The Civil Engineering Contractor May 2019 | Page 23

ON SITE: PROJECT 2
T
he P105-million project
was initially earmarked for
commencement in 2014 (and
had first been mooted as early as 2009)
under the Botswana Department of
Roads, but was taken over by SPEDU
in April 2017 for facilitation. Platjan
is located in the Bobirwa sub-district,
where there are border posts on
both sides of the Limpopo River that
constitute points of entry between
Botswana and South Africa.
The determining design criteria of
the bridge was to design at sufficient
level above the 15-year flood line.
The bridge is therefore cambered
and raised in relation to approach
roads. The in situ bridge deck spans
onto prestressed concrete bridge
beams 800mm deep, spanning
15.5m continuously over 1m thick
by 9m-high tapered concrete piers.
www.civilsonline.co.za
These are typically founded on 1.2m
thick × 9m × 4.5m-wide concrete
bases with 8No. × 5m deep, 32mm
diameter high-yield anchor dowels
on the upstream side and 4No. ×
3m-deep base anchor dowels on the
downstream side of the pier bases.
The final finish over the bridge
will be a 60mm layer of asphalt with
the approach roads having concrete
paving. Two agricultural culverts,
each 5m wide by 2.5m high, are
provided at chainages +0.180 and
+0.420, respectively.
Site project manager with Estate
Construction, Julius Katzke, explains
the commercial basis for the project:
“The Platjan border post is currently
not a commercial border. The nearest
commercial border is heavily backed
up with trucks waiting hours to
cross, and the strategic intent of this
development is therefore to turn
Platjan into a fully fledged commercial
border post to ease that logjam and
simultaneously stimulate the local
economy by providing improved
access for small towns and big farming
enterprises that are located within
a 35km radius. Increased through-
traffic will also create opportunities
for local hospitality businesses in and
around the border post.”
There is 40km of gravel road
leading to the border post on the
South African side, and more on the
Botswana side. These would have
to be paved. The current bridge
is regularly affected by seasonal
flooding, making it impassable for
both vehicles and pedestrians. The
most affected are farmers in both
countries, as they experience a
great inconvenience in crossing to
either side to sell their produce. The
business and farming communities
in the Tuli Block area have engaged
in business partnerships with South
African-based entrepreneurs on the
other side of the border.
The Platjan Bridge upgrade is part
of a bilateral covenant in which the
South African government committed
to construct a bridge across the
Notwane River in Ramotswa. Both
bridges are located at international
border posts and are meant to ease
travel between the two countries.
Scope of work
The bridge is of concrete and a hybrid
construction, its span being 155m with
10 equal spans. The overall bridge
width is 12.7m. The single carriageway
has two 3.7m traffic lanes — one in
each direction — with a 2m-wide
pedestrian walkway on either side of
the traffic lanes. The new bridge dwarfs
the existing bridge level alongside,
being 7.5m higher. The current means
of crossing the river is through a single
lane causeway or low-level culvert
with concrete pipes along the 100m
length of river width.
Quantities of material include:
• About 13 000m 3 of rock fill.
• About 3 500m 3 of gravel material.
• A total of 220 rock dowels will be
drilled into sound rock.
• A total of 54t of reinforcing steel
will be used for in situ culverts
construction.
• A total of 400m 3 of 40N concrete
will be used for in situ culvert
works.
• 
A total of 3 200m 3 of 40N
concrete will be used for the main
bridge works.
• A total of 210 prestressed T bridge
beams, each 15.3m long, will be
transported to site and erected.
• 120t of steel in the deck
• 2 200m 3 of concrete crunched.
At end-January, the bridge was 72%
complete, and was consequently
somewhat more advanced at the
time of the March site visit by Civil
Engineering Contractor, with all the
foundation concrete work done
by that time, barring the deck slab
and approach roads. The contractor
commenced work in early January
2018 and the project is set for
completion by end-June.
Katzke says the project, as a
Botswana project, had to procure
from local Botswana ‘citizen
companies’. One exception was the
precast concrete beams, as these
were not locally manufactured to
the appropriate quality, he says. Jaco
CEC May 2019 | 21