Appendix D3 Hydrogeological Specialist Report
Total Page:16
File Type:pdf, Size:1020Kb
Ground Floor, Bay Suites 1a Humewood Rd, Humerail Port Elizabeth, 6001 P O Box 21842 Port Elizabeth 6000 South Africa T: +27 (0) 41 509 4800 F: +27 (0) 41 509 4850 E: [email protected] www.srk.co.za 29 August 2018 535889 Algoa Consulting Mining Engineers No 2 Deer Park Deer Park Estate Port Elizabeth Attention: Mr Clayton Weatherall-Thomas Dear Clayton Hydrogeological Investigation at a Proposed Site for Mining in the Driftsands Area, Port Elizabeth 1. Introduction SRK Consulting South Africa (Pty) Ltd (SRK) was appointed by Algoa Consulting Mining engineers (ACME) to conduct a groundwater investigation at the proposed Site for the development of a mine in the Driftsands area in Port Elizabeth. SRK understands that a hydrogeological investigation is required to determine the nature and sensitivity of the groundwater environment underlying the study area, and the potential risks that the development may pose to the groundwater environment during its operation. The study area is situated across a number of properties, namely the remainder of Erf 18 Schoenmakerskop, Erf 121 Skoenmakerskop, remainder of Erf 1256 Summerstrand and Erven 1266, 2546, 2962 and 2963 Summerstrand. The study area is situated in the M20A Quaternary Catchment of the DWS. According to the Background Information Document that we received from the Client, “the mining of sand minerals would be a simple operation, whereby only free-digging opencast open pit mining methods would be deployed. No blasting with explosives will take place, but only free-digging mining methods. Infrastructure development will be limited to the construction of roads and a portable wendy house for the security guard with a chemical latrine. No workshops will be built at the mine and no diesel, paints, oils or other hydrocarbons will be stored on-site. A chemical will be added during the screening process to provide the correct sand particle size. No water would be needed for the mining operation other than the water truck for dust suppression of the roads during windy conditions, and the wetting of loads.” Partners R Armstrong, AH Bracken, N Brien, JM Brown, CD Dalgliesh, BM Engelsman, R Gardiner, M Hinsch, African Offices: Group Offices: W Jordaan, WC Joughin, DA Kilian, S Kisten, JA Lake, V Maharaj, DJ Mahlangu, I Mahomed, HAC Meintjes, Cape Town + 27 (0) 21 659 3060 Africa MJ Morris, GP Nel, VS Reddy, PJ Shepherd, MJ Sim, VM Simposya, HFJ Theart, KM Uderstadt, AT van Zyl, Durban + 27 (0) 31 279 1200 Asia MD Wanless, ML Wertz, A Wood East London + 27 (0) 43 748 6292 Australia Directors AJ Barrett, CD Dalgliesh, WC Joughin, V Maharaj, VS Reddy, PE Schmidt, PJ Shepherd Johannesburg + 27 (0) 11 441 1111 Europe Pietermaritzburg + 27 (0) 33 347 5069 North America Associate Partners PJ Aucamp, S Bartels, LSE Coetser, SG Jones, F Lake, L Linzer, L Nedeljkovic, RD O’Brien, Port Elizabeth + 27 (0) 41 509 4800 South America S Reuther, T Shepherd, JJ Slabbert, JS Stiff, M van Huyssteen, D Visser Pretoria + 27 (0) 12 361 9821 Consultants JR Dixon, PrEng; GC Howell, PrEng; T Hart, MA, TTHD; PR Labrum, PrEng; RRW McNeill, PrTech Eng; Rustenburg + 27 (0) 14 594 1280 PN Rosewarne, PrSci Nat, MSc; AA Smithen, PrEng; TR Stacey, PrEng, DSc; OKH Steffen, PrEng, PhD; Accra + 23 (3) 24 485 0928 PJ Terbrugge, PrSci Nat, MSc; DJ Venter; PrTech Eng Lubumbashi + 243 (0) 81 999 9775 SRK Consulting (South Africa) (Pty) Ltd Reg No 1995.012890.07 SRK Consulting Page 2 2. List of Abbreviations NGA: National Groundwater Archive DWS: Department of Water and Sanitation TMG: Table Mountain Group mS/m: milliSiemens per meter EC: Electrical Conductivity RBCA: Risk Based Corrective Action CSM: Conceptual Site Model 3. Scope of Works SRK proposed the following Scope of Works in our proposal dated 11 June 2018 “Proposal: Hydrogeological Investigation at a Proposed Site for Mining in the Driftsands Area, Port Elizabeth, Eastern Cape” and was accepted by the Client: Conduct a desktop assessment of the hydrogeology of the Site and surrounding area (approximately 500 m radius of the boundary supplied by the Client). This will include a study of the geology, hydrogeology and topography; querying the National Groundwater Archive (NGA) – a database of the Department of Water and Sanitation (DWS) that contains information om boreholes that have been registered or licensed with the DWS; and assessing historical reports of groundwater investigations in the area (if available). Conduct a hydrocensus, where neighbouring properties around the Site (up to a 500 m radius of the Site boundaries) will be visited. Information on existing boreholes, including borehole depth, water use, water level, the aesthetic character of the water and borehole position; will be gathered where available. Please note that SRK assumes that the neighbouring property owners are aware of the planned development. In urban areas (e.g. Summerstrand) a sample of properties will be visited only. The hydrocensus does not necessarily mean that all existing boreholes will be identified and located around the Site. This census is intended to gather groundwater information and is subject to the availability of such information. Where site access is denied, or existing boreholes are not shown to SRK, no information will be gathered. SRK can therefore not guarantee that all boreholes will be surveyed within the mentioned area. Provide a description of the potential impacts of the development on the hydrogeological regime in general, particularly during the operational phase. Compile a letter report, summarising the findings of the investigation. Recommendations on appropriate mitigatory measures will be made, where required, to reduce the impact of the proposed development upon the groundwater quality of the area. 4. Results The results of the investigation are discussed in the section below. It must be noted that this investigation took place during a drought period in the Eastern Cape; and water levels may be lower than during normal rainfall conditions. 4.1 Desktop Study 4.1.1 Geology According to the publication “The Geology of the Port Elizabeth-Uitenhage Area” by F.G le Roux of the Council for Geoscience (2000), the geology underlying the proposed development comprises the Schelmhoek Formation of the Algoa Group. This formation is underlain by the Peninsula Formation of the Table Mountain Group (TMG); and to the west, potentially by the Sardinia Bay Formation. Refer to Figure 1 for a map with the geology of the area. KRUR/NELG 535889 ACME Driftsands Mine Groundwater Investigation_Jul2018_Rev1 Aug 2018 SRK Consulting Page 3 The Schelmhoek Formation comprises unconsolidated, windblown fine- to medium-grained sand and occurs up to 6 km inland from the coast. The sand is calcareous quartz sand of aeolian origin, and can be up to 140 m thick in some areas. The Peninsula Formation comprises light-grey supermature sandstone that is quartzitic in places. Vein quartz and subordinate shale layer are present in places. The maximum thickness of the layer is 3000 m. The Sardinia Bay Formation is an arenaceous (sandstoney) formation that is seen as folded metasedimentary outcropping along the coast in the Schoenmakerskop and Sardinia Bay area. The formation comprises a basal metaconglomerate which is overlain by quartzitic sandstone. The sandstone is intercalated with black phyllitic shale and conglomerate. A few perennial fresh-water springs daylights on the coast west of Schoenmakerskop, and is a result of groundwater movement towards the sea, on the contact between the Quaternary deposits and the TMG. 4.1.2 Hydrogeology According to the publication “An Explanation of the 1:500 000 General Hydrogeological Map of Port Elizabeth 3324” by P.S Meyer of the Department of Water Affairs and Forestry (1998), the Quaternary alluvial deposits (which includes the Schelmhoek Formation) can deliver yields ranging between 0.1 and 15 L/s. These sandy deposits can be described as a primary aquifer1. A yield analysis indicated that 7% of boreholes yield less than 0.5 L/s and 26% yield more than 5 L/s. Groundwater quality varies substantially, with conductivities ranging between 20 mS/m (potable) and 600 mS/m (not potable, SANS 241:2015 Drinking Water Standard Limit for conductivity is 170 mS/m). These changes in water quality can be ascribed to changes in geology and depth of drilling. Sodium, calcium magnesium, chloride, alkalinity and sulphate often exceeds the maximum allowable limits for drinking water for this group. A networks of joints and fractures control infiltration, recharge, storage and movement of groundwater in the often brittle TMG formations (of which the Peninsula and Sardinia formations form a part). Fracturing may extend down several hundred meters and deep groundwater circulation is one of the notable groundwater characteristics of the TMG. Despite the often highly fractured nature of the TMG, secondary groundwater storage is often limited, which could result in rapid depletion of an aquifer when water is abstracted. Springs often issue from the TMG sandstones. High-yielding boreholes (> 5 L/s) have been developed in the TMG (and its water quality is generally between 10 and 100 mS/m (the SANS 241:2015 specifies 170 mS/m as the Standard Limit for drinking). 1 Aquifers in which water moves through the integranular spaces formed at the same time as the geological formation. KRUR/NELG 535889 ACME Driftsands Mine Groundwater Investigation_Jul2018_Rev1 Aug 2018 SRK Consulting Page 4 Figure 1: Geology KRUR/NELG 535889 ACME Driftsands Mine Groundwater Investigation_Jul2018_Rev1 Aug 2018 SRK Consulting Page 5 4.1.3 National Groundwater Archive (NGA) Database During the desk study, the NGA database of the Department of Water and Sanitation (DWS) was searched for information on existing boreholes within a 1 km radius of the proposed study area. Forty seven (47) boreholes were located, of which 32 had information stored on the database (other than the identifier and coordinate).