How NB DOT Builds a Highway
The
work to build a highway starts long before heavy equipment arrives
on the construction site.
1. Planning
and Public Consultation (Six to 12 months or more)
The
Transportation department’s planning and land management branch
take special care in choosing what they call a highway “corridor,” a
width of land suitable for placing a highway. They must make sure the
new corridor is a balance of engineering, environmental, social and
economic concerns.
To do this, they
develop a detailed map and compile and analyse a lot of information
on geographic, traffic, and environmental constraints as well as existing
development.
The department then
hosts public meetings so that New Brunswickers affected by the highway
can see the proposed corridor and make comments. Changes are often
made due to input received at these public meetings and are sometimes
taken back to the public for further input.
2. Environmental
Review, Surveys, and Preliminary Design (One to Three Years)
The
new corridor is registered with the Department of Environment and Local
Government and the provincial environmental impact assessment process
begins. Preliminary field surveys and environmental studies take place.
The centre line of the highway is also surveyed. Designers use this
information to create preliminary designs and identify how much land
is needed. Environmental consultants use the centre line to help them
identify where sensitive areas might be. Environmentally sensitive
areas may include areas of rare plants, endangered species, wetlands,
deer/moose yards (wintering areas frequented by deer/moose), etc. Based
on these studies, environmental conditions are placed on the design,
construction and maintenance of the highway and these must be incorporated
in the work.
A federal environmental
process under the Canada Environmental Assessment Act may also apply.
3. Design
and Land Purchase (One to Five Years)
The
department’s design branch uses the functional plans to carry
out a detailed survey and design. Project specifications are developed.
The department designs
the highway using Transportation Association of Canada guidelines and
accepted safety standards to maximize the protection of the travelling
public.
Right of Way agents
negotiate with land owners to purchase the land needed for the highway.
4. Grading
Once
the land has been acquired and a contractor retained through a public
process, construction work begins at the site of the new highway. Construction
signs are installed to warn motorists of the work. Any utilities that
may be affected are removed and/or relocated. Environmental measures
such as silt fences and erosion control structures are installed around
any watercourses.
The area where the
road is to be built is cleared of trees. All merchantable trees are
salvaged. After the trees have been removed, the remaining stumps are
removed by equipment with root rakes, which do not remove the valuable
topsoil.
Most roads are designed
to maximize the material available on site. This is called common excavation
or solid rock excavation. Excavated material is moved by large equipment
such as bulldozers, excavators, and trucks. However, sometimes some
material needs to be imported to the site. This material is called “borrow”.
As the highway is
constructed, layers of soil, rock and crushed rock are compacted by
equipment to make the road strong. As work continues, exposed areas
are stabilized by planting grass. Areas that are prone to erosion are
protected by rock called riprap.
The final touches
to the grading portion of the road are to topsoil the slopes and plant
grass using hydroseed. Now that this is complete, the road is ready
to be paved with asphalt.
5. Structures
Structures
are used to carry traffic over other roads, railway tracks, or water.
Structures are also called overpasses, underpasses, or bridges. Structures
can be single span or multi-span with columns between each span. A
structure consists of footings, piers, piercaps, abutments, beams and
a deck.
The footing is the
base of the structure. The pier sits on top of the footing and supports
the piercap. The piercap supports the beams and the beams in turn support
the deck. The abutments form the start and end of the structure and
support the beams as well.
The first step in building a structure is to build a strong footing. Generally
the structure is founded on firm ground. If the ground is not firm enough,
then piles are driven to provide the necessary support. Once this is done,
the shape of the footing is determined using a “form” and concrete
is poured into the form. Once the footing is hard enough, piers are “formed” on
top, followed by the piercap. The abutments are then completed. Once all of
this work is complete, beams are placed. Beams can be either concrete or steel.
Once the beams are placed, then the deck is placed. A protective barrier wall
is installed and the deck is waterproofed to prevent water from seeping into
the concrete. The final touches are to pave the deck with asphalt and mark
the road.
6. Paving,
Signing and Lighting
The
New Brunswick Department of Transportation uses asphalt to pave the
highway. Asphalt is a mixture of stone, sand and asphalt cement, which
gives the asphalt its black look and binds everything together. The
asphalt is placed and compacted to provide a smooth and dense surface
for traffic to drive on. It is sloped so that the water rolls off the
highway.
Once the asphalt
has been placed, the guide rail is installed, electrical wiring is
run to provide power to the lights, signs are installed and the marking
on the road are painted. The road is now ready to be opened.
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