In­spec­tions re­vealed faulty LRT con­crete

PressReader - Tke Channel - In­spec­tions re­vealed faulty LRT con­crete
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.

In one case, a tech­ni­cian missed test­ing the qual­ity of con­crete dur­ing a pour at Par­lia­ment sta­tion, shown here dur­ing its ex­ca­va­tion in 2016.

It’s in RTG’s in­ter­est to make sure the LRT is built well as the com­pany has a 30-year main­te­nance con­tract with the city.

Work­ers pour con­crete cais­sons north of the ex­ist­ing Hur­d­man Sta­tion for the LRT project.

Crews form the stairs at Blair Sta­tion.

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