If you're developing property anywhere around the Truckee Meadows, you quickly learn that Reno's basin geology isn't something you can guess at from a distance. The valley floor here is a deep sedimentary basin, and a lot of the fill we encounter is layered alluvium brought down by the Truckee River over thousands of years. When an engineer calls our lab and asks whether a site is Class C or Class D, we don't give them a textbook answer. We schedule a MASW survey because the shear wave velocity profile is the only way to know for sure what the IBC seismic site class actually is. We run the line, process the dispersion curves, and give you a VS30 number that holds up with the city's plan reviewers. For deeper characterization, we'll sometimes follow up with seismic refraction to cross-check the bedrock depth in areas where the basin edge pinches out against the foothills.
A VS30 number without the dispersion curves and raw gathers is just a guess. We deliver the full dataset.
Service characteristics in Reno
Typical technical challenges in Reno
ASCE 7-22 Chapter 20 is the governing document for site classification, and in a high-seismicity city like Reno, getting the wrong site class can cascade into a foundation design that's either dangerously unconservative or so overbuilt it kills the project budget. The Mount Rose fault system and the Mogul earthquakes are recent reminders that the basin amplifies ground motion in ways that a simple soil description from a drill log can't capture. We've pulled MASW lines where the VS30 came back at 250 m/s on one side of a parcel and 380 m/s on the other, just because the alluvial layering changed across a paleochannel. That difference flips the site from Class D to Class C, which changes the seismic design category and the lateral force demands on the structure. The city of Reno and Washoe County both require IBC-compliant site classification as part of the building permit submittal, and they'll reject a report that doesn't show the raw data and the inversion parameters.
Our services
Our Reno MASW program covers the full workflow from field acquisition to a stamped report. We handle small single-family lots and multi-acre commercial parcels the same way: clean data, defensible picks, and a site class determination that the structural engineer can plug directly into their model.
VS30 Site Classification
Active-source MASW survey with 24- or 48-channel array. We process on-site to verify data quality, then deliver a signed report with the VS30 value, the shear wave velocity profile, and the IBC site class per ASCE 7-22.
Liquefaction Screening Support
Shear wave velocity data integrated with CPT or SPT logs to evaluate liquefaction potential using the Andrus & Stokoe procedure. Useful for sites in the North Valleys where shallow groundwater and loose sands are common.
Deep Basin Characterization
Extended-offset MASW arrays to resolve velocity structure to 40 meters or more, targeting the basin-fill contact. We correlate with available well logs and USGS basin-depth models for the Truckee Meadows.
Combined Geophysical & Geotechnical Program
MASW paired with test pits or SPT drilling on the same grid. We manage the subcontracting, the utility clearance, and the coordinated report so you get one deliverable instead of three.
Common questions
What does a MASW survey cost for a typical Reno lot?
For a standard single-family lot with a single MASW array, the cost generally runs between $1,890 and $2,720. The exact number depends on access, the number of spreads we need to run to characterize the whole building footprint, and whether the site has a lot of buried utilities that require extra GPR clearance time. We'll give you a fixed-price quote after a quick site visit.
How long does the field work take, and how soon do I get the report?
The field acquisition for one array takes about two hours with a two-person crew. We process the data the same day and typically deliver the draft report within three business days. If you're on a tight submittal deadline, we can expedite the final stamped report.
Will the city of Reno accept an MASW-based site class determination?
Yes. The city of Reno and Washoe County both accept IBC site classification based on shear wave velocity measured by active-source MASW, provided the report includes the raw shot records, the dispersion curves, the inversion parameters, and the VS30 calculation. We've submitted dozens of these packages and the reviewers are familiar with the method.
Can you run the survey if the ground is frozen or covered in snow?
MASW relies on good geophone coupling with the ground surface. A light frost overnight is usually not a problem, but frozen ground deeper than a couple of inches or heavy snow cover will degrade the data. We schedule around the weather, and in winter we typically run surveys during the mid-day window when the surface has thawed.