Hydrological Assessment of the Proposed Haga Haga Wind Energy Facility
Total Page:16
File Type:pdf, Size:1020Kb
HYDROLOGICAL ASSESSMENT OF THE PROPOSED HAGA HAGA WIND ENERGY FACILITY Project No. SAS-06 Version 3 July 2018 HYDROLOGIC CONSULTING CONSULTING HYDROLOGISTS email: [email protected] | phone: +27 72 239 0974 HYDROLOGICAL ASSESSMENT OF THE PROPOSED HAGA HAGA WIND ENERGY FACILITY Prepared For Scientific Aquatic Services CC Scientific Aquatic Services CC CC Reg No 2003/078943/23 Vat Reg. No. 4020235273 PO Box 751779 Gardenview 2047 Tel: 011 616 7893 Fax: 086 724 3132 E-mail: [email protected] Prepared By Hydrologic Consulting (Pty) Ltd Version 3 Project No. SAS-06 July 2018 Hydrologic Consulting (Pty) Ltd P a g e | i TABLE OF CONTENTS 1 INTRODUCTION ................................................................................................................................ 1 1.1 BACKGROUND ........................................................................................................................................... 1 1.2 SCOPE OF WORK ...................................................................................................................................... 1 1.3 REGIONAL SETTING AND SITE LAYOUT ................................................................................................. 1 2 BASELINE INFORMATION ................................................................................................................. 4 2.1 RAINFALL ................................................................................................................................................... 4 2.2 1-DAY DESIGN RAINFALL DEPTHS .......................................................................................................... 6 2.3 EVAPORATION ........................................................................................................................................... 6 2.4 AVERAGE CLIMATE ................................................................................................................................... 7 2.5 TOPOGRAPHY AND SLOPES ................................................................................................................... 8 2.6 HYDROLOGY .............................................................................................................................................. 8 2.7 SOILS, VEGETATION AND LAND-COVER .............................................................................................. 10 3 STORMWATER AND EROSION CONTROL MANAGEMENT PLAN .................................................... 13 3.1 CLEAN AND DIRTY AREAS ..................................................................................................................... 13 3.1.1 IDENTIFICATION OF SENSITIVE INFRASTRUCTURE ...................................................................... 14 3.2 CONSTRUCTION PHASE- MANAGEMENT PLAN .................................................................................. 16 3.2.1 REVIEW OF POTENTIALLY SENSITIVE INFRASTRUCTURE............................................................ 17 3.2.2 SITE-SPECIFIC MANAGEMENT PLANS ............................................................................................. 22 3.2.3 GENERIC MANAGEMENT PLANS ....................................................................................................... 22 3.2.4 STORMWATER MANAGEMENT AND EROSION CONTROL ............................................................. 23 3.2.5 RIVER CROSSINGS ............................................................................................................................. 26 3.3 OPERATIONAL PHASE- MANAGEMENT PLAN ...................................................................................... 27 4 CONCLUSIONS AND RECOMMENDATIONS .................................................................................... 28 5 REFERENCES ................................................................................................................................. 29 APPENDIX A – STORMWATER CALCULATIONS .................................................................................... 30 A.1 MODEL CHOICE ..................................................................................................................................... 30 A.2 MODEL SETUP ........................................................................................................................................ 30 A.2.1 DESIGN STORM ........................................................................................................................................ 30 A.2.2 MODEL PARAMETERISATION .................................................................................................................. 30 A.3 MODEL RUN ............................................................................................................................................. 30 Report No. SAS-06 HYDROLOGICAL ASSESSMENT OF THE PROPOSED HAGA HAGA WIND ENERGY July, 2018 Version 3 FACILITY Hydrologic Consulting (Pty) Ltd P a g e | ii LIST OF FIGURES FIGURE 1-1: REGIONAL SETTING ............................................................................................................................. 2 FIGURE 1-2: SITE LAYOUT ......................................................................................................................................... 3 FIGURE 2-1: WEATHER STATIONS AND MEAN ANNUAL PRECIPITATION ............................................................ 5 FIGURE 2-2: AVERAGE MONTHLY CLIMATE FOR THE SITE................................................................................... 7 FIGURE 2-3: TOPOGRAPHY AND HYDROLOGY ....................................................................................................... 9 FIGURE 2-4: SOILS AND VEGETATION ................................................................................................................... 11 FIGURE 2-5: LAND-COVER ....................................................................................................................................... 12 FIGURE 3-1: FLOW PATHS AND POTENTIALLY SENSITIVE INFRASTRUCTURE ................................................ 15 FIGURE 3-2: DETAILED ASSESSMENT OF TURBINES 01, 02, 14 & 17 ................................................................. 18 FIGURE 3-3: DETAILED ASSESSMENT OF TURBINES 20, 26, 29 & 33 ................................................................. 19 FIGURE 3-4: DETAILED ASSESSMENT OF TURBINES 34, 36, 39 & 41 ................................................................. 20 FIGURE 3-5: DETAILED ASSESSMENT OF TURBINES 42 & LAYDOWN AREA .................................................... 21 FIGURE 3-6: GENERIC EXAMPLE STORMWATER/EROSION CONTROL MANAGEMENT.............................. 23 FIGURE 3-7: TYPICAL BERM AND CHANNEL FOR STORMWATER/EROSION MANAGEMENT SYSTEM .......... 24 FIGURE 3-8: TYPICAL SILT FENCE (AFTER ENVIRONMENT PROTECTION AGENCY) ....................................... 25 LIST OF TABLES TABLE 2-1: AVERAGE MONTHLY RAINFALL DISTRIBUTION (LYNCH, 2004) ......................................................... 4 TABLE 2-2: 24-HOUR STORM DEPTH ........................................................................................................................ 6 TABLE 2-3: MONTHLY POTENTIAL EVAPOTRANSPIRATION DISTRIBUTION (SCHULZE AND LYNCH, 2006) .... 7 Report No. SAS-06 HYDROLOGICAL ASSESSMENT OF THE PROPOSED HAGA HAGA WIND ENERGY July, 2018 Version 3 FACILITY Hydrologic Consulting (Pty) Ltd P a g e | iii EXECUTIVE SUMMARY Hydrologic Consulting (Pty) Ltd has been appointed by Scientific Aquatic Services CC, to undertake a hydrological assessment for the proposed Haga Haga Wind Farm. The project consists of 42 wind turbines, to be installed atop various hills near Haga Haga, within the Great Kai Local Municipality, approximately 45km north-east of East London in the Eastern Cape Province of South Africa. Additional infrastructure in the form of a Substation, Office and Laydown area as well as linear infrastructure (overhead powerline, electrical underground cables and roads) are also proposed. This hydrological assessment has been undertaken to inform both Environmental and Water Authorisation processes. The scope of work in the hydrological assessment included the following: • Baseline Assessment – sourcing of baseline climatic data to be used in hydrological calculations. This included the interrogation of rainfall data (including site specific design rainfall), evaporation, soils, vegetation, land-cover, as well as a regional and local hydrological assessment; • Conceptual Stormwater and Erosion Control Management Plan – development of both construction and operational management principles which can be used to ensure the impact of the proposed operation on receiving water resources is kept to a minimum. This includes a buffer approach adopted for the rivers traversing the site; and • Technical Report – detailing the achieved scope of work. Baseline information including average rainfall data, depth-duration-frequency design rainfall estimates, evaporation data, soils, vegetation and land-cover information, as well as both regional and local hydrological characteristics have been considered for the proposed Haga Haga Wind Energy Facility in the Eastern Cape. The results of this baseline assessment indicate that the proposed site is located in a medium to high rainfall, low to medium evaporation region of South Africa, with moderate to mild slopes. The impact of the proposed project on surface water resources