HOEKPLAATS Dolomite (Pty) Ltd Preliminary Groundwater Assessment: Portion 23 (A Portion of Portion 15) of the farm Hoekplaats 384 JR DATE: October 2010 REVISION Final REFERENCE: 215_Hoekplaats COMPILED FOR: Umhlaba Environmental Consulting CC PO Box 731504 Fairland 2030 COMPILED BY: GROUNDWATER SQUARE Consulting Groundwater Specialists HOEKPLAATS Dolomite (Pty) Ltd – Preliminary Groundwater Assessment: Portion 23 (a Portion of Portion 15) of the farm Hoekplaats 384 JR Ref:215_Hoekplaats (Oct’10) Executive Summary Umhlaba Environmental Consulting CC contracted Groundwater Square on behalf of Hoekplaats Dolomite (Pty) Ltd to compile a preliminary hydrogeological desk study investigation to provide guidance on any future groundwater studies that may be required. The proposed opencast dolomite mine is on situated Portion 23 (a portion of Portion 15) of the Farm Hoekplaats 384 JR approximately 15km south-west of Pretoria. Mining will entail a conventional drilling and blasting opencast operation. The targeted mining area will be approximately 300m x 500m in size and approximately 40m deep. The following main conclusions were reached: The regional dolomitic aquifers was highlighted as a significant source of drinking- and irrigation water; Locally the direction of groundwater movement from the site is in a north-westerly direction towards the Hennops River and the Aalwynkop Spring. The northern regions of the quarry floor is expected to be at lower elevations than the Aalwynkop Spring; The depth of mining will be ±30m below the natural groundwater level. Groundwater will have to be pumped from the pit; The Zwartkop dyke may potentially compartmentalise the aquifers (depending on its weathering depth) to restrict the extent of the groundwater dewatering cone around mining; It is anticipated that the aquifer within the proposed mining area may be low yielding due to being chert-poor and with limited leaching of the dolomites (to the depth of mining); Borehole EUB-6 is situated on Ptn.23 of the farm Hoekplaats 384 JR. Six external user’s boreholes were indentified within a 1km radius of the property. The reported total daily abstraction recorded within a 1km of Portion 23 totals approximately 38m3/d. Once the mine intersects the natural groundwater table, groundwater will be pumped from the pit, resulting in a cone of dewatering developing around the pit. Although the extent of dewatering may be limited/restricted due to various factors, the potential impact on external users’ boreholes and impact on base-flow to the Hennops River and Aalwynkop Spring requires further investigation. The main recommendations for further work therefore focussed on the utilisation of a numerical groundwater flow model to determine/evaluate the potential impacts on external users’ borehole yields and groundwater base-flow toward the Hennops River and the Aalwynkop Spring. Dedicated hydrogeological boreholes should be drilled and pump tested to determine hydraulic aquifer parameters, for inclusion in the numerical model. GROUNDWATER SQUARE Page ii HOEKPLAATS Dolomite (Pty) Ltd – Preliminary Groundwater Assessment: Portion 23 (a Portion of Portion 15) of the farm Hoekplaats 384 JR Ref:215_Hoekplaats (Oct’10) Table of Contents Executive Summary ...............................................................................................................................ii Table of Contents ..................................................................................................................................iii 1. INTRODUCTION ............................................................................................................................ 4 1.1. Background.................................................................................................................................. 4 1.2. Mining Information ....................................................................................................................... 4 2. TERMS OF REFERENCE .............................................................................................................. 4 3. SETTING ........................................................................................................................................ 5 3.1. Regional Setting .......................................................................................................................... 5 3.2. Rainfall......................................................................................................................................... 6 3.3. Land-use...................................................................................................................................... 6 3.4. Morphology and Drainage ........................................................................................................... 7 3.5. Soils ............................................................................................................................................. 7 3.6. Local Setting................................................................................................................................ 7 4. GEOLOGY...................................................................................................................................... 9 4.1. Regional Geology ........................................................................................................................ 9 4.2. Local Geology............................................................................................................................ 10 5. HYDROGEOLOGY....................................................................................................................... 11 5.1. Regional Hydrogeology ............................................................................................................. 11 5.2. Local Geohydrology................................................................................................................... 13 5.2.1. Groundwater Use .................................................................................................................. 13 5.2.2. Hydrocensus.......................................................................................................................... 13 5.2.3. Depth to Groundwater Level and Hydrostatic Fluctuations.................................................. 14 5.2.4. Groundwater Flow Direction.................................................................................................. 16 5.2.5. Aquifer Yielding Potential ...................................................................................................... 16 5.2.6. Groundwater Quality.............................................................................................................. 16 5.2.7. Surface Water Quality ........................................................................................................... 18 6. POTENTIAL IMPACTS................................................................................................................. 20 6.1. Identification of Potential Impacts.............................................................................................. 21 6.2. Discussion of Potential Impacts................................................................................................. 21 7. RECOMMENDATIONS ................................................................................................................ 22 References ........................................................................................................................................... 23 GROUNDWATER SQUARE Page iii HOEKPLAATS Dolomite (Pty) Ltd – Preliminary Groundwater Assessment: Portion 23 (a Portion of Portion 15) of the farm Hoekplaats 384 JR Ref:215_Hoekplaats (Oct’10) 1. INTRODUCTION 1.1. Background Umhlaba Environmental Consulting CC recently compiled an Environmental Scoping Report for HOEKPLAATS Dolomite (Pty) Ltd. The proposed opencast dolomite mine is situated on Portion 23 (a portion of Portion 15) of the Farm Hoekplaats 384 JR approximately 15km south-west of Pretoria. Umhlaba approached Groundwater Square undertake a preliminary hydrogeological investigation. It was decided to perform a desk study, which could provide guidance (and serves as the basis) for any future groundwater studies that might be required. 1.2. Mining Information The targeted mining area will be approximately 300m x 500m in extent with a maximum projected depth of ±40m. The proposed mining will entail a conventional drilling and blasting opencast operation with the frequency of blasting being dependant on product demand. Rock will be crushed and screened to include the following products: 19mm concrete stone; 13.2mm concrete stone; 9.5mm concrete stone; ≤6.7mm super-sand. The installation of services will include the construction of the following: Plant; Settlement dam; Workshops and fuel facilities; Administration offices; Demarcation of the salvage yard; Connection to the water and electricity supply; Sanitation facilities. 2. TERMS OF REFERENCE Based on the project objectives, the following Terms of Reference were proposed by Groundwater Square on 07/08/2010: Collate and perform desktop exercise of available geological and hydrogeological maps/reports pertaining to the study area; Compile a hydrogeological interpretation of the expected groundwater system; Identify likely impacts in view of the Dolomite Mine design and geological drilling (no impact assessment