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D6500 kV TRANSMISSION LINES FrOP GREA TXEr BA.N-GKO^iK ARE)h

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FINAL DRAFTENVIRONMENTAL. RL POR E

Michtelle. Clark

16 Ociober 1996

EGAT - INVESTMENT PROGRAM SUPPORT PROJECT

(WORLD BANK PARTIAL CREDIT GUARANTEE)

Contract Number 4719-30-5803-EGAT-BKK-EH!V-CS

Consultancy Engineering Services

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500 kV TRANSMISSION LINES FOR GREATER BANGKOK AREA

FINAL DRAFTENVIRONMENTAL REPORT

Michelle Clark

16 October 1996

Contract Number 4719-30-5803-EGAT-BKK-EHV-CS

Consultancy Engineering Services

5/5

CONTENTS

Chapter 1 Introduction 1

Chapter 2 Design Options 5

Chapter 3 Landscape and Visual Impact 12

Chapter 4 Socio-economic Aspects 17

Chapter 5 Cultural Heritage 22

Chapter 6 Land Use 25

Q Chapter 7 Water Quality 33

Chapter 8 Flora and Fauna 40

Chapter 9 Electric and Magnetic Fields 47

Chapter 10 Audible Noise 53

Chapter 11 Electromagnetic Compatibility 56

Chapter 12 Conclusions 59

APPENDICES

Appendix A References 63

Appendix B List of Abbreviations 64

Appendix C Glossary of Terms 65

SCHEDULE OF TABLES

Table 4.1 Key Informants for Socio-economic Field SurveyTable 4.2 Community Baseline DataTable 6.1 Land Use Categories along the Proposed 500 kV Transmission LinesTable 7.1 Waterways Potentially Affected by the 500 kV Transmission Line DevelopmentTable 7.2 Results of TEAM Surface Water Quality Survey (9 February 1996)Table 7.3 MOSTE Surface Water Quality ClassificationTable 7.4 MOSTE Surface Water Quality ClassificationTable 8.1 Species and Abundances of PhytoplanktonTable 8.2 Species and Abundances of ZooplanktonTable 8.3 Planktonic Organisms as Indicators of Water QualityTable 8.4 Species and Abundances of Benthic OrganismsTable 8.5 Benthic Organisms as Indicators of Water QualityTable 9.1 Predicted Electric Field StrengthsTable 9.2 Predicted Magnetic Field Strengths

9SCHEDULE OF FIGURES

Figure 1.1 Existing 230 kV Lines (to be Replaced) in the Greater Bangkok AreaFigure 1.2 Proposed 500 kV Lines in the Greater Bangkok AreaFigure 2.1 Vertical 2x2x2 Portal TowerFig, ,re00 °.° Hrzna 3 o r -:e

Figure 2.3 Traditional Vertical Tower with Single Steel Pole ConstructionFigure 2.4 Traditional Vertical Tower of Steel Lattice ConstructionFigure 2.5 Comparison of Final Proposed design with EGATs Existing 500 kV DesignFigure 3.1 Comparison of Proposed 500 kV Tower and Existng 230 kV TowerFigure 5.1 Location of Known Archaeological Sites in the Greater Bangkok AreaFigure 6.1 Definition of Landscape ElementsFigure 6.2 Landscape along Bangkok Noi - Sai Noi RouteFigure 6.3 Landscape along Sai Noi - Rangsit RouteFigure 6.4 Landscape along Rangsit - Chaeng Watthana RouteFigure 6.5 Landscape along Nong Chok - On Nuch RouteFigure 9.1 Assumed Phasing for Proposed Quad Circuit 500 kV Line Design

SCHEDULE OF PHOTOMONTAGES

View 3.1

SCHEDULE OF PHOTOGRAPHS

Photo 3.1 Existing 230 kV Transmission Line Crossing Typical Rural LandPhoto 3.2 Existing 230 kV Transmission Line Crossing a Real-Estate ProjectPhoto 3.3 Muang Thong Thanee Complex

CHAPTER 1

INTRODUCTION

BACKGROUND

1.1 The economic growth rate for Thailand during the 61h and 71 National Economic andSocial Development Board's (NESDB) Plan Periods (1987- 1991 and 1992 - 1996) hasbeen very high. It is expected that this high economic growth rate will continue, at leastduring the 81 plan (1997 - 2001).

1.2 One of the effects of this economic growth has been a dramatic increase in electricitydemand, especially in the Greater Bangkok Area. This increase in electricity demandhas resulted in a requirement for the Electricity Generating Authority of Thailand (EGAT)'to develop a 500 kV transmission system for this area.

K') 1.3 EGAT contracted the National Grid Company plc (NGC) to design these 500 kVtransmission lines, in conjunction with two local partners: TRANSEC and TEAM.TRANSEC are a transmission system engineering consultancy, while TEAM are anenvironmental consultancy. TEAM therefore provided much of the information for theenvironmental study.

PROJECT DESCRIPTION

1.4 The Project involves replacing four existing sections of 230 kV transmission line with 500kV transmission lines. The four sections (shown in Figures 1.1 and 1.2) and their lengthsare listed below:

a Bangkok Noi - Sai Noi 29.4 km* Sai Noi - Rangsit 24.7 km* Rangsit - Chaeng Watthana 7.4 km* Nong Chok - On Nuch 17.9 km

All the above is to consist of double circuit transmission lines, apart from 1.8 km of theNong Chok-On Nuch section which will be quad circuit. This will form the line entry toOn Nuch Substation.

1.5 EGAT require the new 500 kV transmission line system to be constructed as far aspossible along the existing 230 kV transmission lines' alignments using the same Rights-of-Way. The total width of a 230 kV Right-of-Way is 40 metres, ie a corridor of 20 metreseither side of the route centre-line.

SCOPE OF ENVIRONMENTAL REPORT

1.6 The objectives of the study are firstly to identify the potential environmental impacts dueto the Project and, secondly, to recommend mitigation measures to alleviate any adverseimpacts. The environmental areas of concern which have been addressed in this reportare as follows:

1

* landscape and visual impact* cultural heritage* land use* water quality__ _ * flora and fauna (particularly aquatic ecology and impacts on birds):s- ~ * effects on human beings (including safety, socio-economic impacts, electric a,.d

-magnetic field effects and audible noise)* electromagnetic compatibility

1.7 Effects on climate and air quality were considered, and rated as insignificant.

2

230 kV double circuitSai Noi twin 1272 MCM Rangsit

230 kV double circuitft 1l single 127;2 MCMChaeng Watthana

230 kV double circuitsingle 1272 MCM Nong Chok

230 kV double circuittwin 1272 MCM

Oni NuchBangkok Noi

Chao Phraya

Figure 1.1 Existing 230 kV Lines (to be Replaced) In the Greater Bangkok Area

500 kV double circuitSal Nol quad 1272 MCM Rangsit

500 kV double circuitquad 1272 MCM

Chaeng Watthana

500 kV double circuit Nong Chokquad 1272 MCM

500 kV double circuitquad 1272 MCM

500 kV quad circuitquad 1272 MOM

On NuchBangkok Nol

Chao Phraya

Figure 1.2 Proposed 500 kV Lines in the Greater Bangkok Area

CHAPTER 2

DESIGN OPTIONS

INTRODUCTION

2.1 The parameters driving the design of the new 500 kV transmission lines were as follows:

* the restricted Right-of-Way, resulting in a need for a compact line design, both frommechanical {eg conductor blow-out) and electrical (eg EMF) perspectives,

* environmental concerns (mainly visual impact),* ease of construction, operation and maintenance,* cost of construction, operation and maintenance.

2.2 Four preliminary tower designs were considered initially:

. > * vertical 2x2x2 portal tower of steel lattice construction,* horizontal 3x3 portal tower of steel lattice construction,* traditional vertical tower of single steel pole construction,* traditional vertical tower of steel lattice construction.

These are shown in Figures 2.1 to 2.4.

ASSESSM ENT

2.3 The vertical 2x2x2 portal tower has the advantages of low EMF levels due to reducedphase separation, longer spans (ie fewer towers and reduced visual impact ) and reducedfoundation loads (ie smaller foundations and reduced ground disturbance). However,these advantages are outweighed by the size of the stabilising guys required (ieincreased ground-take) and problems with hot line maintenance where new procedureswould be required. This tower design was eventually ruled out when EGAT requestedthe standard ground clearance be increased from 11 metres to 16 metres.

2.4 The horizontal 3x3 portal tower also has low EMF levels due to reduced phase spacing;in addition, it is possible to increase the ground clearance of this design withoutexceeding the height of conventional towers. However, this design would haveintroduced even more significant problems for hot line maintenance as well as requiringsizeable stabilising guys, beams and columns. For these reasons, this design was alsodismisssed.

2.5 The traditional vertical tower with a single pole construction would also allow reducedEMF levels due to phase compaction and longer spans if 'V" insulation were used.However, this design also has maintenance difficulties and large, expensive foundationswhich may disturb land drainage. Tthese aspects of the design eventually ruled it outwhen EGAT requested the standard ground clearance be incraesed from 11 metres to16 metres.

2.6 Therefore, the preferred transmission line design became a conventional vertical steellattice tower. This design was optimised to produce a tower which is lighter and cheaper

than EGAT's existing 500 kV tower design, while having increased span capacity(reduced visual impact), reduced foundation loads (less ground disturbance) and reducedEMF levels due to phase compaction.

2.7 The final proposed double circuit 500 kV tower design is shown in Figure 5, next toEGAT's existing 500 kV design.

CONCLUSION

2.8 Four basic design concepts were considered before the conventional vertical steel latticetower was chosen. This was preferred because of its maintainability, reduced foundationloads (less ground disturbance for smaller foundations), longer span capacity (reducedvisual impact due to fewer towers) and reduced EMF levels (due to phase compaction).

Figure 2.1 Vertical 2x2x2 Portal Tower

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Figure 2.4 Traditional Vertical Tower of Steel Lattice Construction

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Figure 2.5 Comparison of Final Proposed Design with EGAT's Existing 500 kV Design

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CHAPTER 3

LANDSCAPE AND VISUAL IMPACT

INTRODUCTION

3.1 The aim of this chapter of the Environmental Report is to describe the existing landscapethrough which the proposed 500 kV transmission lines would pass. The potentiallandscape and visual impacts caused by the alterations to the network in the GreaterBangkok Area are also assessed.

ASSESSMENT

Landscape

3.2 The land along the Bangkok Noi - Sai Noi route is mainly open and agricultural in nature.Therefore, transmission lines can be observed over a long distance. There are somereal-estate projects in the vicinity, the land in the Right-of-Way being used as 'openspace", ie parks, lakes or treatment lakes/oxidation ponds (Photos 3.1 and 3.2).

3.3 Between Sai Noi and Rangsit, the land consists of agricultural land (paddy fields andveg;,etable plantations), dispersed housing and one major industrial area. The land isgenerally flat, and so transmission lines can again be seen from great distances. Thereare also a number of temples along this section of the Project (see Chapter 5), and acrossing of the Chao Phraya river. The existing two 230 kV towers on either bank arepainted yellow and white to aid visibility; all the remaining towers are grey. Finally, thereare many khlongs in this area; these are used for transportation and irrigation.

3.4 The transmission line route between Rangsit and Chaeng Watthana runs parallel withKhlong Prapa. The majority of this line passes through vacant land, some agriculturalareas and low density residential areas. Near Chaeng Watthana substation, thetransmission line passes through Muang Thong Thanee, a high-density residentialcomplex which includes some office buildings (Photo 3.3). People from Muang ThongThanee have their view of the sunrise crossed by the existing 230 kV transmission lines.

3.5 Finally, the Nong Chok - On Nuch transmission line passes through a mainly agriculturalarea comprising chicken farms, fish culture ponds and grass fields (which are for sale).There are also some housing projects, and khlongs are the major transportation meansin this area. In the future, this line route will have to cross a major road interchange (TabChang) which is currently under construction. The height of towers in this area willconsequently have to increase, and there will be a resultant increase in visual impact.

Visual Impact

3.6 Transmission lines can form relatively strong visual features in low-lying and flatlandscapes. The potential impacts occur when a transmission line (or any part of a line,such as a tower) intrudes into the view of receptors. The main visual receptors for thisProject would be residential.

1 2

3.7 The existing 230 kV transmission lines are judged to have a minor visual impact becausethey pass through mostly vacant and agricultural land in the suburbs of Bangkok. Thetowers are far apart, and from a long distance the transmission lines can barely beperceived because their colour is compatible with the sky and background. It is generallyagreed that the view of a transmission line is considered insignificant at a distance ofgreater than 2 km.

3.8 Interviews with key informants (see Chapter 4) revealed that residents did not feel theysuffered from any visual impact because the existing lines had been there for a long timeand they were 'familiar" objects.

3.9 The proposed 500 kV line design is superficially very similar to the existing 230 kV linedesigns. This is beneficial because local residents accept the existing structures and areunlikely to be concerned by the fact that the proposed line design has slightly largertowers (Figure 3.1) and more conductors. Distant views of the transmission lines will bealmost unchanged.

3.10 The visual impact of the proposed new 500 kV transmission lines compared to theexisting situation would be slightly greater, but would not be as significant as the visualimpact of constructing a new line in a landscape without transmission equipment. It istherefore better to increase the capacity of the existing network by replacing existing linesthan by building more, new lines.

MITIGATION

3.11 In the flat, open landscape typical of the area, transmission lines are often highly visible.The facts that the proposed 500 kV towers are slightly larger than the existing towers,and that the 500 kV lines would have more conductors than the 230 kV lines (fourcompared to either one or two), are compensated for by the superficial similarity of theproposed line design to the existing. Residents are familiar with these structures andaccept them as part of the Greater Bangkok Area landscape.

3.12 Given their height, any screening to mitigate the visual impact of the towers (particularlytheir upper extents) is difficult. Any such screening must be positioned close to thereceptor and, as such, would block views of the wider landscape. It is therefore notconsidered appropriate to suggest screening, such as general planting, for this Project.

3.13 TEAM's visual impact experts recommend that a light colour be used for the towers tominimise their visibility when viewed against the background environment, and the skyin particular. This means that the towers could be left galvanised or painted grey.

CONCLUSIONS

3.14 The proposed 500 kV transmission lines would pass through mainly open, agricultural orresidential areas. This means that they would be visible over a considerable distance (upto 2 km if there are no intervening features). However, distant views of the 500 kV lineswould be almost indistinguishable from views of the existing 230 kV lines. These areaccepted by the community as a familiar part of the landscape, and therefore the visualimpact of the Project woUld be small, and significantly less than the visual impact of aproject which introduced a new line into a landscape without transmission equipment.

-Photo 'A1: Existing ')30 k'J Transm.ssion Line C.03ss.ng Typica,l Rural Lancl

Photo 3.2: Existing 230 kV Transmission Line Crossing a Real-Estate Project

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Photo 3.3: Muang Thong Thanee Complex

15

Figure 3.1 ComDarison of ProDosed 500 kV Tower and Existing 230 kV Tower

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CHAPTER 4

SOCIO-ECONOMIC ASPECTS

INTRODUCTION

4.1 Potential socio-economic impacts arising from the dismantling of the existing 230 kV linesand construction and operation of the proposed 500 kV transmission lines were identified.The study considered the occupations, health, recreation and general living conditionsof people living close to the transmission lines. Public attitudes towards the Project werealso investigated.

ASSESSMENT

4.2 -- Communities in the study area were identified from topography and land-use mapsoverlaid with administrative maps. This work was confirmed by the field-work. Data wasthen collected from two sources:

= desk study: related documents were studied and analysed, eg subdistrict(Tambon) population records from the Department of Local Administration, andresearch reports on urban planning, marketing and law.

* field study: key-informants in various communities were interviewed to obtaintheir views about the Project and to discover their peopies' attitudes toward theproject.

Study Results

Documentary Review4.3 By taking topography and land use maps of the study area and overlaying them with the

administrative maps, it can be seen that the four sections of existing 230 kV transmissionline pass through many subdistricts of Bangkok, Nonthaburi and Pathum Thani (seeTable 4.1). Most areas adjacent to the existing Rights-of-Way for Bangkok Noi - Sai Noi,Sai Noi - Rangsit and Nong Chok - On Nuch are paddy fields, while the land adjacent tothe Rangsit-Chaeng Watthana Right-of-Way is mostly idle. There are few communitiesadjacent to the transmission lines. These have been divided into three categories; ruralor agricultural communities, semi-rural traditional communities and housing project orurban communities.

Field Data Collection4.4 TEAM interviewed six key informants on 21 and 22 February 1996. Two of these key

informants work for or own housing projects, while the others are community leaders.The key informants also relayed concerns from their villagers. Their details arepresented in Table 4.1. Baseline data for the potentially affected communities arepresented in Table 4.2.

4.5 Potential problems and impacts reported by the key informants relate to both theconstruction and the operational periods of both the existing 230 kV transmission linesand the proposed 500 kV transmission lines. They can be summarised as follows:

1-7

* Temporary dikes of paddy fields and fish ponds in the Right-of-Way weredamaged by construction equipment and vehicles during the construction of theexisting 230 kV transmission lines (village head of Ban Lam Nok Faek).

* TV interference from the existing lines already affects the villagers' TV reception,particularly those living close to the transmission line. This TV interference ismore frequent durinc the rains or damp (hiah humiditv\ nenrods (I(risada Nakhon18 and Ban Saeng Bua Thong). This subject is covered in detail in Chapter 11.

* The electric field from the existing line apparently causes fluorescent light bulbsto be brighter or causes them to light automatically during the rains or dampperiods (Ban Saeng Bua Thong).

* A concern that reduced ground clearance may obstruct community developmentor construction work in the area (Krisada Nakhon Housing Project 18).

* The visual impact of the transmission lines indirectly affected the real-estatebusiness of the Ban Saeng Bua Thong housing project. The Krisada Nakhon 18housing project managed to mitigate this impact by using the area in the Right-of-Way for recreation (a narrow lake). Consequently, the housing units closest tothe lake (and therefore also the existing transmission line) had been chosen firstby customers.

- ) * Residents are concerned about danger when commuting across the Right-of-Way, especially during rain or damp periods (Ban Saeng Bua Thong and BanKhiong Nai So).

4.6 In spite of the concerns listed above, all the key informants agreed with the proposed 500kV transmission line project. The reasons for this can be summarized as follows:

* The 500 kV project will be able to transmit electrical power efficiently andadequately for a consumption which has increased continuously.

* fThe project is necessary for economic growth and development of Thailand.

4.7 Most respondents' perception of the impact of the 500 kV transmission lines as comparedto the 230 kV lines was that the negative impacts would increase slightly because theRights-of-Way were remaining 40 metres wide. However, the key informant from KrisadaNakhon 18 was worried that residents living close to or commuting across the Right-of-Way may be endangered by the higher voltage and also that the TV interference wouldoccur more strongly than at present.

4.8 The key informants made some suggestions for implementation of the 500 kV Project:

* The vertical conductor-to-ground clearance should be greater than the existingline and according to international standards.

* A public relations program should be undertaken to inform farmers and/oragriculturalists who have land within the Rights-of-Way to avoid negative impactsfrom and to the 500 kV Project during construction. This should occur 3 to 4months in advance of construction for paddy fields and not less than 1 yearbefore construction for fish ponds.

* The transmission line towers and conductors should be visible from a longdistance.

* The transmission line towers and conductors should be insta!led carefully in orderto ensure the safety of both residents and workers.

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Potential Impacts

Construction Period4.9 Most of the areas which the existing 230 kV transmission lines pass through are

agricultural (especially paddy fields) and so the majority of affected people are farmersor agriculturalists. Construction work may disturb their daily living, interrupt their farmingactivities and damage their crops. The main activity which is likely to generate thoseimpacts is erecting new 500 kV towers at new positions.

4.10 In addition, the ability of residents to travel may be affected if their access roads crossconstruction areas.

4.11 Another possible impact during construction is due to conflict between residents and theProject's officers and workers. This problem may stem from:

* affected people having no information or understanding about the Project.- affected people not receiving adequate consideration and/or fair compensation.

* the Project's officers or workers behaving improperly.

Operational Period4.12 There was a feeling that residents living adjacent to or commuting across the Rights-of-

Way would be more worried because of the voltage increasing from 230 kV to 500 kV.The fact is that the proposed 500 kV transmission lines will still be safe because they willbe designed and built to international safety standards. Sufficient clearance would beprovided to enable the land Lunder ant near to the lines to be used nnrmarly. Hwn ever,care is always needed when carrying long ladders or irrigation pipes or using highmachinery under the lines.

4.13 Real-estate developments close to the Rights-of-Way may have difficulty marketingproperties in the vicinity of transmission lines because customers generally dislike the.alien" structures and worry about danger. However, there are already 230 kVtransmission lines and these have a similar impact to that of the proposed 500 kVtransmission lines. The incremental impact due to the change from 230 kV to 500 kVwould be minimal.

MITIGATION

4.14 Measures taken during the works and controlled by the contract for the work would seekto minimise disturbance and damage. These measures include protection ofwatercourses and reinstatement of damage such as accesses, gates, fences and dykes.Assets and crops or trees which are damaged by the construction work should beadequately compensated for. Where the farmer would prefer to carry out his ownreinstatement and be reimbursed by EGAT, this could be arranged.

4.15 Where roads would be crossed by construction of the new lines or dismantling of theexisting lines, all suitable precautions should be taken including the use of safetyequipment and appropriate signage to drivers warning of any hazard.

4.16 If complaints are received, a prompt response should be provided. The Project's officersand workers should maintain a good working relationship with the local people.

4.17 Residents should receive reliable information about the Project, including details of theProject aims and timescales, the possible impacts and the mitigative measures which areto be undertaken. Concerns about increased danger from the higher voltagetransmission lines would be addressed by a public education programme.

4.18 Problems associated with real-estate developments already exist due to the presence ofthe existing 230 kV transmission lin es. EGATs decision to increase the standard groundclearance required from 11 metres to 16 metres should allay concerns over interferencewith community development or construction work. The additional impact due to theproposed 500 kV transmission lines is therefore minimal, and no mitigative measures areproposed.

CONCLUSIONS

4.19 Impacts during the construction period mainly consist of disturbance to farming activities-. in the Rights-of-Way. This disturbance can be minimised by maintaining good

communication with affected landowners and considerate working practices.

4.20 Concerns during the operational period mainly relate to safety issues. Sufficientclearance would be provided to enable the land under and near to the new 500 kVtransmission lines to be used normally. However, care is always needed when carryinglong ladders or irrigation pipes or using high machinery under any overhead transmissionlines.

20

Table 4.1: Key Informants for Socio-economic Field Survey

Line Section Key Informant Location

Bangkok Noi - Sai Noi Chief of Social Facilities Krisada Nakhon 18 Housing ProjectDivision

Community Leader Ban Lat Kra Chet, Village No. 6,Bang Ku Rat Subdistrict

Sai Noi - Rangsit Owner Bang Saeng Bua Thong HousingProject, La Harn Subdistrict

Village Head Ban Kroen, Village No.1, Bang KraDee Subdistrict

Nong Chok - On Nuch Village Head Ban Lam Nok Faek, Village No.10,Saen Sab Subdistrict

Village Head Ban Khlong Nai So, Village No. 20,Minburi Subdistrict

Table 4.2: Community Baseline Data

Category Community Number of Households

housing project Krisada Nakhon 18 300Ban Saeng Bua Thong 125

agricultural Ban Lat Kra Chet 77

traditional semi-rural Ban Kroen 228Ban Lam Nok Faek 36Ban Khlong Nai So 90

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CHAPTER 5

CULTURAL HERITAGE

INTRODUCTION

5.1 The known archaeology and cultural heritage of the study area is outlined and thepossible impacts discussed. Since the proposed 500 kV development will be within theRights-of-Way of the existing 230 kV transmission lines, there will be no significant effecton cultural heritage other than small changes to the existing visual impact (as describedon Chapter 3) and a small possibility of disturbing archaeological remains.

ASSESSMENT

5.2 During the last week of February and the first week of March, 1996, field surveys wereconducted by TEAM along the four existing 230 kV transmission lines which will bereplaced by the proposed 500 kV transmission lines. In addition, a desk study ofarchaeological sites in the Greater Bangkok Area was also carried out. The objective ofthe surveys was to identify existing cultural or historical sites in the vicinity of the Rights-of-Way.

Temples and MosQues

5.3 The following temples and mosques were identified in within a corridor of 1 km either sideof the centre-lines of the existing 230 kV transmission lines:

* Wat Sai Noi (about 600 m to the east of Bangkok Noi - Sai Noi).* Wat Bang Khu Lat (about 900 m to the west of Bangkok Noi - Sai Noi).* Wat Bang Waeg (about 300 m to the east of Bangkok Noi - Sai Noi).* Ban Lam Ri Mosque (about 600 m to the south of Sai Noi - Rangsit).* Wat Saphan Sung (about 300 m to the south of Sai Noi - Rangsit).* Wat Nam Won (about 700 m to the north of Sai Noi - Rangsit).* Wat Chinwararam (about 500 m to the south of Sai Noi - Rangsit).* Wat Kroen (adjacent to Sai Noi - Rangsit).* Wat Daowadung Bon (about 400 m to the south of Sai Noi - Rangsit).* Wat Na Wong (about 900 m to the east of Rangsit - Chaeng Watthana).* Wat Weruwanaram (about 1 km to the east of Rangsit - Chaeng Watthana).

Wat Mai Lam Nok Khwaek (adjacent to the Nong Chok - On Nuch).* Wat Thong Samrit (about 800 m to the north of Nong Chok - On Nuch).* Wat Pak Bung (about 600 m to the south of Nong Chok - On Nuch).* Wat Lat Bua Khao (about 700 m to the east of Nong Chok - On Nuch).- * Wat Damrongsatthatham (in front of On Nuch Substation)* Thab Chang Mosque (about 800 m to the northeast of Nong Chok - On Nuch).

5.4 Only two temples are located adjacent to the existing 230 kV transmission lines, namelyWat Kroen and Wat Mai Lam Nok Khwaek. At these sites, the existing 230 kVtransmission line can be seen over the temples as a component of their view. For othertemples and mosques within 1 km of the centre-line, the transmission lines andsupporting structures could not be clearly observed within their visual context.

.TX2

Archaeol-ciy

5.5 There were no archaeological findings reported during construction of the existing 230kV transmission lines, and no findings have been recorded within the existing Right-of-Way. The nearest archaeological evidence was found in the heart of Bangkok, at KoRattanakosin and Krung Thonburi (see Figure 5.1). This consisted of ancient cannonsandu boats.

5.6 Potential disturbance to archaeological remains only occurs during construction activities;there would be no impact due to the operation of the proposed 500 kV transmission lines.

MITIGATION

5.7 For the majority of the cultural sites identified, the proposed transmission lines will not beclearly observable within their visual context and so no mitigation measures areproposed. For the two temples which are adjacent to the proposed 500 kV lines, the

- presence of the existing 230 kV lines means that any additional visual detriment will besmall.

5.8 The project area is a long way from known archaeological finds; it is therefore unlikelythat any site of archaeological importance will be disturbed by the construction activities.In addition, a significant percentage (between 23 and 32%) of the proposed 500 kVtowers will be sited over the foundations of the existing 230 kV towers (see Chapter 6).This will minimise the amount of additional ground disturbance, and therefore thelikelihood of disturbing archaeological remains.

5.9 In the event of significant remains being identified, EGAT would aim to minimise damageand, if appropriate, seek alternative tower locations. Otherwise, arrangements would bemade for a suitable level of site recording of archaeological remains prior to and/or duringconstruction works.

CONCLUSIONS

5.10 The potential impacts from the Project consist of the loss of or damage to sites ofarchaeological importance and the adverse impact on the setting of cultural sites.

5.11 It is anticipated that the small increase in the size of the towers would not materiallyaffect the setting of sites. Therefore, no known sites of cultural or historical interestwould be affected more adversely than they already are by the existing 230 kVtransmission lines.

5.12 There are no known archaeological sites along the existing Rights-of-Way, and it isunlikely that any will be found. If significant remains were found, damage to the sitewould be limited as far as was practicable and a suitable level of site recording would bearranged prior to and/or during construction works.

23

NONTh1A RniPj

GRAPHIC SCALE

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CHAPTER 6

LAND USE

INTRODUCTI ON

6.1 A field survey of land uses was conducted along the existing four sections of 230 kVtransmission line by TEAM during the last week of February, 1996.

6.2 The construction of the proposed 500 kV lines would temporarily affect some land usesalong the route. In the longer term, the physical presence of the proposed towers andconductors would affect farming operations to some extent. There may also be anoccasional need for access to land to inspect, maintain, adjust, alter, replace or repair thetransmission lines.

ASSESSMENT

6.3 The land use results from the field survey along the existing 230 kV transmission linesare presented in Table 6.1. This information is also presented graphically in Figures 6.1to 6.5. The main land use within the area is agriculture, in particular paddy fields (56%),b,utI also ru. and vegetabie cuitivation and poultry and fish farming. Other land usesinclude urban (ie housing), institutional land (eg schools and temples), and a smallamount of industry. 16% of the land has been abandoned.

Potential Impacts During Construction

6.4 Dismantling of the existing 230 kV lines and construction of the proposed 500 kV lineswould cause temporary interference to agriculture on land used for access and/ormaterials storage.

Potential Impacts During Operation

6.5 During operation of the line, only the area immediately beneath each tower would beremoved from cultivation. In addition, the immediate tower surroundings would take onthe characteristics of field margins, ie typically having slightly lower yields and a greaterchance of weed problems. This impact has already occurred due to the presence of theexisting 230 kV line and therefore it is expected that any further change to the land usepatterns along the proposed routes will be minimal.

6.6 Additional, temporary disruption may also occur when access is required for maintenanceor repair of the proposed 500 kV line.

MITIGATION

6.7 During construction, because the Project consists of a linear development, it is unlikelythat any one area would be compromised for more than one growing season.Landowners will be informed of work schedules in advance so that they can planaccordingly. Any damage to land (eg to temporary dikes in paddy fields and fish ponds)

A,>5

will be reinstated by EGAT, or appropriate compensation agreed where this is notpossible.

6.8 Disturbance to land will also be minimised because a signifcant percentage of the newtowers would be located on the site of existing towers. Until the final tower spottingexercise, precise statistics are not available. However alonn Bangkok Noi - Sal Nol,between 14 and 23 towers out of a total of 68 will be located at existing positions (iebetween 20 and 33%). Along Sai Noi - Rangsit, of a total of 59 towers, between 19 and25% will be at existing locations. There are only 20 towers between Rangsit and ChaengWatthana, and between 6 and 8 of these will be at existing positions. Finally, of the 40double circuit towers between Nong Chok and On Nuch, between 14 and 16(representing 35 to 41 %) will be located on existing sites.

6.9 During operation, routine maintenance would be arranged with the landowner to avoidtimes when the crop is sensitive and therefore minimise any disruption. When urgentmaintenance or repair is needed, EGAT would seek to minimise any disruption causedby access and working.

CONCLUSION

6.10 The main land use along the proposed routes is agricultural. Disturbance caused duringdismantling the existing 230 kV line and constructing the proposed 500 kV line would beminimised by liaising with the local landowners and choosing appropriate working times.

6.11 Impacts due to the operation of the proposed 500 kV lines already exist along the chosenroutes because of the presence of the existing 230 kV lines, and would be minimised bythe re-use of existing tower sites where practicable.

2 Lb

Table 6.1 Land Use Categories along the Proposed 500 kV Transmission Lines

Land Use Categories: Coverage in hectaresTransmission LinesIU2 U3 U5 Al A4.1 A5.1 A8 A9.1 Al A1 U2 M1 W

A9.1 M1 A4.1Bangkok Noi - Sai Noi 6.50 1.25 - 100.5 3.50 11.25 - 11.25 1.75 12.00Sai Noi - Rangsit 8.75 12.50 0.75 88.75 0.50 2.25 - - 1.50 10.00Rangsit - Chaeng Watthana - 2.00 - - - 2.00 - - - 34.00Nong Chok - On Nuch 16.50 5.00 - 36.50 - - 3.00 3.00 3.00 15.50 - 7.75 2.75% of Total Land Area _ 7.86 5.14 0.19 55.88 0.99 3.84 0.74 0.74 0.74 6.62 0.80 15.78 0.68

U2 UrbanU3 Institutional LandU5 Industrial LandAl Paddy FieldA4.1 Mixed OrchardsA5.1 VegetablesA8 Poultry Farm and Fish PondA9.1 Fish PondMl Idle LandW Water Body

027

5e SINGLE HOUSE INDUSTRIAL PLANT

ROW HOUSE RONG RIAN (SCHOOL)

HIGHRISE BUILDING

0 X ILARGE BUILDING 4AGRICIULTURAL AREA

Figure 6.1 Definition of Landscape Elements

K CJ kJ ~~~ ~ ~ ~~~~ri r t i+or.

-~~~~~~~ - -

| r40.000 E 645,000 E 650.000 E 655,000 ELj

SWt \ ~ \-i /1,545,000 Nq,4\ $ s , ~~~~BAN KHLONG CHEK (2)|o 2KU

" \.At > WAT AND RONG FIAN WAT SAI NOI | GRAPHIC SCALE

BAN KHLDNG TA SANG (I)< .tJ X

645,000 E\ 6500.00. 0 605.000 E 660.000 E 5000 } 'K 670.000EN,~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~ ~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~N

/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ BAN

r -I I I I I I I I I r 650,000 E -54~

_ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 . \1 o,2 KM._ \_3 1 \ ; t GRAPHIC SCALE

I.545,00() N I\o ....\|4o9

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\8 8 :1 \ \8 - ~~~~~~~~~~~~~~~~~~~KHLONG ;t- i---t- ! IRAILWAY

.sr l. \ -SINGLE HOUSE

_ t le , d/ROW HOUSE

-l ; ,N\/HIGHRISE BUILDING

mJ LARGE BUILDING

- TEPPRATARN HUA6E INDUSTRIAL PLANT

/ '. \D D D * 49/ i RONG RIAN (SCHOOL)

\UANG THON A WAT WERUWANARAM A TEP0 ~~~~~~~~~~~~~~~~~~~~AGRICULTURAL AREA

/ \ 0 LJ Ll * t§> 4t/J/ 0 U L

\ 7i4e;vH~~~~~~AKORN KARNBIN lHA] 2/ /

_ \ n h 4 R~~~~~~~~~~~~~~UNGARUN MLLAGE 7/9 \ X

\ ~~~~~~CHATRADA VILLAGE e ? %% ~~~~g = ~~~CHOKPRACHA VILLA1 |/ R/ /

POOPU MLA 3 X/s' 1,535,00Lt N \ PRACHANUPPRILAlHUSH //

,, \ PRACHAHIVES VILLAGE /| CHEUJNKAMOL NIVAS I 1

\WT BUA KHWAN let/ // @ ' @ ~~~~~~~~CHEUNKAML)L NIVAS 2 //w

- \TH~~~~~ANAKARN SONGKAO UAE|g RATANA THU8 E T It, /- // R

_ ~~~~~~~~~KA TPRAPH A -- -----------

- / s I X * /A/ /~~I X

-1,530,000 N |//

Figure 6.4: Landscape Along Rangsit - Chaeng Watthana Route

r - r r r - T I r , 1 1 LT r X T r - r r- I~~~~~~~~~~~~~~~~~~T 6800000 E 5.OE69000 E 695.000 E 700.000 EBAN LAW MOK < 'WE 0 1 2 KM.

GRAPHIC SCALE

1.523.00) N

LEGEND

is// / ,.'BW 26> v 8AN K ONG SAM N..15 Hi/.' . HIGHWAY ROAD

so / A SO t-I- -i RAILWAY

2 9 />J > z ~~~~~~~~~~~~~~KHWANG LAM PLATIU /-*SNL OSSINGLE HOUSE

2 tAT 7 RATC&I^CIX/ ' . _ / S ROW HOUSEBAN,'KOLONO JP CNANC B°,,84 r RKHWANG KHLONG SONG N NU . HIGHRISE BUILDING

-1 LARGE BUILDING

1,520,COP( NL / E KHLONC I 1 I A INDIUSTRIAL PLANT

KHET BANG " ^ S 2 * i _ PONG RIAN (SCHOOL)Al TEMPLE

RON0 RIANJ SURAO THAP CH-AE AGRICUJLTURAL AE

.AT DA.-08 SAT.1101 BAN PAKl KHLONGBEON

t / KHWAG LAI KRAANG

1.515.000 N !ILI _ ILI I I I I 1- 1 _ ___Fig I -ILdcp ln I L N Chok ___ _

FIgure 6.5: Landscape Along Nong Chok - On Nuch

B.-

Ij c - iINDUSTRIAL PLANT . SINGLE HIOUSE

RONG RIAN (SCHOOL) RO(W HOUISE

HIGHRISE BUILDING

A GRICULTURAL AREA LARGE BUILDING

FIGURE 2 LANDSCAPE ALONG 500 KV TRANSMISSION LINE FIGURE 1 LANDSCAPE ALONG 500 KV TRANSMISSION IINE

wo. rw C t . . v # .s. ._E~~~~~~

~~~I I I I I I I I I I I - - 1 I640,000 C 65.000 t I 55.000 E

K~~~~~~~~~~~~~~~~~~AMP0CA SAl NOI

1 545,000 7I'5A ' CHtK l2) 0 1 2KU

_ AND ROANG RIAN A11 SA, NO GRAPHIC SCALE

, 6-N OAIKJN( 2) | - ! \j -

AIRIN WlO,NG t. SANG (1) 4

'6 tlU HL0UC TA CHO 1\ \//

HIGHWAY ROAD

- sai

_ i | 9 *|- \ | - -- ~~~~~~~~~~~~~~~~~~~~KHLONG\f I J _ || | RAILWAY

-\ \ 9 , io 8A~~~~~~~ NONG KRADI11(2) ..\_

_ _ , 12 *| * 5 s . S INGLE HOUSE

.Iurx wHLONs sl Ut* * * i 6ANX WN SA1NAf/ .. l j ROW HOUSE0 HIGHRISE BUILDING

\\ 6AN N 0"G PHLAO N CAU,(3)l ^| * i / \ t \ H535.000 U -a LARGE BUILDIIf

4*\ , | \ - d INDUSTRIAL PLANT

RDNG RIAN (SCHOOL)

\B\ _____ \_ | | X 6AN KHL GC IA UIUANC, \ 40t / X I _ TEMPLE

\\ Lo A.0 I .LU ,1~AGRIOLJLTU1IAL AREA

\\,N T0IK CHU^ B,* AN ITALAT SANG KHV > ;

n BAN BANC YAI (3)) : *\ ' /X\\ \

- BAR UA (1) Z \ \ )

BAN KHLONG SANG SANO

. \ HAN KHLONC BANC KA HLO N \ IAH

P0116 P101 6 lIlAt PAN K 6AN W1A "0KUN SRI -525,000 N

L W^N TALIN~~~~C. C iJ BAN KLANC NA (2) /@,.

(3\ BAN KHLONC AAN Pl - .-

- A \ |} FAN KHLGUC 6ANG I X (TI s ~~~~~~~~1,520,000 N-

\ r 8AN KHL 6ANCWAEK (1)

BANR[7HAIT I) _ . . .... .. 1512000

FIGURE LANI)SCAPE ALONG 500 KV TRANSMISSION LINE

-' L BANGKOK NOI SUBSTATION - SAI NOI SUBSTATION

-NW ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~-

RANG $RAD

-v -- HIGH W AY .NOUSTRIAI. RHTA

t [, 2 = KHONC aD ROW H0USE s RONG RlS XSCHCNN NNA .-)(310

. .

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) N.~~~~~~~~1,..0 N

N ~~~~~~~~~~~~~~~~~LEGEND- HICHWAY ROAD '- SINGLE HOUSE d INDUJSTRIAL PLANT

Sol ~~~~~~~ROW HOUJSE RONG RIAN (SCHOOL)KHLONG

210' -H4+± ~~~~~~~ ~ ~ ~~~~~RAILWAY 0 HIGHRISE DUJILDING T EM-PLE

GRAPHIC SCALE ~~~~~~~~~~~~~~~~~~~~~~~C LARGE BUILDING AGRICUTURAL AREA

FIGURE LANDSCAPE ALONG 500 KV TRANSMISSION LINE

.4.-3 SAI NOI SUBSTATION - RANG SIT SUBSTATION

-/ /,,."

l~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I 91 iA I40 K I IWI I I I (IA_. -

SaOtoo r \ ses,aoo E ~~~~~~~~ ~ ~ ~~~~ ~~~~690,GOO E \ 6 95.000 E _1700.000 E_.

.. -' \ \ ............................... / \ |~~~~~~I-A \-_ 18A1u OK HtEK , 2 KIA.

GRAPHIC SCALE

/B_ : t 0AN KE LONC SAW No..I5 HIGHWAY ROAO

Sol

so / L X 8AN KHt0NC Afl S0 OFf > _KHLONG-I/-H-+--t |RAILWAY

- - ~~~~~~~~~~~~~~~~KHWANG LAM I'LATlU-/ r > S KHWANG LAU PLAnU / -e SINGLE HOUSE

_ _ an ROW HOUSERAl (HI.ONT IHAP CIIANO 8 / l KHWANG I'KHLONG SONG N NUt r HIGHRISE BUILOING

-t.5200o2N ~/ .1.I I 'BAN MA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~LARGE BUILDING_.2000 / 1 8^N KHLONC U^1 CHAN \ ( y INOUSTRIAL PLANT

RONG RIAN (SCHOOL)|r / It KHET LAT KRABANGIE EPLE

RONG -RI+,|| p 4; + - AGRICULTUFAU L AREA

/- A / lO§CJLAT KRA9iC / -| LA

I I I I I I I ! I I I I I I I I~ ~ ~~ ~ I I I I I I

FIGUPE V' LANDSCAPE ALONG 500 KV TRANSMISSION LINE

NONG CHOCK SUBSTATION - ON NUCH SUBSTATION

CHAPTER 7

WATER QUALITY

INTRODUCTION

7.1 Due to the location of the Greater Bangkok Area in the central plain of the Chao Phrayariver, many of the khlongs and waterways were crossed during the 230 kV transmissionline development. A list of affected water courses is presented in Table 7.1. Thesewaterways will potentially be the receptors of any aquatic pollution generated by the 500kV transmission line development.

7.2 Although the proposed 500 kV development will be limited to the existing Rights-of-Way,-- the construction activities will still involve soil disturbance and the use of heavy

machinery. Therefore, there may be some impact on the local water quality in the formof additional suspended solids and spills of oil or grease during the construction period.

ASSESSMENT

7.3 Data has been collected on the existing water quality data as the baseline for futureimpact assessment. A sampling program was undertaken by TEAM on 8 and 9 February,1996. to examine the existing w'ater quality along t Ri,gh+-of-Way. 'Te sampiingstations were as follows:

i Station 1: Khlong Prapa, near Ngam Wong Wan IntersectionKhlong Prapa at the sampling point was about 20 m wide, with quite turbid waterof a brownish colour. The flow was relatively low. No floating weeds or garbagewas observed in Khlong Prapa. This station was located about 20 m from theedge of the existing 230 kV transmission line Right-of-Way.

* Station 2: Chao Phraya River at Wat Kroen, Tambon Bang Kra Dee, AmphoeMuang, Changwat Phrathum ThaniThis station was located at the pier in front of Wat Kroen, about 15 m from theriver bank. This area suffered in the flood of November 1995. The water was

) relatively clear with normal flow. Water hyacinth were present along the riverbank. Upstream and downstream from the sampling station, there were 5-10sand barges docking along the bank. In addition, a tapioca factory was locatednext to the wat and a log terminal was approximately 100 m away. This samplingpoint was about 50 m from the 230 kV transmission line Right-of-Way.

* Station 3: Khlong Phra Pimon at Wat Sai Noi, Tambon Sai Noi, Amphoe SaiNoi, Changwat NonthaburiThis station was in front of Wat Sai Noi. The khlong was densely covered withwater hyacinth, although an H2S odour was perceptible from the khlong where thewater was blackish. Small communities were observed on the bank opposite WatSai Noi. This station was about 50 m from the existing transmission line Right-of-Way.

7.4 Analysis of the samples revealed that the quality of the waterways during the dry season(February, 1996) was relatively consistent (Table 7.2). The water temperature rangedfrom 25 to 270C and the pH from 8.0 to 8.7. The conductivity was found to be relativelylow in Khlong Prapa (230 pmho/cm) and up to 320 pmho/cm in Khlong Phra Phimon (due

1'33

to the high levels of H2S dissolved in the water). This high conductivity also correlatedvith a relatively high total solids of 412 mg/l and a relatively low dissolved oxygen (DO)of 3.9 mg/l in Khlong Phra Phimon.

7.5 Overall, the water in Khlong Prapa and the Chao Phraya was soft (alkalinity of 88-92mg/I) with relatively high DO (ahout 6 mng/). 0! and nrease contamination was detectedat the relatively high concentration of about 2.0 mg/l. From the above analyses, the threewaterways, ie Khlong Prapa, the Chao Phraya river (at Wat Dao Wadung) and KhlongPhra Phimon, can be classified as rank 3, 3 and 4 according to the Ministry of Science,Technology and Environment (MOSTE) standard (Reference 7.1). Definitions of thesewater quality classes are given in Tables 7.3 and 7.4.

Potential Impacts

7.6 As operation of a high voltage transmission line does not involve any emissions, the onlypotential long-term impact on water resources consists of alteration to drainage patternsdue to the interruption of existing drainage.

-;) 7.7 The major potential impacts on water quality arise from construction activities and are asfollows:

* surface run-off from the construction sites.* wastewater from the temporary office and construction camps.* wastewater contaminated with oil or grease from machinery.

7.8 Surface run-off from construction sites will have increased suspended solids due to thesoil disturbance associated with tower foundation construction. The potential impact willbe minimised because only the relatively small area around the tower base will beaffected. Therefore, the potential impact due to increased suspended solids in surfacerun-off is not expected to be significant.

7.9 Dismantling the existing 230 kV transmission lines will involve minimal soil disturbancebecause, in general, the towers will be removed to ground level and the concretefoundations left in place.

7.10 Temporary offices and construction camps will be equipped with sanitary latrines whichwill take care of all domestic waste prior to discharge into nearby waterways. Thus thepotential negative impact of wastewater disposal is negligible.

7.11 The 500 kV transmission line development will utilize a large amount of heavy machineryand construction equipment. Routine maintenance of this equipment will be restricted towithin designated maintenance areas or garages. In these facilities, waste oil will becontained in designated containers and properly disposed of. Therefore, any potentialimpact due to oily contamination should not occur.

7.12 There will be no adverse effects on water quality due to the operation of the proposed500 kV transmission lines.

,Z 3 L 4

MiTIGATION

7.13 The Rights-of-Way for the 500 kV transmission lines already exist because of the 230 kVdevelopment. Therefore, only minimal additional clearing will be necessary.

7.14 Detailed tower locations would be agreed with reference to protection of existing drainageand dikes. Crossing of ditches and drains (where necessary) would be carried out by theconstruction of temporary bridges, able to bear the weight of plant and loads withoutdamage to the integrity of the watercourse. Where any field drains or dike systems aredisturbed during construction, these would be reinstated.

7.15 Surface run-off from construction sites will mainly be a problem in the rainy season. Themajor construction activities will therefore be scheduled for the dry season (November -April). In addition, the area disturbed during tower construction will be kept to a minimum.

7.16 Good housekeeping procedures will minimize any potential water contamination due to- oily waste and chemicals. Adequate sanitary latrines will be constructed at all temporary

-_) offices and construction camps.-,

CONCLUSIONS

7.17 The fact that the proposed 500 kV transmission lines are to be built in existing Rights-of-Way means that the impact on water quality in the area is expected to be small. Thissmnal impact w,ll be further, estricted by working in the d,y season (when practicable) andby proper control of wastewater from the construction sites.

7.18 There will be no impact on water quality during the operational phase of the 500 kVtransmission line project. This is because there are no emissions caused by theoperation of a high voltage transmission line, and because care will be taken not tointerfere with existing drainage patterns.

35

Table 7.1: Waterways Potehtially Affected by the 500 kV Transmission Line Development

Route Waterway Name Class

Bangkok Noi - Sai Noi Kh!onr' Phra Phinom 4Khlong Ta ChomKhlong Nai LikKhlong Som NukKhlong Bang YaiKhlong MahasawatKhlong Bang NoiKhlong Bang Chuk NangKhlong Bang PhaiKhlong Bang Weak

. - Khlong Bang Khi KaengKhlong Bang Chak

Sai Noi - Rangsit Khlong Lam RiKhlong Lak KhonKhlong Lam PhoKhlong Lam YaiKhlong Bang TanaiKhlong Ko KriangKhlong Bang Khu Wat TaiKhlong Bang Khu Wat NuaChao Phraya River 3

Rangsit - Chaeng Watthana Khlong Rangsit Prayoonsak 3Khlong Ban MaiKhlong Bang TaladKhlong Bang Khem 5

Nong Chok- On Nuch Khlong Mae ChanKhlong Lam Bung KhwangKhlong Al SoKhlong Song Ton NunKhlong SamKhlong SiKhlong Lam Phaeng PhouyKhlong Bung YaiKhlong Lam Nok KhwaekKhlonq Lad U-Ta-Phao

4t36

Table 7.2: Results of TEAM Surface Water Quality Survey (9 February 1996)

l___ .____ Water QualityZ Parameters Khlong Prapa Chao Phraya river Khlong Phra

Phimon

air temperature in °C 26 25 29water temperature in DC 25 *25 27depth in metres 2.5 2.0 2.7transparency in metres 0.5 0.5 0.5pH 8.7 8.2 8.0Conductivity in pmho 230 250 320turbidity in NTU 58.0 45.0 29.0alkalinity in mg/I 88.0 92.0 112.0total solids in mg/I 360.0 372.0 412.0suspended solids in mg/l 67.5 47.0 38.0hardness in mg/l 111 107 129DO in mg/l 6.0 5.9 3.9oil & grease in mg/l 2.2 2.0 2.2NO3 - N in mg/l 0.62 0.71 0.53cloud cover in % 0 0 0time of sampling 1000 1130 1400Class e Table 7.4) 3 3

i~~~~~~~~~~~~~"1

Table 7.3: MOSTE Surface Water Quality Classification (Reference 7.1)

[arameters U n Standard Values for Class (see Table 7.4)Parameters Units j StatistiC 1 2 3 | 4 | 5

temperature n' n' n n'pH n 5 9 5 9 5-9DO mg/l P20 n 6 4 2 -BOD (5 days, mg/I P80 n 1.5 2.0 4.0 -

20 °0)coliform bacteria- total MPN/100 ml P80 n 5,000 20,000- fecal MPN/100 ml P80 n 1,000 4,000NO3 - N mg/i max n 5.0 5.0 5.0NH3- N mg/l max n 0.5 0.5 0.5phenols mg/i max n 0.005 0.005 0.005Cu mg/I max n 0.1 0.1 0.1Ni mg/l max n 0.1 0.1 0.1Mn mg/I max n 1.0 1.0 1.0 -Zn mg/! max n 1.0 1.0 1.0 -Cd mg/l max n 0.005* 0.05** 0.05**Cr (hexavalent) mg/i max n 0.05 0.05 0.05Pb mg/I max n 0.05 0.05 0.05 -Hg (total) mg/l max n 0.002 0.002 0.002 -As mg/l max n 0.01 0.01 0.01CN mg/I max n 0.005 0.005 0.005Radioactivity- gross Bq/l max n 0.1 0.1 0.1- gross Bq/l max n 1.0 1.0 1.0Pesticides- DDT mg/i max n 0.05 0.05 0.05- BHC mg/l max n 1.0 1.0 1.0- Dielrin mg/l max n 0.02 0.02 0.02- Aldrin mg/i max n 0.1 0.1 0.1- Heptachlor &Heptachlor mg/I max n 0.1 0.1 0.1epoxide- Endrin mg/l max n none none none

no valuen' expected ambient temperature, but changing by less than 30Cn expected naturally occurring concentrationP percentile value* 0.05 mg/l when water hardness not more than 100 mg/l CaCO3

0.05 mgA when water hardness more than 100 mg/l CaCO3

Table 7.4: MOSTE Surface Water Quality Classification (Reference 7.1)

Classifications Condition and Beneficial Usages

Class 1 Extra clean, fresh surface water resources, suitable for:(1) conservation (water treatment not required, only ordinary processesfor destruction of pathogens)(2) ecosystem conservation (where basic living organisms canproliferate and breed naturally)

Class 2 Very clean, fresh surface water resources, suitable for:| . (1) consumption (but requiring ordinary water treatment before use)

(2) aquatic organism conservation (may be in support of fisheries)(3) fisheries(4) recreation

Class 3 Medium clean, fresh surface water resources, suitable for:(1) consumption (following ordinary water treatment before use)(2) agriculture

Class 4 Fairly clean, fresh surface water resources, suitable for:(1) consumption (but requiring special water treatment before use)(2) industry(3) other activities

Class 5 The resources which are not covered by Classes 1 to 4, suitable for:(1) navigation

,J~~~~~~~~~~~~~~~~re

CHAPTER 8

FLORA AND FAUNA

INTRODUCTION

8.1 Potential impacts to the ecology of an area from the construction and operation of a newtransmission line normally include loss of habitats (mainly at tower bases), loss ofspecies due to habitat loss, fragmentation of habitats, severance of ecological corridorsand disturbance to bird feeding or roosting activities.

8.2 The four sections of proposed 500 kV transmission line pass through the Bangkok-. Metropolitan Area, which has already been developed into a combination of residential,

N industrial and agricultural land. Therefore, there is little wild flora or fauna remaining inthe Rights-of-Way. In addition, the presence of the existing 230 kV transmission linesmean that any ecological impacts mainly already exist.

8.3 The assessment of flora and fauna has therefore been divided into two parts; potentialimpacts on the aquatic ecosystem due to an increase in suspended solids in adjacentwaterways (mainly of concern should construction activities take place during the rainyseason = sec Chapter 7) and other considerations assocaited with bird fiight paths.

ASSESSMENT

Aqati Ecology

8.4 Three waterways were selected as representative of the waterways potentially affectedby the proposed development. These were Khlong Prapa, Chao Phraya river and KhlongPhra Phimon. The sampling stations used by TEAM for their initial study were the sameas those used for the water quality study (Chapter 7).

8.5 All three watercourses were found to be dominated by phytoplankton (Table 8.1).However the dominant genus was different in each case. Coscinodiscus gigas was thedominant genus for Khlong Prapa, while Oscillatoria sp. and Microspora sp. were thedominant genera for Chao Phraya river and Khlong Phra Phimon respectively. Theoverall cell densities for Khlong Phra P,imon, Chao Phraya river and Khlong Prapa were3.4 x 1 06, 2.0 x 1 05 and 1.8 x 1 05 cellsiM3 respectively.

8.6 Using the planktonic indicator species for water quality (Table 8.3), Ceratium sp. (anindicative species for moderate levels of pollution) was identified only in Khlong Prapa.

- Oscillatoria sp., Fragilaria sp., and Spiruline sp. were found in high densities in the ChaoPhraya river and Khlong Phra Phimon; these indicate a relatively high pollution load.

8.7 No benthic species were collected from Khlong Prapa due to the strong flow and driftingof the sediment (Table 8.4). The density and diversity of benthos were also low at ChaoPhraya river and Khlong Phra Phimon. Only three genus were collected; Tubificid wormwas the dominant group. The tubifex worm is associated with high pollution loadsbecause it can survive in very poor environmental conditions, ie low DO, high BiologicalOxygen Demand (BOD) and high H2S levels (Table 8.5).

8.8 Therefore, this initial survey indicates that the three sampling locations are not idealaquatic ecosystems; this corresponds with the analyses of water quality contained inChapter 7. Bearing in mind that the new 500 kV development will be located within theexisting 230 kV Rights-of-Way, and thus only minimal additional land clearing will berequired, and the fact that the waterways around the project area are already in arelatively poor condition ecologically, the impact on aquatic ecosystems will be relativelyrninor.

Bird Flight pathsa

8.9 There is extensive data on which bird species are most at risk from injury or fatal collisionwith transmission lines. Generally, the birds most likely to be at risk are large specieswith poor flight manoeuvrability (and occasionally poor visual acuity) or birds with highflight speeds (such as birds of prey).

8.10 Significant flocks of birds usually fly along the shoreline or mountain ridges. The study- - area is concentrated on the plains of the Chao Phraya river, and therefore major bird

movements would not be expected in this area. TEAM's wildlife expert indicated that theonly known migratory bird in this region is the Barn Swallow (Hirundo rustica) which flieseach winter from its Siberian breeding grounds to the central business district of Bangkok(Silom). They arrive from the north, and therefore the proposed 500 kV transmissionlines would not obstruct their passage.

8.11 There are no records of birds being injured by collision with existing EGAT transmissionlines (including the existing 230 kV lines) in Thailand.

MITIGATION

8.12 As already stated, there are no sites of significant ecological interest in the vicinity of theproposed 500 kV transmission lines. However, general guidelines would be followed topreserve the existing wildlife potential. Damage to trees, dyke systems and grasslandwould be avoided where possible. Where the lines would pass over or close to treeswhich could infringe safety clearances to live conductors, the trees would only beremoved if absolutely necessary; preferably, they would be 'lopped" prior to theconstruction of the lines.

Aquatic Ecog y

8.13 The mitigative measures already described in Chapter 7 (to maintain the quality ofwaterways in the study area) will also minimise distUrbance to the aquatic ecosystems.These measures included minimizing the disturbed area during construction,concentrating the major construction activities during dry season (November - April),minimizing any potential contamination due to the oily waste and chemicals by goodhousekeeping and constructing sanitary latrines at all temporary offices and constructioncamps.

Bird Flight paths

8.14 Although there is no evidence to suggest that the proposed 500 kV transmission lineswould present a risk to birds, if a problem with bird fatalities were to arise, the possibilityof placing "deflectors" or 'markers" on the shieldwire to make the line more visible to birdswould be examined.

A-i

CONCLUSIONS

8.15 The existing 230 kV lines are in an area which has already been developed for a mixtureof residential, industrial and agricultural uses. Therefore, there is little wild flora or faunaleft in the study area.

8.16 TEAM's aquatic ecology survey indicated that the ecosystems present in the waterwayswhich could potentially be affected by construction work are already poor. If themitigative measures proposed in Chapter 7 (to maintain water quality) are applied, thepotential disturbance to aquatic life is minimal. No impact is expected on aquatic ecologyduring the operational phase.

8.17 There is no evidence of an existing risk to birds caused by the operation of EGAT'sexisting transmission lines. There is therefore no reason to suppose that there will be asignificant risk to birds posed by the proposed 500 kV lines.

iL.2

Table 8.1: Species and AbUndances of Phytoplankton

Abundances in cells/m3

PhylumScientific Names Chao Phraya Khlong Phra

Khlonn Prapa river mon

Bacillariophyta (diatom)Coscinodiscus gigas 85,100 15,200 17,100C. nitidus 2,300Diatoma elongatum 6,900 7,600 133,000Synedra tabulata 2,300 2,533 60,800S. affinis 2,300 2,533 -S. ulna - 11,400Ethmodiscus gazellae 2,300 -Melosira sp. 2,300 - 5,700Surfrella robusta - 1,900Bacillaria sp. 7,600Pleurosigma sp. 5,700Fragilaria construens 1,900Gyrosigma sp. - 3,800

Cyanophyta (blue green algae)Oscillatoria sp. 4,600 38,000 1,164,700Dictyosphacrium pul/chellumr 2,533 -Rivularia sp. 2,533 7,600Spirulina major - 7,600Lyngbya contorta - 3,800Trichodesmium lacustre 1,900Tribonema sp. 1,900

Chlorophyta (green algae)Spirogyra ionia 4,600 . 7,600Pediastrum simplex 2,300 5,700P. biradiatom - 22,800Derbesia sp. - 10,133 11,400Basicladia chelonum 2,533 -Microspora sp. - 25,333 1,369,900Closterium gracilo - 100,700Cl. cornu - 24,700Cl. ehrenbergii - 1,900Cl. moniliforme - 1,900

Euglenophyta (Euglenoids)Eugelna acus 39,100 - -E. granulata 6,900 - -Phacus pleuronectes - 1,900P. longicauds ' 1,900

Pyrrophyta (dinoflagellates)Ceratium furca 4,600 - -

Unidentified 1 2.533 5,700

|TotalI 165,600 _ 111,464 | 2,992,500 _

4-3

Table 8.1: Species and Abundances of Zooplankton

Abundances in cells/mr3

Phylum/ Scientific Names Chao Phraya Khlong Phra

Khlong Prapa river Phimon

ArthropodaNauplius (unidentified) 4,600 12,667 100,700Copepod (unidentified) 2,300 2,533 7,600Moina sp. - 1,900Bosmina sp. - 1,900

ProtozoaCentroptxis aculcata 2,300 11,400Cyttarocystis cassis 2,300 -Tintinnopsis sp. - 2,533 -Loucophrys patula - 2,533 -Chilodonella sp. - 2,533Loxodes magnus - 2,533 -Difflugia sp. - 1,900D. acuminata . 9,500Astramocba radiosa 9,500Gaxeletta hexamcma 5,700Euglypha tuberculata 1,900Arcel'a polypoia 1,900

RotiferaKeratella valgn - 10,133 117,800K. cochleariss - 17,733 49,400K. scrulata - 12,667 47,500Filini'a terminata - 2,533 9,500F. brachiata - 2,533 -F. opoliensis - 1,900Ploesoma triacanthum - 2,533Brachionus pala - 2,533 -Br. plicatilis - 9,500Br. faScatus - 11,400Polyarthra sp. - 1,900Pompholyx salcata - 9,500Testudinella sp. - 11,400Albertia typhylina - 5,700Hexamema mira - 3,800

AnnelidaMaupasia sp. - 2,533

MolluscaBivalve larva - 5,067

Unidentified 5,067 -

Total 11,500 88,664 433,200

4 4

Table 8.3: Planktonic Organisms as Indicators of Water Quality (References 8.1 and 8.2)

Water QualityOrganisms High Pollution Load Medium Pollution Load Low Pollution Load

SLaurIUesrrlus sp.Staurastrum sp. /Cyclotella sp. .Dinobryon sp. VMallomonas sp.Oocystis sp. ._ _

Peridinium sp. /Ceratium sp. VTabellaria sp. /

Anabaena sp. /Aphonizomenon sp. /Microcystis sp.Melosira sp. /Fragilaria sp.Synedra sp.Oscillatoria sp. Spirulina sp. _/ _

Table 8.4 Species and Abundances of Benthic Organisms

Abuncdances in indivduaIs/m2Organisms . Chao Phraya Khlong Phra

Khlong Prapa river Phimon

Phylum AnnelidaClass Oligochaeta (Earthworm)Family Naidiae 88Family Tubificidae 220 396

Phylum MolluscaClass GastropodaOrder MesogastropodaFamily AmpullariidaePila sp. 88

- Order NeogastropodaFamily Marginellidae

Rivomarginella sp. 88

Total 308 572

45

Table 8.5: Benthic Organisms as Indicators of Water Quality

Water QualityOrganisms High Pollution Medium Pollution Low Pollution Load

Load Load

Ephemerella sp. (mayfly) _

Nais sp. (worm) /Asellus sp. (bug) /Sialis sp. (alderfly) /

Chironomussp. (midge) /Tubifex sp. (worm) /Limnodrilus sp. (worm) /

CHAPTER 9

ELECTRIC AND MAGNETIC FIELDS

INTRODUCTION

9.1 This section considers the environmental consequences of the electric and magneticfields produced near transmission lines. The effects include possible effects on health,perceptible -effects of high electric fields, such as "microshocks", and effects on implantedheart pacemakers. The effect of power-frequency magnetic fields on certain electronicequipment such as cathode-ray-tube-based visual display units (VDUs) is covered inChapter 1 1.

9.2 The relevant data on possible health effects have been reviewed by a number of nationaland international authorities and their conclusions are also presented.

ASSESSMENT

Field Magnitudes

9.3 The electric field produced by a transmission line depends on the voltage of the line,which remains essentially constant. The magnetic field depends on the current carriedby the line, which varies according to the demand for power at any given time.

9.4 The field strengths at ground level near transmission lines are greatest directly below theconductors and fall as the distance from the line increases. The precise field strengthsat any given point depend on a number of additional factors, including the spatialconfiguration of the conductor array and the arrangement of the three electrical phases.For all the following calculations, it has been assumed that the phasing on the doublecircuit lines is transposed, ie the phase order on one side of the tower is the reverse ofthat on the other. The situation for the quad circuit section is slightly more complicated,and has therefore been illustrated in Figure 9.1.

9.5 EGAT's technical specification states that the electric field strength should not exceed15 kW/m within the Right-of-Way or 2 kV/m at the edge of the Right-of-Way. Magneticfield strengths with load currents of 4 kA per circuit should not exceed 15 pT at the edgeof the Right-of-Way.

Electric Fields9..6 The electric field near ground level beneath a transmission line is strongest where the

conductors are closest to the ground, normally at mid-span. The ground-level fieldstrength diminishes towards the towers, partly because the clearance is normally greaterthere and partly because the towers have a screening effect. The field strength alsogenerally diminishes with lateral distance from the line.

9.7 Objects on the ground such as fences, trees or buildings have a screening effect similarto that of the towers and ground-level field strengths in their neighbourhood are reduced.Most buildings efficiently screen their interiors against external sources of electric fields.

147

9.8 Calculated rms (root-mean square) electric field strengths in kilovolts per metre (kV/m)at one metre above ground level are shown in the Table 9.1. The calculations assumethat the conductors are horizontal at clearances of 13 and 16 metres above ground level,and that the ground is also flat and horizontal.

9.9 In practice, the field strengths are unlikely to reach the maximum values quoted becauseconductor clearances would n-iormaily be greater than 13 metres (the standard clearancewill be 16 metres at mid-span) and because of the screening effect of buildings,vegetation and other objects on the ground.

Magnetic Fields9.10 The ground-level magnetic field of a transmission line is strongest where the conductors

are closest to the ground and its strength diminishes with lateral distance from the lineroute. However, unlike the electric field, the magnetic field is not much screened by thetowers, vegetation or buildings.

9.11 -Calculated rms (root mean square) magnetic field strengths in microtesla (pT) at onemetre above ground for the proposed line designs are shown in Table 9.2. Thecalculations assume that the conductors are horizontal at clearances of 13 and 16 metresabove ground level and that the ground is also flat and horizontal. Loads currents areassumed to be 4 kA per circuit.

9.12 The field strengths would rarely attain these extreme values, because conductorclearances are normally greater than the design minimum and because load currents arenormally less than the 4 kA assumed in the above calculations.

Effects on People

Electric Fields9.13 A person standing in an electric field of about 10 kW/m would have an alternating current

induced in his or her body which could reach approximately 150 pA, about a thousandtimes less than is needed to power a small flashlight bulb and too small to be directlyperceptible (most people cannot perceive currents less than 500 pA). However, theelectric field itself could cause perceptible hair vibration (on the back of an upraised hand,for example).

9.14 In certain circumstances, small spark discharges could pass as the person touched otherobjects, producing a prickling sensation similar to that caused by the static dischargescommonly experienced in dry atmospheric conditions after frictional contact with a nyloncarpet or car seat. Normally, any sensation is confined to the momentary sparkdischarge as contact is made or broken. However, a steady contact with a large structurein poor electrical contact with the ground, such as a lorry or other large vehicle, may allowa perceptible current to pass through the body to ground. This is unlikely to occur unlessthe vehicle has tyres which provide unusually good electrical insulation and it is standingon dry ground. A simple earthing connection between the object and the ground isnormally an effective solution to the problem.

9.15 In the early 1 970s, reports from the Soviet Union claimed that workers in new 500 kV and750 kV substations suffered a number of non-specific health symptoms, which wereascribed to exposure to hiigh electric fields. However, research in the USA, Canada,France, Spain, Sweden and in this counlry on a variety of individuals, including overheadlinesmen, substation workers and members of the public living close to overhead lines,

Z1+89

has failed to substantiate any association between exposure to power-system electricfields and adverse effects on human health.

9.16 A World Health Organisation report (Reference 9.1), concludes: "Whilst it would beprudent in the present state of scientific knowledge not to make unqualified statementsabout the safety of intermittent exposure to electric fields, there is no need to limit accessto regions where the field strength is below about 10 kV/m."

Magnetic Fields9.17 The ground-level magnetic field of a transmission line will normally induce a much smaller

current in a person's body than the current induced by the electric field of the line. In amagnetic field of strength 10 pT, the total induced current could reach approximately 3pA. Unlike the electric field, the magnetic field has no directly perceptible effects on thebody.

9.18 In some circumstances, however, the magnetic field may induce perceptibly largevoltages and currents in long metallic objects (such as pipelines or telephone cables)

-) parallel to the transmission line. This issue is covered in more detail in Chapter 11.

9.19 Recent epidemiological studies, particularly in the United States and in Scandinavia, havesuggested an association between the incidence of childhood cancer and the proximityof homes to power transmission and distribution wires. Power-frequency magnetic fieldshave been postulated as a possible reason for the association. However, no causal linkbetween cancer and magnetic (or electric) fields has been shown and indeed there is noknown way that these fields cou-lu cause o, promote the disease.

9.20 The question of possible health effects of weak power-frequency fields has beenthoroughly reviewed in recent years by bodies such as the World Health Organisation,the International Radiation Protection Association, the UK National RadiologicalProtection Board and the US National Academy of Sciences (References 9.1 to 9.5).None of them has concluded that these fields are a health hazard, although all agree thatmore research is necessary to answer some of the questions that have been raised.

bther Effects

Cardiac Pacemakers9.21 Power-frequency electric and magnetic fields due to transmission power lines constitute

a possible source of interference with the operation of some types of implanted cardiacpacemakers. Most pacemakers are designed to 'fail safe' by reverting to fixed-rateoperation when they sense the presence of interference above a certain level. The fieldstrengths necessary to induce such behaviour vary from one pacemaker model toanother and may, in some circumstances, be encountered in the vicinity of high-voltagetransmission lines.

9.22 The likelihood of patients encountering high-voltage transmission line fields large enoughto affect their pacemaker is small, and there has been no recorded case in Britain of apatient coming to any harm in this way. The UK Department of Health, Medical DevicesDirectorate, does not consider that transmission line electric or magnetic fields constitutea significant hazard.

4

Livestock and Crops9.23 Studies in the USA, Sweden and elsewhere have found little evidence that exposure of

crops, farm animals and natural ecosystems to transmission line electric and magneticfields has any agriculturally significant consequences. One positive finding concerns beehives installed in the highest-field-strength areas beneath transmission lines. Voltagesinduced in the hive structure can cause the bees to experience electric shocks, whichaffect their behaviour and honey production.

MITIGATION

9.24 EGAT agrees that even a remote possibility of a health risk must be taken seriously,because very large numbers of people are exposed to power-frequency fields from bothoverhead and underground power lines and from many other sources, including domesticelectrical appliances. Further studies are in progress worldwide to establish whether or

-- not there is any real cause for concern.

9.25 The problem of the effects on bees caused by voltages induced in the hive structure canbe solved by fitting an earthed screen of chickenwire over the hive. It is thereforeconcluded that eiectric and magnetic fields are unlikely to cause any problems withfarming or related operations in the vicinity of the proposed transmission lines.

CONCLUSIONS '

9.26 Bearing in mind that the standard ground clearance would be 16 metres, the proposed500 kV transmission lines will produce power-frequency electric fields at 1 metre aboveground level under normal operating conditions of significantly less than maximum designvalue of 15 kV/m and less than 2 kV/m at the edge of the Right-of-Way. The shortsection of quad cirouit line may produce electric fields slightly in excess of 2 kV/m (2.16kV/m) at the edge of the Right-of-Way under certain outage conditions.

9.27 These electric field strengths are less than those produced by EGAT's existing 500 kVline design which is already used in the Greater Bangkok Area.

9.28 The maximum power-frequency magnetic-field strength encountered at 1 metre aboveground level will be less than 40 pT within the Right-of-Way and normally less than 15 pTat the edge of the Right-of-Way (remembering that the standard ground clearance wouldbe 16 metres). The one possible exception is during a single circuit outage on theproposed double circuit line, when the level at the edge of the Right-of-Way may reach17.3 pT.

9.29 These magnetic field strengths are less than those produced by EGATs existing 500 kV,'line design which is already used in the Greater Bangkok Area, and the maximum levelsare comparable to those produced by the existing twin-conductored 230 kV lines whichare to be replaced.

9.30 Environmental problems due to electric and magnetic fields are therefore likely to belimited to interference with the image on cathode-ray-tube based VDUs operated closeto the Right-of-Way. This is discussed in Chapter 11.

Table 9.1 : Predicted Electric Field Strengths

Maximum Electric Field atTower Desian Voltage Clearance Electric Edges of Right-of-

in metres Field in Way in kV/mkV/m

double circuit (DCT) both ccts at 13 5.31 1.86 1.86500 kV 16 3.62 1.74 1.74

double circuit (DCT) one cct at 13 6.68 2.00 0.13500 kV, one 16 4.83 1.97 0.25cct earthed

quad circuit (QOCT) four ccts at 13 5.57 2.08 2.085D0 kV 16 3.79 1.93 1.93

quad circuit (QOCT) one side at 13 6.68 2.23 0.15500 kV, one 16 4.84 2.16 0.26side earthed

existing 230 kV line used both ccts at 7.5 4.20 0.15 0.15in Greater Bangkok Area 230 kV

existing 500 kV line used both ccts at 13 6.02 2.76 2.76in Greater roaI n vkok Area __00 kV

Table 9.2: Predicted Magnetic Field Strengths

Maximum Magnetic Field atTower Design Current Clearance Magnetic Edges of Right-of-

in metres Field in Way in pT.__ _ _ _ _ _ pT

double circuit (DCT) both ccts at 13 38.3 13.7 13.74 kA 16 25.7 11.1 11.1

double circuit (DCT) one cct at 4 13 35.6 20.8 11.7kA, one cct 16 25.9 17.3 10.5earthed

quad circuit (QOCT) four ccts at 4 13 39.0 15.7 15.7kA 16 26.5 12.4 12.4

quad circuit (QCT) one side at 4 13 30.6 18.5 9.3kA, one side 16 21.4 14.6 8.0earthed

existing 230 kV line used both ccts at 7.5 40.0 5.2 5.2in Greater Bangkok Area 2 kA

existing 500 kV line used both ccts at 13 45.6 19.5 19.5in Greater Bangkok Area 4 kA

51

Figure 9.1: Assumed Phasing for Proposed Quad Circuit 500 kV Line Design

AC

BB

CA

A

BB

A

X ~~~~~C

CHAPTER 10

AUDIBLE NOISE

INTRODUCTION

10.1 An energised transmission line can be a source of a phenomenon known as "coronadischarge" (a limited electrical breakdown of the air) which can also occur naturally duringstorms when highly charged clouds induce high electric fields around tall objects such asships' masts or projections from buildings. Such corona discharge is sometimes seenat night and has been called "St. Elmo's Fire".

10.2 While power transmission line conductors are designed and constructed to minimisecorona, surface irregularities caused by damage, insects, raindrops or other forms of

- - contamination may locally enhance the electric field strength sufficiently for dischargesto occur. Any corona discharge will act as a source of audible noise (a crackling soundoccasionally accompanied by low frequency hum).

10.3 Methods for predicting the noise level generated by a new transmission line design havebeen developed, and hence the environmental acceptability of the proposed line designcan be assessed. The results of this assessment therefore form part of the informationused during the line design process.

ASSESSMENT

Qeneral

10.4 Transmission line noise is generated when the conductor surface electric stress exceedsthe inception level for corona discharge activity. Transmission line conductors aredesigned to operate below this threshold. Surface contamination on a conductor will,however, cause a local enhancement of electric stress and possibly initiate dischargeactivity. At each discharge site, a limited electrical breakdown of the air occurs. Aportion of the energy associated with the corona process is released as acoustic energyand radiates into the air as sound pressure waves.

10.5 Transmission line audible noise is generally categorised as "crackle" or "hum", accordingto its tonal content. 'Crackle" is a sound containing a random mixture of frequencies overa wide range, typically 1 to 10 kHz. No individual pure tone can be identified for anysignificant duration. 'Crackle' has a generally similar spectral content to the sound ofrainfall. "Hum" is a sound consisting of a single pure tone. Generally 100 Hz is mostsignificant, but other harmonics of the power frequency may occur to a lesser extent.

10.6 The highest noise levels generated by a line generally occur during rain. Water dropletscollect on the surface of the conductor and may initiate corona discharges. The numberof droplets, and hence the noise level, will depend primarily on the rate of rainfall.

10.7 Alternatively, after a prolonged spell of dry weather without rain to wash the conductors,contamination may accumulate sufficiently to result in increased noise. During the nextheavy rain storm, the discharge sources are removed and the line reverts to being quiet.

10.8 It should be noted that when the line is first energised, noise levels in excess of thosepredicted below are possible. A decrease to the long-term noise levels will occur duringan initial ageing-in period, the length of which depends on prevailing meteorologicalconditions and local levels of air pollution. However, this progressive ageing-in processshould be well advanced after a period of 12 months.

Foul WeatherAudible Noisp Prediction

10.9 A method developed by the Bonneville Power Administration (BPA) is used to predict theL,0 audible noise level in a foul weather at a given distance from the proposed linedesigns (Reference 10.1). This method uses the average maximum surface electricstress for each subconductor bundle as input data, along with the number ofsubconductors in each bundle, the diameter of the subconductors and the distance to theobserver. The distance to the observer has been taken as the distance to the edge ofthe Right-of-Way, ie 20 metres.

10.10 The calculations have assumed a minimum ground clearance of 13 metres, although itwill usually be 16 metres or greater. This is therefore a worst-case. The phasingassumed was as described in Chapter 9, ie fully-transposed, in order to minimise theground level electric and magnetic fields.

10.11 Using the BPA method to calculate the Ls -in foui weather for the proposed double circuitline design with both circuits operating at 500 kV gives an answer of 43 dB(A). For thequad circuit line design with all circuits operating at 500 kV, the predicted L. in foulweather is also 43 dB(A). This is due to a combination of factors, including stressreduction on the bundles on the middle two cross-arms and the fact that the uppercircuits are further from the ground, cancelling out the increase in noise due to a doublingof the number of potential noise sources.

10.12 When the quad circuit line is built initially, there will be just two 500 kV circuits on the topcross-arms. The bottom cross-arms will remain unstrung until there is a need for furthercapacity. The audible noise performance of this configuration has therefore beenconsidered; the predicted L. in foul weather is 40 dB(A).

Comparison with Existing Line Designs

10.13 The existing line between Bangkok Noi and Sai Nol (which is to be replaced by the doublecircuit 500 kV line) operates at 230 kV and uses a single ACSR 42/7 1272 MCMconductor per bundle. Using the above technique to predict the Lso in foul weather at theedge of the Right-of-Way gives an answer of 42 dB(A).

10.14 Other existing 230 kV lines in the Bangkok area (which are also to be replaced by thedouble circuit 500 kV line) use twin ACSR 42/7 1272 MCM conductors. These thereforehave a better audible noise performance in foul weather; the L., predicted according tothe same technique is 27 dB(A).

10.15 Because the decibel scale is logarithmic, a casual listener would not be able todistinguish between a noise at 42 dB(A) and the same noise at 43 dB(A). This meansthat the noise performance of the proposed line designs can be considered to be identicalto that of the existing 230 kV line between Bangkok Noi and Sai Noi. Neither of these linedesigns have been the subject of complaints about audible noise.

z5

Foul Weather Audible Noise Assessment

10.16 For audible noise, the Electricity Generating Authority of Thailand (EGAT) required thatthe LR, in foul weather should nct exceed 55 dB(A) at the edge of the Right-of-Way. Boththe proposed line designs have a predicted L., in foul weather of 43 dB(A) when fullyoperational at 500 kV. This is well within the audible noise limit proposed by EGAT.

10.17 The proposed line designs have a predicted noise performance which is practicallyidentical to that of the existing 230 kV line between Bangkok Noi and Sai Noi. This hasnot been the subject of complaints about audible noise, and therefore it is unlikely thatthe new line designs will provoke complaints about audible noise.

MITIGATION

10.18 The proposed lines have been designed such that the predicted foul weather audible- noise levels are well within those required by EGAT and comparable to the noise levelsgenerated by existing, acceptable line designs of a lower voltage. Therefore, no furthermitigation is proposed.

CONCLUSION

10.19 The predicted audible noise performance of the proposed line designs in foul weather iswell within the level required by EGAT and comparable with that of existing, acceptableline designs of a lower voltage. Therefore, both the double circuit and the quad circuitline designs are environmentally acceptable from an audible noise point of view.

/55

CHAPTER 11

ELECTRO-MAGNETIC COMPATIBILITY

INTRODUCTION

11.1 Few complaints about electro-magnetic compatibility (EMC) arise from the normaloperation of overhead lines. Those that do are often caused by unsuitable or faultyequipment or its installation.

11.2 There have been no reported incidents of interference from overhead lines affectingprivate radio transmissions or the emergency services. The main concems relate to TVinterference (as raised during the socio-economic survey in Chapter 4) and a screeninterference phenomenon known commonly as 'VDU wobble".

- ASSESSMENT

Corona Discharge

11.3 Whether wet or dry, corona discharge from high voltage equipment will affect televisionor radio reception will depend on the signal strength (S) of the required broadcast, andupon the strength of the corona interference 'noise' (N) at the same frequency andbandwidth. If a suitably high signal-to-noise (S/N) ratio can be maintained within thetransmitter service area then no interference will be experienced.

11.4 A revised international standard for the limit