Richmond sits on the deep, soft sediments of the Fraser River delta. The city averages less than one meter above sea level. Site class here routinely falls into D or E under NBCC 2020. That means the ground amplifies earthquake shaking. We run the MASW survey to measure the actual shear wave velocity profile. No assumptions. No default tables. The VS30 value we deliver ties directly to the seismic design forces in your structural model. On Lulu Island and Sea Island, the impedance contrast with the underlying glacial till creates a velocity profile that only active-source surface wave testing captures reliably. When the drilling crew hits refusal above 30 m, we pair the SPT drilling data with the VS profile to constrain the site class where refusal depth is ambiguous under the code.
A measured VS30 of 150 m/s versus an assumed 200 m/s can double the seismic base shear in a Richmond structure.
Methodology applied in Richmond BC
Demonstration video
Critical ground factors in Richmond BC
We see it on nearly every Richmond project. The borehole log says silt-clay to 18 m. The designer assumes Site Class C. Then the MASW data comes back with VS30 of 120 m/s. That is Class E. The structural design needs rework. The foundation costs jump. The worst case is a site on the eastern edge of the city near the Annacis Channel. The peat layers there attenuate high-frequency energy. The dispersion curve becomes difficult to pick below 15 Hz. An operator without local experience will overestimate the phase velocity and report a stiffer profile than reality. That error flows directly into an unconservative seismic design. We also see cases where the liquefaction assessment requires the shear wave velocity profile. A single VS30 number is not enough. You need the interval velocities for each layer. Our deliverable includes the full 1D profile.
Our services
The MASW test forms part of a broader site characterization package we deploy across the Lower Mainland. These two services often run concurrently with the shear wave survey on Richmond sites.
Seismic Site Classification per NBCC
We combine the measured VS30 with borehole stratigraphy to assign the final Site Class (A through E). The report includes the design response spectrum parameters for the specific coordinates of your project.
1D Seismic Site Response Analysis
For Class E sites or critical facilities, we perform equivalent-linear ground response analysis using DEEPSOIL. The shear wave velocity profile from MASW is the primary input layer.
Frequently asked questions
How deep does the MASW survey profile in Richmond's soils?
We target 30 m depth below existing grade. In the deltaic silts and clays of Richmond, the 46 m array with a sledgehammer source reliably resolves the shear wave velocity down to the 30 m mark. This satisfies the NBCC 2020 requirement for VS30 calculation.
What is the cost of a MASW survey in Richmond, BC?
The cost ranges from CA$1,980 to CA$4,290. The variation depends on the number of array locations, site access constraints, and whether the survey is combined with other testing on the same mobilization.
Can MASW be performed on a paved parking lot?
Yes. We plant the geophones on the asphalt or concrete surface using steel base plates and a thin layer of viscous couplant. The high-frequency surface wave energy couples adequately through the pavement. The underlying soil profile is what controls the dispersion curve.