Burnaby's geology presents a real challenge for seismic design: deep glacial till overlays interbedded sands and silts from the Fraser River delta, while the Burnaby Mountain area has colluvial deposits with variable stiffness. Before designing a foundation on this kind of profile, a non-invasive MASW survey gives us the VS30 value needed to assign the correct NBCC 2020 site class. We combine this with calicatas exploratorias to correlate surface wave velocities with actual soil stratigraphy, and ensayo SPT for direct density verification at depth. The result is a site-specific shear wave velocity model that reduces uncertainty in dynamic analysis.
A single MASW line across Burnaby Mountain can reveal VS30 values ranging from 360 m/s (Site Class D) to over 760 m/s (Site Class C) over just 200 meters of lateral distance.
Service characteristics in Burnaby
Typical technical challenges in Burnaby
A six-story residential building on Burnaby's Kingsway corridor was recently redesigned after an initial VS30 estimate from a regional map suggested Site Class C. Our MASW line, run directly along the proposed footprint, measured VS30 at 284 m/s — Site Class E, requiring a full site-specific response analysis per NBCC 2020. The developer avoided a potential under-design that could have led to excessive spectral amplification during a Cascadia subduction event. That single survey saved the project from both a structural safety issue and a future retrofit liability.
Our services
We offer two tiers of MASW/VS30 service in Burnaby, both delivered under ISO 17025 accreditation:
2D MASW Profile for Site Classification
A single 48 m line with 2 m receiver spacing, providing a 1D velocity profile at the array midpoint plus a pseudo-2D section. Includes VS30 calculation, site class assignment per NBCC 2020, and a dispersion curve plot. Ideal for low-rise buildings and single-family lots.
3D MASW Array for Complex Sites
Multiple overlapping 2D lines arranged in a grid pattern, covering up to 5,000 m2. Produces a 3D shear wave velocity volume with 1 m vertical resolution. Recommended for high-rises, bridge foundations, and liquefaction hazard assessments where lateral variability is critical.
Frequently asked questions
How does MASW compare to downhole seismic testing for VS30 in Burnaby?
MASW is non-invasive, so you avoid drilling costs and borehole disturbance. In Burnaby's colluvial soils, MASW often provides better lateral resolution than a single downhole hole, but downhole gives direct P-wave arrival times. We recommend MASW as a first pass; if the profile shows abrupt velocity contrasts, we follow up with crosshole testing for confirmation.
What is the typical cost range for a MASW survey in Burnaby?
A standard 2D MASW line with VS30 reporting in Burnaby falls between CA$2.400 and CA$3.760. The final quote depends on array length, number of lines, and site accessibility. Contact us with your site area and target depth for a firm price.
Can MASW detect liquefaction-prone layers in Burnaby's soils?
Yes, but indirectly. MASW measures shear wave velocity, which correlates with cyclic resistance ratio (CRR) using the Andrus & Stokoe (2000) method. In Burnaby's deltaic sands, a layer with VS below 200 m/s between 5 and 12 m depth indicates high liquefaction susceptibility. We always pair MASW with CPT or SPT for a complete liquefaction assessment per NBCC 2020.
How deep does the MASW survey reach in Burnaby's glacial till?
In dense till, the active array with a sledgehammer typically resolves to 15-20 m depth. For deeper profiles (30 m+), we add a passive HVSR component recording 30 minutes of ambient noise. On Burnaby Mountain, we have successfully mapped VS profiles to 40 m using this hybrid approach.