groundwater specialist study - cape town international ... specialist study - cape town...

Groundwater Specialist Study - Cape Town International Airport Runway Re-alignment

and Associated Infrastructure Project

REPORT: GEOSS Report No: 2014/06-10

PREPARED FOR:

Sharon Jones and Scott Mason SRK Consulting (South Africa) (Pty) Ltd.

The Administrative Building Albion Spring 183 Main Road

Rondebosch 7700

PREPARED BY: Julian Conrad

GEOSS - Geohydrological and Spatial Solutions International (Pty) Ltd Unit 19, Technostell Building,

9 Quantum Street, TechnoPark

Stellenbosch 7600 Tel: (021) 880-1079

Email: [email protected] (www.geoss.co.za)

08 September 2014

mailto:[email protected]

http://www.geoss.co.za/

Groundwater Specialist Study - Cape Town International Airport Runway Re-alignment and Associated Infrastructure Project

GEOSS Report No. 2014/06-10 08 September 2014 i

EXECUTIVE SUMMARY

The Airports Company South Africa proposes to re-align the existing primary runway at the Cape

Town International Airport. This will allow the runway to be lengthened, which will enable the

airport to accommodate larger aircraft. A new integrated taxiway system will also be built. The

Cape Town International Airport is located on the sandy Cape Flats region, immediately north of

the N2 highway, approximately 20 km east of Cape Town’s Central Business District, in the

Western Cape. SRK Consulting (South Africa) (Pty) Ltd has been appointed to undertake the

Environmental Impact Assessment for the project. GEOSS - Geohydrological & Spatial Solutions

International (Pty) Ltd was appointed to address the geohydrological aspects of the study.

The Western Cape has a semi-arid Mediterranean climate, which is strongly influenced by the cold

Benguela ocean current and coastal winds. The Cape Town area is characterised by dry warm

summer months (October to April) and wet cool winter months (from May to September). The

highest rainfall occurs between the months of May and August. The long-term average annual

rainfall is 569 mm/a for the area. The long-term average annual evaporation is 2 030 mm/a.

With regard to the geological setting, Tertiary to Recent age sedimentary deposits underlie the area,

comprising mainly of calcareous sands of the Sandveld Group which are underlain by rocks of the

Malmesbury Group. The Sandveld Group deposits constitute what is known as the Cape Flats

Aquifer. The Cape Flats Aquifer is classified as an unconfined aquifer. The thickness of the sand

unit at the study area is approximately 25 m and the saturated thickness of the aquifer is

approximately 20 – 25 m. These sands range in grain size from fine to coarse and are generally

well-sorted and well-rounded. These characteristics result in an aquifer transmissivity of

~100 m2/d for the study area. The aquifer is recharged directly principally from rainfall within the

catchment. Groundwater recharge of the primary aquifer varies between 15% and 37% of the

annual precipitation. In the eastern portion of the Cape Flats Aquifer (i.e. within the study area),

shallow calcrete layers cause perched groundwater levels to occur. The groundwater level

(measured as metres below ground level) is variable due to the undulating topography and the

presence of impervious shallow calcrete lenses. During the wet winter months the groundwater

level is very shallow. In the western portion of the study area the groundwater flow direction is

towards the south-west and in the eastern portion of the study area the groundwater flow direction

is towards the south-east.

With regard to groundwater quality zones of saline water do occur at different stratigraphic levels

due to the varied depositional history of the local geological formations. The high evaporation

rates in summer also result in high salinity areas. The regional groundwater quality in the study

area, as indicated by Total Dissolved Solids, is in the range from 500 mg/ℓ to 2 000 mg/ℓ. This

equates to an Electrical Conductivity range of approximately 70 mS/m to 300 mS/m.

Based on existing literature and data the groundwater level can range from 0 metres below ground

level (i.e. at surface) to > 3.5 metres below ground level. However it is important to note that the

groundwater level is generally very shallow in the study area. Wetlands in the area exist due to the

presence of shallow impermeable geological layers. A large proportion of the water augmenting the

wetlands is from shallow groundwater. The groundwater quality is too saline for direct domestic

use, and there is no current or foreseen economic use of groundwater in the study area.

The possible direct impacts of the proposed airport enhancements are as follows:


GEOSS Report No. 2014/06-10 08 September 2014 ii

1. Removal of alien vegetation and associated impact on groundwater levels and groundwater

quality (construction phase).

2. Earthworks required to prepare the area (i.e. cut and fill), removal of existing wetlands and

construction of the runway and taxiways on groundwater levels and quality (construction

phase).

3. Presence of increased impermeable surfaces (i.e. the new runway and taxiways) on

groundwater levels and quality (operational phase).

The significance ratings for the impacts are as follows:

Impact Consequence Probability Significance Status Confidence

Impact 1a (on groundwater levels): Removal of alien vegetation

Medium Probable MEDIUM - ve High

With mitigation Low Possible VERY LOW - ve High

Impact 1b (on groundwater quality): Removal of alien vegetation

Low Probable LOW + ve High

With mitigation Low Probable LOW + ve High

Impact 2a (on groundwater levels):

Earth works Very low Possible INSIGNIFICANT - ve High

With mitigation Very low Improbable INSIGNIFICANT - ve High

Impact 2b (on groundwater quality):

Earth works Very low Possible INSIGNIFICANT - ve High

With mitigation Very low Improbable INSIGNIFICANT - ve High

Impact 3a (on groundwater levels): Presence of runway and taxiways

Very low Definite VERY LOW - ve High

With mitigation Very low Possible VERY LOW - ve High

Impact 3a (on groundwater quality): Presence of runway and taxiways

Very low Definite VERY LOW - ve High

With mitigation Very low Definite VERY LOW - ve High

There are no major cumulative or indirect impacts of the proposed runway and taxiways on the

groundwater of the area.

It is confirmed that groundwater is very shallow beneath the study area and the design engineers are

well aware of this. The shallow, hard, laterally discontinuous and impermeable calcrete (and

sandstone) layers result in perched groundwater levels. This is especially the situation in the wet

winter months. The groundwater levels are particularly shallow at the south-eastern and north-

western ends of the proposed runway. These are the areas where flooding will occur if the

antecedent conditions are favourable and a very high rainfall event occurs. These shallow

geological layers may result in differential compaction of the site.

It is recommended that the preparation of the site (i.e. earthworks) be carried out with the objective

to keep the land surface as high above mean sea level as possible. In addition the runway and

taxiways need to be elevated above this ground surface level. Liaison between the project

geohydrologist and design engineers is essential regarding the optimal surface elevations. Even

though groundwater is not used on site, nor is it intended to be used on site, it is important to

ensure the groundwater is not contaminated during the construction or operational phase. It is not

imperative that groundwater levels and quality be monitored on a long term basis, unless deemed so

by the relevant authorities.

Ooooo OOO ooooO


GEOSS Report No. 2014/06-10 08 September 2014 iii

TABLE OF CONTENTS

1. INTRODUCTION ................................................................................................ 1 1.1 Background ......................................................................................................................... 1

1.2 Terms of Reference (ToR) ................................................................................................ 4

1.2.1 Broader project - Terms of Reference .................................................................................. 4

1.2.2 Groundwater - specific Terms of Reference .......................................................................... 6

1.3 Study area ............................................................................................................................ 6

1.3.1 General ............................................................................................................................ 6

1.3.2 Climate, Rainfall and Evaporation ................................................................................... 7

1.3.3 Regional Geology .............................................................................................................. 7

1.3.4 Regional Hydrogeology ...................................................................................................... 8

1.4 Assumptions and Limitations......................................................................................... 11

1.4.1 Assumptions ................................................................................................................... 11

1.4.2 Limitations..................................................................................................................... 11

2. METHODOLOGY .............................................................................................. 11

3. RELEVANT EXISTING DATA AND DATA AQUIRED FROM FIELD WORK .......................................................................................................................... 13

3.1 Desktop investigation ...................................................................................................... 13

3.1.1 National Groundwater Archive (NGA) ........................................................................ 13

3.1.2 University of the Western Cape (UWC) ......................................................................... 14

3.1.3 Proposed Belhar Housing Development ............................................................................ 15

3.1.4 CSIR (2006) ................................................................................................................. 15

3.1.5 Naco-SSI (2010) ........................................................................................................... 16

3.1.6 Geo Pollution Technologies (GPT, 2014) ....................................................................... 17

3.2 Field assessment ............................................................................................................... 18

4. IMPACT IDENTIFICATION AND ASSESSMENT ........................................ 23 4.1 Direct Impacts .................................................................................................................. 23

4.1.1 Removal of alien vegetation and associated impact on groundwater levels (construction phase). 23

4.1.2 Removal of alien vegetation and associated impact on groundwater quality (construction phase). 27

4.1.3 Impact on groundwater levels due to earthworks, ground surface levelling and runway construction (construction phase) ..................................................................................................... 28

4.1.4 Impact on groundwater quality due to earthworks, ground surface levelling and runway construction (construction phase) ..................................................................................................... 29

4.1.5 Impact of the presence of the runway and taxiways on groundwater levels (operational phase) 30

4.1.6 Impact of the presence of the runway and taxiways on groundwater quality (operational phase) 32

4.2 Cumulative Impacts ......................................................................................................... 32

4.3 Indirect Impacts ............................................................................................................... 32

5. CONCLUSION .................................................................................................... 33

6. RECOMMENDATIONS .................................................................................... 33

7. ACKNOWLEDGEMENTS ................................................................................. 33


GEOSS Report No. 2014/06-10 08 September 2014 iv

8. REFERENCES .................................................................................................... 34

9. APPENDIX A: MAPS .......................................................................................... 36

10. APPENDIX B: LABORATORY RESULTS (CSIR) ........................................... 46

11. APPENDIX C: SITE PHOTOS .......................................................................... 48

LIST OF FIGURES AND MAPS Figure 1: Location of Cape Town International Airport and proposed project footprint

(SRK, 2014). ............................................................................................................................ 2 Figure 2: Proposed construction of realigned runway and taxiways (Naco-SSI, 2008a) ........ 3 Figure 3: Average monthly rainfall and evaporation (ET) for the study area (Schulze et al,

2008) ......................................................................................................................................... 7 Figure 4: Conceptual model for the current status at the CTIA ............................................. 10 Figure 5: Long term borehole water level graph – UWC (Bh02) ............................................. 14 Figure 6: Long term borehole water level graph – UWC (Bh06) ............................................. 15 Figure 7 A & B: A. Study site, recharge zones and pilot study monitoring borehole

locations. B. Groundwater levels in metres below ground level (mbgl) under 133 hectares cleared and un-vegetated ground subjected to wet conditions (CSIR, 2006). ................................................................................................................................................. 16

Figure 8: Piper diagram of the two groundwater samples collected from the piezometers (24th June 2014) ..................................................................................................................... 20

Figure 9: Stiff diagram of the two groundwater samples collected from the piezometers (24th June 2014) ..................................................................................................................... 20

Figure 10: Expanded Durov diagram of the two groundwater samples collected from the piezometers (24th June 2014) ............................................................................................... 21

Figure 11: Conceptual model post-construction phase ........................................................... 24 Figure 12: Conceptual model of the conditions during the operational phase ..................... 25

Map 1: Location of the Cape Town International Airport area within a regional setting .... 37 Map 2: The study site superimposed on a 1:50 000 topocadastral map, showing the

GEOSS auger sites and piezometer positions. ................................................................. 38 Map 3: The study site superimposed on an aerial photograph, showing the GEOSS auger

sites and piezometer positions. ........................................................................................... 39 Map 4: Geological setting of the study area and NGA boreholes (Council for Geoscience

map: 1:250 000 scale 3318 –Cape Town) .......................................................................... 40 Map 5: Aquifer type and yield within the study area (DWA 1:500 000 scale 3317 Cape

Town) ..................................................................................................................................... 41 Map 6: Groundwater level as metres below ground level (base data is SRTM, 2000) ......... 42 Map 7: Groundwater level as metres above mean sea level (base data is SRTM, 2000) ..... 43 Map 8: Aquifer quality within the study area (DWA 1:500 000 scale 3317 Cape Town) .... 44 Map 9: Groundwater vulnerability within the study area (DWA, 2005) ................................ 45

LIST OF TABLES Table 1: Geological formations within the study area ................................................................ 8 Table 2: National Groundwater Archive data within the study area ...................................... 13 Table 3: Groundwater levels, EC and pH, measured at the Airports Company South Africa

groundwater monitoring sites by GPT (2014). ................................................................ 18 Table 4: Auger and piezometer positions ................................................................................... 19 Table 5: Field descriptions of the piezometer and auger sites ................................................. 19 Table 6: Field chemistry of the two piezometer sites ............................................................... 20 Table 7: Water quality classification table ................................................................................... 21 Table 8: Details of borehole samples collected and DWA (1998) limits for domestic use. 22


GEOSS Report No. 2014/06-10 08 September 2014 v

Table 9: Impact 1a – Alien vegetation clearing and groundwater levels ................................ 27 Table 10: Impact 1b – Alien vegetation clearing and groundwater quality ........................... 28 Table 11: Impact 2a – Impact of earth works and construction activities and groundwater

levels ....................................................................................................................................... 29 Table 12: Impact 2b – Impact of earth works and construction activities and groundwater

quality ..................................................................................................................................... 30 Table 13: Impact 3a – Runway and taxiways and groundwater levels ................................... 31 Table 14: Impact 3b – Runway and taxiways and groundwater quality ................................. 32

ABBREVIATIONS ACSA Airports Company South Africa CFA Cape Flats Aquifer ch collar height CSIR Council for Scientific and Industrial Research DWA Department of Water Affairs DWS Department of Water and Sanitation (formerly DWA) EC Electrical conductivity EIA Environmental Impact Assessment ET Evapotranspiration GCS Groundwater Consulting Services GIS Geographical Information System GPT Geo-Pollution Technologies ha hectare ℓ/s litres per second m metres m/d metres per day MAE Mean Annual Evaporation mamsl metres above mean sea level MAP Mean Annual Precipitation MAR Mean Annual Runoff mbch metres below collar height mbgl metres below ground level mg/ℓ milligrams per litre mm millimetres mm/a millimetres per annum mS/m milliSiemens per meter NGA National Groundwater Archive RP reduction potential RWL rest water level SANDF south African National Defence Force SANRAL South African National Roads Agency Ltd SRK SRK Consulting (South Africa) (Pty) Ltd SRTM Shuttle Radar Topography Mission TDS total dissolved solids ToR Terms of References UWC University of the Western Cape WGS84 Since the 1st January 1999, the official co-ordinate system for South Africa is based on the World Geodetic System 1984 ellipsoid, commonly known as WGS84.


GEOSS Report No. 2014/06-10 08 September 2014 vi

GLOSSARY OF TERMS Anisotrophy: Anisotropy is the property of being directionally dependent Aquifer: a geological formation, which has structures or textures that hold water or permit

appreciable water movement through them. Borehole: includes a well, excavation, or any other artificially constructed or improved

groundwater cavity which can be used for the purpose of intercepting, collecting or storing water from an aquifer; observing or collecting data and information on water in an aquifer; or recharging an aquifer.

Brecciated: breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, which can be either similar to or different from the composition of the fragments

Fractured aquifer: fissured and fractured bedrock resulting from decompression and/or tectonic action. Groundwater occurs predominantly within fissures and fractures.

Groundwater: water found in the subsurface in the saturated zone below the water level or piezometric surface i.e. the water level marks the upper surface of groundwater systems.

Hardness: hard water is water that has high mineral content. Hard water is not a health risk but is a nuisance because of mineral build up on plumbing fixtures and poor soap and or detergent performance.

Heterogeneity: a material that is distinctly non-uniform Hydraulic conductivity: measure of the ease with which water will pass through earth

material; defined as the rate of flow through a cross-section of one square metre under a unit hydraulic gradient at right angles to the direction of flow (in m/d)

Intergranular and fractured aquifers: Largely medium to coarse grained granite, weathered to varying thicknesses, with groundwater contained in intergranular interstices in the saturated zone, and in jointed and occasionally fractured bedrock.

Intergranular Aquifer: generally unconsolidated but occasionally semi-consolidated aquifers. Groundwater occurs within intergranular interstices in porous medium. Typically occur as alluvial deposits along river terraces.

Transmissivity / transmissive: the rate at which a volume of water is transmitted through a unit width of aquifer under a unit hydraulic head (m2/d); product of the thickness and average hydraulic conductivity of an aquifer.

Vadose zone: the unsaturated zone above the groundwater level and below the ground surface.

Suggested reference for this report: GEOSS (2014). Groundwater Specialist Study - Cape Town International Airport Runway

Re-alignment and Associated Infrastructure Project. GEOSS Report Number: 2014/06-10. GEOSS - Geohydrological & Spatial Solutions International (Pty) Ltd. Stellenbosch, South Africa.

Cover photo: On-site augering in order to assess groundwater conditions. GEOSS project number:

2014_04-1233


GEOSS Report No. 2014/06-10 08 September 2014 1

1. INTRODUCTION

1.1 Background

The Cape Town International Airport comprises two active runways: the primary runway

and a secondary runway bisecting it. The Airports Company South Africa proposes to re-

align the existing primary runway. This will allow the runway to be lengthened (from

3 201 m to 3 500 m) and create space for future development. The existing secondary

runway will be decommissioned and be incorporated into a new integrated taxiway system,

which will entail the construction of parallel taxiways and rapid exit taxiways to increase the

capacity of the system to handle air traffic. SRK Consulting (South Africa) (Pty) Ltd

(“SRK”) has been appointed to undertake the Environmental Impact Assessment (EIA)

for the project.

Cape Town International Airport is located in the sandy Cape Flats region, immediately

north of the N2 highway, approximately 20 km east of Cape Town’s Central Business

District (Map 1, Appendix A). The surrounding area consists of mixed land uses

including residential, industrial and portions of undeveloped and derelict land. The current

Cape Town International Airport property is approximately 975 ha in extent, incorporating

the passenger terminal and related airport support infrastructure to the west of the

runways, undeveloped land to the east of the runways, and a portion of land to the south,

belonging to the South African National Roads Agency Ltd (SANRAL), but nominally

falling within the Cape Town International Airport property boundary. The Airports

Company South Africa is currently in the planning phase for the acquisition of additional

parcels of land for the realignment project. Airports Company South Africa proposes to

acquire a portion of land (to the east of the airport) which is owned by the State (i.e.

National Housing Board) as well as the portion of land to the south owned by SANRAL to

accommodate the project and future expansion of the airport. A separate facility, presently

used by the police and administered by the South African National Defence Force’s

(SANDF) 35 Squadron, is located to the immediate east of the runways within the Cape

Town International Airport property boundary.

Airport Industria is located to the west of the terminal, while Bishop Lavis and Belhar are

located to the north of Cape Town International Airport (including the M10 (Modderdam

Road) and M12 (Stellenbosch Drive) roads). Modderdam industrial area lies between these

areas. Immediately east of the Cape Town International Airport property is a large, portion

of undeveloped land. Small sand dunes, with isolated patches of indigenous vegetation on

the dune ridges and some small wetland(s) occur in this area. The area is used for illegal

dumping, harvesting of firewood, opportunistic grazing and, possibly, initiation rituals. To

the east of this vacant land and the M171 (Symphony Way), new affordable housing has

been built forming the residential areas of Delft and Delft South. Crossroads, consisting

mostly of informal shacks, is located to the south of Cape Town International Airport

beyond the N2. Philippi Industria is located to the south of Crossroads.



Figure 1: Location of Cape Town International Airport and proposed project footprint

(SRK, 2014).

The current runway system at Cape Town International Airport comprises two active

runways, namely:

Primary runway – 3 201 m long and 60 m wide; and

Secondary runway – 1 700 m long and 46 m wide.

The proposed project comprises the re-alignment of the existing primary runway to an

“18L/36R“ configuration§. The new runway will be 3 500 m long and approximately 75 m

wide and will be built to international specifications to enable the airport to receive Code F

aircraft such as the A380. The existing primary runway will no longer be used as a runway

but will form part of the integrated taxiway system. The existing secondary runway will be

§ A runway's compass direction is indicated by a number written in a shorthand format. A runway with a

marking of "18" is actually close to (if not a direct heading of) 180 degrees. This is a south compass heading. A runway with a marking of "36" has a compass heading of 360 degrees, that is, a north direction. For parallel runways, 'L' and 'R' is added to the runway number.



decommissioned in order to accommodate the new re-aligned runway (Figure 2). In

Figure 2 take careful note of the orientation of the drawing.

Figure 2: Proposed construction of realigned runway and taxiways (Naco-SSI, 2008a)

The proposed development will entail the construction of two parallel taxiways and Rapid

Exit Taxiways to accommodate increasing air traffic. Parallel 3 500 m long taxiways will be

aligned to the west of the primary runway. Taxiway access to the SANDF apron will be

maintained and accommodated within the new runway and associated taxiway system. The

total area occupied by the proposed new taxiway system will be approximately 34 ha.

In total, the new runway and taxiways will have a footprint of approximately 82.7 ha,

almost all located within the existing Cape Town International Airport perimeter fence,

though Cape Town International Airport will have to acquire some land to accommodate

the re-alignment. Additional key elements of the project include:

Eight connecting rapid exit taxiways;

One aircraft isolated parking position and compass calibration pad;

One dual lane taxiway;

Future taxiway tie-ins; and

Widening of existing taxiway.

Associated infrastructure required as part of the project includes stormwater pipelines and

control systems, internal roads, security facilities, etc. In addition, several services such as

Telkom cables, power cables and fibre optic cables will have to be relocated.



Other areas where fill material will be sourced or placed will increase the disturbance

footprint. Approximately 350 ha will be required for cut operations and 170 ha will be

required for fill operations. It is anticipated that construction will be in six phases.

1.2 Terms of Reference (ToR)

1.2.1 Broader project - Terms of Reference

The principle objectives for this study are to:

Describe the existing baseline characteristics of the study area and place these in a

regional context;

Identify and assess potential impacts resulting from the project (including impacts

associated with the construction and operation phases);

Identify and describe potential cumulative impacts resulting from the proposed

development in relation to proposed and existing developments in the surrounding

area;

Recommend mitigation measures to minimise impacts and/or optimise benefits

associated with the proposed project;

Take into account comments and concerns raised by interested and affected parties

and authorities during the Scoping Phase of the project; and

Recommend a draft monitoring programme, if applicable.

The main deliverable from this specialist study is an Impact Assessment Report with

appropriate maps, drawings and figures. This specialist study must consist of the following

components:

Baseline Description: a description of the environment of the study area in its

current state, relevant to the specialist’s field of study (the specialist must provide a

sufficiently comprehensive description of the existing environment in the study

area to ensure that an adequate assessment of the potential impacts of the proposed

development can be made. The baseline should include data collected through a

thorough literature review as well as field surveys); and

Impact assessment: an assessment of how the proposed expansion project would

alter the status quo as described in the baseline description and recommended

measures to mitigate and monitor impacts.

This study must devote considerable effort to the impact assessment and recommendations

for mitigation and not be overly focused on the baseline aspects. The study must also:

Provide an outline of the approach used in the study;

Clearly identify assumptions, limitations and sources of information;

Incorporate local knowledge if possible;

Include a short discussion of the appropriateness of the methods used in the

specialist study;



Be based on accepted scientific techniques for the assessment of the data, where

possible, failing which the specialist is to make judgments based on professional

expertise and experience;

Provide a description of the affected environment, both at a site-specific level and

for the wider region, the latter to provide an appropriate context;

Address the uniqueness or “irreplaceability” of the site in the context of the

surrounding region, at a local, regional (and, if necessary, national) scale. This must

largely be based on a comparison to existing data sources, where available; and

Provide an indication of the sensitivity of the affected environment (Sensitivity, in

this instance, refers to the capacity of an environment to tolerate disturbance

(taking the environment’s natural capacity to recover from disturbance as well as

existing cumulative impacts into account).

The specialist must take care to obtain an understanding of the overall system of which

their specialist discipline is a part, in order to understand how changes to that system will

affect their subject.

Clear statements identifying the potential environmental impacts of the proposed project

must be presented. This includes potential impacts for the construction and operation

phases of the project. The specialist shall clearly identify the suite of potential direct,

indirect and cumulative environmental impacts in the study. Direct impacts require a

quantitative assessment which must follow the prescribed impact assessment methodology.

Indirect and cumulative impacts should be described qualitatively.

The specialist shall assess environmental impacts and also indicate any fatal flaws, i.e. very

significant adverse environmental impacts which cannot be mitigated and which will

jeopardise the project and/or activities in a particular area (if appropriate). Note that all

conclusions will need to be thoroughly backed up by scientific evidence.

Specialists must clearly state the impact to be assessed, followed by a brief description of

the impact and must then present the assessment of the impact, using the prescribed

impact rating system, in the format provided.

Specialists must recommend practicable mitigation measures or management actions that

effectively minimise or eliminate negative impacts, enhance beneficial impacts, and assist

project design. The significance of impacts must be assessed both without and with

assumed effective mitigation. If appropriate, specialists must differentiate between

essential mitigation measures which must be implemented (i.e. implicit in the “assuming

mitigation” rating) and optional mitigation measures which are recommended, i.e. “nice-to-

haves”, but which do not affect the impact rating. Unsubstantiated recommendations for

further studies should be avoided.

Specialists are also required to recommend appropriate monitoring and review programmes

to track the efficacy of mitigation measures (if appropriate). This should include where to



monitor (locations), what (parameters), when (frequency and duration), how (methods) and

who.

1.2.2 Groundwater - specific Terms of Reference

With regard to this groundwater study, the following is required:

Describe and map the existing groundwater resources potentially affected by the

proposed project, including groundwater levels, groundwater quality, hydrological

linkages with other surface and groundwater resources and existing users of

groundwater resources in the area. The description of the affected environment

must be both at a site-specific level and for the wider region, the latter to provide

an appropriate context;

Define applicable legislative requirements regarding any permit applications

required;

Identify potential impacts of the proposed project on groundwater resources as

well as potential impacts of groundwater on the proposed development;

Assess the impacts of the proposed project on groundwater resources in the area

using the prescribed impact assessment methodology;

Identify and assess potential cumulative groundwater impacts resulting from the

proposed development in relation to proposed and existing developments in the

surrounding area;

Recommend practicable mitigation measures to avoid and/or minimise/reduce

impacts and enhance benefits. Assess the effectiveness of proposed mitigation

measures using the prescribed impact assessment methodology;

Recommend and draft a monitoring campaign to ensure the correct

implementation and adequacy of recommenced mitigation and management

measures, if applicable; and

Assist the EAP in addressing any relevant comments raised by stakeholders.

1.3 Study area

The Cape Town International Airport is located on the Cape Flats, near Cape Town

(Map 1, Appendix A).

1.3.1 General

The Cape Flats is characterised by an expansive, low-lying plain of white sand. The airport

is located on this flat plain. A poorly defined dune system is evident to the east of the

existing airport boundary. The dune system is stabilised by vegetation (mostly alien

vegetation with isolated patches of indigenous vegetation on the dune ridges) and with

wetlands in the dune slacks. Map 2 and Map 3 (Appendix A) show the study area

superimposed on a topocadastral map and aerial photograph respectively.



1.3.2 Climate, Rainfall and Evaporation

The Western Cape has a semi-arid Mediterranean climate, which is strongly influenced by

the cold Benguela ocean current and coastal winds. The Cape Town area is characterised

by dry warm summer months (October to April) and wetter cool winter months (from May

to September).

Although rainfall occurs throughout the year, most rainfall occurs between May and

August. The long-term average monthly rainfall measured at the airport is shown in

Figure 3. The average annual rainfall is 569 mm/a (Schulze et al, 2008). The long-term

average monthly evaporation (ET) data, is also shown in Figure 3. The average annual

evaporation is 2 030 mm/a (Schulze et al, 2008).

Figure 3: Average monthly rainfall and evaporation (ET) for the study area (Schulze et al,

2008)

From the rainfall and evaporation data presented in Figure 3 it can be seen that the field

work (carried out on 24th June 2014) was completed during a high rainfall period. With this

monthly pattern of rainfall and evaporation groundwater recharge will be quite significant

as the rainfall occurs when evaporation is lowest. The risk of flooding will also be highest

during the months of June, July and August. Flooding can occur later in the year, especially

if an exceptionally heavy rainfall event occurs.

1.3.3 Regional Geology

The area is characterised by Quaternary-age sediments overlying basement rocks of the

Malmesbury Group. The Geological Survey of South Africa (now the Council for

Geoscience) has mapped the area at 1:250 000 scale (map sheet 3318 Cape Town). The

geological setting is shown in Map 4 (Appendix A). The main geology of the area is listed

in Table 1.

0

50

100

150

200

250

300

350

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mill

ime

ters

(m

m)

Month Mean ET Mean rainfall



Table 1: Geological formations within the study area

Group Formation Lithology

Sandveld

Witzand Very fine to very coarse grained calcareous coastal dune sand

Springfontyn Fine to medium grained quartzitic sand

Malmesbury

Group Tygerberg

Grey to green phyllitic shale, siltstone and medium to fine

grained impure sandstone (greywacke)

Tertiary to Recent age sedimentary deposits underlie the area, comprising mainly calcareous

sands of the Sandveld Group, which are underlain by rocks of the Malmesbury Group.

The airport is predominantly underlain by deposits of the Witzand and the Springfontyn

Formations.

The Witzand Formation consists mainly of very fine to very coarse calcareous sand

and has abundant shells and shell fragments. These sands form an extensive

system of parabolic, vegetation-bound coastal dunes.

The Springfontyn Formation, which is aeolian in nature, comprises mainly fine to

medium grained quartzose sands. The grain size often increases with depth and

thin calcareous clay and peat lenses may locally be present. This Formation is

relatively uniform and free of inclusions. Vandoolaeghe (1989) suggest this

formation might be a decalcified facies of the Witzand Formation. The

decalcification is due to the relatively high surface and sub-surface permeability and

associated recharge rate of rainfall.

The basement rocks of the area consist of the Tygerberg Formation of the Malmesbury

Group. This formation consists mainly of alternating layers of grey to green phyllitic shale,

siltstone and medium to fine grained impure sandstone (greywacke). The transition

between the sands and the Malmesbury rocks is characterised by a clay layer which is the

product of weathering of the shale. The degree and depth of weathering can change over

relatively short distances (SRK, 2011). The thickness of this weathered zone can vary

significantly, but can be up to 44 m thick (Wright and Conrad, 1995). The bedrock

gradient, in broad terms, is from + 80 metres above mean sea level (mamsl) near Bellville

to -40 mamsl at Zeekoevlei. At the study area the bedrock elevation is approximately

+20 mamsl and it slopes down to the south-west.

Potential mineral resources on the proposed site include building sand and calcrete

deposits. These mineral resources are used primarily in the building industry. Calcrete is

also used as a sub-base for roads. Formal sand mining takes place to the north-east of the

airport.

1.3.4 Regional Hydrogeology

The Sandveld Group deposits constitute what is known as the Cape Flats Aquifer (CFA).

The aquifer is regionally unconfined and internally is essentially free of lateral hydraulic or

geological boundaries which may influence regional behaviour. The aquifer is not



hydrologically linked to any other aquifer except the talus / scree material along the foot of

the mountains in the west. The aquifer is extensive and pinches out against “impermeable”

boundaries in the east, west and north whilst the southern boundary is defined by the

coastline extending along False Bay, between Muizenberg and Macassar. The thickness of

the sand at the study area is approximately 25 m. The saturated thickness of the aquifer in

the study area is approximately 20 – 25 m.

Sands of the Witzand and Springfontyn Formations constitute the main target for

groundwater abstraction from the CFA. These sands range in grain size from very fine to

very coarse and are generally well-sorted and well-rounded. The aquifer transmissivity

within the study area is approximately 100 m2/d. These formations do, however, possess a

degree of heterogeneity and anisotropy due to vertical and lateral grain size gradation and

the occurrence of sandstone, clay or calcrete lenses. The vertical permeability can be

smaller by a factor of 10 to 20 (or even up to 100) when compared with the horizontal

permeability. The bedrock, which consists of weathered Malmesbury Group meta-

sediments, is generally regarded as an impervious basement. However in places the

Malmesbury Group contains brecciated and transmissive fault zones resulting in a fractured

aquifer with high yielding boreholes. The aquifer is recharged directly principally from

rainfall. The average annual rainfall, which occurs mainly in winter and early spring, ranges

from 500 to 800 mm across the Cape Flats. Vandoolaeghe (1989) confirmed that net

groundwater recharge through sandy soils of the primary aquifer varies between 15% and

37% of the annual precipitation. The evaporation rates from the aquifer have been

measured at the surface to be 2 x 10-8 m/s in summer. Evaporation is higher towards the

eastern portion of the CFA, where shallow calcrete cause perched water tables (Gerber,

1976). Groundwater flow in the Cape Flats is either west to Table Bay or south to False

Bay. In the regional study on the CFA (Wright and Conrad, 1995) indicate the flow

direction is mainly towards the south-west within the study area. According to the regional

1:500 000 scale groundwater map of Cape Town (3317), produced by the Department of

Water Affairs, the project area does host an intergranular aquifer with an average borehole

yield of 0.5 ℓ/s to 2.0 ℓ/s (Map 5, Appendix A).

The groundwater quality within the main part of the aquifer generally has a low salinity yet

a relatively high hardness. Due to the depositional history of the aquifer, zones of saline

water do occur at different stratigraphic levels. The high evaporation rates in summer also

result in high salinity areas. For the study area the regional groundwater quality, indicated

by Total Dissolved Solids is in the range from 500 mg/ℓ to 2 000 mg/ℓ. This equates to

an Electrical Conductivity range of 70 mS/m to 300 mS/m (DWAF, 2000) (Map 8,

Appendix A).

The regional groundwater vulnerability is shown in Map 9 (Appendix A) as determined by

DWA (2005). The groundwater in the entire area is classified as having a “medium to

high” vulnerability to surface based contamination.

Based on a conceptual understanding of the site geohydrology a schematic diagram was

developed of the status quo (Figure 4).



Figure 4: Conceptual model for the current status at the CTIA



1.4 Assumptions and Limitations

1.4.1 Assumptions

There is often a high degree of spatial variability in groundwater studies, relating to soil

conditions, geological setting and geohydrological parameters. It is difficult to glean a lot

of geohydrological information without drilling boreholes and sampling. Thus borehole

information and associated data (such as drill logs, water levels, and groundwater

chemistry) are useful for most geohydrological studies. It is assumed that the

geohydrological conditions are relatively consistent between sampling points, unless there

is clear evidence to the contrary. A lot of the work is based on averages, i.e. average annual

rainfall and average groundwater conditions. The absence of water level and rainfall data

make it difficult to make predictions regarding extreme events. For example: a very high

intensity rainfall event in winter, when the groundwater levels are at the shallowest (i.e.

closest to ground level), may result in flooding of certain portions of the study area. There

is insufficient data available to accurately predict the impact of the extreme conditions.

Assumptions will therefor need to be made in this regard.

1.4.2 Limitations

The limitations pertain to the lack of groundwater monitoring data and long-term records.

The study area is not entirely fenced and any monitoring sites established in the past have

been vandalized and rendered non-functional. Thus long-term groundwater level

responses cannot be determined. Additionally, the geographical distribution of existing

monitoring sites is not ideal, but is considered adequate for the purposes of this study.

There are more groundwater quality monitoring sites in the western portion of the study

area than in the east. This is because the airport infrastructure and fuel storage areas are

located in the western portion of the area. The borehole drilling in the eastern portion is

limited so geological detail in that area is sparse. For example, there is not accurate

information on the depth, thickness and extent of the calcrete layers in the eastern portion.

The areas prone to flooding are those where impermeable geological layers are shallow,

resulting in perched aquifers. Without detailed geological information it is difficult to

forecast exactly where flooding is likely to occur. However sufficient data does exist to

enable interpretation of a groundwater level map. For this reason no borehole drilling was

included in this geohydrological specialist study. Hand augering of piezometers to measure

groundwater levels and quality sufficed for this project. Deeper borehole drilling was not

considered necessary for this study.

2. METHODOLOGY

The methodology to achieve the objectives of the ToR is as follows:

Undertake a desktop study of existing information available from relevant

literature, the National Groundwater Archive (NGA), the Department of Water

and Sanitation (DWS) and previous groundwater monitoring undertaken by ACSA;



Undertake a site visit to identify and verify the positions of boreholes at the Cape

Town International Airport and surrounding areas;

Undertake a hydrocensus targeting large industries, schools and institutions in the

area; and

If required, install a limited number of piezometers to establish groundwater levels

and quality.

The approach to the groundwater study was to obtain as much existing data and

information as possible. This included requesting borehole data from the Department of

Water Affair’s National Groundwater Archive (NGA), including borehole yields,

groundwater depths and groundwater quality. No borehole yield data was available and the

Electrical Conductivity data obtained was not usable.

Many relevant reports were obtained from SRK and the Airports Company South Africa.

The reports were reviewed and relevant information retrieved from the reports. This

information, if spatially referenced, was then captured in a Geographical Information

System (GIS) set up for the project by GEOSS. There was a lot of useful information

from the Geo-Pollution Technologies (GPT) (2014) report on groundwater levels and

quality in the western part of the study area.

A list of all the references is included in Chapter 8, but key sources of information

pertaining to this study and reviewed in detail include:

Arcus Gibb, 2004. Sub-soil drainage along the main runway of Cape Town

International Airport

CSIR, 2006. Impact of Alien Invasion Vegetation Report

Naco-SSI, 2008a. Pavement Preliminary Design Report (Doc 3)

Naco-SSI, 2008b. Drainage Preliminary Design Report (Doc 6)

Naco-SSI, 2010. Hydrological Investigation Report (Doc 11)

GPT, 2014. Groundwater Sampling Report.

SAS, 2014. Draft Freshwater Ecological Assessment

SRK, 2014. Final Scoping Report.

Following on from the literature review discussions were held with those who have

knowledge of the aquifer in the vicinity of the Cape Town International Airport.

Discussions were held with SRK (Sheila Imrie); Airports Company South Africa (Sean

Bradshaw); University of the Western Cape (Dr Jaco Nel - GCS); and RoundOne Drilling

Solutions (Jason Greeff).

This was followed up by field work carried out on 24 June 2014, to try and locate previous

relevant field installations as well as to obtain new data. Note the western portion of the

study area (within the existing airport boundaries) was not visited, however data was

obtained from previous reports. In the eastern portion of the study area all previously

referred to boreholes/piezometers could not be located (however the Naco-SSI (2010) data



was still used in this project). The area is unfenced, thus open to the public and prone to

vandalism (and illegal dumping).

Hand augering of 70 mm diameter holes was completed along the proposed route of the

re-aligned runway in order to establish groundwater depth and the presence of

impenetrable layers. Piezometers were installed at two of the auger sites, where

groundwater was intersected. Samples were collected at these two sites and submitted to

the CSIR for analysis.

This approach is appropriate for the assessment of shallow groundwater and vadose zone

conditions. This approach, however, does not provide much information about the deeper

CFA. In order to investigate the CFA more thoroughly within the study area it will be

necessary to drill boreholes through the hard layers down to the bedrock. It was decided

that such drilling was not required to meet the Terms of Reference for this project. In

addition the primary purpose of the groundwater study is to assess the likelihood of

flooding occurring and the drilling of the total depth of the CFA will not contribute

significantly to the prime purpose of this study.

The combined approach of a literature survey and field work enabled characterisation of

the area.

3. RELEVANT EXISTING DATA AND DATA AQUIRED FROM FIELD WORK

3.1 Desktop investigation

3.1.1 National Groundwater Archive (NGA)

A search was completed of the Department of Water Affairs groundwater database,

specifically the National Groundwater Archive (NGA). The results obtained for the study

area are presented in Map 2 and Map 3 (Appendix A), and are listed in Table 2. A total

of 16 NGA sites were obtained. The data associated with these sites is limited; however

some groundwater level and groundwater quality does exist (presented in Table 2).

Table 2: National Groundwater Archive data within the study area

ID Map ID Latitude Longitude Water Level

(mbgl) pH

3318DC00263 NGA01 -33.98023 18.60093 1.28 7.3

3318DC00262 NGA02 -33.97828 18.59787 1.34 7.6

3318DC00261 NGA03 -33.97773 18.59926 1.55 -

3318DC00264 NGA04 -33.97495 18.59732 2.22 7.5

3318DC00265 NGA05 -33.97495 18.59759 2.37 7.3

3318DC00270 NGA06 -33.97467 18.61287 3.79 7.6

3318DC00267 NGA07 -33.97384 18.59454 1.70 7.4

3318DC00274 NGA08 -33.97273 18.59870 2.19 -

3318DC00271 NGA09 -33.97217 18.59426 0.72 7.2



3318DC00273 NGA10 -33.97134 18.59370 1.03 7.5

3318DC00272 NGA11 -33.97134 18.59398 0.89 -

3318DC00275 NGA12 -33.96773 18.59732 2.4 7.2

3318DC00269 NGA13 -33.96551 18.60870 0.87 7.6

3318DC00266 NGA14 -33.95912 18.59370 0.56 7.3

3318DC00268 NGA15 -33.95912 18.60870 1.45 7.7

3318DC00001 NGA16 -33.95761 18.59883 2.66 -

3.1.2 University of the Western Cape (UWC)

There is very little continuous monitoring of groundwater levels within the Cape Flats

Aquifer. However the University of the Western Cape (UWC) did drill a number of

research boreholes which were equipped with borehole water level sensors and data

loggers. It was not possible to track down any reports on the UWC boreholes; however it

was possible to obtain some groundwater level data. The geological setting, as revealed by

these boreholes, consists of approximately 30 m of unconsolidated sands, with peat layers,

overlying Malmesbury Group bedrock. The sands increased in grain size with depth. The

boreholes were drilled to approximately 130 m and fractures were intersected in the

bedrock at approximately 100 m. The primary aquifer had a yield of approximately 2 ℓ/s

and the fractures in the bedrock were higher yielding at approximately 5 ℓ/s (pers. comm.,

Dr J. Nel, 2014).

The groundwater level data was obtained for two of the UWC boreholes and the

groundwater levels are plotted in Figure 5 and Figure 6. The UWC boreholes are

approximately 2.8 km north-east of the Cape Town International Airport.

Figure 5: Long term borehole water level graph – UWC (Bh02)



Figure 6: Long term borehole water level graph – UWC (Bh06)

From Figure 5 the range in the natural seasonal borehole water level (UWC_02)

fluctuation is approximately 0.68 m, with the water level being approximately 4.87 mbgl at

its shallowest. From Figure 6 it can be seen the natural seasonal borehole water level

(UWC_06) range is approximately 0.91 m, with the shallowest groundwater level being

approximately 5.19 mbgl.

3.1.3 Proposed Belhar Housing Development

From a study completed by GEOSS at a proposed development in Belhar (GEOSS, 2013),

six piezometers were installed on site and the groundwater levels were measured from

summer to winter. The range in water levels was greater than measured at UWC, with the

average range of the six sites being 1.590 m. The smallest fluctuation measured was

1.497 m and the largest was 1.691 m. The Belhar study site is 3 km north-east from the

Cape Town International Airport.

3.1.4 CSIR (2006)

The CSIR completed a study in 2006 to address the impact of alien vegetation removal on

groundwater levels (CSIR, 2006). The extent of the study area and results obtained by the

CSIR (2006) study area are shown in Figure 7A and Figure 7B respectively. The CSIR

study area focussed more on the current runway area. The current study area is just to the

east of the CSIR (2006) study area. The results of the CSIR study indicated:

The alien acacia vegetation is not measurably discharging groundwater by

evapotranspiration;

For the vegetated areas the groundwater recharge was 7%;

For the areas that are grassed and cleared of vegetation, the recharge rate increased

to 24% of the rainfall;

Therefore groundwater levels and risk of flooding are higher in cleared areas.



For areas cleared of vegetation the following is concluded:

short term: high risk of flooding and very high risk to runway integrity

long term: moderate risk of flooding and high risk to runway integrity if an area of

133 ha is cleared simultaneously.

Figure 7 A & B: A. Study site, recharge zones and pilot study monitoring borehole locations. B. Groundwater levels in metres below ground level (mbgl) under 133 hectares

cleared and un-vegetated ground subjected to wet conditions (CSIR, 2006).

The CSIR (2006) stated the risks could be mitigated to a very low risk if the following

measures are taken:

The clearance and re-vegetation is conducted in a phased manner.

Groundwater is abstracted from the eastern part of the site.

However please note the new runway will be built substantially higher than the existing

ground levels (SSI, 2010) (see Section 3.1.5) thus the CSIR (2006) mitigation measures are

considered unnecessary.

3.1.5 Naco-SSI (2010)

A hydrological investigation was completed by Naco-SSI in February 2010 (Naco-SSI,

2010) for the new aligned runway RWY 18-36 and associated taxiways. The purpose of

this hydrological study was to investigate and record the existence and fluctuation of the

groundwater level in the study area. This information was required to determine the

optimum fixed construction ground level posing the minimum risk of ground water

influence on the detail design. In the report it is stated that a common feature of the Cape

Flats area is the general occurrence of a shallow groundwater level, during the winter

rainfall season. Perched groundwater levels have also been observed at several locations

towards the south-eastern end of the proposed runway area. It is apparent that these

groundwater levels are elevated in areas of hard impermeable calcrete where the sand

overburden is of limited thickness.



To accurately determine the actual levels of the groundwater as well as the magnitude of

the seasonal fluctuation in these levels, a set of 15 piezometers were installed across the

future construction site. During November 2008 these piezometers were installed by

Fairbrother Geotechnical Engineering, mostly by means of water jetting, to a depth of

5.0 m below ground level. Several of the holes had to be core drilled due to the presence

of shallow hard calcrete lenses. The installation of the piezometers was completed in

January 2009 with the first readings taken at the end of that month.

There are two critical factors to consider when establishing a ground level for future

construction purposes. The one is the risk of a shallow groundwater level below the

runway and the other is the cost involved in site clearing and preparing of the site for

construction work (mass earthworks). Naco-SSI (2010) stated that a geotechnical

investigation revealed the presence of scattered, hard, calcrete lenses to the south-east of

the site resulting in several perched groundwater levels. It is also important to note that

removal of vegetation during site preparation could have an influence on the level of the

groundwater level as well. Due to the vast surface area involved the slightest raising or

lowering of the construction ground level can lead to a very large increase or saving in

construction cost (Naco-SSI, 2010).

Naco-SSI (2010) stated the results obtained indicated:

The shallowest water level recorded in relation to existing ground level was 410 mm

below existing ground level (0.410 mbgl).

The deepest water level recorded in relation to existing ground level was (4 590 mm

below existing ground level (4.590 mbgl).

The smallest seasonal fluctuation recorded was 150 mm (piezometer No. 10) and

the highest fluctuation was 1 330 mm.

The average fluctuation between the shallowest and deepest recording was

616 mm.

3.1.6 Geo Pollution Technologies (GPT, 2014)

Geo Pollution Technologies (GPT) was appointed by the Airports Company of South

Africa to conduct groundwater sampling at the Cape Town International Airport. Water

was collected from 32 on-site monitoring wells. All the monitoring wells are to the west of

the existing runway. Samples were collected and analysed for organic parameters. The

depth to groundwater was measured to lie between 1.585 mbgl and 3.070 mbgl. The field

work was completed on 13 and 14 November 2013 (a time when the groundwater levels

are expected to be quite shallow following the winter rains). Being a primary aquifer, the

water levels respond quickly to rainfall events and are recharged rapidly during the wet

winter months. The existing monitoring well network can be used for on-going

monitoring. The groundwater levels and basic water chemistry is listed in Table 3. Please

note with regard to the values in Table 3, the groundwater levels and pH were measured

on 13 and 14 November 2013 and the EC readings are from sampling carries out in 2012.



Table 3: Groundwater levels, EC and pH, measured at the Airports Company South Africa groundwater monitoring sites by GPT (2014).

Well_ID MW14 MW15 MW16 MW17 MW18 MW19 MW20 MW21

SWL (mbgl) 2.350 2.930 2.315 2.273 2.250 2.465 2.225 2.115

EC (mS/m) 112.8 - - - - - - -

pH 6.29 7.38 - -

- - -

Well_ID MW22 MW23 MW24 MW25 MW26 MW27

SWL (mbgl) 1.595 1.585 1.775 1.813 1.740 1.705

EC (mS/m) 86.5 86.5 61.6 72.9 - 64.2

pH 7.15 7.02 7.42 7.6 7.6 7.4

Well_ID MW28 MW29 MW30 MW31 MW32 MW33

SWL (mbgl) 1.730 1.765 2.110 2.220 2.800 3.070

EC (mS/m) 56.3 94.4 54.5 103.2 126.6 83.9

pH 6.7 6.64 6.98 7.1 5.1 6.82

Well_ID MW36 MW38 MW39 MW4 MW40 MW41 MW44

SWL (mbgl) 2.295 2.373 2.370 2.490 2.150 2.210 2.030

EC (mS/m) - - 94.3 60.7 76.7 57.2 80.6

pH 8.02 - 7.38 7.7 6.31 7.64 8.74

From Table 3, the minimum groundwater level recorded was 1.585 mbgl and the

maximum 3.070 mbgl, with the average groundwater level being 2.176 mbgl. The pH

values ranged from 5.1 to 8.02. The groundwater quality data, as indicated by Electrical

Conductivity (EC) and measured in 2012 (the data being considered more representative

than 2013), ranges from 54.5 mS/m to 126.6 mS/m. The average EC for the 2012

sampling run was 80.8 mS/m.

3.2 Field assessment

The field work, carried out by GEOSS, took place on 24th June 2014. Some site

photographs from the field work are included in Appendix C. The field work included the

assessment of the NGA data obtained from DWA. None of the NGA sites were located

on the eastern side of the runway, nor were any of the Naco-SSI (2010) piezometers found.

The area visited during the field work is not fenced and open to the public, thus vandalism

and illegal dumping does occur. The area is thickly infested with alien vegetation.

During the site visit, a number of sites were augered by hand. This work was done to

determine if groundwater is present in the vicinity of the proposed new runway area and

also to determine the vadose zone thickness.

If groundwater was intersected, a 50 mm slotted PVC pipe was installed, as deep as

possible (with hand augering this is typically just beneath the groundwater level, as the



sands tend to collapse at the groundwater level). The PVC pipe was slotted (i.e. screened)

to allow for the sampling of the groundwater and free movement of groundwater in the

piezometer for the measurement of an accurate groundwater level. Such piping and

screening is referred to as a piezometer in this report. Of the sites augered, only two

intersected groundwater and thus only two piezometers were installed. The positions of

the auger sites and piezometers are presented in Table 4. The distribution of the auger

sites and piezometers is shown in Map 2 and Map 3 (Appendix A). In Table 4 the depth

of the sand layer and distance to refusal (total depth) is also given for the fiver auger sites.

Table 4: Auger and piezometer positions

Site_ID Latitude (WGS84)

Longitude (WGS84)

Elevation (mamsl)

Total Depth (mbgl)

RWL (mbgl)

PZ_1 -33.99509 18.62325 34 1.465 0.805

PZ_2 -33.95897 18.60239 46 1.022 0.500

Auger_1 -33.99074 18.62150 42 1.610 n/a

Auger_2 -33.99084 18.62121 39 0.380 n/a

Auger_3 -33.98776 18.61894 44 3.470 n/a

Auger_4 -33.98078 18.61664 48 1.550 n/a

Auger_5 -33.97445 18.61139 47 1.600 n/a

The field descriptions of the sites are included in Table 5.

Table 5: Field descriptions of the piezometer and auger sites

Site_ID Comments

PZ_1 Stopped on white cemented sand -very hard. Wetland nearby.

PZ_2 Light buff coloured sand. Solid sandstone. There is standing water nearby.

Auger_1 Solid sandstone layer - no water.

Auger_2 Solid sandstone layer - no water.

Auger_3 Site in a drainage channel - however dry and no groundwater at all. Stopped on calcrete.

Auger_4 Surficial calcrete present - very little sand. Stopped on solid calcrete.

Auger_5 Brown soil - slightly damp above hard layer – which is a clay rich material.

Based on a local driller’s knowledge of the area these impermeable layers are typically 2 to

3 mbgl and not very laterally extensive. The layers are typically 1 to 2 m thick. Beneath

these impermeable layers is typically 3 to 7 m of medium- to coarse- grained sands, that

have a high hydraulic conductivity (pers. com., Jason Greeff, Round One Drilling

Solutions, 2014).

Two groundwater level maps were generated. The one map represents the depth to the

groundwater surface (also referred to as a water table) from ground level (Map 6,

Appendix A). The other map represents the groundwater surface as metres above mean

sea level (Map 7, Appendix A). A Bayesian statistical approach was used to model these

two surfaces, using the software called Tripol, and SRTM data was used to represent the

ground surface. The detailed ground surface, that was surveyed, was not available in a GIS

friendly format at the time of writing this report, thus SRTM data was used.



The chemistry parameters measured in the field from the two piezometers are listed in

Table 6.

Table 6: Field chemistry of the two piezometer sites

Site_ID pH Temperature

(deg_C) EC

(mS/m) RP

(mV) Salinity (mg/ℓ)

PZ_1 7.17 15.6 464 -47 2400

PZ_2 7.67 18.8 518 -74 3510

Two samples were collected and submitted to the CSIR (Stellenbosch) for chemical

analysis. The results of the analysis are included in Appendix B. The chemical

composition of the groundwater is shown in Figure 8 (Piper diagram) and Figure 9 (Stiff

diagram).

Figure 8: Piper diagram of the two groundwater samples collected from the piezometers

(24th June 2014)

Figure 9: Stiff diagram of the two groundwater samples collected from the piezometers

(24th June 2014)



From Figure 8 and Figure 9 it can be seen that the groundwater has a dominant sodium-

chloride nature, which is typical for the area and for the geological setting.

The chemical composition of the two samples is similar, however the more northern site

has a higher salinity than the southern site. The southern site is closer to a larger wetland

area which will act as a source of recharge for better quality water. There is far less

ponding to the north of the site.

Figure 10 shows an expanded Durov diagram and the samples plot in an area which is

classified as naturally high salinity water.

Figure 10: Expanded Durov diagram of the two groundwater samples collected from the

piezometers (24th June 2014)

The water samples have also been classified according to the DWA (1998) water quality

guidelines as outlined in Table 7. This classification is for the domestic use of water. The

classified results are listed in Table 8. This “poor” to “dangerous” classification of the

water is an indication of the low importance of the aquifer in this area for domestic

consumption.

Table 7: Water quality classification table

Blue (Class 0) Ideal water quality - suitable for lifetime use.

Green (Class I) Good water quality - suitable for use, rare instances of negative effects.

Yellow (Class II) Marginal water quality - conditionally acceptable. Negative effects may occur.

Red (Class III) Poor water quality - unsuitable for use without treatment. Chronic effects may occur.

Purple (Class IV) Dangerous water quality - totally unsuitable for use. Acute effects may occur.

The groundwater chemistry distribution, as indicated by Electrical Conductivity (in mS/m),

is shown in Map 8 (Appendix A). Map 8 (Appendix A) includes the regional

groundwater quality as mapped by DWA (2000) as well as the results of samples collected

from boreholes in the area. The EC of the groundwater sampled by GEOSS at the two

piezometer sites is significantly higher than samples collected GPT (2014) in the western

portion of the study site.



Table 8: Details of borehole samples collected and DWA (1998) limits for domestic use.

Borehole PZ_1 PZ_2

DWA (1998) Drinking Water Assessment Guide

Class 0

Class I

Class II

Class III

Class IV

pH 7.17 7.67 5-9.5 4.5-5 & 9.5-10 4-4.5 & 10-10.5 3-4 & 10.5-11 <3 &>11

EC (mS/m) 464 518 <70 70-150 150-370 370-520 >520

mg/ℓ mg/ℓ mg/ℓ mg/ℓ mg/ℓ

Total Dissolved Solids (mg/ℓ) 2 746 4 416 <450 450-1000 1000-2400 2400-3400 >3400

Sodium as Na (mg/ℓ) 747 1 290 <100 100-200 200-400 400-1000 >1000

Magnesium as Mg (mg/ℓ) 72 229 <30-70 70-100 100-200 200-400 >400

Calcium as Ca (mg/ℓ) 210 254 0-80 80-150 150-300 >300

Potassium as K (mg/ℓ) 25 37 <25 25-50 50-100 100-500 >500

Chloride (mg/ℓ) 1 220 2 200 <100 100-200 200-600 600-1200 >1200

Nitrate plus nitrite as N (mg/ℓ) 17 2.8 <6 6-10 10-20 20-40 >40

Sulphate as SO4 (mg/ℓ) 147 671 <100-200 200-400 400-600 600-1000 >1000

Alkalinity as CaCO3 (mg/ℓ) 452 505

Iron As Fe (mg/ℓ) 0.01 0.05 <0.01-0.5 0.5-1.0 1.0-5.0 5.0-10.0 >10

Manganese as Mn (mg/ℓ) <0.01 0.01 <0.05-0.1 0.1-0.4 0.4-4 4.0-10.0 >10



4. IMPACT IDENTIFICATION AND ASSESSMENT

Each major potential geohydrological impact (whether positive or negative) associated with

the proposed project has been outlined below and rated in terms of its significance using an

impact rating methodology. The degree of confidence of each assessment is also stated.

4.1 Direct Impacts

With regard to the groundwater setting of the area and the proposed runway and associated

taxiways development, the activities that may impact on the groundwater of the study area

are considered to be:

1. Removal of alien vegetation and associated impact on groundwater levels and

groundwater quality (construction phase).

2. Earthworks required to level the area (i.e. cut and fill) and removal of existing

wetlands on groundwater levels and quality (construction phase).

3. Presence of increased impermeable surfaces (i.e. the new runway and taxiways)

on groundwater levels and quality (operational phase).

These are discussed individually, but are also considered collectively as it is anticipated that

all three will take place. The impacts during the construction phase are presented in

Figure 11. The impacts during the operational phase are shown in Figure 12.

4.1.1 Removal of alien vegetation and associated impact on groundwater levels (construction phase).

4.1.1.1 Description

Prior to the development of the runway and taxiways it will be necessary to remove the

alien vegetation on the portion of the site to the east of the existing airport infrastructure.

It is most probable that all the alien vegetation will have to be removed with regular follow

up to ensure there is no re-growth. In all likelihood the alien vegetation will be replaced

with a grass after the earthworks have been completed. The CSIR (2006) reported the

groundwater recharge is 7% of the rainfall in vegetated areas. Due to the high permeability

of the soils and sands this relatively low recharge rate is attributable to the vegetation

intersecting and abstracting the soil moisture as it passes the root zone. The CSIR (2006)

report stated that in grassed and cleared areas the recharge will be 24%. It is expected that

520 ha of land will be cut and filled (see Section 1.1) for the proposed new upgrades.

Based on a mean annual rainfall of 569 mm/a, the recharge volumes will be:

207 116 m3/a for the lower recharge scenario (7% of mean annual rainfall); and

710 112 m3/a for the higher recharge scenario (24% of mean annual rainfall).



Figure 11: Conceptual model post-construction phase



Figure 12: Conceptual model of the conditions during the operational phase



This is a concern for the areas where groundwater is already relatively shallow, as presented

in Map 6 (Appendix A). The Naco-SSI (2010) report stated the shallowest groundwater

level measured to be 0.410 mbgl. Over an area of 520 ha this increased recharge amounts

to 0.0967 m (say 100 mm) (for cleared land – i.e. high recharge scenario), so the

groundwater level could be as shallow as 0.310 mbgl. In addition to this Arcus Gibb

(2004) warns that isolated large rainfall events could significantly raise the groundwater

level for short periods of time.

These highlight the potential for flooding if the land surface is not sufficiently elevated, as

well as for ponding in lower lying areas where the groundwater surface exceeds the land

surface. Ponding would also be expected in areas where the ground surface is lowered

during the construction activities. Associated to ponding on the site would be an increased

number of wetland birds and animals.

4.1.1.2 Proposed Mitigation Measures

CSIR (2006) reported that groundwater levels will rise more rapidly in cleared areas and the

risk of flooding is higher in these areas. The integrity of the runway is considered to be at

high risk if the groundwater level comes within 0.8 m of the ground surface. For the

reduction in the rapid increase in the groundwater level in the wet winter months, the type

of grass planted needs to be a grass type that has a deep root system and is able to absorb

and transpire moisture at a relatively high rate. This will have limited efficacy as the rainfall

and recharge mainly occurs when plants and vegetation are relatively dormant. It is outside

the specialist’s area of expertise however it is assumed grass is best for the vegetative cover

in the runway environs.

There are two concerns with regarding to flooding. Firstly during high rainfall events the

runway is to have no standing water on it and this is being addressed by having a

“thickened keel” section (Naco-SSI, 2008a). The “thickened keel” means the central

portion (midline) of the runway will be slightly elevated and rainwater will drain off the

runway away from this central “keel”. Secondly the runway and taxiways must be elevated

above the ambient groundwater level. The re-aligned runway will be built substantially

higher than the existing ground levels (Naco-SSI, 2010). If the shallowest groundwater

level can be 0.237 mbgl and the CSIR (2010) consider 0.8 m to be the minimum distance

from the groundwater level to the runway, then it needs to be elevated at least 0.527 metres

above ground level. The second issue is to ensure the runway environs is not flooded as

this will increase the favourability of the habitat for birds and wildlife. This latter issue is

addressed in the two paragraphs above.

4.1.1.3 Assessment of impact

The study area comprises only a small portion of the Cape Flats Aquifer and removal of

alien vegetation from the footprint of the proposed development will result in a seasonal

increase of groundwater levels across the area where the alien vegetation has been cleared,



however it will not extend much beyond the cleared areas. Thus the extent of the impact is

considered to be “local”. It is unlikely that groundwater levels will rise an additional height

(i.e. greater than the norm) beneath adjacent residential areas. This impact is considered to

be of medium intensity and be of long term duration). The consequence rating is thus

“very low” (i.e. a score of 4). The probability is “probable” (i.e. > 70% - 90% chance of

occurring). The overall significance is thus “very low”. The status is considered to be

negative. The level of confidence associated with the assessment is “high”. With the

implementation of mitigation measures the intensity reduces from “medium” to “low” and

the consequence remains “very low”; the probability remains “possible” and the

significance remains “insignificant”. The status is still “negative” and the confidence of the

assessment remains “high”. Table 9 presents the results of the assessment of Impact 1. .

Table 9: Impact 1a – Alien vegetation clearing and groundwater levels Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Medium Long term Medium Probable MEDIUM - ve High

(1) (2) (3) (6)

Essential Mitigation Measures:

Ensure the vegetation / plant material replacing the alien vegetation has a high evapotranspiration rate.

Correct design of the runway and taxiways and elevation of the runway and taxiways.

With mitigation

Local

(1)

Low

(1)

Long term

(3)

Low

(5) Possible VERY LOW - ve High

4.1.1.4 Statement of acceptability

The impact of the removal of the alien invasive vegetation, from the perspective of

groundwater levels, is acceptable, and is not a fatal flaw to the project.

4.1.2 Removal of alien vegetation and associated impact on groundwater quality (construction phase).

4.1.2.1 Description

The removal of alien vegetation is not considered to have a tangible negative impact on

groundwater quality. The removal of alien vegetation will result in increased groundwater

recharge and a possible improvement in groundwater quality (assuming no surface based

contamination). For this reason there are no mitigation measures applicable to the issue of

groundwater quality.

4.1.2.2 Proposed Mitigation Measures

No mitigation measures are required.


This impact is considered to be of low intensity and have long-term duration. The

consequence rating is thus “very low” (i.e. a score of 3). The probability is “probable” (i.e.

> 70% - 90% chance of occurring). The overall significance is thus “very low”. The status

is considered to be positive. The level of confidence associated with the assessment is



“high”. No mitigation measures need to be implemented. Table 10 presents the results of

the assessment of Impact 1 with regard to groundwater quality.

Table 10: Impact 1b – Alien vegetation clearing and groundwater quality Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Low Long term Low Probable LOW + ve High

(1) (1) (3) (5)


None

With mitigation

Local

(1)

Low

(1)

Long term

(3)

Low

(5) Probable LOW + ve High


The impact of the removal of the alien invasive vegetation, from a groundwater quality

perspective, is acceptable, and is not a fatal flaw to the project.

4.1.3 Impact on groundwater levels due to earthworks, ground surface levelling and runway construction (construction phase)

4.1.3.1 Description

Prior to the construction of the runway, earthworks will be required on the site which will

be post- alien vegetation removal (or possibly the two activities will run in parallel). The

earthworks will require extensive “cut and fill” to level the area. These levels have however

not yet been defined and will depend on the final groundwater levels and the cost of fill

material. The engineers have indicated that the final levels on the eastern side of the site

have not been determined and discussion with the project geohydrologist is necessary for

finalisation of the design. The airport runways and taxiways will also be constructed during

this phase. With the levelling process it is recommended the elevation of the ground

surface is kept as high as possible. In other words as shallow groundwater occurs in many

parts of the area in winter, the land surface must be as elevated as economically feasible in

order to avoid ponding. In addition, this is also applicable to the runway and taxiways as

well.

4.1.3.2 Proposed mitigation measures

There are no relevant mitigation measures.


With regard to this impact, the extent is “local”; the intensity is “local”; and the duration is

considered “medium term”. The consequence rating is thus “very low”. The probability

of this impact occurring is considered to be “possible” (i.e. 40 % – 70% chance of

occurring). The significance rating is thus “insignificant”. The impact will be negative if it

occurs and the assessment is completed with a “high” level of confidence.

As no mitigation measures are applicable the significance rating thus remains

“insignificant”. The impact will be negative if it occurs and the assessment is completed



with a “high” level of confidence. Table 11 lists the impact and associated rating, as well as

the rating with mitigation measures in place.

Table 11: Impact 2a – Impact of earth works and construction activities and groundwater levels

Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Local Medium

term Very low Possible

(40-70%) INSIGNIFICANT - ve High

(1) (1) (2) (4)


None

With mitigation

Local

(1)

Low

(1)

Short term

(1)

Very low

(3)

Improbable

(<40%) INSIGNIFICANT - ve High


The extensive earthworks planned for the site are not considered a fatal flaw to the project

and they are acceptable from a geohydrological point of view.

4.1.4 Impact on groundwater quality due to earthworks, ground surface levelling and runway construction (construction phase)

4.1.4.1 Description

During these earthwork activities the threat does exist of machinery leaking fuel and

lubricants onto the ground which may then contaminate groundwater. Even though the

groundwater is not planned to be used for domestic consumption, all measures should be

taken to prevent the contamination of the groundwater.


During the earthworks, it is imperative the equipment is well maintained so that there are

no leakages of fuel or lubricants. Where the vehicles are stored overnight they must be

parked on a hardened surface, otherwise drip trays and / or sand trays must be positioned

under the equipment. The filling of the vehicles with fuel must be done on a hardened

impermeable surface, preferably on concrete surface, so ensure no spillages enter the

ground. Service bays also need to be hardened, impermeable surfaces, also a concrete

surface is best. If any spillage occurs the impacted material must be removed and taken in

the proper manner to a hazardous landfill (Vissershok). One must be particularly vigilant

when mobile fuel trucks are used for filling heavy equipment. Operators must also be

trained and informed about the procedures should a spillage occur.


The shallow groundwater within the development footprint is saline and not suitable for

domestic use (this may well apply to the deeper aquifer as well) and high levels of localised

contamination are present in the CFA. It is still essential that the quality of the CFA (both

the perched and deeper aquifer) must be protected and further contamination prevented.



With regard to this impact, the extent is “local”; the intensity is “local”; and the duration is

considered “medium term”. The consequence rating is thus “very low”. The probability

of this impact occurring is considered to be “possible” (i.e. 40 % – 70% chance of

occurring). The significance rating is thus “insignificant”. The impact will be negative if it

occurs and the assessment is completed with a “medium” level of confidence.

With regard to the impact rating, taking into account mitigation measures, the large

construction companies do operate with high levels of awareness about contamination

prevention and the impacts are re-assessed below. The duration factor is reduced to “short

term” and the probability rating reduces to “improbable” (i.e. < 40 % chance of occurring).

The significance rating thus remains “insignificant”. The impact will be negative if it

occurs and the assessment is completed with a “high” level of confidence. Table 12 lists

the impact and associated rating, as well as the rating with mitigation measures in place.

Table 12: Impact 2b – Impact of earth works and construction activities and groundwater quality

Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Local Medium

term Very low Possible

(40-70%) INSIGNIFICANT - ve High

(1) (1) (2) (4)


Service the vehicles on an impermeable surface

Drip trays / sand trays must be placed under engines when stored overnight or for longer periods.

Filling of vehicles must be done on an impermeable surface.

Vehicles filled on site by a tanker must have a drip tray / sand tray placed beneath the filling nozzle.

All relevant staff must be made aware of trying to prevent spillages and leakages and then trained in the procedures to follow

up should a leak or spillage occur.

With mitigation

Local

(1)

Low

(1)

Short term

(1)

Very low

(3)

Improbable

(<40%) INSIGNIFICANT - ve High


The extensive earthworks planned for the site are not considered a fatal flaw to the project

and they are acceptable from a geohydrological point of view.

4.1.5 Impact of the presence of the runway and taxiways on groundwater levels (operational phase)

4.1.5.1 Description

The runway and taxiways are impermeable surfaces and this will reduce direct recharge to

groundwater beneath these surfaces. The recharge of the CFA taking place at the airport is

very small in comparison with the total aquifer recharge area of the CFA and will have an

extremely small impact. However the run-off from the runway and taxiway will be

concentrated along the edges of these surfaces. Where these “edges” occur above shallow

impermeable geological layers, the possibility for ponding to occur will increase. For the

airport this is a negative issue as it could lead to flooding of the runway and taxiways and



attract birds to the area. The planning of storm water run-off must be addressed by the

design engineers to adequately manage run-off from these areas.

The run-off water may also have a chemistry that is slightly different to natural rainwater

due to accumulation of tyre compounds on the surface from landing planes. This could

potentially impact groundwater quality.


The measures proposed by Naco-SSI (2008b) with regard to managing the edges of the

impermeable surfaces and avoidance of ponding are considered acceptable. These include:

Designing slopes of pavement and adjacent areas to create rainfall runoff flowing as

quickly as possible towards drainage inlet structures, without exceeding the

maximum allowable slopes for safe ground traffic and aircraft movement area, as

prescribed in the relevant design standards.

Designing structures for inlet, collection and storage of surface drainage runoff:

o Having sufficient capacity to collect, transport and store the resulting

volumes of water according to the agreed rainfall intensity-duration limits.

o Being structurally sufficiently strong to withstand static and dynamic loads

generated by critical aircraft, vehicles and equipment for the design life.

o Being installed so that all expected traffic will encounter no operational

obstruction or safety hazard.


The assessment is only applicable where runways, taxiways and impermeable surfaces

occur. The extent of the impact is local, of short intensity and of short duration. Table 13

summarizes the impacts for this factor.

Table 13: Impact 3a – Runway and taxiways and groundwater levels Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Local Short term

Very low Definite

(>90%) Very Low - ve High

(1) (1) (1) (3)


Include sub-surface drainage and storm water removal at the edges of impermeable surfaces where impermeable geological

layers are shallow.

With mitigation

Local

(1)

Low

(1)

Short term

(1)

Very low

(3)

Possible

(<40%) Very Low - ve High


The impact of the presence of the runway and taxiways on groundwater levels are

considered acceptable.



4.1.6 Impact of the presence of the runway and taxiways on groundwater quality (operational phase)

4.1.6.1 Description

The runway and taxiways are impermeable surfaces and thus will accumulate mainly rubber

compound from the wheels of the aircraft. This material and any others that may

accumulate will be washed off these surfaces during a rain event. The run-off from the

runway and taxiway will be concentrated along the edges of these surfaces and may result

in areas of localised groundwater recharge.


The assessment is only applicable where runways, taxiways and impermeable surfaces

occur. The extent of the impact is local, of short intensity and of short duration. Table 14

summarizes the impacts for this factor.

Table 14: Impact 3b – Runway and taxiways and groundwater quality Extent Intensity Duration Consequence Probability Significance Status Confidence

Without mitigation

Local Local Short term

Very low Definite


(1) (1) (1) (3)


None.

With mitigation

Local

(1)

Low

(1)

Short term

(1)

Very low

(3)

Definite



The impact of the presence of the runway and taxiways on groundwater quality are

considered acceptable.

4.2 Cumulative Impacts

It is expected that there will be no cumulative impacts from the presence of the runway

and taxiways on groundwater at the local, regional or national scale. The increased tarred

surface will result in localised increased storm run-off which must be managed, and the

removal of vegetation may result in a small increase in water levels. These are not

considered significant.

4.3 Indirect Impacts

There are no anticipated indirect impacts of the development on the groundwater of the

area. In addition it is assumed that existing fuel storage tanks will not be moved and the

current fuel storage facilities are not being changed, increased in capacity or moved.



5. CONCLUSION

It is concluded (and confirmed) that groundwater is very shallow beneath the study area

and the design engineers are well aware of this. The shallow, hard, laterally discontinuous

and impermeable calcrete (and sandstone) layers result in perched groundwater levels. This

is especially the situation in the wet winter months. The groundwater levels are particularly

shallow at the south-eastern and north-western ends of the proposed runway, and increase

towards the east as presented in Map 6 (Appendix A). These geological layers will result

in differential compaction of the site and these are the areas where flooding will occur if

the antecedent conditions are favourable in combination with a very heavy rainfall event.

The delineation of the calcrete layers (and causes for the perched aquifer conditions) is

considered important so that mitigation measures can be taken to avoid flooding of these

areas.

This specialist study has also addressed the concerns raised by Interested and Affected

Parties during the Scoping Phase of the project.

As there is no planned abstraction of groundwater, Section 21a of the National Water Act

is not applicable and it is likely that a Section 21a Water Use License Application is not

required from a groundwater perspective. This will be addressed and reviewed by the

Department of Water and Sanitation.

6. RECOMMENDATIONS

It is recommended that the levelling of the site be carried out with the objective to keep the

land surface as high above mean sea level as possible. In addition the runway and taxiways

need to be elevated above this level. Liaison with the project geohydrologist and design

engineers is necessary so that the optimal elevations can be decided upon.

It is important to ensure the groundwater is not contaminated during the construction or

operational phase.

Whether a long-term groundwater monitoring programme needs to be established or not

will be decided upon by the relevant authorities and should be in line with a risk based

approach.

7. ACKNOWLEDGEMENTS

The following are thanked for input to the project:

Sean Bradshaw (Airports Company South Africa) for sharing literature and his

knowledge of the area.

Sheila Imrie, Sharon Jones and Scott Mason (SRK) for providing a lot of literature

and insight into the project.



Simo Constantatos and Zaid Gangraker (GPT) for providing the groundwater level

and water quality (EC) data for the Airports Company South Africa monitoring

boreholes.

Dr Jaco Nel (GCS) for imparting his knowledge on the UWC boreholes.

Henry de Haast (DWA) for supplying the UWC logger data.

Jason Greeff (RoundOne Drilling Solutions) for sharing his geological knowledge

of the area.

8. REFERENCES

Arcus Gibb (2004). Geotechnical Site Investigation Report. Sub-soil drainage along the main runway

at Cape Town International Airport. Arcus Gibb Report J24245A. November 2004.

CSIR (2006). Report on Pilot Removal of Alien Invasive Vegetation at Cape Town International Airport and Monitoring and Modelling of Groundwater Levels. Authors: C. Colvin, D le Maitre, F. Rusinga and R. Campbell. Environmentek, CSIR, Stellenbosch.

DWAF (2000). 1:500 000 Hydrogeological Map Series, 3317 Cape Town, DWAF (2005). Groundwater Resource Assessment – Phase II (GRAII). Department of

Water Affairs and Forestry. Pretoria. GEOSS (2013). Geohydrological assessment of a proposed Belhar residential development. GEOSS

Report Number: 2013/07-18. GEOSS - Geohydrological and Spatial Solutions International (Pty) Ltd. Stellenbosch, South Africa.

Gerber (1976). An investigation into the hydraulic characteristics of the groundwater source in the Cape

Flats. MSc thesis, University of the Orange Free State.

GPT (2014). Groundwater sampling report for Cape Town International Airport. Geo Pollution

Technologies – Gauteng (Pty) Ltd. GPT Reference: ACCIA/13/671.

Naco-SSI (2008a). New re-aligned runway 18-36 and associated taxiways. Pavement Preliminary

Design Report. Document No 03. August 2008.

Naco-SSI (2008b). Drainage Preliminary Design Report. Document No 06. August 2008.

Naco-SSI (2010). New re-aligned runway 18-36 and associated taxiways. Hydrological Investigation

Report. Document No 11. February 2010.

Schulze R.E., Maharaj M., Warburton M.L., Gers C.J., Horan M.J.C., Kunz R.P., and Clark

D.J. (2008). South African Atlas of climatology and agrohydrology. Water

Research Commission 1489/1/08.

SAS (2014). Freshwater Ecological Assessment as part of the Environmental Assessment

and Authorisation Process for the proposed realignment of the primary Runway at

the Cape Town International Airport, Western Cape. Scientific Aquatic Services,

Pretoria.

SRK (2014). Cape Town International Airport Runway Re-alignment and Associated Infrastructure

Environmental Impact Assessment: Final Scoping Report. SRK Report Number

445354/03.

SRK, (2011). Feasibility Study on Groundwater Potential for Two Delft Primary Schools. SRK

project No. 438225.

SRTM (2000). The Shuttle Radar Topography Mission (http://www2.jpl.nasa.gov/srtm/).

National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and

Space Administration (NASA).

http://www2.jpl.nasa.gov/srtm/



Vandoolaeghe, M.A.C. (1989). The Cape Flats Groundwater Development Pilot Abstraction

Scheme. Trechnical Report Gh3655. Directorate Geohydrology, Department of

Water Affairs and Forestry, Pretoria.

Wright, A. and Conrad, J. (1995). The Cape Flats Aquifer, current status. Groundwater Programme, Watertek, CSIR, Report no 11/95.



9. APPENDIX A: MAPS



Map 1: Location of the Cape Town International Airport area within a regional setting



Map 2: The study site superimposed on a 1:50 000 topocadastral map, showing the GEOSS

auger sites and piezometer positions.



Map 3: The study site superimposed on an aerial photograph, showing the GEOSS auger sites and piezometer positions.



Map 4: Geological setting of the study area and NGA boreholes (Council for Geoscience map: 1:250 000 scale 3318 –Cape Town)



Map 5: Aquifer type and yield within the study area (DWA 1:500 000 scale 3317 Cape Town)



Map 6: Groundwater level as metres below ground level (base data is SRTM, 2000)



Map 7: Groundwater level as metres above mean sea level (base data is SRTM, 2000)



Map 8: Aquifer quality within the study area (DWA 1:500 000 scale 3317 Cape Town)



Map 9: Groundwater vulnerability within the study area (DWA, 2005)



10. APPENDIX B: LABORATORY RESULTS (CSIR)



11. APPENDIX C: SITE PHOTOS


Photo 1: Piezometer Site 01

Photo 2: The hard sandstone layer

encountered at the base of Piezometer Site 01

Photo 3: Piezometer Site 02

Photo 4: Auger Site 01



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