Fast Track Railway Bridge Design & Construction in Remote Location – Lessons Learned in

Labrador

Christophe Deniaud, Ph.D., P.Eng.

Lead Railway Bridge Engineer, AECOM

17007-107 Avenue

Edmonton, Alberta, Canada

T5S 1G3

Tel: (780) 638-2185

Fax: (780) 486-7070

ABSTRACT

This mine extension project is located about 20 miles (32 kms) from the junction point to the existing

315 miles (500 kms) long QNSL railway which connects to a single port on the St Lawrence River. The

new track alignment includes 4 river crossings. The mine owner retained the services of a contractor to

start the planning and the detailed design of the new track alignment and the new railway bridges. This

contractor in turn retained the services of a couple of consultants to fulfill the design objectives. The

goal was to open the new line in the fall 2008, which did not materialize when the owner revisited

project justification due to the financial crisis that year. In March 2009, the mine owner retained directly

the consultants and contractors to re-start the project with revised and less stringent environment

constraints which lead to the complete re-design of all 4 bridge locations. By August 2009, the bridge

construction started and was completed in April 2010.

The challenges of this project included the fast track design of 4 new railway bridge structures with

precast segmental post-tensioned concrete single span in less than 8 months, the re-design of the 4

river crossings given the revised schedule and environmental constraints with precast concrete arch

and steel plate culverts, the procurement and transportation of the construction materials to the bridge

site with limited road access and the construction of the bridges from August 2009 and into the winter

months, with quality control issues in cold region areas.

This paper will review the conceptual railway bridge options, both detailed designs, and the

construction difficulties encountered during this fast track project. Finally, a series of lesson learned will

be presented to implement future successful fast track projects in remote areas.

INTRODUCTION

Project Description

This project was initiated in spring 2008 with the ambitious schedule of completion by the end of 2008.

The mine or the owner retained the services of a specialized rail construction contractor to manage the

project. This contractor then retained the services of two consulting firms to complete the design of the

drainage, track alignment and profile, the rail bridges, and the construction management. It also

investigated the services of a second contractor specialized in bridge construction and general grading

work for the sub-grade railway track beds. This project organization was later changed with the owner

retaining directly the services of all consultants, contractors and fabricators. The design parameters for

the railway in general terms were aimed at ensuring that trains hauling in excess of 26,500 tons (24,000

metric tonnes) of iron ore or approximately 33,100 tons (30,000 metric tonnes) equivalent gross tons

could operate safely and efficiently. Each car would carry no greater than 286,000 LBS (lading and

empty weight of car). Broadly speaking the railway would be designed to Cooper E-90 standards and

FRA/CTA Class track III standards.

This paper will focus on the structural bridge design aspect of the project only in relation with other

disciplines and change of project management and directions provided during this fast-track project.

However, the overall project included also the construction of a junction to the existing QNSL railway,

which was retained to move the goods from Wabush, Newfoundland Labrador to Sept-Iles, Quebec and

facilities in Sept-Iles for off loading the railcars and loading the material onto upcoming ships.

Site Description

The new mine is located near the Quebec and Labrador border about 16 miles (25 kms) southwest

from Labrador City. This city is only accessible through a single gravel road over 315 miles (500 kms)

long from Sept-Iles in Quebec, which is itself located about 500 miles (800 kms) northeast of the

closest major Canadian city centre, Quebec City. The track and roadway consists of about 20 miles (32

kms) of new single track bridge from the existing QNSL spur or industrial line which serves another

mine (i.e. Wabush). The track profile and alignment was optimized throughout the horizontal alignment

to limit the maximum grade to 1.7%. The track alignment crosses a total of 4 rivers or creeks which

require railway bridge structures. The river crossing widths were estimated to be 79 ft (24m), 98 ft

(30m), 79 ft (24m), and 138 ft (42m) at Virot, Walsh, Ironstone and Canning, respectively. The

proposed track alignment is located in Crown land which was entirely covered with bushes and trees. It

required to be purchased from the Government of Canada and Newfoundland and Labrador a right of

way from Wabush to the mine site. In other words, there was very limited access to the site and a

construction road was built to be used later as railway access road.

The soil conditions were a mix of sandy clay and gravel about 33 to 59ft (10 to 18m) deep over a

bedrock layer for all sites except Virot where the rock was found near the surface. Deep foundations

with HP piles were recommended with expected encounters with boulders and cobbles during driving.

The frost cover in this northern region is 10 ft (3.0m).

BRIDGE DESIGN OPTIONS

Initial Design or Design #1

The owner met with Navigable Water Protection Act (NWPA) representatives and the Department of

Fisheries and Ocean (DFO) in order to define the design criteria related to these bridge crossings.

These first meetings general consensus indicated that in order to meet the aggressive schedule, the

bridges would have to be designed with spans able to cross completely the high water width at each

location including any construction work. By doing so, no Environmental Assessment (EA)

consultations with the public were required and a short turn around response from the EA authorities

was anticipated. The high water mark in this remote part of the country was defined as the edge of the

growing grass. Table 1 presents the proposed high and low water marks for each location.

Table 1: High and Low Water Widths

Bridge Location Virot Walsh Ironstone Canning

Skew angle 25 deg 0 deg 30 deg 0 deg

Low water width 57 ft

(17.3 m) 84 ft

(25.5 m) 66 ft

(20.1 m) 82 ft

(25.0 m)

High water width 79 ft

(24.0 m) 97 ft

(29.5 m) 77 ft

(23.5 m) 137 ft

(41.8 m)

Steel Option

With span lengths up to 105ft (32m), Deck Plate Girder (DPG) type spans are typically not an issue for

the design or fabrication. However, at this remote location, the weight of each single girder was found

too much to be transported over 315 miles (500 kms) of gravel road. Safety and the integrity of the

main girder upon arrival to the site were a concern. In addition, the installation of the DPG girders would

have required one or two large hydraulic cranes which would have to be brought up from Quebec City

at a prohibitive cost for mobilisation and demobilisation.

At Canning with a crossing over 165 ft (50m) long the only reasonable steel option was a Deck Truss

(DT) span. Unfortunately, the design and fabrication time frame required for this span alone meant that

the proposed schedule could not be met.

Figures 1 and 2 show the proposed DPG and DT steel span options, respectively.

Precast Segmental Concrete Option

The bridge design looked at alternative options in order to meet the aggressive schedule and difficult

access. It was proposed to build precast segmental post-tensioned single spans. Figure 3 shows a

typical section of a single cell unit. These precast units had the advantage to be fabricated in a control

environment with a lighter weight for individual transport to the site. The erection required a smaller

crane to place the segments onto a construction truss. See Figure 4 for the schematic erection

procedure. The success of this design was dependant on a timely design, short fabrication schedule

and safe transportation of the segments to the site from the precast plant. In addition, the post-

tensioning operations of these spans were a critical task since it is temperature dependant. Such

operations can only be performed above +41F (+5C).

The overall bridge layout required short DPG approach spans in order to facilitate the post-tensioning

operations of the main concrete spans. For ease of design and fabrication cost savings it was decided

to provide two types of segmental spans 115 ft (35m) and 158 ft (48m), with the later length used at

Canning. Figure 5 shows a typical bridge crossing elevation.

Substructure Design

The substructure design presented its own challenges because the procurement of ready mix concrete

for large volume was not feasible given the existing facilities in Labrador City. The pile cap remained

cast-in-place but the pier and abutment shafts consisted of large precast units stacked on top of each

other with guiding and post-tensioned rods (see Figure 6). This was a concept developed successfully

for the Red River Flood protection project in Winnipeg where all major railway tracks crossing this river

were diverted and then raised in sequence with the use and re-use of modular piers and abutments.

Initial Design Synopsis

The design of the segmental option progressed rapidly and was completed in early fall 2008 after 16

weeks with a bridge design team of 6 structural engineers supported by over 7 draftsmen dedicated full

time to this project. The order to fabricate the segment was first delayed which meant missing the

window of opportunity to post-tensioned the tendons in 2008. Then, this purchase order never

materialized and by the end of 2008 the project was put on hold.

Final Design or Design #2

During the winter 2008-2009 the project was basically dormant until the owner re-started it by retaining

itself all the design consultants, contractors and fabricators. Also at this time, further meetings with EA

authorities and the owner revealed that Walsh and Canning crossings only required navigable

clearance 16 ft (5m) wide by 6.5ft (2m) tall above high water. Furthermore, the encroachment of the

construction activities in the wet area was not longer an issue as long as the navigable clearance was

provided upon completion of the structures.

These news requirements led to a complete review of the bridge crossing options. The proposed

structures would now consist of circular multi-plate steel culverts 26ft (8m) in diameter at Virot and

Ironstone (see Figure 7). For Walsh and Canning, precast concrete arches were selected to meet the

design requirements (see Figure 8). The arches were supported on cast-in-place pile caps similar to the

substructure pile cap design from the initial design.

In all 4 locations, MSE walls with precast concrete facings were selected for the approaches and over

the arches. The straps of each wall were placed alternatively as not to overlap to maintain the integrity

of each wall.

The design of these new 4 structures was completed in July 2009 in time for the in water construction

window.

CONSTRUCTION CHALLENGES

Access and remote location

Temporary Bridges

The river diversions and temporary bridge erection was the responsibility of the bridge contractor.

These were placed successfully during the fish window. However, delays in the construction of the final

structure meant that the EA permit for such diversions needed to be extended into the winter months.

The last temporary bridge was removed in March 2010. Figure 9 shows the temporary bridge with

diversion made of steel corrugated culvert at Ironstone, which is typical of all locations.

QA/QC

Labrador City does not possess laboratory testing facilities to validate the concrete strength. A third

party consultant was retained to collect concrete cylinders which were placed on a plane bound to St-

John’s for testing. Luckily, the concrete strength test cylinders showed that the concrete met the

specifications except for one pier cap. This particular cap strength was further investigated with coring

samples taken from the zone of so called poor concrete. These additional tests showed that the

concrete strength was acceptable as per CSA23.2.

Procurement of materials

Given the remote location of the project, all the material had to be ordered from major centres of the

country and transported to the site mainly by trucks. To this effect, the design of the bridge was

optimized to be of a modular system as much as possible in order to facilitate the transportation of

small bridge components.

The precast BEBO® arches were cast in two different plants (i.e. Nova-Scotia and Quebec) to meet the

schedule of delivery. All these segments were shipped individually by truck and inspected by the

manufacturer upon destination for any defects. Note the middle arch at Canning used the E84T7

segments which were used for the first time in North America. The actual forms were first shipped from

Europe to the casting plant.

The design also called for 20% more piles to be purchased to account for the potentiality of boulder

encounters and brought to site to be used if necessary. This premium cost of supply and delivery for

additional material was found beneficial compared to the alternative of running short of piles. Such

event would have effectively shut down the bridge site construction until the arrival of new materials

and delay the bridge construction which ran continuously to minimize the effect of the cold weather.

Similar actions were taken for the procurement of the steel reinforcements to be placed in the cast-in-

place pile caps. Additional steel rebars were purchased and delivered to the site for any unexpected

construction changes.

Existing Soil Conditions

The geotechncial investigations revealed that the layer of soil above the bed rock presented a

significant amount of boulders and cobbles to be encountered while driving the piles for the deep

foundations. At Virot, the bed rock was anticipated to be at very shallow depth below the existing

ground.

The construction of the piers was carried out with the installation of cofferdams made of sheet piles

driven just below the underside of the bottom excavation as shown in Figure 10. These sheet piles are

then held by interior wall piles driven to the bedrock. The cofferdam sheet piles allowed a dry base for

the placement the insulation and formwork for concreting of the pile caps. These sheet piles were left in

place and cut flush with the top concrete.

In a few instances, the piles hit some boulders and the remedial work consisted of using dynamite to

remove the obstruction. A dynamite crew was on site for a large cut along the track alignment and was

found very useful in removing large boulders in order to allow the completion of the pile installation.

At Ironstone, the bedrock happened to be much higher than anticipated and a program of rock

dynamite was used to remove the excess layer of rock and to allow the installation of the steel plate

culvert (see Figure 11).

Extreme cold weather conditions

Placement of non-frozen material

The cast in place was poured in cold conditions but not extreme cold conditions in the fall of 2009.

Standard heating and insulation procedures were used to keep the concrete from freezing after

placement during the curing process. Heating around pier cap was also provided when the grout was

placed under the BEBO® arches (see Figure 12). Hot water was provided in the design mix in order to

ensure the delivery of the concrete at the specified temperature.

A crushing plant was built to provide ballast material and sub-ballast material for the track construction.

The “residue” or left over from the ballast production operations was tested and found suitable as

backfill material for the bridges. This material contains little moisture and fine material which made it

easier to place in cold conditions and yet meet the compaction tests. The backfill materials were placed

in layers of 300mm maximum, compacted and tested before proceeding with the next layer. In a few

circumstances where the compaction test failed, a heating tarp was placed overnight and after re-

compaction of the backfill material in the morning, it passed the compaction tests allowing the process

to continue.

Incorrect insulation material

The design of the piers included under each pier cap the placement of a compressible inclusion

material, which has the characteristic of collapsing under frost heave. This property meant that is was

possible to reduce the buried depth of the underside pile caps to 5ft (1.5m) in lieu of 10ft (3m) frost

cover, which would have required a much deeper cofferdam installation and excavation. The drawings

called for a minimum thickness of 10in (250mm) recommended by the geotechnical engineer but the

final design of this material was to be performed by the supplier. The contractor went unfortunately

ahead with the purchase and the installation of an incorrect material without prior design validation by

the manufacturer. This material was paramount to the design of the cap and without manufacturer

design validation; the two bridges concerned (i.e. Walsh and Canning) were in jeopardy.

This serious defect had the potential to seriously impede the permit application for railway operations

because the construction conformance with the design could not be obtained. After numerous

conference calls with the manufacturer, the design team and the owner, a compromised alternative was

found by a simple but yet cumbersome solution which involved a monitoring program over several

years of the pier cap with survey points and frost penetration monitoring devices. In other words, the

owner ended up with a stringent maintenance program for two new structures.

LESSON LEARNED

Planning

This project was initiated in spring 2008 with an aggressive schedule which led to the best suitable

feasible design available at that time given the stringent environmental constraints provided.

Unfortunately or fortunately, these initial environmental requirements were reviewed to less stringent or

more realistic constraints. With such changes in the design constraints, it became then evident that

cheaper bridge options should be built. Fast-tracking environmental approval is a difficult task. With

most regulatory agencies, sufficient time should be allocated to discuss options and hence to avoid

placing the design team with very stringent constraints as a compensation for fast approval.

In addition, the owner revisited its priority and commitment to the project with alternative transportation

options, which were found later not feasible. These changes of directions half way through the project

led to re-design of the bridges and loss of valuable summer construction periods. The amount of winter

construction with its excessive costs could have been possibly avoided or significantly reduced, which

would have also helped the final product quality.

Communication

With fast track projects, the amount of information received is condensed and often difficult to absorb.

Errors or misinterpretation are almost inevitable and it is paramount for all stakeholders in a fast track

project to communicate efficiently and effectively to report any potential upcoming issues without

delays. Several of the issues encountered in this project could have been in most case avoided should

all the personal be more pro-active in communicating their concerns.

Contracts

This project required the mobilisation of a large number of consultants, construction crews and other

support staffing to fulfill the design and construction schedule. The description of roles and

responsibilities of each stakeholder was ambiguous, changing and was later never completely

disclosed to all parties since the owner retained each consultant and construction company with

individual contracts. This situation created a lot of friction and resistance within the project team which

is very counter-productive and inefficient in a fast-track environment. It made it difficult for the managing

consultant to lead the design and to implement a quality control program for compliance when the

details of the contract roles and responsibilities are not disclosed. Several construction issues could

have been avoided with a clear understanding of each participant expectations, which would have

created a team effort rather than narrow minded and tunnel thinking players.

POST BRIDGE CONSTRUCTION ACTIVITIES

The survey points at each pier pile caps are in place and linked to a fixed survey monument within the

vicinity of both bridge sites. In addition, frost penetration measuring devices have been installed near

the piers. Both apparatus will be recorded on a regular basis for the next 7 years as part of the

maintenance program and mitigation process elaborated to respond to the placement of the improper

insulation material under the pier caps.

The new tracks are nearly completed for the whole alignment up to the junction with the existing QNSL

industrial line. Negotiations are still ongoing with the neighbouring mines. The other end of the overall

project includes a storage area at Sept-Iles for loading onto ships. The construction of this off-loading

from railcars and loading onto ships facilities is another key element of the project which was not

started yet at the time this paper was submitted.

CONCLUSION

A successful fast-track project in remote area can be achieved with these basic rules:

1. Good planning of the overall project with realistic dates, deadlines and milestone decision dates

to allow the identification of the critical path, which might not be the bridge construction.

2. Good contract with clear definition of roles and responsibilities of all parties, which are also

accountable for their parts and expected to work as team.

3. Excellent communication between all stakeholder involved in order to be pro-active in dealing

with construction situations which are bound to arise on a fast track project

Figure 1: DPG span option at Walsh

Figure 2: Deck Truss (DT) option at Canning

Canning Walsh, Ironstone & Virot

Figure 3: Typical section of a single cell precast segmental span option

Figure 4: Schematic construction procedure for segmental concrete span option

Figure 5: Precast segmental concrete option elevation at Ironstone

Figure 6: Modular precast substructure elements

Figure 7: Completed multi-plate culverts at Virot

Figure 8: Completed BEBO® arches at Canning

Figure 9: Temporary bridge and channel diversion at Ironstone during construction

Figure 10: Typical cofferdam and pier piles miss-alignment at Canning

Figure 11: Rock removal at Virot with dynamite

Figure 12: Heating and insulation for grout placement