CHAPTER 9fred.csir.co.za/project/smelter/eia_final_chapter_9.pdf · proposed aluminium pechiney...

PROPOSED ALUMINIUM PECHINEY SMELTER WITHIN THE COEGA IDZ

CHAPTER 9:

FINAL ENVIRONMENTAL IMPACT REPORT CSIR, 2002

IMPACT ASSESSMENT AND MITIGATION: WATER USE AND

LIQUID WASTE


Contents

9. IMPACT ASSESSMENT AND MITIGATION: WATER USE AND LIQUID WASTE ______________________________________________________ 9-1

9.1 Introduction: approach and methodology ____________________________9-1 9.2 Identification of sources of impacts from the smelter project____________9-2

9.2.1 Water Use ___________________________________________________________ 9-2 9.2.2 Wastewater discharge__________________________________________________ 9-4

9.3 Identification of applicable legislation, guidelines and standards ________9-5 9.3.1 Registration of water use _______________________________________________ 9-6 9.3.2 Water use licencing and authorisation _____________________________________ 9-6 9.3.3 Guidelines and standards _______________________________________________ 9-8

9.4 Characteristics of the receiving environment ________________________9-10 9.4.1 Coega River ________________________________________________________ 9-10 9.4.2 Geology and groundwater _____________________________________________ 9-11

9.5 Scenarios considered in the impact assessment _____________________9-12 9.6 Design alternatives considered in the impact assessment _____________9-12 9.7 Impact assessment and mitigation_________________________________9-15

9.7.1 Water use during construction __________________________________________ 9-15 9.7.2 Water use during operation ____________________________________________ 9-15 9.7.3 Wastewater generated during construction ________________________________ 9-17 9.7.4 Wastewater generated during operation __________________________________ 9-18 9.7.5 Potential impacts on groundwater _______________________________________ 9-23 9.7.6 Identification of the best practicable environmental option (BPEO) _____________ 9-25

9.8 Monitoring recommendations_____________________________________9-26 9.9 Water licence requirements_______________________________________9-26 9.10 Summary of impacts and mitigation________________________________9-27

List of Figures Figure 9.1: Overview of water balance for smelter during operation ________________ 9-3 Figure 9.2: Proposed stormwater management system for the smelter site ___________ 9-14



List of Tables Table 9.1: Water use – required volumes and quality ___________________________ 9-2 Table 9.2: Aluminium Pechiney smelter wastewater characterisation _______________ 9-4 Table 9.3: Typical process wastewater composition_____________________________ 9-5 Table 9.4: Wastewater limit values applicable to discharge of wastewater into a water

resource ______________________________________________________ 9-7 Table 9.5: South African Water Quality Guidelines for aquatic ecosystems __________ 9-9 Table 9.6: Estimated fluoride concentrations in stormwater for six operating

scenarios ____________________________________________________ 9-21 Table 9.7: Identification of water licence requirements for the stormwater management

system_______________________________________________________ 9-27


Table 9.8: Summary impact assessment of water use and liquid waste of the proposed aluminium smelter _____________________________________________ 9-29


9. IMPACT ASSESSMENT AND MITIGATION: WATER USE AND LIQUID WASTE This chapter is based on the Water use and liquid waste specialist study by De Souza and Mackintosh (2002), undertaken for this EIA. Additional inputs on groundwater were provided by Dr Lisa Cavé of the CSIR.

9.1 Introduction: approach and methodology The primary objective of the water study is to identify the significance of possible environmental impacts of water use (during construction and operation), domestic sewage discharge, process wastewater discharge and contaminated stormwater discharge from the proposed aluminium smelter site. In doing so, the study considered water from two perspectives:

1. Water usage – where the total volumes and sources of water use at the proposed plant were considered; and

2. Water release – where the implications of discharging liquid waste and stormwater to the local receiving environment were evaluated.

The significance of possible environmental impacts of water use, discharge of domestic and process wastewater and of contaminated stormwater from the proposed aluminium smelter, were considered. Based on the experience at other smelters, a particular issue of concern was the impact of fluoride deposition on stormwater quality. The planning and design of the stormwater system for the smelter site and the overall IDZ site is at an early stage. In order to assess the possible water quality implications it was therefore necessary to develop a number of representative scenarios. This enabled a quantitative analysis of the compliance of the proposed wastewater and stormwater management system with appropriate water quality guidelines under different operating conditions. Results of the Air quality study (Chapter 7) were used to estimate the potential fluoride concentrations in stormwater. “Worst case” scenarios were then used to determine the significance of impacts. Based on the significance of impacts, recommendations have been made regarding mitigation measures, environmental management and monitoring.


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9.2 Identification of sources of impacts from the smelter project 9.2.1 Water Use

The expected water use for the various stages of the proposed smelter project are provided in Table 9.1. Table 9.1: Water use – required volumes and quality

Phase Water volume requirement Water quality requirement Preliminary earthworks 2 ℓ/s Drinking-water standards Smelter construction 144 000 m3/yr Drinking-water standards required for

construction personnel Quality required for concrete, compaction, dust control not specified

Smelter construction (for cathode sealing)

Min. emergency flow of 10 m3/hr pH 7 – 8 Hardness < 150 mg/ℓ as CaCO3 Alkalinity < 60 mg/ℓ as CaCO3 Conductivity < 1 000 µS/cm Chloride < 100 mg/ℓ

Smelter operation – drinking water

80 000 m3/yr Drinking-water standards

Smelter operation – process water

500 000 m3/yr pH 7 – 8 Hardness < 150 mg/ℓ as CaCO3 Alkalinity < 60 mg/ℓ as CaCO3 Conductivity < 1 000 µS/cm Chloride < 100 mg/ℓ

Fire fighting water 400 m3/hr during 1 hour Not specified

The current potable water consumption and disposal designs are summarised by the following diagram (Figure 9.1):


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Disposal Options

(1) Co-disposal with stormwater (proposed option)

(2) Treatment & re-use (under investigation)

(3) Disposal to NMMM sewerage network

(4) Disposal to IDZ industrial water recycling plant (future potential option)

Process wastewater (300 000 m3/year)

Evaporation (200 000 m3/year)

Cooling System (e.g. casthouse & compressors)

Process water input (500 000 m3/year)

Disposal to NMMM sewerage network (80 000 m3/year)

Domestic use (e.g. washing & drinking)

Domestic water input (80 000 m3/year)

Figure 9.1: Overview of water balance for smelter during operation


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9.2.2 Wastewater discharge

Wastewater to be discharged from the smelter each month includes domestic wastewater, process wastewater and stormwater. Expected quantities are described in Table 9.2.

Table 9.2: Aluminium Pechiney smelter wastewater characterisation

Wastewater stream Quantity (m3/year) Description

Domestic wastewater 80 000 Sewage effluent generated on the plant

Process wastewater 300 000 Wastewater from the cooling system in the casthouse and compressors (blowdown water)

Stormwater Varies

according to rainfall

Fluoride contaminated stormwater

Domestic wastewater

It is proposed that domestic wastewater generated will be discharged into the municipal sewer network for treatment at the municipal wastewater treatment plant. Initially the IDZ effluent will be sent to the Fish Water Flats treatment works, which has the spare capacity to treat this effluent. Later, as volumes of the IDZ effluent increase a new treatment works will be built within the IDZ.

Process wastewater Most of the process wastewater originates from cooling water used throughout the plant for the cooling of cast aluminium products. Wastewater from these circuits is generated to maintain a constant dissolved minerals content (water hardness), by balancing the concentrating effects caused by water evaporation losses through addition of an excess of fresh water above evaporation makeup demand. In effect, a constant minerals concentration cycle is established and maintained in the cooling water circuits through adjustment of this discharge (termed “blowdown” or “purge” water), within technical specifications. A small proportion of the cooling water is therefore drawn off, resulting in a process wastewater, which Aluminium Pechiney has noted, has the characteristics as presented in Table 9.3 below.


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Table 9.3: Typical process wastewater composition

Parameter Concentration Fluoride (mg/ℓ ) 2 – 6 PH 6,5 – 9,5 Oil and grease (mg/ℓ ) < 10 Suspended solids (mg/ℓ ) < 30

Stormwater

Stormwater contamination can be expected to arise from: Deposition (“fallout”) from the smelter fluoride emissions into the atmosphere.

Accidental or other spillages of fluorinated materials, oils, litter, etc. Discharge of process wastewater into the stormwater system.

Data provided by Aluminium Pechiney on the stormwater quality from several Pechiney smelter sites showed that the constituents of primary concern include zinc, aluminium and fluoride. The predicted levels based on this synthesis are:

Zinc. An average zinc concentration of 0,66 mg/ℓ (total) is noted. Aluminium. An average aluminium concentration of 9 mg/ℓ is noted. This data reflects Total Concentrations (i.e. the sum of both dissolved and particulate aluminium). The latter will have no environmental impact, whilst the former has environmental significance. Fluoride. An average fluoride concentration of 21,3 mg/ℓ is noted.

These levels for zinc and aluminium are unexpectedly high. It is worth noting that other smelters in South Africa using Pechiney technology have not recorded such high average levels.

While the magnitude and frequency of fluorinated material spillages on the site is difficult to model/predict in a meaningful manner, experience at other South African aluminium smelters has shown that this source can contribute from 10 mg/ℓ to 50 mg/ℓ of fluoride to stormwater.

9.3 Identification of applicable legislation, guidelines and standards Water use, taking into account both water extraction and release, is controlled by the National Water Act 36 of 1998, which protects all water resources countrywide, including both surface and groundwater. The enforcing authority is the Department of Water Affairs and Forestry (DWAF). The National Water Act identifies the following as uses of water relevant to the proposed project:

Utilization of water from a water resource;


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Discharging of liquid waste or water containing waste into a water resource through a pipe, canal, sewer or other conduit;

Disposing of waste in a manner that may be detrimental to the water resource.

9.3.1 Registration of water use

The proposed project will obtain water from the Nelson Mandela Metropole (NMMM) Municipality. Therefore, Aluminium Pechiney does not need to register its water use requirement. In this case, the water services provider will need to register the water use with DWAF.

9.3.2 Water use licencing and authorisation Licenses are not required (Section 22) where the use is permissible under a General Authorisation, or where a responsible authority has waived the need for a licence. The latter occurs when the authority is satisfied that the purpose of the Act will be served by an authorisation under any other law. The authorisation permitted replaces the need for a water user to apply for a licence in terms of the National Water Act if the water use is within the limits and conditions set out in the authorisation. The intention of the General Authorisation is to allow water use which has a small or insignificant impact on a water resource to take place without a licence. The Director-General of DWAF has issued a General Authorisation in respect of water uses, where need for a licence is not required:

Taking of water from a water resource and storage of water.

Engaging in a controlled activity, identified as such in section 37(1), namely irrigation of any land with waste or water containing waste generated through any industrial activity or by waterworks.

Discharging of waste or water containing waste into a water resource through a pipe, canal, sewer, or other conduit or discharging water from an industrial or power generation process.

The General Authorisation provides information regarding discharge of wastewater into a water resource. Wastewater limit values applicable to the discharge of wastewater into a water resource are shown in Table 9.4.


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Table 9.4: Wastewater limit values applicable to discharge of wastewater into a water resource

Parameter General limit Special limit Faecal coliforms (per 100 mℓ) 1000 0 Chemical Oxygen Demand (mg/ℓ) (after removal of algae)

75 30

PH 5,5 – 9,5 5,5 – 7,5 Ammonia as N (mg/ℓ) 3 2 Nitrate/Nitrite as N (mg/ℓ) 15 1,5 Chlorine as free chlorine (mg/ℓ) 0,25 0 Suspended solids (mg/ℓ) 25 10 Electrical conductivity (mS/m) 70 mS/m above intake to

a max. of 150 mS/m 50 mS/m above intake to

a max. of 100 mS/m Ortho-phosphate as phosphorous (mg/ℓ) 10 1 (median) and

2.5 (max.) Fluoride (mg/ℓ) 1 1 Soap, oil or grease (mg/ℓ) 2,5 0 Arsenic (dissolved) (mg/ℓ) 0,02 0,01 Cadmium (dissolved) (mg/ℓ) 0,005 0,001 Chromium VI (dissolved) (mg/ℓ) 0,05 0,02 Copper (dissolved) (mg/ℓ) 0,01 0,002 Cyanide (dissolved) (mg/ℓ) 0,02 0,01 Iron (dissolved) (mg/ℓ) 0,3 0,3 Lead (dissolved) (mg/ℓ) 0,01 0,006 Manganese (dissolved) (mg/ℓ) 0,1 0,1 Mercury and its compounds (mg/ℓ) 0,005 0,001 Selenium (dissolved) (mg/ℓ) 0,02 0,02 Zinc (dissolved) (mg/ℓ) 0,1 0,04 Boron (mg/ℓ) 1 0,5

Under the General Authorisation, the proposed smelter is permitted to:

Discharge up to 2 000 m3 of wastewater on any given day into a water resource that is not a listed water resource provided the:

o Discharge complies with the General Limit Values as set out above. o The discharge does not alter the natural ambient water temperature of the

receiving water resource by more than 3ºC. o The discharge is not a Complex Industrial Wastewater. Discharge up to 2 000 m3 of wastewater on any given day into a listed water resource provided the:

o Discharge complies with the Special Limit Values as set out above. o The discharge does not alter the natural ambient water temperature of the

receiving water resource by more than 2ºC. o The discharge is not a Complex Industrial Wastewater. Discharge stormwater run-off from the premises, not containing waste or wastewater emanating from industrial activities and premises, into a water resource.

Based on the above requirements, the following should be noted:

The Coega River is not a listed water resource, and therefore General Limit


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Values are applicable. Wastewater discharged from the smelter site into a water resource must therefore satisfy the General Limit Values.

Process wastewater from the proposed smelter is not considered a Complex Industrial Wastewater.

As atmospheric emissions from the smelter and on-site activities (e.g. spillages) are likely to result in contamination of stormwater run-off from the smelter site, discharge of this stormwater does not fall under the General Authorisation. Stormwater must therefore be regarded as wastewater.

Under Chapter 3 of the National Water Act (Section 19), any person who owns, controls, occupies or uses land is deemed responsible for taking measures to prevent pollution of water resources. If these measures are not taken, the responsible authority may do whatever is necessary to prevent the pollution or remedy its effects and to recover all reasonable costs from the responsible person. Non-compliance with this provision constitutes a criminal offence. The measures referred to may include measures to:

Stop, modify or control any act or process causing the pollution;

Comply with any prescribed waste standard or management practice;

Contain or prevent the movement of pollutants;

Eliminate any source of the pollution;

Remedy the effects of the pollution; and

Remedy the effects of any disturbance to the bed and banks of a watercourse.

9.3.3 South African guidelines and standards

In addition to satisfying water quality requirements specified under the General Authorisation, the following guidelines are applicable to the smelter:

South African Water Quality Guidelines – Aquatic Ecosystems (DWAF, 1996)

Marine Water Quality Guidelines (DWAF, 1995).

South African Water Quality Guidelines – Aquatic Ecosystems

These guidelines are used by DWAF as a decision support tool for management and protection of aquatic ecosystems. The different water quality criteria and objectives provided in the guidelines are typically used in the following ways:

Target Water Quality Range (TWQR) is a management objective used to specify the desired or ideal concentration range and/or water quality requirements for a particular constituent.


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The Chronic Effect Value (CEV) is a criterion used in certain special cases where the TWQR is exceeded. The setting of water quality requirements or objectives at the CEV protects aquatic ecosystems from acute toxicity effects.

The Acute Effect Value (AEV) is a criterion used to identify those cases requiring urgent management attention because the aquatic environment is threatened, even if the situation persists only for a brief period. The AEV may also be used to identify those cases in urgent need of mitigation. However, the AEV should not be used for setting water quality requirements for aquatic ecosystems.

The guidelines applicable to the smelter to ensure protection of aquatic ecosystems are presented in Table 9.5. Table 9.5: South African Water Quality Guidelines for aquatic ecosystems

Parameter Target water quality range (TWQR) Chronic effect value

(CEV)

Acute effect value (AEV)

PH pH vales should not be allowed to vary by > 0,5 of a pH unit, or by > 5% (use more

conservative estimate)

- -

Aluminium as Al (mg/ℓ)

< 0,005 (pH < 6,5) < 0,01 (pH > 6,5)

0,01 (pH < 6,5) 0,02 (pH > 6,5)

0,1 (pH < 6,5) 0,15 (pH > 6,5)

Total Suspended solids (TSS)

(mg/ℓ)

Any increase in TSS concentrations must be limited to < 10% of the background TSS concentrations at a specific site and time

- -

Total dissolved solids (TDS)

(mg/ℓ)

TDS concentrations should not be changed by > 15% (from normal water body cycles), and amplitude/frequency of natural cycles in TDS

concentrations should not be changed

- -

Fluoride (mg/ℓ) < 0,75 1,5 2,54 Soap, oil or

grease (mg/ℓ) No guidelines

Zinc (dissolved) (mg/ℓ)

< 0,002 0,0036 0,036

Source: DWAF, 1996

Marine Water Quality Guidelines If process wastewater and contaminated stormwater are discharged from the smelter site to the sea the Marine Discharge Guidelines will be applicable. The impact of process wastewater and contaminated stormwater discharges on the marine environment are discussed in Chapter 10 dealing with Discharges to the marine environment.


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9.3.4 International guidelines and permits affecting Aluminium Pechiney’s current

international operations Aluminium Pechiney currently operates nine aluminium smelters in six countries around the world, in both developed and developing world contexts. Table 9.6 provides a summary of the international guidelines/limits and permits under which Aluminium Pechiney operates these smelters. This indicates that the South African marine water quality guideline of 5 mg/ℓ for fluoride in effluent discharge is more stringent than in these six countries. Table 9.6: Fluoride guidelines and permit allocations in countries where Aluminium Pechiney currently conducts smelter operations

Country Location

National regulations on

fluoride concentrations in

effluent:

Aluminium Pechiney’s permit requirements

Australia Tomago No limit (fluoride is not a priority

substance)

40 mg/l (Hunter River - estuarine)

Cameroon Edea - No limit (Sanaga)

Canada Becancour, Quebec

- 11 mg/l (St Laurent River - fresh)

Auzat 15 mg/l (Vicdessos river - fresh)

Dunkerque 10 mg/l dry weather

20 mg/l any time

(North Sea)

Lannemezan 15 mg/l (Baïse river - fresh)

France

Saint-Jean-de-Maurienne

General limit: 15 mg/l

New aluminium smelters: 25 mg/l

15 mg/l (Arc river - fresh)

Greece Aghios Nikolaos - No limit (Mediterranean Sea)

Netherlands Vlissingen - 50 mg/l (North Sea)

9.4 Characteristics of the receiving environment 9.4.1 Coega River

A description of the affected natural environment, in particular the lower reaches of the Coega River Valley and Butterfly Valley, is provided in Chapter 4. This includes the results of the river classification study (Gibb, 1999). This study concluded that the lower section of the Coega (between the N2 highway and the coast) is Class F, which means it is critically modified: modifications have reached

FINAL ENVIRONMENTAL IMPACT REPORT CSIR, 2002 page 9-10


a critical level and the system has been modified completely or with an almost complete loss of habitat.

9.4.2 Geology and groundwater

The 1:250 000 Geological Series map for Port Elizabeth 3324 shows that the IDZ area is underlain by young (post-Karoo) sedimentary rocks of the Uitenhage Group and Bluewater Bay Formation1. The site itself is located on Bluewater Bay alluvial deposits of gravel and sand, as well as deposits of calcareous sandstone, shelly limestone and conglomerate which make up the Alexandria Formation. These shallow surface formations are underlain by a deep deposit of the Kirkwood Formation of the Uitenhage Group. The Alexandria and Bluewater Bay Formations are likely to contain groundwater at shallow depths in a localised, unconfined aquifer located in the unconsolidated alluvial or marine gravels and sand deposits. The quantity of groundwater in this aquifer would depend on the local rainfall recharge and the depth of these layers, but is unlikely to provide a large sustainable groundwater supply. Limited geohydrological or groundwater data are available for the Aluminium Pechiney site and the depth to the water table on the site is not known. Based on monitoring studies conducted for the Coega Development Corporation at a number of boreholes north of the proposed Aluminium Pechiney site the quality of the shallow groundwater in the vicinity of the smelter site is generally poor (SRK, 2002). For example, the fluoride concentrations recorded were generally high (up to 14 mg/ℓ) and regularly failed the SABS 241-2001 Maximum Allowable Limits of 1.5 mg/ℓ for drinking-water (De Souza and Mackintosh, 2002).

The underlying Kirkwood Formation has a lower permeability and forms a clay-rich confining layer (aquitard) above the main water-bearing unit, which is the deep, regional, confined, fractured rock aquifer in the quartzites of the Table Mountain Group, known as the Coega Ridge Aquifer (refer to section 4.2.5). Simplified geological cross sections by Maclear (2001) show a depth of at least 200m of aquiclude material (i.e. Kirkwood Formation) between the surface and the deep Table Mountain Group aquifer in the area of the Aluminium Pechiney site. The Coega Ridge Aquifer is a unit of the Uitenhage Artesian Basin and is protected as a Subterranean Government Water Control Area (SGWCA), proclaimed in 1957 to protect the artesian aquifer against overexploitation. The Aluminium Pechiney site falls within this SGWCA. The Coega Ridge Aquifer Unit is, however, not hydraulically connected to the other aquifers in the area (such as the Swartkops Aquifer) and does not receive groundwater from the shallow aquifer at the Aluminium Pechiney site.


1 Name not yet approved by the South African Committee on Stratigraphy


9.5 Scenarios considered in the impact assessment

A number of scenarios have been have been considered in order to determine the possible range of fluoride concentrations in the stormwater discharge during operations, and hence to assess the potential impact on the receiving environment. These scenarios include:

Scenario 1: The effect of atmospheric deposition with varying rainfall

intensity on the potential fluoride concentration in the stormwater discharge from the interceptor pond (12 600 m3);

Scenario 2: The effect of enlarging the interceptor pond to 30 000 m3;

Scenario 3: The effect of poor on-site management of spillages on the fluoride concentration in the stormwater.

Scenario 4: The effect of disposing of process wastewater via the stormwater system for process wastewater of varying fluoride concentrations.

Scenario 5: The risk of interceptor pond overflow

Scenario 6: The potential for removing process wastewater by road tanker.

The results from determining fluoride concentrations in stormwater for this range of scenarios are shown in Table 9.7. The following additional scenario is also discussed in the Final EIR, based on feedback from the authorities: Direct the process wastewater (822 m3/day with fluoride concentration of 2-6 mg/ℓ ) to the Fish Water Flats Sewage Treatment Works.

9.6 Design alternatives considered in the impact assessment

The design for the smelter includes a conceptual stormwater management plan, which is currently being finalised by Aluminium Pechiney and linked with the stormwater management for the IDZ being planned by the CDC. The following principles guide the design and operation of the smelter stormwater system and are illustrated in Figure 9.2.

Principle 1: Sediment Capture

Initial control of the quality of the water collected from the site requires the collection of gross sediments, oils and floating debris. A sedimentation basin designed to separate gross particulates is located at the site network collection point immediately prior to the site retention pond. Traps will also be installed in this basin to remove oils and other floating contaminants.



Principle 2 – “First Flush” Collection

The interceptor pond is designed to provide control of the “first flush”2 of stormwater from any rain event – shown as route (a) in Figure 9.2. This first flush principle aims to collect up to the first 20 mm of rainfall from the 50 hectares of paved, roofed and sealed areas of the smelter site. Considering the extent of the proposed smelter site the interceptor pond should be designed with the proposed volume of 12 600 m3. Following the cessation of a rain event, water stored in the first flush interceptor pond can be discharged as a “controlled” flow via the normal offsite network (possibly via the second flowrate controlling Attenuation Dam). After the pond has been drained, it is maintained in a near empty state in readiness for the next rain event. (The pond should not be drained completely dry, in order to provide a layer of water to protect the lining).

Principle 3 – Discharge Flowrate Attenuation

Once the first flush Interceptor Pond is full, all further stormwater flow during a rain event bypasses the Interceptor Pond by way of a series of weirs - shown as route (b) in Figure 9.2. The discharge rate of this bypass flow from the smelter site to the IDZ network is controlled by an additional Attenuation Dam, designed to meet the flowrate limits set by permits or by agreements between relevant parties (equal to a one in two year peak rain event). The required capacity of the Attenuation Dam has been estimated to be 30 000 m3. Rainfall associated with the one in two year event is used to calculate the allowable rate of discharge from the site, which is presently understood to be 23 m3/s. Discharge from the site will be via the stormwater system provided by CDC for the IDZ, which is planned to route the stormwater from the AP site through the northern corner of Butterfly Valley and to the harbour via a culvert or a pipeline.

Principle 4 – Process Wastewater Discharge

Three options exists for process wastewater discharge:

Process wastewater from re-circulating process cooling water circuits is discharged into the site stormwater system

Process wastewater is used for irrigation on site

Process wastewater is sent to the Fish Water Flats Sewage Treatment Works.

The option of removing process wastewater from the site by means of road tanker was discarded based on the assessment that this would require approximately 27 tanker trucks per day to remove the volume generated.

2 The first flush of stormwater contains the highest concentration of dissolved fluorides rapidly leached from dusts accumulated on rooftops, roads and other sealed areas between each rain event. The first flush collection also acts as an important interception control for accidental spillages on site of materials such as oils or chemicals and for water from fire fighting.



Overflow weir

Final d

Process wastewater Stormwater

Dirt trap

Figure 9.2: Proposed storm

Overview of stormwater man

The transport of stormwaand NPA’s property will stormwater will be transp2.1). Thereafter, it will be Valley to the point where the saltworks. This sectionor an open culvert lined controls (eg. attenuation pmust have the capacity tosmelter site will generate for stormwater from the Consulting Engineers, per

FI

(a)
Interceptor pond12 600 m3
(b)

ischarge

Attenuation dam 30 000 m3

water management system for the smelter site

agement from the smelter site to the coast

ter from the smelter site to the boundary between CDC be the CDC’s responsibility. From the smelter site, orted in a pipeline to south of the N2 highway (Figure transported down a small valley to the north of Butterfly it reaches the planned railway line and conveyer belts at down the small valley would either consist of a pipeline

with rip-rap protection and incorporating other erosions onds). The stormwater system running down this valley

transport stormwater at a rate of 20 m3/s. Given that the an estimated 11 m3/s, the remaining capacity is required N2 highway and other areas (Loyiso Dotwana, Iliso

sonal communication, 5/8/2002). From the bottom of the

NAL ENVIRONMENTAL IMPACT REPORT CSIR, 2002 page 9-14


valley to the sea, the continued stormwater management system would be NPA’s responsibility to design, construct and operate. It is envisaged that the stormwater would be directed along the western edge of the saltworks to the port, from where it would either be discharged into the harbour basin or into the surfzone to the north-east of the breakwater. (Figure 2.1 in Chapter 2 shows the proposed routing of stormwater).

9.7 Impact assessment and mitigation

9.7.1 Water use during construction

During construction water will be used for both construction and domestic purposes. Water required for the preliminary earthworks has been estimated at 0,2 Mℓ/day, whereas water used during construction has been estimated at 230 000 m3/year (or 0,6 Mℓ/day). This water will be supplied by the NMMM, the quality of which will be as per minimum standards of the Metro (i.e. drinking-water quality). Water used for construction will be obtained from the Nooitgedagt Water Treatment Works which draws water from the Gariep Dam on the Orange River. The Nooitgedagt Water Treatment Works is located at Sunland some 40 km north of the IDZ and currently has spare capacity of approximately 28 Mℓ/day (Raymer, D. 2002. Personal Communication, 3 July 2002. Nelson Mandela Metropolitan Municipality). Water consumption during the preliminary earthworks for the smelter is approximately 1,4% of the spare capacity of the Nooitgedagt Water Treatment Works, while water consumption during the construction phase is approximately 2,2% of the spare capacity. The negative impact of water use on the available capacity is, therefore, likely to be of low significance.

9.7.2 Water use during operation Domestic Water Use

Domestic water supply (for consumption, toilets, kitchens, cleaning, etc) is to be supplied from the NMMM. Typical consumption by the smelter has been estimated to be 80 000 m3/year (or 0,2 Mℓ/day). Water quality will meet the minimum standards of the Metro (i.e. drinking-water quality). The volume of domestic water consumption by the proposed smelter is approximately 0,8% of the spare capacity of the Nooitgedagt Water Treatment Works.



Process Water Use

Industrial water consumption has been estimated at approximately 500 000 m3/year (or 1,4 Mℓ/day). Initially this requirement will be met by the Nooitgedagt Water Treatment Works. The CDC proposes that, in the future, the bulk of the process water required would be recycled water supplied from the Fishwater Flats Reclamation Works near the Swartkops River mouth. The facilities for reclaiming treated wastewater do not presently exist, but are planned (depending on future demand). It is envisaged that water re-use facilities with a capacity of 60 Mℓ/day will be constructed. Process water consumption by the proposed smelter is approximately 2.3% of the total capacity of the proposed Fishwater Flat Reclamation Works. However, as it is unlikely that the Fishwater Flat Reclamation Works will be available at the start of smelter operation, the process water will have to be obtained from the Nooitgedagt Water Treatment Works. Process water consumption by the proposed smelter is approximately 5% of the spare supply capacity of the Nooitgedagt Water Treatment Works. Increased demand as a result of the proposed smelter on the regional water budget is considered to be negligible. Therefore, the significance of the negative impact of the use of during the operation of the smelter is considered to be low.

Mitigation and management measures While the impact of water use as a result of the proposed smelter is considered to be of low significance, additional management measures should be employed to reduce the impact significance even further. The following additional water conservation techniques are recommended:

Domestic - Implement water saving devices (Dual flush toilets, automatic shut-off taps, etc).

Irrigation - As far as possible, potable water should not be used for irrigation purposes. However, untreated process wastewater or stormwater is unlikely to be suitable for irrigation purposes because of its high fluoride and TDS levels. Ideally, landscapes should be designed to absorb rainwater run-off (stormwater) rather than having to carry it off-site in stormwater drains.

Horticulture – Indigenous vegetation should be used to minimize watering.

Cleaning - Cleaning methods utilised for cleaning vehicles, floors, etc should aim to minimise water use.

Fire fighting - Proper pressure management within fire water systems will limit water use.


Elimination of leakage - Regular audits of water systems should be conducted to identify possible water leakages.


Metering and measurement - Proper metering and measurement of water use and wastewater discharges will enable proper performance review and management.

9.7.3 Wastewater generated during construction

During construction, wastewater generated will include:

Domestic wastewater

Construction process wastewater

Stormwater run-off

Domestic wastewater

With respect to domestic wastewater (i.e. sewage) produced during construction, the CDC has stated that it will utilise the existing municipal sewer network and the Fishwater Flats Reclamation Works for treatment of domestic wastewater produced by the IDZ. The Metro has noted that the Fishwater Flats Reclamation Works has sufficient spare capacity to meet the effluent from the smelter (Raymer, D. 2002. Personal Communication, 3 July 2002. Nelson Mandela Metropolitan Municipality). If sanitary facilities cannot be connected to the Coega IDZ sewage collection network, a local waste contractor will need to be appointed (e.g. provision of portable toilets). If properly managed, no impacts of environmental significance are expected.

Construction process wastewater and stormwater

With respect to construction process wastewater and stormwater, contamination could result from contact with, for example, chemicals, oils, fuels, sewage, solid waste, litter. However, during construction, erosion from construction areas resulting in increased turbidity and downstream sedimentation is likely to be the main water quality concern. Management measures are proposed to ensure that the negative impacts associated with construction wastewater are of low significance.

Mitigation and management measures Although the environmental impact has been rated as low, the exact management practices that will be followed during construction phase have yet to be established/identified. For this reason a number of practical mitigation/ environmental management measures that should be implemented are highlighted. In order to minimise potential environmental impacts, the following measures should be implemented:


Erosion and sedimentation because of construction activities must be


limited. In particular:

o The boundaries of the site must be demarcated clearly in order to restrict construction activities to the site.

o Permanent or temporary fences must be erected and maintained to ensure that activities are conducted within a limited area, and thus limit impact on the environment.

o “No-go” areas (e.g. environmentally sensitive areas) should be clearly marked. No persons, machinery, equipment or materials should enter these areas.

o Suppliers/contractors should ensure that all vehicles utilize dedicated routes for construction vehicles.

All material storage areas should be designated to reduce risk of spillages. All materials should be covered during transport to prevent them from spilling. If there is a risk of contamination of stormwater, all stockpiles should be covered/kept out of the rain.

Information posters describing environmental specifications, and aimed at all levels of construction personnel should be erected and maintained.

Transport, use, and disposal of hazardous material must comply with legislation (e.g. dispose at a permitted hazardous waste site). Of importance is the training and education of personnel in handling these hazardous materials. This includes road safety when transporting these materials.

Contaminated stormwater and other run-off from the construction site must be contained. Construction of the dirt trap, interceptor pond and the attenuation dam must commence as early as possible in the construction phase.

Workshops, washing areas, etc must contain bunded areas.

Tanks containing fuels should be fully enclosed. Fuel tanks must be contained in bunded areas and any wastewater or spilled fuel collected within the bund must be disposed of as a hazardous waste. Oils collected in grease traps must be collected by the appointed waste disposal contractor.

Emergency procedures should be developed and communicated to all construction personnel such that they are aware of the procedures to be followed for dealing with spills and leaks. The procedures should include identification of responsible personnel, contact details of emergency services, etc. The necessary materials and equipment for dealing with spills and leaks must be available at all times.

9.7.4 Wastewater generated during operation

Wastewater generated as a result of the proposed project will include:

Domestic wastewater;

Process wastewater; and

Stormwater run-off.



Domestic wastewater

The CDC plans to utilise the existing municipal sewer network and the Fishwater Flats Reclamation Works for treatment of domestic wastewater produced by activities in the IDZ. The Metro has indicated that the Fishwater Flats Reclamation Works has sufficient spare capacity to meet the effluent from the smelter (Raymer, D. NMMM, 2002). No impacts of environmental significance are expected.

Process wastewater The amount of process wastewater generated has been estimated to be 300 000 m3/year (i.e. 822 m3/day, which is within the DWAF maximum allowable discharge of 2 000 m3/day). As discussed earlier, three options exist for process wastewater, namely discharge to stormwater system, use for irrigation on site, or redirect to the Fish Water Flats Sewage Treatment Works. Discharge to the stormwater system has been assessed to have a manageable impact on the receiving environment. Use for irrigation raises concerns about the potential medium to long-term effects that fluoride in the process water could have on the soil and water chemistry of the site (refer to section 9.7.5). Before this option is adopted, process wastewater quality needs to be confirmed, a baseline groundwater monitoring study undertaken, and a more detailed study needed to ascertain the significance of these potential impacts. Redirecting the process wastewater to a sewage treatment works has the potential benefit that this water could in future be reclaimed when the necessary re-use facilities are established (as described in section 9.7.2). It is therefore proposed, based on currently available options, to discharge the process wastewater into the smelter site’s stormwater system. The quality of this wastewater will be controlled within acceptable discharge parameters (pH, suspended solids, metals) by way of specification of the commercial water treatment programs employed for corrosion and biological control in the circuits. The wastewater would initially be discharged into the stormwater system (most likely the attenuation dam) on a semi-continuous basis, likely resulting in small dry weather base flows from the smelter site. However, potential may also exist for this water source to be treated and re-used in the smelter process. Some further assessment of this option will be undertaken as part of the water licence application process.



Stormwater

A review of stormwater analyses from several Pechiney smelter sites world-wide showed that constituents of primary concern include zinc, aluminium and fluoride. Of these, fluoride is of the greatest concern since the average recorded fluoride concentration for stormwater is 21.3 mg/ℓ. This grossly exceeds both the DWAF General Limit Value of 1.0 mg/ℓ and the South African Water Quality Guidelines (DWAF, 1996) Aquatic Ecosystem Target Water Quality Range (TWQR) of 0,75 mg/ℓ. The specialist study on water use and liquid waste therefore undertook a detailed analysis of the predicted fluoride concentrations in wastewater for six scenarios (De Souza and Mackintosh, 2002). The results of this analysis are summarised in Table 9.7. It is important to note that these are total cumulative concentrations and based on worst case scenarios where heavy rainfall is experienced after a dry period. The following key assumptions were applied in calculating the predicted concentration of fluoride in stormwater:

• the average atmospheric deposition rate for fluoride at the smelter site is estimated to be 150mg/m2/month

• the mean maximum rainfall intensity for a one-hour period is 20 mm for the period 1972 to 2001 Note 1

• the maximum rainfall intensity for a one-hour period for the period 1972 to 2001 is 56.5 mm Note 1

• 80% mobilisation of surface fluoride occurs in the first 20 mm of rainfall.

Note 1: Based on data for Port Elizabeth. No long-term data is available for Coega.



Table 9.7: Estimated fluoride concentrations in stormwater for six operating scenarios

Source of fluoride Estimated total

concentration in discharge (mg/ℓ )

Scenario

15.3 Scenario 1: 20mm rainfall in 1 hour after 3 month dry spell

9.7 Scenario 2: 56.5mm rainfall in 1 hour after 3 month dry spell

1. Deposition (“fallout”) from the smelter fluoride emissions into the atmosphere

5.4 Scenario 3: 56.5mm rainfall in 1 hour after 3 month dry spell

Interceptor pond enlarged to 30 000m3 2. Atmospheric

deposition plus accidental or other spillages of fluorinated materials (eg. cryolite)

30 Scenario 4: 50kg of cryolite is spilt per month, in addition to the

fluoride from the atmospheric deposition as described in Scenario 1

13.8

Scenario 5: Process water with 2mg/ℓ fluoride is added to the

stormwater discharge for Scenario 1

3. Atmospheric deposition plus discharge of process wastewater into the stormwater system 14.2 Scenario 6:

Process water with 6mg/ℓ fluoride is added to the stormwater discharge for Scenario 1

These scenarios show that the potential fluoride concentration in combined stormwater and process wastewater could range from in the order of 5 to 30 mg/ℓ. Aluminium Pechiney has indicated that, based on their experience from similar smelter operations around the world, the fluoride concentration in the combined stormwater and process water is expected to be below 20 mg/ℓ on average. With good management, Aluminium Pechiney expects the fluoride concentrations in process wastewater to be close to 2mg/ℓ (Scenario 5). The following points highlight the results of assessing the various scenarios for stormwater management:

It is highly unlikely that the fluoride concentration in either the process wastewater or stormwater will satisfy the DWAF General Limit Value (1 mg/ℓ) or DWAF Aquatic Ecosystem Guidelines (0,75 mg/ℓ).

Increasing the capacity of the interceptor pond will not result in the discharged water meeting the required fluoride concentration standards/guidelines.

Based on an assessment of local rainfall data, the risk of interceptor pond/attenuation dam overflow as a result of site run-off is minimal.



Removal of process wastewater or stormwater from site using a road tanker is not feasible.

Poor on-site management of spillages can increase fluoride loading in the stormwater substantially.

Combining the process wastewater (2 – 6 mg/ℓ fluoride; 822 m3/day) with stormwater has a minimal dilution effect, and still does not achieve the required standards/guidelines for the fluoride concentration.

Based on the above findings, discharge or spillage of process wastewater and stormwater into the surface water environment will exceed South African guidelines. These guidelines will be exceeded even with the implementation of numerous Best Available Technology (BAT) and Best Practicable Environmental Option (BPEO) designs and controls employed in the smelter design and operation, as described in section 9.7.6.

The consequence of releasing stormwater directly into the natural environment (e.g. the side valley north of Butterfly Valley) is considered to be negative with a high significance. This is due to the DWAF freshwater guideline of 1 mg/ℓ for fluoride being exceeded. Findings from the specialist study on effluent discharges to the marine environment (Luger et al, 2002) show that discharge of process wastewater and stormwater into the marine environment is not problematic as dilution of contaminants (including fluoride) to acceptable levels is achieved readily (refer to Chapter 10). Therefore, the ultimate discharge of process wastewater and stormwater to the marine environment is the only viable option that should be considered. In Chapter 10 it is predicted that the impact of discharging combined process wastewater and stormwater to the marine environment is of low significance (with mitigation).

Mitigation measures for process wastewater and stormwater discharges In addition to the stormwater management measures described above, it is recommended that:

The marine discharge of fluoride-enriched process wastewater and stormwater is considered to be the environmentally preferable option.

Since the fluoride concentration in the process wastewater is expected to be considerably less than that of the stormwater (e.g. 6 mg/ℓ vs. 15 mg/ℓ), the drainage system must be designed such that process wastewater can be discharged separately from the stormwater in the event that options become available in future for recycling or re-use of process wastewater.

Stormwater quality can be improved by effective management of on-site spills. It is recommended therefore, that plant-wide spillage audits be conducted and follow-up management measures implemented.



Implementation of these measures should reduce the significance of the predicted impact of process wastewater and stormwater discharge from high to low. Although this impact is of low significance (with mitigation, as described above), it is recognised that some further alternative options could be developed for managing process wastewater discharge. In line with the fundamentals of Continuous Improvement, it is recommended that further options for process wastewater be investigated in the development of the Environmental Management Plan for the smelter.

9.7.5 Potential impacts on groundwater

Groundwater in the shallow sand and gravel aquifer in the Bluewater Bay and Alexandria Formation may be susceptible to contamination through infiltration of fluoride polluted rainwater. The geology of the area suggest that these formations would be likely to transport contaminated groundwater towards the Coega River, the Butterfly Valley area and the coastal environment (SRK, 1998, Colvin et al 1996, Meyer 1998, Maclear, 2001). No groundwater is known to be abstracted down gradient of the site and, due to the low permeability of the soils, it is not expected to deliver significant quantities of water to receiving environments, if any. Impacts on shallow groundwater A natural mitigating factor for attenuating fluoride concentrations in shallow groundwater is the presence of the calcareous soils of the Alexandria Formation, which have the capacity to immobilise/fix fluoride in the form of calcium fluoride minerals. Fluoride deposition will, when dissolved in rainwater, form an acid solution (expected because of the release of hydrogen ions from HF deposition). This will help to dissolve calcium from the soils and enhance ligand exchange of fluoride for hydroxide on minerals. Fluoride and hydroxide ions are of similar size and chemical behaviour. In acid solutions (low pH) the concentration of hydroxide ions (OH-) in the water is low. If there are fluoride ions in solution, some of these can exchange for the hydroxide ions that are attached as ligands at chemically reactive sites on mineral surfaces to “balance the deficit”. (The fluoride will become attached to the solid and the hydroxide ions will be released into the solution. This process decreases the concentrations of dissolved fluoride and increases the pH of the solution). The amount of exchange that takes place depends on the mineral type, its surface properties and the composition of the solution in contact with the mineral. Both precipitation of calcium fluoride minerals and ligand exchange will immobilise the fluoride to a certain extent. Many calcium fluoride minerals have a low solubility



and therefore fluoride concentrations in solution are reduced. Solubility is further limited by chemisorption of calcium fluoride minerals onto clays and oxides of low crystallinity (McBride, 1994), a process very similar to ligand exchange, in which both calcium and fluoride become attached to the solid surfaces. The concentrations of fluoride in groundwater of the upper aquifer would therefore be expected to be lower than that of the surface runoff water although the groundwater may still be vulnerable to some degree of fluoride contamination. This would need to be established by monitoring. Impacts on the Coega Ridge Aquifer The deeper Coega Ridge Aquifer is protected by the confining Kirkwood clays (mudstones) and is highly unlikely to be contaminated by surface deposition or other activities at the site. The confined aquifer is only vulnerable to contamination in its recharge areas (of which the outcrop at Coega Kop might be one) but direct recharge to this aquifer from the surface will not occur through the Kirkwood Formation at the proposed smelter site. The main recharge areas for this deep aquifer are located in the large surface outcrops of quartzite belonging to the Peninsula Formation of the Table Mountain Group, about 20 km west of the proposed Aluminium Pechiney site. (Coega Kop is a relatively small “window” of exposed Peninsula Formation quartzites, and although some local recharge may occur here, it will be limited in comparison to that occurring over the vast outcrop of the Groot Winterhoek mountains north of the Coega Fault) Activities at the Aluminium Pechiney site should therefore not impact on the deep confined aquifer. Preferred groundwater recharge pathways, such as poorly constructed boreholes drilled into the Table Mountain Group quartzites, may put the lower aquifer at risk if contaminated surface water infiltrates via these conduits. Care should therefore be taken in conducting further groundwater investigations that such preferred pathways are avoided. The potential negative impact is rated as medium significance given the uncertainty surrounding current knowledge of groundwater. Mitigation measures Further investigations should be undertaken to establish the groundwater presence and characteristics of the smelter site.



The geohydrological study should:

Establish water table depth, seasonal variations and local flow patterns in the shallow aquifer. Confirm whether or not flow occurs towards the Coega River.

Establish the thickness of the aquitard/aquiclude layer above the main TMG aquifer.

Establish the relationship between the shallow aquifer and surface water systems or terrestrial ecosystems in the area. If possible, quantify any discharge/baseflow to the Coega River.

Establish current and potential future uses of groundwater in the area.

Establish baseline quality of groundwater in the shallow aquifer – include full analysis of major and trace elements up- and down-gradient of the site. These should be measured at least twice (wet and dry season) to provide a record of pre-development values.

9.7.6 Identification of the best practicable environmental option (BPEO)

Principle applications of BAT and BPEO aimed at reducing the concentration of fluoride in stormwater include the following:

Dry scrubbing air emission controls for primary collection and treatment of gaseous and particulate fluorides from the electrolysis cells (pots) operating at an efficiency of >99%.

Fully hooded pots with a collection efficiency of >98.5%.

BAT materials handling systems, featuring enclosed conveyors, fully sealed pneumatic transport, dust filters at all transfer points, crushing systems under negative pressure, covered production workshops and internal transfer routes.

Enhanced integrated plant layout minimising transport distances of raw materials and intermediate products.

Extensive spillage control and housekeeping procedures, featuring bunded areas, regular sweeping of roadways and work areas, reporting systems, rigorous training and awareness programs.

Lined interceptor pond on-site to capture the “first flush” of rainfall events and trap sediments, oils and litter.

A lined attenuation dam to allow controlled release of stormwater.

Constant monitoring of water quality.

Furthermore, by designing the plant layout to minimise transport distances for raw materials and intermediate products, as well as applying extensive spillage control and house-keeping measures during operation, Aluminium Pechiney aim to



minimise the average fluoride concentration in stormwater resulting from on-site spillages.

The transport of process wastewater and stormwater from the western edge of the saltworks to the port has yet to be finalized. A lined canal or enclosed pipeline is likely to have the lowest environmental impact. However, considering the present degraded state of the lower reach of the Coega River and the possible expansion of the port in the future, the capital expenditure required to construct a lined canal or pipeline may not be justified. This requires further investigation by the National Port Authority, as part of the design of this section of the stormwater management system.

9.8 Monitoring recommendations

The quality and quantity of process wastewater and stormwater should be monitored/recorded to verify the scenario predictions.

Plant-wide spillage audits should be conducted to monitor spillages and allow for the identification of areas requiring improved management.

Should the need for a more regular groundwater monitoring programme be required, recommendations for monitoring boreholes would include:

Shallow monitoring boreholes should be mainly located along the down-gradient boundary of the site with a reference borehole along the other boundaries to monitor quality of the groundwater entering the site.

If there is a chance for vertical stratification of flow e.g. in layered sediments of differing hydraulic conductivity, multilevel piezometers, or groups of monitoring wellpoints of different depths, should be installed to ensure that any pollution plumes can be properly characterised.

The deepest monitoring boreholes on site should extend to the depth of the top of the clay/mudstone aquitard (Kirkwood Formation).

It is not advisable to construct deep monitoring boreholes into the Table Mountain Group aquifer at the site as these could serve as a conduit for contaminated water into the deep potable water aquifer. Instead Table Mountain Group groundwater should be monitored at points of use around the site. These will need to be identified by a hydrocensus, e.g. selected boreholes on farms to the north of the site could be included in a monitoring programme with the owners consent.

9.9 Water licence requirements

The water licences required with respect to the management of wastewater from the smelter site are summarised below in Table 9.8:



Table 9.8: Identification of water licence requirements for the stormwater management system

Activity Responsible party

Licence/permit

Construction, operation and maintenance of the on-site stormwater interceptor pond and attenuation dam

AP A licence is required from DWAF under the National Water Act (1998).

Construction, operation and maintenance of stormwater pipeline from the attenuation dam to the culvert underneath the N2.

CDC No EIA or licence required.

Construction, operation and maintenance of a stormwater culvert from the N2 through a side valley (north of Butterfly Valley) to the Coega estuary.

CDC A licence is required from DWAF under the National Water Act (1998).

Construction, operation and maintenance of a stormwater canal along the western edge of the saltworks to the sea (for discharge to the port or surfzone).

NPA A licence is required from DWAF under the National Water Act (1998).

Reserve Determination study for the Coega River: a reserve determination study must be undertaken by DWAF, completion of which may be a prerequisite for licences being approved.

DWAF CDC initiated the reserve determination process with DWAF in August 2002.

9.10 Summary of impacts and mitigation

The impact assessment for issues related to water use and liquid waste generation and management are summarised in Table 9.9.

Water Use

Increased water use for both domestic and industrial purposes will have a low negative impact. This was because of the already existing or planned facilities for water supply.

Domestic wastewater discharge

Domestic wastewater discharge will have a low negative impact. This is because domestic wastewater would be discharged to the existing sewer facilities.



Construction wastewater discharge

Although the expected environmental impact is rated as low, it must be noted that the assessment was made based on expected general management practises to be followed on-site during the construction period. A number of practical on-site management measures have been recommended, which, if followed, will minimise environmental impacts related to construction activities.

Wastewater/stormwater discharge on the surface water environment

Wastewater/stormwater discharge will have a high negative impact on the surface water environment. This results from the high likelihood that process wastewater and stormwater fluoride concentration will exceed the required DWAF General Limit Values and DWAF Water Quality Guidelines for Aquatic Ecosystems. It is recommended that discharge of fluoride-enriched process wastewater and stormwater to the marine environment be the only option considered. Findings of the marine discharges specialist study predict that the impact of discharging process wastewater and stormwater into the marine environment is of low significance (with mitigation). Considering marine discharge, the transport of process wastewater and stormwater from the western boundary of the saltworks to the port has yet to be finalized. A lined canal or enclosed pipeline is likely to have the lowest environmental impact.

Satisfaction of impact mitigation measures will reduce the environmental impact from high negative impact to low negative impact. In particular, the on-site management of fluoride spills is very important.

Wastewater impacts on groundwater The impact of wastewater on the groundwater is potentially of medium significance. This is a precautionary assessment. Monitoring is required to ascertain the groundwater characteristics of the site.



Table 9.9: Summary impact assessment of water use and liquid waste of the proposed aluminium smelter

Impact Status Extent Duration Intensity Probability of occurrence Confidence

Significance (without

mitigation) Significance

(with mitigation) Increased water use during construction Negative Local Short term Low Definite High Low Low

Increased water used during operation Negative Local Long term Low Definite High Low Low

Construction wastewater and stormwater discharge during construction phase

Negative Local Short term Medium Probable Medium Low Low

Process wastewater and stormwater discharge on environmentally sensitive ecosystems

Negative Local Permanent High Definite High High N/A

Process wastewater and stormwater discharge along western edge of the saltworks to the port via an earth/natural channel

Negative Local Long term Low Probable Medium Medium Low

Process wastewater and stormwater discharge along western edge of saltworks to the port via a lined canal or pipeline

Negative Local Long term Low Definite Medium Low Low

Influence of wastewater practices on groundwater Negative Local Long term Medium Probable Medium Medium Low

DRAFT ENVIRONMENTAL IMPACT REPORT CSIR, 2002 page 9-29

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