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Contents
of February 1998
EDITORIAL
LETTERS
TREE OF THE ISSUE
INSPIRATION
Heritage Square, Loop Street, Cape Town
INSULT
Catchment management problems at Hennops River
DETAILS IN THE URBAN ENVIRONMENT
FEATURES
Taking tourists to the Table Top
Environmental
management during construction of toll road
146 000 recycled tyres used
for road revamp of N1
Designing service stations
-----
EDITORIAL
At the start
of a new year, The Urban Green File has a new Editorial Advisory Committee, as listed on
the contents page, and we would like to welcome our new multi-disciplinary team. The
journal also has a ‘new’ editor, as Carol Knoll has taken over a number of the
duties previously performed by Gerald Garner, giving him more time for his duties as
publisher and advertising sales manager. We have, unfortunately, to say goodbye and thank
you to Pieter Snyman who helped us to get the journal off the ground with his selling
abilities. Philippa Brown and Gerald will share the sales portfolio.
The
Townscape Millennium Public Spaces competition is a new project for 1998/9 and we are
delighted to be working with Enviro Elements who have sponsored the competition. The
particulars are on page 22 and we hope that many municipalities and other landowners will
participate to help us find the overall ‘best public open space’ in the country.
This is our
urban transport issue and looking back to last year’s issue and our article on
Sandton’s first official taxi rank, we have, sadly, to report that the rank which was
due to open last February is still shrouded in barbed wire and the number of attempts that
we have made to establish the reason for this have been met with no response. The PR
Department of the Eastern Metropolitan Local Council (EMLC) has simply fobbed us off -
which makes us think that there is egg on somebody’s face. Could the problem have
stemmed from lack of adequate public involvement at concept stage? Are the taxi drivers
unhappy? The Sandton ratepayers have the right to be! We are guessing, and we hope that
the EMLC will respond to these comments.
In closing,
we would like to extend our heartfelt thanks to all our advertisers and subscribers who
have shown faith in us and are the reason we can continue to publish The Urban Green File.
-----
LETTERS
Beach churned up by 4x4s
As a tourist
in Port Alfred over the holiday season, I was most distressed by the number of 4x4
vehicles that were allowed onto the East Beach near the Kowie River mouth.
Environmentally, they seemed to show no respect for the tidal lines and besides crushing
many shells, including live oysters washed up on the beach, they churned up the strip of
beach - destroying its beauty for others. With the increase of the number of luxury 4x4s
on the roads, this problem is on the increase and should not be ignored by local councils.
- Sarah Crawford.
One-sided
reporting
With
reference to The Urban Green File Nov/Dec 1997 issue, we would like to express our
disappointment at your one-sided reporting, regarding one of our developments. On page 10
of the above publication, you have an article headed ‘Insult’ and the photograph
adjacent to this article is our Strijdom Commercial Park Phase II project. We wish to
correct the contents of this article as follows:
•
The embankment is
being retained and protected using stone gabions. All loose material will be removed from
the embankment as part of this construction. This is now underway - but was programmed
long before your article was published.
•
This protection has
been the topic of much discussion and negotiation between ourselves and the local
authority for a considerable time. Your comment that we have "a total disregard for
this precious water source" is therefore without foundation and simply untrue.
•
Furthermore, the
embankment, in fact, has little impact on the river course. Only under 50 year flood
conditions is the embankment involved and only as a result of the restriction of the river
as it passes below the freeway, a short distance downstream from our development.
•
The free flow is in no
way hindered by this embankment, particularly as the volume, at this point, is larger than
most of the length of the Klein Jukskei throughout Strijdom Park.
•
We would also like you
to know that we spent ± R 750 000 last year on landscaping at our various sites. We
planted some 120 trees on one project in Rivonia alone. While it is an unfortunate part of
development that some trees and existing plants need to be cleared, on the whole we
replace far more trees than we remove.
We request
that, in future, you investigate more thoroughly before you publish such articles.
- R Cottril - Abland (Pty) Ltd
Ed: Although measures are now being undertaken to retain the
embankment in the form of a stepped gabion retaining wall, when we wrote the article, soil
and building rubble was slipping down into the river.
The
real problem, though, seems to be that councils are being more lenient with 50 year flood
lines, thereby allowing all sorts of encroachments into these integral components of river
systems. During floods, silt is deposited on flood plains and because development is
allowed to encroach into these spaces, silt cannot be deposited - and is carried further
resulting in damage downstream (see the ‘Insult’ for this issue on page 21). It
is, however, encouraging to see that developers, such as Abland, are taking environmental
issues seriously. (Pub. Ed.)
An
attempt to retrieve the situation
In
our July/August 1997 issue, we gave our so called ‘Insult to the Urban Environment
Award’ to two "desert-like parking lots" in Fourways. The one comprising
the garden centre has now partially retrieved itself by planting a few (very few) oak
trees, which will probably start to provide some decent shade when our children are
middle-aged. The oak saplings are, however, clearly taking strain and one has already
died. We suspect that the reason for this is that the oaks, being ill-suited to our
climate in the first place, are suffering from heat stress resulting from their harsh
tarmac environment.
-----
TREE OF THE ISSUE
Millettia grandis
Commonly known as the
Umzimbeet
In 1998, The Urban Green File will be inviting various specialists in the
landscaping and horticultural fields to choose the Tree of the Issue and to motivate their
choice. The tree will always be indigenous, because we believe that South Africa’s
tremendous plant wealth is often ignored by the design professions, and will be
appropriate for use in the urban environment. Landscape architect, Erika van den Berg, has
made the choice for this issue.
Millettia
grandis is indigenous to the coast of KwaZulu-Natal and the Transkei, having a relatively
limited natural distribution, largely in coastal forests - and Erika, who practises as a
landscape architect in Gauteng, has not yet specified the tree for any large landscaping
projects but has had it ‘on trial’ in her own garden and is now satisfied with
its ability to cope with conditions in this area.
She
comments: "I love the tree because it has so many points of interest and aesthetic
qualities - from its beautiful new growth where the fresh green is shielded by purply
coloured hairs, to the darker green foliage of the mature tree, the lovely mauve flowers
and, finally, the woody pods with their golden sheen of hairs (that are nice to touch
too). In its natural environment, the tree has a wide spreading crown - whereas it is
sometimes inclined towards a more rounded growth habit in Gauteng. I have also found that
it is more inclined to be single-stemmed up here, whereas in its forest environment it is
usually multi-stemmed.
"One of
the nicest things about it is that although it is deciduous, it loses all its leaves in
one week and the new growth appears immediately. In Natal, certain butterfly species
utilise the pods at larval stage but I have not noticed this happening in the Transvaal.
(Braam & Piet van Wyk’s book Field Guide to Trees of Southern Africa records that
the butterflies Deudorix diocles and Charaxis pondoensis breed on the tree.)
"People
tend to steer clear of coastal species up on the highveld when, in fact, many species do
well. M. grandis germinates quickly and grows relatively fast up here. It does grow faster
at the coast - up to 1 m a year, but achieves up to 0,5 m here, without frequent watering.
It is sometimes slow to take off and needs additional moisture when it is very young. The
oldest specimen in my garden was planted 10 years ago and is between 4 - 5 m tall. Our
property is relatively cold because it is quite low down on a slope and it has coped very
well with the cold."
-----
INSPIRATION
Heritage Square, Loop Street, Cape Town
At the risk of sounding repetitive, I will say, once again, that Cape Town must be the
only African city that is undergoing a spontaneous renaissance. Examples abound throughout
the city - from individual shops and restaurants which have, collectively, transformed the
likes of Long and Kloof Streets to larger projects such as the recently completed (Phase
1) Heritage Square.
It appears
to me, as a recent resident of Cape Town, that the initiatives of Council in previous
years - such as the development of St Georges Mall - have laid the foundation for private
entrepreneurs to restore, recycle and revitalise old buildings within the city, reflecting
its history in a functional and vibrant manner.
Developed by
Montsi and Shortmarket Properties, in conjunction with the Cape Heritage Trust, Heritage
Square is a restoration of a group of 18th century buildings which have been consolidated
into a "self-contained community of restaurants, art galleries, jewellers, clothing
and textile designers, wine merchants and a five star hotel". (Off the Cuff
Productions press release 1997.)
My first
visit to the complex was during the evening - my impression, one close to awe! A
subsequent return visit, in the harsher light of day, tended to mute this first
impression, somewhat - but criticisms tend to concern detail rather than the broader
ambience, which is largely anchored around the central courtyard onto which the hotel,
restaurants and many of the shops open, providing an al fresco setting shaded by overhead
decks and vine covered pergolas. The resulting quality, European in character, reflects
the understated architectural urbanity of this precinct - circa 1800.
Similarly,
the treatment of shop frontages is restrained to the point where they might go unnoticed
by the passer-by - and for this the developers need to be commended! They have resisted
the temptation to ‘Disney World’ the development for the sake of ‘frontal
hype’!
Criticism of
detail - the pond, an architectural afterthought; the exterior beams not matching the
solidity of the interior; and the patched grouting to the stone walls - tends not to
detract from the whole.
Yet another gem for the city - long may it continue.
-----
INSULT
Catchment
management problems at Hennops River
Symptom of man’s
interference with a river course
This scene
of devastation, photographed at the end of winter last year, is the Hennops River just
downstream of the badly silted Centurion Lake. The trees that are falling into the river
are large, old, indigenous River Bushwillows (Combretum erythrophyllum), White Stinkwoods
(Celtis africana) and Sweet Thorns (Acacia karroo), which gave a magnificent ambience to
this stretch of the Hennops and were cherished by the old Verwoerdburg Parks Department
(in the days of Andrea Hepplewhite).
The Urban
Green File visited the scene again in late January this year to find that the situation
had worsened and although there is little hope of saving these trees because the
embankments are so badly undermined already, the Centurion Council is clearing the river
of debris further downstream and widening the channel in an effort, presumably, to limit
this undermining of the banks and the continual flooding of the adjacent Par 3 golf
course. Whether it will work or not remains to be seen - it will probably only provide a
very temporary solution.
In our
‘Urban Rivers and Wetlands’ feature later this year, we will be looking at the
Hennops in more detail and at Catchment Management Plans which could, in the future, make
all the difference. Certainly, no single agent is to blame for this ‘Insult to the
Environment’. It is a complex catchment management issue.
-----
DETAIL IN THE URBAN ENVIRONMENT
This is the start of a new series which The Urban Green File will carry as a regular
feature in each issue. We believe that interesting detailing is a vitally important
element in the urban landscape - adding vibrancy to our towns and cities and establishing
a sense of community, and a sense of pride in our surroundings. Because this is our ‘urban
transport’ feature, we have chosen street furniture details related to the transport
environment.
In future,
readers may wish to participate by sending in a photograph of an interesting detail,
accompanied by a comment, so that we can give coverage to those towns and cities that the
editorial team has not had the opportunity of visiting, recently. Forthcoming issues will
carry signage - including murals, walls, paving details, areas of informal trade –
vendors’ shelters, sculpture, pavement gardens, benches, doors and gateways,
lighting, retaining walls, water features - and anything else that is interesting,
attractive or even humorous - and adds value to the urban environment.
A sculptural
element with the functional value of a bollard, a small detail which is part of the
on-going ‘full scale urban upgrade’ of Johannesburg by the Urban Development
Cluster of the Southern Metropolitan Local Council, started in 1995. Li Pernegger of the
Urban Development Cluster commented that these carved bollards at intersections in
Commissioner Street, representing aspects of street life such as the repairing of shoes,
mini-bus taxis, the hailing of a taxi - depicted by a hand with a finger pointing upwards,
and other such, seemed to be serving as a kind of (psychological more than physical)
barrier to keep pedestrians from spilling out into the street.
She said
that the appreciation of these small sculptures was very real and that this was shown by
people touching them as they passed by and the fact that only one had been vandalised in
all the months that they had been there. She said that a public participation exercise had
been carried out prior to the start of the inner city upgrade, in which the informal
traders, shopkeepers and property owners had all provided input. Anthony Filbrick was the
architectural consultant on the project.
Bus shelter
on Jan Smuts Avenue in Rosebank with sloping wooden seats ensuring that water blown in
during the sharp, highveld storms runs off, rapidly.
An avenue of
bollards demarcates a pedestrianised section of Kerk Street in Johannesburg.
A bank of
public telephones under the escalators at the Star Stop Egoli on the N1 highway (see
article on page 17). Peter Schuen of Winterbach Pretorius White was responsible for the
design of these innovative, curved stands with their powder-coated metal finish. The idea
was to break away from the usual perspex kiosk and to give a transparent, open feel to the
area. An appealing concept. Looks almost like: ‘E.T. Call home!’
A sculptural
element of a sort? These unusual bicycle stands also provide advertising space, while
taking up very little room in a crowded parking lot. "Park your bike and pop in for a
coke!"
A convex
bench seat with the same function at a newly revamped station in Pretoria. These small
details add to the comfort of commuters.
-----
FEATURES
Taking tourists to the table top
Table
Mountain’s cableway and tourist visitor’s facilities have recently been given a
facelift
South Africa’s
most famous but also one of its most environmentally sensitive tourist destinations has a
new cable car system. Gerald Garner went up Table Mountain to visit the new development
which adheres to the highest environmental standards.
Most South
Africans, and especially Capetonians, regard Table Mountain as ‘their mountain’.
Attempts to develop on its slopes have caused mass demonstrations (Oudekraal) and even
motivated a model agency to make its time and models available for a campaign to save the
mountain. When the first rumours surfaced during the early ‘90’s that the
cableway was to undergo a revamp, the response was as dramatic. Eventually, more than 200
interested and affected parties voiced their opinions during the IEM process (288 parties
were contacted). Ideas and opinions were as diverse as the flora and fauna on the
mountain. Even the radical proposal of a tunnel inside the mountain was mooted to minimise
the visual impact of transporting tourists to the mountain top!
The Table
Mountain cableway project is due for completion during April 1998 but the new cableway has
already been open to the public since October 1997. The project comprises the renovation
of the existing upper and lower stations, a new cable car system, restaurant, bistro,
curio shop, ablution facilities and sewage system and sub-surface reservoir, as well as
walkways and viewpoints on top of the mountain. At the lower station, new parking
facilities have been provided.
Environmental Impact
Assessment
Environmental consultants, Crowther Campbell & Associates, identified three critical
aspects during the EIA that needed further investigation: carrying capacity, impact on the
vegetation and visual impact.
In order to
enable the architects and landscape architects to design adequate facilities, the expected
number of visitors and the carrying capacity of the mountain had to be established.
Factors such as the required level of service in restaurants, the sensitivity of
vegetation to traffic and the unique (not over-crowded) experience, that visitors seek,
were considered.
The EIA
recommended that new walkways should be designed to encourage visitors to stay on paths so
as not to disturb the fynbos, and that sensitive areas should be bridged with wooden
boardwalks to create protected, moist areas where plants can thrive.
The visual
impact study focused mainly on the impact of the buildings and it was recommended that the
facades should be broken up into smaller pieces and disturbed areas around the
construction sites rehabilitated.
Environmental
Management Programme (EMP)
Jaana-Maria Ball, environmental scientist at Gibb Africa, elaborates on the EMP
which includes elements of a broader Environmental Management System that was based on the
ISO 14001 standards: "A mutli-disciplinary team of specialists, known as the
Environmental Management Team (EMT) was appointed to assist in dealing with potential
environmental problems and ensuring compliance with the EMP." The team included
representatives of the TMACC, National Parks and City Council; consultants, specialists
and the contractor - and they met once a month. "The discussion created a sense of
commitment amongst those involved and increased the consideration given to environmental
criteria during the design and construction phases," says Ball.
In keeping
with the EMP, environmentally sensitive areas were fenced off and declared ‘no-go’
areas during construction, and site works were limited to previously degraded areas. The
contractors constructed raised platforms that allowed the penetration of light and air to
protect plants and lichen covered rocks, as well as an elevated rail system that extended
across the site so that bagged, excavated material could be transported to the loading
platform. It was taken down the mountain on the temporary materials cableway.
The most
significant aspect of the EMP was the requirement that all contractors had to submit a
written method statement to the Environmental Control Officer describing the envisaged
method of construction for any work to be done. "It is details such as how the
contractor lays a new path or how he discards the material from the old path that are of
concern," says Ball. Method statements ensured that potential problems could be
identified before construction commenced and suitable solutions found.
All
construction personnel attended environmental training sessions, which touched on aspects
such as the project background, ecology, environmental control and an overview of the EMP,
before they came onto site. Workers also competed for a monthly environmental award and
due to the fierce competition, selecting a winner proved to be extremely difficult.
Architecture
The revamped cableway stations are more visitor orientated than their
predecessors. Because of technical requirements, the cableway machinery had to be moved
from the upper station to the lower station, thereby creating the opportunity to ‘exhibit’
the machinery as a focal point in a glass cage. The ticket offices and queuing area have
also been moved to the seaward side of the building, giving visitors a view towards the
city.
The upper
station has been enlarged with added viewing platforms and a bistro. However, the
architects managed, through the manipulation of facades (by breaking these down into
smaller articulated pieces) to understate the actual size of the station. The facades are
finished off with an exposed aggregate known as ‘UCT plaster’ or ‘Luytens
plaster’ in order to blend more effectively with the mountain.
The new
restaurant (currently under construction) is positioned behind the old restaurant
(historical stone building) which now functions as a curio shop, where the former is the
least visible. This building is excavated into the rock so that it is not visible from the
upper cable station or from Camps Bay below.
Landscape architecture
On top of the mountain, carefully planned pathways and view points add to the
experience of the visitor. "To bring people closer to the edge of the mountain, where
they can experience as many views as possible in different directions" was the aim of
landscape architect Steyn Swanepoel of OVP Associates. Previously, the pathways
criss-crossed through the middle of the mountain, limiting the experience of the
magnificent views.
Two circular
routes, an inner circle ‘10 minute walk’ on a 3 m wide pathway and an outer
circle ‘20 minute walk’ on a 2 m wide pathway, surround a core conservation
area. The ‘outward’ experience is of magnificent views, whereas the ‘inward’
experience is of the fynbos on Table Mountain. Swanepoel explains: "We tried to
preserve the feeling of being in a pristine environment, in spite of all the man made
structures on the mountain."
Designing
the pathways was no easy task: "We could not simply demolish everything on the
mountain and start from scratch. We had to work carefully around rocks and plants, often
designing on site, which made it impossible to quantify materials before construction
commenced and even more difficult to budget ahead," he comments.
The old
pathways were constructed from stones collected on the mountain, causing the surfaces to
be uneven and too similar in appearance to the surroundings. The surfaces of the new
pathways comprise a mixture of aggregate (crushed stone from the mountain) and coloured
cement with sandstone edges, which provides a natural feel while clearly distinguishing
walking areas from natural areas. However, due to environmental constraints, it was
impossible to wash the surfaces during construction (so as to expose the aggregate)
because the cement and water mixture would have encroached into the fynbos. The result is
that the surfaces do not look as natural as intended but these should weather over time.
During construction, the cement was poured onto a layer of geotextile so that the pathways
can be easily removed without leaving any permanent scarring, should there be another
upgrade in the future.
View points
are positioned along the pathways so as to preclude any culs-de-sac and resulting two-way
traffic. OVP Associates specified two contrasting materials for the pathways and view
points: aggregate surfaces with sandstone walls and timber surfaces with steel
balustrades. Sandstone blends with the natural mountain scenery. However, as the sandstone
pieces on the mountain were not big enough for coping stones, Tora-Tora supplied stone
from their Vanrynsdorp quarry (which forms part of the Table Mountain sandstone series).
Timber view points and bridges span sensitive vegetation, where necessary. The Waterfront
Wood Company imported Balau wood from Asia for the boardwalks and view points because it
was the only wood that was guaranteed to withstand the harsh conditions and traffic
volumes.
Rehabilitation
All the plant material was sourced from the site so as to prevent unnatural
genetic drift, which occurs when imported indigenous plants interbreed with local plants.
Seeds and cuttings from the areas to be disturbed were collected before construction
commenced. Gael Grey of Good Hope Nursery, who succeeded in growing 55 of those species
occurring naturally around the lower and upper cableway stations, comments: "Of the
range of plant species that was dug up, mainly geophytes and resprouters transplanted
successfully into bags." Grey used a growing medium comprising sand, bark and peat
mixed with soil from the site. "The soil was a wonderful source of seed and a lot of
germination of herbaceous seedlings and Restionaceae took place in the bags." Grey
used only the growth stimulator, Kelpak and the fertiliser, Seagro to stimulate growth.
Plants from the two stations were kept separate to avoid the mixing of material from two
very different environments.
Rod Tritton
of Gardenlife Landscapes says that the challenge of the rehabilitation process was
"the need to plant so that the plant doesn’t appear to have been planted."
They did not attempt to reproduce the exact landscape that existed prior to construction:
"The numerous dassies (unfortunately, attracted by the public who feeds them) had
caused a degraded and species impoverished environment with only a very few unpalatable
plant species thriving - for example the Blister bush (Peucedanum galbanum) and Climbers
friend (Cliffortia ruscifolia). The former is not a plant species one wishes to inflict on
the public and the latter is difficult to propagate," he explains.
Water provision and
sewerage
Water, electricity and sewage services often have a real and very visible
impact on the environment. On Table Mountain, care was taken to minimise these impacts -
the old reservoir and septic tanks were built on top of the mountain with a significant
visual impact. However, both have been demolished and a new sub-surface reservoir
constructed.
Consulting
engineers, Hawkins Hawkins & Osborn, recommended the use of a plastic HDPE pipe - as
it is easy to bend and can therefore be hidden between the rocks - to pump water from a
fountain to the 400 kl underground reservoir. Both cable cars also have 4 kl water tanks
under their floors which can transport water up to the top.
At the lower
station, sewage previously flowed into a ‘soak-away’ septic tank but this is now
connected to the municipal sewer via a pipe underneath the road. On the top of the
mountain, the engineers are still looking for the best solution but, in the interim,
chemical toilets in conjunction with a septic tank and ‘soak-away’, are being
used. According to the engineers, the final solution will be a pipeline down the mountain
but an appropriate route still has to be identified.
Johan
Koegelenberg, Project Manager for Murray & Roberts, describes the project as a special
challenge: "Working on top of a mountain in harsh weather conditions, taught us to
work with, rather than against, nature." At an environmental cost of R 20 million of
the total project cost of R 90 million (22%), the Table Mountain cableway project sets a
precedent that emphasises the importance of environmental aspects for other sensitive
sites.
Project team:
Client: Table Mountain Aerial Cableway Company (TMACC)
Project managers and civil contractors: Murray & Roberts Cape Ltd
Architects: MLH
Civil and structural engineers: Hawkins Hawkins & Osborn
Electrical engineers: CA du Toit
Quantity surveyors: MLC
Landscape Architects: OVP Associates
Environmental consultants (for TMACC): Crowther Campbell & Associates
Environmental management consultants (for South African National Parks): Gibb Africa
Cableway contractors: Garaventa
Landscape contractors: Garden Life
-----
Environmental
Management during construction of N1 toll road
Ensuring
that construction work on the N1 toll road to Pietersburg caused minimal damage to the
environment
This new
stretch of 100 km of road from Middlefontein (just north of the Nyl River) to Pietersburg
is a Build Operate and Transfer (BOT) project - meaning that financing for the
construction of the road is organised by a private corporation which then builds the road
and operates and maintains it for 25 years, after which the road is transferred back to
the state. After the alignment of the road had been determined, the Department of
Transport called for tenders and various teams put in bids. The successful team formed a
company called the Northern Toll Road Construction Ltd (NTRC) and BKS, a member of the
NTRC and the consulting engineers responsible for the detail design of the road, appointed
the environmental consultants Cave Klapwijk & Associates (CKA) to ensure that
construction work would cause minimal damage to the environment. Carol Knoll asked Alan
Cave to comment on the project.
Prior to the
start of the BOT operation, consulting engineers Stewart Scott Incorporated, who were
responsible for the road alignment study, utilised the services of environmental
consultants Mark Wood Consultants to do a preliminary impact assessment to identify
critical areas and as a result of this study specialist ecological investigations were
done on the sensitive Nylsvlei area and the alignment of the road was moved to accommodate
a Bat hawk nesting site. Cave commented that the lack of a formal Environmental Impact
Assessment (EIA) on the final alignment had, however, resulted in certain important
botanical and archaeological sites not being identified, timeously.
CKA drew up
an Environmental Policy document which recommended methods that would reduce the cost of
rehabilitation and Cave monitored the construction process, providing advice on any
environmental problems as they arose. Cave said that most of the recommendations had been
followed and in instances where they had not, extra costs had sometimes been incurred. One
of the most important aspects of this document emphasised the need to conserve topsoil,
and calculations showed that if the correct stockpiling procedures were followed, the end
result would be a surplus of topsoil. However, in the end, topsoil had to be brought in,
largely because, in the initial stages, valuable topsoil was used as fill or lost in
preliminary earthworks.
The document
suggested that there was no need to clear all the bush within the road reserve and that
only areas in which the actual work was taking place, and the service roads, needed to be
denuded of vegetation. CKA also liaised with Willem van der Merwe, responsible for road
verge maintenance with the Dept of Transport, and permission was given to change the
mowing standards in the road reserve. Usually, the whole reserve is cleared with flail
mowers on a regular basis, but it was agreed that a 6 m wide firebreak on the road reserve
fence and one of a 6 m width off the shoulder of the road would be adequate. The result,
where this allowance has been followed through, has been a very natural finish to the road
and a good blend with the surrounding environment.
Hydromulch
served as the revegetation contractor on the project - sub-contracted to the consortium of
contractors, LMG - and they, with their many years of experience, provided recommendations
for the grass mix. Eragrostis tef was used as a pioneer but the amount of seed in the mix
was reduced because the species competes with other germinating seed for moisture. The
proportion of Eragrostis curvula was also reduced because this grass with its weeping
tendency is inclined to shade out other species. It was decided that the accepted 45 kg of
seed mix per ha could be safely reduced to 20 kg / ha for hydroseeding purposes.
CKA used the
services of botanical consultant Fanie Venter to identify plants that occur naturally in
the area for planting in the road reserve. Venter identified the various vegetation belts
that the road traverses and drew up an appropriate list according to these. The start of
the road from Middlefontein across Nylsvlei towards Potgietersrus is characterised by
flats, predominantly sand over clay covered in ‘mixed bushveld’ (Terminalia,
Combretum and Euclea) with an intervening tongue of heavy clay soils with ‘clay thorn
bushveld’ (mainly acacias) as the vegetation type, while the rocky areas north of
Potgietersrus show an increase of Combretum species. A small section of dolomite occurs in
the area of the Sebediela toll plaza where Kirkia accuminata is the dominant tree. Between
this dolomite area and Driefontein, shales dominate and the vegetation is varied, with
Peltophorum africanum in evidence - whereas at Driefontein the existence of granites and
dolerite dykes means that there is a mosaic of Combretum, Euclea, Cussonia and Acacia
species. North towards Pietersburg, the soils are highly erodible and Aloe marlothii is in
abundance with Acacia rehmanniana dominating, particularly in a belt adjacent to the road.
Trees characteristic of each area were used in the road reserve rehabilitation of that
area.
After CKA
had been appointed, there was an almost negligible period of three weeks available to them
before the bulldozers were due to go on site and they managed to advise Nature
Conservation who informed the Succulent Society that numerous aloes were going to be lost
and, as a result, interested people collected many of these as they were bulldozed out of
the ground. The Potgietersrus camping site collected the largest number and have used
these to good effect. Along with the many shrubs and trees that were acquired and planted
as part of the revegetation process, 2 000 aloes were planted at strategic sites but
numbers of these have, unfortunately, been vandalised by inquisitive baboons.
Cave pointed
out that the lack of an adequate vegetation study which would have been part of a formal
EIA had resulted in the destruction of an unusual grouping of plants in the dolomitic area
at the Sebediela plaza, where the road had been routed through the large Planknek cutting.
Venter explained that the vicinity of this cutting was on a fault line and that the
movement of the two ‘blocks of earth’ meant that different types of geological
matter had been deposited there creating a rich variety of soil types, resulting in a
variety of habitat sites - ecological niches - and the area of highest species diversity
in the Buffelshoek/Highlands ranges. He said that, amongst others, a community of
Ceropegia verruculosa, a succulent climber, had been lost and this was classed as ‘rare’
in the Red Data Book. He commented that such a combination of geological and other factors
was invariably indicative of a high impact area and that even someone with a rudimentary
knowledge of ecological matters should have been able to see this. Sakkie Schabort of
Northern Province Nature Conservation lodged a belated objection to this routing,
immediately he became aware of it.
Mark Wood,
the consultant involved at the road alignment stage, said that he had recommended a
detailed vegetation study for the Planknek area but for some reason this had not been
carried out.
Cave spoke
about the low priority given to the impact of crushing stations, gravel stockpiles and
borrow pits during road construction, in general. Large areas of vegetation need to be
cleared for stockpiles and, additionally, stormwater rushes off these piles and scours
deep gullies in the neighbouring terrain. Cave suggested silt retention dams to prevent
this erosion and his advice was followed, with an element of success, on both the
Hartebeeslaagte and Driefontein stockpiles.
The
principle of using rock from the road cuttings to provide the crushed stone for the road
base was followed on this project but the material from the large Driefontein cutting was
found to be too soft and an extra quarry had to be opened, resulting in the repositioning
of the crusher station and stockpiles. The 260 000 m3 of spoil from the Driefontein
cutting was stockpiled in an area, identified by Cave, where the visual impact could be
mitigated. The stockpile was rounded off into a natural form and grassed. Some of the
poorer spoil material was used to fill the shallow borrow pits on farms adjacent to the
road and most of these were topsoiled and grassed, while in some cases farmers requested
that they be left open to collect water. Cave noted that some of these had created
valuable aquatic habitats.
Cave said
that the Planknek cutting had been an area of concern both during the excavation and
rehabilitation stages. It is a very large cutting (one of the biggest in the country), 300
m across and 45 m at its deepest point. The geology of the cutting was carefully examined
prior to excavation and the team agreed that the pitch of the slopes could be varied,
depending on soil and rock type and stability factors. They needed to be almost vertical
where there was a hard band of quartzite, whereas weathered dolerite allowed for more
flattened slopes, generally lending a more natural appearance to the cutting. Only the
quartzite was blasted, using the technique of ‘varied hole depth blasting’ to
create a more natural, rough finish.
The gentler
slopes were topsoiled and hydroseeded and CKA recommended the use of a biodegradable jute
geotextile as a surface soil stabiliser but this was ignored because of the extra expense.
The topsoil washed down the hill four times and had to be replaced each time, at great
cost, before the geotextile cover was finally installed.
Cave
commented that another concern of theirs had been that no proper investigation had been
done to see whether the road route traversed important archaeological sites. In the three
week period prior to the arrival of the bulldozers, he had asked Prof Tom Huffman of the
Wits Dept of Archaeology to look for possible sites and an excavation carried out on an
identified site produced information that indicated that there were other sites of value
in the area - but lack of time precluded further investigation.
At one of
the first meetings, Cave had asked the NTRC about the lack of provision of ‘stopping-off’
points or viewpoints, and had been told that these were not considered necessary because
of the petrol station/food outlet complexes along the route.
In
conclusion, Cave said that he was, generally, satisfied with the rounding off of the cut
and fill areas and felt that a natural blend with surrounding landscapes had been
achieved. He said that the chief landscape architect of the Department of Transport, Ricky
Samyn, had supported the approaches taken. Cave added that the proposals to curb
activities detrimental to the environment made by CKA during the construction phase had
always been discussed in detail and given due consideration - and that Eugene Erasmus, LMG’s
project manager, and the project engineer from BKS, Schalk Hanekom, had supported CKA’s
aims.
"Engineers
are becoming more sensitive to the environment and, on many projects, specifications which
will help to mitigate impacts are written into the contract documents, meaning that the
contractor has to take them into account," was Cave’s final comment.
Ed: The new
environmental impact regulations under the Environment Conservation Act, have made EIA’s
compulsory for "...roads, railways, airfields and associated structures outside the
borders of town planning schemes." Hopefully, these regulations will ensure better
integration between environmental work done at road alignment stage and that done during
the construction phase.
Project team:
Client: SA Roads Board
Engineers: Stewart Scott Inc and BKS
Main contractor: Northern Toll Road Venture and Northern Toll Road Construction (NTRC)
Contractors: LMG Joint Venture (LTA, Murray & Roberts and Grinaker); LET Construction;
Basil Read
Environmental consultants: Cave Klapwijk & Associates
Revegetation sub-contractors: Hydromulch
-----
146 000 recycled tyres used for
road revamp of N1
The 34 km
stretch of the N1 between Pienaarsrivier and the start of the new toll road has recently
been upgraded, and the bitumen-rubber binder ARM-R-SHIELD made by Tosas, a subsidiary of
Sasol/Total, was used in the renovating process. Ian Rademeyer of Tosas has calculated
that the treads of 146, 000 vehicle tyres were used in the binder for this section of
road.
The peelings
and buffings (rubber tread) obtained from tyres during the retreading process are milled
down into fine particles and blended with bitumen at 230șC to form the bitumen-rubber
binder. Because this product needs to be applied to the road surface almost immediately,
this blending process is usually carried out in mobile units on site. The product is then
loaded into trucks and sprayed onto the road surface. A follow-up truck spreads stone
chips over the binder and this surface is compacted with rollers. The product sets rapidly
and each section of the N1 that was being worked on was only closed to traffic for a few
hours.
The rubber
content in the product is 22 % and its function in the binder is to limit degradation of
the road surface. This is achieved through a natural element in the rubber called ‘carbon
black’. The rubber also provides added flexibility which will prevent extensive
cracking of the surface, over time. According to Rademeyer, rubber/bitumen laid straight
onto a cracked surface will prevent the existing cracks from coming through, giving it an
edge on conventional bitumen binders. He said that the Pienaarsrivier contract was a
so-called Product Performance Guarantee System which had to be guaranteed for six years,
and because it was the first thin surfacing contract of this kind, a ‘peace of mind’
product such as the rubber/bitumen binder made sense.
Rademeyer
also pointed out that bitumen is not a toxic substance and therefore is a safe product to
spray. At ambient temperatures, it is non-toxic, non-volatile and odourless and it has
also been declared non-carcinogenic.
Tosas
operates under the internationally recognised yardstick for environmental management, ISO
14001, which it was awarded close on two years ago after being audited by an accredited
team sent out from Switzerland. Rademeyer commented that Tosas was the first South African
company to be given ISO 14001 accreditation.
-----
Rest-stop facility integrated
into urban interchange
Economical
user of land: Star Stop Egoli, Midrand
After the
recent outcry by Edenvale residents against the proposed Linksfield Skydeck on the N3, The
Urban Green File has followed the construction of the Caltex Star Stop in Midrand with
great interest, noting that the facility is an economical user of land - with the service
stations slotted in under portions of the road bridge and an unimposing, yet attractive,
restaurant facility that does not impinge excessively on the skyline. The signage is the
only aspect that is somewhat obtrusive and one questions the need for this. Carol Knoll
spoke to Ian Pretorius of Winterbach Pretorius White Inc, the architects and project
managers of this new facility who have been responsible for a number of what they term
‘rest-stop facilities’, countrywide. Landscape architect John Drummond was also
asked to comment.
Firstly, Pretorius pointed out that the name ‘skydeck’ could not be applied to
the new Midrand facility, because the latter was a patented idea in which the petrol
pumps, along with other facilities, were located on the actual deck - it implied something
imposing and a large user of land. He also made the comparison with the Petroport on the
N1 near Warmbaths, saying that, historically, such facilities required a large expanse of
land for extensive parking areas and to accommodate the turning circles of large trucks.
The Total Panorama, near Warmbaths, is set in a rural landscape with virtually no
constraint on available land, whereas the Star Stop in Midrand is a compact user of land
and is carefully integrated into an unusual urban interchange.
The Star
Stop is unique in that it is accommodated within the first single-point or ‘butterfly’
interchange in the country - with a single set of robots, on the bridge deck above the N1,
controlling all the traffic. Normally, urban interchanges make use of the clover-leaf
configuration which occupies a much larger expanse of land, and the cost would have been
prohibitive within the urban environment of Midrand. Another unusual aspect is that the
interchange has been retrofitted into the highway environment, while the Star Stop
facility was accommodated within the interchange by the excavation of the crown of a hill
to reduce levels to that of the freeway. Six additional extention bridges ‘fly’
the traffic over the facility to the ‘butterfly’ bridge.
The question
automatically posed itself: Was there a real need for another facility in such close
proximity to the Shell Ultra City? Pretorius answered that projected traffic volumes
indicated a marked increase in daily traffic over a five year period at this point on the
N1 - from 91 700 vehicles, travelling in both directions, recorded in 1995 to 103 560
predicted for the year 2000. This, he said, implied potential crowding at the neighbouring
Ultra City, in the near future.
Noise was a
vitally important consideration at planning stage and Pretorius pointed out that to
accommodate the movement of vehicles within a very confined area, virtually the entire
site had to be paved. This, in addition to the reflected noise off the concrete retaining
walls of the road ramps, the increased noise of trucks grinding up the hill towards the
facility and the reverberations off the underside of the road bridge, created a hostile
environment. The problem was alleviated, firstly by constructing large earth berms on both
sides of the road which reduced the noise substantially and, secondly, by placing
facilities such as the convenience shop and the toilets under the bridge deck, protected
by additional concrete filled walls, on the highway side, of an 800 mm thickness. Aside
from mitigating highway noise, these walls serve to stop an out-of-control vehicle
crashing through into the pedestrian zones.
The highway
noise in the overhead restaurant is eliminated by means of a thick floor slab, walls of
11, 5 mm thick laminated glass and heavy brickwork on the northern side of the building,
which is level with the traffic intersection on the bridge. One of the reasons, Pretorius
mentioned, that the restaurant was on a separate structure was that in similar designs
overseas, where the restaurant deck was continuous with the road bridge, structural
vibration from the traffic carried through into the restaurant and was found to be
severely disruptive.
Speaking
about aesthetics, Pretorius commented that the ‘neutral design’ of the
restaurant building, with its black tinted glass to eliminate the harsh glare from the
highway, would not date and was maintenance free. He added that its night-time appearance
was far more eye-catching, in keeping with the promotional requirements of Caltex. He said
that there had always been a compromise between the oil company’s requirements and
architectural detailing. At night, the slender deck above the service stations seems to
float above the highway because of the high level of lighting reflected off the steel
cladding on the underside of the deck.
Pretorius
commented on the vital importance of good lighting and said that the brightly lit service
stations and predominantly glazed convenience stores, in close proximity to the well-lit
ATM facilities and the glassed in enclosures of the escalators to the restaurant deck, all
served as strong draw-cards for people at night. When questioned about the dominant
signage, he said that the primary signage was very important because it encouraged the
motorist to leave the freeway, initially, to fill up with petrol. He said that, secondly,
the convenience store had been raised to a higher level in the forecourt so that it could
be clearly seen over the roofs of cars and that, thirdly, the escalators in their
transparent boxes would encourage the motorist to make the decision to utilise the
restaurant. He said that an additional reason for the towering signage was that the
noise-reducing berms blocked visual contact, except for a brief glimpse through a
specially positioned valley, with the service stations. Visual contact with their petrol
pumps is normally a strong requirement of the oil company at such a facility - so this was
another compromise.
Pretorius
explained that the fuel reticulation system used at the Star Stop’s service stations
was a sophisticated one with a high degree of safety built into it and that Caltex had
employed consultants from the States to install sate-of-the-art technology. To preclude
the possibility of a fuel spill at pump level, the pumps have built-in shear valves which
close off if the pump is ripped out of the paving by a careless motorist. The battery of
tanks under the petrol pumps are individually coated with fibreglass, in keeping with the
latest technology, to eliminate erosion.
Asked to
comment on the planting, John Drummond said that the client had specified evergreen
species for the berms and that he had chosen mass plantings of star jasmine and ivy
because he knew that they had excellent soil binding properties, particularly for the
stabilisation of the steep road embankments. He said that he had recommended a natural,
biodegradable geotextile to provide support until the roots had become established in the
soil and that this had been used on certain vulnerable areas, only. He also expressed
disappointment that the recommended upgrade proposal that palisade fencing should be used
instead of wire fencing had been turned down because of a budget cut-back. He commented
that it was essential to keep the planting theme simple to avoid visual confusion, in such
close proximity to fast-moving traffic.
Drummond’s
final comment was that he felt the rest-stop could have served the people of Midrand
better, if pedestrians from the town had had access to the site and to the other side of
the highway by means of a pedestrian bridge. Pretorius commented that existing regulations
would not have allowed the inclusion of a strong pedestrian element onto such a site,
because of the dangers of a vehicle dominated environment.
Caltex Star Stop
Co-ordinator/Developer: Petroleum and Retail Properties (Midrand) (Pty) Ltd
Project managers and project architects: Winterbach Pretorius White Inc
Quantity surveyors: Farrow Laing Ntene (in association with) Chris Chalmers Consultants
Civil, structural and electrical engineers: Keeve Steyn Inc
Mechanical engineers: Van Zyl and De Villiers
Landscape architects: John Drummond Landscape Architects
Main contractor: Bird Construction (Pty) Ltd
Project financed by: Rand Merchant Bank |
