PREPARED BY NA

PTT PUBLIC COMPANY LIMITED CHECKED

BY ONSHORE COMPRESSOR STATION 4 PROJECT

APPROVED BY

CERTIFIED

(PTT) NA

REV.NO.

DATE

REVISED BY

APPROVED BY

DESCRIPTION

D1 18-Feb-08 NA ISSUED FOR INTERNAL REVIEW D2 21-Jul-08 NA REVISION ISSUED FOR ITB

SPECIFICATION FOR

DESIGN OF STORAGE TANK FOUNDATIONS

SPC 0804.02-40.10 REV.D2

TOTAL 14 PAGES

AREA CODE OF SITE LOCATION

GENERAL AREA: 010

.

PTT PLC. CONTRACT NO.

PTT PLC. PROJECT NO.

0804.02

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

SPC 0804.02-40.10 PAGE : 2 OF 14

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CONTENTS

SECTION

1.0 SCOPE ....................................................................................................4

2.0 DEFINITIONS ...........................................................................................4

3.0 REFERENCES ...........................................................................................4

4.0 GENERAL ................................................................................................4

5.0 SUBGRADE..............................................................................................5

6.0 TANK ELEVATION ....................................................................................6

7.0 GRANULAR RING BEAMS..........................................................................6

8.0 CONCRETE RING BEAMS ..........................................................................7

9.0 GRANULAR FILL PADS..............................................................................7

10.0 REINFORCED CONCRETE RAFT FOUNDATIONS ...........................................8

11.0 PILED FOUNDATIONS ...............................................................................8

12.0 BITUMEN SAND SURFACING.....................................................................8

13.0 CATHODIC PROTECTION ..........................................................................9

14.0 ADDITIONAL CONSIDERATION ................................................................10

15.0 CONSTRUCTION TOLERANCES................................................................10

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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CONTENTS (Cont’d) SECTION SUBJECT

APPENDIX 1 STORAGE TANK WITH SUITABLE SUBGRADE AT OR NEAR

GRADE LEVEL FOUNDED ON A GRANULAR PAD FOUNDATION WITH A GRANULAR RING BERM.

APPENDIX 2 STORAGE TANK WITH SUITABLE SUBGRADE AT OR NEAR

GRADE LEVEL FOUNDED ON A GRANULAR FILL PAD WITH A REINFORCED CONCRETE RING BEAM.

APPENDIX 3 STORAGE TANK WITH SUITABLE SUBRADE AT OR NEAR

GRADE LEVEL FOUNDED ON A REINFORCED CONCRETE RAFT WITH A REINFORCED CONCRETE RING BEAM.

APPENDIX 4 STORAGE TANK WITH UNSUITABLE SUBGRADE FOUNDED

ON A REINFORCED CONCRETE FOUNDATION AND LOAD BEARING REINFORCED CONCRETE PILES.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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1.0 SCOPE This Standard provides general guidance and practice to be followed for the design of generally occurring foundations for vertical atmospheric storage tanks. This standard shall not apply to refrigerated, cryogenic, pressurised or corrosive chemical storage tanks. 2.0 DEFINITIONS (Deleted) 3.0 REFERENCES Design shall conform with the latest revisions of the following Standard and Codes of Practice at time of Contract Placement: 3.1 Engineering Standards: SPC-0804.02-40.05 Wind and Earthquake, Loading SPC-0804.02-40.06 Design Loadings for Buildings, Equipment, Structures and Foundations SPC-0804.02-40.01 Specification for Civil Works SPC-0804.02-40.01.01 Specification for Precast Concrete Piling Work SPC-0804.02-40.01.02 Specification for Cast Institute Concrete Bored Piling Work National / International Standards See SPC 0804.02-40.01 - Specification for Civil Works for applicable standards relevant to the construction of the storage tanks. The Standards and Codes of Practices listed shall be used, however National Standards or Local Authority Codes maybe substituted provided they are no less stringent and prior approval is obtained from PTT/CONSULTANT. 4.0 GENERAL 4.1 The design of tank foundations shall be based on the advice and design parameters given in the Geo-technical Investigation Report(s). All anticipated settlements and deformations of the foundation shall be reviewed by specialist civil/structural, Tank/Vessel and Piping Engineers employed by CONTRACTOR in order for them to assess if the anticipated movement of the tank is acceptable for the design of the tank and the tank

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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piping attachments. Foundations shown in Appendices 1, 2, 3 and 4 are typical of the foundations to be used, unless otherwise specified in the Job Specification or recommended in the Geo-technical Investigation Report(s). 5.0 SUBGRADE 5.1 The subgrade shall be capable of supporting the tank, its attachments and its maximum weight of contents (under operating conditions) without general and/or local shear failure or excessive: Unequal settlement Centre to edge settlement Total settlement Deformation in tank floor Where the subgrade is capable of supporting the tank and its contents, the soil shall be thoroughly compacted in accordance with the requirements of Engineering Standard SPC 0804.02-40.01.04. Soft spots shall be removed and replaced with compacted fill of granular or other stable material compacted to the same density as the subgrade. If the subgrade is unable to support the loadings from the tank without excessive unequal or total settlement, one or a combination of the following methods may be considered to improve the subgrade: Remove the unsuitable subgrade and replace with thoroughly compacted granular fill material or other stable material. Deep compaction of the unsuitable subgrade by vibro-flotation or dynamic consolidation if satisfactorily proved by testing by CONTRACTOR. Consolidation of the unsuitable subgrade by temporary preloading with or without providing vertical drains drilled into the subgrade to accelerate the rate of consolidation Piling Rigid raft type foundation Ground stabilisation utilsing methods other than those noted above. Other methods such as cement columns may also be acceptable however full details shall be provided by CONTRACTOR for approval by PTT/CONSULTANT.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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6.0 TANK ELEVATION The height above grade of the tank floor after total settlement shall not be less than 300 mm. in order to prevent ground water from being trapped beneath the tank and to facilitate piping and drainage attachments to the lower parts of the tank. 7.0 GRANULAR RING BEAMS 7.1 Granular ring beams shall be: - 7.1.1 Thoroughly compacted in accordance with Engineering Standard SPC 0804.02–40.01.04 well graded granular material or crushed stone, within the grading limits shown in Table 1.

ASTM D422 SIEVE SIZE PERCENTAGE PASSING (BY WEIGHT)

2 “ 50 mm. 100 1 ½ “ 37.5 mm. 100 3/4 20 mm. 75 – 85 3/8 10 mm. 60 – 75 No. 4 4.75 mm. 40 – 60 No. 10 2 mm. 20 – 40 No. 30 0.6 (600µm.) 10 – 20 No. 200 0.075 (75µm.) 1 – 10

TABLE 1 All granular materials shall comply with the requirements of ASTM D448 and D693. Compacted in layers not exceeding 200 mm. thickness when uncompacted. 2.0 m. minimum width at the top, symmetrical about tank shell, with sloping sides of 1 vertical to 1.5 horizontal. Surfaced with materials as described in Section 9 of this Standard except the 50 mm. sand asphalt surfacing outside the tank shell, shall be applied after the hydrostatic test. Total and differential settlements shall be computed by an experienced Geo- technical Engineer employed by CONTRACTOR. All such settlements shall be reviewed and agreed with the specialist tank vendors and PTT/CONSULTANT.

DESIGN OF STORAGE TANK FOUNDATIONS

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8.0 CONCRETE RING BEAMS 8.1 Concrete ring beams shall be designed and constructed in accordance with ACI 318 M. Concrete ring beams shall be designed to resist the following simultaneous conditions: to span 4.0 m. horizontally unsupported to resist the surcharge from the tank to resist pressure from the retained earth An experienced Geo-technical Engineer employed by CONTRACTOR shall determine a depth of foundation to reduce the component of settlement due to lateral flow of soil to an acceptable proportion of total settlement. Concrete ring beams shall be of adequate width to ensure that the theoretical unit bearing pressure at the bottom of the ring beam is the same as the theoretical unit bearing pressure at the centre of the filled tank. Concrete ring beams shall be of adequate width and depth to accommodate tank holding down bolts. Concrete ring beams shall be designed to control cracking appropriate to the prevailing exposure conditions. 9.0 GRANULAR FILL PADS 9.1 Granular fill pads shall be constructed of inert granular or other stable material approved by PTT/CONSULTANT. Granular fill pads shall be laid in layers not greater than 200 mm. In thickness and shall be compacted to a minimum 95% of relative density in accordance with AASHTO T180 and ASTM D4253 and D4254. Any granular materials that fall outside the suitability of the relative density tests noted in the above ASTM Standards shall be well compacted. All granular fill shall have moisture content suitable for achieving the minimum relative density noted above. CONTRACTOR shall determine in-place density in accordance with one or more methods given by ASTM D1556, D2167, D2922 and D2937. The top of the pad shall be covered with 100 mm. thickness of compacted crushed stone or gravel well graded from 10 mm. to 20 mm. Chips and quarry dust shall be used to fill in the surface voids. The top of the 100 mm. layer

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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shall be sprayed with asphalt and a 50 mm. thick layer of bitumen sand mix shall then be applied 3extending 300 mm. beyond the tank shell. The 100 mm. thick layer of crushed stone or gravel well graded 10 mm. to 20 mm. shall extend over the granular ring berm. 10.0 REINFORCED CONCRETE RAFT FOUNDATIONS 10.1 Reinforced concrete raft foundations shall be designed and constructed in accordance with Engineering Standard SPC 0804.02-40.01.01 and ACI 318 M. 11.0 PILED FOUNDATIONS 11.1 Pile foundations shall be designed and constructed in accordance with Engineering Standards SPC 0804.02-40.01.01 & SPC 0804.02-40.01.02. 11.2 The concrete pad shall be designed to span between the piles assuming no pile failure and investigated for the case assuming differential settlement of individual piles. Specialist Geo-technical engineering advice shall be taken in assessing the amount of differential settlements of piles. 12.0 BITUMEN SAND SURFACING 12.1 A smooth Bitumen-sand mix of minimum 50 mm. thickness shall be hot laid over the foundations for weather proofing/weather protection and to provide a sufficiently firm layer. This surfacing shall also be required to retard corrosion of the tank bottom. The Bitumen-sand mix shall be such as for the bitumen to just wet the sand. A suitable bitumen-sand can be produced by hot-mixing in the following proportions by mass: 9 ± 0.5% (m/m) non-toxic cut back bitumen (i.e. fluxed with kerosine and not creosote*); 10 ± 1.0% (m/m) filler: either limestone dust passing a sieve of nominal aperture size 75 µm complying with ordinary Portland cement; 81 ± 1.5% (m/m) clean dry washed sand with the properties given ASTM C33. * Creosote fluxed Bitumen is not considered to be acceptable in view of its acid content.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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13.0 CATHODIC PROTECTION When cathodic protection of the tank bottom is adopted, consideration shall be given to the compatibility of the foundation surfacing material in contact with the tank floor. CONTRACTOR shall fully evaluate the need for any cathodic protection and provide a fully detailed evaluation report for review and approval by PTT/CONSULTANT. The following considerations shall apply: - 13.1 General Review the flexural and settlement characteristics of the tank and foundation. Review the need for protective coatings to underside of tank bottom. Consider the aggressive nature of the soil and support foundations together with ground water quality and levels. 13.2 Structure Preparation The tank foundation mound should as far as possible be constructed so that it will distribute protection current uniformly to the whole of the underside of the tank. This means that the use of rubble, rock fill etc., should be avoided and the mound should consist of fine-grained and well compacted material, to a minimum depth of 150 mm. Where individual plates (for tank bottom fabrication) are lapped or welded ensure there is electrical continuity across all joints. Provide bonding between individual tanks where a group of tanks require cathodic protection. Provide isolation joints in all pipelines and fittings connected to tanks if there is a need to confine the protection current. Earthing electrodes connected to the tank should be of zinc, stainless or galvanised steel. 13.3 Application of Cathodic Protection Current density figures of the order of 10mA/m2 are normally required for uncoated tank bottoms resting on bitumen-sand carpets and, owing to the large areas involved, impressed current shall be used preferred. Sacrificial anodes may, however, may be used for small isolated tanks on soil with low resistivity subject to PTT/CONSULTANT approval. A system of buried or submerged electrodes connected to the positive terminal of an independent direct current shall be arranged symmetrically around a tank

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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or group of tanks. Dependent upon the space available, the groundbeds should be located not less than one tank diameter from the tank periphery to provide optimum current distribution over the tank bottom. 13.4 Particular Considerations Structure/soil potentials vary across the underside of a cathodically protected tank bottom so that rim potentials usually need to be more negative than –0.85 B in order to ensure that this protection potential is attained at the centre. On new construction, reference electrodes shall be installed at representative point across the foundation mound. These shall be such that they will remain in good condition for along time. If such reference electrodes have not been installed an arbitrary value of rim potential has to be adopted. Potentials in the range –1.10 V to –1.20 V (copper/copper sulphate reference electrode) have been found to be satisfactory. Tanks that remain empty for long periods are unlikely to be fully protected because while the tank is empty the bottom moves out of contact with the foundation. 14.0 ADDITIONAL CONSIDERATION In addition to the foregoing types of tank foundations the following items will need to be incorporated into the design: - Leak detection system to tank bottom. This shall comprise of a high density polyethylene membrane (HDPE) at least 2 mm. thick and a collection sump/drain. The membrane shall ideally have factory fabricated/sealed seam joints which shall be 100% tested by vacuum box methods. Any joints shall be repaired and re-tested by vacuum box methods. Any joints shall be repaired and re-tested prior to transporting to site. Prevention of ground contamination. Permeable membrane/geotextile to protect formation level. 15.0 CONSTRUCTION TOLERANCES Construction tolerances shall be such that the difference in level of the tank foundation between any two points 10 m. apart around the periphery of the tank shall not be greater than ± 6 mm. and the envelope of peripheral surface levels shall lie within 12 mm. above to 12 mm. below the design levels. Closer tolerances in the tank foundations peripheral levels may be necessary in the case of floating roof tanks. Uneven foundation conditions or settlement can result in the shell assuming an oval shape at the top, causing the floating roof to stick.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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APPENDIX 1 STORAGE TANK WITH SUITABLE SUBGRADE AT OR NEAR GRADE LEVEL FOUNDED ON A GRANULAR FILL PAD FOUNDATION WITH A GRANULAR RING BEAM

KEY:- 1. Thoroughly compacted graded granular material or crushed stone (Refer Table 1). 2. Thoroughly compacted fill of granular or other stable inert material. 3. 100 mm. thick crushed stone or gravel graded 10 mm. to 20 mm. with voids filled with chips and quarry dust. 4. Sprayed asphalt skim coat. 5. 50 mm. thick bitumen sand surfacing extending to 300 mm. outside tank shell. 6. Surfacing to berm as Item 5 but applied after completion of Hydrostatic Test. 7. In consultation with the Geo-technical Engineer a permeable membrane/geotextile may be used to protect the subgrade formation level.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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APPENDIX 2

STORAGE TANK WITH SUITABLE SUBGRADE AT OR NEAR GRADE LEVEL FOUNDED ON GRANULAR FILL PAD FOUNDATION WITH REINFORCED CONCRETE RING BEAM

KEY:- 1. Thoroughly compacted fill of granular or other stable inert material. 2. 100 mm. thick crushed stone or gravel graded 10 mm. to 20 mm. with voids filled with chips and quarry dust. 3. Sprayed asphalt skim coat. 4. 50 mm. thick bitumen sand surfacing. 5. In consultation with the Geo-technical Engineer a permeable membrane/geotextile may be used to protect the subgrade formation level. 6. Consideration shall be given to siting the tank shell central over the ring beam particularly in the case of a tank with a floating roof.

DESIGN OF STORAGE TANK FOUNDATIONS

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APPENDIX 3

STORAGE TANK WITH SUITABLE SUBGRADE AT OR NEAR GRADE LEVEL FOUNDED ON A REINFORCED CONCRETE RAFT WITH A REINFORCED CONCRETE RING BEAM

Note: 1. Consideration shall be given to siting the tank shell central over the ring beam particularly in the case of a tank with a floating roof. 2. Expansion joint may be omitted in the case of smaller diameter tanks in favour of a maintenance free joint.

DESIGN OF STORAGE TANK FOUNDATIONS

PTT PUBLIC COMPANY LIMITED ENGINEERING SPECIFICATION

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APPENDIX 4

STORAGE TANK WITH UNSUITABLE SUBGRADE AT OR NEAR GFRADE LEVEL FOUNDED ON A REINFORCED CONCRETE FOUNDATION AND LOAD BEARING

REINFORCED CONCRETE PILES