2007 Fatality Report: Workers Crushed by Collapse of · PDF fileWorkers Crushed by Collapse of...

Workers Crushed by Collapse of Tank Roof Support Structure Date of Incident: April 24, 2007 Type of Incident: Double Fatality

2 Serious Injuries 3 Minor Injuries

TABLE OF CONTENTS PAGE NUMBER

SECTION 1.0 DA TE AND TIME OF INCIDENT 3

SECTION 2.0 NAME & ADDRESS OF PRINCIPAL 3 ST AKEHOLDER(S) - Owner(s) - Prime Contractor - Employer(s) - Stakeholders

SECTION 3.0 DESCRIPTION OF PRINCIPAL 4 STAKEHOLDER(S)

SECTION 4.0 LOCATION OF INCIDENT 6

SECTION 5.0 EQUIPMENT AND MATERIAL INVOLVED 7

SECTION 6.0 NARRATIVE DESCRIPTION OF INCIDENT 8

SECTION 7.0 ANALYSIS 12

SECTION 8.0 APPLICABLE LEGISLATION 14

SECTION 9.0 FOLLOW-UP/ACTION TAKEN 17

SECTION 10.0 SIGNATURES 18

SECTION 11.0 ATTACHMENTS 18

2 September 27, 2007

File: F-536919

Section 1.0 DATE AND TIME OF INCIDENT

1.1 April 24, 2007, approximately 2:30 p.m.

Section 2.0 NAME & ADDRESS OF PRINCIPAL STAKEHOLDER(S)

2.1 Owner(s)

2. 1. I Canadian Natural Resources Limited 2500-855 2 Street SW, Calgary, Alberta T2P 418

2 .2 Prime Contractor

2.2. l Canadian Natural Resources Limited Horizon Oil Sands Corporation (CNRL Horizon) PO Bag 4025, Fort McMurray, Alberta T9H 3H5

2.3 Employer 1

2.3. 1 SSEC Canada Ltd. (SSEC Canada) #1800, 250-6 A venue, Calgary, Alberta T2P 3H7

2.4 Employer 2

2.4. l Tenth Construction Company of Sinopec (TCC) PO Box #132, Zibo, Shandong, China 255438

2.5 Stakeholder 1

2.5. 1 Sinopec Shanghai Engineering Company Ltd. (SSEC China) 769 Zhangyang Road, Pudong New Area, Shanghai, China

2.6 Stakeholder 2

2.6.1 China Petroleum and Chemical [Petrochemical] Corporation (Sinopec) PO Box 3013, Beijing 100011, China

2.7 Stakeholder 3

2.7.1 The Zachry Group Suite 250, 700 Sixth Avenue SW, Calgary, Alberta, T2P OT8


File: F-536919

2.8 Stakeholder 4

2.8.1 Zachry Energy International Inc. 1238, 13351 Commerce Parkway, Richmond, British Columbia V6V 2X7

2.9 Stakeholder 5

2.9.1 TIW Division of Canadian Erectors Ltd. (TIW) 23 Smith Street, St. Catherine's, Ontario L2R 6Y6

Section 3.0 DESCRIPTION OF PRINCIPAL STAKEHOLDER(S)

3.1 Canadian Natural Resources Limited (CNRL)

3 .1.1 CNRL is a senior independent oil and natural gas exploration, development and production company based in Calgary, Alberta.

3.1.2 The CNRL Horizon Oil Sands Project is located approximately 70 km north of Fort McMurray and 30 km north of Fort MacKay, Alberta. CNRL owns and operates leases covering approximately 115,000 acres and will use open pi t mining methods to mine oil sands. A plant is being constructed that will separate raw bitumen from the oil sands and upgrade the bitumen to a synthetic crnde oil using delayed coking and hydro-treating technologies. Phase 1 started in 2005 and is scheduled for completion in 2008, ramping up to produce 11 0,000 barrels of synthetic crude oil per day. Phases 2 and 3 wi ll proceed until projected completion in 20 12. Phase 3 is expected to bring production to 232,000 barrels of synthetic crude oil per day. At the time of the incident approximately 6,000 workers were working on the construction of the project.

3.2 SSEC Canada Ltd. (SSEC Canada)

3.2.1 SSEC Canada is an Alberta corporation. The company was incorporated in April, 2006 to bid for work in the Alberta oil sands. The company is 90% owned by SSEC China, a Chinese company, and 10% owned by Zachry Energy International Inc., a company based in British Columbia. SSEC Canada uses management, technical and journeyman workers drawn from SSEC China and Tenth Construction Company of Sinopec (TCC), working in Alberta as temporary foreign workers, to carry out projects such as the tank farm project at the CNRL Horizon Oil Sands Project.

3.2.2 SSEC Canada was contracted by CNRL Horizon to construct a total of 14 tanks, 11 on the east tank farm and 3 on the west tank farm at the CNRL Horizon Plant Site. The effecti ve date of the contract was April 11 , 2006. SSEC Canada was expected to have workers available July 2006 to commence the tank assembly at the west tank farm. Work on the three tanks at the west tank fan11 was scheduled for completion by September, 2007.


File: F-536919

3.2.3 The three tanks on the west tank farm were being constructed in accordance with a tank erection schedule prepared by CNRL. The schedule specified a sequence of construction where the tank floors were laid, the walls were started and the internal roof support structures were erected. SSEC Canada was required to construct the tanks in accordance with the tank erection schedule, and in accordance witb component and material schedules and engineered drawings provided by TIW. The TIW drawings showed how the components and materials they had supplied fitted together. SSEC Canada was responsible for the direction of their workers, which included giving instructions on how component parts of the roof support structure were to be suppotied from movement or falling until the construction was complete and the tank assemblies were self-supporting.

3.3 Tenth Construction Company of Sinopec (TCC)

3.3. l TCC is an industrial construction company in China, specializing in the construction and installation of petroleum refining projects. TCC has undertaken construction projects in Africa, Asia and Saudi Arabia.

3 .4 Sinopec Shanghai Engineering Company (SSEC China)

SSEC China is a Chinese company based in Shanghai, China. SSEC China has the capacity to undertake mid to large engineering projects including projects in the petrochemical industry. SSEC China has some contacts with engineering companies internationally. SSEC China own a 90% share of SSEC Canada and exercises full control of all activities of SSEC Canada. The Horizon tank project was sub contracted to TCC by SSEC China. All workers were recruited by TCC. Most construction management personnel were employed by TCC. SSEC China employed one business representati ve in Calgary to dea l with the finances and one secretary at the CNRL site.

3.5 Sinopec China Petroleum and Chemical !Petrochemical! Corporation (Sinopec)

3.5 .1 Sinopec is the largest producer and marketer of refined oil products in China and Asia, and is the largest producer and distributor of petrochemicals in China. Sinopec is a state-owned Chinese corporation, is the second largest oil and gas explorer in China, and is the parent company of both TCC and SSEC China.

3.6 The Zachry Group

3.6.1 The Zachry Group is an Alberta registered company that designs and manufactures equipment fo r the oil and gas, pulp and paper, sawmills and mining industries.


File: F-536919

3. 7. Zachry Energy International Inc.

3.7.1 Zachry Energy International Inc. is a British Columbia registered company that is 60% owned by the Zachry Group. Zachry Energy International Inc. provides overview and management input to SSEC Canada and is 10% shareholder ofSSEC Canada. Zachry International Inc. focused on helping SSEC China to liaise with CNRL and to penetrate the oil and gas construction market in Alberta. They were responsible to assist SSEC China to li aise with CNRL and assist with requirements of training of the trade workers. They were responsible to assist SSEC China workers to obtain work visas, and coordinated with Alberta Apprenticeship and Industry Training (AAIT) requirements for designated trades. They assisted SSEC China to set up SSEC Canada Ltd. , and assisted SSEC Canada Ltd. with obtaining legal counsel to help the company deal with local regulations and laws in connection with their establishment in Alberta. In March of 2007 Zachary Energy International Inc. relinquished its 10% share of SSEC Canada. SSEC China and Sinopec requested that Zachary Energy International Inc. be the lead contact for SSEC Canada in relation to the investigation of WHSC with respect to the April 24, 2007 incident at the CNRL Horizon site.

3.8 TIW Division of Canada Erectors Ltd. (TIW)

3.8. l TIW is engaged in the fabricat ion, construction and distribution sectors of the steel industry. TlW is a fully integrated unit for design, manufacturing, and construction of fi eld erected steel platework structures. TIW was contracted byCNRL to provide the components, material schedules for arrival on site, and the engineered drawings for the 14 tanks on the east and west tank fanns at the CNRL Horizon plant site.

3 .8.2 The roof support structures were all fabricated " in house" by TIW at their faci Ii ties, with the exception of the welding of columns to the cap plates, which was perfo1med by Bartonair Fabrications of Hamilton. Bartonair is a regular supplier to TIW. Bartonair was required to use TIW supplied materials, consumables and welding procedures. TIW inspection personnel reviewed the materials before shipment. TIW coordinated the identification, packaging and shipment of the roof support structures (including columns) to the CNRL Horizon site.

Section 4.0 LOCATION OF INCIDENT

4.1 Tank 72-TK- l B, located on the west tank farm of the CNRL Horizon Oil Sands Project, approximately 70 km north of Fort McMurray and 30 km north of Fort MacKay, Alberta.


File: F-5369 19

Section 5.0 EQUIPMENT AND MATERIAL INVOLVED

5.1 The West Tank Farm

5 .1 . I The west tank farm is located approximately northwest of centre on the Hori zon Plant Site. (Attachment "C", Site Layout). As the tanks had restricted means of entry and exit and could become hazardous to workers entering them, they were designated as confined space. Three high-cone steel tanks, Tank 72-TK-lA, 72-TK- IB and 72-TK-1 C are located on the west tank farm, in a line east to west with Tank 72-TK-1 A at the west, Tank 72-TK- lB in the centre and Tank 72-TK- lC at the east end of the row of tanks. The tanks are all the same size and of the same construction. At the time of the incident the roof support structure in tank 72-TK- l B was in a suspended state of completion with the centre support column, the inside ring of 6 support columns and the outer ring of 12 support columns in place, with the girders and rafters fitted, waiting for the shell assembly to be completed. Once the shell assembly was completed, the rafters from the outer ring's girders would be connected to the shell wal 1. The roof support structure in tank 72-TK-1 B had been completed the day before the collapse. At the time of the incident a team of boilermakers and scaffolders was working in Tank 72-TK-1 C on the assembly of the roof support structure. (Attachment "A'', Photographs #1 1, #15)

5.2 The East Tank Farm

5.2.1 The east tank farm is located at the east of the Horizon Plant Site (Attachment "C'', Site Layout). When completed, the east tank farm will contain 10 tanks of various sizes, and of generally similar construction to the tanks on the west tank fann. At the time of the incident, the roof support structures in two tanks on the east tank farm, Tank 73-TK-11 and 73-TK-12 were also in a suspended state of assembly waiting for the shell walls to be competed. After which they would connect the rafters from the outer rings' girders to the top of the shell walls. (Attachment "A", Photograph #17)

5.3 Tank 72-TK-tB

5.3. 1 Tank 72-TK-l B (described as a Dilbit Dewatering Tank), located on the west tank farm, was to be a circular steel high-cone roof tank, 56.5 mi n diameter and 19.8 m high. At the time of the incident the tank wall shell was only completed to a height of 5.6 m. The tank structure consists of wall, floor and roof constructed from steel plate. The roof is constructed onto a roof support structure cons isting of vertical circular columns, supporting girders and radial rafters. (Attachment "D", Sketch of Roof Support Structure). The components of the roof support structure are assembled together with 19 mm (:X inch) nuts and bolts . At the time of the incident a team of welders was working in the tank constructing the tank wall. Two technicians were also in the tank carrying out weld testing, and one scaffolder was in Tank 72-TK-l B. There was an Electri cal Consultant and a welding foreman who were checking out a welding machine on top of the wall .


File: F-536919

5.4 Assembly Procedure for Tanks

5.4. 1 SSEC Canada developed a procedure for assembling and supporting the tank roof support structures for the tanks on the west tank farm. Erection of the shell was independent of the roof support structure - they were being assembled concurrently. The procedure consisted ofraising the centre support column first, using a crane and securing it in the ve1iical position by workers operating elevating work platfo1ms to install 4 steel cables, secured to the top of the column and anchored to lugs welded onto the tank floor. The cables were tightened using "come-alongs". ("Come-along" is a generic tenn to describe mechanical tensioning devices). The inner ring of 6 support columns was erected in a similar manner, but with 3 cables on each column. The girders connecting the inner ring of columns were then lifted and bolted into place, using 19 mm (:y.; inch) bolts, and the radial rafters were installed between the centre column and the inner ring. After the inner ring was completed, one cable, extending towards the tank centre, was removed from each of the 6 inner ring columns. The outer ring of 12 columns was erected, using 3 cables to support each column. The girders connecting the outer ring of columns were lifted and bolted into place, and all of the radial rafters were installed. After the outer ring of the roof support structure was assembled, 6 steel cables were installed, extending from girders to alternate columns in the outer ring to anchor lugs welded into the floor of the tank, close to the tank wall. When these 6 support cables were in place and tightened using "come-alongs'', all of the cables used to support the individual columns were removed. The six cables remaining were intended to support and stabilize the roof support structure until the shell was completed to ful l height. The "come-alongs" were removed after the cables had been tightened.

Section 6.0 NARRATIVE DESCRIPTION OF INCIDENT

6. 1 SSEC Canada recruited 132 Mandarin-speaking Chinese workers from TCC to work as temporary foreign workers on the CNRL tank construction project. The workers had at least 5 years experience as trades-people and had received additional training from a Canadian training agency before arriving in Canada. The workers started to arrive in Canada in September of 2006.

6.2 On April 24, 2007, at the west tank farm, the roof support structures in tanks 72-TKlA (Attachment "A", Photograph #11) and 72-TK-lB were in the suspended state of completion waiting for the shell to be assembled. Each roof support structure was supported by six cables. The roof support structure in tank 72-TK-lC was being assembled. The centre column and the inner ring had been completed and the steel cables were still attached to the columns. No work was taking place in Tank 72-TKl A on April 24, 2007. A team of boilermakers was working in Tank 72-TK-I C, assembling the roof suppo1t structure. (Attachment "A", Photograph #15)


6.3

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6.5

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On April 24, 2007, a team of welders was working in tank 72-TK-1 B, welding sections into the tank wall. The tank wall sections were being welded together by welders and helpers working inside welding machines that tracked around the inside of the tank wall. (Attachment "A", Photographs #20, #21) One Electrical Consultant and a welder foreman were inside the tank checking an electrical fai lure on one of the welding machines. One scaffolder was also on the floor area inside the tank. Two weld test technicians were also in Tank 72-TK-1 B, testing and marking the welds on the tank wall.

At approximately2:30 p.m. on April 24, 2007, workers inand around tank 72-TK-lB heard several sounds, described as loud bangs or pops. The roof support structure in tank 72-TK-1 B started to fal l in an easterly direction during windy conditions. As the structure collapsed, some of the support cables failed, many of the bolts that were holding the components together failed and then the components began to come apart. (Attachment "A", Photographs #8, #9, #10, # 22) The structure fell onto the east side of the tank wall. Some of the components of the roof support structure can1e to rest on the floor of the tank, some components came to rest leaning against the tank wall , and some components came to rest on the outside of the tank on the east side. Many of the components were bent or damaged by the impact. After the roof support structure collapsed some of the workers, who were in tank 72-TK-1 B, managed to escape from the tank through manways or other holes in the tank wal I. (Attachment "A", Photographs #1, #2, #3, #4)

SSEC Canada workers from tank 72-TK-.1 C and other workers on the west tank farm, as well as workers from other contractors who were working near the west tank fa1m, went to tank 72-TK-lB to provide assistance. CNRL Horizon emergency services were called and attended. Rescuers had to lift a large section of steel inside the tank to remove the fatally injured Scaffolder. The Electrical Consultant was standing on the top of a welding machine, which was located on top of the wall, and was fatally injured when he was struck by falling steel. His body was thrown onto scaffolding outside the tank. The Electrical Consultant was pronounced dead at the scene. The Scaffolder, who was on the tank floor, was crushed by the falling steel and died in an emergency conveyance vehicle on the way to Fort McMurray. Two other workers received serious injuries and three more workers received minor inj uries. The two seriously injured workers and two of the workers who had received minor injuries were transported to hospital in Fort McMurray. The two seriously injured workers were subsequently transferred to hospital in Edmonton.

6.6 INVESTIGATION OBSERVATIONS AND INFORMATION

6.6. 1 Workplace Health and Safety Compliance (WHSC) was notified of the incident by CNRL Horizon at 3:08 p.m. on April 24, 2007. Workplace Health and Safety officers from Fo1t McMurray were dispatched to the scene and while en route made contact with RCMP Fort McMurray Detachment. WHSC officers arrived at the site at 5: 19 p.m. The scene had been secured by CNRL and RCMP.


File: F-536919

6.6.2 WHSC issued a verbal Stop Work Order to CNRL at 8:36 p.m. on April 24, 2007. The Stop Work Order was for construction of the three tanks on the west tank farm and any similar tanks on the Horizon site.

6.6.3 On April 24, 2007 a WHSC Lead Investigator was dispatched from Edmonton to direct the investigation. The Lead Investigator atTived at the CNRL Horizon Oil Sands Project at 9:00 a.m. on April 25, 2007. CNRL Horizon set up an internal investigation team and met with the Lead Investigator and other Workplace Health and Safety offi cers on April 25, 2007. The Lead Investigator confi rmed the verbal Stop Work Order and reminded CNRL Horizon that no workers were to enter the area and to have the area secured.

6.6.4 On April 25, 2007 a second WHSC Lead Investigator, the WHSC Manager of Compliance, and an employee from another Govenunent of Albe1ta depa1tment, who speaks Mandarin, were dispatched from Edmonton to assist with the investigation. The second Lead Investigator, the Manager and the other employee arrived at the CNRL Horizon plant site at 6:00 p.m.

6.6.5 It was found that there had been 13 workers inside tank 72-TK-lB at the time the incident occurred. Ten workers were Chinese temporary foreign workers employed by SSEC Canada, one Chinese worker (the Electrical Consultant) was directly employed by TCC and two workers were Canadian workers employed by Iris NDT, carrying out weld testing. All of the fatally injured and other injured workers were Chinese temporary foreign workers. SSEC Canada workers and others who had attended the scene were interviewed over a period of several days, in order to determine the circumstances of the incident and the locations of all of the workers who were inside the tank at the time of the incident. It was found that the workers had carri ed out the assembly of the roof support structures in accordance with SSEC Canada's chief engineer's instructions and the assembly drawings provided by T IW.

6.6.6 One of the fatally injured workers, an Electrical Consultant, had been on the top of a welding machine working on the east side of the tank wall. The Electrical Consultant had been struck in the head and back by a section of the falling steel and thrown onto scaffolding outside the east wall of the tank. The other fatally injured worker, a Scaff older, had been standing on the tank floor, east of the tank centre, and had been caught and crushed under a falling girder. Rescuers had manually lifted the girder to rescue him. The Scaffolder died during transport to hospital. (Attachment "A", Photographs #4, #5, #7)


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6.6.11

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One of the seriously injured workers, Welder l , had been inside the same welding machine that the Electrical Consultant was working on. The welding machine })ad been struck by fall ing steel and partially dislodged from the tank wall. Welder 1 was trapped inside the welding machine and was rescued by CNRL staff and other contract workers. The other seriously injured worker, Welder 2, was inside another welding machine on the east wall that had been struck by falling steel and completely dislodged from the wall, falling to the tank floor. Welder 2 was rescued by his Chinese co-workers. (Attachment "A", Photographs #5, #6)

The verbal Stop Work Order was confirmed in writing on April 27, 2007. The Stop Work Order prevented access to the east and west tank farms. The Stop Work Order was re-issued on May 1, 2007 to define a specific part of the east tank farm around tanks 73-TK-1 l and 73-TK 12 where workers could be at risk from the collapse of the roof support structures. The remainder of the east tank farm was released to CNRL. The Stop Work Order for the west tank farm remained in effect. CNRL cooperated with the Stop Work Orders and provided barriers and security staff to ensure that the order was made effective.

On May 12, 2007 the roofsuppo1t structure in tank 72-TK-lA on the west tank farm collapsed during windy conditions. The Stop Work Order was still in effect and no workers were near the collapse. Before the collapse it had been observed that the roof support structure was twisting during windy conditions. (Attachment "A", Photographs # 18, # 19)

CNRL developed an engineered procedure for securing and dismantling the roof support structures in tanks 73-TK-1 l and 73-TK-12 on the east tank farm. The Stop Work Order for the east tank farm was lifted on May 16, 2007 and the site was released to CNRL Horizon to enable the remediation work to be done. The work on dismantling and removal of the roof support structures was completed on June 11 , 2007 by SRS Industrial Services Ltd.

CNRL developed an engineered procedure for the removal of fallen materials in tanks 72-TK-lA and 72-TK lB and the dismantling of the roof support structure from tank 72-TK-l C. The Stop Work Order for the west tank farm was lifted on June 6, 2007. Work on tank 72-TK-I A commenced on June 8, 2007 and was completed on June 13, 2007. Work then sta1ted on tank 72-TK-I B and was completed on June 20, 2007. The removal of the roof support structure in tank 72-TK-l C was completed on June 22, 2007 by Penny Industrial Fabricators Ltd. The WHSC Lead Investigator monitored the removal of the fallen materials from tanks 72-TK-1 A and 72-TK-1 B and during the removal retri eved materials from both tanks for analysis by an independent consulting engineering firm.


File: F-536919

Section 7.0 ANALYSIS

7 .1 Direct Cause

7 .1.1 Two workers working on the construction of a large steel tank 72-TK-1 B were fatally injured, two other workers were seriously injured and three workers received minor injuries when the roof support structure inside the tank collapsed suddenly and without warning onto the workers.

7 .2 Contributing Factors

7 .2. 1 SSEC Canada assembled the roof support structure as a stand alone structure, which was not intended to be assembled as such by the TlW drawings. Neither CNRL nor SSEC Canada consulted with TIW with respect to what assembly sequence should be fo llowed for the construction of the roof support structure. As the erection of the shell was independent of the roof support structure and they were being assembled concun-ently, the top of the shell and the outer ring were not supporting each other.

7.2.2 TIW did not specify an erection sequence to follow to erect the tank they designed. TIW did not specify the assembly sequence because that was not part of the contract with CNRL.

7 .2.3 CNRL prepared a tank erection schedule specifying the sequence of construction such as when the tank floors were to be laid, the walls to be started and the internal roof support structures were to be erected. SSEC Canada followed the tank erection schedule as set out by CNRL.

7.2.4 SSEC Canada did not provide written engineered erection procedures for the assembly of the roof support structure. CNRL did not require SSEC Canada to provide written engineered assembly procedures.

7 .2.5 The SS EC Canada chief engineer who developed the erection procedure for the roof suppo1i structures and specified the number, size and location of the guy wires was not a qualified professional engineer.

7.2.6 The roof support structure was a completely bolted structure using ASTM A-307 Grade B bolts without the use of wedges or washers. The bolted roof support structure, which was required to be flexible, did not have the necessary restraints to resist the lateral forces generated by the wind.

12 September 27. 2007

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7.2.11.1

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The number and size of guy wires that were supporting the roof support structure in tanks 72-TK- IA and 72-TK-1 B, was not designed for the static and dynamic loads imposed by the 33 to 45 km/h wind that occurred on the day of the incident, let alone for the maximum expected wind speed of 83 km/h, as determined by the Alberta Building Code or 190 km/h recommended by the American Petroleum Institute. (Attachment " A", Photographs # 12, #13, #14, #16)

There were six guy wires wrapped around girders located near the outer ring columns to stabilize the roof support structure. Three of the guy wires were aligned in a rad ial direction through the centre column axis; however, the other three guy wires were significantly offset from radial alignment and were angled in the same direction by 14° to 24°. Because of the offset alignment, this action would result in forces attempting to twist the roof support structure in a clockwise (easterly) direction, which is the direction of the eventual collapse.

Because of the flexible bolted structure, any movement caused by the wind, would provide means to loosen the nuts on the bolts as well as intensify the twisting force on the guy wires .

Examination of the roof support structures in tanks 72-TK-1 C, 73-TK-1 l and 73-TKl 2 showed that many of the bolts used to assemble the structures were loose; some bolts had become bent during tightening, or necked because the thread length was to short. o washers or bevelled washers were used in the assembly of the roof support structure.

On April 25, 2007 Workplace Health and Safety Compliance contracted Anderson Associates Consulting Engineers Inc. to examine the circumstances leading to the collapse of the roof support structure in tank 72-TK- l B. The Professional Engineer's report summarized the following causes:

The collapse was primarily the result of inadequate guy wires used as wind bracing on the partially assembled flexible roof structure. As wind speeds increased, the flexible roof structure began to load the guy wires. Due to the structure's flexibility and the unbalanced load conditions (the unbalanced geometry of the channel rafters and the poor alignment of guy wires with the structure), the roof oscillated in the wind. This movement of the 127 metric ton roof structure imparted cyclic loading onto the guy wires. The upwind guy wire failed first as the wire rope clips became overloaded and slipped toward the floor attachment lug. Once the structure was able to move out of position, it collapsed in a downwind direction-essentially blown over.


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7 .2. 11 .2 The design of the guy wire wind bracing was based on API 650 calculation methods. These methods are inadequate for structural steel stability, although they are suitable for their intended use (tank stability). As a result, the designer, who was not a professional engineer, determined that there was minimal need for wind bracing. Only six 12.5 mm (half inch) guy wires were used to brace the structure against wind loads. These were neither aligned to prevent rotation of the structure nor sized with a normal safety factor. When the wind speed increased, the structure began to oscillate and the guy wires were overloaded by the inertia of the structural steel's movement.

7.2.11.3 Bracing to make the structure more rigid was not installed by the erector. This or other temporary cross-bracing may have helped prevent or reduce the oscillation that led to the inertial load. More wind bracing, in tenn s of guy wires or structural steel cross-bracing, would have been required to prevent the incident.

7.2. 11 .4 The incident was not caused by material failure of the wire ropes, fi ttings or erection equipment. Testing of the wire rope and wire rope clips confinned their design capacity. Damage to the structural steel was all a result of the incident. The A-307 B bolts used to connect the structural steel were proper strength when tested. They had failed as the structure collapsed. It is unlikely that stronger bolts alone would have provided the rigidity required to prevent the incident.

Section 8.0 APPLICABLE LEGISLATION

8.1 Occupational Health and Safety Act, Section 2(1)(a)(i) Obligations of employers

8.1.1 SSEC Canada did not take reasonably practicable measures to protect the health and safety of all the workers who were working inside the tank when the incident occurred. The tank roof support structure that collapsed onto the workers was a skeleton structure. The erection procedures for erecting the roof support structures had not been prepared and certifi ed by a professional engineer.

8.1 .2 Tenth Construction Company of Sinopec (TCC) did not take reasonably practi cable measures to protect the health and safety of the Electrical Consultant. The tank roof support structure that collapsed onto the worker was a skeleton structure. The erection procedures for erecting the roof support structures had not been prepared and certified by a Professional Engineer. The Electrical Consultant did not have a work permit as a temporary foreign worker and thus should not have been working at this work site.


8.2 Occupational Health and Safety Act, Section 3(3) Prime Contractor

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8.2. 1 CNRL did not do what was reasonable and practicable to ensure the Act and the regulations were complied with by failing to ensure that one of their contractors had erection drawings and procedures for a skeleton structure certified by a professional engrneer.

8.3 Occupational Health and Safety Regulation, Section 7(1) Availability of specifications

8.3. 1 The Occupational Health and Safety Code requires skeleton structures to be erected in accordance with engineered erection procedures. SSEC Canada did not provide engineered erection procedures. The procedures for the erection of the roof suppo1i structure were not certified by a professional engineer and the specifications were not readily available to the workers responsible for the work. The workers were given only verbal instructions on the erection procedure.

8.4 Occupational Health and Safety Regulation, Section 13(1)(a)(b) General protection of workers

8.4. 1 SSEC Canada did not ensure that the engineer who developed the erection drawings and procedures of the roof support structure was a professional engineer competent to do the work, or supervised by a professional engineer.

8.5 Occupational Health and Safety Code, Section 7(1) Hazard assessment

8.5.1 SSEC Canada held daily too lbox meetings before work started. Field level risk assessments were carried out during the toolbox meetings. SSEC Canada had prepared a HSE Manual containing generic safety procedures.

8.6 Occupational Health and Safety Code, Section 14(1) Certification by a professional engineer

8.6.1 The Code requires that skeleton structures are erected in accordance with erection procedures certified by a professional engineer. SSEC Canada did not ensure that the erection p rocedure and drawings had been certified, signed and stamped by a professional engineer.


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8.7 Occupational health and Safety Code, Section 46(3) Confined space training

8.7 .1 SSEC Canada did not ensure that the worker who was assigned duties relating to confined space entry was trained by a competent person. The worker who had been designated the Confined Space Monitor for the day of the incident was not aware of the purpose of the confined space designation, his duties in terms of maintaining communication w ith the workers in the confined space, or his duties if an emergency occurred. The Confined Space Monitor had not been effectively trained in his duties and was not competent to perfonn the duties required . The Confined Space Monitor was not able to communicate with the workers inside the tank and was not able to rai se an alarm following the incident.

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8.1 1.1

Occupational Health and Safety Code, Section 55(1) Confined space emergency response

SSEC Canada had an emergency response procedure. However, on the day of the incident the worker who had been designated as the Confined Space Monitor was not aware of the emergency response requirements and was not capable of raising an alarm or implementing an effective rescue. SSEC Canada did not ensure that the emergency response plan included procedures to evacuate the confined space immediately.

Occupational Health and Safety Code, Section 56(1) Confined space tending worker

The worker who had been designated as the Confined Space Monitor was not competent. SSEC Canada did not designate a competent worker to be in communication with the workers in the confined space.

Occupational Health and Safety Code, Section 56(2) Confined space tending worker

On the day of the incident the worker who was the Confined Space Monitor did not have a telephone or radio to summon assistance. SSEC Canada did not ensure that the designated worker had a suitable system for summoning assistance.

Occupational Health and Safety Code, Section 190(1) Skeleton structures

SSEC Canada did not ensure that erection drawing and procedures for the erection of the roof support structure in tank 72-TK- I B were prepared and certified by a professional engineer.


8. 12 Occupational Health and Safety Code, Section l90(2) Skeleton structures

File: F-536919

8.1 2. 1 The erection procedure prepared by SSEC Canada for the erection of the roof suppo1i stmcture in tank 72-TK-1 B did not ensure that the structure was stable during assembly.

8.13 Occupational Health and Safety Code, Section 300(1) Cable clips

8.13. 1 SSEC Canada did not ensure that u-bolt type clips used for fasteni ng wire rope were installed so that the u-bolt section of the clip bears on the dead side of the rope and the saddle of the clip bears on the live side of the rope.

8.1 4 Occupational Health and Safety Code, Section 306(1) Wire rope

8.14.1 SSEC Canada did not remove from service wire rope used to support the roof support structure in tank 72-TK- l B that had been distorted because of kinking where it had been attached around girders.

Section 9.0 FOLLOW-UP I ACTION TAKEN

9. 1 Alberta Employmen4 Immigration & Industry

9.1. I WHSC issued Stop Work Orders to CNRL for the construction of the east and west tank farms. WHSC issued orders for securing and dismantling the roof support structures in the east and west tank farm. Orders were issued for remedial actions to remove fa llen rnate1ial in tanks 1 A and 1 B. Orders were also issued for documentation, hazard assessments and for an investigation repoti.

9. 1.2 WHSC issued orders to SSEC Canada to provide documentation such as, worker information, worker training records, hazard assessment and engineering procedures. Orders were also issued to SSEC Canada to cooperate with CNRL's incident investigation.

9. 1.3 WHSC issued orders to TIW to provide the tank drawing specifications, assembly instructions, component testing and contact information with SSEC Canada.

9. 1.4 WHSC issued orders to ewfab Industries Ltd. to provide written observations from the disassembly of the roof support structure in tank 72-TK- 1 C.

17 September 27. 2007

File: F-5369 19

9.1.5 WHSC issued orders to SRS Industrial Services for written observations from the securing and the dismantling of the roof support structures in tanks 73-TK-1 1 and 73-TK-1 2.

9.2 Industry

9.2.1 At this time, CNRL has complied with all of the written orders with the exception of the order pertaining to the completion of an incident investigation report.

9.2.2 SSEC Canada complied with all of the orders written.

9.2.3 TIW complied with all of the orders written.

9.2.4 Newfab Industries Ltd. complied with all of the orders written.

9.2.5 SRS Industrial Services complied with all of the orders written.

9.3 Additional Measures

9.3 .1 o additional measures were required.

Section 10.0 SIGNATURES

Section 11.0 ATTACHMENTS

Attachment "A" Attachment "B" Attachment "C" Attachment "D"

.>"'"~ A7 6J.c:>o7 D e J

Se:P1e~eisi? 21- . k~. Date

~Z2Po7 Date ../

Photographs Location Map Site Layout Sketch of Roof Support Structure


Photograph #1

File: F-536919 Attachment "A"

Page 1of22

Shows the debris field on the east side of tank 72-TK lB after the collapse of the tank roof support structure.

Photograph #2


Page 2 of22

Shows part of the debris field on the outside of tank 72-TKlB after the collapse. Arrow "A" indicates the top of the welding machine where the Electrical Consultant was standing when he was struck by the collapsing steel. Arrow "B" indicates where the Electrical Consultant's body was found.

Photograph #3


Page 3 of22

Shows the interior of tank 72-TK-l B after the collapse of the roof support structure. This image was computer generated from several photographs. Arrows "A" indicate one of the vertical columns in the outer ring, and the base where it was standing before the collapse. Arrows "B" indicate one of the vertical columns in the inner ring and its base.


Page 4 of22

Photograph #4 Shows the interior of tank 72-TK-lB after the collapse of the roof support structure. Arrow "A" indicates the centre support column. Arrow "B" indicates the hard hat that was worn by the Scaffolder.

Photograph #5


Page 5 of22

Shows the interior of tank 72-TK-lB after the collapse of the roof support structure. Arrow "A" indicates the welding machine partially dislodged from the tank wall that the Electrical Consultant was standing on, and Welder 1 was working in, at the time of the incident. Arrow "B" indicates the welding machine that fell from the tank wall, that Welder 2 was working in.

Photograph #6


Page 6 of22

Shows a closeup view of the welding machine that Welder 2 was working in.

Photograph #7


Page 7 of22

Shows a closeup view of the welding machine that the Electrical Consultant was standing on, and that Welder 1 was working in.

Photograph #8


Page 8 of22

Shows part of the collapsed structure from tank 72-TK-lB, showing one of the % inch bolts that were used to bolt the components of the roof support structure together.


Page 9 of22

Photograph #9 Shows a sheared 14 inch bolt on the ground to the east of tank 72-TK-lB.


Page 10 of22

Photograph #10 Shows the bolt also shown in photograph 9. The markings on the bolt head indicating the specification of the bolt, A-307-B, can be seen.


Page 11 of22

Photograph #11 Shows the completed roof support structure in tank 72-TKlA, before it also collapsed. The roof structure that collapsed in tank 72-TK-lB was identical to this. Arrow indicates one of the support cables.


Page 12 of22

Photograph #12 Shows a closeup of one of the support cable top connections on tank 72-TK-1 A. Arrow "A" indicates where the support cable has been secured back onto itself using a screw pin shackle. Arrow "B" shows the top connection of one of the cables that had been used to support the vertical column during the erection of the roof support structure. This cable had not been removed after the assembly of the structure was completed.


Page 13 of22

Photograph #13 Shows the top connection of another support cable on tank 72-TK-lA. Arrow indicates where the cable is kinked as it passes over the top plate of the column.


Page 14of22

Photograph #14 Shows a beam from tank 72-TK-lB after the collapse of the roopf support structure. The top end of one of the support cables is still attached to the beam. Arrow indicates where the cable has been kinked and distorted as it passed through the shackle.


Page 15 of22

Photograph #15 Shows the partially completed roof structure in tank 72-TKl C. The cables used to support the vertical columns can be seen. The centre column and the inner ring of 6 columns have been erected, the beams have been installed joining the inner ring, and some of the radial purl ins have been installed.


Page 16 of22

Photograph #16 Shows the base of the centre column in tank 72-TK-lC. The "come-alongs" tensioning the cable supporting the columns can be seen. Arrow "A" indicates a cable that has been clamped correctly, with the saddle clamps installed so that the saddles are on the live side of the cable. Arrow "B" shows one that has been made up incorrectly, with the saddles on the dead side of the cable.


Page 17of22

Photograph #17 Shows tanks 73-TK-l land 73-TK-12 on the east tank farm. These tanks are smaller than the tanks on the west tank farm . The roof support structures consist of a centre colwnn and one ring of 6 columns. The roof support structure installation has been completed and the support cables can be seen.


Page 18of22

Photograph #18 Shows the debris field on the east side of tank 72-TK-lA after the roof support structure in this tank also collapsed.

--: ..... ,


Page 19 of22

Photograph #19 Shows the collapsed roof support structure on the east side of tank 72-TK-lA. It can be seen that several tank wall sections were broken off this tank during the collapse.


Page 20 of22

Photograph #20 Shows an intact orbital welding machine on the inside of a tank wall. A welder working inside the welding machine would be welding the horizontal seam indicated by the arrow.

k ,.


Page 21 of 22

Photograph #21 Shows an intact orbital welding machine seen from outside the tanlc The work platform on the top of the welding machine can be seen. The Electrical Consultant was standing on the top work platform of a similar welding machine at the time of the incident.


Page 22 of22

Photograph #22 Shows the lower end of one of the cables supporting the roof support structure in Tank 72-TK-lB after the collapse of the structure.

Jort McMa rraiiJ

File Number: F-536919 Attachment: "B" Location Map Not to Scale

N

• .. s

Sulphur Recovery:

Coker I Diluent Reco"ery

Cogeneratlon Plant and Utilities

N ¢ WestTank Farm

w s Ad min I Warehousing

\ To Aerodrome 5km

File Number: F-536919 Attachment: Site Layout Not to Scale

"C"

Camp3 Lodge

ast Tank Farm

Hydrogen Plant

Hydrotreatin g

Heat Integration

\Froth Treatment To South Mine

Mine Maintenance and Administration Facilities

--PllSlse 2 D Phase: D

~ - ..... -

GUY WIRES

1

OUTER RING

SUPPORT COLUMN

TANK SHELL

TANK SHELL

ELEVATION

INNER RING SUPPORT COLUMN

CENTRE SUPPORT COLUMN

GUY WIRES

F-536919 Attachment "D" Sketch of roof support structure Not to scale

OUTER RING GIRDERS

INNER RING

GIRDERS

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