Environmental impact before mitigationenvironmental impact after mitigationemp requirements
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| Annexure B
ISSUEDESCRIPTIONENVIRONMENTAL IMPACT BEFORE MITIGATIONENVIRONMENTAL IMPACT AFTER MITIGATIONEMP REQUIREMENTSBird collisions with the earthwire of the proposed line The issue is the negative biological impact of bird mortality caused by birds, especially threatened species, colliding with the earthwire of the proposed line Overall significance rating = Moderate Section 1: Overall significance rating = Moderate Confidence level = high Section 2: Overall significance rating = Low to Moderate. Preferred alternative = southern route Confidence level = high Section 3: Overall significance rating = low Confidence level = low Section 4: Overall significance rating = moderate Confidence level = low Section 5: Overall significance rating = moderate Confidence level = low
Up to 1996, it was generally believed that powerline collisions are not a major problem in Southern Africa, with the exception of the three crane species and flamingos. This may have been the case because collisions with powerlines are seldom recorded through internal systems, as it seldom impacts on the electricity supply. However, a disturbing new picture has since started to emerge from data gathered over the past six years, pointing to the fact that collisions are indeed a major cause of unnatural mortality for several threatened birds (Anderson 2001). Most heavily impacted upon are bustards, storks, cranes and various species of waterbirds. These species are mostly heavy-bodied birds with limited manoeuvrability, which make it very difficult for them to take the necessary evasive action to avoid colliding with powerlines. Impact assessment was essentially limited to estimating the risk of collision with the line by threatened (SA Red Data species – Barnes 2000, or Globally threatened – Stattersfield 2000) or endemic/near-endemic, large terrestrial bird species or raptors, known to be prone to such collisions. This was done by identifying landscape features likely to attract such species, or to channel commuting birds, into the vicinity of the line. The study was compromised by constraints on time and funding. Two approaches were used – impacts of the proposed routes through the Karoo from Victoria West to Karoo Poort (sections 3-5) were estimated using large-scale maps and knowledge and experience of the area of the field biologists. Routes through the more complex, populated, agricultural areas from Karoo Poort to Olifantskop (sections 1 and 2) were followed (as far as possible) on the ground using the existing road network. Ideally, all proposed and alternative routes should have been followed by helicopter. Priority bird species: White Pelican Pelecanus onocrotalus (SA Near-threatened), Greater Flamingo Phoenicopterus ruber (SA Near-threatened), Lesser Flamingo Phoeniconaias minor (SA Near-threatened), Secretarybird Sagittarius serpentarius (SA Near-threatened), Blue Crane Anthropoides paradiseus (SA Vulnerable, near-endemic), Kori Bustard Ardeotis kori (SA Vulnerable), Ludwig’s Bustard Neotis ludwigii (SA Vulnerable). Other species of concern: White Stork Ciconia ciconia (Global ), Black Stork C. nigra (SA Near-threatened), Martial Eagle Polemaetus bellicosus (SA Vulnerable), Peregrine Falcon Falco peregrinus (SA Near-threatened), Lanner Falcon F. biarmicus (SA Near-threatened), Karoo Korhaan Eupodotis vigorsii (near-endemic). Key landscape features are saddles, necks or valleys, waterbodies close to the route, waterbody complexes spanning the route, river-crossings, drainage lines, isolated areas of agriculture, cliff-lines. Sensitive areas along the recommended route of the line are marked and numbered on the accompanying map (annexure A) of the proposed routes. Details of the perceived threat or problem posed by each highlighted location are provided separately in table format with particulars of each locality and recommended mitigation (annexure B). Bird Atlas data and Coordinated Avifaunal Roadcount data (sourced from the Avian Demography Unit, UCT) were used to determine areas of the route where impacts could occur. Section 1: The line poses a collision threat to White Pelican, White Storks, Greater and Lesser Flamingo, Secretarybird and Blue Crane where it passes through cereal croplands and/or close to sizable waterbodies Section 2: The line poses a threat to cliff-nesting raptors (and Black Storks?) where it passes through mountainous areas (Riebeek-Kasteel – Tulbagh – Ceres – Karoo Poort), and to waterfowl near farm dams and wetlands. Section 3: The line poses a threat waterbirds where it crosses close to waterbodies. Other powerline sensitive species are present but in low numbers. Section 4: The line poses a threat mainly to bustards in flat areas between hilly country, and to waterbirds near farm dams and river crossings. Section 5: The line poses a threat to bustards in low lying areas, cranes near waterbodies, storks near low lying, agricultural and wetland areas, and cliff-nesting birds and waterfowl Overall significance rating = Low Section 1: Overall significance rating = low Confidence level = high Section 2: Overall significance rating = Low Preferred alternative = southern alternative Second most preferred alternative = final route Third most preferred alternative = central alternative Least preferred alternative = northern alternative Confidence level = high Section 3: Overall significance rating = low Confidence level = low Section 4: Overall significance rating = low Confidence level = low Section 5: Overall significance rating = low Confidence level = low
Bird anti-collision devices of different kinds have been used worldwide for several decades to limit bird collision mortality. Up until 1997, the most frequently used device was the so-called Bird Flight Diverter (BFD), which is basically a PVC spiral shaped as a pigtail. Several sizes are available. The advantage of the BFD is that it has no moving parts which mean that it requires no maintenance is durable. The disadvantage of the BFD is that it has been found to be ineffective in curbing large terrestrial bird mortality on transmission lines in the Karoo (Anderson 2001). A more recent device is the Bird Flapper (BF) that has been locally developed. The advantage of the BF is that it has been proven to be statistically significantly better in reducing bird mortality than the BFD (Anderson 2001). On 400 kV lines, 30% reduction in mortality was reported, while reductions of up to 80% have been recorded on smaller lines. The disadvantages of the BF are that it has been plagued by mechanical failure, although recent field tests are producing better results (Van Rooyen unp.data). A particular problem that has to be dealt with is the issue of nocturnal collisions. In this respect, the flamingo species are particularly vulnerable due to their habit of migrating long distances at night. A device is available to address this issue, namely a product called a Mace Bird Lite, produced by Mace Technologies. It basically consists of a Perspex tube with a fluorescent tube inside. The tube is placed on the earthwire and energised using the ambient electrical field generated by the conductors. This has been designed specifically with 132kV towers in mind, but it should be possible to design a similar device for use on the proposed line. Research into an effective anti- collision mitigation device for large transmission lines continues, and it may well be that new devices are available when construction of the line is started. √
Marking sections of line skirting waterbodies and agricultural habitat in sections 3 – 5 in addition to areas already earmarked for mitigation. Directory: OurCompany -> SustainableDevelopment -> EnvironmentalImpactAssessments EnvironmentalImpactAssessments -> Environmental impact assessment open cycle gas turbine power plant in mossel bay: additional units final scoping report Download 14.08 Kb. Share with your friends:
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