The Ministry of Transportation is investigating the condition of at least three MSE ( Mechanically Stabilized Earth) retaining walls along the Sea to Sky Highway, according to sources close to the project.
This action finally comes after specific Ministry employee’s received the photos shown below – in February of this year – that show clear flaws, deficiencies and structural concerns that sources indicate out-of-spec walls. Major defects show large open gaps in the concrete panels, water seepage behind walls, walls that are “out of batter” ( leaning the wrong way) and possible vertical movement of the walls. *terminology link found here for reference.
In some areas, the gaps are so wide that the tongue and groove elements are no longer meshed and it is possible to reach in and feel the geotextile cloth behind. While the photos were taken earlier this year in a cold snap, follow-up visits during rainy weather have shown very little water coming out of installed drainage pipes installed for such purpose, and a build up of water behind the wall with seepage from under the wall in other areas.
In speaking with several industry sources who have assisted me on prior MOT project stories ( who would only speak off the record fearing reprisals or backlash in the industry), the photos are concerning for two reasons.
First, these type of MSE retaining walls should be built to spec to last for approximately 70 years. That these walls are showing sign of defects within years of construction is not acceptable,nor is it standard. Sources indicate this is above and beyond what would be normal settlement.
Water and faulty construction are two major reasons behind MSE retaining wall failures.
Water on its own, not properly directed via drainage conduits to exit or bypass the wall in specific areas, can undermine the backfill behind a wall, leading to serious erosion and the potential for wall failures. Water can cause irreparable damage to retaining walls if not controlled and directed and can have catastrophic consequences, as this engineering publication details :
“When water flows
About 90 percent of soil problems are really water problems. Most retaining wall failures occur during heavy rainstorms. Recently, a 43-foot-tall “big block” MSE wall failed during a heavy rain just eight months after it was built, launching 2,400-pound blocks more than 50 feet when the wall popped. This wall failed during a storm, even though it had survived earlier, heavier rains. It appears that the earlier storms caused the wall’s drains to clog, and therefore this subsequent storm contributed to the failure.”
Water is also incredibly destructive in the winter freeze/thaw cycle – winter freezing in this case will continue to damage these walls, pushing the panels further apart because as water freezes, it expands with a tremendous force. Follow that up with typical heavy rains and spring melt run-off and it doesn’t take an engineer to tell you there could be a big problem.
This is why the drainage systems in the walls are so important,and why it needs to be determined why some of the drains on these walls are not working. Sources indicate the backfill on some of these walls may have been over-compacted by over-loaded rock trucks used to bring the fill on site. If the drainage system was damaged or crushed by too much weight, or improperly engineered, the drainage issues will continue, as will costly damage.
The second issue on these walls is one of accountability.
With all the ” Value for Money” touted by Partnerships BC on the Sea to Sky highway improvement project, where is the value in a retaining wall that allegedly doesn’t meet the standards for a 70 year life? Who inspected this wall and signed off on it? There is no monitoring equipment on the wall, how often are these walls inspected? Who did the quality control? At this point, the question of who would be liable at this point comes into play as the Province of BC signed off on the final project.
This isn’t the first retaining wall Kiewit has had issues with locally.
In 2011, Kiewit had to tear down and rebuild parts of a retaining wall that was found to be ” structurally unfit” along Lougheed Hwy, on the Port Mann Highway One project. According to Transportation Investment Corporation – the crown corporation overseeing the project- Kiewit was to cover the entire cost of the repairs.
Kiewit has also been involved in litigation in the U.S. following the massive failure of one retaining wall, that lead to the tear down and replacement of another 14 retaining walls along the Caltrans 405 Freeway project in California.
” Kiewit, SSL, as well as the project’s designer, global firm HNTB, are in all court, suing one another. In court documents, Kiewit alleges the wall system was “deficient and defective.” SSL has stated the “drain design and installation were inadequate” at the site where the wall collapsed, according to the Caltrans report.”
Internal ministry sources indicate Transportation Minister Todd Stone is aware of this issue and has also seen these photos.
While sources indicate that the retaining walls shown in these photos are not likely to suffer a catastrophic failure, the photos are concerning because in some areas below the retaining walls, there are homes. There is no crash wall below these retaining walls either, to prevent a vehicle that might go over the edge from crashing completely down the slopes below. There is no guarantee what would happen in an earthquake, or following heavy rains and runoff, which is why these issues need to be addressed.
Considering there are 219 MSE retaining walls on this project, finding signs like this in just three walls easily accessible, raises questions to the status of all the walls, in particular because of the very tight construction deadlines on this project and Kiewits history.
After all, since we are all paying for this highway everytime someone travels it, via the ‘ shadow toll’ portion of the payment to the concessionaire, I think the public is entitled to a little more than lip service on this one.