Executive Summary. Geotechnical Investigations at Fort Victoria Page 3 of 52

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3 Executive Summary In January 216, the Central Electricity Board (CEB) awarded Water Research Co Limited a contract (Ref. Q18298) to carry out geotechnical investigations at Fort Victoria power station. The investigation aimed to support the design and construction of a proposed 6,5m 3 heavy fuel oil tank (approximate diameter 23m & height 14m). The field works comprised of 4No. trial pits and 1No. coreholes with SPT tests. The trial pits were generally excavated at the maximum explored depth of 2.55m bgl and the corehole was drilled to 2.om bgl. The identified soil sequence generally consists of approx. 1m of Fill Material, ii) 12.5m of Clay (Completely to Highly Weathered Basalt), and iii) Moderately to Slightly Weathered Basalts. Although 6m of Fill Material was observed at only one location, corehole. Groundwater prevailed as from a depth of 3.5m. Selected samples were collected from the trial pits were couriered to the Gets Laboratory for geotechnical testing and to Alcontrol for contaminant tests. Engineering Fill is recommended as the founding stratum for the tank if shallow circular raft foundations are entertained. It is proposed that the existing Fill Material and natural strata is excavated down to 2.m and replaced with Engineering Fill. Bearing capacity and settlements were estimated by considering two scenarios; i) a double layered profile of medium dense Gravel over firm Clay and ii) a triple layered profile of medium dense Gravel underlain by loose gravel (Fill Material) and firm Clay. The assessment indicated that the allowable bearing capacity (factor of safety) estimated is 145kPa with a maximum settlement of 14mm and a differential; settlement of 1mm at a founding depth of.6m bgl. If shallow foundations are implemented, the tank is expected to sink uniformly. According to Klepikov (1989) the magnitude of settlement (maximum of 14mm) may be considered as acceptable. Settlements may be curtailed by reducing the designed height of the tank. The settlements can be mitigated by using piles as foundation solution by transferring the load to the competent stratum at a depth of 14.m. This solution shall also increase the bearing capacity. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 3 of 52

4 Contents Executive Summary 3 Introduction 7 Desk study information Site location and topography Published geology 8 Field and laboratory works Geotechnical investigation works Rotary core drilling Trial Pits In Situ Tests Laboratory testing 13 Results and ground conditions Identified soil profile Groundwater Dynamic Cone Penetration Test Results Plate Load Test Results Chemical Environment 2 Geotechnical engineering assessment Identified Soil Profile Foundation options Bearing capacity and settlement for Engineering Fill on natural strata (Scenario 1) Bearing capacity and settlement for Engineering Fill on Fill Material (Scenario 2) Deep foundations 28 References 3 OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 4 of 52

5 Figures 31 Appendix A Site Layout 39 Appendix B Photographs of Site Works 4 Appendix C Exploratory Hole Logs 43 Appendix C-1 Corehole Logs 44 Appendix C-2 Photographs of Cores 45 Appendix C-3 Trial Pit Logs 46 Appendix C-4 Photographs of Trial Pits 47 Appendix C-5 Geological Profiles 48 Appendix D In-Situ Testing 49 Appendix D-1 DCP Test results 5 Appendix D-2 Plate Load Test Results 51 Appendix E Geotechnical Laboratory Test Schedules and Results 52 Appendix F Contamination Test Schedules, Standards and Results 53 LIST OF TABLES Table 3-1 Summary of rotary drilled coreholes... 9 Table 3-2 Summary of Trial Pits... 1 Table 3-3 Summary of SPT N results Table 3-4 Location and Depths of DCPT Table 3-5 Location and Depths of PLT Table 3-6 Standards for laboratory tests Table 3-7 Summary of Laboratory Testing Results on clayey material OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 5 of 52

6 Table 3-9 Summary of Laboratory Testing Results on Rock Cores Table 4-1 Summary of strata encountered in metres Table 4-2 Summary of DCPT Results Table 4-3 PLT Results Summary... 2 Table 4-4 Soil Chemical Tests Summary Table 4-5 Water Chemical Tests Summary Table 5-1 Cast-in-situ piles indicative characteristics LIST OF FIGURES Figure 2-1 General location of the site Figure 2-2 Site Location Figure 2-3 Aerial Map of site and location of Trial Pits and Coreholes Figure 2-4 Location of the site on geological map Figure 2-5 Location of the site on Soil Map Figure 2-6 Standard Penetration Test N Value Variation with Depth As per Stratum Figure 2-7 Rock Quality Designation Variation with Depth Figure 2-8 A Line Plasticity Chart OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 6 of 52

7 Introduction On 7 th January 216, the Central Electricity Board (CEB) awarded Water Research Co Limited (Water Research) a contract (Ref. Q18298) to carry out geotechnical investigations at Fort Victoria power station, in the district of Port Louis. The geotechnical investigation aimed to support the design and construction of a proposed 6,5m 3 heavy fuel oil tank (approximate diameter 23m & height 14m) and ancillary infrastructures. Appendix A depicts the proposed layout of the tank and the site. Water Research s brief comprised the following items: Formation of 4No. trial pits Drilling 1No.rotary coring borehole Soil and rock sampling. Undisturbed soil samples were 5mm diameter U2 samplers. Rock cores were 52mm diameter. Disturbed samples included large and small bulks Compaction, compressibility, strength and chemical laboratory tests Report on findings and general geotechnical evaluation. This Report is presented in the following format: Desk study information for the site, including geological maps and plans Factual information comprising: description of fieldwork and exploratory hole logs Geotechnical assessment comprising: profile definition; discussion on geotechnical parameters for foundation design; recommendations for selection of foundation solutions; general foundation comments including bearing capacity and settlements. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 7 of 52

8 Desk study information 2.1 Site location and topography The subject site is situated within the Fort Victoria power station, in the locality of Bain des Dames (Figures 2.1 to 2.3). The site lies on the shoreline of the western coast and is surrounded by residential dwellings. Bain des Dames public beach adjoins the site to the north west. The site can be accessed from Cassis Road which branches off the M1 motorway. The site is an operational power station which comprises of existing tanks and heavy engines. The investigated area is on a strip of land in the western portion of the power station. The area was being used as a storage spot with scrap metals and other heavy duty materials. According to the Client there used to be a trench crossing the site after which it was backfilled. The site elevations generally vary between 2m and 5m amsl. The site is flat with no salient topographical feature. Surface water run-off is expected to be channelled towards the ocean. 2.2 Published geology According to the Carte Geologique au 1:5, of Mauritius, the site is underlain by fresh basalt of the Intermediate volcanic series (Figure 2.4, Ref. 1). The intermediate volcanic series are composed of basaltic flows overlying basalt agglomerate. The basalts are not very homogeneous in composition but, on the whole, they are made up of fine grained olivine rocks, grey to black in colour. The very compact types are rather rare, and are in general porous and often vesicular, the vesicles being sometimes infilled with a powdery bluish material. They are also slightly fissured and in some places the fissures and cavities are filled with light cream coloured clay (Ref. 2). According to the Soil Map of Mauritius (Figure 2.5, Ref. 3) the natural strata on the site area consists of Low Humic Latosols. These soils occur in the sub-humid and lower rainfall zones from 1,mm to 2,75mm annually, in areas with a distinct dry season. They are deep (+1cm) to moderately deep soils (+6cm) with good internal drainage. They have a weak to moderately strong structured A horizon varying from red to brown in colour over a red to reddish brown B horizon. The texture of the A horizon is silty clay to clay; kaolinite is the dominant clay mineral (Ref. 2). OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 8 of 52

9 Field and laboratory works 3.1 Geotechnical investigation works The scope of fieldworks was specified in the Tender Document and was undertaken in general accordance with BS 593 (1999) (Ref. 4). The site works were carried out between the 2 nd and 23 rd February 216. The location of the Trial Pits and Corehole are shown in Appendix A; the photographs of the site activities are presented in Appendix B. The following sections present a general description of the works carried out. 3.2 Rotary core drilling 1No. corehole were drilled by rotary drilling techniques in order to obtain information on the underlying geology, delimit the ground profile and carry out in situ testing. The corehole was designated as BH 1. Core recovery drilling was completed using a triple tube core barrel (hole diameter 76mm and core diameter 52mm) followed by NW casing (outside diameter of 88.9mm and inside diameter of 76.2mm). Water was used as flushing medium. During coring in soft and weak materials, circulation of water was stopped so as to achieve the maximum recovery. The term dry coring is used in such cases. The coordinates of the exploratory borehole and the explored depth are shown in Table 3.1. The coordinates reproduced in Table 3-1 below are from Google Earth. Table 3-1 Summary of rotary drilled coreholes Corehole No. Depth (m) Easting Northing Elevation (m) Installations BH m PVC casing The core samples recovered from the rotary coreholes were photographed, sampled and described according to BS593: 1999 (Ref. 4). The geological description of the strata encountered are given on the corehole logs along with the assessment of Total Core Recovery (TCR), Solid Core Recovery (SCR) and Rock Quality Designation (RQD), each expressed as a percentage of the individual core runs. Fracture Index (FI) representing the number of clearly identifiable fractures per meter of intact core pieces is also reported. The corehole logs and photos are presented in Appendices C-1 and C-2. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 9 of 52

10 3.3 Trial Pits 4No. Trial Pits were excavated using a JCB 4CX mechanical backhoe excavator at the locations and depths shown in Table 3-2. Small and large bulk disturbed samples were taken at regular intervals where possible for geotechnical, chemical and contamination testing the list of samples taken are presented in Table 3-2. The logs and photos of the Trial Pits are presented in Appendices C-3 and C-4, respectively. The coordinates reproduced in Table 3-2 are from Google Earth. Trial Pits TP 1 and 2 were left open for three weeks in order to observe the potential presence of groundwater. After 3 weeks, black petroleum like based product was observed at the base and along the walls of trial pit TP 2 on 23 rd February 216. Table 3-2 Summary of Trial Pits TP No. Depth (m) Samples Intervals Easting (UTM) Northing (UTM) Elevation (m) TP ; TP ; TP ; TP ; In Situ Tests Standard Penetration Tests 6No. of Standard penetration tests (SPT) were carried out in cohesive and granular soils in accordance with BS1377: Part 9 (199) (Ref. 5). The test consisted of driving a 5mm split spoon by means of a 63.5kg hammer falling a height of 76mm. The SPT blow count N is the number of blows required to drive the spoon by 3mm after initially seating the spoon by 15mm. Tests for which the full penetration of 45mm could not be achieved after 5 blows are termed as Refusals. Table 3-3 shows a summary of the SPT test results. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 1 of 52

11 Table 3-3 Summary of SPT N results BH No. Depth (m) Stratum N value Recovery Fill Material gravelly Clay 1 4 BH Fill Material Gravels and R Cobbles Fill Material gravelly Clay CWB with cobbles between 7.84m and R m CWB C to HWB Dynamic Cone Penetrometer Test TRRL type (Ref. 6) dynamic probing tests were carried out by Geotechnical Services Ltd (GETS) on the trial pits at depths shown in Table 3-4. Table 3-4 Location and Depths of DCPT TP No. DCPT No. Depth (m) Stratum TP 1 1 Ground level Fill Material Clay 2 1. C to HWB TP 2 1 Ground level Fill Material Gravel 2 1. HWB Dynamic probing involves driving a 2mm diameter solid cone (6 o angles) into the ground using repeated blows of a hammer with a mass of 8kg, falling a distance of 575mm. Typically, the rate of driving is between 15 to 3 blows per minute. As the cone is driven into the ground, the number of blows for each 1mm penetration is recorded. The penetration resistance provides a measure from which the California Bearing Ratio (CBR) can be calculated using the following formula: Log1 (CBR) = log1 (mm/blow) OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 11 of 52

12 The details of the tests, the penetration vs blows and CBR results are presented in Appendix D-1. The existing asphalt and concrete road surfaces at the location of the tests were removed previous to the execution of the tests Plate Load Test 3No. maintained Plate Load tests (PLT) were carried out by Geotechnical Services Ltd (GETS) on trial pits at depths as shown in Table 3-5. Table 3-5 Location and Depths of PLT TP No. PTL No. Depth (m) Stratum TP 1 PLT 1 Ground level Fill Material very gravelly sandy Silt TP 2 PLT 2 Ground level Fill Material silty Gravel PLT 2 1. CWB Clay The Plate Load Tests were carried out with a Geotechnical Testing Equipment s hydraulically jacked system. The tests were carried out in accordance with BS1377: Part 9:199 (Ref.5) using a 35mm diameter plate on a maintained load basis and following the procedure: 1. Apply seating load to produce deflection between.25 mm and.51 mm. 2. Record and release load. 3. Apply ½ seating load. 4. Allow dial needles to come to rest. 5. Set dial needles to zero. 6. Apply load above ½ seating load. 7. Allow action of load to continue until rate of deflection of not more than.3 mm/min has been maintained for at least two consecutive minutes. 8. Record load and deflection readings for applied load increment. 9. Apply next loads increments up to maximum or failure, each time repeating (7) 1. For final load increment maintain load until deflection of not more than.3 mm/min for at least two consecutive minutes. 11. Unload in steps and release the load to load at which dial gages were set to zero. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 12 of 52

13 The complete set of results and the load displacement curves are presented in Appendix D Laboratory testing The laboratory schedule was prepared as stipulated in the tender document and shown in Appendix E. The laboratory testing aimed at determining site parameters concerning the classification, chemical and strength properties of the strata to enable geotechnical design. The programme of laboratory testing was carried out in accordance with BS1377 (199) (Ref. 5) at the Geotechnical Services (GETS), University of Mauritius Laboratories and Alcontrol (England) for contaminants testing. The test schedules included: Natural Moisture Content Determinations Particle Size Distribution (wet sieving and hydrometer) Atterberg Limits Bulk and Dry Density Test Chloride and Sulphate Content Determination Organic Matter Content Determination Unconfined Compression Test on rock cores Contamination Testing: As, Cd, Cr, Cu, Ni, Zn, Pb, Hg, Se, B, hex Chromium, total cyanide, free cyanide, total sulphate, sulphide, total sulphur, ph, speciated (16), PAHs, Phenols. Thiocyanate, TPH (Total Petroleum Hydrocarbons) The soil and rock tests and the relevant standards for performing the tests are presented in Table 3-6. of scheduled and completed laboratory tests is presented in Appendix E. The list Table 3-6 Standards for laboratory tests Test Standard Moisture content BS1377: Part 2. Liquid Limit (LL) and Plastic Limit (PL) BS 1377: Part 2, Clauses 4.3 and 5.3 Particle size distribution BS 1377: Part 2. Bulk Density Determination BS1377:Part 2 Loss on Ignition BS 1377: Part 3: 199 clause 4, test 3 Total sulphate content determination test BS 1377: Part 3: 199, test 5 OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 13 of 52

14 Test Water soluble chloride content determination test Uniaxial Rock Compressive Strength & Density of rock Contamination Testing Standard BS1377: Part 3: 199, test 7.2 ISRM suggested Methods for Rock Characterisation, Testing and Monitoring Standard Methods for Determining the Uniaxial Compressive Strength and Deformability of Rock Materials Methods and standards are given in Appendix F A summary of the laboratory test results is presented in Table 3-7 and Table 3-7 below. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 14 of 52

15 Table 3-7 Summary of Laboratory Testing Results on clayey material Bulk Total TP/BH No. Depth (m) Stratum Moisture Content (%) Loss on Ignition Unit Weight Atterberg Limits PSD (%) Sulphate Content Chloride Content (%) (Mg/cm 3 ) (%) Liquid Limit LL Plastic Limit PL Plasticity Index PI Gravel Sand Silt Clay TP Clay (Fill Material) TP C to HWB TP Gravel (Fill Material) TP H to MWB OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 15 of 52

16 Table 3-8 Summary of Laboratory Testing Results on Rock Cores TP/BH No. Stratum Depth (m) Unconfined Compressive Strength / MPa (N/mm 2 ) BH 1 SWB BH 1 SWB BH 1 SWB BH 1 MWB OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 16 of 52

17 Results and ground conditions 4.1 Identified soil profile The depth and thickness of the various strata observed in the Trial Pits and Corehole are shown in the logs and are summarised in Table 4-1. Table 4-1 Summary of strata encountered in metres TP / BH Strata No. TP 1 TP 2 TP 3 TP 4 BH 1 Topsoil / Fill Material (gravelly Clay)..6 (Gravel)..9 (Silty & Clay)..8 (Gravel and Clay) (Clay) (clayey Gravel & Cobbles) C to HWB M WB SWB (HWB) (CWB) The following definitions were considered for weathered basalts: Residual Soil: No recognisable rock texture. Surface layer contains humus and plant roots. Completely Weathered (CW) basalt: Rock completely decomposed by weathering in place but texture still recognisable. Can be excavated by hand. Highly Weathered (HW) basalt: Rock so weakened by weathering that fairly large pieces can be broken and crumbled in the hands. Sometimes recovered as core in careful rotary drilling. Moderately Weathered (MW) basalt: Considerable weathered throughout. Possessing some strength large pieces cannot be broken by hand, reasonable core recovery. Often limonite stained. Difficult to rip. OPG 1657 CEB Geotechnical Investigations at Fort Victoria Page 17 of 52

18 Slightly Weathered (SW) basalt: Distinctly weathered through much of the rock fabric with slight limonite staining. Strength approaches that of the fresh rock. Requires explosive for excavation. Highly permeable open joints. The following sections summarise the descriptions for each of the encountered strata Topsoil and Fill Material Topsoil was observed from the ground level to a maximum depth of.6m bgl. The Topsoil were represented by compacted Clay, Silt and Gravel. Fill Material was encountered on all Trial Pits and the Corehole generally as from the surface or below the Topsoil to an average depth of 1.m. It is likely that the Fill Material has been placed all over the site. For the corehole, the depth of the Fill Material was difficult to ascertain and it is presumed to extend to 6.m bgl. The spatial distribution of the suspected 6m Fill Material identified at BH 1 could not be defined due to restricted mobility on site. The trial pits and plate load tests trenches did not provide further evidence of the 6m thick Fill. It is possible that this thickness of Fill Material is localised or sporadically spread across the northern portion of the proposed tank outline. Two excavations done in close proximity of the borehole proved Fill Material up to 1.15m depth. The encountered Fill Material was described as: Soft to firm dark brown to reddish brown very gravelly high plasticity Clay / Silt with frequent fragments of glasses and plastics. In the corehole the Clay Fill is limited to the upper 2.25m. Loose sub-angular medium to coarse Gravel and Cobbles of strong light grey Slightly Weathered Basalt. 2No. SPT tests were carried out on the clayey fill material and the measured of SPT N-values of 1 and 11 (Figure 4.1). 1No. SPT tests performed on Gravel and Cobbles (fill material) reported refusal Clayey Weathered Basalts Completely and Completely to Highly Weathered Basalts were encountered on all exploratory holes except on TP2. This strata was intercepted across the site from a depth of.8m to 13.5m bgl with an average thickness of 2.m. The strata were generally described as firm to stiff reddish brown to dark brown high plasticity Clay. 2No. SPT tests were carried out on the Completely to Highly Weathered Basalts and the measured SPT N- values were 11 and 16 (Figure 4.1). OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 18 of 52

19 4.1.3 Rock Weathered Basalt Highly Weathered Basalt was retrieved at trial pit TP 2 between.6 and 1.9m. This layer was logged as moderately weak orangish brownish grey with black discolorations at joints highly vesicular with frequent amygdales. The joints are infilled with yellowish brown medium plasticity Clay. Moderately Weathered Basalt (MWB) was encountered at BH 1 at alternating depths between 13.53m to 2.m bgl. The average thickness of the stratum is 2.m and was described as weak to moderately strong grey with black and yellow mottles vesicular with frequent amygdales very closely jointed. RQD values for the MWB generally varies between % and 16 (Figure 4.2). Unconfined Compressive Strength (UCS) test carried out on a Moderately Weathered core returned a value of 3.6MPa. Slightly Weathered (SWB) was encountered between 14.33m to 17.64m and was generally described as strong to moderately grey vesicular closely to medium jointed. RQD values for the MWB generally varies between 34% and 61 (Figure 4.2). Unconfined Compressive Strength (UCS) test carried out on the strata returned values varying between 18MPa and 54MPa. 4.2 Groundwater Groundwater was encountered only at corehole BH 1 at3.5m bgl measured on 23 rd February Dynamic Cone Penetration Test Results A summary of the DCPT results is presented in Table 4-2. Table 4-2 Summary of DCPT Results TP No. DCPT No. Depth (m) Stratum CBR TP 1 1 Ground Fill Material 1 level Clay 2 1. C to HWB 2 TP 2 1 Ground level Fill Material Gravel HWB 21 OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 19 of 52

20 4.4 Plate Load Test Results A summary of the Plate Load Test results is presented in Table 4-3. The detailed results are presented in Appendix D-2. Table 4-3 PLT Results Summary TP No. PTL No. Depth (m) Stratum Maximum Load (kn) Maximum Bearing Pressure (kpa) Settlement (mm) TP 1 PLT 1 Ground level Fill Material very gravelly sandy Silt TP 2 PLT 2 Ground level Fill Material silty Gravel PLT 2 1. CWB Clay Chemical Environment The following tests were carried out on soil samples from the trial pits: Chloride and Sulphate Content Determination Organic Matter Content Determination Contamination Testing: As, Cd, Cr, Cu, Ni, Zn, Pb, Hg, Se, B, hex Chromium, total cyanide, free cyanide, total sulphate, sulphide, total sulphur, ph, speciated (16), PAHs, Phenols. Thiocyanate, TPH (Total Petroleum Hydrocarbons). Selected results are summarised in Table 4-4 and Table 4-5; the complete results are provided as Appendix F. Guidelines for soils for some of the contaminants for residential and commercial or industrial land use as per the documents from the Environment Agency UK and the Canadian Council of Ministers of the Environment are also presented in Table 4-4 (Refs. 11 and 12). OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 2 of 52

21 Table 4-4 Soil Chemical Tests Summary Parameter Units Limit of Detection (LOD) Soil Results Range Soil guideline value (residential) mg/kg Soil guideline value (commercial) mg/kg Chloride % < Sulphate % < Organic Matter % < Arsenic, As mg/kg <.6 < Cadmium, Cd mg/kg <.2 < Chromium, Cr mg/kg < Copper, Cu mg/kg < Nickel, Ni mg/kg < ,8 Zinc, Zn mg/kg < Lead, Pb mg/kg < Mercury, Hg mg/kg <.14 < Selenium, Se mg/kg <1 < , Boron, B mg/kg < Hexavalent Chromium mg/kg <.6 < Total Cyanide mg/kg <1 <1 Free Cyanide mg/kg <1 <1.9 8 Total Sulphate mg/kg < Sulphide mg/kg <15 <15 Total Sulphur % <.2 < ph ph units Speciated (16), PAHs μg/kg <118 < Phenols (Total detected mg/kg <.35 <.35 monohydric) Thiocyanate mg/kg <1 < TPH (Total Petroleum mg/kg <1 < Hydrocarbons) Phenols mg/kg <.1 < OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 21 of 52

22 Cresols mg/kg <.1 <.1 Xylenols mg/kg <.15 < Table 4-5 Water Chemical Tests Summary Limit of Parameter Units Detection Water Results (LOD) Arsenic, As µg/l < Cadmium, Cd µg/l <.1 <.1 Chromium, Cr µg/l < Copper, Cu µg/l < Nickel, Ni µg/l < Zinc, Zn µg/l < Lead, Pb µg/l < Mercury, Hg µg/l <.1 <.1 Selenium, Se µg/l < Boron, B µg/l < Hexavalent Chromium mg/l <.3 <.3 Total Cyanide mg/l <.5 <.5 Free Cyanide mg/l <.5 <.5 Sulphate mg/l < Total (16), PAHs μg/l < Phenols (Total detected monohydric) mg/l <.16 <.16 TPH (Total Petroleum Hydrocarbons) μg/l <1 32 Phenols mg/l <.2 <.2 Cresols mg/l <.6.6 OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 22 of 52

23 Geotechnical engineering assessment This Chapter presents geotechnical evaluation and recommendations for the proposed development based on the interpreted ground conditions. As stated in Section 1.1, the proposed development consists of a 6,5m 3 tank with a diameter of 24m for heavy oil storage. A full tank with its combined load is expected to exert of pressure of 145 kpa. This pressure was estimated by assuming a 14m high tank storing fuel oil with a density of 1kN/m 3. The value of the fuel density was provided by the Client. The geotechnical issues discussed are: design soil profile and parameters and discussion on foundation solutions. Shallow or deep foundations may in principle be adequate to support the proposed development under assessment. Engineering Fill has to be used for the case of shallow foundation due to the presence of Fill Material. 5.1 Identified Soil Profile The profile at the site, in order of vertical sequence, consists of i) 1m of Fill Material, ii) 12.5m of Clay (Completely to Highly Weathered Basalt), and iii) Moderately to Slightly Weathered Basalts. Geological profiles across the corehole and Trial Pits are presented in Appendix C-5. Groundwater prevailed as from a depth of 3.5m. The presumed thickness of the Fill Material encountered in the corehole is 6m. If this thickness of Fill Material is localised, it is recommended that the fill material is replaced by engineered fill, however for the case for which the distribution is relatively widespread, the following scenario will be assessed i) i) 6m of Fill Material, ii) 7.5m of Clay (Completely to Highly Weathered Basalt), and iii) Moderately to Slightly Weathered Basalts. The following sections describe the geotechnical properties associated with the encountered strata. Fill Material should be avoided as founding stratum or for engineering purposes as far as possible Properties of Fill Material The clayey silty Gravel was generally described as loose and the following properties can be considered for analysis: Soil unit weight of 18kN/m 3. SPT N values for the clayey Gravel varied between 1 and 11 (Figure 4.1). Assuming SPT N Value of 1, an angle of shearing resistance of 29 o can be used for analysis (Ref. 4). Relative Density 2%-4% OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 23 of 52

24 5.1.2 Clayey Weathered Basalts The clayey weathered basalt layer is composed of firm high plasticity silty Clay. The following properties are suggested for geotechnical analysis based on the laboratory test results and correlations: Soil Unit Weight of 15kN/m 3. Average Natural moisture contents of 26%. Atterberg Limits indicate the stratum to be silt/clay of high plasticity with average Plasticity Index of 3 (Figure 5.1). The variation of the moisture content and the liquid and plastic limits are presented in Figure 5.2. The representative SPT blow count (N) is 16 (Figure 4.1). Based on the SPT N correlation to undrained shear strength (Su) (Ref. 7), Plasticity Index (PI) of 42 and f1 value of 4.5 the estimated Su value would be 72kPa. Typical values for firm clay material are between 4kPa and 75kPa. An undrained shear strength (Su) of 65kPa will be adopted for analysis. mv can be determined using Stroud s correlation (Ref. 8) mv= 1 / f2n; where f2 can be defined based on PI as.45, and SPT = 16. Thus mv for the material is in the order of.13m 2 /MN corresponding to a medium compressibility material. Sulphate Content of the soil is.3% and average Chloride Content is.4% Moderately and Slightly Weathered Basalt The following properties can be considered representative of the M to SWB basalt rock: Bulk unit weight of 22kN/m 3. M to SWB rock was described as moderately strong to strong; UCS values corresponding to this description varies between 12.5MPa and 5MPa. Unconfined Compression tests on rock cores at depths varying between 14.83m and 18.38m gave UCS values varying between 3.6MPa and 53.5MPa. Rock Quality Designation (RQD) values for rock encountered at shallow depths (between 13.55m and 2.m) vary between and 61 indicating rock of very poor to fair quality rock (Figures 4.2 and 4.3) Engineering Fill The following properties for the granular engineering fill to be placed on site are suggested for analysis: Achieved soil unit weight of 2kN/m 3. For the granular fill (assumed as a dense gravel), a value of SPT N of 3 can be considered. A conservative an angle of shearing resistance of 32 o can be used for design. Relative Density 4%-6% OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 24 of 52

25 5.2 Foundation options For economic and practical reasons, shallow foundations are the conventional solution for founding structures. Deep foundations or alternative solutions (e.g. ground improvement) are implemented for low bearing capacity or high compressibility strata, subjected to loadings that can result on ultimate or serviceability performance limitations. The selection of the foundation solution will be controlled by the loads imposed and the response of the ground profile. The proposed development includes a 14m high heavy fuel tank with a stress magnitude of 145kPa. It is recommended that the Fill Material is excavated and replaced by Engineering Fill. For the purpose of analysis it is assumed that the 2m of the on-site materials are to be replaced by Engineering Fill. Therefore the Engineering Fill may act as founding layer. The following analyses are focused on evaluating the bearing capacity and related settlements for the proposed tank at a foundation depth of.6m bgl for a 24m circular raft. Two (2No) profile scenarios are analysed to verify the shallow foundation behaviour. This will provide a reliable indication of the potential bearing capacity and settlement threshold of the prevailing stratum. The bearing capacities are computed assuming no eccentric or inclined loading and without considering sloping ground. A pile foundation solution shall be implemented in the case that the settlement or bearing capacity for shallow foundation solutions are inadequate. Piles may be founded on the Moderately to Slightly Weathered encountered generally at 14.5m bgl. 5.3 Bearing capacity and settlement for Engineering Fill on natural strata (Scenario 1) In this case a layer of 2.m thick dense granular Engineering Fill is underlain by a 12.5m thick of clayey weathered basalt (Plate 1). OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 25 of 52

26 GL Scenario 1 Granular Engineering Fill SPT N 3 ; Ф 32 2.m 3.5m Firm Clay SPT N 16 ; Su 65kPa 12.5m Strong to moderately strong Moderately to Slightly Weathered Basalt Plate 1: Engineering Fill over natural strata Bearing capacity was computed using the two-layered profile (medium dense Gravel underlain by firm Clay) using solutions from Meyerhof and Hanna (1978) and Hanna and Meyerhof (198) for the condition of a strong drained layer overlying a weak undrained layer. For the Engineering Fill, an SPT of 3 for an angle of shearing resistance of 32º was applied. As for the Firm Clay an SPT of 16 for an undrained shear strength of 65kPa was adopted. The settlements for both layers were combined and were calculated by using the Burland and Burbridge (Ref. 5) for the Gravel and for the Clay a compressibility of.13m 2 /MN. A bearing capacity of 148 kpa was estimated with settlements in the order of 14mm for a factor of safety of 2.8. Skempton and MacDonald (Ref. 4) concluded that for a limiting angle of distortion of 1 in 5, the limiting maximum differential settlement is about 25mm, the limiting total settlement is 4mm for isolated foundations and 4-65mm for raft foundations. 5.4 Bearing capacity and settlement for Engineering Fill on Fill Material (Scenario 2) This scenario is envisaged if the thickness of Fill Material is relatively large as encountered at BH 1, where it extended to 6m depths, and also if it is widely distributed. It will not be practical to excavate all the Fill Material. Therefore, 2.m thick Engineering Fill over 4.m of clayey Gravel (Fill Material) has been analysed. OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 26 of 52

27 GL Scenario 2 Granular Engineering Fill SPT N 3 ; Ф 32 2.m Fill Material SPT N 1 ; Ф m 4.m Firm Clay SPT N 16 ; Su 65kPa 7.5m Strong to moderately strong Moderately to Slightly Weathered Basalt Plate 2: Engineering Fill over Fill Material Bearing capacity was computed using the two-layered profile (medium dense Gravel underlain by loose Gravel and firm Clay) using solutions from Meyerhof and Hanna (1978) and Hanna and Meyerhof (198) for the condition of a strong drained layer overlying a weak drained layer. The geotechnical parameters considered for the analysis is depicted on Plate 2 above. For the Engineering Fill, an SPT of 3 for an angle of shearing resistance of 32º was adopted. A for the loose clayey Gravel an SPT of 1 for an angle of shearing of 29º were computed. An undrained shear strength of 65kPa and a compressibility of.13m 2 /MN was used for the underlying firm Clay. The settlements for the three upper layers were combined. A bearing capacity of 149 kpa was estimated with settlements in the order of 13mm for a factor of safety of 2.8. The above analysis for both scenarios estimated settlements in the order of 14mm and 13mm. According to Skempton and MacDonald (Ref. 4) these magnitudes of settlement are considered to be excessive (higher than 4 to 65mm for raft foundations). Differential settlement as a result of heterogeneity of the underlying strata (clay and gravel) amounts to 1mm which is within the acceptable limit of 25mm. However, Klepikov (1989) suggests that for a large (53.6m diameter; 18.3m high) circular steel tanks the allowable settlement is 18mm while for a smaller circular tank (9m diameter; 8m high) it is 11mm. OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 27 of 52

28 Ground improvement can be performed to improve the existing sub surface ground via mechanical methods. These methods can include dynamic compaction, stone columns and soil cement columns. This would increase bearing capacity and reduce settlements. If shallow foundations solutions are implemented, the tank is expected to sink uniformly due to the uniformly circular distributed load. The sinking of the tank is due to serviceability load and according to Klepikov (1989) the magnitudes of settlement (maximum of 14mm) may be considered as acceptable. Settlements may be curtailed by reducing the designed height of the tank. The settlements can be mitigated by using piles as foundation solution by transferring the load to the competent stratum at a depth of 14.m. Piles will also significantly increase the allowable bearing capacity. Pile foundations are expected to cost more than shallow foundations. 5.5 Deep foundations Selection of type of pile depend on stress applied construction constraints and availability in Mauritius; based on these criteria, driven precast piles may be implemented. Although, if the scrap metals are cleared, there is no foreseeable constraints on the site which can hamper mobility. Other types of piles may be suggested by the piling suppliers. Vibration associated with pilling works should be regulated so that the surrounding infrastructures are not deleteriously impacted. Precast piles can provide an economical solution especially in deeper soil profiles. The main considerations for driven pre-cast piles are: i) small sections available could be a limitation if large loads are expected; ii) faster installation results on reduced time on site (Ref. 7). Other consideration is the considerable noise and vibration associated with the driving of the precast pile. Inter-bedded hard layers were not observed on the site, in such a situation, rock shoes may be used to protect the concrete with a hardened steel point. Although the founding strata is identified previous to pile installation, the final pile length is determined on site, where the piles are driven to a predetermined displacement set corresponding to a specific number of driving hammer blows. The depth to the bedrock is 14.m based on observation from corehole BH1. For precast concrete driven piles, the exact area of contact with rock is not known. The bearing capacity will depend on the type and nature of the rock and the depth of penetration of the pile into the rock. Estimation of the allowable bearing capacity of such piles by analytical method cannot be made. Load capacity of these type of piles should be estimated based on local experience and driving resistance supported by pile load tests. Table 5-1 summarises typical Precast pile characteristics as presented by Byrne et al. (Ref. 7). Table 5-1 Cast-in-situ piles indicative characteristics Diameter, mm 25mm 3mm 35mm OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 28 of 52

29 Square Square Square Typical working load, kn* Max depth, m Unlimited Minimum pile spacing c/c, m *Note: The typical working loads are related to the structural characteristics of the piles and not to the soil conditions the latter is given below. If the rock is strong at its surface, the carrying capacity of the piles is governed by the strength of the pile as structural element Buried Concrete An Aggressive Chemical Environment for Concrete (ACEC) site classification has been carried out based on Water Soluble Sulphate content (2:1 water-soil extract) and ph tests on similar marine deposit samples. The evaluation is carried out following the UK Building Research Establishment (BRE) Special Digest SD1, Concrete in Aggressive Ground 25 (Ref. 8). Typical results for Water Soluble Sulphate content (2:1 water-soil extract) on the clayey weathered basalts vary between.5% and.7%; Water-soluble Chloride Content varied between.3% and.7%. Based on these results, a Design Sulphate Class DS-1 and ACEC Class AC-1, for mobile groundwater, can be used for buried concrete structures. Exposure of concrete to potentially brackish (~1 mg/l chloride) or similarly saline groundwater is, however, beyond the scope of this recommendation Conclusions Based on the analyses presented above, the recommended bearing capacity for the 6,5m 3 tank is in the order of 145kPa with maximum settlements of 14mm for a factor of safety of 2.8. If shallow foundations solutions are implemented, the tank is expected to sink uniformly. The sinking of the tank is due to serviceability load and according to Klepikov (1989) the magnitudes of settlement (maximum of 14mm) may be considered as acceptable The settlements can be neutralised by using piles as foundation solution by transferring the load to the competent stratum at a depth of 14.m OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 29 of 52

30 References 1. Ile Maurice Carte Geologique et Hydrogeologique (1996), Republique de Maurice. 2. Proag, V. (1995), The geology and water resources of Mauritius, analysis, Mahatma Gandhi Institute. 3. Directorate of overseas surveys (UK) (1962), Soil Map of Mauritius, Public Works and Survey Department, Port Louis Mauritius. 4. British Standards (1999), BS 593, Code of practice for site investigations. 5. British Standards (199), BS 1377, Methods of tests for soils for Civil Engineering purposes. 6. Transport and Road Research Laboratory (1986), Operation instructions for the TRRL dynamic cone penetrometer, TRRL Information Note. UK. 7. Tomlinson, Foundation Design and Construction, Seventh Edition, Pearson Education Limited, Stroud, M A (1989), The Standard Penetration Test its application and interpretation, Penetration Testing in the UK, Thomas Telford 9. Burland, JB and Burbidge, MC (1985), Settlement of foundations on sand and gravel. Proc Instn Civ Engrs, part Prakash S., Sharma H. (199), Pile Foundations in Engineering Practice, John Wiley and Sons Inc. 11. Environment Agency (29), Technical Note Science Project, Environment Agency UK. 12. Canadian Soil Quality Guidelines for the protection of Environmental and Human Health (27), Canadian Soil Quality Guidelines, Table 1, Canadian Council of Ministers of the Environment. OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 3 of 52

31 Figures North Site Figure 2-1 General location of the site OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 31 of 52

32 North Site Figure 2-2 Site Location OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 32 of 52

33 Site Figure 2-3 Aerial Map of site and location of Trial Pits and Coreholes OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 33 of 52

34 Site North Figure 2-4 Location of the site on geological map OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 34 of 52

35 Site Figure 2-5 Location of the site on Soil Map OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 35 of 52

36 SPT N Values Depth (m) BH 1 Date: March 216 Job: OPG 1657 CEB Figure: 4.1 Figure 2-6 Standard Penetration Test N Value Variation with Depth As per Stratum OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 36 of 52

37 RQD, % BH Depth (m) BH 1 Rock Quality Designation, RQD % Date: March 216 Job: OPG 1657 CEB Figure: 4.1 Figure 2-7 Rock Quality Designation Variation with Depth OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 37 of 52

38 7 Low Plasticity Intermediate Plasticity High Plasticity Very High Plasticity Extremely High Plasticity 65 CV CE 6 55 CH ME 5 45 CI Plasticity Index (%) CL MV 25 MH MI 5 ML A Line Fill Material C to HWB Liquid Limit (%) A-Line Plasticity Chart Figure : 5.1 Figure 2-8 A Line Plasticity Chart OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 38 of 52

39 Appendix A Site Layout OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 39 of 52

40

41 Appendix B Photographs of Site Works Photo B.1 OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 4 of 52

42 Photo B.2 OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 41 of 52

43 Photo B.3 OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 42 of 52

44 Appendix C Exploratory Hole Logs OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 43 of 52

45 Appendix C-1 Corehole Logs OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 44 of 52

46 BOREHOLE No. : BH 1 SITE : Bain des Dames, les Saline Drilling Rig : ABYSS 75 National Grid Coordinates Start Date : 2/2/216 Casing Diameter : 88mm N : End Date : 3/2/216 Borehole Diameter : 76mm E : Final Depth : 2.m Core Diameter : 52mm Ground Level : 3.m amsl Water Depth : 3.5m on 2/2/216 Description of Strata Legend Scale (m) Elevation/Depth Sample / In Situ Test N Value Recovery (cm) Core Run TCR (%) SCR (%) RQD (%) FI Casing Depth Drilling Dark brown very gravelly high plasticity silty CLAY. FILL MATERIAL? Soft to firm reddish brown gravelly high plasticity silty CLAY. FILL MATERIAL? 1..6 () SPTLS (1) Loose sub-angular fine to medium clayey GRAVEL of very weak reddish brown Highly to Completely Weathered Basalt with rare cobbles between m. Clay is brown high plasticity FILL MATERIAL? Loose sub angular fine to medium GRAVEL & COBBLES of strong light grey vesicular Slightly Weathered Basalt. FILL MATERIAL? U2(R) DC - 76mm Loose sub angular fine to medium dense clayey GRAVEL of very weak dark greyish brown Highly Weathered Basalt. FILL MATERIAL? Firm dark brown with mottles high plasticity silty CLAY with cobbles between m. COMPLETELY WEATHERED BASALT. Firm reddish brown with orange & cream mottles high plasticity silty CLAY. COMPLETELY WEATHERED BASALT SPTLS SPTLS (11) > NW 6. DC - 52mm 9. SPTLS (16) Continued next sheet 1. Legend : U : Undisturbed Tube Sample C : (SPT) Solid Cone DC : Dry Coring 1. Logged by : ZJ D : Disturbed Sample S : (SPT) Split Spoon WD : Water Drilling Drillers : MP RU : Refusal at Jacking of U Sampler R : (SPT) Refusal NI : Non Intact M : Mazier Sample Checked by : Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 1 of 2

47 BOREHOLE No. : BH 1 SITE : Bain des Dames, les Saline Drilling Rig : ABYSS 75 National Grid Coordinates Start Date : 2/2/216 Casing Diameter : 88mm N : End Date : 3/2/216 Borehole Diameter : 76mm E : Final Depth : 2.m Core Diameter : 52mm Ground Level : 3.m amsl Water Depth : 3.5m on 2/2/216 Description of Strata Legend Scale (m) Elevation/Depth Sample / In Situ Test N Value Recovery (cm) Core Run TCR (%) SCR (%) RQD (%) FI Casing Depth Drilling Firm reddish brown with cream & black mottles high plasticity silty CLAY. COMPLETELY TO HIGHLY WEATHERED BASALT SPTLS (22) Weak to moderately weak creamish grey with black mottles at vesicles closel jointed MODERATELY WEATHERED BASALT. Joints are smooth WD - 52mm Strong to moderately strong light grey vesicular closely-medium jointed SLIGHTLY WEATHERED BASALT. Joints are planar smooth sub horizontal in-filled with cream clay Moderately weak to moderately strong grey with yellow & black mottles at vesicles with frequent amygdales very closely jointed MODERATELY WEATHERED BASALT. Joints are undulating rough sub horizontal in-filled with reddish brown clay End of Borehole at 2. m Legend : U : Undisturbed Tube Sample C : (SPT) Solid Cone DC : Dry Coring Logged by : ZJ D : Disturbed Sample S : (SPT) Split Spoon WD : Water Drilling Drillers : MP RU : Refusal at Jacking of U Sampler R : (SPT) Refusal NI : Non Intact M : Mazier Sample Checked by : Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 2 of 2

48 Appendix C-2 Photographs of Cores OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 45 of 52

49 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA BH1 Page 1 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB COREHOLE BH1 CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH:. 2.m DATE: 2/2/216 CORE RUN:..5m.5 1.m m m SPT 1 Depth: m Penetration: 15mm = mm = mm = mm = mm = 2 N Value = 1 Recovery = 4cm CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: 2. 4.m DATE: 2/2/216 CORE RUN: m m m m SPT 2 Depth: 3.5m Recovery = Refusal CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: 4. 6.m DATE: 2/2/216 CORE RUN: m m m m m SPT 3 Depth: m Penetration: 15mm = mm = mm = mm = mm = 2 N Value = 11 Recovery = 28cm Depth:. 6. metres

50 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA BH1 Page 2 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB COREHOLE BH1 CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: 6. 8.m DATE: 2/2/216 CORE RUN: m m m SPT 4 Depth: m Penetration: 15mm = mm = mm = mm = 51 N Value = 71 Recovery = 34cm CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: 8. 1.m DATE: 2/2/216 CORE RUN: m m SPT 5 Depth: m Penetration: 15mm = mm = mm = mm = mm = 3 N Value = 16 Recovery = 28cm CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: m DATE: 3/2/216 CORE RUN: m m Depth: metres

51 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA BH1 Page 3 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB COREHOLE BH1 CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: m DATE: 3/2/216 CORE RUN: m m SPT 6 Depth: m Penetration: 15mm = mm = mm = mm = mm = 4 N Value = 22 Recovery = 33cm CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: m DATE: 3/2/216 CORE RUN: m m CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: m DATE: 3/2/216 CORE RUN: m m Depth: metres

52 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA BH1 Page 4 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB COREHOLE BH1 CLIENT: CENTRAL ELECTRICITY BOARD PROJECT: GEOTECHNICAL INVESTIGATION AT FORT VICTORIA SITE: PORT LOUIS FORT VICTORIA C/HOLE: BH1 DEPTH: m DATE: 3/2/216 CORE RUN: m Depth: metres End of Corehole at 2. metres

53 Appendix C-3 Trial Pit Logs OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 46 of 52

54 TRIALPIT No. : TP 1 SITE : Bain des Dames, les Saline Method : Mechanically Excavated National Grid Coordinates Start Date : 4/2/216 N : End Date : 4/2/216 E : Final Depth : 2.55m Ground Level : 3.m amsl Water Depth : Not Encountered Description of strata Legend Scale (m) Elevation/Depth Sample Type Depth of Water Strikes Insitu density/ Percolation/ Pocket Pen. kpa Firm to stiff dark brown medium plasticity CLAY with debris such as plastic and glass bottles, concrete and roots. FILL MATERIAL. SB LB Firm to stiff reddish brown with orange and cream mottles gravelly high plasticity CLAY. Gravels are sub rounded to sub angular medium to coarse moderately strong light grey of Moderately Weathered Basalt. COMPLETELY TO HIGHLY WEATHERED BASALT SB LB End of Trialpit at 2.55 m Remarks : TP.4m above G.L Notation P : Percolation Test DT : In Situ Density Test PP : Pocket Penetrometer SB : Small Bulk LB : Large Bulk Logged by : Checked by : ZJ Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 1 of 1

55 TRIALPIT No. : TP 2 SITE : Bain des Dames, les Saline Method : Mechnicaly Excavated National Grid Coordinates Start Date : 4/2/216 N : End Date : 4/2/216 E : Final Depth : 1.9m Ground Level : 3.m amsl Water Depth : Not Encountered Description of strata Legend Scale (m) Elevation/Depth Sample Type Depth of Water Strikes Insitu density/ Percolation/ Pocket Pen. kpa Dense sub rounded to sub angular clayey GRAVELS of moderately strong grey with black discoloration at joints very vesicular of Moderately Weathered Basalts with concrete debris, iron bars and plastic materials. FILL MATERIAL SB LB.6 Moderately weak orangish brownish grey with black, yellow and cream discolorations at joints. Very vesicular with many amygdales HIGHLY WEATHERED BASALT in filled with yellowish brown medium plasticity clay. 1. SB LB 1.9 End of Trialpit at 1.9 m 2. Remarks : Bucket Refusal at 1.9m Notation P : Percolation Test DT : In Situ Density Test PP : Pocket Penetrometer SB : Small Bulk LB : Large Bulk Logged by : Checked by : ZJ Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 1 of 1

56 TRIALPIT No. : TP 3 SITE : Bain des Dames, les Saline Method : Mechanically Excavated National Grid Coordinates Start Date : 23/2/216 N : End Date : 23/2/216 E : Final Depth : 1.5m Ground Level : 3.m amsl Water Depth : Not Encountered Description of strata Legend Scale (m) Elevation/Depth Sample Type Depth of Water Strikes Insitu density/ Percolation/ Pocket Pen. kpa Soft light grey strong brown very gravelly sandy SILTY with frequent concrete blocks. TOPSOIL..3 Soft black very gravelly medium plasticity silty CLAY with various fragments of glasses, pipes. FILL MATERIAL. SB.9 Firm moist reddish brown high plasticity gravelly silty CLAY. COMPLETELY WEATHERED BASALT. 1. SB 1.5 End of Trialpit at 1.5 m 2. Remarks : Notation P : Percolation Test DT : In Situ Density Test PP : Pocket Penetrometer SB : Small Bulk LB : Large Bulk Logged by : Checked by : OB Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 1 of 1

57 TRIALPIT No. : TP 4 SITE : Bain des Dames, les Saline Method : Mechanically Excavated National Grid Coordinates Start Date : 23/2/216 N : End Date : 23/2/216 E : Final Depth : 1.1m Ground Level : 3.m amsl Water Depth : Not Encountered. Description of strata Legend Scale (m) Elevation/Depth Sample Type Depth of Water Strikes Insitu density/ Percolation/ Pocket Pen. kpa Sub angular coarse silty GRAVEL of strong grey Moderately to Slightly Weathered Basalt. TOPSOIL..15 Firm dark brown very gravelly silty clay with numerous fragments of glasses. FILL MATERIAL. SB.8 SB Stiff reddish brown with black mottles high plasticity CLAY. COMPLETELY TO HIGHLY WEATHERED BASALT End of Trialpit at 1.1 m 2. Remarks : Notation P : Percolation Test DT : In Situ Density Test PP : Pocket Penetrometer SB : Small Bulk LB : Large Bulk Logged by : Checked by : OB Contract No : OPG 1657 CEB Project : Geotechnical Investigation at Fort Victoria Sheet : 1 of 1

58 Appendix C-4 Photographs of Trial Pits OPG 1657 CEB Report on Site Investigation at Fort Victoria Page 47 of 52

59 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 1 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB TP 1

60 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 2 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

61 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 3 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

62 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 4 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

63 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 5 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

64 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 6 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

65 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 1 Page 7 of 7 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB Final Depth at 2.55metres

66 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 2 Page 1 of 5 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB TP 2

67 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 2 Page 2 of 5 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

68 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 2 Page 3 of 5 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

69 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 2 Page 4 of 5 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

70 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 2 Page 5 of 5 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB Final Depth at 1.9 metres

71 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 3 Page 1 of 2 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB TP 3

72 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 3 Page 2 of 2 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB Final Depth at 1.5 metres

73 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 4 Page 1 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB TP 4

74 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 4 Page 2 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

75 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 4 Page 3 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB

76 GEOTECHNICAL INVESTIGATION AT PORT LOUIS FORT VICTORIA TP 4 Page 4 of 4 CLIENT: CENTRAL ELECTRICITY BOARD CONTRACT No.: OPG 1657 CEB Final Depth at 1.1 metres