Norma PDVSA 0602 1 472 Dikes for Storage Tanks

PDVSA N° TITLE

REV. DATE DESCRIPTION PAG. REV. APPD. APPD.

APPD.BY DATEDATE

VOLUME 18–I

� PDVSA, 1983

0602.1.472 EARTH DIKES FOR STORAGE TANKS

FOR APPROVAL

José Gilarranz Antonio OrtizAUG.85 AUG.85

ENGINEERING SPECIFICATION

AUG.85

APR.94

AUG.95 L.T.

L.T.

J.S.

2

1

0

MODIFICATION PAR. 4.1

GENERAL REVISION 5

5

E.J.

E.J.

J.G.

A.N.

A.N.

A.O.

ENGINEERING DESIGN MANUAL

ESPECIALISTAS

APPD.BY

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EARTH DIKES FOR STORAGE TANKS AUG.952

PDVSA 0602.1.472

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.Menú Principal Indice manual Indice volumen Indice norma

Index1 PURPOSE 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 SYSTEM DESCRIPTION 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 TANK–DIKE SPACING 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 EARTH DIKES 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Dike Design Basis 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Earth Dike Material 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Initial Preparation 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Dike Dimensions and Slopes 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 EROSION PROTECTION 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 ACCESS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Personnel 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Vehicular 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7 DIKE BASINS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Requirements 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Impervious Dike Basins 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8 GRADING AND DRAINAGE 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Sump 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Drains 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 GEOTECHNICAL CONSULTANT 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10 SAFETY STANDARDS 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 PURPOSEThis guide presents considerations pertinent to the design and construction ofearth dikes for tank farms.

2 SYSTEM DESCRIPTION

2.1 Diked areas are used to retain accidental discharge of product from above groundtanks in order to prevent the liquid from endangering adjacent, facilities, propertyor waterways. Stormwater control, protection of tanks from high water andpollution control may also be required.

2.2 Other methods such as concrete dikes, and diversion systems are used to controltank spillages. Normally, the diversion system will channel the drainage by gravityto an impounding basin.

The impounding basin can be formed by installing an impounding dike around aholding area.

2.3 Concrete dikes, dikes and basins for permanent storage or water treatment,earthdams and diversion systems are not covered in this guide.

3 TANK–DIKE SPACINGSpacing between tank shell and dike shall not be less than tank shell height.

Spacing between adjacent tanks shall not be less than 1 – 1/2 diameters of thesmaller tank. For all cases, tank–dike spacing could be determined by installationdesign or local requirements.

Dike content capacity shall not be less than 150% of tank volume. If more thanone tank inside dike, dike content capacity shall be at least 150% of larger tankvolume, plus displaced volume of the rest of tanks.

4 EARTH DIKES

4.1 Dike Design Basis

Design dikes sufficiently impervious to contain a product spill for a period of timeadequate for recovery and cleanup. They shall be capable of withstanding a fullhydrostatic head of water, and seismic vibrations, in accordance with EngineeringSpecification PDVSA FJ–251, “Metallic Tanks Seismic Design”.




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4.2 Earth Dike MaterialVirtually any soil except rock flour, silt, sand or gravel may be used. A materialwill probably be satisfactory if, when material passing No. 200 sieve with lowestwater content can be rolled between the palms of the hands into a 3 mm (1/8 in)thread without crumbling in accordance with ASTM D1557. The best material isa clay or clayey silt that is impervious when properly installed. Compact theearthen material to 90 percent of the maximum obtained in ASTM D 1557.

If only granular or other permeable material is available an impervious core canbe built into the dike. This core may consist of imported clay soil, compacted to150 mm (6 in) thickness, 50 mm (2 in) layer of asphaltic concrete, or a plastic liner.Figure 1 shows a typical core construction.

(2 FT) MIN.

TANK SIDE

(1 FT) IMPERVIOUSCORE

150 mm – 200 mm(6 in – 8 in)IF NOT SAND460 mm (18 in)IF SAND

0.3 m (1 ft)

VAR

IES

FIG. 1 EARTHEN DIKE WITH IMPERVIOUS CORE

4.3 Initial PreparationBefore dike construction is started, remove the vegetation and topsoil. Scarify thesurface 150 mm to 200 mm (6 in to 8 in) deep and excavate 300 mm (12 in) widerthan the proposed dike and recompact the area. If the virgin soil is sand, removeit to a depth of 450 mm (18 in) before placement of dike materials.




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4.4 Dike Dimensions and SlopesHeight 3000 mm (9’–10”) Maximum (Tank Side)Slope Consistent with angle of repose of soil used. Not steeper than 2

horizontal to 1 verticalWidth at Top 1000 mm (3 ft.) – Minimum

5 EROSION PROTECTIONThe method most widely used consists of one prime coat with a mixture of 75%Asphalt RC–2 and 25% kerosene, pressured sprayed at a rate of 1,2 to 1,5 l/m2

(depending on soil), and a second coat of 100% Asphalt RC–2.

Other methods for erosion protection are wire mesh, granular aggregate andPC–2 asphalt, precast concrete panels. Erosion protection method shall beapproved by Owner.

6 ACCESS

6.1 PersonnelFor dikes over 1000 mm (3 ft.) in height provide means of crossing at locationsof normal ingress and egress. Use concrete stairs, prefabricated stairs or a rampwith handrails.

6.2 VehicularWhen vehicular access is required for dikes with low or moderately high dike walls,an earth ramp is provided. ramps shall have a minimum width of 3.7 m (12 ft.) andshould not exceed a 15 percent grade. Compact the ramp to 95% of maximumobtained in ASTM D 1557 and cover with a minimum of 150 mm (6 in) ofcompacted stone or shell. Instead of the above an asphalt concrete surface canbe provided.

7 DIKE BASINS

7.1 RequirementsDike basins are used to prevent seepage into underground soils. Localregulations may require dike basins to be impervious for certain classes of liquids.

Consideration should be given to make a dike basin impervious only under specialconditions such as:

– Extremely porous soil.– Contamination of water table, water ways or other surface waters.




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– Possible seepage of product from plant properly, to lowlying areas or to housesin the area.

– Toxic chemicals to be contained.

7.2 Impervious Dike BasinsImpervious dike basins can be designed using one of the following methods:

– Install a plastic liner under the basin. Liner material shall be compatible withstored liquid. Bury the liner when mechanical protection is required.

– Line the basin with a clay layer 100 mm to 150 mm (4 to 6 in) thick. Use thickerlayer when vehicular traffic has access to basin.

– Other methods recommended by geotechnical consultant.

8 GRADING AND DRAINAGEGrade tank basins away from the tanks a minimum slope of one percent at least,15 meters or up to dike base, whichever is shorter. Avoid interference withroadways or pipeways.

8.1 SumpProvide a sump with valved drains at the lower corner of the basin. Sumpdimensions are:

Area 0.84 m2 ( 9 ft.2)Depth 600 mm minimum (2 ft.)

8.2 DrainsDrainpipe is a steel pipe through the dike with a normally closed indicating valveoutside the dike that will be operable during a fire. Drains are provided with sealsto prevent the spread of flame through the drainage system when flammablematerials are stored, in accordance with Engineering Specification PDVSAH–251, “Drain Systems”.

9 GEOTECHNICAL CONSULTANTRecommendations for dike materials, dike construction, basin materials andconstruction shall be provided by the Geothechnical Consultant. The maximumheight, slopes, slope protection and special conditions shall also be supplied.

10 SAFETY STANDARDSVenezuelan Fire Prevention and Protection Standard shall apply. If should therebe any discrepancies between this Guide and PDVSA Risk Engineering Manual,the more stringent shall apply, with previous approval of Owner’s representative.




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Norma PDVSA 0602 1 472 Dikes for Storage Tanks