Inflection Point Engineering Section 4 — Structures and Foundations

Atmospheric Storage Tank Foundation Monitoring, Repair and Retrofit

IPE Engineering Practice IPE-EP-4-2-10

Document number: IPE-EP-4-2-10 · Section: 4 — Structures and Foundations

Figure 8 Tank Bottom Bulges And Depressions 27Figure 8 Tank Bottom Bulges And Depressions 27

Figure 9 Cone-Up, Earth Pad, Double Bottom 28

Figure 10 Cone-Down, Earth Pad, Double Bottom 29

Figure 11 Cone-Up, Gravel Ringwall Double Bottom 30

Figure 12 Cone-Down, Gravel Ringwall Double Bottom* 31

Figure 13 Cone-Up, Concrete Ringwall Double Bottom 32

Figure 14 Cone-Down Concrete Ringwall Double Bottom 33

Figure 15 Cone-Up, Piles/Mat, Double Bottom 34

Figure 16 Cone-Down, Piles/Mat, Double Bottom 35

Figure 17 Center Sump Detail 36

Figure 1`8 Double Bottom Liner Attachment 37

SCOPE

2.0 REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

STANDARDS AND PUBLICATIONS (CONTINUED)

API Standards
RP 651 Cathodic Protection of Aboveground Petroleum Storage Tanks Std 650 Welded Steel Tanks for Oil Storage
Std 653 Tank Inspection, Repair, Alteration and Reconstruction
ASME Codes
Sec VIIIPressure Vessels, Alternative Rules, Division 2
ASTM Standards
D471 Rubber Property - Effect of Liquids D638 Tensile Properties of Plastics
D751 Standard Test Methods for Coated Fabrics
D1004 Initial Tear Resistance of Plastic Film and Sheeting
D1204 Linear Dimensional Changes of Nonrigid Thermoplastic Sheeting or Film at Elevated Temperature
D2136 Standard Test Methods for Coated Fabrics-Low-Temperature Bend Test

DEFINITIONS

SETTLEMENT MONITORING

EXISTING TANK FOUNDATION EVALUATION

S  deflection (out  of  plane) , feet

L  arc length between measurement points, feet Y  yield strength, psi

E  Young' s modulus, psi H  tank height, feet

B  0.37R

where:

B  height of bulge or despression (max),inches

R  radius of inscribed circle in bulge or depressed area,feett

FOUNDATION REPAIR/RETROFIT WITHOUT TANK LIFT

Where partial tank shell relevelling is required because of excessive settlements, jacking against external shell lugs shall be used. Shell relevelling shall be performed in accordance with EP 9-1-6.

FOUNDATION REPAIR/RETROFIT WITH TANK LIFT

LEAK DETECTION. RELEASE PREVENTION AND CATHODIC PROTECTION

8.2 Cathodic Protection Systems

Cathodic protection systems shall be designed in accordance with EP 10-3-6.

PAINTING, INTERNAL LINING AND COATING

ALTERNATIVE SETTLEMENT ANALYSIS REQUIREMENTS

HYDROTEST REQUIREMENTS

SPECIAL REQUIREMENTS FOR RIVETED TANKS

13.0 TABLES

TABLE 1

DOUBLE BOTTOM DETAIL PARAMETERS

TYPE OF (1)
FOUNDATION		 SLOT (2)
HEIGHT (IN)		 FILL MATERIAL(3) MAX ECCENTRICITY (4)
OF SHELL/STUB
EP GR CR PM
MT		 6 IN
6 IN
6 IN
6 IN
6 IN		 CLEAN DRY SAND CLEAN DRY SAND CLEAN DRY SAND CLEAN DRY SAND
CLEAN DRY SAND		 0.10 IN
0.10 IN
0.10 IN
0.10 IN
0.10 IN

NOTES:

TABLE 2

PHYSICAL PROPERTIES OF FLEXIBLE SHEET LINER MATERIALS (3)

PROPERTY ASTM PROCEDURE VALUE
GRAB TENSILE STRENGTH D751 1000 lbs. (2500 psi) (2)
STRIP TENSILE STRENGTH D751 (D638) (2) 750 lbs. (2500 psi) (2)
TEAR STRENGTH D751 (D1004) (2) 50 lbs (50 lbs.) (2)
HYDROSTATIC RESISTANCE D751 - Method A 500 psi - 5 min.
LOW TEMPERATURE STRENGTH D-2136, 4hrs, 25°F No Cracking, 1/8" mandrel
DIMENSIONAL STABILITY D-1204, 1 hr, 212°F 4% max
THICKNESS (1) D-751 as specified
±0.002 in
CHEMICAL RESISTANCE (1) as specified as specified
MOISTURE ABSORPTION D-471 , 7 days, 70°F 5% max

NOTE:

TABLE 3 DOCUMENTATION REQUIREMENTS

FOR ATMOSPHERIC STORAGE TANK FOUNDATION MONITORING REPAIR AND RETROFIT PER EP 4-2-10

Item Description Format As-Built
1 Calculations of tank settlement and settlement history. See EP 2-5-2 N/A
2 Plan, elevation and detail drawings for double bottom retrofits. See EP 2-5-2 Yes
3 Cement grout specifications for bottom relevelling. See EP 2-5-2 N/A
4 Documentation of economic evaluation of tank bottom repair scenarios. See EP 2-5-2 N/A
5 Specifications for mud jacking materials and procedures. See EP 2-5-2 N/A
6 Details and materials specifications for ringwall repairs. See EP 2-5-2 N/A
7 Plan, elevation and detail drawings for tank life repairs and retrofits. See EP 2-5-2 Yes
8 Plan, elevation and detail drawings for retrofitted leak detection and release prevention systems. See EP 2-5-2 Yes
9 Results of field tests and inspection for impermeable membrane liners. See EP 2-5-2 N/A
10 Computer analysis input and output. See EP 2-5-2 N/A
11 Specification of sand used in double bottom retrofit. See EP 2-5-2 N/A
12 Documentation of physical property test results for impermeable liner materials. See EP 2-5-2 N/A

14.0 FIGURES

FIGURE 1

DIAMETER LOCATIONS FOR TANK SETTLEMENT MEASUREMENTS

Figure

NOTE:

(*)For tank diameters greater than 300 feet, number of diameter axes shall be specified by the Owner's Engineer.

FIGURE 2

MEASUREMENT OF ELEVATION DIFFERENCE BETWEEN TANK AND SURROUNDING GRADE

Figure

FIGURE 3

SPACING REQUIREMENTS FOR TANK BOTTOM ELEVATION MEASUREMENTS

Figure

NOTE:

If edge cutting has occurred, measure elevation at one-foot increments along each axis.

FIGURE 4

TANK SHELL DIFFERENTIAL SETTLEMENT

Figure

FIGURE 5

TIME - SETTLEMENT HISTORY

Figure

FIGURE 6

SETTLEMENT DATA POINT LOCATIONS

Figure

NOTES:

FIGURE 7

EDGE CUTTING SETTLEMENT

Figure

NOTES:

FIGURE 8

TANK BOTTOM BULGES AND DEPRESSIONS

Figure

FIGURE 9

CONE-UP, EARTH PAD, DOUBLE BOTTOM

Figure

NOTE:

See Figure 10 for notes.

FIGURE 10

CONE-DOWN, EARTH PAD, DOUBLE BOTTOM

Figure

NOTES:

FIGURE 11

CONE-UP, GRAVEL RINGWALL DOUBLE BOTTOM

Figure

Note:

FIGURE 12

CONE-DOWN, GRAVEL RINGWALL DOUBLE BOTTOM*

Figure

Notes:

See Figure 10 for Notes.

May be revised after FE Parametric Study.

FIGURE 13

CONE-UP, CONCRETE RINGWALL DOUBLE BOTTOM

Figure

Notes:

See Figure 10 for Notes.

May be revised after FE Parametric Study.

FIGURE 14

CONE-DOWN CONCRETE RINGWALL DOUBLE BOTTOM

Figure

Notes:

See Figure 10 for Notes.

May be revised after FE Parametric Study.

FIGURE 15

CONE-UP, PILES/MAT, DOUBLE BOTTOM

Figure

Notes:

See Figure 10 for Notes.

May be revised after FE Parametric Study.

FIGURE 16

CONE-DOWN, PILES/MAT, DOUBLE BOTTOM

Figure

Notes:

See Figure 10 for Notes.

May be revised after FE Parametric Study.

FIGURE 17 CENTER SUMP DETAIL

Figure

NOTES:

FIGURE 18

DOUBLE BOTTOM LINER ATTACHMENT

Figure

info@inflectionpointengineering.com

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.

© 2026 Inflection Point Engineering, LLC. All rights reserved.