Upgrade of the Tabor Substation and the deviation of the Tabor Louis Trichardt 132kV power line.

Transcription

1 BIRD IMPACT ASSESSMENT PROFESSIONAL OPINION Upgrade of the Tabor Substation and the deviation of the Tabor Louis Trichardt 132kV power line. Compiled by: Chris van Rooyen Consulting 30 Roosevelt Street Robindale Randburg 2194 South Africa Tel. International: Tel. Local: Fax:

2 1. INTRODUCTION & BACKGROUND The project description below was taken directly from the Draft Scoping Report (Zitholele 2010). The proposed project is for the upgrade of the existing 275/132kVTabor Transmission Substation to accommodate the new 400kV and 132kV power lines and the deviation of the existing 132kV Tabor Louis Trichardt power line near Polokwane in the Limpopo Province. The proposed footprint for the substation extension is approximately 300 x 300 metres. Additionally the servitude required for a 132kV power line is 36 metres (18 metres on either side) and it is estimated to be a length of between 500 metres and two kilometres (depending on the approved alternative). Therefore the total construction area required is dependent on the approved alternative. Construction activities will be limited to the footprint of the extension of the substation and the approved power line corridor. The construction phase for the project will take approximately 18 months and will include the construction for the extension of the substation and the deviation of the 132kV Tabor-Louis Trichardt power line. The civil construction works i.e. platforming, storm water control and foundations is likely to take place first, with the balance of time taken up with the fabrication and erection of steelwork. The construction phase will entail the following: Removal of vegetation within the substation footprint and power line servitude; Dismantling of 132kv Tabor Louis Trichardt pylons / towers within the substation extension footprint; Relocation of 132 kv Tabor-Louis Trichardt pylons / towers to newly approved servitude; Stringing of the deviated 132kV Tabor-Louis Trichardt power line; Terracing and levelling of the site; Installation of foundations for infrastructure such as transformers, control building and radio tower; Construction of bunds and fire safety walls; Compaction and filling with gravel of the areas between foundations; Creation of formal drainage and storm water control measures; Delivery and installation of transformers, towers, busbars and associated infrastructure; Construction of control rooms and administrative infrastructure; Construction of the perimeter fence and lighting. The first construction activity will be to clear the site of vegetation and to level off and terrace the ground surface for those areas where the heavy electrical transformers and other switchgear will stand. After this will follow the concrete and building construction for foundations for the supporting steelwork, transformers and other switchgear, storm water drainage pipes, slabs, bund walls, the control room, small buildings and storage areas that are needed. All open areas between the transformer plinths and other switchgear foundations will be covered with about a 150 mm layer of 25 mm crushed stone. Before laying the crushed stone, the ground surface is intensively treated to strict specification with insecticide and herbicide to prevent insect activity and the growth of weeds and other plants in the high voltage yard. The steelwork will then be erected. The transformers, circuit breakers, reactors and other high voltage equipment will be delivered to site, erected and then commissioned. Eskom has decades of experience in the construction and operational use of high voltage equipment such as the proposed extension of the Tabor Substation. All equipment, commissioning and operational procedures and protocols are subject to strict specifications, which Eskom has had in place for many years. Construction is anticipated to begin in March 2011, and it is estimated that it will continue for approximately eighteen months thereafter, before the substation is finally commissioned. The substation is planned to be commissioned at the latest March During construction, which is when the civil works are being carried out (foundations, storm water drainage, buildings, etc), there should not be more than 50 people present on the site at any one time. Depending on the level and

3 nature of construction activity taking place, there will be varying numbers of people housed on site in temporary accommodation. No one will be housed on site on a permanent basis during the operational life of the substation. However, there will be ongoing monitoring and control of operations as well as planned and other maintenance work done on an ad hoc basis. During operations, Eskom requires access to the substation for maintenance activities. Maintenance activities are specialised and are, therefore, carried out by Eskom employees. Figure 1 below shows the extent and location of the alternatives for the proposed infrastructure. Figure 1: Proposed alternatives for the extension to the Tabor substation and the proposed deviations of the Tabor Louis Trichardt 132kV sub-transmission line.

4 1.1 Terms of reference The terms of reference for the avifaunal professional are as follows: Review existing avifaunal reports for the study area and determine the occurrence of any Red Data and vulnerable species; Provide mitigation measures to prevent and/or mitigate any environmental impacts that may occur due to the proposed project; Compile an avifaunal professional opinion memorandum, indicating findings, recommendations and maps indicating sensitive and/or no-go areas. 1.2 Sources of information The following information sources were consulted in order to conduct this desktop study: Bird distribution data of the Southern African Bird Atlas Project 1 (SABAP1 Harrison et al 1997) was obtained from previous avifaunal studies conducted in the area. The more recent bird distribution data (2007 onwards) of the Southern African Bird Atlas Project 2 (SABAP2 sabap2.adu.org.za) for 2329BD was also checked for a more up to date snapshot of the species that have been recorded. The Draft Scoping Report (April 2010) compiled by Zitholele Consulting was used to obtain details of the project scope and design. Additional information on bird occurrence and potential impacts were obtained from the bird impact assessment study compiled by the Endangered Wildlife Trust for the Tabor Witkop 400kV transmission line in Assumptions & Limitations This desktop report made the assumption that the above sources of information are reliable. The following factors may potentially detract from the accuracy of the predicted results: The SABAP data covers the period Bird distribution patterns fluctuate continuously according to availability of food and nesting substrate. Sources of error in both the SABAP1 and SABAP2 databases, particularly inadequate coverage of some quarter degree squares. This means that the reporting rates of some species may not be an accurate reflection of the true densities in quarter degree squares that were sparsely covered during the data collecting period. It must be noted that in this instance the 2329BD quarter degree square has not been very extensively covered by any of the SABAP projects, which means that the reporting rates may not be an accurate reflection of actual densities on the ground. Only 39 checklists were completed for SABAP1 and only 4 checklists for SABAP2. 2 DESCRIPTION OF AFFECTED ENVIRONMENT Woodland (or savanna) is the dominant vegetation type in the study area and it is defined as having a grassy under-storey and a distinct woody upper-storey of trees and tall shrubs (Harrison et al 1997). The woodland biome contains a large variety of bird species (it is the most species-rich community in southern Africa) but very few bird species are restricted to this biome. It is also relatively well conserved compared to the grassland biome. The woodland biome is particularly rich in large raptors, and forms the stronghold of Red Data species such as White-backed Vulture Gyps africanus, Cape Vulture Gyps coprotheres, Martial Eagle Polemaetus bellicosus, Tawny Eagle Aquila rapax, and Lappet-faced Vulture Torgos tracheliotis. Apart from Red Data species, it also serves as the stronghold of several non-red Data raptor species, such as the Brown Snake Eagle Circaetus cinereus, Black-chested Snake Eagle Circaetus pectoralis, and a multitude of medium-sized raptors

5 for example the migratory Steppe Buzzard Buteo vulpinus, African Harrier Hawk (Gymnogene) Polyboroides typus, Wahlberg s Eagle Aquila wahlbergi and African Hawk Eagle Aquila spilogaster. Apart from raptors, woodland in its undisturbed state is suitable for a wide range of other power line sensitive birds, including the Kori Bustard Ardeotis kori. The woodland in the study area has been impacted in places, with many dirt roads and tracks crisscrossing the study area. Agriculture has led to areas having been cleared of trees and the grassy under-story is depleted due to heavy grazing by cattle. Large terrestrial species such as Kori Bustard and Southern Ground Hornbill Bucorvus leadbeateri that historically almost certainly occurred here is long gone. It is however feasible that most of the Red Data power line raptor species are still to be found, albeit in reduced numbers, as their prey base is most likely also under pressure due to the effects of habitat transformation, and disturbance of breeding activity by vehicle and pedestrian traffic (see Table 1 below). Table 1: Red Data species that have been recorded in 2329BD (Harrison et al 1997; Species SABAP1 reporting rate (%) SABAP2 reporting rate (%) African Marsh-harrier Circus ranivorus 3 - Bateleur Terathopius ecaudatus 3 - Martial Eagle Polemaetus bellicosus 3 - White-backed Vulture Gyps africanus 31 - Cape Vulture Gyps coprotheres 10 - Red-billed Oxpecker Buphagus erythrorhynchus 21 - Short-clawed Lark Certhilauda chuana 3 - Lanner Falcon Falco biarmicus 3 - Secretarybird Sagittarius serpentarius 38 - Black Stork Ciconia nigra ASSESSMENT OF POTENTIAL INTERACTIONS Because of their size and prominence, electrical infrastructures constitute an important interface between wildlife and people. Negative interactions between wildlife and electricity structures take many forms, but two common problems in southern Africa are the electrocution of birds (and other animals) and birds colliding with power lines. Other problems are: electrical faults caused by bird excreta when roosting or breeding on electricity infrastructure; and disturbance and habitat destruction during the construction and maintenance activities associated with electrical infrastructure.

6 3.1 Loss of breeding, foraging and roosting habitat through habitat transformation. During the construction phase and maintenance of power lines and substations, some habitat destruction and alteration inevitably takes place. This happens with the construction of access roads, and the clearing of servitudes. These activities have an impact on birds breeding, foraging and roosting in or in close proximity of the site, through the modification of habitat. Historically (i.e. before the establishment of the current infrastructure) the area surrounding the proposed power line and substation comprised entirely of undisturbed woodland. As a result it may have supported a number of power line sensitive species, particularly raptor species currently Red listed such as Martial Eagle, Tawny Eagle, Bateleur, Lappet-faced Vulture Torgos tracheliotis and also non-raptors such as Southern Ground Hornbill Bucorvus leadbeateri and Kori Bustard Ardeotis kori. However this area has long been transformed to accommodate a change in land use (i.e. livestock and industrial infrastructure) which reduced the number and variety of species originally inhabiting the area, on account of the loss of habitat and decline in food availability. It is therefore unlikely that any of the remaining Red Data species will regularly utilize the area, in view of impact of the current human population, although visits to the area can still happen. The impact on smaller, non-red Data species that are potentially breeding in the area that will be taken up by the extended Tabor substation and clearing of woodland for the proposed 132kV deviation will be local in extent, in that it will not affect regional or national populations in any significant way. It is also likely that the clearing of dense shrub and bush below the proposed new 132kV line will create new foraging habitat for raptors which is currently inaccessible due to the dense vegetation. The proposed construction of the new substation and associated power lines would therefore have a LOW habitat transformation impact from an avifaunal perspective. 3.3 Collisions with the proposed power line. With the exception of the Short-clawed Lark and the Red-billed Oxpecker, all the species listed in Table 1 are potentially vulnerable to collisions with power lines. However, the only species that is likely to be potentially specifically attracted to the study area for foraging purposes is the Black Stork, due to the presence of three dams, two of which are situated within the zone of influence of the current Tabor Louis Trichardt 132kV line (see Figure 1). The current alignment of the line is highly risky, running straight over one of the dams. Large raptors are also potentially attracted to open water bodies, as they use them to bath and drink water. This could expose them to an occasional risk of collision. Compared to the existing Tabor Louis Trichardt 132kV line, the realignment will be a huge improvement as far as collision risk is concerned, especially if Alternative 1 is used. The risk of collision is therefore regarded as LOW. 3.4 Electrocutions on the proposed 132kV power line. The electrocution risk is a function of the size of the bird and the tower design. Self-supporting tower design is the one that is considered to be suitable for the proposed deviation of the 132kV Tabor-Louis Trichardt power line. This was supported by the technical requirements of the proposed deviation as well as considering the needs of the land owners whereby this tower design does not require big portion of land. Furthermore, the existing Tabor-Louis Trichardt power line design is a self-supporting suspension tower and therefore Eskom would like to keep uniformity of tower designs within that specific project. The risk of electrocution on self-supporting towers is extremely LOW, as the birds generally perch above the insulators, away from the potentially dangerous live conductors. 4. CONCLUSIONS & RECOMMENDATIONS The proposed project is for the upgrade of the existing 275/132kVTabor Transmission Substation to accommodate the new 400kV and 132kV power lines and the deviation of the existing 132kV Tabor Louis Trichardt power line near Polokwane in the Limpopo Province. The overall impact of the proposed project is regarded as LOW. No specific recommendations are deemed necessary to mitigate for impacts in this regard, other than strict adherence to Eskom s vegetation clearing guidelines, to minimize the impact on vegetation. The preferred alignment from a bird impact

7 perspective would be Alternative 1, as it would largely remove the collision risk posed by the current alignment of the Tabor Louis Trichardt 132kV line. The fact that Alternative 1 will have the largest footprint due to it being the longest alternative is not of material importance from a potential bird interaction perspective, as the vegetation clearing should not affect any power line sensitive Red Data species in any significant way. If alternative 2 or 3 is utilised, consideration should be given to the marking of the existing 132kV with Bird Flight Diverters on the earth wire, where it crosses the dam (see Figure 2 below). Section of the existing Tabor-Louis Trichardt 132kV line that should be marked with BFDs. Figure 2: The section of the existing Tabor-Louis Trichardt 132kV line that should be marked with Bird Flight Diverters.

8 5. REFERENCES BARNES, K.N. (ed.) The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. BirdLife South Africa, Johannesburg. HARRISON, J.A., ALLAN, D.G., UNDERHILL, L.G., HERREMANS, M., TREE, A.J., PARKER, V & BROWN, C.J. (eds) The atlas of southern African birds. Vol 1 & 2. BirdLife South Africa, Johannesburg. SOUTHERN AFRICAN BIRD ATLAS PROJECT 2. http.sabap2.adu.org.za. Accessed 19 June SMALLIE, J Tabor Witkop 400kV Power Line. Eskom Transmission. Bird Impact Assessment Study. Endangered Wildlife Trust, Johannesburg. ZITHOLELE CONSULTING The upgrade of the Tabor Substation and the deviation of the Tabor Louis Trichardt 132 kv power line. Draft Scoping Report. DEA REF NO: 12/12/20/1776