A new three-storey mixed-use project on Lonsdale Avenue hit a snag last fall. The geotechnical boreholes showed competent till. But the seismic site classification came back unknown. That triggered a higher design base shear under the 2020 National Building Code. The structural engineer needed a Vs30 value. Our crew deployed a 24-channel MASW spread on the parking area. Within three hours we delivered a shear wave velocity profile to 30 metres. The site class shifted from default Class D to Class C. The lateral load demand dropped 20 percent. That single survey saved the owner tens of thousands in structural steel. North Vancouver sits on complex glacial and marine sediments. Assumptions are expensive here. A seismic refraction survey complements MASW when bedrock depth is shallow and you need a two-method cross-check.
One MASW survey can shift your site class from D to C and cut lateral design forces by up to 30%.
Frequently asked questions
How much does a MASW survey cost in North Vancouver?
Active-source MASW surveys in North Vancouver range from CA$2,160 to CA$4,590 depending on array length, site access, and number of spreads. A single 24-channel spread for a standard lot is at the lower end. Two or three spreads with longer offsets push toward the upper range. We provide a fixed-price quote after reviewing the site plan.
Does the NBCC require MASW for all buildings?
The 2020 NBCC strongly encourages site-specific Vs30 measurement for any structure assigned Importance Category Normal or higher. You can default to Class D or E from borehole data, but that usually increases design loads. A measured Vs30 often pays for itself in structural savings.
Can you do MASW on a sloped site?
Yes, with adjustments. Gentle slopes under 10 degrees work well with a standard linear array. Steeper sites require a contour-following spread and topographic correction in processing. We have surveyed steep lots in the Upper Lonsdale and Deep Cove areas.
How long does a MASW survey take on site?
Field work for one 24-channel spread takes about two hours. This includes equipment layout, calibration shots, and data quality checks. A full report with Vs30 and site class letter is delivered within two business days.
What's the difference between MASW and seismic refraction for Vs30?
MASW uses surface waves and works well on paved or flat ground without needing a velocity contrast at depth. Seismic refraction requires a velocity increase with depth to interpret. In North Vancouver's glacial till over bedrock, both methods work. We often recommend MASW because it is faster and needs less space.
