Inspections revealed faulty LRT concrete
O-Train boss says contractor’s quality control system is working
Inspectors have found a range of problems with concrete work at the city’s LRT sites, according to newly released inspection reports that offer a behind-the-scenes look at Ottawa’s biggest infrastructure project.
The problems relate to concrete pours at worksites such as unacceptable temperatures and missed durability tests, and have forced contractors to sometimes redo work or come up with workarounds.
The city finally released the 63 reports to Ken Rubin after he successfully convinced a provincial adjudicator that the records are of public interest. Rubin, an Ottawa access-to-information specialist, was originally stymied by the Rideau Transit Group, which didn’t want the city-held records released. The city, which agreed with Rubin that releasing the records wouldn’t cause harm to RTG, has the documents since RTG is its main contractor on the $2.1-billion LRT project.
The 644 pages of non-conformance reports largely detail deficiencies with concrete pouring activities around the maintenance and storage facility, stations and in the downtown tunnel.
All of the inspections were initiated by the construction contractor’s quality control team, making sure work completed by the subcontractors meets the city’s requirements and the RTG design. Non-conformance reports are standard documents in the construction industry, helping contractors and clients make sure the quality of work is up to snuff. They make sure the client — in this case the City of Ottawa — is getting the safe transit infrastructure it paid for.
There’s a huge amount of concrete going into the construction of the Confederation Line. The 2.5-kilometre tunnel alone is expected to have been built with 84,181 cubic metres of poured concrete when the work is done.
Several of the 63 released nonconformance reports signal deficiencies in concrete work.
After one concrete pour in the tunnel early in 2016, an inspector learned a load of concrete didn’t conform to the mix design, “causing significant damage to the running tunnel arch” in one area. An engineer told the builder to remove and replace the deficient concrete.
One report, generated after an inspection of Lyon station in July 2016, detailed an insufficient amount of concrete poured in three arches. According to the report, the concrete placement “was stopped due to concern of bulkhead failure after workers reported hearing timber cracking under the pressure of the concrete.” The builder indicated the bulkhead design would be reinforced.
The concrete must meet the city’s standards and contractor’s specifications if it’s going to be poured.
In June 2016, workers at Blair station added water to a concrete mix after more than half of the mix was discharged, leading to a nonconformance report.
That report is particularly eyeopening.
Maria Anna Polak, a professor in the civil and environmental engineering department at the University of Waterloo, said adding water to a concrete batch at the worksite is “an absolute no-no.”
“If you add extra water, this extra water contributes to lower strength. It contributes also to shrinkage, which means basically when the concrete hardens, it cracks,” Polak said in an interview.
In this case, the concrete was used as is. The contractor made sure the concrete passed the durability tests to satisfy the standards.
Durability tests are important parts of quality management and ultimately decide if the concrete is suitable.
On Sept. 14, 2015, 11 loads of concrete were delivered for workers to build a wall in the tunnel. A nonconformance report says seven of the loads poured didn’t meet the specifications for the mix design — although strength tests on the concrete passed the requirements. The inspector who wrote the report told the contractor to test the concrete before pouring it and reject trucks that don’t meet the specifications.
In December 2014, during a concrete pour of a wall at the access track to the maintenance and storage facility, seven concrete trucks were rejected because the air content of the concrete was off. Four other trucks also exceeded the aircontent limit “and had to be used to avoid major pour interruptions and cold joints,” a report says. The concrete used in the wall passed strength tests.
The temperatures of the concrete during the pouring and curing periods — the process by which the concrete is set — were also flagged in several of the non-conformance reports. In most cases, inspectors directed the contractor to monitor the concrete for any cracking and make any necessary repairs.
In summer 2016, an inspector wrote up a deficiency report for off-temperature concrete at an overpass, noting that the subcontractor was warned about not having a temperature-control plan. “However, they stated that temperature would not be an issue,” the report says.
Some reports illustrate how the contractor wasn’t able to adapt quickly to Mother Nature.
The concrete curing temperature for the new deck on the Booth Street bridge was out of whack during four unexpectedly cool evenings in May 2016. There were reports that flagged concrete poured beyond a required time threshold for discharging the mixture. In one report, the inspector noted that poured concrete was actually 23 minutes past the allowable time for pouring. Workers subsequently repaired cracks and conducted a flood test on the structure.
A few cases of poor communication also resulted in non-conformance reports.
An inspector found a cement contractor wasn’t testing the strength of the material, but the inspector also didn’t know a lab was onsite, taking tests during the pour. In another case, a technician missed testing the quality of concrete during a pour at Parliament station. There was miscommunication between a field engineer and the quality-control team, a report says.
RTG answered questions by email relating to the concrete work on the LRT project but said it couldn’t speak to specific nonconformance reports because they’re considered “internal corporate documents.”
The company said it “maintains a rigorous quality management system” to meet the city’s expectations, provisions of the LRT contract and international standards.
Asked specifically about concrete that goes past prescribed time limits between producing and pouring, RTG said it’s normal that quality inspectors find issues related to the product or process.
“Given the logistics of delivering and placing large volumes of concrete it is inevitable, on any project, to have some loads exceed time limits,” RTG says. “There are options in those cases, one of which is to reject the load.”
Non-conformance reports also warn about formwork — the mould for concrete — being removed too early during the curing period, wrongly installed reinforcing bars and deficiencies on girders at the Hurdman station elevated guideway.
Questionable waterproofing is another common problem in the reports.
A report from 2015 noted missing strips of membrane in Parliament and Lyon stations. The supplier was told to follow the approved drawings.
Another report that year flagged a problem with a design-required redundant “waterstop” in a construction joint at Lyon station. The work was allowed. The builder is “proceeding at their own risk of damage due to water infiltration,” the report says.
At the connecting line to the maintenance facility, an inspector found there was no waterproofing installed in areas that underwent emergency repair in 2015.
It’s in RTG’s interests to make sure the LRT system is built properly since the company also has a 30-year maintenance contract from the city.
Steve Cripps, the city’s director of O -Train construction, said the non-conformance problems were raised by RTG’s construction arm, Ottawa Light Rail Transit Constructors, which shows the builder’s quality-management system is working.
“The city has reviewed the documentation provided by the Ottawa Light Rail Transit Constructors for each (non-conformance report) and is satisfied that they have conducted the appropriate due diligence,” Cripps said in an email.
The builder is scheduled to deliver the LRT system to the city by Nov. 2. It’s the second deadline after RTG couldn’t meet the previous May 2018 delivery date. The city plans to have the rail line open to passengers by the end of November, but it should have a better idea by the end of the summer if RTG will meet the new deadline.