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Canada's “Rock to Road” Magazine
August/September
2006 Issue
For a copy of the issue
that contains these articles with colour photos, click
here.
B.C.’s
Sea-to-Sky Highway targets innovation, value
By Andy Bateman, Engineering
Editor
The
Sea-to-Sky Highway is one of Canada’s outstanding roadbuilding
projects and combines innovative engineering solutions with a new method
of project delivery.
The highway upgrade currently underway between West Vancouver and Whistler
focuses on saving lives and improving mobility by providing increased
opportunities to pass slow moving vehicles. Improvements to the twisting
100 km long mountain highway include widening, straightening, improved
sightlines, additional passing lanes and wider shoulders, as well as
measures to contain storm water and rock fall debris. The $600 million
project is scheduled for completion by spring 2009, in readiness for
Whistler’s hosting of the 2010 Winter Olympics. By then, highway
improvements will result in 30 per cent fewer accidents and a 15-minute
reduction in overall travel time between Horseshoe Bay and Whistler.
Beyond 2010, the improvements are expected to meet population growth
and travel demands until 2020, with further improvements phased in as
required over approximately 20 years. The project will create 6,000
new jobs throughout the province as a result of economic activity generated
along the corridor, and will increase provincial GDP by $300 million
over the period of 2010 to 2025.
It has long been recognised that
improvements were needed to the highway’s safety, reliability
and capacity, with its poor safety record underscored by 300 annual
accidents. According to one recent report, the collision rate for a
specific section, Snake Hill, is 1.28 collisions per million vehicle
kilometres (MVKm), or more than double the 0.535 per MVKm average collision
rate for a comparable rural conventional highway. In turn, road reliability
has been reduced by delays or closures caused by these accidents and
other unforeseen incidents such as rock slides. The need for increased
capacity is confirmed by forecasted growth in both traffic volume and
population. Average Annual Daily Traffic (AADT) volumes between Horseshoe
Bay and Squamish are forecast to increase 62 per cent from 13,700 to
22,000 by 2025, while volumes between Squamish and Whistler are forecast
to increase 56 per cent from 7,700 to 12,000 over the same period. Official
community plans along the corridor indicate a 94 per cent growth in
population over the next 25 years.
David Wallace is project engineering manager
for project design/build contractor Peter Kiewit Sons Co. Wallace explains
that, apart from newly completed sections, the existing two lane road
was constructed in 1957 and 1958. Since then, several asphalt overlays
have been added and considerable sums spent on rock fall prevention.
These efforts aside, limited reconstruction options have been available
given the road’s tight geometry, cost and inevitable traffic delays.
Before the current project could even
begin, some fundamental decisions would have to be made about the method
of widening the existing pavement. At any given location, would it be
preferable to widen on the upslope or the downslope side? Widening on
the upslope side would frequently require drilling and blasting, while
widening on the down slope would require fill or the construction of
a retaining wall. Add to that dilemma, the requirement for significant
environmental protection as well as the protection of an existing CN
railway line on the downslope side. To tackle these issues, a team of
eight specialists walked the whole length of the contract and see at
first hand some of the challenges involved. This feasibility phase was
a significant undertaking in itself, with the team incurring six figure
costs and taking some three weeks to complete the 100 km walk. Early
route studies contemplated a highway with a 100 km/h speed limit but
it soon became clear that these options would be prohibitively expensive,
as would tunnel options more recently considered. Other routes were
ruled out as some of these would adversely impact Vancouver’s
principal water sources.
Design
The new design will be incorporate two,
three or four-lane highway with an 80 km/h speed limit except in urban
areas. Specifically, there will be four lanes from Horseshoe Bay to
Lions Bay, two, three and four lanes from Lions Bay to Porteau Cove,
four lanes from Porteau Cove to Squamish, four lanes within urban Squamish
and three lanes from Squamish to Whistler. The overall location and
scheduling of the improvement work is a function of property acquisition,
with most project work concentrated at the southern end for the time
being. In all, about 65 km of road will be rebuilt. On rural four lane
sections, the addition of two lanes more than doubles the typical existing
pavement width from about 12 m to 24 m plus the width of any required
fill or walls. There are 48 bridges on the project, 24 of which are
located in the project’s southern DB4 section. Wallace notes that
design of the structures is driven by earthquake resistance rather than
projected traffic volumes or severe weather, while the light pavement
cross section similarly reflects a projected low ratio of trucks and
relatively mild weather. A typical cross section consists of rock fill,
150 mm of 0-75 mm base material followed by 150 mm of 0-25 mm road base.
On top of the base materials, hot mix asphalt lifts consist of 50 mm
base course and 75 mm Superpave surface lifts.
Design innovations abound on the project.
At a number of locations, retention areas are being constructed to mitigate
the impact of debris torrents that have, in extreme cases, washed away
bridges or whole sections of highway. These torrents occur when storm
water carrying sand and gravel pours down the mountainside and temporarily
overwhelms the carrying capacity of existing creek beds. The retention
areas are significant structures in their own right, with one such area
at Sunset Beach providing 6000 m3 of retention.
Still on the topic of retention, Mechanically
Stabilized Earth (MSE) retaining walls are widely used to construct
wing walls and creek walls. Highly visible walls are faced with precast
stamped face panels, while an interlocking wire mesh facing is used
where the walls are less visible. At first glance, the latter looks
like conventional gabion baskets, but actually utilises interlocking
layered sections to provide stable and cost effective retention.
Another example of cost effect design
solutions is provided by the bridge abutments at the Furry Creek bridge.
Here, the piles underneath the bridge abutments have been extended to
the cap supporting the bridge girders, with the space between the piles
filled with concrete to form the abutments themselves.
Environmental measures
The Furry Creek Bridge also provides a
practical example of the extent of project’s comprehensive environmental
protection measures. In this case, the bridge deck comprises precast
concrete panels rather than poured-in-place deck panels to eliminate
the risk of spilling concrete into the creek during a deck pour. For
the contractor, the precast approach has the added benefit of reducing
soffit formwork.
In addition to being subject to all applicable
provincial and federal environmental requirements, the owner has issued
a table of commitments for the whole project, dealing with topics such
as air quality, water quality and animal habitat to name just a few.
Before many construction activities can begin, environmental management
plans have to be drawn up, reviewed and approved. There is still a further
step in the process in which the contractor has to develop a work plan
incorporating the approved environmental management plans.
Materials and construction
Job demand for aggregates totals about
3 million tonnes of aggregates, including concrete coarse and fine aggregates,
asphalt coarse and fine aggregates, 0-25 mm and 0-75 mm road base aggregates,
MSE wall backfill (0-150 mm for backfill and 100 to 200 mm for facing
rock) together with drainage rock for culverts and drainpipes. Hot
mix asphalt quantities include some 450 000 tonnes of Class B and Class
A open graded Superpave asphalt. All rock fill material is site sourced,
with road design targeting a zero cut and fill balance to avoid the
truck traffic generated by importing or exporting fill material. Within
the project limits, about 2.4 million m3 of fill material will be moved
to achieve the necessary improvements in width and vertical alignment.
To minimise traffic delays during construction,
contract rules stipulate that road closures for blasting are limited
to just 20 minutes. This tight time frame includes pre blast set up,
the blast itself, post blast checks and any debris removal, even though
some rock faces are next to the road edge. In practice, the time left
for road clearance is only a few minutes, so average blasts are kept
small (600 m3 – 700 m3) and designed to minimise the spread of
shot rock.
Project delivery
The Sea-to-Sky project is British Columbia’s
first P3 project (public private partnership) using the relatively new
Design Build Finance Operate (DBFO) model as its method of project delivery.
Under this delivery method, the province, as owner, defines baseline
requirements and sets the project budget, while the private sector is
responsible for design, financing and long-term operations and maintenance.
Having defined the maximum performance payments it would pay over the
life of the contract, the province required proponents to develop their
proposals on the basis of meeting the baseline requirements, together
with additional improvements that could be achieved within the maximum
payment.
The successful private sector partner
on the Sea-to-Sky project is the S2S Transportation Group, whose members
and respective roles are: Macquarie North America Limited, Finance;
Peter Kiewit Sons Co, Design/Build; BA Blacktop, Construction; Hatch
Mott MacDonald, Design; Miller Paving, Operations, maintenance, rehabilitation
and Capilano Highway Services, Operations and maintenance. The S2S Transportation
Group will construct highway improvements and maintain the system, as
well as assuming most of the construction, maintenance and operation
risks. For Kiewit, the project requires significant human resources
including some 170 staff and 300 hourly employees. Some 90 designers
and specialists from other companies are also involved in addition to
some 80 government employees.
According to B.C. government information,
S2S was selected to provide the best value highway improvements through
a competitive selection process and a rigorous evaluation of proposals.
Within the project budget, the private sector contractor is able to
provide significant added value to what could have been built by the
Ministry of Transportation under traditional procurement. Examples of
added value received by partnering with the private sector include a
33 per cent increase in additional passing lanes from 60 km to 80 km,
an 80 per cent increase in median barrier from 20 km to 36 km, as well
as, improvements to rock fall and debris catchment, highway straightening,
lighting, roadside reflectors and earthquake resistance. During construction,
intelligent traffic management systems should result in up to 50 per
cent fewer delays and closures.
Equipment
Some idea of the work involved in the
project is given by Kiewit’s formidable site equipment list. The
extensive list runs to eight pages, with at least 350 items and including
some $40 million worth of new equipment.
Major pieces of mobile equipment include
six Caterpillar dozers (D3C, two D6R XLs, two D8Ts and D9R DS), a Caterpillar
426B and two John Deere 710Gs backhoe/loaders, two Caterpillar graders
(14G and 14H), 13 Caterpillar excavators (225CL, 320B, 330B, three 450C
LCs, four 330CLs, 330C LC, 365CL and 385CL), a John Deere135C RTS excavator,
a Komatsu PC1250LC-7 excavator, two Ingersoll-Rand SD150D compactors,
five Caterpillar compactors (CP323C, CP563D, CS323C, CS563E, CS583E),
a Dynapac CA151D compactor, a Link-Belt HC-218 and three Grove (RT-745
RT-750, TTS870B) mobile cranes, nine articulated trucks (five Volvo
A35Ds and Caterpillar 730s), four Caterpillar 769D rigid frame haulers,
an Ingersoll-Rand ECM -350 air track drill, 10 Tamrock drills (two 550
Tiger drills and eight Ranger 800 drills), three Ford 8000 tankers,
eight Kenworth tri-drive trucks, five Freightliner International 7400
SBA trucks, six tridem pony trailers and at least 100 Ford light trucks,
SUV’s and cars.
In addition, the rental equipment list
includes nine John Deere excavators (135, 200, 225, 330 and 450 models),
three Komatsu excavators (PC200, PC-78 MR6 and PC300LL), as well as
nine articulated trucks including a Komatsu HM300, two Caterpillar 735s
and six Volvo A30s.
There are also a number of portable material
plants dedicated to the job. Three dry batch concrete plants include
Erie Strayer, Ross and CON-E-CO models, while there is also a large
asphalt aggregate crusher set up at the government’s Raynier quarry,
a smaller road base crusher at Garibaldi, a Pioneer tracked jaw, and
a subcontractor’s plant washing concrete aggregates. The
Raynier quarry is also home to an asphalt plant set up by BA Blacktop.
As a footnote, Wallace adds that significant
investment has been made in an advanced communications system for the
project, including some $500,000 in wireless infrastructure plus another
$300,000 to $400,000 in radios. The system links all four of the project’s
semi-autonomous areas as well as the company’s Vancouver head
office with high speed internet as well as telephone and radio. As a
result, all essential information on job progress and operations can
be reported and accessed as required.
Back to
top
B.C.
quarry redevelopment plan creates long term benefits, short term challenges
By Andy Bateman,
Engineering Editor
The
Cox Station granite quarry is located alongside the Fraser River at
Sumas Mountain some 70 km east of Vancouver. It is the principal operation
of Mainland Sand & Gravel Ltd., which ranked 14th in Aggregates
& Roadbuilding’s latest Top 25 Aggregate Operations report
with production of 2.0 million tonnes. The operation is unusual insofar
as product can be shipped by either truck, rail or barge. In practice,
90 - 95 per cent of its products are shipped in 1600 to 4000-tonne capacity
barges to Vancouver, with some going as far as Vancouver Island.The
quarry’s full product range includes dry asphalt and road base
aggregates as well as washed concrete aggregates, rail ballast and rip
rap.
Construction manager Brian Weeks explains
that, until recently, all rock was extracted from the operation’s
west quarry and processed in nearby fixed plants. From there, finished
product was trucked to the barge loading dock at the east end of the
property. However, reserves in the west quarry are nearing depletion,
so extraction is being progressively transferred to the new east quarry
where there are about 100 years of quality granite reserves. The development
plan also takes advantage of the switch to install a new processing
plant within the east quarry and increase production capacity from 800
tonnes/h to 1500 tonnes/h. Ultimately, the entire process of extraction,
processing, and barge loading will be completed in a relatively compact
area when compared to the operation’s present footprint. The resulting
improved operational efficiencies will include a short primary haul
in the east quarry, economies of scale and the elimination of a long
internal finished product truck haul.
To implement the overall plan, the operation
has to go through a challenging transitional phase lasting some three
to four years which includes full development of the east quarry face
as well as the design and installation of the new east quarry processing
plant. As Weeks points out, all these changes have to be made while
maintaining full production: “Customer demand is very strong and
looks set to remain that way for at least the next few years. As a result,
we don’t have the luxury of any significant breaks in production
to commission new plant or the opportunity to build up inventory of
key products.”
New
quarry development
When Aggregates & Roadbuilding recently
visited the operation, the east quarry face was still in its early stages
of development. The plan is to develop a haul road with a grade of no
steeper than 10 per cent up the entire face, allowing large trucks to
work concurrently with the installation of a new primary crusher. For
the short term at least, primary production costs are high as shot rock
is being handled three times, or as Weeks succinctly puts it; “We
are moving 6 million tonnes of rock to produce 2 million tonnes.”
With no access from the back or sides, the steep face has to be developed
from the front and most of its upper section was accessible at the time
only by tracked vehicles or articulated dump trucks (ADT’s) via
a steep and narrow track. About half way down the face, a small intermediate
bench was also accessible to wheel loaders, while a bench near the bottom
was accessible to all equipment including full size quarry haul trucks.
Small development faces were being drilled and blasted near the top
of the face, with the resulting shot rock loaded and hauled to a high
level casting out point. Cast out material accumulated on the intermediate
bench below, from where it was cast out again to the bottom bench.
For safety reasons, the second casting
was carried out only on afternoon shifts when no one was working below.
In the third and final face development step, the shot rock was recovered
from the bottom bench and hauled to the existing processing plant. Equipment
being used in the face development process included a rental Caterpillar
D8N dozer and a 4.6 m3 Hitachi 1100 excavator for the high level casting
out, while the company’s 6.7 m3 Komatsu WA600, 6.6 m3 Caterpillar
988H or 9.9 m3 Caterpillar 992 wheel loaders completed the intermediate
level casting out. The relatively long haul from the bottom bench to
the existing primary crusher was being completed by three 60-tonne capacity
Caterpillar 775D haul trucks. As soon as face development has progressed
sufficiently, a recently acquired 54-74 Allis-Chalmers primary gyratory
crusher will be installed above grade in the east quarry. With an overall
face height of nearly 230 m, primary haul trucks will nonetheless have
a short downhill haul for many years as the upper benches will be higher
than the 21 m dump elevation of the crusher. Weeks adds that the planned
east quarry secondary plant will use two Metso HP 400 cone crushers
and two 45.7 m long Superior TeleStackers recovered from the existing
plant, while almost everything else will be new.
Existing
processing plant
At the existing dry processing plant,
shot rock is reduced to 180 mm minus by a 30-65 gyratory primary crusher
and conveyed to a surge pile. Material recovered from the surge pile
is first screened by a Simplicity 7x20 double deck screen at the secondary
plant with oversize material directed to a Metso Nordberg 1560A Omnicone
crusher. Product from the Omnicone 1560A provides feed for the second
screen, a Simplicity 7x20 double deck unit, with material passing the
bottom deck of both screens stockpiled as granular road base. At the
same time, the 38 mm x 11 mm middle fraction off the secondary screen
is conveyed to a tertiary circuit where a Simplicity 8x20 triple deck
screen separates three asphalt aggregates sizes; 25 mm clear, 13 mm
clear and 8 mm minus. Material larger than 25 mm is directed to a Metso
HP 400 tertiary crusher set up in closed circuit with the screen to
meet crushed face specifications for asphalt aggregates.
The operation’s separate wash plant
produces between 200 000 and 300 000 tonnes annually, utilising either
pit run or 19 mm road base as its feed material. Material larger than
125 mm in the pit run is separated by a grizzly screen while a 5x14
scalping screen downstream of the grizzly separates material larger
than 25 mm from wash plant feed. The 12 mm to 25 mm plant feed first
passes through a Trio 914 mm coarse material washer before being conveyed
to a Simplicity 8x20 triple deck wash screen. Fitted throughout with
urethane screen media, this wash screen separates 25mm x 14 mm, 14 mm
x 9 mm, and 9 mm x 3 mm “bird’s eye” stone sizes.
Minus 3 mm material passing though the screen’s bottom deck is
transferred to an Eagle Iron Works (EIW) classifier producing specification
concrete sand and secondary sand. Sand product from the classifier is
dewatered by Trio 914 mm and EIW 1067 mm dewatering screws before being
stockpiled. The wash plant does not have its own operator. Instead,
key operating functions such as feeder belt speed, sequenced start and
stop and emergency stop are controlled by radio remote control from
the loader providing raw feed.
New
load out conveyor
Although near the end of the internal
process chain, the new load out conveyor connecting the east quarry
and the dock is one of the first major elements of the redevelopment
plan to be commissioned. Weeks explains why: “We decided to prioritise
the load out conveyor as it shortens the product truck haul from the
existing plant in the short term and will eliminate the haul entirely
from the planned east quarry plant. In both cases, it eliminates a time
consuming and potentially dangerous at grade railroad crossing on the
finished product haul. There were some 250,000 crossings each year,
with trucks delayed frequently by trains passing though the operation
on the CN main line.”
To feed the new system, Mainland installed
a 24.5 m3 Mormak truck dump hopper with a 1067 mm x 9.1 m conveyor which
can handle loads from either tandem trucks or the 40 tonne articulated
trucks. Rated at 2250 tonnes/h, the over railroad load out conveyor
has a 1219 mm wide belt and is 366 m long. Driven by a 200hp motor,
it discharges onto a 1219 mm x 30.5 m Western Engineered Systems radial
stacker. This stacker can be positioned to discharge directly into the
former truck dump feed hopper of the barge loading conveyor or swung
round to stockpile material close to the river. There are three reasons
why this indirect loading approach is being used. Firstly, having product
stockpiled near the river facilitates product changes or top ups during
barge loading. Secondly, the radial stacker allows excess material on
the load out conveyor to be stockpiled should a barge reach capacity
before the belt is empty. (A similar scenario could also occur if a
product switch on the barge is required). Finally, should the load out
conveyor fail for any reason, it will be easy to revert to the existing
truck haul method and avoid delays in product shipment. Power for the
load out conveyor is provided by the recent installation of a 1.2 km
long power line from the existing tertiary crusher. In due course, a
tap off the same line will provide power for the new east quarry processing
plant, starting with the primary crusher. After that, the installation
and commissioning of additional process stages in the east quarry will
mark successful implementation of the redevelopment plan.
Mainland Sand & Gravel Limited is
family owned business, formed in 1971 and based in Surrey, B.C.
Back to
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New
loaders do double duty
An
Ontario crushing contractor is utilising a quick attachment and in-house
engineered boom design to convert wheel loaders into an effective lifting
device.
Crushing
contractor J.G. Stewart Construction Ltd. operates eight portable aggregate
plants across Ontario and the ability to set up, move and tear down
a crushing spread efficiently is vital for a successful business. After
several years of research and internal development, Stewart has developed
a safe and effective system to assist with plant moves. The system utilises
a quick attachment and lifting boom mounted on an otherwise stock wheel
loader to lift or tow equipment into position. Today, several of the
company’s wheel loaders are fitted with the quick attachments
and eleven lifting booms are in regular use.
Company president John Stewart explains
that an internal review some years ago identified the process of lifting
and moving of portable aggregate processing equipment as a potential
safety hazard. A typical spread will include portable conveyors, trailer-mounted
crushers, screens and a generator set in addition to a wheel loader
on material handling duty. While on site, the process equipment may
be moved several times to keep the production spread near the active
face and so minimise load and carry distances for the loader. The question
is; how are these components to be moved safely and effectively? Some
can be towed, but others require a substantial lifting device. Mobile
cranes are a possibility, but would be expensive to keep on standby
and not well suited to loaded travel across an uneven quarry or pit
floor. Stewart’s team wondered if would be possible to utilise
the loader by the addition of a lifting boom. Most of the time, the
loader would be on its normal duty of hauling shot rock or pit run to
the primary crusher. When the loader was required for lifting or towing,
its bucket could quickly be removed and replaced by the boom. For this
idea to work, a boom would have to be purpose built for the task and
the process of changing from bucket to boom and back again would have
to be both safe and fast.
Against this background, Stewart went
in search for a quick attachment that would facilitate the switch between
bucket and lifting boom. Although none were commercially available at
the time, Stewart located a quick attachment in service with the U.S.
army and bought the first unit in 2001. Since then, a number of improvements
have been made to the original design to provide the best fit with the
loader buckets and lifting booms currently in service.
The boom itself has been designed and
engineered in-house and has a rated capacity of up to 15 tonnes. The
loader operator can see the attachment points of the extendable boom
from the loader cab and, more important, its design also gives the loader
operator a clear view of the plant operator when lifting chains are
being attached. The versatile boom is also equipped with a tow hitch
to move items such as field conveyors, as well as a tow point for full
size trailers. Apart from annual testing for certification, it requires
little maintenance.
Turning to the loaders themselves, Stewart’s
unique system is in service with two of the four new Volvo L33E wheel
loaders that the company acquired earlier this year. Duty for all four
machines will be primary load and haul in granite, limestone or sand
and gravel applications. The two loaders fitted with quick attachments
carry 6.73 m3 buckets which can be replaced by the boom in a few minutes.
The lifting system on these loaders is balanced, such that no adjustments
are required to the loader counterweights when either the bucket or
boom is fitted. The other two new machines are fitted with conventional
7.5 m3 buckets.
When it came to buying the loaders, Stewart
emphasises that the commitment of over $2.6 million is significant for
a company of this size. The purchase was carefully thought out and included
comparison of the L330E with competitive units in a real life application.
On a 122 m primary haul, it was found that the L330E delivered significant
fuel savings, a faster load cycle and good operator comfort compared
to the competition. The new loaders are well equipped, with back up
cameras, proximity sensors, a Trabon automatic greasing system and comfort
features such as the HEPA cab air filter. These are also the first loaders
bought by Stewart equipped with Ride Control to reduce spillage in a
load and carry application. Michelin X Mine D2’s were the tires
of choice.
The L330E’s manufacturer claims
better fuel efficiency than most other machines in its class in most
applications. Fuel saving measures includes a 503 hp engine that delivers
full power even at low revolutions per minute (rpm). To further improve
fuel economy, a load sensing hydraulic system provides flow and pressure
only when required, while the load sensing hydrostatic steering system
is activated only when the wheel is turned.
Four companies are owned by John, Greg,
Glen and Ken Stewart, sons of the late Russell H. Stewart. The individually
owned companies include J.G. Stewart Construction Ltd., R.H. Stewart
Construction Co. Inc. and G.H. Stewart Construction Ltd., all based
in Orillia, Ont. and Stewart Construction Alberta Ltd., based in Innisfail.
Back
to top
Aecon
fast tracks 407 ETR widening
Aecon
Construction & Materials is taking just five months to complete
nearly $40 million worth of road widening work on the 407 ETR north
of Toronto.
Traffic
volumes on the 407 ETR have increased steadily since the 1997 opening
of the first 36km section, with 330,000 drivers now using the open access
toll road every day in peak months, including a one day peak of 413,687
trips on June 30, 2005.
To help deal with these increased volumes, the
number of through lanes is being increased from three to five (in each
direction) on the busy 22 km section between Highways 427 and 404, taking
the 407 up to its reported maximum capability. For contractor Aecon
Construction & Materials, the combined pressures of a tight project
completion deadline, liquidated damages of $20,000 per day and an awkward
median construction zone location have required virtually continuous
site operations and creative solutions to project challenges.
Brian Morris, senior contracts manager for Aecon
Construction & Materials explains that work began in mid-April 2006,
with the eastbound lanes and westbound lanes scheduled for completion
by September 6th and 11th respectively. The project actually encompasses
three design contracts designated C4, C5, and C6-2006 and was negotiated
directly between the Aecon and the owner. All road widening is carried
out in the median and begins with topsoil excavation followed by earth
fill placement, compaction and sub drain installation. The pavement
section itself consists of 200 mm of Granular A base, 100 mm of Open
Graded Drainage Layer (OGDL) hot mix asphalt and a 280 mm concrete surface
lift. Dufferin Construction Ltd. is completing the concrete paving as
principal subcontractor to Aecon.
Once the job is complete, just one additional
lane will be initially opened in each direction, with two median lanes
remaining closed to facilitate the installation of a final median concrete
barrier wall and sewers. Morris adds that a structures contract designated
C4-2005 was already in place within the project limits and includes
the widening of three bridges carrying the 407 ETR over Rainbow Creek,
the Humber River and Highway 400. In all, some $46 million worth of
work is being completed.
The median location of the road widening construction zone has necessitated
some specific safety and construction traffic control measures. Access
to the construction zone (both ingress and egress) is generally only
allowed from the opposite side of the lanes under construction, thereby
providing maximum separation distance between work crews and access
points to live traffic. Site access on the same side as active construction
is generally prohibited. In early June, for instance, the construction
areas on the eastbound side were separated from eastbound highway traffic
by a 22 km long solid temporary concrete barrier (TCB) with ingress
from the westbound lanes only.
To obtain site access, any construction
traffic on the 407 eastbound had to leave the highway at the next exit
after the construction zone, turn round, join 407 westbound and enter
the construction zone from a designated ingress point off the westbound
lanes. Morris adds that it is occasionally necessary to implement one
lane closures between 9 a.m. and 3 p.m. on the same side as construction,
but this is avoided wherever possible.
As an additional measure, activities not generating significant delivery
traffic such as dirtmoving and sub drain operations are scheduled during
the daylight hours, while paving operations are completed at night.
The volume of construction traffic and
associated vehicle movements is also being significantly reduced by
the reuse of site materials. Some 152 000 tonnes of Granular A base
is being salvaged from the existing median shoulder and incorporated
into the new road base, with the result that about 60 per cent of the
total Granular A requirement of 251 000 tonnes is being met by reused
material. Still on quantities, original job estimates called for 54
000 m3 of topsoil stripping from the median. In the event, the actual
quantity of topsoil removed was almost double this amount with a corresponding
increase in earth fill requirements. Fortunately, sufficient earth fill
was available from local commercial development sites to supplement
the original 22 000 m3 estimate.
Morris notes that the purpose of the OGDL is
to provide stability and drainage for the concrete surface and, like
many construction elements, it is probably subjected to its most severe
loading during construction. In this application, the exposed OGDL has
to carry direct loading of about 32 tonnes from trucks feeding the concrete
paver and there were concerns that OGDL rutting would result. To prevent
this potential rutting, the OGDL mix design has been modified by an
increase in both fines content and asphalt cement content to improve
mix stability. Superintendent Shane Fuller adds that keeping other site
traffic such as service vehicles off the OGDL can also be a challenge.
Staying on the theme of daily challenges and
solutions, the traditional stringline used for paving operations also
provides its share of headaches. The string line provides horizontal
and vertical control on the outside edges of the pavement during both
OGDL and concrete paving and is said to deliver the best pavement smoothness
results. For site crews however, the stringline means obstructed truck
access to the pavers, the need for frequent access breaks, restringing
and a trip hazard for the unwary.
As a footnote on smoothness, Morris reports
that the smoothness requirement on the new concrete was negotiated with
the owners at 90 per cent of the normal smoothness specification, recognising
that the inside edge of the new concrete has to match the existing concrete
surface.
Elsewhere, a number of measures
have been taken to streamline the construction process. During excavation,
for instance, the exposed clay subgrade was proof rolled as soon as
possible after excavation and covered with base material to minimise
its exposure to wet weather and the associated risk of soft spots and
rework. Even lane markings were fast tracked, with the eastbound markings
for lane shifts installed over the entire 22 km job during a full weekend
road closure.
The structural side of the project has also
created its own challenges and solutions. At the Humber Bridge, structure
construction included the installation of a 50 m long concrete girder,
although the current maximum length allowed for transportation is 40
m. An engineering solution was devised whereby two girders, 40 m and
10 m long, were delivered to site and laid end to end. Under the guidance
of bridge superintendent Giuliano Covassin, a joint was then cast around
the contacting ends and common post tensioning cables run through both
girders. After post–tensioning, the resulting 50m long prestressed
concrete girder was lifted into place, although a novel engineering
solution was applied here as well. Instead of utilising a conventional
gantry system, the lift was completed by two Liebherr LTM 1250 mobile
cranes set up on the existing bridge deck.
During the lift, it was estimated that the bridge
would be carrying a girder load of some 100 000 kg together with crane
counterweight loads of 114 000 kg and the self weight of both cranes.
To deal with this heavy loading, the bridge bearings were blocked and
load from the crane outriggers transferred to the existing girders by
temporary spreader beams. This novel approach reduced girder installation
cost and time, with the lift completed successfully over one weekend.
On the equipment front, Aecon’s site fleet
of Caterpillar dirtmoving and paving equipment includes 335 and 345
excavators as well as two full-time 14G motor graders equipped with
robotic machine control technology to control Granular A base material
grade. The OGDL was paved by an AP-1055B paver and compacted by just
one roller, a 534C dual drum unit, operating in static mode. For the
concrete paving, Dufferin Construction is using its venerable Guntert
& Zimmerman S1500 slipform concrete paver that has been used on
concrete paving projects across the country. This machine is capable
of paving two lanes and the shoulder in one pass and, with its integral
dowel bar inserter, will place 336 000 m3 of concrete on this project.
Aecon Construction & Materials is based
in Brampton, Ont. 407 International Inc. is owned by a consortium comprised
of Cintra Concesiones de Infraestructuras de Transporte, Macquarie Infrastructure
Group and SNC-Lavalin.
Back
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August/September
2006 issue
Aggregates
and Roadbuilding Magazine
4999 St Catherine Street West.
Suite 315
Westmount, Quebec H3Z 1T3
Tel: (514) 487-9868 Fax: (514) 487-9276
EMail: rocktoroad@sympatico.ca
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