HYDROGEOLOGY STUDY FOR THE PROPOSED FUEL STATION, … · the weathering of chert and dolomite....
Transcript of HYDROGEOLOGY STUDY FOR THE PROPOSED FUEL STATION, … · the weathering of chert and dolomite....
HYDROGEOLOGY STUDY FOR THE PROPOSED FUEL STATION, ON PORTION 125 OF THE FARM WATERVAL 174 IQ, MOGALE CITY
Report Prepared for
Ntata Investment
Report Number 491398
Report Prepared by
June 2015
SRK Consulting: Project No: 498391 Hydrogeology of Portion 125 of Waterval 174 IQ Page i
MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
HYDROGEOLOGY STUDY FOR THE PROPOSED FUEL STATION, ON PORTION 125 OF THE FARM WATERVAL 174 IQ, MOGALE CITY
Ntata Investment
SRK Consulting (South Africa) (Pty) Ltd 265 Oxford Rd Illovo 2196 Johannesburg South Africa
e-mail: [email protected] website: www.srk.co.za
Tel: +27 (0) 11 441 1111 Fax: +27 (0) 11 880 8086
SRK Project Number 491398
June 2015
Compiled by: Peer Reviewed by:
Benedict Mabenge Pr Sci Nat Senior Hydrogeologist
Ismail Mahomed Pr Sci Nat Principal Hydrogeologist
Email: [email protected]
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Table of Contents
Disclaimer .................................................................................................................................................... iv
1 Introduction and Scope of Report .................. ............................................................. 1
1.1 Scope of Work ..................................................................................................................................... 1
2 Site Description .................................. .......................................................................... 1
2.1 Locality ................................................................................................................................................ 1
2.2 Climate ................................................................................................................................................ 3
2.3 Geology ............................................................................................................................................... 3
2.4 Hydrogeology ...................................................................................................................................... 5
2.4.1 Groundwater Levels ................................................................................................................ 5
2.4.2 Recharge ................................................................................................................................. 5
2.4.3 Groundwater Use .................................................................................................................... 5
3 Hydrogeological Investigations .................... .............................................................. 6
4 Program Results ................................... ........................................................................ 6
4.1 Site Visit and Hydrocensus ................................................................................................................. 6
4.2 Baseline Water Quality ....................................................................................................................... 9
5 Assessment of Impacts ............................. .................................................................. 9
5.1 Risk Assessment ................................................................................................................................. 9
5.2 Impacts Assessment ......................................................................................................................... 10
6 Conclusions and Recommendations ................... ..................................................... 12
6.1 Conclusions ....................................................................................................................................... 12
6.2 Recommendations ............................................................................................................................ 12
7 References ........................................ .......................................................................... 14
Appendices ........................................ .............................................................................. 15
Appendix A: Impact Assessment Methodology ..................... ..................................... 16
Appendix B: Laboratory Certificates ........................... ................................................ 21
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List of Tables Table 2-1. Summary of site geology ................................................................................................................... 3
Table 3-1. Summary of boreholes installed for geotechnical investigation ........................................................ 6
Table 4-1. Water Sources Identified During Hydrocensus ................................................................................. 7
Table 4-2. Laboratory Results ............................................................................................................................ 9
Table 5-1. Impacts Assessment ....................................................................................................................... 11
List of Figures Figure 2-1. Location of proposed filling station ................................................................................................... 2
Figure 2-2. Mean monthly precipitation .............................................................................................................. 3
Figure 2-3. Site geological map .......................................................................................................................... 4
Figure 4-1. Map showing locations of boreholes identified during hydrocensus ................................................ 8
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Disclaimer The opinions expressed in this Report have been based on the information supplied to SRK
Consulting (South Africa) (Pty) Ltd (SRK) by Ntata Investment (Ntata). The opinions in this Report
are provided in response to a specific request from Ntata to do so. SRK has exercised all due care
in reviewing the supplied information. Whilst SRK has compared key supplied data with expected
values, the accuracy of the results and conclusions from the review are entirely reliant on the accuracy and completeness of the supplied data. SRK does not accept responsibility for any errors
or omissions in the supplied information and does not accept any consequential liability arising from
commercial decisions or actions resulting from them. Opinions presented in this report apply to the
site conditions and features as they existed at the time of SRK’s investigations, and those
reasonably foreseeable. These opinions do not necessarily apply to conditions and features that may arise after the date of this Report, about which SRK had no prior knowledge nor had the
opportunity to evaluate.
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1 Introduction and Scope of Report Ntata Investment appointed SRK Consulting to complete a hydrogeological study at Portion 125 of
the Farm Waterval 174 IQ, Mogale City. The property lies in Tarlton, 12 km west of the town of
Krugersdorp. Ntata Investment is compiling an Environmental Impact Assessment (EIA) for the
establishment of a fuel service station on the property.
The objective of this study is to identify and rate the impacts associated with proposed development on groundwater.
The study area is located within quaternary catchment A21D and within the Crocodile West and
Marico Water Management Area.
1.1 Scope of Work We understood the scope of work to be as follows:
• Desktop study of existing available data;
• Hydrocensus and site visit;
• Review of gravimetric survey and borehole drilling information supplied by Geotechnical
Engineering study;
• Sampling of groundwater and baseline water quality assessment;
• Impacts assessment.
2 Site Description
2.1 Locality The property is situated at the junction of the R24 to Krugersdorp and a link road to the N14 highway
to Rustenburg (Figure 2-1). The proposed development will cover an area of 2.3 ha and will
comprise of a fuel filling station and a retail component - convenience store, fast food restaurant and parking facilities for long haul heavy vehicles. The area slopes very gently towards the east, with an
average elevation of 1623.5 metres above mean sea level (mamsl).
A small retail shop is currently situated in the eastern corner of the property. The property has
access to municipal water, but no municipal sewer. The local municipality is amicable to alternative
measures to be implemented to deal with sewerage (Tarlton Truckstop Development Business Plan, June 2015).
The general land use within the area is residential rural, comprising of residential plots and some
agriculture. The study site is flanked by a farm on the northern boundary, and a small filling station
(Baobab Filling Station) is situated 200 m to the northeast of the site.
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Figure 2-1. Location of proposed filling station
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2.2 Climate The area is characterised by a temperate climate, with a mean annual precipitation of 750 mm. Most
of the precipitation comprises of rainfall which falls during the warm summer months (Figure 2-2).
The average midday temperatures range from 16.6 °C in June to 26.4 °C in January.
Figure 2-2. Mean monthly precipitation
2.3 Geology The site is underlain by dolomites of the Malmani subgroup, of the Transvaal Supergroup
(Figure 2-3). Geotechnical test pits excavated to an average depth of 1.6 m at the site exposed a
surface colluvium of dark reddish brown silty fine sand underlain by a chert residuum derived from the weathering of chert and dolomite.
Three boreholes were drilled on the site for dolomite stability investigations. These boreholes
encountered the transition from highly weathered material to a leached and fresh dolomite at an
average depth of 39 m (Africa Exposed, 2015). A summary of the site geology exhibited in the boreholes is shown in Table 2-1.
Table 2-1. Summary of site geology
Depth (mbgl) Description
0.0 – 7.0 Silty SAND and GRAVEL: Light reddish brown, silty fine sand with occasional gravel. Colluvium
7.0 – 13.0 Silty clayey SAND and FERRICRETE: Reddish to orangish brown silty and clayey sand with several angular ferricrete nodules
13.0 – 31.0 CHERT RESIDUUM: Dark orangey brown mottled white and red silty sand and weathered chert fragments
31.0 – 39.0 CHERT and WAD: Dark greyish brown to black mottled white clayey silt (wad) approx. 10-15%, with many angular weathered chert fragments
39.0 – 50.0 LEACHED DOLOMITE: Abundant angular slightly weathered chert and leached dolomite fragments in a matrix (5-15%) of dark grey silty clay
50.0 – 61.0 DOLOMITE: Light grey, slightly weathered to fresh dolomite
0
20
40
60
80
100
120
140
160
Rai
nfal
l (m
m)
Mean Monthly Precipitation
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Figure 2-3. Site geological map
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A gravity survey was carried out as part of the dolomite study and concluded that the site poses a
medium level risk of sinkhole and doline formation (Africa Exposed, 2015). The survey established
that no receptacles or open voids exist within the shallow weathered material, nor in the dolomite bedrock. Karsts are however known to be present in the region.
2.4 Hydrogeology The aquifers underlying the region are associated with the highly weathered zone, karst cavities,
fractures and joints within the chert and dolomite. Dolomites constitute some of the most important
aquifers in South Africa, with recharge values of between 9 and 13%. Groundwater yields are
excellent, and 50% of boreholes yield more than 5 L/s (DWS). The groundwater quality within the dolomites is typically of a calcium-magnesium-bicarbonate nature and generally of acceptable quality
for a variety of uses including drinking.
The presence of interconnected karst, fractures and joint systems within the dolomites makes the
aquifers vulnerable to pollution and allows the rapid migration of contaminants. The karst aquifers
are characterised by modest (<100 m2/d) to extremely high (>1000 m2/d) transmissivity values and moderate storativity values (Bredenkamp et al, 1986). Boreholes drilled for the dolomite study did not
intersect any open receptacles or voids within the weathered zone. Wad associated with Karst is
however present.
2.4.1 Groundwater Levels
Data sourced from the National Groundwater Archives (NGA) shows that the groundwater levels within a 1 km radius of the site vary from 6.7 metres below ground level (mbgl) to 59.82 mbgl. The
NGA data also shows that groundwater was intersected at depths ranging from 6.7 mbgl to 78 mbgl.
During the drilling of three dolomite study boreholes on the site groundwater was intersected at
depths of 28 to 30 mbgl. Interpolation of the groundwater level data shows that the groundwater
flows in a north easterly direction across the site.
2.4.2 Recharge
Groundwater recharge for the area is estimated at 11 % of MAP (Vegter, 1992), or approximately
81 mm of rainwater per annum percolating through the weathered zone to reach the groundwater
table.
2.4.3 Groundwater Use
The major groundwater users within the immediate vicinity of the proposed development are the Levante farm, to the north, which uses groundwater for irrigation and the Baobab filling station for
their domestic and industrial use. The residential properties along the R24 to the east of the site
largely use municipal water and use groundwater as backup for domestic purposes.
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3 Hydrogeological Investigations A site visit was carried out on the 8th of June 2015 and was undertaken with the assistance of
personnel from Ntata Investment. The SRK hydrogeologist made a visual assessment of the site,
carried out a limited hydrocensus of surrounding groundwater users and collected three samples for
hydrocarbon analysis.
Three, 165 mm diameter, boreholes (Table 3-1) drilled during the geotechnical and dolomite studies were inspected and found to have collapsed as no casing had been installed following completion.
Ntata Investment provided the geotechnical and dolomite study reports that were compiled by Africa
Exposed in May and June 2015. Geological logs of these boreholes were provided with the reports.
Table 3-1. Summary of boreholes installed for geote chnical investigation
BH ID Locality X (m)
Y (m)
Drilled Depth (m)
Current Depth (m)
Water strike (mbgl)
Comments
VW1 Study Site 2880402 -0699156 54 16 28
Geotech holes, drilled 40m, collapsed, could not sample groundwater
VW2 Study Site 2880402 -069145 61 5 30
VW3 Study Site 2880466 -069151 56 6 30
4 Program Results
4.1 Site Visit and Hydrocensus The hydrocensus carried out within the vicinity of the site found that the majority of the households in
the area rely on the local municipality for their water supply. Some of the properties, however, have boreholes which provide a backup supply of water and used to water gardens. The Levante farm,
which is north west of the site, has a borehole that is used to provide water for irrigation. Access to a
number of the properties was a challenge as residents were absent, however the expectation is that
many of the residential and agricultural plots located to the north of the site have boreholes.
A summary of boreholes located on the surrounding properties is given in Table 4-1 and shown on
Figure 4-1. The depth to water level could not be measured in any of the boreholes visited as pumps
are installed. Water samples were collected in 100 ml and 500 ml glass bottles from three of the
boreholes visited. The samples were stored in a cooler box with ice packs until delivery to laboratory.
Basic water quality parameters were measured on-site before the collection of each water sample. No purging of the boreholes was necessary as all three boreholes were pumping at the time of
sampling.
No sheen or visual evidence of hydrocarbons was observed in any of the samples collected. The
Baobab filling station borehole valve is housed in a manhole box into which dirty contaminated water
from surface flows. A small amount of water was present in the manhole. The raising main from the borehole is sealed to prevent the contaminated water from flowing into the borehole.
Field Electrical Conductivity (EC) measurements ranged from 21.7 to 28.4 mS/m and the
groundwater is alkaline with a pH range of 8.4 to 9.2. The alkaline pH of the groundwater is typical of
groundwater from a dolomitic aquifer and the EC is well within the drinking water limit of 70 mS/m.
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Table 4-1. Water Sources Identified During Hydrocen sus
BH ID Locality X (m)
Y (m)
EC (mS/m) pH Temp
(°C) Water use Distance from site
(m)
BH4 Levante Farm 2888207 -068847 21.7 9.2 19.7 Irrigation 400
BH5 Baobab Filling Station 2888185 -069088 25.3 8.4 20.1 Domestic 300
BH6 VO School 2888228 -069237 - - - Disused 300
BH7 Plot H28 2888354 -069469 28.4 8.6 14.5 Domestic 300
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Figure 4-1. Map showing locations of boreholes iden tified during hydrocensus
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4.2 Baseline Water Quality The water samples were submitted to M & L Laboratory Services for hydrocarbon content analysis.
The samples were analysed for Total Petroleum Hydrocarbons (TPH), Benzene, Toluene,
Ethylbenzene, Xylenes and Naphthalene (BTEXN) compounds. TAME and MTBE concentrations
were also measured during the analysis. Table 4-2 shows a summary of the laboratory results. The laboratory certificates are attached in Appendix B.
All the organic parameters analysed were found to be within the recommended limits by the United
States of America Environmental Protection Agency (US EPA)1. The alkaline pH measured in the
water suggests that the water is abstracted from the deep dolomite aquifer. The laboratory results indicate that the groundwater within the immediate vicinity of the proposed development site has not
been impacted by hydrocarbon fuels.
Table 4-2. Laboratory Results
Parameter BH4 BH5 BH7 USA EPA Limit (µg/L)
Date Sampled---> 08/06/2015 08/06/2015 08/06/2015
C10-C12 (µg/L) <2 <2 <2 7
C12-C22 (µg/L) <26 <26 <26 86
C22-C30 (µg/L) <13 <13 <13 42
C30-C40 (µg/L) <62 <62 <62 208
Total C10-C40 (ug/l) <103 <103 <103
GRO-C6-C10 (µg/L) <3 <3 <3 11
Benzene (µg/L) <1 <1 <1 1
Ethylbenzene (µg/L) <1 <1 <1 1
MTBE (µg/L) <1 <1 <1 3
Naphthalene (µg/L) <1 <1 <1 2
O-Xylene (µg/L) <1 <1 <1 1
TAME (µg/L) <1 <1 <1 1
Toluene (µg/L) <1 <1 <1 1
m/p-Xylene (µg/L) <1 <1 <1 1
5 Assessment of Impacts The impact assessment was carried out according to the methodology laid out in Appendix A.
The first step of the assessment is to carry out a risk assessment and identify the potential sources
of contamination, contaminant pathways and receptors.
5.1 Risk Assessment A risk assessment entails the evaluation of Source-Pathway-Receptor (S-P-R) linkage. The risk level
is defined by the completeness of the S-P-R linkage together with the severity of the impact:
• High : S-P-R linkage is proven to be complete
• Medium : S-P-R linkage is suspected but not proven
• Low : S-P-R linkage is complete but severity of impact is negligible, or S-P-R linkage is
incomplete and there is no foreseeable mechanism by which it could be realised
1 Note there are no South Africa guideline limits for these compounds
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For the study site, the following S-P-R linkage is defined as follows:
• The potential source of contamination will be the fuel from leaks of the underground storage tanks (USTs), associated pipework and relevant filling station surface infrastructure. Sewage
disposal via spectic and French drains if used could also be a source of contamination.;
• Potential pathways for the contamination will be the groundwater via the weathered zone and karst/fractures or joints aquifers;
• The receptors are residential users who abstract boreholes for potable use to the eastern side of the site and the farm on the north.
The risk of groundwater contamination is rated as High as the S-P-R linkage for the site is proven.
5.2 Impacts Assessment Any leakage from the underground fuel tanks and spillages from surface connections may reach the
unsaturated zone and be leached down to the water table. This would contaminate the groundwater
with hydrocarbons and users could be exposed. Percolation of contaminates from the sewage disposal, if on-site, could also occur. Abstraction form pumping boreholes could also draw
contaminants towards the supply boreholes.
The impact of the operation of the filling station on the groundwater quality is rated Medium High but
can be mitigated to reduce the potential impacts (see Table 5-1).
Mitigating these impacts require that the construction of the tank farm to contain any leakages, safeguards be implemented to prevent spills and leaks and in the event these occur, the impacts of
any spills be limited.
The excavation, installation and maintenance of the underground storage tanks must follow the
relevant SABS standards, including:
• SANS 10089-3: The petroleum industry Part 3: The installation, modification, and
decommissioning of underground storage tanks, pumps/dispensers and pipework at service
stations and consumer installations
• SANS 50858-1: Separator systems for light liquids (e.g. oil and petrol) Part 1: Principles of
product design, performance and testing, marking and quality control
• SANS 50858-2: Separator systems for light liquids (e.g. oil and petrol) Part 2: Selection of nominal size, installation, operation and maintenance
It worth highlighting that a HDPE liner would need to be installed within the tank farm and that all
stormwater from the forecourt area is controlled and directed to an oil/water separator and compiles with municipal by-laws and SANS guidelines, The discharge from the oil/water separator must be
directed to sewer line or disposed in an acceptable manner.
Careful daily wet stock reconciliation and at least monthly or when leaks are suspected inspection of
tank farm wells is required to identify any leakages quickly.
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Table 5-1. Impacts Assessment
Potential impact Activity
Environmental Significance Before Mitigation Recommended
mitigation measures / Remarks
Environmental Significance After Mitigation
S SS D FA FI SIG Rating S SS D FA FI SIG Rating
Impact on groundwater quality
Storage and dispensing of fuel 4 3 4 4 4 88 MH
Construction (HDPE lined, backfill & concrete slabs etc.) of tank farms. Jacketed tanks and spill containment at dispensers etc.. Clean up protocols for all spillages
4 1 4 4 2 54 L
Surface run-off from forecourt
4 3 4 2 4 66 ML
Install hardstanding, stormwater drainage and oil\water separator Appropriate Clean up all spillages
4 2 4 2 3 50 L
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6 Conclusions and Recommendations
6.1 Conclusions The following were concluded from the desktop study, the site visit and the laboratory results:
• The aquifers underlying the region are predominantly karstic and associated fracturing and
jointing, with modest to high transmissivity values and modest storativity. Any contaminant
introduced into the subsurface could migrate rapidly to the domestic water users located 300 m down gradient of the site;
• The groundwater within the immediate vicinity of the site is generally of acceptable quality
for a variety of purposes. All the organic parameters analysed were found to be within the recommended limits by the United States of America Environmental Protection Agency (US
EPA), indicating that no historical contamination is evident. No contamination from the
service station located 200 m and to the north is evident.
• The impact to the groundwater quality of the operation of the filling station is rated as Medium High but can be mitigated by complying with industry good practice and the
relevant SANS standards for UST installations.
6.2 Recommendations We recommend the following:
• Implement good practices and good housekeeping during all phases of the project to limit the impacts of leakages and spills.
• A HDPE liner would need to be installed within the tank farm and stringent application of stormwater and leak detection measures would need to be applied.
• Implement and follow measures to prevent and detect leaks as detailed in SANS standards and fuel industry construction protocols. These include amongst others:
o Lined tank farm, jacketed tanks and delivery pipes which are capable of
withstanding the high positive pressure (400 kPa to 1000 kPa);
o Electronic leak detection measures;
o Hardstanding and stormwater drainage;
o Daily wet stock reconciliation;
o At least monthly inspection of monitoring well that will be installed around the tank
farm;
o Annual pressure testing of infrastructure,
o Effective housekeeping and effective protocols for responding to spills and leaks etc.
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Prepared by
Benedict Mabenge Pr.Sci.Nat
Senior Hydrogeologist
Reviewed by
Ismail Mahomed Pr.Sci.Nat
Principal Hydrogeologist
Reviewed by
Peter Shepherd. Pr.Sci.Nat
Principal Hydrologist & Partner
All data used as source material plus the text, tables, figures, and attachments of this document
have been reviewed and prepared in accordance with generally accepted professional engineering and environmental practices.
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7 References Africa Exposed. Dolomite Stability Investigation Report: Portion 125 Of The Farm Waterval 174 IQ
Mogale City (2015)
Africa Exposed. Engineering Geological Investigation Report: Portion 125 Of The Farm Waterval 174
IQ Mogale City (2015)
Bredenkamp D.B, Van der Westhuizen C, Weigmans F.E and Kuhn C. Groundwater Supply Potential of Dolomite Compartments West of Krugersdorp. Report No. GH3440. Directorate
Geohydrology. Department of Water Affairs & Forestry. (1986)
South African National Groundwater Archives (2015)
Vegter J.R & Seymour A.J. Saturated Interstices, Mean Annual Recharge and Depth to Groundwater
Level maps. Department of Water Affairs & Forestry (1992)
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Appendices
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Appendix A: Impact Assessment Methodology
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Impact assessment methodology
The first stage of impact assessment is the identification of environmental activities, aspects and
impacts. This is supported by the identification of receptors and resources, which allows for an
understanding of the impact pathway and an assessment of the sensitivity to change. The following definitions therefore apply:
• An “Activity” is defined as a distinct process or risk undertaken by an organisation for which
a responsibility can be assigned. Activities also include facilities or pieces of infrastructure that are possessed by an organisation;
• An environmental “Aspect” is an element of an organisation’s activities, products and
services which can interact with the environment. The interaction of an aspect with the environment may result in an impact.
• Environmental “Impacts” are the consequences of these aspects on environmental
resources or receptors of particular value, sensitivity, for example, disturbance due to noise and health effects due to poorer air quality. Receptors can comprise, but are not limited to,
people or human-made systems, such as local residents, communities and social
infrastructure, as well as components of the biophysical environment such as aquifers, flora
and palaeontology. Impacts on the environment can lead to changes in existing conditions; the impacts can be direct, indirect or cumulative. Direct impacts refer to changes in
environmental components that result from direct cause-effect consequences of interactions
between the environment and development activities. Indirect impacts result from cause-
effect consequences of interactions between the environment and direct impacts.
Cumulative impacts refer to the accumulation of changes to the environment caused by human activities.
Description of the Aspects and Potential Impacts
The cumulative knowledge of the findings of the environmental investigations forms the basis for the
prediction of impacts. Once a potential impact has been determined it is necessary to identify which
development activity will cause the impacts, the probability of occurrence of the impact, and its magnitude and extent. This information is important for evaluating the significance of the impact, and
for determining mitigation and monitoring strategies.
The assessment of significance should be undertaken twice. Initial significance should be based on
only natural and existing mitigation measures (including built-in engineering designs). The subsequent assessment should take into account the recommended management measures
required to mitigate the impacts.
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Table A1. Criteria for assessing significance of im pacts
SEVERITY OF IMPACT RATING
Insignificant / non-harmful 1
Small / potentially harmful 2
Significant / slightly harmful 3
Great / harmful 4
Disastrous / extremely harmful 5
SPATIAL SCOPE OF IMPACT RATING
Activity specific 1
Right-of-way specific (within right-of-way) 2
Local area (within 5 km of filling station) 3
Regional 4
National 5
DURATION OF IMPACT RATING
One day to one month 1
One month to one year 2
One year to ten years 3
Life of operation 4
Post closure / permanent 5
FREQUENCY OF ACTIVITY / DURATION OF ASPECT
RATING
Annually or less / low 1
6 monthly / temporary 2
Monthly / infrequent 3
Weekly / life of operation / regularly / likely 4
Daily / permanent / high 5
FREQUENCY OF IMPACT RATING
Almost never / almost impossible 1
Very seldom / highly unlikely 2
Infrequent / unlikely / seldom 3
Often / regularly / likely / possible 4
Daily / highly likely / definitely 5 The method as described above is further explained in the following section in order to give a better understanding on how the Likelihood and Significance of an impact is identified. Attributes contributing to the significance and likelihood will be explained below: a. Spatial Scope: The spatial scope can be defined as the geographical coverage, and will take into account the following factors:
• The physical extent/distribution of the aspect, receptor and proposed impact; and
• The nature of the baseline environment within the area of impact.
For example, the impact of noise is more likely to be confined to a smaller geographical area than that of air emissions, which may be experienced at some distance. The significance of an impact varies spatially. Many will be significant only within the immediate vicinity of the site or within the surrounding community, while others may be significant at a regional or national level.
CONSEQUENCE
LIKELIHOOD
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b. Duration Duration refers to the length of time that the aspect may cause a change, either positive or negative, on the environment. The environment assessment methodology distinguishes between different time periods by assigning a rating to the duration of an impact. c. Severity The severity of an environmental aspect is determined by the degree of change to the baseline environment and includes consideration of the following factors:
• The reversibility of the impact;
• The sensitivity of the receptors to the stressor;
• The impact duration, its permanency and whether it increases or decreases with time;
• Whether the aspect is controversial or would set a precedent; and
• The threat to environmental and health standards and objectives.
d. Frequency of Activity The frequency of an activity refers to how regularly the activity takes place. The more frequently the activity takes place, the higher potential there is for a related impact to occur. e. Frequency of Impact The frequency of an impact refers to how often the aspect impacts, or may impact, either positively or negatively, on the environment. f. Additional Variables There are additional variables that must be taken into consideration when assessing the impacts of the proposed project. These variables will have a bearing on the significance of the impacts being assessed. These variables may include cumulative impacts and inputs received from I&AP’s. In scenarios where this is applicable, more emphasis will be placed on the management measure requirements. Cumulative and Impact identified by I&AP’s are discussed below:
• Cumulative impacts: These are impacts which are considered where off-site activities take place together with activities associated with the proposed project, resulting in a cumulative
impact imposed on the environment.
• Impacts/Issues raised by I&AP’s: I&AP’s will be consulted during the entire process of the EIA/EMP. Issues and concerns may be raised by the I&AP’s which will bear more weight in
the significance of the impact being assessed.
Determining the Impact Rating This rating methodology is used to evaluate the importance of a particular impact, the consequence and likelihood. The significance of the impact is assessed by rating each variable numerically according to defined criteria as outlined in Table A1. The purpose of the rating is to develop a clear understanding of influences and processes associated with each impact. The severity, spatial scope and duration of the impact together comprise the consequence of the impact and when summed can obtain a maximum value of 15. The frequency of the activity and the frequency of the impact together comprise the likelihood of the impact occurring and can obtain a maximum value of 10. The values for likelihood and consequence of the impact are then read off a significance rating matrix as shown in Table A2.
SRK Consulting: Project No: 491398 Hydrogeology of Portion 125 of Waterval 174 IQ Page 20
MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
Table A2. Interpretation of Impact Rating
Consequence
Like
lihoo
d
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
SIGNIFICANCE = CONSEQUENCE X LIKELIHOOD
The model outcome as determined from Table A2 is then assessed in terms of impact certainty and consideration of available information. Where a particular variable requires weighing or an additional variable requires consideration the model is adjusted accordingly. The numerical rating is determined through the use of Table A2. The colour code from Table A2 corresponding to Table A3 is then used to determine the appropriate level of mitigation that will be required to reduce the current rating.
Table A3. Positive/Negative Mitigation Ratings
Colour Code
Significance Rating Value
Negative Impact Management Recommendation
Positive Impact Management Recommendation
Very high 125-150
Improve current management
Maintain current management
High 101-125
Improve current management
Maintain current management
Medium High 76-100
Improve current management
Maintain current management
Medium Low 51-75 Maintain current
management Improve current management
Low 25-50
Maintain current management
Improve current management
Very Low 1-25
Maintain current management
Improve current management
Mitigation In assessing the significance of an impact, natural and existing mitigation is taken into account. Natural and existing mitigation measures are defined as natural conditions, conditions inherent to the development design and existing management measures that alleviate impacts. The significance of impacts is assessed taking into account any mitigation measures that are proposed. An EMP, specifying the methods and procedures for managing the environmental impacts of the proposed development, during all phases has been compiled and will be submitted to the competent authority following the final review period.
SRK Consulting: Project No: 491398 Hydrogeology of Portion 125 of Waterval 174 IQ Page 21
MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
Appendix B: Laboratory Certificates
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MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
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MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
SRK Consulting: Project No: 491398 Hydrogeology of Portion 125 of Waterval 174 IQ Page 24
MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
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MABB/MAHO Hydrogeology Study of Portion 125 of Waterval 174 IQ June 2015
SRK Report Distribution Record
Report No. 491398
Copy No. 1
Name/Title Company Copy Date Authorised by
Raveen Ramlakan Ntata Investments 1 01/07/2015
Janavi Jardine Azzuro Environmental 1 01/07/2015
SRK Library SRK 1 01/07/2015
Approval Signature:
This report is protected by copyright vested in SRK (SA) (Pty) Ltd. It may not be reproduced or
transmitted in any form or by any means whatsoever to any person without the written permission of
the copyright holder, SRK.