baseline geohydrology for the davel to … rail link/davel to nerston... · davel to nerston...
TRANSCRIPT
TRANSNET
ENVIRONMENTAL IMPACT ASSESSMENT FOR THE CONSTRUCTION OF THE
TRANSNET – SWAZI RAIL LINK
BASELINE GEOHYDROLOGY
FOR THE
DAVEL TO NERSTON SECTION, MPUMALANGA, SOUTH
AFRICA
NOVEMBER 2013
DOCUMENT NUMBER
109578 DA-NE 2013
Compiled by
Project Title: Baseline Geohydrology for the Davel to Nerston Section, Mpumalanga, South Africa
Location: Mpumalanga, South Africa
Prepared for: Aurecon Environmental Unit (EAD)
Contact person: Dr Pieter Botha
Tel No: 012 427 2529
Compiled by: Aurecon
Lynnwood Bridge Office Park
4 Daventry Street
Lynwood Manor
0081
Contact Person: Louis Stroebel
Tel No: 012 427 3151
Project team: L Stroebel Geohydrologist
M Terblanche Geotechnician
Signed on behalf of Aurecon:
L Stroebel
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TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................................................................. III
1 INTRODUCTION ....................................................................................................................................... 1
2 METHODOLOGY ...................................................................................................................................... 1
2.1 RECONNAISSANCE TRIP & DESK STUDY .................................................................................................... 1
2.2 REPORTING ............................................................................................................................................. 1
3 AVAILABLE INFORMATION .................................................................................................................... 1
4 DESCRIPTION OF THE ROUTE .............................................................................................................. 2
5 PORTION 1 – 0 TO 67KM ......................................................................................................................... 2
5.1 PHYSIOGRAPHY ....................................................................................................................................... 2 5.1.1 Site Location ...................................................................................................................................... 2
5.1.2 Topography, Drainage and Climate ................................................................................................ 2 5.1.3 Geology & Geohydrology ................................................................................................................. 2
5.2 GROUNDWATER USE ................................................................................................................................ 4 5.3 BOREHOLE YIELDS & GROUNDWATER LEVELS ........................................................................................... 5 5.4 GROUNDWATER CHEMISTRY ..................................................................................................................... 5
6 PORTION 2 – 67 TO 160KM ..................................................................................................................... 6
6.1 PHYSIOGRAPHY ....................................................................................................................................... 6 6.1.1 Site Location ...................................................................................................................................... 6
6.1.2 Topography, Drainage and Climate ................................................................................................ 6 6.1.3 Geology & Geohydrology ................................................................................................................. 6
6.2 GROUNDWATER USE ................................................................................................................................ 6 6.3 BOREHOLE YIELDS & GROUNDWATER LEVELS ........................................................................................... 7
6.4 GROUNDWATER QUALITY ......................................................................................................................... 7
7 IMPACT ASSESSMENT ........................................................................................................................... 8
7.1 IMPACT ACTIVITY CHECKLIST .................................................................................................................... 8 7.2 SUBJECTIVITY IN ASSIGNING SIGNIFICANCE ............................................................................................. 10 7.3 CONSIDERATION OF CUMULATIVE IMPACTS ............................................................................................. 11 7.4 IMPACT ASSESSMENT ............................................................................................................................. 12
8 RECOMMENDATIONS & GROUNDWATER MANAGEMENT FRAMEWORK .................................... 13
9 CONCLUSION ......................................................................................................................................... 14
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LIST OF TABLES
Table 1: Description of the Hydrogeological units underlying the Davel – Nerston section. ............................. 2
Table 2: Statistical information of borehole data extracted from the NGA for Portion 1 ................................... 5
Table 3: Statistical information of borehole data extracted from the NGA for Portion 2. .................................. 7
Table 4. Criteria for the evaluation of environmental impacts. ......................................................................... 8
Table 5. Definition of significance ratings ......................................................................................................... 9
Table 6. Definition of probability ratings ........................................................................................................... 9
Table 7. Definition of confidence ratings ........................................................................................................ 10
Table 8. Definition of reversibility ratings ........................................................................................................ 10
Table 9: Impact assessment for the construction phase of the proposed Davel to Nerston Section. ............. 12
Table 10: Impact assessment for the operational phase of the proposed Davel to Nerston Section. ............ 12
LIST OF FIGURES
Figure 1. Conceptualisation of product migration routes ................................................................................. 13
LIST OF APPENDICES
Appendix A: Maps
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EXECUTIVE SUMMARY
Transnet appointed Aurecon to perform an Environmental Impact Assessment (EIA) for the
proposed Swaziland Rail Link Project. The project has been broken down into different work
packages and this report will focus on the section stretching from Davel to Nerston on the
Mpumalanga/Swaziland border.
As part of the EIA for the proposed Transnet-Swazi Rail Link, a geohydrological desk study for this
portion was required. This document outlines the approach and methodology to describe the
baseline conditions in order to quantify potential impacts, and ultimately develop a groundwater
management framework to mitigate identified potential impacts.
The tasks consisted of the following:
1. Reconnaissance Trip & Desk study of existing and published information,
2. Reporting.
For the purpose of this study, the Davel to Nerston section of the Transnet Swazi Rail Link is
divided into two sections according to the geohydrological boundaries as described in the 1:
500 000 Hydrogeological Maps & accompanied explanation booklet by Barnard (2000) underlying
the route. Portion 1 is located between the 0 to 67km chainages of the route, while Portion 2 is
located between the 67 and 160km chainages. The physical attributes hereof are described in the
table below.
Chainage (km) Hydrogeological
Unit1
Geological Description Aquifer
Description
Potential
Yield (l/s)
0 – 67 (Portion 1) D2 Sandstone &
Conglomerate
Fractured and
Intergranular
0.1 – 0.5
67 – 160; Alternative
Routes 4 and 4A
(Portion 2)
D3 Sandstone, Conglomerate
& Various Granitoids
Fractured and
Intergranular
0.5 – 2.0
Apart from the published 1:500 000 Hydrogeological Maps, a search of the National Groundwater
Archive (NGA) for borehole information within the project area was conducted to characterise the
geohydrological environment. A total of 212 boreholes were recorded in the region of Portion 1 of
the Rail Link, while 231 boreholes were recorded in the region of Portion 2. A summary of the
statistical analysis is presented in the 2 tables below.
For Portion 1 the mean groundwater level and yield for the data collected from the NGA
corresponds with the figures provided by Barnard (2000) and the Hydrogeological Maps.
For Portion 2 the average and mean yield as calculated from the NGA data is significantly less
than described by Barnard. Only a small number of boreholes (7) had yields recorded on the NGA
data base and this figure can thus not be regarded as representative of the geological unit. With
1 According to the 1:500 000 Hydrogeological Map (2526 Johannesburg & 2530 Nelspruit)
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regards to groundwater level data, it can be concluded that the average static water for Portion 2 is
11.68 mbgl. This corresponds with the data published by Barnard (2000).
Portion 1 (0-67km): NGA Data
Borehole Static Water Level (SWL) Data Borehole Yield Data
No of BH with SWL data 154 No of BH with Yield Data 24
Average SWL 13.10 Average yield 0.99
Mean SWL 10.82 Mean yield 0.48
Max SWL 45.72 Max yield 5.3
Min SWL 0.07 Min Yield 0.01
Portion 2 (67-160km; Alternative Routes 4 and 4A): NGA Data
Borehole Static Water Level (SWL) Data Borehole Yield Data
No of BH with SWL 182 No of BH with Yields 7
Average SWL 11.68 Average yield 0.14
Mean SWL 9.14 Mean yield 0.08
Max SWL 60.96 Max yield 0.36
Min SWL 1.07 Min Yield 0.01
Since the majority of Portion 1 & 2 of the Davel-Nerston section of the rail link is located in the rural
areas of Mpumalanga, groundwater is mainly used for domestic purposes and stock watering. The
majority of users make use of boreholes for their water requirements.
The natural groundwater quality in both portions is generally good and fit for human consumption.
RECOMMENDATIONS & GROUNDWATER MANAGEMENT FRAMEWORK
Fuel Storage Tanks used during construction should be installed according to the relevant
SABS standards, for example SABS 089, 1535, 0131, 0108 and 0400. These standards
make provision for observation wells, leak detectors, overfill protectors, etc.
The construction of the workshops, cleaning bays and fuel dispensing areas of the
construction camps should be in such a way that no accidental spillages leave the site and
surface and storm water run-off be diverted through an oil/water separator before leaving
the site.
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Emergency Spill Response Procedures should be in place with capable people with the
necessary training available at strategic locations to follow these procedures in the case of
major accidents and/or accidental spillages.
Should contamination of the soil/groundwater be suspected at any given point in time within
the proposed rail alignment, a detailed site and consequent risk assessment is proposed.
The purpose hereof would be to establish the risk that the contaminated soils and
groundwater pose to the receiving environment using the Risk Based Corrective Action
(RBCA) approach. The Risk Based Corrective Action (RBCA) process represents a
streamlined approach for the assessment and response to subsurface contamination. It
integrates risk assessment practices with traditional site investigation and remedy selection
activities in order to determine cost-effective measures for the protection of human health
and environmental resources. Under this integrated approach, contaminated sites are
characterised in terms of sources, transport pathways, and receptors. Appropriate
remedial measures, based on the outcome of the risk assessment, can then be designed
and implemented at the site under investigation. These risk-based corrective actions can
address any of the steps in the exposure process, including but not limited to the following:
Removing or treating the source,
Interrupting contaminant transport mechanisms, or
Controlling activities at the point of exposure.
SOURCESpill materials and affected media
TRANSPORT
Air, soil, groundwater or
surface water migration
RECEPTORHuman or ecological point of exposure
SOURCESpill materials and affected media
TRANSPORT
Air, soil, groundwater or
surface water migration
RECEPTORHuman or ecological point of exposure
Conceptualisation of product migration routes
As part of the exposure assessment, all potential exposure pathways and receptors have to
be identified. This needs to be done through the conceptualisation of the migration routes
at the site. Thereafter risks can be calculated using commercially available software such
as British Petroleum’s (BP) Risk-Integrated Software for Clean-ups (RISC) or the RBCA
Tier 1 Risk Based Screening Levels (RBSL) spreadsheets. It must be stated that the risk
profile is dependent on the current land use (mainly agricultural). Should the land use
change in future to e.g. residential, the risk profile and consequent remedial actions could
change.
CONCLUSION
Based on the reconnaissance visit and desk study, the construction and operation of the proposed
Davel-Nerston section of the rail link, will have a “very low” impact on the investigated
geohydrological environment, given that sound environmental infrastructure and management
procedures are put in place. During the rating and ranking procedure of impacts, all identified
impacts could be countered by appropriate mitigation.
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1 INTRODUCTION
Transnet appointed Aurecon to perform an Environmental Impact Assessment (EIA) for the
proposed Swaziland Rail Link project. The project has been broken down into different work
packages and this report will focus on the section stretching from Davel to Nerston on the
Mpumalanga/Swaziland border.
As part of the EIA for the proposed Transnet-Swazi Rail Link, a geohydrological desk study for this
portion was required. This document outlines the approach and methodology to describe the
baseline conditions in order to quantify potential impacts, and ultimately develop a groundwater
management framework to mitigate identified potential impacts.
The tasks consisted of the following:
1. Reconnaissance Trip & Desk study,
2. Reporting.
2 METHODOLOGY
The work completed for the purposes of compiling a geohydrological report comprised the
following:
2.1 Reconnaissance Trip & Desk Study
A reconnaissance trip of the proposed route was conducted during July 2013. This assisted in
familiarising ourselves with the site conditions and project objectives. During the desk study, all
existing data from the client and published data was collected, collated and studied. Aerial photos,
geological and geohydrological maps formed the basis for the study. Geohydrological data was
also downloaded from the Department of Water Affairs’ National Groundwater Archive.
2.2 Reporting
Upon completion of the desk study, a document was compiled summarising the geohydrological
conditions along the route. This document also contained an impact assessment.
3 AVAILABLE INFORMATION
The following information was available and relevant to the study:
1:250 000 Geological Map (2628 East Rand).
1:250 000 Geological Map (2630 Mbabane)
1:500 000 Hydrogeological Map (2526 Johannesburg).
1:500 000 Hydrogeological Map (2530 Nelspruit).
An explanation of the 1:500 000 Hydrogeological Map, Johannesburg 2526 (2000) Barnard.
Investigation into Groundwater Quality Deterioration in the Olifants River Catchment above
the Loskop Dam with specialised investigation in the Witbank Dam-Sub Catchment (1998).
F.D.I Hodgson & R.M. Krantz. WRC Report No. 291/1/98.
National Groundwater Archive (Department of Water Affairs)
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4 DESCRIPTION OF THE ROUTE
For the purpose of this study, the Davel to Nerston section of the Transnet Swazi Rail Link is
divided into two sections according to the geohydrological boundaries as described in the 1:
500 000 Hydrogeological Maps underlying the route. Portion 1 is located between the 0 to 67km
chainages of the route, while portion 2 is located between the 67 and 160km chainages. The
physical attributes hereof are described in Table 1 below according to this arrangement.
Table 1: Description of the Hydrogeological units underlying the Davel – Nerston section.
Chainage (km) Hydrogeological
Unit2
Geological Description Aquifer
Description
Potential
Yield (l/s)
0 – 67 (Portion 1) D2 Sandstone &
Conglomerate
Fractured and
Intergranular
0.1 – 0.5
67 – 160; Alternative
Routes 4 and 4A
(Portion 2)
D3 Sandstone, Conglomerate
& Various Granitoids
Fractured and
Intergranular
0.5 – 2.0
5 PORTION 1 – 0 TO 67KM
5.1 Physiography
5.1.1 Site Location
Portion 1 of the route alignment is located between the 0 to 67km chainages of the route
alignment. Portion 1 starts at the rail yard in the town of Davel, Mpumalanga, and is terminated on
the geohydrological boundary between the D2 and D3 aquifer types as indicated on the 1:500 000
geohydrological map (2526 Johannesburg) (Map 1, Appendix A). The adjacent land-use mainly
comprises of farms where agricultural activities are practised.
5.1.2 Topography, Drainage and Climate
The topography of Portion 1 is characterized by flat and slightly undulating pastures of the Eastern
Highveld of Mpumalanga. The elevation increases from 1715 mamsl at Davel to 1738 mamsl at km
67 along the rail route. The vegetation is described as Highveld Grassland and this portion falls
within the Olifants River and Vaal River catchments.
The climate is described as being a temperate climate with warm to hot summers (October to
March) with moderately cold winters. Rainfall mostly consists of afternoon thunder showers with an
annual average rainfall figure of 739 mm/a.
Portion 1 intersects five quaternary catchments (C11F, C11A, B11A, B12A, X11A). The average
annual groundwater recharge to these five catchments is 42.8mm/a.
5.1.3 Geology & Geohydrology
Based on the 1:250 000 geological maps (2628 East Rand and 2630 Mbabane) Portion 1 of the
Davel-Nerston section of the rail link is underlain by Palaeozoic Ecca Group geology. The Ecca
Group geology underlying the project area consists of arenaceous rocks of the Vryheid Formation.
2 According to the 1:500 000 Hydrogeological Map (2526 Johannesburg & 2530 Nelspruit)
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The deposition of the Vryheid Formation sediments is largely controlled by the irregular pre-Karoo
platform on which they were deposited. The pre-Karoo rocks, consisting mainly of felsites of the
Bushveld Igneous Complex, have been glacially sculptured to give rise to uneven basement
topography. The thin veneer sediments of the Dwyka Formation, which overlies the pre-Karoo, are
generally not thick enough to ameliorate the irregularities in the placated surface, which therefore
affected the deposition of the younger Vryheid Formation sediments.
The Ecca sediments consist predominantly of sandstone, siltstone, shale and coal. Combinations
of these rock types are found in the form of interbedded siltstone, mudstone and coarse grained
sandstone.
Dolerite/Diabase intrusions in the form of dykes and sills are present within the Ecca Group. The
sills usually precede the dykes, with the latter being emplaced during a later period of tensional
forces within the earth’s crust. Tectonically, the Karoo sediments are practically undisturbed.
Faults are rare. However, fractures are common in competent rocks such as sandstone and coal.
The groundwater rest level is generally encountered between 5 and 25m below surface.
According to Hodgson et al. (1998), three distinct superimposed groundwater systems are present
within the occurring geology. They can be classified as the upper weathered Ecca aquifer, the
fractured aquifers within the unweathered Ecca sediments and the aquifer below the Ecca
sediments.
5.1.3.1 Ecca Weathered Aquifer
The Ecca sediments are weathered to depths between 5 – 12 meters below surface and often form
a perched aquifer. This aquifer is recharged by rainfall and estimated to be between 1-3 % of the
annual rainfall. Rainfall that infiltrates into the weathered rock soon reaches an impermeable layer
of shale underneath the weathered zone. The movement of groundwater on top of this shale is
lateral and in the direction of the surface slope. The water discharges at surface in the forms of
fountains and springs where the flow paths are obstructed by a barrier, such as a dolerite dyke,
paleo-topographic highs in the bedrock, or where the surface topography cuts below the
groundwater table at streams. It is suggested that less than 60% of the water recharged to the
weathered zone eventually emanates in streams while the remaining water is evapotranspirated or
drained by some other means.
This aquifer is generally low-yielding (100 – 2000 ℓ//h) because of its insignificant thickness. Wells
or trenches dug into this aquifer are often sufficient to secure a constant water supply of excellent
quality. The excellent water quality can be attributed to the many years of dynamic groundwater
flow through the weathered sediments. Leachable salts have been dissolved and it is the only the
slow decomposition of clay particles which presently releases salts into the water.
5.1.3.2 Fractured Ecca Aquifer
The pores within the Ecca sediments are too well cemented to allow any significant permeation of
water. Groundwater movement is therefore along secondary structures, such as fractures, cracks
and joints in the sediments. These structures are better developed in competent rocks such as
sandstone, hence the better water yielding properties of the latter rock type. It should, however, be
emphasised that not all secondary structures are water bearing. Many of these structures are
constricted because of compressional forces that act within the earth’s crust. The chances of
intersecting a water-bearing fracture by drilling decreases rapidly with depth. At depths deeper
than 30 m, water-bearing fractures with significant yield were observed to be spaced at 100 m or
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greater. Scientific siting of production boreholes is necessary to intersect these fractures. The
mean yield of this aquifer is ~1250 ℓ//h.
In terms of water quality, the fractured Ecca aquifer always contains higher salt loads than the
upper weathered aquifer. Although the sulphate, magnesium and calcium concentrations in the
Ecca fractured aquifer are higher than that in the weathered zone, they are well within expected
limits. The higher concentrations can be attributed to the longer exposure time of the water to the
rock. The occasional elevated chloride and sodium levels can be attributed to boreholes in the
vicinity of areas where salts naturally accumulate on surface, such as pans and some of the
fountains.
5.1.3.3 Pre-Karoo Aquifer
Drilling in only a few instances has intersected the basement of the Karoo Supergroup which can
be regarded as an insignificant aquifer due to:
The great depth,
Low yielding fractures,
Inferior water quality with elevated concentrations of fluoride associated with the granitic
rocks,
Low recharge characteristics of this aquifer because of the overlying impermeable Dwyka
tillite.
5.2 Groundwater Use
Since the majority of Portion 1 of the Davel-Nerston section of the rail link is located in the rural
areas of Mpumalanga, groundwater is mainly used for domestic purposes and stock watering. The
majority of users make use of boreholes for their water requirements.
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5.3 Borehole Yields & Groundwater levels
According to Barnard (2000), the groundwater yield potential is classed as low since 83% of
boreholes on record produce less than 2 l/s, while the groundwater rest level is generally
encountered between 5 and 25m below surface.
A search of the National Groundwater Archive (NGA) revealed that 212 boreholes were recorded
in the region of Portion 1 of the Rail Link. Mainly water level and yield data exists with very little
chemistry data. The borehole positions are plotted on Map 3 in Appendix A and the statistics in
terms of yield and water level is presented in Table 2.
Table 2: Statistical information of borehole data extracted from the NGA for Portion 1
Portion 1 (0-67km): NGA Data
Borehole Static Water Level (SWL) Data Borehole Yield Data
No of BH with SWL data 154 No of BH with Yield Data 24
Average SWL 13.10 Average yield 0.99
Mean SWL 10.82 Mean yield 0.48
Max SWL 45.72 Max yield 5.3
Min SWL 0.07 Min Yield 0.01
From Table 2 it can be concluded that the mean groundwater level and yield for the data collected
from the NGA corresponds with the figures provided by Barnard (2000).
5.4 Groundwater Chemistry
According to Barnard (2000), the general suitability of the groundwater for any use is indicated by
the average EC value of 57 mS/m and a mean pH value of 7.5. Due to a lack of chemistry data on
the NGA, this could not been confirmed.
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6 PORTION 2 – 67 TO 160KM; ALTERNATIVE ROUTES 4 AND 4A
6.1 Physiography
6.1.1 Site Location
Portion 2 of the route alignment is located between the 67km to 160km chainages of the Davel-
Nerston route alignment. Portion 2 starts at the geohydrological boundary between the D2 and D3
aquifer types as indicated on the 1:500 000 geohydrological map (2526 Johannesburg) (Map 1,
Appendix A) and terminates at the Nerston border post between South Africa and Swaziland. The
adjacent land-use mainly comprises of farms where agricultural activities are practised.
6.1.2 Topography, Drainage and Climate
The topography of Portion 2 is characterized by flat and slightly undulating pastures of the eastern
Highveld of Mpumalanga. The elevation decreases from 1741 mamsl (km67) to 1419 mamsl
(Nerston) along the rail route.
The vegetation is described as Sandy Highveld Grassland in the km67 area grading into North
East Mountain Grassland in the Nerston area. This portion falls within the Vaal River and Usutu
River catchments.
The climate is described as being a temperate climate with warm to hot summers (October to
March) and moderately cold winters. Rainfall mostly consists of afternoon thunder showers with an
annual rainfall figure of 866 mm/a.
Portion 2 intersects six quaternary catchments (C11A, W55A, W54A, W54B, W54D, W54E). The
average annual recharge to groundwater to these five catchments is 64.61mm/a.
6.1.3 Geology & Geohydrology
According to the 1:250 000 Geology maps (2628 East Rand and 2630 Mbabane), Portion 2 is
underlain by the Vryheid Formation of the Ecca Group (Kalahari Supergroup) (67km – 123km), as
well as the Mozaan Group geology (123km – 160km).
For a detailed description of the geology and geohydrology of the Vryheid formation, refer to
paragraph 5.1.3.
The Mozaan Group consists of mainly crystalline basement rocks of Randian Age. The rocks
consist of leucocratic potassic granite, tonalite, leucocratic biotite granite as well as gabbro, quartz
gabbro, ferrogabbro with magnetite lenses and hyperite.
According to Barnard (2000), groundwater occurrence in these mainly granitic rocks is generally
associated with zones of weathering, brecciation and jointing. Groundwater is often encountered in
both the saturated weathered material below the regional groundwater rest level and in the
transition zone between weathered and fresh granite. The basins of weathering normally coincide
with the drainage pattern. The majority of fault and joint zones are steeply dipping structures that
tend to narrow and even pinch out at depth with a corresponding decrease in permeability. The
porosity is usually less than 1%, while fresh rock may be regarded as impermeable.
6.2 Groundwater Use
Since the majority of the Davel – Nerston section of the rail link is located in the rural areas of
Mpumalanga, groundwater is mainly used for domestic purposes and stock watering. The majority
of users make use of boreholes for their water requirements.
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6.3 Borehole Yields & Groundwater Levels
According to Barnard (2000), the groundwater yield potential of the basement complex igneous
rocks is classed as good on the basis that 62% of the boreholes on record produce more than 2
l/s. High yielding boreholes appear to be associated with the weathering of granites, contacts
between geological units and in fault or fracture zones. Therefore extensive geophysics is
required to site such a borehole. When fracture zones and faults are however intercepted, high
borehole yields can be expected as well as springs where dyke contacts outcrop.
The depth to groundwater rest level is generally between 5 and 30m below surface (Barnard).
A search of the National Groundwater Archive (NGA) revealed that 231 boreholes were recorded
in the region of Portion 2 of the Rail Link. Mainly water level and yield data exists with very little
chemistry data (Table 3).
Table 3: Statistical information of borehole data extracted from the NGA for Portion 2.
Portion 2 (67-160km): NGA Data
Borehole Static Water Level (SWL) Data Borehole Yield Data
No of BH with SWL 182 No of BH with Yields 7
Average SWL 11.68 Average yield 0.14
Mean SWL 9.14 Mean yield 0.08
Max SWL 60.96 Max yield 0.36
Min SWL 1.07 Min Yield 0.01
From Table 3 it can be seen that the average and mean yield as calculated from the NGA data is
significantly less than described by Barnard. Only a small number of boreholes (7) had yields
recorded on the NGA data base and this figure can thus not be regarded as representative of the
geological unit.
With regards to groundwater level data, it can be concluded that the average static water for
Portion 2 is 11.68 mbgl. This corresponds with the data published by Barnard (2000).
6.4 Groundwater Quality
According to Barnard (2000), the general suitability of the groundwater in the basement complex
geology for any use is indicated by the average EC value of 38 mS/m and a mean pH value of 7.5.
Due to a lack of chemistry data on the NGA, this could not been confirmed.
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7 IMPACT ASSESSMENT
7.1 Impact Activity Checklist
This section outlines the methodology used to assess the significance of the potential
geohydrological impacts identified. For each impact, the EXTENT (spatial scale), MAGNITUDE
(size or degree scale) and DURATION (time scale) are described (Table 4). These criteria are
used to ascertain the SIGNIFICANCE of the impact, firstly in the case of no mitigation and then
with the most effective mitigation measure(s) in place. The mitigation described in the EIR
represent the full range of plausible and pragmatic measures but does not necessarily imply that
they should or will all be implemented. The decision as to which mitigation measures to implement
lies with Transnet and ultimately with the DEA. The tables on the following pages show the scale
used to assess these variables, and defines each of the rating categories.
Table 4. Criteria for the evaluation of environmental impacts.
CRITERIA CATEGORY DESCRIPTION
Extent or spatial
influence of
impact
Regional Beyond a 10 km radius of the proposed construction site
Local Within a 10 km radius of the centre of the proposed construction site
Site specific On site or within 100 m of the proposed construction site
Magnitude of
impact (at the
indicated spatial
scale)
High Natural and/ or social functions and/ or processes are severely altered
Medium Natural and/ or social functions and/ or processes are notably altered
Low Natural and/ or social functions and/ or processes are slightly altered
Very Low Natural and/ or social functions and/ or processes are negligibly altered
Zero Natural and/ or social functions and/ or processes remain unaltered
Duration of
impact
Construction
period Up to 2 years
Medium Term Up to 5 years after construction
Long Term More than 5 years after construction
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Davel-Nerston Geohydrological Desk Study November 2013
The SIGNIFICANCE of an impact is derived by taking into account the temporal and spatial scales
and magnitude. The means of arriving at the different significance ratings is explained in Table 5.
Table 5. Definition of significance ratings
SIGNIFICANCE
RATINGS LEVEL OF CRITERIA REQUIRED
High High magnitude with a regional extent and long term duration
High magnitude with either a regional extent and medium term duration or a local extent
and long term duration Medium magnitude with a regional extent and long term duration
Medium High magnitude with a local extent and medium term duration
High magnitude with a regional extent and construction period or a site specific extent
and long term duration
High magnitude with either a local extent and construction period duration or a site
specific extent and medium term duration
Medium magnitude with any combination of extent and duration except site specific and
construction period or regional and long term Low magnitude with a regional extent and long term duration
Low High magnitude with a site specific extent and construction period duration
Medium magnitude with a site specific extent and construction period duration
Low magnitude with any combination of extent and duration except site specific and
construction period or regional and long term
Very low magnitude with a regional extent and long term duration
Very low Low magnitude with a site specific extent and construction period duration
Very low magnitude with any combination of extent and duration except regional and
long term
Neutral Zero magnitude with any combination of extent and duration
Once the significance of an impact has been determined, the PROBABILITY of this impact
occurring as well as the CONFIDENCE in the assessment of the impact would be determined
using the rating systems outlined in Table 6 and Table 7 respectively. It is important to note that
the significance of an impact should always be considered in connection with the probability of that
impact occurring. Lastly, the REVERSIBILITY of the impact is estimated using the rating system
outlined in Table 8.
Table 6. Definition of probability ratings
PROBABILITY
RATINGS CRITERIA
Definite Estimated greater than 95 % chance of the impact occurring.
Probable Estimated 5 to 95 % chance of the impact occurring.
Unlikely Estimated less than 5 % chance of the impact occurring.
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Davel-Nerston Geohydrological Desk Study November 2013
Table 7. Definition of confidence ratings
CONFIDENCE
RATINGS CRITERIA
Certain Wealth of information on and sound understanding of the environmental factors potentially
influencing the impact.
Sure Reasonable amount of useful information on and relatively sound understanding of the
environmental factors potentially influencing the impact.
Unsure Limited useful information on and understanding of the environmental factors potentially
influencing this impact.
Table 8. Definition of reversibility ratings
REVERSIBILITY
RATINGS CRITERIA
Irreversible The activity will lead to an impact that is permanent.
Reversible The impact is reversible, within a period of 10 years.
7.2 Subjectivity in Assigning Significance
Despite attempts at providing a completely objective and impartial assessment of the
environmental implications of development activities, EIA processes can never escape the
subjectivity inherent in attempting to define significance. The determination of the significance of
an impact depends on both the context (spatial scale and temporal duration) and intensity of that
impact. Since the rationalisation of context and intensity will ultimately be prejudiced by the
observer, there can be no wholly objective measure by which to judge the components of
significance, let alone how they are integrated into a single comparable measure.
This notwithstanding, in order to facilitate informed decision-making, EIAs must endeavour to come
to terms with the significance of the potential environmental impacts associated with particular
development activities. Recognising this, we have attempted to address potential subjectivity in
the current EIA process as follows:
Being explicit about the difficulty of being completely objective in the determination of
significance, as outlined above;
Developing an explicit methodology for assigning significance to impacts and outlining this
methodology in detail in the PoS for EIA and in this EIR. Having an explicit methodology
not only forces the assessor to come to terms with the various facets contributing towards
the determination of significance, thereby avoiding arbitrary assignment, but also provides
the reader of the EIR with a clear summary of how the assessor derived the assigned
significance;
Wherever possible, differentiating between the likely significance of potential environmental
impacts as experienced by the various affected parties; and
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Utilising a team approach and internal review of the assessment to facilitate a more
rigorous and defendable system.
Although these measures may not totally eliminate subjectivity, they provide an explicit context
within which to review the assessment of impacts.
7.3 Consideration of Cumulative Impacts
Section 2 of the NEMA requires the consideration of cumulative impacts as part of any
environmental assessment process. EIAs have traditionally, however, failed to come to terms with
such impacts, largely as a result of the following considerations:
Cumulative effects may be local, regional or global in scale and dealing with such impacts
requires co-ordinated institutional arrangements; and
EIA’s are typically carried out on specific developments, whereas cumulative impacts result
from broader biophysical, social and economic considerations, which typically cannot be
addressed at the project level.
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Davel-Nerston Geohydrological Desk Study Novemberr 2013
7.4 Impact Assessment
Table 9: Impact assessment for the construction phase of the proposed Davel to Nerston Section.
Code Impact
Pre-mitigation: Post-mitigation:
Duration Extent Intensity Conse-quence
Proba-bility
Signifi-cance
Duration Extent Intensity Conse-quence
Proba-bility
Signifi-cance
G1
Potential hydrocarbon spillages from equipment, machinery and vehicle storage may lead to contamination of groundwater.
Long-term
Regional Very high - negative
Extremely detrimental
Probable Moderate - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
G2
Potential waste leakages/spillages in construction camp may lead to contamination of groundwater.
Long-term
Regional Very high - negative
Extremely detrimental
Probable Moderate - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
G3
Incorrect disposal of hazardous and non-hazardous materials or waste could contaminate groundwater.
Long-term
Regional Very high - negative
Extremely detrimental
Probable Moderate - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
Table 10: Impact assessment for the operational phase of the proposed Davel to Nerston Section.
Code Impact
Pre-mitigation: Post-mitigation:
Duration Extent Intensity Conse-quence
Proba-bility
Signifi-cance
Duration Extent Intensity Conse-quence
Proba-bility
Signifi-cance
GO1 Contaminated ballast stone may lead to contamination of groundwater.
Long-term
Regional Very high - negative
Extremely detrimental
Probable Moderate - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
GO2
Spillages of hazardous materials resulting from accidents or collisions may result in contamination of groundwater.
Medium-term
Local Very high - negative
Highly detrimental
Unlikely Low - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
GO3
Windblown hazardous material emanating from uncovered rail trucks may result in contamination of groundwater.
Long-term
Regional Moderate - negative
Highly detrimental
Probable Moderate - negative
Short-term
Site-specific
Negligible Negligible Unlikely Very low
From the above table it can be seen that the construction and operational phases of the Davel to Nerston section will have a “very low” impact on the
investigated geohydrological environment, given that sound environmental infrastructure and management procedures are put in place. All of the identified
impacts could be countered by appropriate mitigation.
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Davel-Nerston Geohydrological Desk Study November 2013
8 RECOMMENDATIONS & GROUNDWATER MANAGEMENT FRAMEWORK
Fuel Storage Tanks used during construction should be installed according to the relevant
SABS standards, for example SABS 089, 1535, 0131, 0108 and 0400. These standards
make provision for observation wells, leak detectors, overfill protectors, etc.
The construction of the workshops, cleaning bays and fuel dispensing areas of the
construction camps should be in such a way that no accidental spillages leave the site and
surface and storm water run-off be diverted through an oil/water separator before leaving
the site.
Emergency Spill Response Procedures should be in place with capable people with the
necessary training available at strategic locations to follow these procedures in the case of
major accidents and/or accidental spillages.
Should contamination of the soil/groundwater be suspected at any given point in time within
the proposed rail alignment, a detailed site and consequent risk assessment is proposed.
The purpose hereof would be to establish the risk that the contaminated soils and
groundwater pose to the receiving environment using the Risk Based Corrective Action
(RBCA) approach. The Risk Based Corrective Action (RBCA) process represents a
streamlined approach for the assessment and response to subsurface contamination. It
integrates risk assessment practices with traditional site investigation and remedy selection
activities in order to determine cost-effective measures for the protection of human health
and environmental resources. Under this integrated approach, contaminated sites are
characterised in terms of sources, transport pathways, and receptors (Error! Reference
source not found.). Appropriate remedial measures, based on the outcome of the risk
assessment, can then be designed and implemented at the site under investigation. These
risk-based corrective actions can address any of the steps in the exposure process,
including but not limited to the following:
Removing or treating the source,
Interrupting contaminant transport mechanisms, or
Controlling activities at the point of exposure.
SOURCESpill materials and affected media
TRANSPORT
Air, soil, groundwater or
surface water migration
RECEPTORHuman or ecological point of exposure
SOURCESpill materials and affected media
TRANSPORT
Air, soil, groundwater or
surface water migration
RECEPTORHuman or ecological point of exposure
Figure 1. Conceptualisation of product migration routes
As part of the exposure assessment, all potential exposure pathways and receptors have to
be identified. This needs to be done through the conceptualisation of the migration routes
at the site. Thereafter risks can be calculated using commercially available software such
as British Petroleum’s (BP) Risk-Integrated Software for Clean-ups (RISC) or the RBCA
Tier 1 Risk Based Screening Levels (RBSL) spreadsheets. It must be stated that the risk
profile is dependent on the current land use (mainly agricultural). Should the land use
change in future to e.g. residential, the risk profile and consequent remedial actions could
change.
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Davel-Nerston Geohydrological Desk Study November 2013
9 CONCLUSION
Based on the reconnaissance visit and desk study, the construction and operation of the proposed
Davel-Nerston section of the rail link, will have a “very low” impact on the investigated
geohydrological environment, given that sound environmental infrastructure and management
procedures are put in place. During the rating and ranking procedure of impacts, all identified
impacts could be countered by appropriate mitigation.
.
AURECON Doc. No: 109578-DA-NE-2013
Davel-Nerston Geohydrological Desk Study November 2013
APPENDIX A
MAPS
Project Title:
Map Title:
Davel-Nerston Route : Locality Map
Map Number:
Map 1
Lynnwood Bridge Office Park 4 Daventry Street Lynwood Manor 0040 www.aurecongroup.com
Project nr: 109578
LEGEND
TRANSNET SWAZI RAIL LINK EIA: HYDROGEOLOGICAL DESK STUDY FOR THE DAVEL-NERSTON ROUTE
Proposed Davel-Nerston Rail Link
Alternative Route 4
Alternative Route 4A
Project Title:
Map Title:
Davel-Nerston Route: Geological Setting
Map Number:
Map 2
Lynnwood Bridge Office Park 4 Daventry Street Lynwood Manor 0040 www.aurecongroup.com
Project nr: 109578
LEGEND
Pv: Vryheid Formation (Sandstone, Shale, Coal)
Jd: Jurassic Age Dolerite
Pv
Jd
TRANSNET SWAZI RAIL LINK EIA: HYDROGEOLOGICAL DESK STUDY FOR THE DAVEL-NERSTON ROUTE
RPg: Mozaan igneous geology (leucocratic potassic granite)
Rt: Thole Suite (Ultrabasic rocks, norite, pyroxenite)
Project Title:
Map Title:
Davel-Nerston Route: Portion 1 - NGA Borehole Locations
Map Number:
Map 3
Lynnwood Bridge Office Park 4 Daventry Street Lynwood Manor 0040 www.aurecongroup.com
Project nr: 109578
LEGEND
Borehole
TRANSNET SWAZI RAIL LINK EIA: HYDROGEOLOGICAL DESK STUDY FOR THE DAVEL-NERSTON ROUTE
Existing Rail Route
Proposed Rail Route
Project Title:
Map Title:
Davel-Nerston Route: Portion 2 - NGA Borehole Locations
Map Number:
Map 4
Lynnwood Bridge Office Park 4 Daventry Street Lynwood Manor 0040 www.aurecongroup.com
Project nr: 109578
LEGEND
Borehole
TRANSNET SWAZI RAIL LINK EIA: HYDROGEOLOGICAL DESK STUDY FOR THE DAVEL-NERSTON ROUTE
Existing Rail Route
Proposed Rail Route
Alternative Route 4
Alternative Route 4A