Pattullo Bridge Replacement Project – Underhill Geomatics

The Pattullo Bridge Replacement Project is currently undergoing a detailed design process and as you can see from the artist’s rendering the new bridge will have two in-river piers, reduced from the six piers the current bridge has in the river.  

Northwest Hydraulic Consultants (NHC) was contracted to build a 1/80 scale model of the existing Skytrain, Pattullo and CN Rail bridge pilings, on the river bed so that hydraulic impacts can be tested and evaluated on the new bridge pilings, as well as the upgrades to the CN railway pilings for earthquake preparedness. 

The model is representative of what water in the Fraser River will do in relation to the new bridge structures and tests various construction and environment scenarios. 

A summary of the process: 

  • NHC built the original model 
  • Underhill performed the initial 3D laser scan to determine the current state of the river bed to ensure it was accurate to as is data 
  • Then NHC added the new proposed structures and performs tests by flooding the model with varying water levels, current speeds etc.  
  • Our team at Underhill is brought in each time a test has been completed to scan the resulting changes to the river bed after the flow has been drained. The new data are transformed as a digital surface which is overlapped on the reference river bed to reveal the changes.  

Underhill has been scanning this model regularly for NHC after each test for 4 years now. You can see in the images the targets we place on the facility walls in order to precisely match each scan overlay to the previous scenarios and the baseline. As the bridge is currently undergoing design refinements, we cannot show the model in full detail, however it’s very interesting to see the effects each test has on the river bed and how our 3D scanning technology is being used to provide accurate data to NHC for their testing. 

More information on the Pattullo Bridge project can be found here: https://engage.gov.bc.ca/pattullobridge/ 

If you’d like to learn more about Underhill’s 3D scanning capabilities please contact us today.