair the particle-size distribution with an Atterberg limits test to confirm the plasticity characteristics of those fine-grained layers.
The hydrometer captures what sieves miss—and in Richmond’s deltaic silts, that fraction controls both drainage and seismic response.
Methodology applied in Richmond BC
This level of detail matters when a contractor on Westminster Highway is trying to determine whether the trench backfill meets the City of Richmond’s gradation envelope for bedding sand, or when a consultant is assessing the internal stability of a granular filter beneath riprap on the Steveston waterfront.
Demonstration video
Critical ground factors in Richmond BC
A three-storey mixed-use building planned on No. 3 Road was redesigned after the initial grain size analysis in Richmond BC revealed a continuous silt layer with more than 80 percent fines passing the No. 200 sieve. The original shallow footing scheme had assumed a sandy profile based on neighbouring borehole logs, but the hydrometer data showed the material was a low-plasticity silt—potentially liquefiable under the seismic shaking expected for a 1-in-2,475-year event. The structural engineer switched to a piled foundation bearing in the deeper Pleistocene till, adding about six weeks to the schedule but eliminating the settlement risk that would have surfaced during construction. Across the Lulu Island floodplain, similar surprises arise when project owners skip the full hydrometer analysis and rely solely on sieve data; the fine tail of the grain-size curve is precisely where the biggest geotechnical uncertainties hide, especially in a seismic zone as active as coastal British Columbia.
Our services
The grain size analysis in Richmond BC can be ordered as a standalone laboratory test on disturbed samples or bundled with a broader geotechnical investigation. The two standard configurations cover the full particle-size range from coarse gravel down to colloidal clay.
Sieve Analysis (Coarse Fraction)
Mechanical sieving from 75 mm to the No. 200 sieve per ASTM D6913, with oven-dried sample preparation and wash-through of fines. Results report percent retained on each sieve, cumulative percent passing, and the coarse-side gradation curve. Suitable for sands used in Richmond’s bedding and backfill applications, where conformance to municipal gradation envelopes is a contract requirement.
Hydrometer Analysis (Fine Fraction)
Sedimentation test per ASTM D7928 using a 152H hydrometer and sodium hexametaphosphate dispersant. Measures the silt-clay distribution from 75 µm down to approximately 1 µm. Combined with the sieve curve, this test provides the complete particle-size distribution needed for USCS classification, liquefaction screening in Richmond’s seismic site class D and E soils, and hydraulic conductivity estimation for dewatering design.
Frequently asked questions
Why does Richmond BC need the hydrometer test instead of just a sieve analysis?
Richmond sits on deep deposits of Fraser River delta sediments that contain significant silt and clay fractions. The sieve analysis stops at the No. 200 sieve (75 microns), so it cannot distinguish between silt and clay or define the full gradation curve. The hydrometer test per ASTM D7928 quantifies the fines distribution, which is essential for USCS classification, liquefaction susceptibility assessment under the NBCC 2020 seismic provisions, and accurate permeability estimates for dewatering system design.
What sample size do you need for a proper grain size analysis?
The required mass depends on the maximum particle size. For sands and silts typical of Richmond, a 500-gram representative sample is usually sufficient for the full sieve-hydrometer combination. If gravel is present, we need a larger sample—up to 25 kilograms for material with 75 mm particles—to satisfy the minimum mass requirements in ASTM D6913.
How do you handle organic material in Richmond soil samples?
Richmond’s near-surface soils often contain peat and organic silt layers, especially in the eastern parts of Lulu Island. The laboratory performs a loss-on-ignition pre-treatment or hydrogen peroxide digestion before running the hydrometer analysis, because organic coatings can flocculate clay particles and distort the sedimentation results. The pre-treatment method is noted on the final report so the engineer can interpret the data correctly.
Can the grain size curve be used to estimate soil permeability?
Yes, several empirical correlations—such as Hazen’s formula for sands and the Kozeny-Carman approach—use the D10 and D50 values from the grain size curve to estimate hydraulic conductivity. In Richmond, where dewatering and flood protection are central design concerns, these estimates provide a first-order input for wellpoint and sump pump sizing, though they should be verified with in-situ permeability testing for critical structures.