MASW / VS30 (Shear Wave Velocity) Testing in Pickering, ON

For a standard MASW line with 24-channel acquisition, including dispersion analysis, inversion, and a VS30 report, the cost in Pickering typically falls between CA$2,100 and CA$4,040. The spread depends on site access—working in landscaped areas or near buried utilities adds time—and whether we need a second orthogonal line for site class confirmation under NBCC requirements.

NBCC 2020 restricts default assumptions to cases where the soil and rock conditions are well-documented and the site clearly fits the description in Table 4.1.8.4.A. In Pickering's variable glacial terrain—especially where soft clays are suspected—we rarely see a site that qualifies for a default Class C without at least a measured shear wave velocity or a correlated SPT-based estimate. Most municipalities now require a measured VS30 for buildings over three storeys.

A single 24-channel MASW spread takes our crew about 90 minutes to lay out, shoot, and pack up. We need a clear line roughly 70 to 90 metres long by 2 metres wide—typically a future building footprint or a parking lot. If we're running multiple lines or combining with SPT drilling, site work extends to a half-day. The processing and inversion back at the lab adds about three business days before the draft VS30 report is ready.

MASW is a surface method that measures Rayleigh wave dispersion and inverts it to a 1D shear wave velocity profile, without requiring a borehole. A downhole seismic test requires a cased borehole and measures the direct arrival of shear waves at a downhole geophone. MASW is faster and less expensive for site class screening, but downhole testing gives higher vertical resolution. In Pickering, we often use MASW for the overall VS30 determination and recommend downhole only when thin-layer resolution is critical, such as for a liquefaction assessment.

On asphalt or concrete, we can plant the geophones using base plates with a thin layer of coupling gel—it works well as long as the pavement is bonded to the subgrade. Inside an active building, MASW is harder because the low-frequency geophones pick up foot traffic and mechanical noise. For indoor sites, we usually recommend a seismic refraction line or, if a borehole exists, a downhole survey instead. We assess each site during the walkthrough and advise on the method that will give the cleanest data.