BASELINE GEOHYDROLOGY FOR THE DAVEL TO … Rail Link/Davel to Nerston... · DAVEL TO NERSTON SECTION, MPUMALANGA, SOUTH AFRICA ... Project Title: Baseline Geohydrology for the Davel

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

AURECON Doc. No: 109578-DA-NE-2013 Page i

Davel-Nerston Geohydrological Desk Study November 2013

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

AURECON Doc. No: 109578-DA-NE-2013 Page ii


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

AURECON Doc. No: 109578-DAV-2013 Page iii


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)

AURECON Doc. No: 109578-DAV-2013 Page iv


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


No of BH with SWL 182 No of BH with Yields 7





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.

AURECON Doc. No: 109578-DAV-2013 Page v


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


TRANSPORT




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.

AURECON Doc. No: 109578-DA-NE-2013 Page 1


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)



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)



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



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.



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



No of BH with SWL data 154 No of BH with Yield Data 24





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.



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.



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.



No of BH with SWL 182 No of BH with Yields 7





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.



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



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.



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



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.


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


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




Short-term

Site-specific


G3

Incorrect disposal of hazardous and non-hazardous materials or waste could contaminate groundwater.

Long-term




Short-term

Site-specific


Table 10: Impact assessment for the operational phase of the proposed Davel to Nerston Section.

Code Impact

Pre-mitigation: Post-mitigation:


Proba-bility

Signifi-cance


Proba-bility

Signifi-cance

GO1 Contaminated ballast stone may lead to contamination of groundwater.

Long-term




Short-term

Site-specific


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


GO3

Windblown hazardous material emanating from uncovered rail trucks may result in contamination of groundwater.

Long-term

Regional Moderate - negative

Highly detrimental


Short-term

Site-specific


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


AURECON Doc. No: 109578-DA-NE-2013 Page 13 Page 13


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.


TRANSPORT





TRANSPORT




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.

AURECON Doc. No: 109578-DA-NE-2013 Page 14 Page 14


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


.

AURECON Doc. No: 109578-DA-NE-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


Project nr: 109578

LEGEND

Pv: Vryheid Formation (Sandstone, Shale, Coal)

Jd: Jurassic Age Dolerite

Pv

Jd


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


Project nr: 109578

LEGEND

Borehole


Existing Rail Route

Proposed Rail Route

Project Title:

Map Title:

Davel-Nerston Route: Portion 2 - NGA Borehole Locations

Map Number:

Map 4


Project nr: 109578

LEGEND

Borehole


Existing Rail Route

Proposed Rail Route

Alternative Route 4

Alternative Route 4A

Documents

BASELINE GEOHYDROLOGY FOR THE DAVEL TO … Rail Link/Davel to Nerston... · DAVEL TO NERSTON SECTION, MPUMALANGA, SOUTH AFRICA ... Project Title: Baseline Geohydrology for the Davel