2. TECHNICAL DETAILS OF THE PROPOSED PROJECT ... - Eskom

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Environmental Impact Assessment for the proposed construction of a 400 kV Transmission power line between Mercury Substation and Ferrum Substation traversing the Free State, North West and Northern Cape Provinces Inaccessible Item Standard Follow up valleys (trace line) Access/service roads Proposed tower position and proposed support/stay wire position Indigenous vegetation within servitude area (outside of maximum 8 m strip) Alien species within servitude area (outside of maximum 8 m strip) Clear a 1 m strip for access by foot only, for the pulling of a pilot wire by hand. Clear a maximum (depending on tower type) 6 m wide strip for vehicle access within the maximum 8 m width, including de-stumping/cutting stumps to ground level, treating with a herbicide and re- compaction of soil. Clear all vegetation within proposed tower position in an area of 20 m x 20 m (self- supporting towers) and 40 m x 40 m (compact cross-rope suspension towers) around the position, including de- stumping/cutting stumps to ground level, treating with a herbicide and re- compaction of soil. Allow controlled agricultural practices, where feasible. Area outside of the maximum 8 m strip and within the servitude area, selective trimming or cutting down of those identified plants posing a threat to the integrity of the proposed sub-transmission power line. Area outside of the maximum 8 m strip and within the servitude area, remove all vegetation within servitude area and treat with appropriate herbicide. Vegetation not to be disturbed after initial clearing – vegetation to be allowed to re-grow. Re-growth to be cut at ground level and treated with herbicide as necessary. Re-growth to be cut at ground level and treated with herbicide as necessary. Selective trimming Cut and treat with appropriate herbicide. Once the centre line has been cleared, the contractor’s surveyor will peg every tower position and marks the crossing point with existing fences for new gate installations. Where required, once the tower positions have been marked, the vegetation clearing team will return to every tower position and clear vegetation, in accordance with the specifications outlined in the draft Environmental Management Plan (EMP) attached in Appendix A, as well as associated Eskom vegetation management guidelines to be adhered to during construction activities (Refer to Appendix B). 2.2.3 Foundations The choice of foundation is influenced by the type of terrain encountered, as well as the underlying geotechnical conditions. The actual size and type of foundation to be installed will depend on the soil bearing capacity (actual sub-soil Technical Details 2-6 16/04/2007
Environmental Impact Assessment for the proposed construction of a 400 kV Transmission power line between Mercury Substation and Ferrum Substation traversing the Free State, North West and Northern Cape Provinces conditions). Strain structures require more extensive foundations for support than in-line suspension structures, which contributes to the cost of the construction of the power line. The footprint area required for the construction of the foundation for the powerline is 1,5 m x 1,5 m. The minimum working area required around a structure position is 20 m × 20 m for self-supporting towers and 40 m x 40 m for compact cross-rope suspension towers. Foundations may be mechanically excavated where access to the tower position is readily available. The same usually applies to the pouring of concrete required for the setting of the foundations. Prior to erecting the towers and filling of the foundations, the excavated foundations are protected in order to safe-guard unsuspecting animals and people from injury. All foundations are back-filled, stabilised through compaction, and capped with concrete at ground level. Construction activities associated with foundations are represented in Figures 2.7 and 2.8 below. Figure 2.7: Tower foundation construction Technical Details 2-7 16/04/2007
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2. TECHNICAL DETAILS OF THE PROPOSED PROJECT ... - Eskom

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