Soil Investigations Wind Farm Zones

Transcription

1 Date January Status Final Soil Investigations Wind Farm Zones Section IV-d Scope of Work geotechnical Survey Borssele Wind Farm Zone WIND FARM SITE I & II

2 Colophon Project name Project number Version File name Project manager Contact Site Studies Wind Farm Zone Borssele F _SDB_Section IV-d Scope of Work Geotechnical _Rev1_F Ruud de Bruijne Annex(es) Author Reviewed Approved R. de Wolff M. Timmerman R. de Bruijne Page 2 of 19

3 Contents 1 Introduction & Background Scope document Background Objective geotechnical survey Site description Investigation Areas (IA s) Planning of the investigations Available information Scope of Work General scope survey works Preparation Execution of Boreholes Data processing and reporting for boreholes Execution of Seabed PCPT Data processing and reporting for seabed PCPT Create a geological model of the site OFFSHORE REPRESENTATION SCHEDULE OF KEY DATES Page 3 of 19

4 1 Introduction & Background 1.1 Scope document This document details the scope of the WORK as part of the SPECIFC AGREEMENT that CLIENT has awarded to CONTRACTOR for carrying out geotechnical investigations at WIND FARM SITE I & II. 1.2 Background The Ministry of Economic Affairs is responsible for the legislative framework for the development of offshore wind farms in the Netherlands. Within this framework (a) (concession) tender(s) for subsidy for construction and operation of (a) wind farm(s) will be organized under the SDE+ regulation. As part of the tender documentation, the participants will receive an information package in which detailed information on the offshore site is included. Detailed information on the soil conditions at the site will be part of this information package. 1.3 Objective geotechnical survey The objective of the geotechnical soil investigation is to improve the geological and geotechnical understanding of WIND FARM SITE I & II and to obtain geotechnical information on this location, which is suitable to progress the design and installation requirements for offshore wind farms, including, but not limited to foundations and cables. The Geotechnical Soil Investigation must provide relevant information about the soil to a depth below which possible existence of weak formations will not influence the safety or performance of the wind turbine and its support structure. The objective of the investigation (and laboratory testing program) is to: confirm the geological / geophysical model for the WIND FARM SITE I & II; determine the vertical and lateral variation in seabed conditions; provide the relevant geotechnical data for the design of the offshore WIND FARM SITE I & II, including, but not limited to foundations and cables. Update the geological desk study and provide a detailed geological model of the site. The geotechnical investigation of WIND FARM SITE I & II consisting of a combination of sampling with subsequent laboratory testing and in situ testing, should include, but not be limited to stiffness and damping parameters for all important layers: Description and index classification Strength parameters Deformation properties Permeability In-situ stress conditions The soil parameters provided shall cover the scope required for a detailed and complete wind turbine foundation design, including lateral extent of significant soil layers, and the lateral variation of soil properties in these layers. Page 4 of 19

5 The laboratory test program for determination of soil strength and deformation properties shall cover a set of different types of tests and a number of tests of each type, which will suffice to carry out a detailed foundation design. 1.4 Site description The proposed WFS is located in the Borssele WFZ (the most southern WFZ as presented in Figure 1). The Borssele WFZ is the first WFZ for which site investigations shall be executed. Figure 1 Designated Wind Farm Zones in the Netherlands The co-ordinates of the corners of the Borssele WFZ are given in Fout! Verwijzingsbron niet gevonden. (with reference to Figure 2): Page 5 of 19

6 Corner Geographical Co-ordinates (ETRS 89) UTM Coordinates (ETRS89 Zone 31) Latitude Longitude Easting Northing 1 51, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,30 Table 1 Coordinates of Borssele Wind Farm Zone The four different WFS s that are defined at the Borssele WFZ are shown in Figure 2. From this graphical representation it can be seen that the WFS s are separated by safety corridors of cables and pipelines that run through the site. Figure 2 The Borssele Wind Farm Zone and the designated Wind Farm Sites in the Borssele WFZ 1.5 Investigation Areas (IA s) It is the intention to obtain a separate set of data, reports and drawings for each WFS. The Investigation Area that shall be surveyed for WIND FARM SITE I & II is shown in Figure 3. Page 6 of 19

7 Borssele WFZ Figure 3 The Investigation area for WFS I & II The boundary points and the coordinates of these boundary points of each of the Wind Farm Sites (Investigation Zones) are presented in Appendix A. In paragraph 2.1 the number of Seabed PCPT s and Boreholes/PCPT s required is provided. The target coordinates and target depth of the Boreholes/PCPT s and the target coordinates of the Seabed PCPT s will be provided by Client at the date as specified in the Schedule of Key Dates. 1.6 Planning of the investigations The WORK shall be carried out in the period [ ]. Opmerking [MT1]: Specify the timing for carrying out the survey 1.7 Available information CLIENT has carried out desk studies on The Borssele WFZ. The following studies have been made available to CONTRACTOR: Geological desk study Morphological desk study Archaeological desk study UXO desk study Metocean study After contract signing Client will make available: (Preliminary) results of the Geophysical survey carried out for WFS I & II Page 7 of 19

8 2 Scope of Work 2.1 General scope survey works The activities that need to be carried out to obtain the information detailed in section 1.3 are the following: Obtaining / arranging all necessary permissions and / or notifications to perform the investigation (Including all permissions and fees necessary for access and safety arrangements to harbours and offshore positions). Obtain UXO clearance certificates for all borehole/pcpt and Seabed PCPT locations. Preparation of the geotechnical survey and providing plans that need to be provided (and approved) before the works can start. Carry out the survey for foundation design purposes - Carrying out [12] boreholes/pcpt - Carrying out [51] seabed PCPT Target coordinates and target depth of boreholes/pcpt and target coordinates of Seabed PCPT to be provided by Client at the date as specified in Schedule of Key Dates. Client may adjust quantities in accordance with the provisions in the Contract. Inform the client on the progress of the works. Laboratory testing on obtained soil samples Create a detailed geological model of the WIND FARM SITE Process the data obtained through the geotechnical survey and present all results in clear reports and drawings. 2.2 Preparation Scrutinise available information CONTRACTOR shall scrutinise the information that has been made available by CLIENT. Information that is relevant for carrying out the WORK shall be taken into account while preparing the WORK Preparations Permits Obtaining and arranging all necessary permissions and/or notifications to perform the survey (including all permissions and fees necessary for access and safety arrangements to harbours and offshore positions). Project Plans CONTRATOR shall prepare all required project plans as required by the CONTRACT. These documents include but are not limited to: Project Execution Plan (including applicable Method Statements and Risk Assessments; Project HSE Plan; Project Quality Plan; Emergency Response plan. Page 8 of 19

9 CONTRACTOR shall only commence the WORK when all project plans have been reviewed by by CLIENT and CLIENT has confirmed to have no further comments UXO risk assessment and measures There is a possibility of an increased risk regarding the presence of UXO s (unexploded ordnances) in the WIND FARM SITE. Information on this increased risk will be submitted in a UXO desk study that is carried out by CLIENT. CONTRACTOR shall carry out an UXO risk assessment for the proposed borehole and seabed PCPT locations and undertake any required additional measures in order to reduce the risk to as low as reasonably practical (ALARP). 2.3 Execution of Boreholes Mobilization Positioning Mobilization of the vessel to the site, complete with all necessary geotechnical drilling equipment and personnel. Boreholes should be positioned within a 5m radius of the target co-ordinates Executing boreholes The boring log, a detailed description of the soil types, and the in situ geotechnical properties determined for the boreholes shall be documented to characterise the strata. These shall be performed in accordance with Eurocode EN or CLIENT approved equivalent. The general requirements for the boreholes are as follows: 1. When the vessel is on station, the position of the vessel and the water depth shall be logged prior to commencing any investigation work at each of the locations. 2. The target depths for the boreholes will generally be somewhere between 50m and 80m, depending on the depths of the geological formations of interest at a particular location. The CLIENT OFFSHORE REPRESENTATIVE may request the depth of boring/testing to be terminated prematurely or extended beyond the target depth to a maximum depth of 80m, should it be determined by the CLIENT REPRESENTATIVE that this is appropriate. The boreholes should be progressed by a drilling and sampling technique approved by the CLIENT i.e. conventional offshore API drilling with downhole wireline sampling and piezocone penetration testing (PCPT). The sampling and PCPT requirements will depend on the material type encountered. The following regimes should be applied, unless otherwise agreed by the CLIENT OFFSHORE REPRESENTATIVE and the CONTRACTOR on site, or directly by the CLIENT OFFSHORE REPRESENTATIVE on site. The appropriate regime should begin immediately upon encountering a new layer. Within the granular deposits, the boreholes are to be advanced by alternating PCPT (up to 3m stroke) and push sampling (1m length Shelby tubes). Where the sample recovery is poor using the push sampler, a hammer sampler shall be used instead. Blow counts measured during hammer sampling shall be recorded and presented on the Borehole Logs. Page 9 of 19

10 Within the cohesive deposits, the boreholes are to be advanced by PCPT followed by two push samples (repeat cycle). Rotary coring (using a triple-tube core-barrel that provides 100m diameter cores) may be used instead of push sampling in suitable materials, in which case the PCPT and cores (1.5m length) shall be alternated. The spacing between samples and/or PCPT shall not exceed 1.0m Recovery of Samples and Laboratory Testing General Ideally, the following tasks should be carried out offshore on the vessel: Sample logging and photography; Selection and preservation of core sub-samples for onshore testing; Moisture content measurements; Pocket penetrometer tests (or torvanes if appropriate) on cohesive soil samples. All onshore laboratory testing shall be carried out at an approved geotechnical laboratory. All core logging and soil testing shall be carried out, where applicable, respectively to Eurocode EN :2007, BS 5930, and BS 1377 or CLIENT approved equivalent. Cyclic soil testing, if any, shall be carried out in accordance with the relevant ASTM standard (e.g. ASTM D & ASTM D 6528), where applicable. All test data shall be presented in ASCII format for easy manipulation, data transfer, and integration. The CONTRACTOR is to ship all recovered samples and cores to the onshore laboratory on a regular basis (to be discussed and agreed by the CLIENT). As a general guideline, the following types and quantity of tests will normally be required for the different material types expected. The actual testing programme shall be agreed between the CLIENT and CONTRACTOR, or as instructed by the CLIENT. Onboard the vessel, samples shall be stored in a temperature stable environment with no exposure to direct sunlight and in compliance with the standards as specified. In the onshore laboratory, samples shall be stored in a temperature and humidity controlled enclosure and in compliance with the standards as specified. The soil samples shall be stored onshore by the CONTRACTOR for a period of twelve (12) months following the soil samples receipt at the onshore laboratory during which time the CLIENT shall be granted free access to the same. The CONTRACTOR shall store the cores in containers so that they can be retrieved easily. Storage shall be in a temperature and humidity controlled environment to ensure the samples do not dry out or suffer any other damage and in compliance with the standards as specified. Following the minimum twelve (12) month storage period the CLIENT shall instruct the CONTRACTOR of one of the following: i) a further period of storage, ii) safe and legal disposal of all samples or iii) CLIENT collection of said samples. Options i) shall be at the cost to the CLIENT by way of VARIATION where such additional cost is incurred. For the avoidance of doubt the CONTRACT PRICE shall include for the safe and legal disposal of all samples regardless of the duration of storage. Page 10 of 19

11 A number of undisturbed samples will be reserved for further advanced testing including cyclic testing. Granular Soil Particle size analysis at approx. 2-4m interval (using either pipette or hydrometer for fines fraction, if appropriate); Maximum and minimum density at approximately 8m interval; Consolidated drained (CD) triaxial tests (approximately 3 no. per borehole) (on undisturbed samples where possible); Direct simple shear tests (approx. 3 no. per borehole); Ring shear tests (approx. 1-2 per borehole); Cohesive Soil Moisture content at 1.0m interval; Bulk density at 1.0m interval (included in triaxial tests but may be requested as an additional test); Particle density at approx 5m intervals; Atterberg limits (liquid and plastic limits) at approx. 2-3m interval; Unconsolidated undrained (UU) triaxial compression tests on undisturbed and remoulded samples at approximately 5m intervals; One dimensional consolidation (oedometer) tests (approximately 4 no. per borehole); Consolidated anisotropically undrained (CAU) (approximately 5-10 no. per borehole); Ring shear tests (approx. 1-2 per borehole). The anticipated cyclic testing programme for each of the soil layers/formations that are selected for cyclic behaviour assessment is as follows: Cyclic undrained direct simple shear tests (DSScy) - approx. 5 no. tests Anisotropically consolidated undrained cyclic triaxial tests (CAUcy) - approx. 5 no. tests As part of the cyclic testing programme, a number of additional static soil tests will be undertaken for each of the soil layers/formations as follows: Static undrained (or drained) direct simple shear tests including Gmax measurements (DSS) - 2 no. tests Anisotropically consolidated undrained (or drained) static triaxial compression tests (CAUc) - 2 no. tests Anisotropically consolidated undrained (or drained) static triaxial extension tests (CAUe) - 2 no. tests Constant rate of strain (CRS) consolidation tests including two unloading reloading loops - 2 no. tests Executing downhole wireline piezocone penetration tests (PCPT) The down-hole wireline PCPT system shall include a minimum 10 tonne thrust reaction and a cone tip capacity of 100 kn. The tests shall be carried out in full accordance with ISSMFE Reference Test Procedures, British Standard BS 1377:1990, ASTM D and Eurocode EN Page 11 of 19

12 2.3.6 Demobilization Upon completion of the survey demobilization of the vessel, equipment and personnel. 2.4 Data processing and reporting for boreholes After carrying out the borehole investigation, CONTRACTOR shall process the data that is gathered during the field work, carry out the laboratory tests according to the programme that is agreed with CLIENT and prepare a detailed report covering the total scope of work. The reporting requirements for the geotechnical borehole work are detailed below Daily & Weekly reporting The CONTRACTOR is to submit daily reports throughout the period of the fieldwork, providing full details of previous 24 hours work and results. Further, CONTRACTOR shall issue a weekly report providing insight in the progress of the WORK on a weekly basis. The minimum contents of the daily and weekly report is specified in Section VII of this CONTRACT Preliminary Field Borehole Logs and PCPT results Field report Final report The Contractor is to provide preliminary (field) borehole logs and PCPT results within 72 hours of completion of the borehole (these logs/results will be used to complete the onshore laboratory test schedule. A Field report shall be made available within one week of the completion of the fieldwork. This report shall include: A statement of the purpose of the investigation; Daily logs; A description of the work carried out, including reference to specification and standards adopted and any deviations from them; Exact locations of all boreholes, co-ordinates shall be with respect to ERTS89 datum, given in degrees and decimal-minutes format as well as in meters using a UTM ETRS89 Zone as well as in meters using a UTM ETRS89 Zone 31 projection.31 projection. Drawings (AutoCAD format or similar) showing the locations of the boreholes undertaken; Preliminary (field) borehole logs Plots of the following final (quality assured) PCPT results: o Measured cone resistance o Measured sleeve friction o Measured pore water pressure o Friction Ratio o Net cone resistance o Interpreted relative density (granular materials) o Interpreted undrained shear strength (cohesive materials) CONTRACTOR shall submit a Final Report no later than four (4) weeks following the completion of fieldwork. This report should include: Page 12 of 19

13 A statement of the purpose of the investigation; A description of the work carried out, including reference to specification and standards adopted and any deviations from them; Exact locations of all boreholes, co-ordinates shall be with respect to ETRS89 datum, given in degrees, minutes and decimal minutes format as well as in meters using a UTM ETRS89 Zone 31 projection. Drawings (AutoCAD or similar) showing the locations of the boreholes undertaken; Plots of the following final (quality assured) CPT results: o Measured cone resistance o Measured sleeve friction o Measured pore water pressure o Friction Ratio o Net cone resistance o Interpreted relative density (granular materials) o Interpreted undrained shear strength (cohesive materials) Final onshore laboratory test results (effective stress testing and cyclic testing may follow separately up to 16 weeks after completion of fieldwork) including summary tables; Final borehole logs; Plots of soil parameters versus depth for individual boreholes, including moisture content, unit weight, and undrained shear strength; Colour photographs of samples and cores. The CONTRACTOR shall provide a digital draft report, which shall be made final after processing of comments and approval by the CLIENT. The final field report shall consist of two (2) hard copies and two (2) electronic copies to be provided on digitally (CD/DVD). CONTRACTOR shall provide four (3) hard copies and four (3) CD copies of the final geotechnical report. 2.5 Execution of Seabed PCPT Mobilization Positioning Mobilization of the vessel to the site, complete with all necessary geotechnical equipment and personnel. Seabed PCPTs should be positioned within a 5m radius of the target co-ordinates. If an obstruction is encountered on the seabed or the seabed level exceeds 5-10 degrees (depending on availability of a levelling system), the seabed PCPT shall be re-positioned to avoid the obstruction or slope whilst remaining as close to the target co-ordinates as possible Executing seabed PCPTs The seabed PCPT system shall include a minimum 20 tonne thrust reaction and a cone tip capacity of 100 kn or 150 kn, depending on the cone tip area (see below). The tests shall be carried out in full accordance with ISSMFE Reference Test Procedures, British Standard BS 1377:1990, ASTM D and Eurocode EN At start of the individual CPT, the tip and friction sleeve readings are zeroed and the pore pressure reading checked to comply with the water depth. Page 13 of 19

14 The seabed elevation at the test location shall be registered by pressure transducers mounted on the subsea rig and corrected for specific gravity of the water column at the location. Comparative tape measurements versus depths registered as pressure shall be performed at all locations. Possible settlement, due to the net weight of the subsea rig shall be registered. The specifications of the seabed PCPT equipment shall include: A minimum thrust capacity of 200 kn (20 tonnes); Cone with a projected area of 10cm 2 or 15cm 2 ; A target penetration depth of 50m; Cone tip capacity of 100 kn (10 tons) (or 150 kn if using 15cm 2 cone). The typical parameters that define refusal of the seabed PCPT are as follows: 1. Total thrust equals nominal reaction provided; 2. Cone tip load is 100% of the cone tip capacity; 3. Sleeve friction is more than 15% of the cone tip capacity; 4. String deviation from the vertical is greater than twelve (12) degrees between the tip and the top of the hole; 5. Rod deviation is greater than three (3) degrees over a length of penetration of one metre or less; The CONTRACTOR operator judges that further penetration would damage the equipment, in which case an explanation shall be provided within 24 hours. 2.6 Data processing and reporting for seabed PCPT After carrying out the seabed PCPT investigation, CONTRACTOR shall process the data that is gathered during the field work and prepare a detailed report covering the total scope of work. The reporting requirements for the seabed PCPT work are detailed below Daily & Weekly reporting The CONTRACTOR is to submit daily reports throughout the period of the fieldwork, providing full details of previous 24 hours work and results. Further, CONTRACTOR shall issue a weekly report providing insight in the progress of the WORK on a weekly basis. The formatting of the daily and weekly report is specified in Section VII of this Contract Preliminary PCPT results Field report The Contractor is to provide preliminary (field) results within 72 hours of completion of each test. A Field report shall be made available within one week of the completion of the fieldwork. This report shall include: A statement of the purpose of the investigation; Daily logs (DPRs); A description of the Work carried out, including reference to specification and standards adopted and any deviations from them; Page 14 of 19

15 Exact locations of all PCPT tests (co-ordinates shall be with respect to ETRS89 datum, given in degrees, minutes and decimal minutes format as well as in eastings and northings using a UTM ETRS89 Zone 31 projection). Drawings (AutoCAD or Microstation format or similar) showing the locations of the PCPT tests undertaken; Plots of the following PCPT results: o Measured cone resistance o Measured sleeve friction o Measured pore water pressure o Friction Ratio o Net cone resistance o Interpreted relative density (granular materials) o Interpreted undrained shear strength (cohesive materials) The CONTRACTOR shall provide two (2) CD copies of the draft report. CONTRACTOR shall provide four (4) hard copies and four (4) CD copies of the FINAL REPORT, i.e. above described DRAFT REPORT after EMPLOYER s review and integration of EMPLOYER s comments. The CONTRACTOR shall provide electronic copies of the PCPT results in AGS or ASCII format. 2.7 Create a geological model of the site Based upon the information that is gathered through the geotechnical soil investigation and the information that is gathered through the geophysical soil investigation, including results provided by the Client and through interpretation of all other relevant data available (provided by the Client and in the public domain). CONTRACTOR shall create a geological model (report including drawings) of the site. The objective of this geological model is to: get insight in overall stratification and the soil conditions over the WIND FARM SITE and to identify possible constraints for the design and installation of offshore wind farms in the Borssele WIND FARM ZONE as a result of the soil conditions. The geological model shall address the following subjects: Identification of the soil layers that can be found over the site including all relevant soil parameters. Identification of areas within the Borssele WIND FARM ZONE that can be qualified in terms of suitability and quantified in terms of costs. Identify suitability or possible constraints of the Borssele wind farm zone regarding: o Transfer of forces from wind turbine & substation foundation to seabed. o Piling of foundations e.g. presence of boulders or rocks. o The use of jack-ups. o The use of gravity base foundations. o The use of foundations based on suction piles or suction buckets. o The installation of cables. Page 15 of 19

16 2.8 OFFSHORE REPRESENTATION The CLIENT may require up to two (2) CLIENT OFFSHORE REPRESENTATIVES to witness the offshore phase of the surveys works, in addition to any other client representatives required under the contract. The CONTRACTOR is to be responsible for providing safety induction training for the CLIENT OFFSHORE REPRESENTATIVES who are to work on or visit any vessel in connection with the execution of the work. The CONTRACTOR shall provide adequate facilities for the CLIENT OFFSHORE REPRESENTATIVES on any vessels to include a private cabin, office space, communication systems and messing facilities. CONTRACTOR shall provide Personal Protective Equipment (PPE), life jackets and any special offshore PPE for the CLIENT OFFSHORE REPRESENTATIVES for the duration of the project. Page 16 of 19

17 3 SCHEDULE OF KEY DATES The SCHEDULE OF KEY DATES, excluding WAITING ON WEATHER is set out in the table below; No. Description Date 1 COMMENCEMENT DATE CONTRACT [dd/mm/yyyy] 2 STARTING DATE of the WORK [dd/mm/yyyy] 3 Client conformation target coordinates and [dd/mm/yyyy] target depths Boreholes/PCPT s and target coordinates Seabed PCPT s 4 Project documentation finalized [dd/mm/yyyy] 5a Start of Mobilsation Borehole campaign [dd/mm/yyyy] 6a Mobilisation and transit to site for the Borehole [dd/mm/yyyy] campaign 7a Start of offshore works Borehole campaign [dd/mm/yyyy] 8a Offshore completion date Borehole campaign (excl WoW) [dd/mm/yyyy] 5b Start of Mobilsation Seabed PCPT campaign [dd/mm/yyyy] 6b Mobilisation and transit to site for the Seabed [dd/mm/yyyy] PCPT campaign 7b Start of offshore works Seabed PCPT campaign [dd/mm/yyyy] 8b Offshore completion date Seabed PCPT campaign (excl WoW) [dd/mm/yyyy] 9 Field Report [dd/mm/yyyy] 10 Draft Final Report [dd/mm/yyyy] 11 Client Review of Final Report [dd/mm/yyyy] 12 Final Report [dd/mm/yyyy] Table 2 Schedule of Key Dates Page 17 of 19

18 Appendix A. Wind Farm Sites and investigation zones Page 18 of 19

19 Appendix B. Cables and Pipelines at the Borssele WFZ Page 19 of 19