Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

PROPOSED 765 kV TRANSMISSION LINE

GAMMA TO OMEGA

PEDOLOGY REPORT

Prepared by

Kayode Okesanjo

Kay Environmental Services

P.O. Box 1533

Paulshof 2056

Prepared for:

PBA International

February 2002

EXECUTIVE SUMMARY

Kay Environmental Services (KES) was approached by PBA to undertake pedological study of the proposed Gamma – Omega 765 kV transmission line. The proposed 765 kV Transmission line forms a part of the wider Cape Strengthening Programme being undertake by Eskom’s Transmission. The motivation for the programme is set out in the report, however it sets out to address two key requirements:

  • To strengthen the transmission networks to the Western Cape such that reliability of the supply is improved.
  • To enhance the capacity of the network such that predicted future demand may be met.

To comply with regulatory requirements of the Environmental Conservation Act (Act 73 of 1989 and associated regulations), and to apply internationally acknowledged best management practice in its activities, Eskom Transmission Group have undertaken this Environmental Impact Assessment (EIA) process.

The aim of this study is:

  • To improve the reliability of the exiting transmission network to the Western Cape, and
  • To upgrade the electricity transmission capacity of the network in the short-term whilst providing for the longer-term requirement.

This report is primarily comprised of a desktop study of the corridor supplemented by site visits and feedback from I&APs. The primary sources of information were the Institute of Soil, Water and Climate maps and land-type memoirs, and Eskom.

The environmental impacts of the construction phase would be particularly sensitive to the management and sensible planning. These impacts include soil erosion and soil pollution.

The issues and activities connected to the construction phase include:

  • Clearing of vegetation for the installation of the transmission towers.
  • Clearing of areas for campsites.
  • Construction of access roads.
  • Soil erosion.

The soil types along the entire route are generally stable, though all are sensitive to disturbance. The areas in section 2 are very sensitive and due to the position of the soil on the steep slopes along the mountain range. Evidence of gully, water and wind erosion is present in the landscape. In sections 3 to 5 there is evidence of erosion throughout the area, primarily due to infrastructure such as road crossings of watercourses.

Construction activities should be carefully monitored to ensure compliance with the EMP. The EMP should limit construction activities to those that are acceptable in preventing environmental damage. No scarring of such areas would be allowed and proper rehabilitation would ensure recovery without any problems. Erosion prevention measures should be taken right from inception of the construction process.

The proposed transmission line will have very little impact on the soil within the study corridor. However there are some sensitive areas within the study corridor especially the areas within section 2 were the terrain shows extensive evidence of gully and sheet erosion. Special attention needs to be giving to this area during the construction of the proposed transmission line.

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

TABLES OF CONTENTSPage

1.INTRODUCTION

2.BACKGROUND AND BRIEF

3STUDY APPROACH

4STUDY AREA

4.1SOILS

5.IDENTIFICATION OF RISK SOURCES

5.1CONSTRUCTION

5.2MAINTENACE DURING OPERATION

5.3CRITERIA AGAINST WHICH EXPECTED IMPACTS ARE EVALUATED

6.IMPACT DESCRIPTION AND ASSESSMENT

7GENERIC MANAGEMENT AND MITIGATION MEASURES

7.1MITIGATION

7.2MAINTENANCE

7.3REHABILITATION OF FERTILE SOIL

8ALTERNATIVES

9CONCLUSION

10.REFERENCES

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

1.Introduction

The proposed 765 kV Transmission line forms a part of the wider Cape Strengthening Programme being undertake by Eskom’s Transmission. To comply with regulatory requirements of the Environmental Conservation Act (Act 73 of 1989 and associated regulations), and to apply internationally acknowledged best management practice in its activities, Eskom Transmission Group have undertaken this Environmental Impact Assessment (EIA) process.

Although the new transmission line will only be brought into operation at the time when growth and demand requires it, it is necessary to secure the corridor (servitude) that will accommodate the proposed 765 kV well in advance. The study route is a 10km corridor centred on a preferred alignment for the new transmission line. The length of the study corridor is some 520km. It may cross the Western/Northern Cape provincial border at a number of locations, but the bulk of the route lies in the Western Cape province.

2.Background and brief

The Cape Strengthening Programme comprises a number of individual projects with the collective aim of improving the reliability of electricity supply to the southern areas of the country, and to the Western Cape in particular.

The primary aims of the Cape Strengthening Programme are:

  • To improve the reliability of the exiting transmission network to the Western Cape, and
  • To upgrade the electricity transmission capacity of the network in the short-term whilst providing for the longer-term requirement.

3STUDY APPROACH

This report is primarily comprised of a desktop study supplemented by site visits and feedback from I&APs. The primary sources of information are the Institute of Soil, Water and Climate (ISWC) and Soil map produce from the Environmental Impact Assessment software package.

The approach to this study was to review all soil land-type maps, from ISWC and topographical information from 1: 50,000 maps. No soil mapping was conducted but site visits were undertaken at locations along the route.. The erosion hazard criteria consists of two sub-criteria, namely slope gradient and soil erodibility group. Both criteria need to be met for the land to qualify for a particular erodibility class.

4STUDY AREA

The study route is a 20km corridor centred on a preferred alignment for the new transmission line. The length of the study corridor is some 520km. It may cross the Western/Northern Cape provincial border at a number of locations, but the bulk of the route lies in the Western Cape province. The pedology for the route was reviewed. Critical and/or sensitive areas along the corridor were identified and mitigation factors area discussed. Refer to Map 5a – Soils.

4.1SOILS

Section 1 soils are dominate by soils with a marked clay accumulation also common within this section is soils with minimal development (lime present) and greyish-sandy excessively drained soil, with some soils with minimal development with lime rare in the landscape.

Section 2 of the study corridor is dominate by soils with minimal development with lime present and soils with minimal development with lime rare in the landscape, also common is the landscape is rocks with limited soils and soils with marked clay accumulation strong and reddish colour.

Section 3 soils are dominated by soils with marked clay accumulation strong and reddish with Red-massive or weak structured soils with high base status and rock with limited soils.

Section 4 soils include both soils with minimal development (shallow on hard or weathering rock) with lime present and rocks with limited soils.

Section 5 soils are dominated by soils with minimal development (shallow on hard or weathering rock) with lime present, also present are rocks with limited soil, Red massive or weak structured with high base status. Present in limited parts greyish-sandy excessively drained soils and soils with negligible to weak profile development –usually on recent flood plains.

Erosion is seen to be a potential problem for the whole study area. The flatter terrain and extensive agricultural practices in Section 1 result in the soils being highly disturbed, but largely protected and therefore at lower risk. However, Sections 2 to 5 are seen to be very sensitive to disturbance, resulting in a high erosion potential. Indeed, at locations in these Sections, erosion due to the existing lines is evident, and this has been confirmed by repeated complaints from stakeholders along the route. However it is understood that this erosion is largely due to poor maintenance of the access roads.

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

5.Identification of risk sources

This section presents the various biophysical impacts that may result from the construction of the transmission line. The biophysical impacts are discussed in terms of the various project stages and the activities connected to each stage. The project stages include construction and maintenance.

5.1Construction

The environmental impacts of the construction phase would be particularly sensitive to the management and sensible planning. These impacts include soil erosion and soil pollution.

The issues and activities connected to the construction phase include:

  • Clearing of vegetation for the installation of the transmission towers.
  • Clearing of areas for campsites.
  • Construction temporary access roads.
  • Disturbance of geological fossil sites.
  • Soil erosion.

5.2MAINTENACE DURING OPERATION

As with disturbance to any soils, the potential problem of subsequent erosion is seldom solved by initial rehabilitation after construction. A long-term maintenance programme needs to be established. Such a programme will need to be drawn up prior to construction.

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

Summary of potential risk of each activity per description area

Table 1

Activity / Impact / Magnitude of impact / Duration of impact
Clearing of vegetation for installation of foundation and towers /
  • Soil erosion
  • Loss of arable land
  • Loss of wetland related soils
  • Soil pollution
/
  • High
  • High
  • High
  • High
/
  • Medium to long term
  • Medium to long term
  • Medium to long term
  • Medium to long term

Clearing for campsite /
  • Soil erosion
  • Soil pollution
  • Soil Loss
/
  • High
  • High
  • High
/
  • Medium to long term
  • Long term
  • Long term

Construction temporary road /
  • Soil erosion
  • Soil pollution
  • Loss of arable land
  • Wetland related soils
/
  • High
  • High
  • High
  • High
/
  • Medium to long term
  • Long term
  • Short to long term
  • Medium to long term

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

5.3Criteria against which expected impacts are evaluated

Nature of the impact / Description of impact
Extent of the impact / Describe whether the impact will be : local extending only as far as the development site; or limited to the site and immediate surroundings; or will have an impact on the region, or will have an impact on a national scale or across international borders
Duration of the impact /
  • Short term (0-5 years)
  • Medium term (5-15 years)
  • Long term (f16-30 years)
  • Permanent

Intensity / The specialist should establish whether the impact is destructive or benign and should be qualified as low, medium or high. The specialist study must attempt to quantify the magnitude of the impacts and outline the rationale used.
Probability of occurrence /
  • Improbable, where the possibility of the impact to materialise is very low
  • Probable, where there is a distinct possibility that the impact will occur
  • Highly probable, where it is most likely that the impact will occur
  • Definite, where the impact will definitely occur

Status of the impact / The specialist should determine whether the impacts are negative, positive or neutral (“cost – benefit” analysis). The impacts are to be assessed in terms of their effect on the project and the environment. For example, an impact that is positive for the proposed development may be negative for the environment. It is important that this distinction is made in the analysis.
Accumulative impact / Consideration must be given to the extent of any accumulative impact that may occur due to the proposed development. Such impacts must be evaluated with an assessment of similar developments already in the environment. Such impacts will be either positive or negative, and will be graded as being of negligible, low, medium or high impact.

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

6.Impact description and assessment

The soils along the entire route are stable. However, the areas within section 2 are the most sensitive and critical areas along the entire route. This is due to the position of the soil on the steep slopes along the mountain range. Evidence of gully, water and wind erosion is present in the landscape.

Sections 1 to 5
Theme / Clearing of vegetation for installation of foundation and towers
Nature of Impact / Soil Erosion
Legal requirements / Conservation of Agriculture Resources Act (No. 43 of 1983)
Stage / Construction and Decommission / Operation
Extent of impact / Local / NA
Duration of impact / Potentially long term / NA
Intensity / Medium / NA
Probability of Occurrence / Definite / NA
Status of impact / Negative / NA
Accumulative Impact / Negative / NA
Level of Significance / Potentially high on steep slopes, Moderate in valleys / NA
Mitigation measures /
  • Construction to be done in dry season.
  • Work from top of slope downward.
  • Clearing of vegetation should be kept to a minimum.
  • If possible construction should happen without vegetation removal.
  • Avoid pristine area.

Level of significance after mitigation / Moderate to low
EMP requirements /
  • The rehabilitation of any dongas will be necessary in this area.
  • Erosion control will be necessary in this section of the proposed transmission line.
  • Long-term monitoring and maintenance requirements to be identified.
  • EMP to control construction to ensure that the best method is used.

Discussion
The steeper slopes long the route of the proposed transmission line are the most sensitive and critical area to be crossed by the line. These soils are highly susceptible to erosion. Construction activities will either disturb the vegetation cover or breach the protective topsoil is likely to result in severe soil loss. However, it is understood that limited vegetation clearing takes place during construction. Unless the vegetation is high or comprises large trees, it is merely driven over within the working area around the pylon. Nevertheless, some damage to the vegetation will occur and rehabilitation and long-term monitoring will be necessary, particularly in the Karoo areas where vegetation regeneration is slow.

765kV Soils ver 1.doc- 1 -

Kay Environmental Services / Kayode Okesanjo Gamma-Omega 765 kV transmission line

Pedology Report

Section: 1, 2, 3, 4, and 5
Theme / Clearing of vegetation for installation of foundation; towers and access roads
Nature of Impact / Loss of Wetland related soils
Legal requirements / Conservation of Agricultural Resources Act (No 43 of 1983), Environmental conservation Act (No 73 of 1989)
Stage / Construction and Decommissioning / Operation
Extent of impact / Local / Local
Duration of impact / Potentially long – term / Potentially long-term
Intensity / Moderate to high / Moderate
Probability of Occurrence / Highly probable / Probable
Status of impact / Negative / Negative
Accumulative Impact / Moderate / Moderate
Level of Significance / Moderate / Moderate
Mitigation measures /
  • Wetland areas should be avoided at all cost during the installation of towers
/ Ensure ongoing, regular monitoring and maintenance.
Level of significance after mitigation / Low / Low
EMP requirements /
  • Wetlands should be avoided in planning access roads for construction.
  • Any damage to wetlands must be rehabilitated before the site is abandoned.
  • Self-supporting tower should be installed in wetland area and pans.
  • No dumping of refuse and waste around wetlands.
  • While working in an area efforts should made to reduce compaction of soil.
  • Temporary road crossing wetland should not be compacted and must be remove after construction is finished.
  • For more site specific mitigation measures refer to Eskom’s Environmental Management Plan Report (EMPR) to the construction Phase of this project.
/
  • Set out monitoring and maintenance programme for each wetland.

Discussion
Wetlands are highly sensitive habitats being home to a group of highly specialized species, particularly bird species. Gaining access to construct this proposed powerline has the potential to impact heavily the wetlands in this study area. These wetlands must be avoided, as it is unacceptable to route roads through wetlands. The presence of wetlands along the study area is relatively low, and are all of a small scale. As such they can be avoided by careful placing of pylons and access roads in the bird area. Also included in the area are river crossings, particularly the smaller watercourses where formal roads or crossing points are not near to the route of the line. The same construction and management principles apply, though avoidance is seldom possible. The protection and rehabilitation of these points will be important.
Section 1
Theme / Construction of access roads
Nature of Impact / Soil Erosion
Legal requirements / Conservation of Agricultural Resources Act (No 43 of 1983), Environmental conservation Act (No 73 of 1989)
Stage / Construction / Operation
Extent of impact / Local / Local
Duration of impact / Long-term / Long-term
Intensity / Low / Low
Probability of Occurrence / Probable / Probable
Status of impact / Negative / Negative
Accumulative Impact / Negative / Negative
Level of Significance / Low to moderate but potentially high on the Southern Alternative / Low to moderate but potentially high on the Southern Alternative
Mitigation measures /
  • During construction of access road track based vehicle should be used especially in wetland surroundings.
  • Compaction should minimised
  • Any foreign material used to maintain the temporary road must be remove after construction, unless used to improve the road and for erosion control
/
  • All rehabilitation and re-vegetation programmes must be monitored.
  • Existing access road should be used were ever possible.

Level of significance after mitigation / Low / Low
EMP requirements /
  • During construction site preparation, vegetation removal and the erection of buildings must happen simultaneously, to ensure that no large tracts of land are left exposed at any point in time. Vegetation clearance should be kept to the dry season.
/
  • All access roads must be maintained and storm water drainage system implemented.
  • Vegetation removal must be kept to a minimum.