## ESTCP Final Report

ENVIRONMENTAL SECURITY
TECHNOLOGY CERTIFICATION PROGRAM

U.S. Department of Defense



### Validation of the



## Low-Range Differential Pressure (LRDP) Leak Detection System

for Small Leaks in Bulk Fuel Tanksii Executive Summary

The Naval Facilities Engineering Service Center (NFESC ), Port Hueneme, California, and its industrial partners, Vista Research, Inc., and Vi sta Engineering Technologies, L.L.C., have demonstrated and validated (DEM/VAL) an innovative mass-based leak detection system for bulk underground storage tanks (USTs) containing petroleum fuels. The Low-Range Differential Pressure (LRDP) system is a computer-controlled system that can reliably detect small leaks in bulk USTs ranging in size from 50,000 gal to 12,500,000 gal. As part of this project, it has been evaluated for pe rformance by an independent third party in a 122.5-ftdiameter, 2,100,000-gal tank following EPA’s standard test procedures. The LRDP meets the monthly monitoring and annual precision (tightness) test regul atory compliance guidelines established by California using either a 10-h (overnight) or 24-h test.

This project was performed under the Environmental Security Technology Certification Program (ESTCP)

. The objective of the ESTCP is to demonstrate and va lidate innovative environmental technologies that are needed to address the environmental objectives of the Depa rtment of Defense (DoD), that are cost effective, and that will be ready for the development of comme rcial products and services at the completion of the DEM/VALs. All of the objectives of the project have b een met, and the LRDP is ready for commercial use. Both (1) on-line, permanently installed monitoring syst ems and (2) tightness testing services using the LRDP can be obtained commercially through Vista Research, Inc.

The LRDP system achieves a very high level of performance against small leaks because of its high precision (0.0002 in.) and its accurate methods of compensating fo r the thermal expansion and contraction of the fuel, the instrumentation, and the tank. Because of its i nnovative design, the LRDP achieves this high level of precision and accuracy with an off-the-shelf, industrial- grade differential pressure sensor. Thus, the LRDP not only delivers high performance, but it is also rugged and field-worthy.

The LRDP system is fully automatic and is comprised of (1) an innovative in-tank level sensing unit, (2) an embedded remote test controller to collect and analyze th e data from a test, and (3) a host computer to initiate, report, and archive the results of a test. A test can be initiated by an operator or can be automatically scheduled for a future date and time. The in-tank sen sor can be installed through a standard 8-in.-daimeter opening without removing fuel from the tank. The electronics meet Class 1, Div. 1 standards. The LRDP system is compatible with the DoD Fuels Accounting Sy stem (FAS) and can be integrated with FAS to test the tanks in a fuel farm or a bulk storage facility.

The in-tank sensor is comprised of (1) a vertical referen ce tube that spans the full usable height of the tank, (2) a sealed, bottom-mounted container that houses all of the level-measurement sensors, and (3) a special bellows-mounting system that is used to attach the system to the top of the tank. The reference tube is shaped so that it has a cross-sectional area that is proportional to the cross-sectional area of the tank as a function of depth. Except for 50,000-gal USTs and the 12,500,000-ga l Red Hill tanks, all of the DoD’s bulk USTs have vertical walls, and therefore, the reference tube has a constant cross-sectional area. A valve at the bottom of this tube allows fuel from the tank to enter or leave. When the tank is to be test ed for leaks, the valve is closed, thus isolating the fuel in the reference tube fro m that in the tank. As the level of liquid in the tank fluctuates, the level of liquid in the closed reference t ube mimics it—except when the change in level is due to a leak. High precision is achieved because the dynamic ra nge of the differential pressure sensor only needs to accommodate the differences in level between the referen ce tube and the tank and not the full height of the tank. The very small differences between the changes in level (pressure) in the tank and those in the tube are detected by a differential pressure sensor that is located in the sealed container at the bottom of the tube. Thus, the differential pressure sensor makes a direct measure ment of the change in level that is due to a leak, if one is present. Because the differential pressure is hou sed at the bottom of the tank, where it is not subject to ambient air conditions, it avoids a common problem of other mass-based leak measurement systems— thermally induced drift of the pressure sensor. In addition, the special bellows-mounting system removes any thermally induced vertical movement of the tank, the manway, or the in-tank sensor. The LRDP system is self-calibrating, and its performance and functionality can easily be checked between tests any time the valve is in the open position.

The performance of the system was independently evaluated for a 10- and a 24-h test by Ken Wilcox Associates, Inc. (KWA), a nationally recognized third-party evaluator, usi ng a variety of detection thresholds that were selected (1) to maintain a low probability of false alarm, (2) to optimize performance against certain target leak rates, and (3) to meet or exceed known re gulatory requirements. The performance was determinediii experimentally and was reported in accordance with th e guidelines set forth in “Alternative Test Procedures for Evaluating Leak Detection Methods: Evaluation of Bulk Field-Constructed Tanks,” a standard test procedure for bulk underground tanks that is approve d by the National Work Group on Leak Detection Evaluations (NWGLDE), an EPA-spons ored oversight group. A leak de tection method cannot be used unless the evaluation has been approved by this group. The evaluation consisted of 12 tests conducted on a 122.5-ftdiameter, 2,100,000-gal bulk underground storage tank contai ning jet fuel and located at the Navy’s Point Loma Fueling Facility, San Diego, California. The t ests were conducted over a wide range of temperature and induced leak conditions beginning on March 22, 2000 and ending on June 8, 2000. Neither the temperature conditions nor the leak rates were made available to NFESC until the test results had been generated and the evaluation report prepared.

The LRDP is currently listed by the NWGLDE and is approved for use in California based on a third-party evaluation previously conducted at NAS North Island on an 88-ft-diameter tank. The results of the current ESTCP evaluation, conducted on the 122.5-ft-diameter tank at Point Loma, a much larger tank than the one used in the North Island evaluation, have been s ubmitted to the NWGLDE for review and update of the previous listings. The results of the KWA evaluation (whi ch are presented in this report) indicate that a single 10-h test with the LRDP-10 can detect a leak of 1.14 gal/h with a probability of detection (P D ) of 95% and a probability of false alarm (P FA ) of 5% in a 122.5-ft diameter tank. The performance of the LRDP-10 scales with the product surface area of the tank and improv es as the tank diameter decreases. The LRDP-10 can detect leaks as small as 0.2 gal/h in a single test in a 51 -ft-diameter tank; by averaging four tests, a 0.2-gal/h leak can be detected in a 73-ft-diameter tank with th e same probabilities of detection and false alarm. The performance improves with a 24-h test. The LRDP- 24 can detect a leak of 0.69 gal/h with a P D of 95% and a
P FA of 5% in a 122.5-ft diameter tank; when the 12 mont hly tests are averaged toge ther, the system has the capability for detecting leaks as small as 0.2-gal/h. The LRDP-24 can detect leaks as small as 0.2 gal/h with the same P D and P FA in a 66-ft-diameter tank with a single test and in a 93-ft-diameter tank by averaging four tests together. The LRDP-10 and the LRDP-24 are the only in-tank, on-line monitoring systems that can meet both Option 7 and Option 10 of the California regul atory guidelines for underground bulk storage tanks.

A DEM/VAL of the LRDP system configured to test 50,000-gal underground storage tanks was performed at Hunter Army Airfield. For these tests, the reference tube was shaped to match the cylindrical cross-section of the tank as a function of depth. While a third-party evaluation was not performed, it was clear from the results of the DEM/VAL tests that the LRDP could meet the 0.2-gal/h monthly monitoring regulatory requirements with an 8-h test.

Many important improvements to the LRDP previously evaluated at NAS North Island have been made under this ESTCP project. As a consequence of these improvements, the LRDP is ready for implementation throughout the DoD. Some of these improvements are:



## • The notebook computer and data acquisition system were replaced with field-worthy embedded controller, which collects data, evaluates data qua lity, analyzes test results, and stores the results.



## • The system was made fully automatic, and the soft ware was made easy to use. The electronics are housed in an explosion proof container and meet Class 1, Div 1 Standards.



## • The system was originally approved as a portable system and can now also be used as a stand-alone system for on-line, real-time, in-tank monitoring.



## • The in-tank sensor unit was redesigned for easy inst allation and now fits into a standard 8-in. diameter opening and a tank of any diameter and any product depth.



## • The LRDP can be easily interfaced with base fu eling operations, including the FAS, and can be used for both leak detection and inventory monitoring



## • The evaluated performance of the LRDP is 20% be tter than originally determined in the first evaluation, and the performance limitations (e.g ., a 24-h waiting period) have been removed.



## • A leak detection test can be conducted with the LRDP using either a 10-h or a 24-h test.

The LRDP has several significant cost advantages over other internal and external technologies. The cost advantages are realized because of the extremely high performance of the LRDP and the low probability of false alarm, the on-line monitoring capability of the LRDP when permanently installed in a tank, the capability of the system to conduct a short test (an overnightiv test), and the low recurring costs associated with testing. For each tank brought into compliance, the LRDP can realize cost savings over other mass-based methods in terms of installation and testing of $250,000 or a factor of 3 over a 10-year period. The cost savings realized by the LRDP over an in-tank tracer method can be well over $1,000,000 or a factor of 12 over a 10-year period. This can result in savings of up to several tens of millions of dollars for each DoD fuel storage facility. The savings of the LRDP compared to other mass-based systems would result ina payback of less than three years. This payback is less than one year when compared to an intank tracer method. The cost of a tracer method is expensive because of the high recurring cost of testing. The costs of other mass-based methods are high because of lower performance and the inability to meet both the monthly monitoring and annual precision regulatory requirements with an on-line system. In addition to the installation and operational cost savings, the LRDP has the potential to save DoD many hundred of millions of dollars in terms of clean-up and tank replacement cost avoidance.v Table of Contents

Executive Summary.............................................................................................................. ......... ii

List of Figures................................................................................................................ ............. viii

List of Tables ................................................................................................................. ............... xi

Acronyms....................................................................................................................... ............. xiii

Acknowledgments................................................................................................................ ....... xiv

1.0 Introduction.............................................................................................................. ................ 1

1.1 Problem.................................................................................................................... ................. 3

1.2 Background................................................................................................................. .............. 4

1.3 Objectives of the Demonstration ............................................................................................ .. 6

1.4 Regulatory Requirements .................................................................................................... ..... 6

1.5 Improvements to the LRDP Evaluated at NAS North Island ................................................... 8

1.6 Report Organization........................................................................................................ ........ 11

2.0 Technology Description.................................................................................................... ..... 12

2.1 Description................................................................................................................ .............. 12

2.2.1 Sources of Noise ........................................................................................................ .... 14

2.2.2 Reference Tube .......................................................................................................... .... 15

2.2.3 Measurements Sensors in a Bottom-Mounted Sealed Container................................... 17

2.2.4 Mounting of the In-Tank Sensor Unit............................................................................ 18

2.2.5 Remote Test Controller.................................................................................................. 19

2.2.6 Software ................................................................................................................ ......... 19

2.2.7 Conduct of a Test....................................................................................................... .... 20

2.2.8 Data Quality Indices .................................................................................................... .. 21 Pagevi Table of Contents (cont.)

2.2.9 Summary ................................................................................................................. ....... 22

2.2 Strengths, Advantages, and Weaknesses ................................................................................ 23

2.3 Factors Influencing Cost and Performance............................................................................. 24

3.0 Site/Facility Description ................................................................................................. ....... 25

3.1 Background................................................................................................................. ............ 25

3.2 Site/Facility Ch aracteristics .............................................................................................. ...... 25

3.2.1 DEM/VAL 1: Point Loma Fuel Terminal (Third-Party Evaluation in a Bulk UST).... 25

3.2.2 DEM/VAL 2: Hunter Army Airfield (50,000-gal UST) .............................................. 26

4.0 Demonstration Approach.................................................................................................... ... 28

4.1 Performance Objectives..................................................................................................... ..... 28

4.2 DEM/VAL 1: Point Loma Fuel Terminal (Third-Party Evaluation in a Bulk UST)............. 28

4.2.1 Evaluation Procedure.................................................................................................... . 28

4.2.2 Evaluation Tank......................................................................................................... .... 31

4.2.3 Evaluation Conditions and Test Results ........................................................................ 33

4.2.4 Comparison of the LRDP Evaluated at NAS North Island and the LRDP Evaluated
Under ESTCP................................................................................................................ 34

4.3 DEM/VAL 2: Hunter Army Airfield (50,000-gal UST)........................................................ 36

4.4 Other Field Tests in Bulk USTs with the LRDP .................................................................... 39

5.0 Performance Assessment .................................................................................................... ... 40

5.1 Results of the First LRDP Evaluation..................................................................................... 4 0

5.2 Methods Evaluated .......................................................................................................... ....... 42

5.3 Results of the Leak Detection Tests at Point Loma................................................................ 43 Pagevii Table of Contents (cont.)

5.4 Performance Estimates for a Single Test (LRDP-10 and LRDP-24) ..................................... 46

5.5 Performance Estimates for More than One Test (LRDP-10-n and LRDP-24-n).................... 47

5.6 Formula to Compute the Threshold and Target Leak Rate as a Function of Tank Diameter for
the LRDP-10 and LRDP-24........................................................................................................ .. 49

5.7 How to Use the LRDP System................................................................................................ 51

5.8 Results of the DEM/VAL of the LRDP in a 50,000-gal UST ................................................ 52

5.9 Results of the DEM/VAL of the LRDP in a 132.5-ft Diameter Bulk UST at San Pedro....... 55

6.0 Cost Assessment ........................................................................................................... ......... 57

6.1 Cost Performance........................................................................................................... ......... 57

6.2 Cost Comparison to Conventional and Other Technologies .................................................. 60

6.3 Cost Avoidance............................................................................................................. .......... 62

6.4 Cost of the Parts to Manufacture the LRDP ........................................................................... 64

7.0 Regulatory Issues......................................................................................................... .......... 65

8.0 Technology Implementation ................................................................................................. . 68

8.1 DoD Need ................................................................................................................... ............ 68

8.2 Transition ................................................................................................................. ............... 68

9.0 Lessons Learned ........................................................................................................... ......... 69

10.0 Summary .................................................................................................................. ............ 71

11.0 References............................................................................................................... ............. 72

Appendix A: Points of Contact................................................................................................. A-1

Appendix B: Listings Submitted to the NWGLDE for the LRDP-10 and the Update of the
LRDP-24 ...............................................................................................................B-1 Pageviii Table of Contents (cont.)

Appendix C: Product Description a nd Product Specification Sheets.........................................C-1

Appendix D: Software User Interface Screens .......................................................................... D-1

Appendix E: Performance Equations for Ve rsion a of the LRDP-10, LRDP-24, LRDP-10-n
and LRDP-24-n............................................................................................. ..........E-1

Appendix F: Performance Equations for Ve rsions 1.0a, 1.1a, and 1.2a of the LRDP-10, LRDP-24, LRDP-10-n and LRDP-24-n .................................................................F-1

Appendix G: Performance Estimates for the LRDP-10 for Versions 1.0a, 1.1a, and 1.2a as a
Function of TLR and Tank Diameter.................................................................... G-1

Appendix H: Performance Estimates for the LRDP-24 for Versions 1.0a, 1.1a, and 1.2a as a
Function of TLR and Tank Diameter.................................................................... H-1

Appendix I: Performance Estimates for the LR DP-10 as a Function of TLR and Tank Diameter (Product Surface Area) for a Threshold Set to Yield a P D = 95% for the Selected
TLR........................................................................................................ ...................I-1

Appendix J: Performance Estimates for the LR DP-24 as a Function of TLR and Tank Diameter (Product Surface Area) for a Threshold Set to Yield a P D = 95% for the Selected
TLR....................................................................................................... ...................J-1 Pageix List of Figures

Figure 1. Low-Range Differential Pressure (LRDP) system for bulk USTs ............................1

Figure 2. LRDP system with a tapered tube installed in a 12,500,000-gal Red Hill UST .......5

Figure 3. Engineering Prototype of the LRDP system for bulk USTs .....................................5

Figure 4. LRDP system used in the ESTCP bulk UST DEM/VALs......................................13

Figure 5. In-tank portion of the LRDP system for a bulk UST with vertical walls................15

Figure 6. Shaped reference tube used in a 50,000-gal UST ..................................................16

Figure 7. Bottom container of the LRDP housing the sensor systems ...................................16

Figure 8. A time series of the LRDP illustrating that the precision is 0.0002 in....................17

Figure 9. Mounting system for a permanently installed LRDP in a bulk UST ......................18

Figure 10. Remote Test Controller: (a) photograph and (b) schematic...................................19

Figure 11. Example of the results of the data quality indices identifying that a pump was turned on during a test.............................................................................................22

Figure 12. Example of the results of the data quality indices identifying a problem with the stability of the data trend.........................................................................................22

Figure 13. Tank 175 at the Point Loma Fuel Terminal ............................................................26

Figure 14. Tank 45 at the Hunter Army Airfield......................................................................26

Figure 15. Installation of the LRDP in the Point Loma tank....................................................32

Figure 16. Comparison of the LRDP data obtained with the engineering prototype of the LRDP and the LRDP evaluated in the ESTCP project ...........................................34

Figure 17. Installation of the LRDP in the 50,000-gal UST.....................................................37

Figure 18. Top of the being installed in an 8-in.opening in a 50,000-gal UST........................38

Figure 19. Level data obtained with the LRDP-10 system for Test 10 ....................................44

Figure 20. Level data obtained with the LRDP-24 system for Test 10 ....................................44 Pagex List of Figures (cont.)

Figure 21. Level data obtained with the LRDP system over a 96-h period in a 132.5-ftdiameter tank at San Pedro......................................................................................44

Figure 22. Least-squares lines fitted to the test results of the LRDP-10 and the LRDP-24.....44

Figure 23. Difference between the induced leak rate and the volume rate measured with the
LRDP-10 and the LRDP-24 ....................................................................................45

Figure 24. Cumulative frequency distributions of the test results in a 122.5-ft-diameter bulk UST after the volume changes due to the induced leak were removed. .................45

Figure 25. Height-to-volume calibration level data in a 50,000-gal UST................................53

Figure 26. Volume data from a 24-h leak detection test with the LRDP-24 ............................53

Figure 27. Volume data obtained from 74-h of measurements with the LRDP .......................53

Figure 28. Estimate of Performance made for the LRDP in a 50,000-gal UST .......................54

Figure D-1. LRDP Main Menu: display screen allowing the user to conduct a leak detection test or to review the results of previous leak detection tests. ............................... D-2

Figure D-2. Enter New Test Parameters: display screen allowing the user to use the default testing option and test parameters shown on the screen or to enter new test parameters. ........................................................................................................... D-3

Figure D-3. Test Initiation: display screen allowing the user to start the test immediately or to
schedule the start of the te st for a later time......................................................... D-4

Figure D-4. Leak Detection Test Preparation: display screen reminding the user that valves
need to be closed before a test can be conducted................................................. D-5

Figure D-5. Leak Detection Test Setup/Monitor Screen: display screen allowing the user to
monitor the level in real time ............................................................................... D-6

Figure D-6. LRDP Test Results: display screen presenting the results of the leak detection to
the user ................................................................................................................. D-7

Figure D-7. Leak Detection Test Archives: display screen allowing the user to review previous
test results and test data........................................................................................ D-8 Pagexi List of Tables

Table 1. California Testing Options for Bulk USTs................................................................8

Table 2. Summary of the Four Methods of the LRDP System for Bulk Tanks ......................9

Table 3. Illustration of the Magnitude of the Sour ces of Errors in a 122.5-ft-Diameter Bulk UST Containing 2,100,00 gal of Fuel .....................................................................14

Table 4. Standard Test Schedule ...........................................................................................29

Table 5. Summary of the Test Results and Induced Leak Rates for the LRDP Systems .....33

Table 6. Summary of the Evaluation Temperature Conditions.............................................35

Table 7. Final Results for the Evaluation of the LRDP-10 at Point Loma............................36

Table 8. Final Results for the Evaluation of the LRDP-24 at Point Loma............................36

Table 9. Test Results for the LRDP in a 50,000-gal UST at Hunter Army Airfield.............38

Table 10. Mean and Standard Deviation of the Difference between the Measured Leak Rates (Test Results) and Induced Leak Rates for the LRDP-10 and LRDP-24................45

Table 11. Performance Estimates for the LRDP-10 and the LRDP-24 ..................................46

Table 12. Performance Estimates for the LRDP-48 and the LRDP-24 against Larger Leaks 47

Table 13. Mean and Standard Deviation of the Difference between the Measured Test Results and Induced Leak Rates for the LRDP-10-n and LRDP-24-n for n = 4, 6,
and 12 .....................................................................................................................48

Table 14. Performance Estimates Made for the LRDP-10-n and the LRDP-24-n Systems....48

Table 15. Formula to Compute the Threshold and Target Leak Rate as a Function of Tank
Diameter for the LRDP-10 .....................................................................................49

Table 16. Formula to Compute the Threshold and Target Leak Rate as a Function of Tank
Diameter for the LRDP-24 ......................................................................................50

Table 17. Example of the MDLR in gal/h (P D = 95% and a P FA = 5%) as a Function of Tank
Diameter .................................................................................................................50

Table 18. Largest Diameter Tank in which a 0.20 gal/h Leak Rate Can Be Detected as a Function of the Number of Tests Averaged Together ............................................51 Pagexii List of Tables (cont.)

Table 19. Largest Diameter Tank in which Various Leaks Can Be Detected as a Function of Target Leak Rate .....................................................................................................51

Table 20. Estimate of performance for the LRDP made for an 8-h and a 24-h test duration in a 50,000-gal UST ....................................................................................................54

Table 21. Summary of the Results of Eight 24-h Tests with the LRDP in the San Pedro Tank
after the Mean Flow Was Removed ........................................................................55

Table 22. Summary of the Costs of the Two DEM/VALs of the LRDP System....................57

Table 23. Compliance Monitoring Technology Costs for the LRDP on a Per Tank Basis.....59

Table 24. Comparison of the Cost of Testing with Monthly Monitoring and an Annual
Precision Test for Each Bulk UST for the First Year .............................................61

Table 25. Comparison of the Cost of Testing with Monthly Monitoring and an Annual Precision Test for Each bulk UST Over 1, 3, 5 and 10 Years ................................62

Table 26. Comparison of the Cost of Testing with Monthly Monitoring and an Annual Precision Test for 15 bulk USTs Over 1, 3, 5 and 10 Years ..................................62

Table 27. Comparison of the Cost of Testing with Monthly Monitoring and an Annual Precision Test for 300 bulk USTs Over 1, 3, 5 and 10 Years ................................62

Table 28. Parts List for the LRDP...........................................................................................64 Pagexiii 

### Acronyms

AST Aboveground storage tank

CERF Civil Engineering Research Foundation CERL Construction Engineering Research Laboratory (Army)

DESC Defense Energy Support Center (DESC) DoD Department of Defense

EPA Environmental Protection Agency ESTCP Environmental Security Technology Certification Program EvTEC Environmental Technology Evaluation Center

I/F Interface
MDLR Minimum Detectable Leak Rate MODBUS Industrial Networking System that uses RS232 Serial Master-Slave
Communications

NAS Naval Air Station NFESC Naval Facilities Engineering Service Center NWGLDE National Work Group on Leak Detection Evaluations

P D Probability of Detection

P FA Probability of False Alarm

P MD Probability of Missed Detect PLC Programmable Logic Controller
PSA Product surface area

RTD Resistance Temperature Device

TLR Target Leak Rate

UST Underground Storage Tank

VR Volume Rate Pagexiv 

### Acknowledgments

The LRDP team would like to acknowledge and thank the fuel farm directors and their staff at the Point Loma Fuel Terminal, the H unter Army Airfield, the Defense Energy Office, Los Angeles (San Pedro), and the NAS North Island for making their facilities available for the DEM/VALs of the LRDP system, and for coor dinating and supporting the DEM/VALs. We would also like to acknowledge the input and support of the Defense Energy Supply Center (DESC) and Endress+Enhauser Coggins Systems. Ken Wilcox Associates, Inc., performed the third-party evaluation of the LRDP. The LR DP was initially developed by NFESC and Vista Research with funding from the Pollution Abatement Ashore Program, which is sponsored by the Environmental Protection, Safety and Occupa tional Heath Division (N45) of the Chief of Naval Operations, and from Vista Research. The work described in this report was funded through the Environmental Security Technology Certification Program (ESTCP) and is entitled, “Validation of the Low Range Differential Pressu re (LRDP) Leak Detection System for Small Leaks in Bulk Fuel Tanks.” A full list of contacts is included in Section 8 of this report.

The LRDP team would like to especially thank Dr. Jeffrey Marqusee and Dr. Robert Holst for their support.

Project Manager: Leslie A. Karr, REM
NFESC

Project Engineers: William R. Major
NFESC

Dr. Vincent F. Hock
CERL

Technical Director: Dr. Joseph W. Maresca, Jr. Vista Research, Inc.

Design/Field Engineers: James W. Starr, P.E. Vista Research, Inc.

Gary A. Hayter Vista Research, Inc.1 

### 1.0 Introduction

The Low Range Differential Pressure (LRDP) system is an innovative technology that was developed for the reliable detection of small fuel leaks in the bulk underground storage tanks (USTs) that are owned or operated by the Departme nt of Defense [1-2]. If a tank is leaking, the LRDP quantitatively measures the leak rate in gallons per hour, the quantity of regulatory interest. The LRDP system can be used to te st tanks ranging in capac ity from 50,000 gallons to 12.5 million gallons and will work fo r tanks with vertical and/or curved walls. The LRDP is a fully automatic, mass-based system, which is easy to install and use. The LRDP system can be permanently installed in a tank and used for on-li ne monitoring and precision (tightness) testing. It can also be used as a portable system for pe riodic testing of any tank in the fuel farm. The
duration of a test can be either 10 or 24 h depending on the size of the tank and the performance required.

The LRDP, which is shownin Figure 1, is the only intank system that has the performance to address both the monthly monitoring andannual precision test leakdetection regulatory requirements for bulk USTs [3-5] without requiring the installation, operation and cost of a second system. Not only is the LRDP the only system that can cost effectively meet both requirements, it can meet these requirements with a very low probability of false
alarm. It is also the only system that can conduct an overnight test. The technology is not site-specific, and the performance of the tec hnology is not affected by site geology or topographic factors. Th e system can be implemented in a bulk tank of any size and of any configuration. It can also be readily integrated into th e DoD tank farm Fuel Accounting System (FAS) and other fuel management and handling systems.

The LRDP technology also provides facility operato rs with valuable tank replacement and cleanup cost avoidance information, because the probabil ity of a missed detecti on, the probability of a false alarm, and the confidence intervals on the m easurement of the flow rate due to a leak are Figure 1. Low-Range Differential Pressure (LRDP) system for bulk USTs.2 known for the LRDP. With this information, an es timate of the life-cycle cost of the technology can be made. Significant cost savings can be r ealized, because the performance of the LRDP is high, and the recurring costs associated with operation of the system are low.

As part of the Environmental Security Technology Certification Program (ESTCP), the LRDP technology was demonstrated and validated (DEM/VAL) in two 2,100,000-gal, field-erected, bulk USTs and in a 50,000-gal, shop-fabricated UST, all owned and operated by the DoD. One
of the bulk USTs was located at the Point Loma Fuel Terminal, San Diego, California, and the
other was located at the San Pedro Fuel Facili ty, Defense Energy Office, Los Angeles. The DEM/VAL conducted on the 50,000-gal UST was conduc ted at the Hunter Army Airfield (a subunit of Fort Stewart), Savannah, Georgia. Th ese technology demonstrations were performed by the Naval Facilities Engineering Service Center (NFESC), Port Hu eneme, California, the U. S. Army’s Construction Engineering Research Labo ratory (CERL), Champaign, Illinois, and their industrial partners, Vista Re search, Inc., Sunnyvale, Califo rnia, and Vista Engineering Technologies, L.L.C., Kennewick, Washington. The ESTCP is a corporate DoD program that promotes innovative, cost effective environm ental technologies through demonstration and validation at DoD sites. This proj ect was performed as part of the Compliance ESTCP Thrust
Area under Improved Leak Detection and Prevention Technologies for Underground Storage Tanks (USTs) and Underground Pipelines . The main points of contact for this project are listed in Appendix A.

The objective of the DEM/VAL conducted at the Po int Loma site was to obtain an independent third-party evaluation of the performance of the LRDP as an on-line mon itoring and precision test leak-detection system. This evaluation was origin ally planned for the San Pedro site, but a small flow across the pipeline valve prevented the ev aluation from being conducted at this site. However, the limited number of tests conducted at San Pedro indicated that the LRDP had the capability for meeting the regulatory requirements for precision testing and monthly monitoring.

Before a method can be used, it must be evaluate d for performance by an independent third party and listed by the National Work Group on L eak Detection Evaluations (NWGLDE). The evaluation was performed by Ken Wilcox Associates , Inc. (KWA) at the Point Loma site. The
evaluation was conducted in a 122.5-ft-diameter bul k UST in accordance with a standard test procedure following EPA guidelines that was develope d specifically for bulk storage tanks [6, 7]. This procedure was reviewed and approved by the NWGLDE, a national group of regulators, which is sponsored by the EPA, to simplify the certification of leak detection methods by the
states. The NWGLDE reviews the third-party evaluations of leak detection methods for completeness and accuracy. If the evaluation is complete and accurate, the NWGLDE will list the method. This listing allows the states, which develops a list of approved methods that can be used for leak detection in their state, to approve methods without extensiv e review. If the method is not listed by the NWGLDE, the states will not approve or use the method. The listing gives a description of the method, its performance, and the limitations on its use.

The results of this performance evaluation for an overnight test (10 h) an d for a 24-h test have been submitted for review and update of the curr ent LRDP listings by the NWGLDE so that the system can be used by the states to address thei r leak detection regulator y requirements [8-15]. A draft of the updated listing is presented in A ppendix B. The performance of the system is presented in terms a probability of detection (P D ) of a given target leak rate (TLR) in gallons per3 hour and a probability of false alarm (P FA ), where the P D = 95% and the P FA < 5%. The TLR is usually specified by the regulatory requirements and may be different from state tot state. The TLRs are typical 1, 2, or 3 gal/h for monthly monitoring and 0.2 gal/h for precision testing.

The objective of the DEM/VAL conducted at the Hunt er Army Airfield site was to demonstrate the technology in a 50,000-gal UST with cylindr ical walls. This DEM/VAL consisted of a limited number of tests showing th at the system was capable of meeting the EPA’s regulatory requirements for monthly monitoring at 0.2-gal/h. A third-party evaluation was not performed for this type of UST. If the LRDP is to be used for testing cylindrical USTs , a third-party evaluation will be required.

This technology has been successfully transfe rred to industry. Leak-detection products and services based on this technology are commercially available through Vista Research, Inc.; these products and services include (1 ) on-line, permanently instal led monitoring systems and (2) tightness testing services. Pr oduct description and product speci fication sheets are included in Appendix C.

1.1 Problem

The DoD owns and operates over 300 bulk USTs. They range in size from 100,000 gal to over 4,000,000 gal, and have diameters up to 135 ft. Over half of these bulk USTs are located in California. The DoD also owns twenty 12,500,000-ga l USTs in Red Hill, Hawaii. In addition, the DoD owns and operates many thousands of large shop-fabricated USTs (e.g., 50,000-gal) throughout the country. Until recently, unlike th e small USTs found at petroleum service stations, the bulk tanks had no re gulatory requirements for periodi c leak detection. The federal regulations deferred bulk USTs from the regular annual tightness test or monthly monitoring tests that other smaller USTs must undergo. However, various states have implemented regulations or testing guidelines, which have the strength of regul ations, for bulk USTs. This presents a unique problem for DoD, because DoD is the only ow ner of bulk USTs. Because of increasing remediation and cleanup costs due to tank le akage and the implementation of regulatory guidelines and requirements, the DoD is in need of one or more leak detection systems to meet
their environmental needs.

Prior to the start of this ESTCP project, the only system that could meet the Federal UST regulatory requirements was a tracer method in which a unique tracer could be added to the fuel. However, the cost of using this technology is ve ry expensive, even for a single annual tightness test, and is not cost effective for monthly mon itoring. The use of other types of tracer methods, which use one or more constituent components of the fuel as tracers, do not work, because the background contamination results in too many fa lse alarms. While acoustic systems have application for aboveground storage tanks (ASTs), they have not been used for bulk USTs and do not have the performance to meet regulatory gui delines for bulk USTs. Volumetric systems, comprised of level and temperature sensors like those used on the smaller USTs at petroleum service stations, cannot adequately compensate fo r the thermal expansion and contraction of the
fuel to be considered. While statistical invent ory reconciliation methods are approved and widely used at service stations, their pe rformance, even for these small tanks, is suspect by the regulatory community. Regardless, of performance, the fuel farm UST systems are not adequately4 configured for leak detection, and it would be very expensive to retr ofit the fuel farm to implement this approach.

The technology of preference for DoD’s bulk UST owners and operators is an in-tank, massbased system. The performance of a convent ional mass measurement system, however, is seriously limited by three factors an d cannot be used to address th e regulatory guidelines for both monthly monitoring and periodic precision testing unless these lim itations are fully addressed. The first limitation is that a conventional system, which uses a differential pressure sensor with sufficient dynamic range to measure level changes over the full vertical ex tent of the tank, lacks
the precision required to detect small leaks unless sp ecial-purpose, delicate and expensive sensors are used. The second limitation is that, in a tank with a variable cross-sectional area, thermal influences can cause large changes in volume, which are not compensated by a differential pressure sensor. The third limitation is the errors produced by the thermal expansion or
contraction of both the instrume ntation and mounting system.

The LRDP system was developed to address thes e limitations. The reference tube addresses the first limitation, and a “shaped” tube addresses the second limitation; the bottom-mounted sensors and the special bellows mounting system used in the LRDP system described below address the
third limitation.

1.2 Background

The LRDP system was developed to address the re quirements for leak detection specified in the Navy’s Environmental Quality Research and De velopment Requirement No. 2.iii.2.a “Improved Leak Detection and Prevention Technologies fo r Underground Storage Tanks (USTs).” The LRDP system provides the DoD a method of leak detection for bulk USTs that

• will be in compliance with local, stat e and federal regulatory requirements,

• has with sufficient performance to detect a leak, if one were to occur, so that the environmental damage and the costs associat ed with cleanup and remediation could be minimized,

• is reliable enough to be used, because it does not have false alarm problems and could be used without any significan t impact to operations, and

• is very cost effective, because it can be installed, operated, and maintained over time less expensively than other technologi es, and could be effectively us ed to minimize the cost of cleanup and remediation by early detection of an d quantification of the size of a leak. An estimate of the cost savings associated with the use of this tec hnology is between $500 M and $1 B.

All four of these objectives are based on the pe rformance of the method, and the LRDP system has more than sufficient performance to meet the compliance, detection, operation, and cost objectives required of a leak dete ction technology needed to satisfy DoD’s environmental needs.5 The LRDP, shown in Figure 2, was originally deve loped for detection of leaks in the world’s largest USTs [2]. The 20 Red Hill tanks, whic h are owned and operated by the U. S. Navy, are buried over 100 ft deep in the hills above Honolulu, Hawaii and contain 12.5 million gallons of fuel. Each tank is 100 ft in diameter and 250 ft in height. In 1996, an LRDP was installed in one of the Red Hill tanks (Tank 16) for demonstration purposes. (Another LRDP has recently been installed in Tank 9 (March 2001) and a third-party evaluation has been completed [16]).

While waiting for fuel to be added to Tank 16 at Red Hill, a second LRDP was built and installed in a 88-ft-diameter, 600,000-gal UST at the NAS North
Island Fuel Farm. The first implementation of this system, which is shown in Figure 3, was developed for cylindrical tanks with vertical walls and evaluated for performance by KWA in a 600,00-gal UST at the NAS North Island
Fuel Farm in 1998. The LRDP was listed by the NWGLDE for use as a precision leak-detection system for bulk USTs using either a 24- or 48-h test, a waiting period of 24 h, and an average of a set number of tests (1, 4 or 5 tests) [1, 5]. The performance es timates made in this th ird-party evaluation were contaminated by a small inflow (~0.1 gal/h) that occurred during the evaluation; this inflow introduced a small bias and degraded the perfor mance of the system over what it should have been. Even so, the performance was excellent and more than sufficient to meet regulatory requirements for both monitoring and precision tes ting. The limitations and constraints imposed on the use of the LRDP by the
NWGLDE as a result of this first
evaluation were addressed and
eliminated in the evaluation described in this report.

The main difference between the LRDP system installed at NAS
North Island and the one used in this
evaluation is the size and location of
the sealed container at the bottom of
the reference tube. The
measurement sensors in the sealed
container were the same for both systems. Since the fuel in both Figure 2. LRDP system with a tapered tube installed in a 12,500,000-gal Red Hill UST.

Figure 3. Engineering Prototype of the LRDP system for bulk

USTs6 versions of the reference tube extended from th e bottom of the tank to the product surface and had
an identical cross-sectio nal area, identical performance is e xpected and was verified by a side-byside comparison of the improved version of the LRDP system evaluated during the Point Loma
DEM/VAL.

1.3 Objectives of the Demonstration

The objective of this ESTCP project was to de monstrate and validate (DEM/VAL) a reliable, cost-effective leak-detection system for monthly m onitoring and periodic pr ecision testing of the
bulk underground storage tanks (USTs) with vertical walls that are owned and operated by the DoD. This project was an expansion of the pr evious testing and regulat ory approval obtained in
California for the LRDP on an 88-ft-diameter bul k UST at NAS North Island [1]. The present tests were designed to demonstrate the system on larger tanks and to obtain regulatory approval for use of the system as an on-line monitoring system and with a test duration of 24 h and a
second test duration shorter than 24 h (i.e., 10 h). The output of th e project is an alpha-prototype of the LRDP leak detection system (1) that is ready for pre-production te sting by industry and (2) that has been evaluated for performance by an independent third party following a standard test procedure developed by the EPA and approved by th e NWGLDE. The third-party evaluation
will be submitted to the NWGLDE for review and inclusion on a national list of leak detection methods, which are ready for use by the states. An additional objective was to demonstrate that the LRDP system also can be used to test th e smaller, 50,000-gal underg round storage tanks with
curved walls.

Unlike many other environmental technologies, th e approach to DEM/VAL is prescribed by the EPA. In 1988, the EPA developed a set of st andard test procedures for estimating the performance of various types of leak detection methods. In 1996, a standard test procedure was prepared for mass-based or volumetric leak detect ion methods for bulk USTs [6]. The results are presented in terms of a volumetric target leak rate (TLR) in gallons per hour, a probability of detection (P D ), and a probability of false alarm (P FA ). The regulatory requirements of each state are specified in terms of P D , P FA , and TLR, where the state sets the TLR, and at a minimum, the

P D must be equal to or better than 95% and the P FA must be less than or equal to 5%. The standard test procedure for mass-based systems allo ws for the scaling of performance for verticalwall USTs with surface areas up to 250% of the surface ar ea of the UST used in the evaluation. The standard test procedure places a number of constraints on the scaling of performance. First, the performance of the method could not be scaled to a target leak rate less than 0.2 gal/h, and second, the smallest UST that the method is ap proved for use has a capacity of 50,000 gal.

1.4 Regulatory Requirements

The UST regulation, issued in 1988 by the EPA, deferred the requirements for testing bulk or field-erected USTs for leaks [3]. The main reas on for the deferral of field-erected USTs was the lack of any technologies in 1988 th at could reliably test these larg e tanks for leaks. Only the shop-constructed USTs, which are typically used at service stations a nd have capacities of 50,000 gal or less, were strongly regul ated. In contrast, the large field-erected USTs, which have capacities between 100,000 to 12,500,000 gal, did not n eed to meet the rigorous leak-detection performance standards for monthly monitoring or annual tightness testing established for small USTs [3].7 The performance of a leak detection system with a P D = 95% for a specified TLR and a P FA = 5%
is called the minimum detectable leak rate (MDLR), where the MD LR equals the specified TLR. This jargon should not be confused with the smalle st leaks that can be detected. Leaks smaller than the TLR can be detected, but the P D may be less than 95% (even if the threshold is not changed) or the P FA may be less than 5% (by changing the threshold). While many leak detection systems are operated at this level of performan ce, the chief advantage of computing the MDLR for each method, even if they are not operated at th is level, is that the performance of different methods can be easily and directly compared.

The UST regulation, which was required to be implemented by the states, requires that all regulated USTs be tested for leaks on a monthly basis with a leak det ection system capable of detecting a leak as small as 0.2 gal/ h with a probability of detection (P D ) of 95% or greater and a probability of false alarm (P FA ) of at 5% or better. Between the issuance of the UST regulation on 22 December 1988 and the 10-year period that allowed for tank owners to meet the UST upgrading requirements (by 22 December 1998), tightne ss (or precision) tests of the USTs were allowed in lieu of the monthly monitoring. Wh ile the testing schedule prescribed by the EPA regulation allowed intervals of up to 5 years between te sts, most states required annual tightness testing if this option was selected by the tank ow ner. To meet the regulatory requirements for a tightness test, a leak detection system capable had to be capable of detecting a leak as small as 0.1 gal/h with a P D > 95% and a P FA < 5%. During this 10-year period, the states struggled with how to test bulk USTs and what performance standa rds should be required. Until the mid- to late1990s, bulk USTs were rarely tested for leaks; large i nventory imbalances were the primary mode for identifying a leak. The volumetric systems that were typically used to meet the performance standards required for the small regulated USTs found at service stations could not meet these same standards on the bulk USTs. The LRDP, a mass-based system, was developed in response
to the need for detection of leaks in bulk US Ts owned by the Department of Defense (DoD).

During the late 1990s, California, where the majo rity of all of DoD’s bulk tanks are located, developed regulatory guidelines fo r testing bulk tanks. Since the DoD owns almost all of the bulk USTs in the United States, the California guidelines were mainly prepared for DoD compliance.

The basic option for testing USTs, regardless of size, is to meet the 0.2-gal/h monthly requirement in the EPA UST regulation. This option, included by California as Option 1, is overly stringent and does not have a low enough P FA for routine monitoring. As a consequence, California developed other options that included a precision test at 0.1 gal/h, which is not realistic for testing bulk USTs [4].

Two of the ten testing options (Options 7, 10) developed by Calif ornia were based on the input
from discussions from NFESC and Vista Resear ch and the results of the first third-party evaluation of the LRDP [4] conducted at North Is land. Both of these options required monthly monitoring and a periodic precisi on test. These performance guide lines are stringent, consistent with bulk operations, and achievable. These tw o guidelines are summarized in Table 1. The other options are variances of the UST leak dete ction performance standards issued for the small
USTs found at service sta tions and are not generally consiste nt with the design and operation of
bulk USTs. The State of Califor nia requires that each leak det ection system be third-party8 evaluated, be approved and listed by the NWGLDE , and be approved and listed on the California
list.

As will be discussed in Section 5, the LRDP meets all of these standards. However, any leak detection system that can meet Option 1 can also meet Options 7 and 10, so Option 1 would not be the first choice by the fuel farm operator unless such level of protection is really needed or the
standard can be met with a much lower P FA than 5%. Furthermore, the LRDP system is the only on-line monitoring mass-measurement system that can meet both the monthly monitoring and precision testing guidelines in Options 7 and 10 for all bulk USTs owned by DoD.

Table 1. California Testing Options for Bulk USTs [4]

California Testing Options Mo nthly Monitoring Test Precision (Tightness) Test Option 1
Target Leak Rate – gal/h 0.2 gal/h

P D - % > 95%

P FA - % < 5%
Testing Schedule – years 1 month

Option 10
Target Leak Rate – gal/h 0.3 to 1.0 gal/h 0.2 gal/h

P D - % > 95% > 95%

P FA - % < 5% < 5%
Testing Schedule – years 1 month 1 year

Option 7
Target Leak Rate – gal/h 1.0 to 2.0 gal/h 0.2 gal/h

P D - % > 95% > 95%

P FA - % < 5% < 5%
Testing Schedule – months 1 month 6 months

Because of the particularly hi gh performance achieved by the LR DP, the State of California would not allow the system to be used as de signed (Version a in the NWGLDE listing), even though it met these performance guidelines. The Stat e limited the target leak rate to twice the minimum detectable leak rate (MDLR) achieved by the system (Versions 1.1a or 1.2a). For most UST sizes, the P FA << 5% for the LRDP.

1.5 Improvements to the LRDP Evaluated at NAS North Island

The work was accomplished in the following four tasks:

• Task 1 - Prepare and execute work plan

• Task 2 - Design, assemble, integr ate and checkout alpha prototype

• Task 3 - Conduct system DEM/VAL and evaluati on testing at selected DoD installations Task 4 - Prepare technology transfer package and implementation plan9 All four tasks were successfully completed; the technology has been transferred to industry and is being offered commercially to address DoD’s bulk UST environmental needs.

Four testing methods of the LRDP system were evaluated for performance. For each method, one of four thresholds can be used to detect a specif ic target leak rate (TLR) or to operate with a specific P FA . The TLR is usually specified by the regulatory agency. The P D = 95% for all thresholds and all methods used by the LRDP. Th e list distinguishes each threshold by a unique version number. Table 2 summarizes the four methods. Two of the methods require only one test, and two of the methods require the averagin g of up to 12 tests. The name of the method
contains the duration of the test in hours and the number of tests to be av eraged. The LRDP-10 is implemented with a 10-h test, a nd the LRDP-24 is implemented w ith a 24-h test. The LRDP-10- n is a test that requires the averaging of “n” test s. The number of tests to be averaged depends on the required performance. This type of method is normally used to meet the 0.2-gal/h precision (tightness) test requirement for th e larger tanks owned by DoD. A ny or all four of these methods can be used in combination to address regulator y requirements. For example, the LRDP-10 might be used to address the monthly monitoring re quirement, and the LRDP-24 might be used to address the precision test requirement.

Table 2. Summary of the Four Methods of the LRDP System for Bulk Tanks

Name of Test Method Type of Test Test Duration Number of Tests Averaged Together LRDP-10 Monitoring, Precision 1 10 h 1 test
LRDP-10-n Precision 1 10 h 1 < n < 12 tests LRDP-24 Version A Monitoring, Precision 1 24 h 1 test
LRDP-24-n Version A Precision 1 24 h 1 < n < 12 tests

1 Can be used to address the regulatory standards for a 0.20-gal precision test, when the monthly monitoring requirement is 2.0 gal/h or less.

Many important improvements to the LRDP eval uated at NAS North Island have been made under ESTCP. As a result of these improveme nts, the LRDP is ready for implementation throughout the DoD. However, none of these impr ovements effected any changes to those parts of the system that control performance. For ex ample, the same differential pressure sensor was used in both systems. Some of these improvements are:



## • The notebook computer and data acquisition system were replaced with a field-worthy remote test controller, which collects data, evaluates data quality, analyzes test results,
and stores the results.



## • The system was made fully automatic, and the software user interfa ce was made easy to

use.



## • The system was originally approved as a porta ble system and can now also be used as a stand-alone system for on-line, real-time, in-tank monitoring.



## • A special set of data quality indices were developed and tested to insure the reliability of
each test result.



## • The in-tank sensor unit was redesigned for eas y installation and now fits into a standard 8-in. diameter opening of a tank of any diameter and any product depth.10 

## • The LRDP can be easily interf aced with base fueling operations, including the FAS, and
can be used for both leak dete ction and inventory monitoring



## • The evaluated performance of the LRDP is 20% better than originally determined in the first evaluation, and the performance limitati ons (e.g., a 24-h waiting period) have been
removed.



## • The monthly monitoring regulatory guidelines can be met with the LRDP using a 10-h test, which is short enough to be conducte d overnight. For many of DoD’s bulk USTs, the LRDP also be used to address the precis ion testing guidelines with a 10-h test. The LRDP can be used to address the precisi on testing guidelines for the remaining bulk
USTs with a 24-h test.



## • The electronics are housed in an explosi on proof container and meet Class 1, Div 1
Standards.



## • With changes to the design of the referen ce tube, the LRDP was adapted for use in testing 50,000-gal USTs and other USTs with curved walls.

The main attributes of the LRDP system are summarized below:



### • The LRDP is directly inserted into a standa rd 8-in.-diameter openi ng in the tank that is being tested or monitored.



### • The LRDP can be used to perform a leak de tection test without removing fuel from the
tank.



### • The LRDP can be used to test USTs with both vertical and curved walls.



### • The output of a leak detection te st is easy to interpret, becau se it is a direct measurement of the leak rate in gallons per hour, the qua ntity of regulatory and engineering interest.



### • Because the LRDP system is a mass-based system, it inherently compensates for the thermal expansion or contraction of the fuel in the tank during a test. Furthermore, accurate tests can be initiated without a long pre-test waiting period that are needed by other systems to allow the horizontal temper ature gradient to stabilize throughout the
tank.



### • The special mounting system eliminates ther mally induced movement of the reference tube during a test.



### • Thermally induced drift of the differential pressure sensor is virtually eliminated,
because it is mounted in a sealed container at the bottom of the tank.



### • Because the differential pressure sensor used to measure level (volume) changes in the tank needs a dynamic range of only 1 in. (rather than the total heig ht of the tank, like other mass-based systems), the LRDP has the precision (0.0002 in.) to detect very small leaks in large-diameter tanks.



### • The system is self-calibrati ng, and the performance and func tionality of the LRDP can easily be checked between leak detection tests.11 1.6 Report Organization

This report is organized following the ESTCP fi nal report outline. Section 2 provides a description of the technology. S ection 3 describes the sites/facilities where the DEM/VALs were conducted, and Section 4 describes the demonstration approach. Section 5 presents the results of the DEM/VALs and the performance of the LRDP. Section 6 presents a cost assessment of the technology. Section 7 describes the regulatory interactions. Section 8 describes how the technology can and is being implemented. Section 9 describes the lessons learned that might be useful for other demonstrations, and Section 10 briefly summarizes the results of the project.12 

### 2.0 Technology Description

A description of the LRDP is presented below.

2.1 Description

The LRDP system is a mass-based, leak-detect ion system for use in bulk USTs containing petroleum fuels. If a tank is leaking, the LRDP quantitatively measures the leak rate. The LRDP system can be used to test tanks ranging in capacity from 50,000 gallons to 12.5 million gallons
and will work for tanks with vertical and/or cu rved walls. Its modular design makes it easy to install in a tank of any depth or diameter. It can be installed through a standard 8-in.-diameter opening without removing any fuel from the tank. The LRDP system can be permanently
installed in a tank and used for on-line monitoring and precision (tig htness) testing. It can also be used as a portable system and be moved from tank to tank for periodic testing of any tank in the fuel farm. The former is the preferred c onfiguration, because of th e regulatory requirements for monthly monitoring. A test can be completed in 10, 24, or 48 1 hours. Better performance is
achieved as the duration of the test is increased. For almost all app lications, a 10- or 24-h test is sufficient; a 48-h test can be used if enhanced performance is needed.

The LRDP can be used to test all three types of large, regulated, fuel USTs owned by the DoD: (1) bulk, field-erected USTs with vertical walls, (2) very large bulk USTs like those at Red Hill, and (3) large, shop-constructed cylindrical USTs (e.g., 50,000-gal tanks). The largest bulk USTs owned by DoD have diameters of ~134 ft a nd capacities of 2,000,000 to 4,000,000 gal. The largest USTs are located in Red Hill and have a capacity of 12,500,000 gal; these tanks are 250 ft in height and 100 ft in diameter; the top and bottom 50 ft of the tank is dome shaped. The 50,000-gal USTs are nominally 10.5 (to 12.0) ft in diameter and 77.2 (to 59.0) ft in length.

The pre-production prototype of the LRDP system, developed in this ESTCP project and shown in Figure 4, is a fully automatic, computer-controlled system. It is comprised of (1) an in-tank level sensing unit, (2) a local embedded remote test controller to implement a test and to collect and analyze the data from a test, and (3) a host co mputer to initiate, display, report, and archive
the results of a test. The level-measurement sens or is an industrial di fferential pressure (DP)
sensor that is located in a seal ed container at the bottom of the in-tank sensing unit. A test is initiated by an operator using the host computer. The remote test controller, located in close proximity to the tank, automatica lly operates the LRDP system. A test report is generated upon completion of the test. The LRDP system is co mpatible with the DoD Fuels Accounting System (FAS) and can be integrated with FAS to test th e tanks in a fuel farm or bulk storage terminal.

1 A 48-h test was evaluated for performance at NAS North Island. The performance obtained for the 24-h test in the second evaluation conducted as part of this ESTCP project wa s better than that obtained for the 48-h test in the first evaluation. This result is a consequence of contamination of the first results with a small inflow that occurred during the evaluation. If a 48-h test were performed, it would have better performance than a 24-h test. It should only be used, however, if the results of the 24-h test are inconclusive and better performance is needed. Although better performance will be achieved with a 48-h test, th e performance claim can be no better than the 24-h test, unless it is re-evaluated.13 The in-tank level sensing unit of the LRDP system that has been designed for tanks with vertical walls (that is, upright cylinde rs with flat bottoms) is comprised of the following:

(1) a reference tube that extends from the t op to the bottom of the tank

(2) a valve , located near the bottom of the tank, w ith which to open and close the tube

(3) a sealed container mounted at the bottom of the reference tube

(4) a differential pressure sensor , mounted in a sealed contai ner located at the bottom of the tank, that measures the difference between the level of liqui d in the tank and that in
the reference tube

(5) two pressure sensors , mounted in the sealed container, that can be used to measure the level and specific gravity of the fuel in the tank

(6) a temperature sensor , mounted on the differential pressure cell in the sealed container,
that can be used to compensate the differential pressure sensor or the pressure
sensors for temperature, and/or to
measure the temperature of the fuel
at the bottom of the
tank

(7) electrical wires (4-20
ma contained in a sealed conduit) that
connect the bottommounted sensors to the data acquisition system outside the tank, and

(8) a special bellowsmechanical mounting system to eliminate
thermal movement of
the reference tube and transducer enclosure.

The fuel in the tank is allowed to enter or leav e the reference tube thr ough a valve located at the bottom of the tube. The valve is opened and closed electronically (a func tion that can also be done manually). Except for a test, the valve is le ft in the open position. This allows fuel from
the tank to enter the reference tube until the level of liquid is the same in both. When the valve is open, i.e., when the level of liquid in the tube is identical to that in the tank, the precision and accuracy of the LRDP system can be checked. When the tank is to be tested, the valve is closed, isolating the fuel in the tube from the fuel in the rest of the tank. With the exception of a level change due to a leak, the level of the fuel in the reference tube mimics the level of the fuel in the
tank. The DP sensor measures the difference in th e levels of fuel between the reference tube and Fi g ure 4. LRDP s y stem used in the ESTCP bulk UST DEM/VALs.14 the tank. If the rate of change of the level in the tank (which can be expressed in terms of gallons per hour based on a height-to-volume conversion from the tank’s strapping table) exceeds a pre-set detection threshold, the tank fails the test.

2.2.1 Sources of Noise

Ambient noise—real and apparent volumetric ch anges not associated with a leak—may, unless compensated, mask the presence of a leak or lo ok like a leak. The LRDP compensates for the important source of ambient noise. Since it is kn own that the reference tu be is not leaking, and since level changes in the tube mimic those in the tank, the ambient noise is removed from the
test result. Because the LRDP is a mass-base d system, it compensates automatically for the greatest source of noise—the level (volume) changes produced by thermal expansion and contraction of the fuel. Note that this approach must be modified for tanks with curved walls (e.g., horizontal cylinders, or vertical cylinders with spherical tops and bottoms). To address this type of tank, the LRDP system incorporates a second design in which the constant-diameter reference tube is replaced by a variable-shaped t ube that mimics the cro ss-sectional changes in the tank’s geometry [17]. Such a reference tube was used to test the 50,000-gal USTs during the Hunter Army Airfield DEM/VAL.

High performance is achieved with the LRDP sy stem, because the novel design of the in-tank sensing unit results in (1) a ve ry high precision for making level measurements with an off-theshelf differential pressure sensor and (2) effective compensation of the thermally induced changes of the fuel, the sensors, the tank, and the mounting system. For bulk tanks, both high precision and effective compensation is requ ired to meet regulatory guidelines.

Table 3. Illustration of the Magnitude of the Sources of Errors in a 122.5-ft-Diameter Bulk UST Containing 2,100,00 gal of Fuel

Level Change Temperature Change Volume Change
over 24 h Volume Error
24-h Test* MDLR**
24-h Test
(in.) ( o C/h) (gal) (gal/h) (gal/h)

Precision 0.001 1.50 0.062 0.22 Thermal Expansion or
Contraction of Jet Fuel 0.01 504.00 21.00 75.39

6-in. of exposed manway by air
temperature 0.10 22.04 0.92 3.30

DP sensor by fuel temperature 0.01 17.63 0.73 2.64 DP sensor/electronic equipment by air temperature 0.10 176.33 7.35 26.38

Total without Thermal Expansion
or Contraction 7.44 26.71

Total 22.28 79.99 * Assumes 24 degrees of freedom in regression line. ** TLR for a P D = 95% and a P FA = 5%.

Table 3 illustrates, for the conditions given, the magnitude of the errors in a 122.5-ft diameter
UST and the MDLR that would result if these errors were not compensated. These conditions are modest and do not represent extreme conditions . Unless these thermally induced sources of noise are compensated by the leak detection syst em, leaks as small as 0.2 or even 1.0 or 2.0 gal/h would be masked by these large volume changes and would not be detected. Conversely, unless15 these volume changes are not compensated, they might be confused with a leak and lead to false declarations (i.e., false alarms). It is the latter that tends to pla gue systems and results in a loss of confidence in the system and ultimately in not using the system by fuel farm operators.

As can be seen in Table 3, any one of the erro rs, if not compensated, can be large enough to prevent the method from meeting the regulatory requirements. For example, if a method has a precision of 0.001 in., this results in a volume change of 1.50 gal over a 24-h period in a 122.5- ft-diameter tank. This assumes that a regression line is fit to data in and that there are 24 degrees of freedom. Assuming this was the only error, the method would have a MDLR of 0.22 gal/h.

In a tank with a capacity of 2,100,000 gal, a 0.01 o C/h change in temperature results in a 21.00 gal/h volume change. If this thermally induced volume change is not compensated to within

0.01 o C/h, then the error would be too large to use this approach for leak de tection. This is the main reason mass-based systems, rather than volu metric (level and temperature) systems, are used for bulk USTs. A mass-based system compen sates this error directly as part of the
measurement. Even if a volumet ric system can compensate to 0.001 o C/h, a performance of 7.54 gal/h would result, which is also too large for routine use.

Exposed parts of the tank upon which the leak det ection system is mounted will change elevation by thermal expansion and contrac tion of the mounting system. Di urnal temperature swings of

over 15 o C are not uncommon. An estim ate of the thermally induced level change based on a temperature difference of 2.4 o C over a 24-h period (0.1 o C/h) on an exposed section of manway of 6 in. results in 0.92 gal/h erro r. This error is quite comm on for improperly mounted systems and would prevent the reliable det ection of leaks of 3.3 gal/h if th ere were no other errors. As shown in Table 3, the thermally i nduced changes in a differential pr essure cell or it electronics can result in apparent height changes that are also very large if not compensated.

All of these potential so urces of error must be reduced or compensated to a bout a third of the target leak rate required for regulatory compliance. In California, this means that monitoring methods must compensate to within 0.3 gal/h to meet a monthly monitoring requirement of 1.0 gal/h and to within 0.06 gal/h to meet a periodic (semi-annual or annual) precision test of 0.2 gal/h. The LRDP compensates for over 98% of all of the thermally induced changes listed in Table 3, and because of the reference tube, the LRDP can achieve a very high precision with a DP sensor (0.0002 in.).

2.2.2 Reference Tube

The key components of the in-tank sensing unit are a reference tube that spans the full usable height of the
tank and a sealed container at the bottom of the tube (and tank) that houses the measurement sensors. Unlike most other mass-based systems, the LRDP Figure 5. In-tank portion of the LRDP system for a bulk UST with vertical walls.16 system does not require a high-precision DP sensor nor does it require special compensation for changes in the temperature of the pressure sensor itself. Instead, the precision of the LRDP is controlled by the reference tube. The reference tube, because it greatly reduces the dynamic range over which measurements must be made, increases the precision of the DP sensor significantly - 100 to 3,000 times in comparison to systems without a reference tube. Thisallows the LRDP system to employ an offthe-shelf, inexpensive, and rugged DP sensor instead of a special purpose, expensive and delicate one. An industrial grade DP sensor, which is manufactured by Rosemount, is located in the sealed container and measures the change in level
between the fuel inside the reference tube
and in the tank.

A straight, constant diameter tube is used to test tanks with vertical walls (Figur e 5), and a geometrically shaped tube is used to te st tanks with curve walls (Figure 6). For bulk tanks with straight walls, the
reference tube has a diameter of 3.5 in. For tanks with curved walls, the tube is shaped so that the product surface area at any depth changes in the same proportion in the tube and in the tank [17]. A shaped
reference tube is needed for 50,000-gal horizontal tanks and for the 12.5-M-gal tanks at Red Hill. If the tube is not shaped appropriately, the thermally induced volume changes of the fuel cannot be accurately compensated.
This is true for both mass-based and volumetric systems. The errors can be large enough to prevent the system from meeting the regulatory guidelines. In the Red Hill tanks, for example, the tapered tube eliminates an error of 20 gal/h that w ould otherwise be present in
the measurement. Such errors can occur even when the rate of change of temperat ure is extremely small (e.g.,

0.0023 o C/h, as it was in this estimate).

The same shaped reference tube can be used for all tanks with the same diameter, regardless of capacity. For best accuracy, the design of the tube should change as the diameter of the tank changes. For 50,000-gal

Figure 6. Shaped reference tube used in a 50,000-gal

UST.

Figure 7. Bottom container of the LRDP housing the sensor systems.17 tanks two reference-tube designs would cover the range of tank diameters (generally 10.5 to 12.0 ft) found in commercial and DoD tanks.

2.2.3 Measurement Sensors in a Bottom-Mounted Sealed Container

All of the measurement sensors are located in a sp ecial sealed container at the bottom of the tank (Figure 7). This container is 18 in. in height and 6.8 in. in diam eter. The sealed container is actually comprised of a cylinder within a cylinder . The inside cylinder is dry and contains a differential pressure sensor, one or two pressure sensors, and a temp erature sensor attached to the differential pressure sensor. The annular space that exists between the inner and outer cylinder
contains fuel and communicates with the fuel in the reference tube attached to the top of this
bottom module. As an extension of the referen ce tube, the cross-sectiona l area of the annular space also changes in the same proportion as the pr oduct surface area in the ta nks changes. If the tank has vertical walls, then the cross-sectional area of the annu lar space does not change. If the walls of the tank are curve, then a special space r bar is inserted into the annular space whose volume changes with depth so that the cross- sectional area of the annular space changes appropriately with depth. A spacer bar, whose volume is constant with depth, can be used to reduce the cross sectional area in the annular space if a reference tube with a smaller diameter than 3.5-in. is used. These spacers are made of aluminum to reduce weight. To avoid the possibility of leakage, the bottom of the container is welded closed.

The DP sensor is the main sensing element of th e LRDP. It measures the difference in level of
the fuel in the reference tube and in the tank. The DP sensor measures the change in level
between the fuel inside the reference tube and in the tank. The two se nsing ports of the DP sensor are at the same elevation. One of the por ts communicates directly with the fuel in the tank. The other port communicates with the fuel in the annular space. As stated above, an industrial grade differential pressure sensor, whic h has a long-term demonstrated track record of performance, can be used in the system, because the measurement configuration only requires measurements to be made over the small differences in height that may occur in the reference tube and in the tank during a test. The differential pressure sensor is set to operate over a height range
of + 0.5 in. of fuel; the same dynamic range
was used for the Red Hill tank. This configuration increases the precision of the differential pressure measurement by a factor of at least 150 over a system that
does not use a reference tube. Because of the small dynamic range of the measurement, the precision of measuring level is 0.0002 in., where the precision is
defined as the one-standa rd deviation of the measured level fluctuations (Figure 8). -0.0004 -0.0002 0.0000 0.0002 0.0004

0 20 40 60

Time - minLevel - in. Water

Figure 8. A time series of the LRDP illustrating that the precision is 0.0002 in.18 A temperature sensor (RTD) is attached to the body of the DP sensor. It can be used to compensate for any thermal changes of the sensor if they become large. None of the field
demonstrations and evaluations conducted to da te has required such co mpensation, because the sealed container housing the sensors is located in a nearly constant temperature bath (i.e., the fuel in the bottom of a tank). While 0.01 o C/h changes in the fuel te mperature are large enough to produce volume changes of the fuel that mask a l eak, such temperature changes are too small to
affect errors in the DP sensor measurement. Temperature changes of several degrees per hour or more are required to introduce errors that may impact the accuracy of the DP sensor measurements. The temperature sensor mounted on the DP sensor can also be used to obtain an estimate of the mean temperature of the fuel in the tank.

One or two absolute pressure sensors may be locat ed in the sealed container. If one pressure sensor is located in the container, then the level of the fuel in the tank can be measured and used for inventory control purposes. If two pressure sensors are installed in the container, then in addition to the level measurement, either the specific gravity of th e fuel can be measured, or the level of any water at the bottom of the tank can be measured. The former measurement is made with the two sensors communicating with the fuel in the tank and separated by 16 in. The latter measurement is made by placing one of the sensors at a depth near the bottom of the tank, so that it is located in the water when water is present.

2.2.4 Mounting of the In-tank Sensor Unit

The reference tube and its connect ion into the annular space extends from the bottom of the tank to a level that is higher than the maximum level at which the tank is to be tested. The top of the
reference tube must be able to communicate freely with the vapor space. Many years of experience has indicated that any leak detection system with a level sensor needs to rest on the bottom of the tank. Thus, the
reference tube should be installed such that it rests on the bottom of the tank. Suspending the reference tube (or a level sensor from the top of the tank) introduc es errors due to the thermal expansion and contraction of the staff, chain or tube used to suspend the level
sensor. Problems are also encountered when the system is rigidly attached to a manway plate at the top of the tank, because the manway plate can raise (or lower) the reference tube due to thermal expansion or contraction. As shown in Figure 9, the mounting system is comprised of a 4-in. diameter cap in the manway of the tank, a bellows to prevent thermal movement, and a motor to open and close the valve. The bellows mounting system eliminates the thermal movement of the tank or manway Figure 9. Mounting system for a permanently installed
LRDP in a bulk UST.19 subject to ambient air temperatures. While thermally induced level changes of several
thousandths of an inch can in troduce large test errors, the bellows system allows for level changes of many hundredths of an inch (0.03 to 0.06 in.) before any errors are introduced.

2.2.5 Remote Test Controller

The remote test controller, shown in Figure 10, is located near each tank to be monitored and contains a microprocessor, a disk, a temperature se nsor, and a stable resistor. The remote test
controller can collect up to 8 channels of data, but more channels can be added, if required. Once a test is initiated from the host computer, the microprocessor collects, analyzes, outputs, and stores the data and the results. The analys is not only includes a comp utation of the measured volume rate, which is equal to the leak rate, if a leak is present, but also includes a comprehensive set of quantitativ e data quality indices (DQIs) that automatically assess the quality of the data before the data are used to complete a test. Up to 50 tests can be conducted and stored without downloading the data. The power supply and sensor electronics are also
located in the controller unit. Because of the temperature sensitivity of the pressure sensors and the large swings
that can occur in the ambien t temperature during a test, a temperature sensor and a stable resistor are installed in the controller for compensation. Only one, either the

stable resistor or the temperature sensor, is needed for compensation. However, both have been demonstrated as effective in this project.

2.2.6 Software

The host computer is used to initiate a test with its user-friendly Graphi cal User Interface (GUI) developed in a Windows 98 platform . Appendix D shows seven of th e user screens. The first Figure 10a. Photograph of the remote test
controller. Figure 10b. Schematic of the remote test controller.20 screen (Figure D-1) allows the operator to conduct a leak detec tion or review the results of previous leak detection tests.

The next screen (Figure D-2) asks what type of test will be c onducted (a 10-, 24-, or 48-h test), the duration of the waiting period after the final tank operations have been terminated, the start of the test, and the thres hold criterion. The current date and ti me is also given for information. The software is set up to operate using Version 1. 1a of the LRDP system [8-15]. Once the tank diameter is specified and the type of the test is selected, the threshol d criterion and the waiting period change accordingly. If a longer waiting peri od or a different threshold is desired, it can be entered directly.

The screen shown in Figure D-3 can be used to initiate a test no w or to schedule one for a later time. Before a test can be started, it is impera tive that the tank is isolated from its associated piping. A special reminder screen (F igure D-4) is displayed before a test can be initiated to make sure that the operator has shut al l of the valves necessa ry to perform a leak detection test.

A test is initiated by clicking on th e Start/Schedule Test button. One a test is initiated, no further action is required by the operator. Output of a time history of the data from any of the sensors can be displayed during the test. This screen also contains the re levant information about the test being conducted, including th e start and stop time.

The next screen (Figure D-6) s hows an output report from a leak detection test. This report can be printed and is sufficient to address all of the typical reporti ng requirements of the state and local regulating agencies.

The screen shown in Figure D-7 summarizes the resu lts of previous tests and allows the user to obtain the test reports from any pr evious test. This screen is pa rticularly useful when addressing the monthly monitoring requireme nt or when averaging data.

2.2.7 Conduct of a Test

A test consists of a waiting period (between the last transfer into and out of the tank and the start of a test) and the test itself. Th e waiting period used in these ev aluations was 2 h. This waiting period is not necessary from a performance sta nd point, but practically, it insures that the tank has been prepared for a test, i.e., all valves ha ve been closed and any drainback or disturbance from pumps etc. have been minimized. The basi c procedure for conducting a test is described
below.

• Specify what type of test will be conducte d (i.e., the test duration) and what waiting period will be used. There are two standard tests: (1) the LRDP-10, comprised of a 2-h waiting period and a 10-h test, and the LRDP-24, comprised of a 2-h waiting period and a 24-h test.

• Specify the threshold to be used in determin ing whether or not the tank passes or fails the

test

• The valve at the bottom of the reference tube is automatically left open between tests and the level of the fuel in the tube should be at the same level as the fuel in the tank21 • If the LRDP is being inserted into the tank fo r a test, allow the reference tube to fill up with fuel so that the fuel in the tube and in the tank is at the same level

• Close the valve to isolate the fuel in the reference tube from the fuel in the tank

• Begin collecting data with the LRDP. The da ta collected during the waiting is not used in the analysis. The data collected followi ng the waiting period is us ed in the analysis.

• Generate a time series of the difference in th e level changes in the tube and the tank using the pressure measurements obtained with the DP sensor. Level measurements are obtained by dividing the pressure measurements by the specific gravity of the fuel (e.g., 0.82).

• Convert the level time series to a volum e time series using the height-to-volume conversion (HVC) factor for the tank. Fo r a 122.5-ft-diameter tank, the HVC factor is 7,347 gal/in.

• Apply a set of Data Quality Indices (DQIs) to the volume time series to determine if the data collected is of sufficient quality to be used in a test. If a data quality problem is encountered during the first half of a test, the test is automatic ally extended by a time interval equal to half the test duration. If a problem is enc ountered during the second half of the test, the test is automatically repeate d. The test operator can abort the test at any time if there is not enough time to complete the tests before normal operations begin. Thus, the test may be extended either 12 or 24 h for a 24-h test, or 5 or 10 h for a 10-h test, depending on which half of the test data is of poor quality. If the test is extended, at present, the software only allows an extensi on equal to the duration of the test. If the extended test data fail the DQI tests, then another test can be initiated immediately or at a later time.

• If the data fail the DQI tests, then the output of the test is Inconclusive and must be repeated.

• If the data pass the DQI tests, then the rate of change of volume is computed by fitting a regression line to the volume time series data

• The measured volume rate is compared to th e detection threshold to determine whether the test is a Pass or a Fail . The tank passes the test if th e measured volume rate is less than or equal to the threshold. If the tank fails the test, the tank and the test data should be checked for problems, and then the tank s hould be re-tested. A leak rate is only printed out if the tank fails the test.

2.2.8 Data Quality Indices

Before a test is begun, the operator should verify th at the valves required to isolate the tank from its associated piping are closed a nd that the level of the fuel in the tank is below the top of the reference tube (which is usually above the maximum safe operating level of the fuel for the tank).

A number of data quality tests were developed and incorporated into the data acquisition and analysis software to identify potential problems that might o ccur during a test. These data quality problems were identified using previous data collected w ith the LRDP. One of the data quality tests is designed to determine if a pump is turned on during a test (Figure 11). Two pump signatures are shown in Figure 11. A test should not be conducted if product is being removed
or added to the tank.22 Another data quality test is designed to determine if there is a step discontinuity in the data (Figure 11). Su ch discontinuities might occur, for example, if a product sample is obtained during the test, or if the tank is opened during a test.

Another data quality test is designed to determine if there are any data dropouts or wild points in the data set (Figure 11). Still another data quality te st is designed to determine if the fluctuations in the level are too large for an alysis. Strong winds, internal wa ves, and other physical factors might produce such fluctuations. A data quality te st is also designed to determine if there are any inflows during a test.

Another data quality test is also
used to determine if the data set is sufficiently stable to draw a conclusion. A non-stationary leak, structural deformation of the tank, evaporation or condensation, or a particularly strong thermal affect might produce an unstable data set. All of these data quality indices
are set at the time the LRDP is
installed and should not be changed unless the number of
inconclusive tests is to o high. Figure 12 shows a data set wi th stability problem in which the
trend for the first half of the test is diffe rent than for the second half of the test.

During the evaluation, the data quality indices were set sufficiently high so that all of the data would be of sufficient quality to use except for very extreme problems. This was required to minimize the time required to complete the eval uation. It was justifie d because many of the problems that might be encountered operationally would not be encounter ed during a controlled evaluation (e.g., a transfer dur ing the middle of a test).

2.2.9 Summary

In summary, the LRDP is designed to easily and accurately compensate for the major sources of noise that might occur during a l eak detection test. Accurate compensation is obtained because the LRDP is specifically designed to compensate for each source of noise without the need for arrays of temperature sensors or delicate and expensive level sensor s. As a consequence, all of the sensors are off-the-shelf, commercially availa ble sensors that have a proven track record of -30.00000 -25.00000 -20.00000 -15.00000 -10.00000 -5.00000 0.00000 5.00000 10.00000 15.00000 20.00000 25.00000

0 2 4 6 8 10 12 14 16 18 20 22 24

Time - hourVolume -gal

Figure 12. Example of the results of the data quality indices identifying a problem with the stability of the data trend. -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

0 2 4 6 8 10 12 14 16 18 20 22 24

Time - minVolume -gal

Figure 11. Example of the results of the data quality indices identifying that a pump was turned on during a test.23 performance. The reference tube, the bellows mounting stand, and the bottom-mounted sensors are the key elements that lead to high performa nce. Other mass-based systems do not work as well because the sensors are mounted at the top of the tank and are subject to large diurnal swings in the ambient air temperature, are very delicate and expensive to achieve the level of precision required to conduct a test, and may re quire the use of nitrogen gas.

2.2 Strengths, Advantages, and Weaknesses

The LRDP system is ready for Full-Scale Implementation . It has the following advantages over other technologies that might be used for leak detection in large tanks:

• The LRDP is a mass-based technology, which is a preferred technology of the owners and operators of DoD bulk USTs.

• The LRDP can be used to perform a leak de tection test without removing fuel from the
tank.

• The LRDP system can be installed through a standard 8-in.-diameter opening in the tank.

• The LRDP can be used to test USTs w ith both vertical and curved walls. The
DEM/VALs were conducted in a bulk UST w ith vertical walls and a 50,000-gal UST
with curved walls. In anot her evaluation, the LRDP was us ed to test bulk USTs with
both vertical and curved walls. For tanks w ith curved walls, a special shaped reference
tube needs to be constructed.

• The LRDP has the best performance and the s hortest test time (10 h) of any mass-based technology. It is the only system th at conduct a test in less than 24 h.

• The output of a leak detection te st is easy to interpret, becau se it is a direct measurement of the leak rate in gallons per hour, the qua ntity of regulatory and engineering interest.

• The system is constructed of off-the-shelf sensors and components that have a proven track record of high performance, excel lent reliability, and low maintenance.

• The LRDP can be used as a portable system for performing a precision test as part of a leak detection testing service or permanen tly installed in the tank for automatic tank gauging operations including monthly monitoring and precision testing.

• The LRDP system has been successfully dem onstrated in a variety of operational DoD
tanks.

• The LRDP system has been evaluated for pe rformance and is listed with the National Work Group on Leak Detection Evaluations, a nationally recognize d, regulatory group
that allows the local and stat e regulatory agencies to select methods for their use.

• The LRDP system is the only mass-based system that can meet both the monthly monitoring and the semi-annual or annual pr ecision test regulatory guidelines in
California.

• The LRDP system is approved for use in California.

• The recurring cost of using and maintaining the LRDP are significantly lower than tracer methods and other mass-measurement methods. Because the LRDP system is a mass-24 based system, it inherently compensates for th e thermal expansion or contraction of the fuel in the tank during a test. Furthermore, accurate tests can be in itiated without a long pre-test waiting period.

• The mounting system eliminates thermally induced movement of the reference tube during a test.

• Thermally induced drift of the differential pre ssure sensor is virtua lly eliminated, because
it is mounted in a sealed cont ainer at the bottom of the tank.

• Because the differential pressure sensor used to measure level (volume) changes in the tank needs a dynamic range of only 1 in. (rather than the total heig ht of the tank, like other mass-based systems), the LRDP has the precision (0.0002 in.) to detect very small leaks in large-diameter tanks.

• The system is self-calibrati ng, and the performance and func tionality of the LRDP can easily be checked between leak detection tests.

• The sensors used to measure differential pr essure, pressure, and temperature are robust and have been used commercially in the pipeline leak detectio n systems that Vista
Research has been se lling for many years.

• The LRDP system can be modified for testing aboveground storage tanks (ASTs).

The main limitation of the method is that all of the valves in the fu el facility that isolate the tank from its associated piping must seal complete ly; if these valves do not completely seal, the LRDP system will detect this flow. This is not usually a problem for monitoring, because the monitoring standards are high enough to accomm odate small flows across the valve. For precision tests, however, the valves must seal completely. If the tank fails a test (either a monitoring or precision test), a de tailed inspection of th e tank and pipe valves is performed next assuming this is the reason for the failed test, an d if necessary, valve blinds are installed to complete the test. In many instances, closing th e valves tighter is all that is needed. The magnitude of this problem is not known for bul k tanks, but it is the same problem encountered and successfully addressed for routine monito ring of underground storage tanks at service
stations.

2.3 Factors Influencing Cost and Performance

Unlike remediation technologies, the performance of an LRDP is essentially independent of the site and the facility, because through the third-party evaluati on, the performance is estimated over a range of conditions that the system will operate. While these conditions may not include the extremes, they are sufficient to identify pe rformance problems that might be encountered under more challenging conditions. The main fact or influencing the perf ormance of the LRDP system (and other mass-based systems) is the si ze of the tank. The performance of the LRDP scales with the product surface area (tank diameter squared) in a prescribed way as determined by the third-party evaluation [6].

The main sources of problems during a test are oper ational ones. It is important that the tank is completely isolated from the associated piping, i.e ., all valves are completely sealed, before a test25 is initiated. It is also important that any drainback of fuel into the tank has ceased before a test is
initiated.

The LRDP is designed to fit into a standard 8-in.-diameter opening in a tank. The initial purchase cost, the installation cost, and the co st of operational use and maintenance are not affected by site parameters or site geology. This assumes that electrical power is available at
each tank and that communication cable has alr eady been installed between each tank and the building where the host computer is located. This assumption is valid, because systems used to acquire inventory level data are cu rrently being used at each site . The cost differential between an LRDP in a bulk UST with a small height (e .g., 13 ft) versus a large height (e.g., 25 ft) is insignificant and is attributed to th e cost of a longer reference tube.25 

### 3. Site/Facility Description

An overview of the sites/facilities used in the two demonstration and validation (DEM/VAL) tests are described below. For more details, please see the ESTCP Demonstration Plan [18].

3.1 Background

Two types of DEM/VALs were planned. The firs t, and most important, was to evaluate the performance of the LRDP in a large diameter bulk UST with vertical walls following a nationally accepted standard test procedure [6]. Si nce the leak detection system is not affected by soil conditions and site geology, and the evaluation procedure only requires that a tank that which is not leaking, the most important criterion in selecting a DEM/VAL site is to select a site with a suitable tank that can be used in the evaluation. Two criteria were used in selecting a site. First, it was desired to perform the DEM/VAL in a tank with a large enough diameter to address all of the tanks used by DoD. Second, it was desired that no inflow or outflow due to leaking valves or drainback from piping occur during the evaluation. Both problems interfered and degraded the results of the North Island evaluation, and the estimate of system performance from the evaluation did not reflect the true performance of the system. If there were no inflows, the evaluated performance would have been at least a factor of two better than determined from the evaluation. Initially, a bulk UST at the San Pedro Fuel Farm was selected for the DEM/VAL. After a series of tests in the tank, it was found that a small uncontrolled outflow existed due to a faulty valve. Because this outflow could not be measured independently, the DEM/VAL was moved to the Point Loma site, because it met the site selection criteria and the facility expressed an interest in using the system.

The second DEM/VAL was to demonstrate that the LRDP could be used for leak detection in a 50,000-gal horizontal tank with curve walls. While not considered a bulk UST, these large tanks are usually found at bulk fueling facilities and are used for storage of fuel before transfer into a hydrant pit or a loading rack. These tanks are found at almost every military facility. The Hunter Army Airfield site was selected for the DEM/VAL because this is typically the largest tank found at Army sites and there was on-site support and interest in fielding a DEM/VAL.

3.2 Site/Facility Characteristics

Brief descriptions of the Point Loma and H unter Army Airfield DEM/VAL sites are given
below.

3.2.1 DEM/VAL 1: Point Loma Fuel Terminal (Third-Party Evaluation in a Bulk UST)

The Point Loma Fuel Terminal stores and supplies fuel to other facilities in the area (e.g., the NAS North Island). The facility is located in San Diego, California, and has over 30 bulk USTs.26 The evaluation was conducted in Tank 175, because it was one of the largest field-erected bulk USTs owned or operated by DoD and the valves isolating the tanks had just been replaced and were expected to seal tightly. Also, the confi guration of the tanks and their associated piping was easy to verify whether or not the valves seal ed. Finally, the configuration afforded several ways to insure that the tanks were isolated from the piping.

Figure 13 shows the location of
Tank 175. This tank is located in a hillside and stores 2,100,000 gal of JP-5 fuel. Fuel is pumped into
the tank to fill it and the removal
of fuel from the tank is accomplished by gravity. The
tank is 122.5 ft in diameter and 23.5 ft in height. The tank is
buried about 5 ft below the surface of the ground. The product surface area (PSA) of the tank is 11,786 ft 2 . Level changes
in this tank are converted tovolume changes using a heightto-volume conversion (HVC) factor of 7,347 gal/in.

3.2.2 DEM/VAL 2: Hunter Army Airfield (50,000-gal UST)

There are 30 shop-fabricated 50,000-gal USTs at the Hunter Army Airfield (a sub-unit of Fort Stewart). Each of these tanks are nominally 10.5 ft in diameter, 80 ft in length, and are made of 3/8-inch thick welded steel. The tanks originally had a cut-back asphalt coating and, in 1986-87,
were lined inside with a 10-mil thick epoxy coating. Impressed current cathodic protection systems
were installed at the tank batteries in 1978. Figure 14 shows the location of Tank 45, the 50,000-gal UST
used in the DEM/VAL.

The thirty 50,000 gal USTs are arranged in three batteries of ten tanks each, at Pumping Stations #3, #4, and #5. The pumping stations are located in the Helicopter Landing and Parking Area. The
tank batteries are about 1500 feet west of the Base Operations Building #1252 and are identified as structures #8080, #8082, and #8084. These tanks were installed in the 1952-53 time period. Figure 13. Tank 175 at the Point Loma Fuel Terminal.

Figure 14. Tank 45 at the Hunter Army Airfield.27 Until 1996, the tanks were used to store JP5. In 1996, the facility converted to JP8. Neither the tanks nor the piping have ever had a discovered leak. Each 10-tank battery has a 6-inch diameter manifold connected supply pipeline and a 12-inch diameter discharge piping system running to the aircraft fueling area. An internal inspection, in 1997, of three selected tanks revealed the interior coating to be intact, with no signs of deterioration or significant corrosion.28 

### 4.0 Demonstration Approach

As stated above, two types of demonstrations we re conducted. The first and most important was an evaluation of the performance of the technol ogy following a standard test procedure used and approved by the regulating community for bulk USTs [6]. The second was a demonstration of the system on a 50,000-gal tank commonly found at bulk fueling facilities. This second demonstration consisted of a few tests to demonstrate that the system had the performance capability to meet the 0.2-gal/h monthly monitoring regulatory standard. For more details, please see the ESTCP Demonstration Plan [18].

4.1 Performance Objectives

The performance objectives of the DEM/VALs are established by the regulatory guidelines for detection of leaks in bulk USTs. Since there are no national regulatory compliance standards for bulk USTs, the California regulatory guidelines were adopted as the basis for the performance objectives of this project, because they are practical and the most stringent standards. These guidelines indicate that the leak detection system must be evaluated for performance by an independent third-party following a standard test procedure [6]. The results of this evaluation must be reported in terms of a P D of the target leak rate (TLR) and a P FA . As stated above, the TLR is specified by the regulatory agency and at a minimum the P D must be equal to or better
than 95% and the P FA must be less than or equal to 5%. The DEM/VAL at the Point Loma Fuel Terminal followed this standard test procedure. The performance objective of the DEM/VAL conducted on the 50,000-gal USTs at Hunter Army Airfield was to show that the results of several tests had the capability for detecting leaks of 0.2-gal/h, the regulatory standards for these tanks. This was accomplished by conducting a few tests and showing the results were not statistically different than the evaluation results. The evaluation results indicated that the LRDP would be able to detect a TLR = 0.2 gal/h with a P D = 95% and a P FA = 5%.

4.2 DEM/VAL 1: Point Loma Fuel Terminal (Third-Party Evaluation in a Bulk UST)

A third-party evaluation of the LRDP was conducted by Ken Wilcox Associates, Inc. (KWA). The output of the evaluation is the TLR that can be detected with a P D = 95% and a P FA , which must be less than or equal to 5% for the system to be used. The LRDP leak detection system was designed for use in petroleum fuel tanks, but can be used for other hazardous substances. Thissection describes the sampling/data-collection procedure used in the evaluation, the physical setup and operation of the facilities and equipment needed to conduct the evaluation, the conditions in the evaluation, and the output from each test conducted.

4.2.1 Evaluation Procedure

The LRDP was evaluated in accordance with the protocol described in the report “Alternative Test Procedures for Evaluating Leak Detection Methods: Evaluation of Bulk Field-Constructed29 Tanks” [6]. This 1996 protocol was updated in 1999 for mass-based bulk leak detection systems and adheres to the guidelines specified in EPA’s standard test procedures for determining and reporting the performance of leak detection systems. The update allows the performance results to scale with the product surface area of the tank and averaging of the test results to improve performance. This protocol has been approved by the NWGLDE, and has been accepted by federal, state and local regulatory agencies as the means for demonstrating the performance of bulk tank leak detection systems. This protocol is also in accordance with the evaluation protocol and reporting procedures specified in the ASTM standard practice (E-1526-93) [7].

The UST regulation for USTs requires that the performance of any leak detection that is used for testing a tank be evaluated for performance following a standard test procedure. The states, which implement the regulation, require an independent third party to perform the evaluation. The leak detection systems used for the small USTs found at petroleum service stations are evaluated in testing facilities owned and/or operated by the third-party evaluator. For systems used in bulk USTs, an operational facility must be used because no bulk test facilities exist. When an evaluation is completed, it is submitted to the NWGLDE for review and certification that it has been properly evaluated. Properly evaluated leak detection systems are then added to a list for use by the states when approving leak detection methods for use in their states. For most of the states, if a method is listed, it can be directly approved. For a limited number of states, like California and Florida, a more detailed review may be required.

As shown in Table 4, the evaluation protocol requi res that 12 tests be conducted at four different leak rates and under variable fuel temperatures. The tank is emptied to 50% of capacity and refilled back to approximately 95% to produce (1) temperature conditions typical of

Table 4. Standard Test Schedule

Test Prep Test

No. Pair

No. Set

No. Nominal

Leak Rate Nominal Temp Diff

Trial run
- - - 0.00 0

Empty to 50% 1 1 1 LR1 T1
then refill to 95% 2 1 1 LR2 T1

Empty to 50% 3 2 1 LR4 T2
then refill to 95% 4 2 1 LR3 T2

Empty to 50% 5 3 2 LR1 T3
then refill to 95% 6 3 2 LR4 T3

Empty to 50% 7 4 2 LR2 T4
then refill to 95% 8 4 2 LR3 T4

Empty to 50% 9 5 3 LR4 T5
then refill to 95% 10 5 3 LR1 T5

Empty to 50% 11 6 3 LR3 T6
then refill to 95% 12 6 3 LR2 T6

operational conditions during fuel deliveries and transfers and (2) the type of wall deformation that might occur as a result of a level change. Typically, the rate of change of temperature depends on the temperature difference between the fuel in the tank and the backfill and soil30 around it. For the purposes of the evaluation, a temperature condition, as reported on a given test, is equal to the difference in temperature between (a) the fuel in the tank and (b) the fuel brought into the tank during filling operations. (It is assumed that the temperature of the fuel in
the tank before such a transfer is approximately the same as that of the backfill and surrounding soil.) For each test, the third-party evaluator induces leaks of a pre-determined size, all unknown to the testing party. At the end of the 12-test sequence, the testing party submits its estimates of the leak rates, and the testing party’s data are analyzed in accordance with statistical guidelines provided in the evaluation protocol [6].

Neither the LRDP or any of the equipment used in the evaluation produce any contaminants. The product removed from the tank to simulate a leak flows through clean tubing into a clean barrel. Since the fuel is not contaminated, it is normally returned to the tank after the test. Thus, there is no test process waste, other than that re sulting from final cleaning of the tube and barrel.

The test results will qualify the system for use in bulk USTs with any commercial petroleum product of grade number 2 or lighter. For other liquids, some component materials may need to be changed for chemical compatibility.

The evaluation protocol requires that performance be presented in terms of the leak detection system’s P FA and its P D against a specified TLR. The performance is estimated directly from the histogram of the noise and the histogram of th e signal-plus-noise. In general, the noise histogram is estimated from a statistical compilation of the results of many leak detection tests on a non-leaking tank. These tests are conducted over a wide range of ambient thermal conditions and induced-leak conditions such as might be expected during routine testing. For mass-based systems, where the signal (volume changes) produced by the leak are additive with the noise, the signal-plus-noise is then a shifted replica of the noise histogram. The shift (or mean) of the signal-plus-noise histogram is equal to the TLR. The histograms are generally displayed in terms of their cumulative frequency distributions (CFDs).

The performance of the LRDP system was estimated using a student-t probability model for the histograms. More detailed descriptions on how to estimate performance can be found in thestandard test procedure [6]. Because mass-based systems test at a constant pressure, the signalplus-noise histogram can be generated directly from the noise histogram by adding the leak rate of interest to the test results. This is possible, because the volume changes due to a leak are
additive with those due to noise.

This is not true of all leak detection systems. With non-mass-based (and non-volumetric) systems, for example, the signal-plus-noise histogram must be generated experimentally for each and every leak rate for which the probability of detection is desired.

Unlike remediation methods, once a leak detection method is evaluated in a tank, similar performance can be expected in other tanks provided that they are not too big and the main source of noise, thermal expansion and contraction of the fuel, is not too much larger than the conditions used in the evaluation. For in-tank volumetric methods, mainly used to test the small USTs found at service stations, at least two constraints were placed on the use of the system. First, the system could not be used to test a tank that was any larger than 150% of its volume. Second, the system could not be used to test a tank when the difference in the temperature of the fuel and the ground was greater than 150% of the average temperature condition used in the31 evaluation. The only performance that could be claimed by the manufacturer of the system was the one that was evaluated, regardless of the size of the tank or temperature conditions under which it would be used. If a larger tank was to be tested, then another third-party evaluation had to be performed.

For bulk USTs using a mass-based system, these constraints were modified to accommodate the differences between mass and volumetric methods. The temperature constraint was eliminated, because it does not affect the performance of a mass-based system. The tank-size limitation was modified, because the performance of a mass-based system does not scale with the volume of the fuel in the tank; it scales with the product su rface area. Because of the limited number of bulk USTs and the wide range of tank sizes, the NWGLDE increased the multiplier from 150% to 250%. If the evaluation tank was properly selected, than once evaluated, it could be used to test any tank within the DoD. The use of the 150% constraint would have meant that at least three or four evaluations would have had to be conducted to cover all of the tanks. Because of the large range of tanks to be tested, the NWGLDE required that the performance of the method be scaled by the product surface area. Thus, for tanks larger than the one used in the evaluation, the performance of the method would be worse than that achieved in the evaluation, and for tanks smaller than the one used in the evaluation, the performance would be better. The NWGLDE also limited the TLR to no less than 0.2 gal/h, regardless of scaling. This scaling can be technically justified and has been experimentally verified for mass-based systems, but not for
volumetric methods.

KWA conducted its third-party evaluation of the LRDP system at the Point Loma Fuel Terminal, on a 122.5-ft-diameter, 2,100,000-gal bulk UST. This tank was selected because it was one of the largest diameter tanks owned and operated by the DoD, and the valves that are used to isolate the tank from its associated piping were new, doubl e-block valves that sealed tightly. The tank contained jet fuel with a specific gravity of approximately 0.82. The tank was approximately 23.8 ft in height. The tests were conducted between 87 and 90% of capacity, the maximum safe operating level for the tank. Several additional tests were conducted at 50% capacity to demonstrate that the performance does not vary with product depth.

The evaluation was done in accordance with the EPA guidelines described above. With a massbased system like the LRDP, there is no real need to induce leaks during an evaluation, because, as stated above, volume changes due to a leak are simply additive with those due to noise (for example, thermal expansion or contraction of the fuel). Induced leaks are included in the evaluation, because they are required by the protocol to create a blind testing situation and to ensure that the system actually responds to a leak.

4.2.2 Evaluation Tank

The evaluation was conducted at the Point Loma Fuel Facility over a three-month period beginning on March 22, 2000 and ending on June 8, 2000. The tank used in the evaluation is located on a hillside and stores JP-5 fuel. The fuel is pumped into the tank to fill it and the removal of fuel from the tank is accomplished by gravity.

The evaluation was performed in an operational 2,100,000-gal steel-lined concrete tank containing jet fuel. The tank was 122.5 ft in diameter and 23 ft-5 in. in height. Figure 13 showed
the location of the tank in the side of a hill.32 The LRDP was installed in the tank and checked out on 15-17 February 2000. Representatives from NFESC, KWA, Vista Research, and Vista Engineering were present. A two-person team is needed to install the system.
The total installation time is less than 4 h. The LRDP was installed in an 8-in. opening (Figure 15). The LRDP used at North Island and KWA’s level gauge and RTD array were installed in a 22- in.-diameter manway located about 10 ft away from the 8-in. opening. The peristaltic pump used
to induce leaks in the tank was also located in this

manway.

Level changes in this tank can beconverted to volume changes using a height-tovolume conversion factor of 7,347 gal/in. Testing during the evaluation was accomplished by KWA personnel following the LRDP testing procedures specified by NFESC and Vista Research. Leak
simulations and fuel deliveries were also defined by KWA. The LRDP data were collected by KWA. The output of each test was automatically output from the system. The results from add itional test durations were also output from a worksheet used by KWA using the same analysis procedure as used in the system. The evaluation was interrupted, as required by fuel farm personnel, to support military and fuel operations. Delays of one or more days to a week or more sometimes occurred in executing the evaluation protocol.

For comparison purposes, the LRDP evaluated in an 88-ft-diameter tank at NAS North Island (Figure 3), was also installed in the tank th rough a 22-in.-diameter manway near the 8-in. opening. This was done to demonstrate that the performance of the modified version of the system developed under this ESTCP project was no different than the system evaluated previously. The level data obtained with both systems, as expected, were nearly identical.

Leaks were induced by KWA through the manway. For each test, the volume rate measured by the LRDP system was compared to the leak rate induced by KWA. Twelve tests were
conducted. There was a total of six fuel transfers. Fuel was transferred from other tanks in the fuel farm. The temperature of the received fuel and the fuel in the tank was measured for each test. Tests were conducted with the tank at approximately 90% full with additional tests conducted at 50% full. The induced leaks were monitored by KWA throughout the three-month
evaluation.

The induced leaks were produced by pumping fuel out of the tank with a peristaltic pump. Nominal leak rates of 0.4, 0.8, and 2.0 gal/h were randomly induced during the evaluation. Neither the nominal nor actual leak rate was made known to NFESC or Vista until many months after the evaluation had been completed and the final evaluation report was prepared. Leak rates were calculated from the total mass of fuel removed from the tank during the test and the density of the fuel that was measured with an analytical balance in a laboratory. The mass of the fuel Figure 15. Installation of the LRDP in the Point
Loma tank.33 removed from the tank was measured by pumping the fuel into a barrel hanging from a load cell. The uncertainty in the induced leak rates was less than 0.01 gal/h. During each test, KWA also verified the magnitude of the induced leak rate by measuring the pump rate with a graduated cylinder and a stop watch.

Fuel levels and fuel temperatures were electronically monitored by KWA throughout the evaluation using a level gauge and an RTD array. This allowed KWA to record and document the exact times and temperatures of the fuel deliveries. The temperature array consisted of RTDs
located in the bottom 50% of the tank.

4.2.3 Evaluation Conditions and Test Results

The test conditions and results obtained during the evaluation are summarized in Table 5. Column 1 gives the test number, and column 2 gives the date and time that each test was started. The level change due to the delivery of fuel to th e tank prior to the start of the test is shown in column 3, and the temperature condition (the difference in temperature of the fuel in the tank and

Table 5. Summary of the Test Results and I nduced Leak Rates for the LRDP Systems

Test
No. Test Start

(d/m/y (hhmm) Level Change du e to Delivery

(in.) Temperature
Condition 1

( o F) Fuel Depth

(%) KWA
Nominal Induced
Leak Rate 2

(gal/h) KWA
Actual Induced

Leak Rate 2

(gal/h)

1

2

3

4 03/22/00 1539

03/23/00 1736

03/27/00 1519

03/28/00 1728 116.0

N/A

113.4

N/A 0.2

N/A

-0.2

N/A 90

90

89

89 -0.3

0.0

-0.4

-0.8 -0.327

0.000

-0.444

-0.824

5

6

7

8 04/05/00 1715

04/06/00 1919

04/18/00 1614

04/19/00 1740 106.0

N/A

111.3

N/A -0.6

N/A

-0.2

N/A 87

87

89

89 -1.0

0.0

-0.8

-0.2 -1.040

0.000

-0.765

-0.170

9

10

11

12 04/27/00 1308

05/11/00 1500

05/12/00 1731

06/07/00 1557 63.6

N/A

110.3

109.4 1.4 3

N/A

-0.5

-0.2 90

88

88

88 -2.0

-2.0

0.0

-2.0 -1.934

-1.820

0.000

-1.845

1 A negative temperature condition means that the fuel in the tank was colder than the fuel in the tank and the surrounding ground. 2 A negative value indicates a leak out of the tank. 3 Test 9 was initiated 70.6 h after the transfer was comple ted so it was not used in the temperature differential calculations. A test was not conducted before Test 9.

the fuel delivered to the tank) is shown in column 4. The depth of fuel in the tank during the test, the nominal induced leak rate, and the actual leak induced by KWA as part of the evaluation are shown in columns 5 through 7, respectively. As shown in Table 5, the temperature conditions ranged from –0.6 o F to +1.4 o F. Fuel deliveries ranged from 463,662 gal (a level change of 63.6 in.) to over 845259 gal (a level change of 260 in.). The leaks induced by KWA,34 nominally 0, [0.2, 0.3, 0.4], [0.8, 1.0], and 2.0 gal/h, ranged from 0.0 gal/h to 1.94 gal/h.

A more detailed summary of the test conditions and the results are presented in Tables 6-8.
Tables 7 and 8 show the volumetric errors for both the LRDP-10 and LRDP-24.

4.2.4 Comparison of the LRDP Evaluated at NAS North Island and the LRDP Evaluated
Under ESTCP

To show that the performance of the system was unaffected by the changes to the LRDP system under ESTCP, leak
detection data were simultaneously obtained using the LRDP tested at
North Island and the LRDP
used in the ESTCP evaluation. Figure 16 shows a comparison of the two data sets offset by a
constant of 0.002 in. for display purposes. The
estimated volume rate determined by each LRDP is different by 0.01 gal/h. y = -2.2728x + 187.9 5

R 2 = 0.9829 y = -2.2726x + 197.45

R 2 = 0.9656

75 100 125 150 175

12 16 20 24 28 32 36 40

Time - hVolume - gal

LRDP-1 (1.428049) DLvl LRDP-1 Cal Linear (DLvl) Linear (LRDP-1 (1.428049)) Figure 16. Comparison of the LRDP data obtained with the engineering prototype of the LRDP and the LRDP evaluated in the ESTCP project.35Table 6.Summary of the Evaluation Temperature ConditionsBefore Fill After Fill Before Fill After Fill Start End Calculated DeliveryTest Delivery Delivery Delivery Level (50%) Level Volume (50%)Volume Temp Temp Delivery TemperatureNo. Start Time End Time Fill Time (inches)* (inches)(gallons) (gallons) (deg F) (deg F) Temp Differential1 3/22/2000 11:30 3/22/2000 15:31 1/0/1900 4:01 144.0 260.0 1,049,354 1,894,61364.4 64.2 64.0 0.23 3/27/2000 11:00 3/27/2000 15:18 1/0/1900 4:18 144.0257.4 1,049,354 1,875,455 64.4 64.5 64.7 -0.25 4/5/2001 8:22 4/5/2001 17:15 1/0/1900 8:53 144.0250.0 1,049,354 1,821,852 64.6 65.1 65.7 -0.67 4/18/2000 11:00 4/18/2000 15:30 1/0/1900 4:30 144.0255.3 1,049,354 1,860,590 65.4 65.5 65.8 -0.29 4/25/2000 12:59 4/25/2000 14:29 1/0/1900 1:30 196.5 260.1 1,431,905 1,895,56765.8 65.4 64.0 1.411 5/11/2000 10:34 5/11/2000 14:53 1/0/1900 4:19 144.0254.3 1,049,354 1,853,303 65.8 66.2 66.7 -0.512 6/7/2000 12:08 6/7/2000 15:54 1/0/1900 3:46 144.0253.4 1,049,354 1,846,380 68.0 68.2 68.3 -0.2(1) Height-to-volume = 7,287 gal/in. (2) Tank Capacity = 2,098,708 gal. (3) Tank Height = 288 in.* Tank operator stated that the level was dropped to 50% operational level before each delivery.36 Table 7. Final Results for the Evaluation of the LRDP-10 at Point Loma

Test

No. New LRDP Filename Transfer

Prior to

Test Nominal

Leak Rate Induced

Leak Rate Waiting

Period EVR Actual VR VR Error

(gal/h) (gal/h) (h) (gal/h) (gal/h) (gal/h)
1 Tnk175_3_22_2000_15_39.dat -0.327 1.87 -0.179 -0.327 -0.148 2 Tnk175_3_23_2000_17_36.dat Yes 0.3 0. 000 0.00 0.470 0.000 -0.470 3 Tnk175_3_27_2000_15_19.dat 0.0 -0.444 2.00 -1.142 -0.444 0.698 4 Tnk175_3_28_2000_17_28.dat Yes 0.4 -0. 824 0.00 -0.908 -0.824 0.0838 5 Tnk175_4_5_2000_17_15.dat 0.8 -1.040 10.00 -0.724 -1.040 -0.316 6 Tnk175_4_6_2000_19_19.dat Yes 1.0 0. 000 0.00 -0.059 0.000 0.059 7 Tnk175_4_18_2000_16_14.dat 0.0 -0.765 10.00 -1.014 -0.765 0.249 8 Tnk175_4_19_2000_17_40.dat Yes 0.8 -0. 170 0.00 -0.566 -0.170 0.395 9 Tnk175_4_27_2000_13_8.dat 0.2 -1.934 3.00 -2.194 -1.934 0.260 10 Tnk175_5_11_2000_15_0.dat 2.0 -1.820 1.95 -1.797 -1.820 -0.023 11 Tnk175_5_12_2000_17_31.dat Yes 2.0 0. 000 2.00 -0.238 0.000 0.238 12 Tnk175_6_7_2000_15_57.dat Yes 0.0 -1.845 2.00 -1.786 -1.845 -0.060 Mean = 2.24 Mean = 0.080 gal/h Median = 1.98 Standard Deviation = 0.317 gal/h

N = 12

dof = 11
MDLR = 1.140 gal/h

n needed for 0.2 gal/h = 32.5

t B = 0.878

Table 8. Final Results for the Evaluation of the LRDP-24 at Point Loma

Test

No. New LRDP Filename Transfer

Prior to Nominal

Leak Rate Induced

Leak Rate Waiting

Period EVR Actual VR VR Error

(gal/h) (gal/h) (h) (gal/h) (gal/h) (gal/h)
1 Tnk175_3_22_2000_15_39.dat Yes 0.3 -0. 327 1.87 -0.327 -0.327 0.000 2 Tnk175_3_23_2000_17_36.dat 0.0 0.000 0.00 0.232 0.000 -0.232 3 Tnk175_3_27_2000_15_19.dat Yes 0.4 -0. 444 2.00 -0.726 -0.444 0.282 4 Tnk175_3_28_2000_17_28.dat 0.8 -0.824 0.00 -1.072 -0.824 0.248 5 Tnk175_4_5_2000_17_15.dat Yes 1.0 -1.040 2.00 -0.832 -1.040 -0.208 6 Tnk175_4_6_2000_19_19.dat 0.0 0.000 0.00 0.081 0.000 -0.081 7 Tnk175_4_18_2000_16_14.dat Yes 0.8 -0. 765 12.00 -1.053 -0.765 0.288 8 Tnk175_4_19_2000_17_40.dat 0.2 -0.170 0.00 -0.453 -0.170 0.283 9 Tnk175_4_27_2000_13_8.dat 2.0 -1.934 3.00 -2.162 -1.934 0.228 10 Tnk175_5_11_2000_15_0.dat Yes 2.0 -1. 820 1.95 -1.834 -1.820 0.014 11 Tnk175_5_12_2000_17_31.dat 0.0 0.000 2.00 -0.190 0.000 0.190 12 Tnk175_6_7_2000_15_57.dat Yes 2.0 -1. 845 2.00 -1.997 -1.845 0.152 Mean = 2.24 Mean = 0.097 gal/h Median = 1.98 Standard Deviation = 0.192 gal/h

N = 12

dof = 11

MDL

R = 0.690 gal/h

n needed for 0.2 gal/h = 11.9

t B 1.75037 4.3 DEM/VAL 2: Hunter Army Airfield (50,000-gal UST)

A DEM/VAL of the LRDP was conducted on a 50,000- gal UST at the Hunter Army Airfield, Savannah, GA (part of Fort Stewart). The speci fic objectives of the DEM/VAL, the physical setup and operation, and the sampling/data-collection procedure are described below.

The primary objective of the test was to demonstrate that the system could be used to test horizontal tanks for leaks. A special reference tube, whose cross-sectional area changed as a function of depth was used instead of a constant-diameter tube. Other objectives of the
DEM/VAL were to

• demonstrate that the LRDP could measure the level of the fuel in the tank to the nearest 1/8 in. for inventory control and reconciliation,

• validate the deployment procedure that was developed to insure that all air was adequately bled from the tubing in the sensor system, and

• demonstrate that the LRDP could be used as a portable system for performing an annual precision test of the tank.

In a vertical right regular cylinder, the free surface area of the fuel is constant regardless of level. In a tank with curved walls, however (e.g., a horizontal cylinder, or a vertical cylinder with a spherical top and bottom), the free surface area varies as a function of level. In this type of tank, a DP sensor will not completely compensate for the thermal expansion or
contraction of the fuel. To address this type of tank, the LRDP system incorporates a second design in which the cylindricalreference tube is replaced by a variableshaped tube that mimics the cross-sectional changes in the tank’s geometry as a function of depth [17]. This shaped reference tube, which is shown in Figure
was used instead of the constant-diameter
tube used for bulk USTs.

The DEM/VAL was conducted between 29
November and 2 December 1999. The tank contained 38,100 gal (74% of capacity) for these tests. Figures 17 and 18 show the LRDP being installed in the tank through the standard 8-in.opening in the tank. The
LRDP can be installed in less than four hours by a single person.

Three types of tests were conducted to meet the objectives stated above. The first was
to demonstrate that the level of the fuel in
the tank could be measured and used for inventory purposes. The second was to Figure 17. Installation of the LRDP in the 50,000-gal UST.38 show that the system would respond if a known volume of product were to be removed or
added to the tank. The third
was to demonstrate that the
LRDP had sufficient performance to meet the 0.2- gal/h monthly monitoring regulatory standard.

A 24-h test was conducted on November 19, 1999 to
determine whether or not the tank was leaking. Having
determined that the tank was tight, a demonstration of the system was conducted for site personnel on November 20, 1999. After the demonstration, additional data were collected with the LRDP; a total of 74 h of data were collected. Analyses were then performed to make an estimate of performance of the LRDP for use in 50,000-gal USTs using test durations of 8 h and 24 h.

To satisfy the 0.2-gal/h monthly monitoring regulator y standard, the LRDP would have to be able to detect a leak of 0.2 gal/h with a P D = 95% and a P FA < 5%. This performance is achieved if the standard deviation of the error in the tests used in an evaluation is less than or equal to 0.06 gal/h. If only a single test was conducted, the error in this test would have to be less than 0.10 gal/h, as determined by a hypothesis test using a student’s t distribution at a level of significance of 0.05.

Table 9. Summary of the Test Results for the LRDP Sy stems in a 50,000-gal UST at Hunter Army Airfield

Test No. Test Start (mm/dd/yy hhmm) Induced Leak

Rate 8-h Test

VR* 8-h Test

VR Error 24-h

VR* 24-h Test

VR Error (gal/h) (gal/h) (gal/h) (gal/h) (gal/h)

1a 11/19/99 1155 0.000 -0.087 -0.087 0.014 0.014

1b 11/19/00 1939 0.000 0.027 0.027

1c 11/20/99 0339 0.000 0.123 0.123

2a 11/20/99 1604 0.000 -0.049 -0.049 0.010 0.010

2b 11/21/99 0004 0.000 0.051 0.051 0.010 0.010

2c 11/21/99 0804 0.000 0.042 0.042 -0.008 -0.008

2d 11/21/99 1604 0.000 -0.037 -0.037

2e 11/22/99 0004 0.000 0.013 0.013

2f 11/22/99 0804 0.000 0.014 0.014 2g 11/22/99 1604 0.000 -0.080 -0.080

2h 11/23/99 0004 0.000 0.010 0.010

2I 11/23/99 0804 0.000 -0.025 -0.025 2j 11/23/99 1604 0.000 0.066 0.066

* VR = Volume Rate

The 98 h of data collected during the November 19, 1999 and November 20, 1999 tests were grouped, and as shown in Table 9, the data were analyzed in 8 h and 24 h segments to make an estimate of performance. Figure 18. Top of the being installed in an 8-in.opening in a 50,000-gal
UST.39 A full-scale evaluation was not performed, because the scaled results of the bulk UST evaluation indicates that this level of performance would easily be achieved by the LRDP in a 50,000-gal UST. As a consequence, only a few tests were performed and a statistical comparison was made. If the LRDP were to be used to test these USTs, it would have to undergo a complete third-party
evaluation.

4.4 Other Field Tests in Bulk USTs with the LRDP

It was originally intended to verify that the system was functional and then to evaluate the performance of the LRDP in a 132.5-ft-diameter, 2,100,000-gal bulk UST at the DEO-LA San Pedro Fuel Farm. The first objective was addressed, but the second objective could not be addressed because of a valve or valves that did not completely seal.

The San Pedro fuel farm is located about 1.5 mile s NW of the West Basin of Los Angeles Harbor. Tank #5, which was been selected for the demonstra tion tests, contained jet fuel and was 20 ft in depth. It had extensive leak testing within the past two years and does not have any known leaks.

The LRDP was installed in the tank on January 1999, and an extensive set of field measurements were made until May 1999. A small flow across the valve (outflow) of approximately 0.1 gal/h was observed that was believed to be due to valve leakage. The specific source of this small flow could not be identified, and it was determined that the evaluation should be performed on another tank in which the valves were known to be tight, as required by the evaluation protocol. Such a problem existed during the first evaluation of the LRDP at North Island and led to artificial constraints being placed upon the operational use and performance of the system by the
NWGLDE. Additional discussion can be found in Section 9.40 

### 5.0 Performance Assessment

The performance of the LRDP system was assessed for its suitability for both monthly monitoring and for annual or semi-annual precision (tightne ss) testing. The results of the third-party evaluation conducted by KWA on the Point Loma bul k UST are presented and discussed below.
Section 5.1 summarizes the result s of the previous evaluation, and why a second third-party
evaluation was conducted. Secti on 5.2 describes the various me thods evaluated. Section 5.4 describe the data measured with the LRDP system and summarizes statistic ally the individual test
results tabulated in Table 7 for the LRDP-10 a nd Table 8 for the LRDP-24. Estimates of the performance of the LRDP-10 and LRDP-24 are pres ented in Sections 5.4 for a single test. The enhanced performance achieved when two or more tests are averaged together is presented in
Section 5.5 for the LRDP-10-n and the LRDP-24- n, where n is the number of tests averaged together. Section 5.6 summarizes the re sults for different thresholds and P FA s (Versions 1.0a, 1.1a, and 1.2a). The applicability of the results and how to use the LRDP is meeting regulatory requirements are presented in Sections 5.7 throu gh 5.10. Section 5.10 describes the results of the DEM/VAL at Hunter Army Airfield on a 50,000-gal UST.

The only difference in the test pr otocol between the LRDP-10 and the LRDP-24 is the duration of the test. The 10-h test duration required by th e LRDP-10 allows for monitoring tests to be conducted during an overnight period. The same type of monitoring test can be accomplished with the LRDP-24 using a 24-h test, but with a significantly better probability of false alarm against the same target leak rate, or a significantly bett er capability for detecting smaller leaks for the same probability of false alarm. As predic ted by theory, the performance of the LRDP-24 in
terms of detectable leak rate is 70% better than the performa nce of the LRDP-10. As shown below, however, both systems have sufficient performance to meet the regulatory standards for testing bulk tanks.

5.1 Results of the Fi rst LRDP Evaluation

The performance of the LRDP system depends on the diameter of the tank, the duration of the test, and the number of tests averaged together. The LRDP was previously evaluated for performance by Ken Wilcox Associates. This ev aluation was performed in an 88-ft-diameter
UST at the NAS North Island Fuel Farm. Some degradation of performance occurred because of
fuel drainback into the tank duri ng the evaluation. Such degradati on is not representative of the method, but rather the evaluation conditions. A data quality index was used to identify the presence of drainback (inflow) and to determin e when it was small enough to begin a test. The average waiting time required to wait until th e drainback was small was 24 h. Thus, a waiting period of 24 h was specified by the NWGLDE. Ev en though the drainback was small after 24 h (less than 0.1 gal/h), it degraded the performance by at least a fact or of two over what should have
been the outcome of the evaluation. This assessm ent could be made because of several back-toback tests with and without leaks in which the volume rate difference between these tests was equal to the induced leak to within 0.03 gal/h.41 Even with this degradation, th e LRDP still achieved excellent performance. The performance
achieved with the LRDP for a 24- and a 48-h test i ndicated that with a single test the LRDP could detect leaks as small as 0.46 and 0.38 gal/h, respec tively, with a probability of detection of 95% and a probability of false alarm of 5%. By av eraging 4 or 5 tests t ogether, the performance improved by a factor of 2 or more for both methods.

The main problem with this evaluation was the limitations placed on the LRDP that were technically unnecessary. These limitations includ ed a 24-h waiting period (when none is actually required) and the inclusion of a 0.1-gal/h bias (due to the inflow and not th e system) in the use of a threshold for conducting a precision test at 0.2 gal/h. While this bias does not impact a monitoring test at 1, 2 or 3 gal/h, it would imp act a precision test. In addition, the inflow prevented the evaluation of the LRDP fo r a test duration shorter than 24 h.

Since the LRDP did not automatically report the test result at the conclusion of a test, the system was not approved for stand-alone monitoring. Inst ead, the analysis was au tomatically performed in a spreadsheet at the completion of a test. This latter constraint is not significant, because all the
criteria could be met for monito ring provided that an operator st art and stop a test, and then imported the data into a spreadsheet for analysis.

The LRDP was re-evaluated for perfor mance during this ESTCP project to

• eliminate the unnecessarily long waiti ng period imposed by the regulators,

• obtain approval to operate the system as an automatic monitoring system,

• obtain a more accurate estimate of performance that was not degraded by uncontrolled,
nonleak-related inflows and out flows during the test, and

• obtain approval for a test that could be c onducted in less than 24 h (i.e., overnight).

All of these objectives were met in th e second evaluation conducted under ESTCP.

The LRDP was operated in a fully automatic monitoring mode and was evaluated for test durations of 10 h and 24 h. A waiting period of 2-h wa s used just be sure that all operations had ceased before a test was begin.

The results of the first evaluation were listed by the NWGLDE for test durations of 24 and 48 h [19-26]. The new results are being submitted for approval for a 10- and 24-h test [8-15]. There are presently 12 approved ways to implement a l eak detection test with the LRDP system that change only in terms of test duration, testing frequency (mon itoring or tightness regulatory requirements), number of tests averaged together , and probability of false alarm [5]. The performance and operation of the system were designed to meet the California regulatory guidelines for bulk tanks [5], but have general app lication for all states. The system is currently approved by the NWGLDE for

• use as a portable system with a 24- and 48-h test (LRDP-24 or LRDP-48) [19-22],

• averaging multiple tests together (e.g., 4 or 5 tests) for increased reliability and/or increased detection sensitivity LR DP-24-5 or LRDP-48-4) [23-26],42 • a variety of monthly monitoring (0.3-1.0, 1.0- 2.0, and 2.0-3.0 gal/h) and precision testing (0.2 gal/h) regulatory options, and

• all vertical-walled tanks with capacities greater than 50,000 gal and diameters less than
140 ft.

When the results of the third-party evaluati ons performed under ESTCP are listed by the NWGLDE, the LRDP system will be approved for

• use as a stand-alone, in-tank monitoring system or as a portable system with a 10- and 24- h test (LRDP-10 or LRDP-24) [8-11],

• averaging multiple tests together (e.g., where the number of tests is less than 12) for increased reliability and/or increased detec tion sensitivity LRDP-10-n or LRDP-24-n) [12- 15],

• a variety of monthly monitoring (0.3-1.0-2.0, 2.0, and 2.0-3.0 gal/h) and precision testing (0.2 gal/h) regulatory options, and

• all vertical-walled tanks with capacities greater than 50,000 gal and diameters less than
194 ft.

5.2 Methods Evaluated

As described in Table 1, four LRDP test methods were evaluate d: (1) LRDP-24, (2) LRDP-24-n, (3) LRDP-10, (4) LRDP-10-n. Methods (3) and (4 ) allow individual test results from up to 12 tests to be averaged together before applying a threshold. As done in the first evaluation, for each of these test methods, the performance was estimated for four thresholds. As a consequence, for each method, there are four “versions” of the KWA evaluation report and four versions of the
method. An “a” in the version number is used to differentiate the LRDP -24 evaluated at North
Island from the LRDP-24 evaluated at Point Lo ma. The Point Loma results will replace the previous results for the LRDP-24. The LRDP -10 is a new method. Although this is a new method, a version number of “a” is also used to indicate it was evalua ted at Point Loma.

The performance was estimated for four thresholds to allow the method to be used as needed to satisfy regulatory and operational requirements and for direct comparison of the performance to other methods. The basic version, called Version a , sets the threshold to insure that the P D = 95% against the target leak rate and that the P FA is as small as possible and less than or equal to 5%. In this case, the TLR and P D (= 95%) can be the same for any tank diameter. However, if the threshold is selected in this way, the P FA will be different for each tank diameter, which is acceptable provided that the P FA < 5%. This method is used for the small regulated USTs found in petroleum service stations and is how the LR DP was intended to be used. However, the
NWGLDE would not let us use this approach for a number of r easons. First, the performance of the LRDP was too good, and the NWGLDE, comprised of regulators from st ates with bulk USTs,
were concerned that leaks smaller than the thre shold would go undetected, because they knew that the method had the performance to detect them us ing a smaller threshold. Second, they did not
want the P FA to be different for every tank tested, becau se they thought it w ould be confusing to tank owners. They wanted the P D and P FA to be the same for every tank and to allow the TLR to43 change.

Version 1.0a, which was reported previously to the NWGLDE for a 2.0 and 3.0 gal/h leak as Version 1.0, is reported here for leaks of 1.65 and 2.40 gal/h for the 24-h test and leaks of 1.90
and 2.40 for the 10-h test. These TLRs were select ed because it allowed the LRDP to address the 0.3-1.0-, the 1.0-2.0-, and 2.0-3.0-gal/h monthly monitori ng standards for all tank sizes. In this method, the NWGLDE required that a TLR be sel ected for the evaluation tank. This TLR would
then be scaled for the tank being tested, keeping the P D and P FA the same for tanks of different product surface areas. This method is different than “Version a,” because the selected TLR changes with tank diameter, but the P FA remains the same. In Version a, the TLR can be the same
for all tank diameters.

Version 1.1a is intended for use in California. For this version, the TLR for the evaluation tank
was selected so that it is less than or equal to twice the MDLR . For the LRDP-24, a TLR of 0.95 gal/h was selected, and for the LRDP-10 a TLR of 1.65 gal/h was selected. Both TLRs are less
than 2 * MDLR 1 . These TLRs are less than 2 * MDLR a nd were selected, because this choice of
TLRs allows the LRDP to be used to addre ss Option 7 or 10 of the California regulatory guidelines for monthly monitoring.

In Version 1.2a, the threshold was selected to give the MDLR, the sm allest leak rate that could be detected in a given tank and still insure a P D = 95% and a P FA = 5%. The MDLR is useful, because it is a simple way to compare the performance of different methods.

Ken Wilcox Associates, Inc., has prepared four evaluation reports (LRDP-24, LRDP-24-n, LRDP-10, LRDP-10-n) [8-11]. These reports in clude Version a of the standard EPA Results Form. The performance that corre sponds to the other three threshol d selections are presented in four more KWA reports that include only the Results Forms and the Method Description Forms for versions V1.0a, V1.1a, and V1.2a [12-15]. As state above, these performance results are reported identically to the results determined from the North Island ev aluation. This was done purposefully so that it should be straightforward for the NWGLDE to review and approve these updated results.

The performance results scales with the square root of the number of tests, n, averaged together, and linearly the product surface ar ea (PSA), which can also be expressed in terms of tank diameter (D). The formula used to compute th e threshold and TLR for a particular tank size are presented in Appendix E for Versi on a and Appendix F for the other three versions. Examples of
the results for all four versions are presented in Appendices G – J.

5.3 Results of the Le ak Detection Tests

An example of the level data measured with the LR DP in Test 10 for a 10-h test and a 24-h test is shown in Figures 19 and 20, respectively. The test s of the LRDP-10 were initiated at the same
time as those of the LRDP-24. The induced leak rate was 1.82 gal/ h, and the leak rate measured by the LRDP-10 was 1.80 gal/h and the LRDP-24 was 1.83 gal/h.

1 A TLR = 2 * MDLR for the LRDP-24 would equal 1.38 gal/h (2 * 0.69 gal/h), and a TLR = 2 * MDLR for the LRDP-10 would equal 2.28 gal/h (2 * 1.139 gal/h).44 The waiting period was initiated at 1500 on 11 Ma y 2000, and the test started 2 h later at 1700. The precision of the data (i.e., th e standard deviation of the data about a regression line fit to the data) is less than 0.0003 in. The data do not exhi bit any evidence of ambi ent diurnal temperature effects on the differential pressure sensor or the reference tube m ounting system. The linearity of the 24-h data in Figure 20 suggests that the volume rate estimated with these data should be about the same for both the 10-h and 24-h test periods.

A 1-h periodicity is obser ved in the level data
obtained for this test and several other tests. In some tests this periodicity was 2 to 3 h. This periodicity is consistent with the presence of internal waves in the tank. This periodicity was
not observed in the San Pedro data shown in Figure 21. It is likely that the geometry of this specific tank is such that a resonance condition is sometimes established. The amplitude of these
fluctuations observed du ring the other 11 tests ranged from a factor of th ree higher and lower.
These fluctuations do not affect the results of
either the 10- or 24-h tests. The main effect is that a test must include 3 to 5 cycles to achieve a stable performance. If the evaluation had been completed in the tank at San Pedro, it is likely that
a 4- to 8-h test would have been evaluated.

The results of the leak detection tests for
the LRDP-10 and the LRDP-24 were
tabulated in Tables 7 and 8. These test results are presented graphically in Figures
22 and 23 for the LRDP-10 and the LRDP24. Each test result is plotted against the leak induced for that test. In Figure 22, the test results measured by the LRDP systems appear on the y-ax is, while the KWAinduced leak rates appe ar on the x-axis. A least-squares line has been fitted to the results of the tests with each LRDP system. The slope of the line is nearly 1.0 (1.039
for the LRDP-10 and 0.979 for the LRDPy = 1.0389x - 0.0673

R 2 = 0.9434 y = 0.979x - 0.0966

R 2 = 0.8415

-2.500 -2.250 -2.000 -1.750 -1.500 -1.250 -1.000 -0.750 -0.500 -0.250 0.000 0.250 0.500

-2.250 -2.000 -1.750 -1.500 -1.250 -1.000 -0.750 -0.500 -0.250 0.000
Induced Leak Rate - gal/hMeasured Volume Rate - gal/h

LRDP-10 LRDP-24 Linear (LRDP-24) Linear (LRDP-10)

Figure 22. Least-squares lines fitted to the test results of
the LRDP-10 and the LRDP-24. -60 -50 -40 -30 -20 -10

0 10 20

0 2 4 6 8 10 12 14 16 18 20 22 24

Time - hVolume - gal

Figure 20. Level data obtained with the LRDP-24 system for Test 10. -25 -20 -15 -10 -5 0 5 10 15

0 1 2 3 4 5 6 7 8 9 10

Time - hVolume - gal

Figure 19. Level data obtained with the LRDP-10 system for Test 10.

0.565 0.567 0.569 0.571 0.573 0.575

0 50 100 150 200

Elapsed Time (hours)Differential Level (inches)

0 20 40 60 80 100 120Temperature (deg F)

Level BoxTemp

Figure 21. Level data obtained with the LRDP system over a 96-h period in a 132.5-ft-diameter tank
at San Pedro.45 24); this indicates that the volume changes due to the induced leaks are additive with any other volume changes in the tank. The intercepts for the LRDP-10 and the LRDP-24 systems, -0.097 and -0.067 gal/h, respectively. A statistical hypothesis test at a level of significance of 0.05 shows that the intercepts are not different from zero.

This is more easily seen in the error plot shown in Figure 23. The error plotted on the y-axis is the difference between the
induced leak rate and the leak rate measured by the LRDP system for both
test durations. The mean and standard
deviation of the test results for each system, after the induced leak has been subtracted out, are summarized in Table
10. The standard deviation of the 10-h test is nearly 70% larger than the standard deviation of the 24-h test, which is consistent with expectation.

Table 10. Mean and Standard Deviation of the Difference between the Measured Leak Rates (Test Results) and
Induced Leak Rates for the LRDP-10 and LRDP-24

Type of
LRDP System Number of Tests Mean Volume Rate (gal/h) Standard Deviation (gal/h)

LRDP-10 12 0.080 0.318

LRDP-24 12 0.097 0.192

A two-sided statistical hypothesi s test, as required by the evalua tion protocol, was performed to determine if the mean was statistically different from zero. The results of a two-sided Student-t test conducted at a level of signi ficance of 0.05 was that the mean c ould not be distinguished from
zero. The critical Student- t statistic is 2.20 and th e computed statistics for the LRDP-10 and the LRDP-24 were 0.878 and 1.750, respectively. This means that the mean computed in the
evaluation does not have to be in cluded in the threshold as a syst em bias. This is significant,
because the mean was shown to be statistically signifi cant in the first evaluation. Even though the NWGLDE recognized that this non-zero mean was produced by nonleak-related inflows and was not a bias of the method, they were requiring that the thresh old include the mean,
which when used would have resulted in an unacceptably high probability of false alarm. The present evaluation shows that the bias computed in the first evaluation was not real.

Figure 24 shows the cumulative frequency distributions (CFDs) of th e test results, with the dashed line denoting the LRDP-10 and the solid line denoting the LRDP-24. These CFDs were generated after the induc ed leak rate and the 0.000 0.200 0.400 0.600 0.800 1.000

-0.750 -0.500 -0.250 0.000 0.250 0.500 0.750
Volume Rate - gal/hCumulative Frequency LRDP-10 LRDP-24

Figure 24. Cumulative frequency distributions of the
test results in a 122.5-ft-diameter bulk UST after the
volume chan g es due to the induced leak were removed. -0.750 -0.500 -0.250 0.000 0.250 0.500 0.750

-2.250 -2.000 -1.750 -1.500 -1.250 -1.000 -0.750 -0.500 -0.250 0.000
Induced Leak Rate - gal/hMeasured Volume Rate - gal/h LRDP-10 LRDP-24

Figure 23. Difference between the induced leak rate and the
volume rate measured with the LRDP-10 and the LRDP-24.46 mean inflow had been subtracted. Based on the CDF of the LRDP-10 and the LRDP-24, a threshold set at volume rates greater than –0.5 and –0.25 gal/h, respectively, would have resulted in no false alarms during the evaluation.

The difference in performance between the LRDP-10 and the LRDP-24 can be attributed to one
or two of the evaluation tests. If the LRDP-10 measured the same result as the LRDP-24 for Tests 2 and 3, the mean and standard deviat ion of the LRDP-10 would be 0.066 gal/h and 0.226 gal/h, respectively, which means th e performance of the LRDP-10 is similar to the LRDP-24 for most tests. Although its quoted performance is not nearly is good, in operation, it will give similar results for 80% of the tests conducted.

The LRDP was also evaluated for an 18-h test wi th a 6-h waiting period. The mean and standard deviation was 0.080 gal/h and 0.198 gal/h, respectively. The performance of the LRDP using this test protocol is nearly the same as LRDP us ing a 24-h test with a 2-h waiting period and would result in a MDLR of 0.713 gal/ h, as compared to an MDLR of 0.690 gal/h for the 24-h test.
While the difference between the LRDP-24 a nd the LRDP-18 was only 0.02 gal/h, a 12-test average would not quite meet th e 0.20-gal/h precision test standard with the LRDP-18 for the
evaluation tank. For this reason and because the to tal test time for both methods is about the same and a 24-h test has already been approved by the re gulators, only the 10-h and 24-h test protocols
were evaluated.

5.4 Performance Estimates for a Si ngle Test (LRDP-10 and LRDP-24)

Estimates of the performance of the LR DP-10 and the LRDP-24, in terms of P D and P FA , were generated for the evaluation tank from the standard deviation of the test results given in Table 10. The formula for computing performance is presente d in Appendix E. In Table 11, the thresholds
used for detection were selected so as to maintain a P D of 95% and a P FA of 5%. As stated above, for such a threshold, the resulting leak rate is called the minimum detectable leak rate (MDLR).

Table 11. Performance Estimates for the LRDP-10 and the LRDP-24

Type of
LRDP System Threshold

(gal/h) Leak Rate

(gal/h) Probability of
False Alarm (%) Probability of
Detection (%)

LRDP-10 0.570 1.14* 5.0% 95.0%

LRDP-24 0.345 0.69* 5.0% 95.0%
* For these thresholds, the leak rate is also referred to as the minimum detectable leak rate (MDLR).

The performance of these two systems against la rger leaks in the evaluation tank is shown in Table 12. The thresholds set for these performance estimates were selected so as to maintain a P D of 95% and to make the P FA as small as possible. In order for the LRDP-10 to maintain a P D = 95% against a leak rate that is larg er than 1.14 gal/h and still have a P FA < 5%, the threshold should be less than the leak rate by 0.57 gal/h or more and no smaller than 0.57 gal/h. In this case, a threshold anywhere from 0.57 to 1.43 gal/h c ould be used if the leak rate is 2.0 gal/h. Similarly, in order for the LRDP-24 to maintain a P D = 95% against a leak rate that is larger than 0.69 gal/h and still have a P FA < 5%, the threshold should be less than the leak rate by 0.345 gal/h or more and no smaller than 0.345 gal/h. In this case, a threshold anywhere from 0.345 to 0.655 gal/h could be used if the leak rate is 1.0 gal/h.; a threshol d anywhere from 0.345 to 1.655 gal/h47 could be used if the leak rate is 2.0 gal/h. B ecause the evaluation is based on only 12 tests, the

P FA is reported as very much less than 1% (<< 1%) if the calculated P FA is a factor of ten or more smaller than 1.0%. Additional performance result s as a function of TLR and tank diameter are presented in Appendices I and J.

Table 12. Performance Estimates for the LRDP-48 and the LRDP-24 against Larger Leaks

Type of
LRDP System Threshold

(gal/h) Leak Rate

(gal/h) Probability of
False Alarm (%) Probability of
Detection (%)

LRDP-10 1.43 2.0 <<1.0% 95.0%

LRDP-10 0.93 1.5 0.7% 95.0%

LRDP-24 1.655 2.0 <<1.0% 95.0%

LRDP-24 1.155 1.5 <<1.0% 95.0%

LRDP-24 0.655 1.0 <1.0% 95.0%

The smallest leak rate that is detectable in the evaluation tank with a 24-h test with a P D = 95%
and a P FA = 5% was 0.69 gal/h This scales to a detect able leak rate of 0.3 6 gal/h in an 88-ftdiameter tank, the diameter of the bulk UST used in the first evaluation at North Island. In the previous evaluation, the MDLR for a 24- a nd a 48-h test was 0.45 gal/h and 0.38 gal/h respectively. Thus, once the inflow problem s experienced during the first evaluation are eliminated, the LRDP-24 performs slightly bette r than the LRDP-48 evaluated at North Island.

5.5 Performance Estimates for More than One Test (LRDP-10-n and LRDP-24-n)

The performance of the LRDP-10 and the LRDP -24 (or any leak detection system) can be improved significantly by combining the results of tw o or more tests. Averaging two or more test results before applying the threshold will improve both the probability of detection and the probability of false alarm over that obtained fo r a single test. Performance improves as the number of tests averaged together increases. The performance will depend on the test duration and the number of tests, n, averaged together. Fo r example, the performance of the LRDP-10-4 is a factor of 2.0 (square root of 4) times better than a single 10-h test with the LRDP-10; the LRDP10-4 uses a test duration of 10 h and averages four 10-h tests together.

The performance of the LRDP-10-n and LRDP -24-n systems, where n is the number of independent tests averaged t ogether, is obtained using the standard deviation of the mean test result, S

m , of the LRDP-10 and LRDP-24 systems. The st andard deviation of the mean test result
can be determined from the standard deviation of the single-test results, S, computed in the thirdparty evaluation. Once the standard deviation of the mean test result is known, the performance of the mean (average) te st result (in terms of P D and P FA ) can be computed using the same methods as for the single test results.

For independent tests, S

m of the LRDP-10 and LRDP-24 is obt ained from S and the number of tests, n, averaged together. The standard deviation of the mean, S

m , is given by

S
m = S /(n) 0.5

.48 For the LRDP-10 and the LRDP-24, values of n th at yield an MDLR of 0.2 gal/h or less were purposely selected. This equates to a system capable of detecting a 0.2-gal/h leak with a P D = 95% and a P FA < 5%. In this way, the LRDP-10 and th e LRDP-24 could meet the annual testing requirements for bulk tanks established by the stat e of California. Table 13 summarizes the mean
and standard deviation of the m ean test result for the LRDP-10-n and the LRDP-24-n for different
values of n in the evaluation tank. Table 14 summ arizes the performance in terms of the MDLR.

Table 13. Mean and Standard Deviation of the Difference between the Measured Test Results and Induced Leak Rates for the LRDP-10-n and LRDP-24-n for n = 4, 6, and 12

Type of
LRDP System Number of Tests Averaged Together Mean Volume Rate

(gal/h) Standard Deviation
of the Mean (gal/h

LRDP-10-1 1 -0.080 0.3175

LRDP-10-4 4 -0.080 0.1588

LRDP-10-6 6 -0.080 0.1296

LRDP-10-12 12 -0.080 0.0917

LRDP-24-1 1 -0.097 0.192

LRDP-24-4 4 -0.097 0.096

LRDP-24-6 6 -0.097 0.0784

LRDP-24-12 12 -0.097 0.0055

Table 14. Performance Estimates Made for the LRDP-10-n and the LRDP-24-n Systems

Type of
LRDP System Threshold (gal/h) Leak Rate (gal/h) Probability of
False Alarm (%) Probability of
Detection (%)

LRDP-10-1 0.57 1.14 5.0% 95.0%

LRDP-10-4 0.285 057 5.0% 95.0%

LRDP-10-6 0.233 0.465 5.0% 95.0%

LRDP-10-12 0.165 0.329 5.0% 95.0%

LRDP-24-1 0.345 0.690 5.0% 95.0%

LRDP-24-4 0.173 0.345 5.0% 95.0%

LRDP-24-6 0.141 0.282 5.0% 95.0%

LRDP-24-12 0.100 0.199 5.0% 95.0%

The average test result is important because it allo ws the same in-tank leak detection system to meet both the 0.3-1.0 or 1.0-2.0-gal/h monthly monitoring and the 0.2-gal/h annual leak testing requirements established by the state of Californi a for bulk tanks. All of the LRDP systems can easily meet the monthly testing requirements with a very low probability of false alarm (<1%).49 With averaging, all of the bulk USTs owned or operated by the DoD can also meet the precision test requirements.

5.6 Formula to Compute the Threshold and Targ et Leak Rate as a Function of Tank
Diameter for the LRDP-10 and LRDP-24

The performance of a leak detection system can be affected by the size and geometry of the tank. This relationship is not quanti tatively understood for volumetric methods, but is predictable for mass-based systems. For most mass-based techno logies, performance is related to the surface area of the fuel in the tank (but not the volume of fuel in the tank).

The evaluation protocol specifies that the threshol d for declaring a leak must be adjusted when testing tanks that are smaller or larger than th e tank used in the evaluation. For a mass-based system, the threshold and the TLR are obtained from the ratio of the surface area of the tank being
tested and the surface area of th e tank used in the evaluation.

According to the evaluation protocol [6], th e maximum tank size to which a mass-based method may be applied is determined by the surface area of the tank and is limited to two and one-half
times the surface area of the tank used in the ev aluation. Since the surface area of the 122.5-ft diameter, 2,100,000-gal tank used in this evaluation is 11,756 ft 2 , the LRDP-10 and the LRDP-24 can be used to test tanks with diameters up to 193.4 ft. The maximum tank capacity (in terms of volume of fuel in the tank) that can be tested with the LRDP systems is not constrained by the evaluation and will depend on the height of the tank.

As discussed previously in this report, the NWGLDE would not list the LRDP using a threshold
established to maintain a P D = 95% against the target leak rate. Instead, thresholds were selected against two leak ra tes using a set P FA and a P D = 95% (Version 1.0a), a TL R less than or equal to 2 * MDLR using a set P FA and a P D = 95% (Version 1.1a) , and the MDLR (Version 1.2a). Tables 15 and 16 present the formula for co mputing the thresholds and target leak rate as a function of tank diameter, D, (or product surfac e area) and number of tests, n, averaged for the LRDP-10 and LRDP-24, respectively. The tables also gives the largest tank di ameter for which the MDLR is 0.2 gal/h or less. The formula are based on a product surface area for the 122.5-ft-diameter evaluation tank of 11,786 ft 2 . A more complete set of formula for these versions are presented in Appendix F.

Table 15. Formula to Compute the Threshold and Target Leak Rate as a Function of Tank Diameter for the LRDP-10

Method Tank Diameter Target Leak Rate (Probability of detection of

95% with a probability of false alarm of 5%)
Version 1.2a For tank diameters less than 51.3 ft For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [2,635.0*(n) 0.5 ] 0.5 (LRDP-10-n) 0.20 gal/h (3.14*(D*0.5) 2 /11,786)*1.139 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of

95% with a probability of false alarm of 0.29%)
Version 1.1a For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [1,817.3*(n) 0.5 ] 0.5 (LRDP-10-n) (3.14*(D*0.5) 2 /11,786)*1.653 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of

95% with a probability of false alarm of <0.15%)
Version 1.0a For tank diameters (D in ft) up to 193.4 ft For tank diameters (D in ft) up to 193.4 ft (3.14*(D*0.5) 2 /11,786)*(2.0-0.569) gal/h (3.14*(D*0.5) 2 /11,786)*(3.0-0.569) gal/h50 Table 16. Formula to Compute the Threshold and Target Leak Rate as a Function of Tank Diameter for the LRDP-10

Method Tank Diameter Target Leak Rate (Probability of detection of

95% with a probability of false alarm of 5%)
Version 1.2a For tank diameters less than 66.0 ft For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [4,349.7*(n) 0.5 ] 0.5 (LRDP-24-n) 0.20 gal/h (3.14*(D*0.5) 2 /11,786)*0.69 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of

95% with a probability of false alarm of 0.48%)
Version 1.1a For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [3,172.4*(n) 0.5 ] 0.5 (LRDP-24-n) (3.14*(D*0.5) 2 /11,786)*0.946 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of

95% with a probability of

false alarm of <0.003%)
Version 1.0a For tank diameters (D in ft) up to 193.4 ft For tank diameters (D in ft) up to 193.4 ft (3.14*(D*0.5) 2 /11,786)*(2.0-0.345) gal/h (3.14*(D*0.5) 2 /11,786)*(3.0-0.345) gal/h

Tables 17-19 further summarize the results of th e evaluation. Table 17 gives the MDLR for n = 1, 4, 6, and 12 for three tank sizes. This table also presents the results from the previous evaluation for comparison. A more complete pres entation of the results for these versions are presented in Appendices G and H.

Table 18 gives the largest
tanks in which the LRDP10, LRDP-10-n, LRDP24, and LRDP-24-n can meet the precision test TLR requirement of 0.20 gal/h with two different

P FA s. Table 19 gives the largest tank diameters in
which the LRDP-10 and
the LRDP-24 can meet the monthly monitoring standards of 0.3-1.0, 1.0- 2.0, and 2.0-3.0 gal/h. Also, Table 18 shows that an annual precision test can be conducted in any
tank with a diameter of
less than 51 ft with a P FA = 5%, which covers over 50% of the bulk USTs. The LRDP-10 can also be used to meet the precision requirement using a single test at a P FA = 0.3% for all tanks with diameters less than 43
ft. Table 19 shows that the LRDP-10 can be used to address the 0.3-1.0-gal/h and the 1.0-2.0- gal/h monthly monitoring requirement for tanks with diameters up to 95 and 135 ft. respectively, with a very low P FA (0.3%). This covers the full range of bulk USTs owned or operated by the

DoD. Table 17. Example of the MDLR in gal/h (P D = 95% and a P FA = 5%) as a
Function of Tank Diameter

Method PD-% PFA-% Target Leak Rate - gal/h
for tank diameters of 122.5 ft 88 ft 60 ft

LRDP-10 95% 5% 1.14 0.59 0.27
LRDP-10-4 95% 5% 0.57 0.29 0.14*

LRDP-10-6 95% 5% 0.46 0.24 0.11*

LRDP-10-12 95% 5% 0.33 0.17* 0.08*

LRDP-24 95% 5% 0.69 0.36 0.17*

LRDP-24-4 95% 5% 0.35 0.18* 0.09*

LRDP-24-6 95% 5% 0.28 0.15* 0.07*

LRDP-24-12 95% 5% 0.20 0.10* 0.05*

LRDP-24* 95% 5% 0.89 0.46 0.21
LRDP-48* 95% 5% 0.74 0.38 0.18*

* Although the computed MDLR is less than 0.20 gal/h, the performance of the system must be reported and the system operated at 0.20 gal/h.51 As shown in Table 19, with the LRDP-24, the 0.3 – 1.0- gal/h monthly monitoring requirements can be
addressed for all but a few of the largest bulk USTs owned by DoD. The advantage of using the 0.3 – 1.0-gal/h criterion is that only a single precision test at 0.2 gal/h is required each year. Table 19 shows that
the LRDP-24 can be used to address the 0.3 – 1.0-gal/h and the 1.0 – 2.0-gal/h monthly monitoring requirement for tanks with diameters up to 126 and 178 ft. respectively, with a low P FA (0.5%). This covers the full range of bulk USTs owned or operated by the DoD. Als o, Table 18 shows that an annual precision test can be conducted in any tank
with a diameter of 66 ft with a

P FA = 5%, which covers over
50% of the bulk USTs. If a precision test is conducted with the LRDP-24, then all of
the 88-ft-diameter tanks at the
North Island fuel farm can be tested in compliance with California regulations by conducting a precision test four times a year.

5.7 How to Use the LRDP System

The LRDP system gives the tank owner or opera tor great flexibility in developing a testing strategy for meeting the monthly monitoring and th e precision test regulat ory requirements. The overnight testing capability of the LRDP-10, the high performance of the LRDP-24, and the capability for averaging tests together allow a testing strategy to be developed that includes both methods. A testing strategy, which is both cost effective and mini mizes disruption to operations, can be developed. Tables 18 and 19 suggest how the system may be used; also see Appendices G
- J for more detail. The detailed calculations can be made using the formula in Tables 15 and 16; Appendices E and F give additional detail.

Appendices G and H present the results for the LRDP-10 and th e LRDP-24, respectively, for all four versions of each method (a, 1.0a, 1.1a, and 1.2a) for a sufficient number of TLRs to design a testing strategy without using th e equations in Appendices E and F. The four tables in each appendix present the target leak ra te, threshold, standard deviation, P D and P FA for specific target leak rates of interest and specific tank diameters of interest. These results will indicate which size
tanks can be tested with the LRDP-10 and the LRDP-24 to meet the 0.2, 0.3-1.0, 1.0-2.0, and 2.0-

Table 18. Largest Diameter Tank in which a 0.20 gal/h Leak Rate Can Be
Detected as a Function of the Numb er of Tests Averaged Together*

Method P D P FA TLR-gal/h
For Tank Diameters <

n=1 n=4 n=6 n=12

LRDP-10-n 95% 5.0% 0.20 51 ft 73 ft 80 ft 96 ft

LRDP-10-n 95% 0.3% 0.20 43 ft 60 ft 67 ft 79 ft

LRDP-24-n 95% 5.0% 0.20 66 ft 93 ft 103 ft 123 ft

LRDP-24-n 95% 0.5% 0.20 56 ft 80 ft 88 ft 105 ft

*P D = 95% and a P FA < 5% for the LRDP-10, LRDP-10-n, LRDP-24, and LRDP-24-n as a Function of Tank Diameter and Averaging (n = 1, 4, 6, 12)

Table 19. Largest Diameter Tank in which Various Leaks Can Be Detected as a Function of Target Leak Rate*

Method P D P FA Tank Diameters for TLRs in gal/h

for TLR in gal/h = 0.30 1.0 2.0 3.0

LRDP-10 95% 0.3% 52 ft 95 ft 135 ft 165 ft

for TLR in gal/h of 0.30 1.0 2.0 3.0

LRDP-24 95% 0.5% 69 ft 126 ft 178 ft 218 ft

*P D = 95% and a P FA < 5% for the LRDP-10 and the LRDP-2452 3.0 gal/h precision and monthly monitoring standard s. The table also indicates how many tests need to be averaged to detect 0.2 gal/h. The st andard deviation, which is used to estimate the performance, is also shown. Appendices I a nd J present the results for the LRDP-10 and the LRDP-24, respectively, for Version a, as a function of tank size, for the TLRs of interest (0.2, 0.3, 1.0, 2.0, and 3.0).

The guiding principle that should be used when developing a testi ng strategy is to minimize the probability of a false alarm. Any P FA that is less than 1% will su ffice, but it is highly desirable to
have the P FA < 0.1%. Experience shows that the P FA computed using a normal distribution, as required by the EPA standard test procedures, is reasonably accurate for estimating the P FA at 5%
but results in a lower than observed P FA for P FA s < 1%. A P FA of about 0.01% really results in a

P FA of about 0.1%.

The performance of the 10-h test is sufficiently good that almost all of the monthly monitoring tests, regardless of tank size, can be conducted us ing a 10-h test. For ta nks with diameters less than 51 ft, the 10-h test could also meet the 0.2-g al/h precision testing cr iterion established by the State of California. By averaging 4 tests together ta nks as large as 73 ft in diameter could be test. When the LRDP was used for monitoring at 1.0, 2.0 or 3.0 gal/h, both tests had a P FA < 0.3% for all tanks owned or operated by DoD.

All three of the testing options described in Tabl e 1 can be used. As indicated by Tables 18 and 19, for the smaller bulk USTs, the LRDP-10 or LRDP-24 to meet the 0.2-gal/h monthly monitoring requirement outright. However, it is probably more cost efficient and less disruptive to operations for 12 monthly tests to be perf ormed using the 0.3 – 1.0-gal/h monthly monitoring option and one annual test at 0.2 gal/h than 12 m onthly tests at 0.2 gal/h. This latter approach minimizes the potential for false alarms and pr ovides excellent environmental protection well within the regulatory standards. If this latte r approach is used, small valve weeps would not interfere with the monthly monitoring testing. For the largest DoD bulk USTs, the only available strategy may be to use the LRDP-24 and test at 0.2 gal/h.

The exact option to select for the tank owner/ope rator to use will depend on the size of bulk USTs at the facility. The provider of the LRDP can help the tank owner/operator design a testing program that is best for the facility. The first step in the design process is to determine which LRDP system can be used for monitoring and wh ich LRDP system can be used for precision testing with the fewest tests to be averaged and the lowest P FA that can be used. Once this is completed, a test protocol which is uses the mi nimum number of testi ng combinations (methods and versions) should be selected. The added time required to design the testing program in the beginning will have great benefits once it is implemented.

5.8 Results of the DEM/VAL of the LRDP in a 50,000-gal UST

The LRDP was successfully demonstrated at the Hunter Army Airfield in a 50,000-gal UST. All of the DEM/VAL objectives were met. First, it wa s demonstrated that the LRDP can be used as a portable leak detection system. The system was unpacked, pressure tested, installed and bled in less than a day. Also, the system was removed fr om the tank and packed up in less than a day. Though there were two people on-site at all times, for this size of system, a single person could easily install, bleed and remove the system.53 Second, upon installation, the level of the product in the tank was measured with the
LRDP. The level measured with the LRDP
was within 0.1 in. of the level measured with a tape measure. This is within the 1/8 in. (0.125 in.) regulatory requirement for inventory level

measurements.

Third, a calibration check was performed next to verify that the height-to-volume conversion factor to use for the testing. This was accomplished by adding a gallon of fuel and measur ing the level change with the LRDP. As shown in Figure 25, this addition was easily m easured by the LRDP. At 74 % capacity, a one gallon volume change is equivalent to approximately a 0.002 i n. level change.

Fourth, four 24-h leak
detection tests were conducted.
The first two tests showed an inflow of ~ 0.25 gal/h. Upon further investigation, it was found that the system had not been properly bled. When this problem was corrected, the
tank was tested with the LRDP for leaks using a target leak criterion of 0.1 gal/h. The test result was a PASS, because the
measured volume rate of 0.014 gal/h was less than a threshold of 0.05 gal/h. The final leak detec tion test was the demonstration of the system for the Hunter personnel. A 74-h data set was obtained (Fi gure 27). The data in Figures 26 and 27 were post analyzed to evaluate the performance of the system using shorter test periods. The results are
tabulated in Table 9 for test
durations of 8 h and 24 h. These preliminary results show that a leak rate criterion of 0.2-gal/h should be achievable in 50,000-gal tanks with only an 8-h test period. The results are presented graphically in Figure 28, and the statistics are summarized
in Table 20 for both test durations. -2.000 -1.500 -1.000 -0.500 0.000 0.500 1.000 1.500 2.000

0 2 4 6 8 10 12 14 16 18 20 22 24

Time - hVolume - gal

c

Figure 26. Volume data from a 24-h leak detection test with the LRDP-24. 0.36 0.361 0.362 0.363 0.364 0.365 0.366

12.6 12.8 13 13.2

Time (hours)Diff. Level (inches) One Gallon Added to Tank

Figure 25. Height-to-volume calibration level data in a 50,000- g al UST.

41.4 41.6 41.8

42 42.2 42.4 42.6 42.8

43 43.2 43.4

12 36 60 84

Time - hLevel Change - gal

Figure 27. Volume data obtained from 74-h of measurements with
the LRDP.54 This demonstration provided an opportunity to learn additional information regarding the deployment of the LRDP. First, the importance of properly "bleeding" the system was demonstrated. Bleeding the system refers to the act of purging any air-bubbles that may be trapped in the LRDP tubing and which may contribute to
erroneous level measurements. Originally, it was thought that adequate purging would take place if the system was installed

in a near-full tank with the
reference tube valve closed. When the LRDP is resting on the bottom, with the reference tube empty, the valve is then opened so that the fuel will rush through the plumbing and fill the tube.
The head of fuel in a near-full tank was thought to be adequate to flush out any air bubbles. Two subsequent 24-h tests
showed substantial level trends on the order of +0.4 gal/h and +0.2 gal/h, respectively. Because the tank was completely
isolated from the fuel lines and a
test for water infiltration was ne gative, we knew that the tank ha d no actual inflow and that the system results were erroneous.

To address this problem, the system was repurged. The procedure was to close the valve, fill the reference tube to the top, pull th e system up through the riser just to the point wher e the valve is still below the fuel surface, and open the valve so the fuel column in the reference tube will rush back through the plumbing until the DP cell readi ng is within 0.5 inches. Next, the valve is closed and the system is lowered to rest on the bo ttom. The valve is then opened to allow the fuel to rush back into the plumbing to fill the refe rence tube. This proce dure was performed twice,
and the volume rate obtained in a su bsequent 24-h test was 0.014 gal/h.

The need to perform extensive bleeding of the LRDP is a key finding of this DEM/VAL. The current design for the LRDP maintains the refere nce tube isolation valve in the open position when a test is not being conducted. It is possible that air bubbles may have gotten into the system when the tank was drained and the system was not effectively bled during the subsequent fill. A -0.2 -0.15

-0.1 -0.05 0 0.05

0.1 0.15

0.2

0 20 40 60 80 100

Time - hTest Result - gal/h 8 h 24 h

Figure 28. Estimate of performance made for the LRDP in a 50,000- gal UST. Table 20. Estimate of performance for the LRDP made for an 8-h and a 24-h test duration on a 50,000-gal UST.

Performance Parameters

8 h 24 h
November 19-20, 1999 Data

Test Duration – h Mean – gal/h 0.000 0.006 Standard Deviation – gal/h 0.047 0.010

Count 13 4 Threshold – gal/h 0.084 0.023 MDLR –gal/h 0.168 0.047

Precision Test MDLR – gal/h 0.200 0.200 Precision Test Threshold –gal/h 0.116 0.177

Precision Test P FA 1.5% < 0.001%55 standard procedure for bleeding the system, including valve control logic changes, was implemented prior to the installation at Pt. Loma.

We also found that not having the system mounted permanently made it susceptible to a noise
level of a factor of 2 to 3 times higher than expected. This was due to two factors: (1) the system
"rocked" a bit due to the curv ed bottom of the tank, and (2) any motion of the conduit due to wind/bumping/etc. induced this rocking motion. We showed that this problem existed by "jiggling" the conduit manual and th en noting that the LRDP did not return to the exact previous position (before rocking), resulti ng in a step of 0.001 inch, or 0.5 gallons. This problem can be alleviated by shaping the bottom of the LRDP to better fit th e bottom of the tank.

An oscillation with a 2 to 3 h period is also pres ent in the data collected during the first week of the installation (Figure 26). The peak-to-peak am plitude of this oscillation is about 0.001 inches or about 2 to 3 times the amplitude of the ra ndom background noise. While the source of this oscillation is unknown, this periodicity is consistent with those of internal waves. The oscillation was not present in later data sets, such as the 74- h data set. In addition, there is a small diurnal component to the signal that does not get compen sated, on the order of 0.001 in. This may be due
to thermal effects on the conduit that cause th e LRDP to "rock", as discussed previously.

5.9 Results of the DEM/VAL of the LRDP in a 132.5-ft Diameter Bulk UST at San Pedro

Figure 21 showed a 74-h data se t obtained in a 132.5-ft diamet er bulk UST at San Pedro. Superimposed on the level data is the temperat ure of the electronic package located in the embedded controller. This figure illustrates a nu mber of important charac teristics of the LRDP system. First, the diurnal temperature cha nges observed in the embedded controlled are not present in the compensated level data. This indicates that the compensation algorithm is effective. Second, the random fluctuations about the mean level change is representative of the system noise and the random background noise. Fo r these data, the fluctuation level is 0.005 in., which is somewhat higher than the precision of th e level measurement capability of the system. Third, the mean trend suggests an outflow from the system of 0.1 gal/h, which is most probably associated with a valve that did not fully close. The tank is located at the top of a hill and product transfers are made under gravity flow from the tank.

A preliminary estimate of performance was ma de using the data obtai ned during the system checkout (Table 21). The performance estimate was made eight 24-h tests and assuming that the valve flow leakage was zero. The performance obtai ned indicated that the LR DP could be used to

Table 21. Summary of the Results of Eight 24-h Tests with th e LRDP in the San Pedro Tank after the Mean Flow
Was Removed.

Test
Duration
(h) Tank
Diameter
(ft) Number

of Tests Leak Rate (gal/h) Probability of
False Alarm (%) Probability of
Detection (%)

12 132.5 18 0.46 5.0% 95.0%

24 132.5 8 0.26 5.0% 95.0%

12 88 18 0.133 5.0% 95.0%

24 88 8 0.069 5.0% 95.0%56 test the largest diameter bulk USTs owned and operated by the DoD. The performance obtained, when scaled for comparison of the previous eval uation results in an 88-ft-diameter tank, was over twice as good as obtained in the first evaluation. The results also suggested that a test duration that was shorter than 24 h would be possible. Th e MDLR determined from a sample of eight 24-h tests was 0.26 gal/h in the 132.5-ft diameter ta nk and 0.15 in the 88-ft-diameter tank. The tests conducted at San Pedro were a precursor to the Point Loma evaluation, and the results of the measurements made at San Pedro justified switching sites to co mplete the evaluation.57 

### 6.0 Cost Assessment

This section summarizes the cost and cost savi ngs achievable with the LRDP for testing bulk USTs. This section also compares the cost of the LRDP to other in-tank mass-based systems and external systems such as tracer-based systems. The cost advantages of the LRDP are realized because of the extremely high performance of th e LRDP, the on-line, monitoring capability of the LRDP when permanently installed in a tank, the cap ability of the system to conduct a short test (an overnight test), and the lo w recurring costs associated with routine testing to address regulatory requirements.

Two DEM/VALs of the technology were conduc ted. The cost of these DEM/VALs are
summarized in Table 22. The first DEM/VAL wa s to install an LRDP system in a 2,100,000-gal bulk UST (Tank 175) at the Point Loma Fuel Te rminal, San Diego, California, and to conduct a third-party evaluation to determine performance. The second DEM/VAL was to conduct a series of tests with the LRDP in a 50,000-gal shop-fabri cated UST (Tank 45) at Hunter Army Airfield, Savannah, Georgia. With the exception of the re ference tube, the same LRDP system was used
for both DEM/VALs. The DEM/VAL costs include an initial site visit, installation, checkout, and removal of the equipment, and conduct of the DEM/VAL (data collection, analysis, and briefing of the results). The DEM/VAL at Point Loma required the collection of data over a 2-month period to check out the system and over a 3-mont h period to conduct the th ird-party evaluation. The DEM/VAL at Hunter was only a demonstrati on of the technology and was completed in less
than two weeks.

Table 22. Summary of the Costs of the Two DEM/VALs of the LRDP System

DEM/VAL Cost of the
DEM/VAL Cost of the Third-Party
Evaluation Total

Point Loma Fuel Facility $75,000 $45,000 $120,000 Hunter Army Airfield $25,000 N/A $25,000

Total $100,000 $45,000 $145,000

Section 6.1 summarizes the estimated cost of the LRDP, and Section 6.2 compares the approximately cost of other in-tank mass-based methods and tracer-based methods to the LRDP system. Section 6.3 discusses the potential cost avoidance savings associat ed with the use of a reliable leak detection system like the LRDP. Finally, Section 6.4 summarizes the approximate cost of the parts used to manufacture the LRDP.

6.1 Cost Performance

The total life-cycle cost of leak detection includes the following items:

• Cost of Regulatory Compliance: Purchase, installation, and ope ration of a leak detection system (direct and recurring costs)58 − Purchase price of the leak de tection system (direct cost)

− Installation of the system (direct cost)

− Training (direct a nd recurring cost)

− Maintenance (recurring cost)

− Cost of testing in meeting regulatory compliance requirements (recurring cost)

− Cost of shutting down operations for testing (recurring cost)

− Cost of false alarms (recurring cost)

− Cost of missed detec tions (recurring cost)

• Cost Avoidance

− Fines and Shutdown of Operations: Costs associated with fines for not being in compliance and the cost impact on operations and operational readin ess. (direct cost)

− Tank Replacement Cost Avoidance: Pre-mature replacement of tanks (direct cost)

− Remediation/Cleanup Cost Avoidance: Clean-up costs due to lack of testing or testing mistakes (direct cost)

• Commercialization and Technology Transfer Cost: Commercialization of the preproduction system (direct cost)

It is possible to make an estimate of all of th ese costs, because the performance of the leak detection system is known through th e third-party evaluation. The P D and P FA allow estimates of the cost of testing mistakes, remediation, and tank replacement to be made. The cost of regulatory compliance is described below; the costs associated with cost avoidance and commercialization and technology transfer is described in Section 6.3.

Regulatory compliance will include the costs associat ed with the purchase, installation, and use of a leak detection system. It is estimated that the DoD owns or operates approximately 300 bulk UST with capacities greater than 100,000 gal. Th e life-cycle cost of a leak detection technology is comprised of the elements in Table 23. The St artup costs are fixed costs associated with the purchase, installation, and operato r training. The Operational a nd Maintenance costs are also fixed and are small for the LRDP. The recurring costs associated with Compliance Testing and Test Mistakes are very small. Once the LRDP is permanently installed, a test can be initiated by pressing a start button.

In general, it is not the direct co sts that control the pr ice of a leak detectio n system. Rather, the recurring costs of monthly monitoring and annua l precision testing tend to control. For poor performing systems with a higher than desired P FA , the cost of testi ng increases, because

• additional tests with the same system or another system will have to be conducted to distinguish false alarms from leaks,

• site investigation may be required in terms of monito ring wells or uncovering of
buried tanks to determine whether or not the tank is actually leaking,59 • such false declarations may have to be repor ted to regulatory authorities with all the ramifications of such a report, and

• the activities required to determine whether or not a failed test is a false alarm will shutdown facility operations until the false alarm can be resolved.

If the P FA is unacceptably too high, operational experien ce indicates that fuel farm personnel often do not operate or trust the equipment, and thus, le aks may go undetected. This can be very costly
because of the remediation costs associated with undetected leaks.

Table 23. Compliance Monitoring Technology Co sts for the LRDP on a Per Tank Basis

Direct Environmental Costs Recurring or Variable Environmental Costs

Startup Operation &
Maintenance Compliance Testing Testing Mistakes

Equipment Cost $40,000 Equipment

Cost $40,000 Equipment

Cost $40,000 FA Mitigation

Remediation $40,000
$750,000

Activity % Activity % Activity % Activity %

Facility preparation,
mobilization $4,000

(10%) Labor to
operate equipment $4000

(10%) Monthly monitoring $400

(1%) False alarms

(P FA =< 0.1%) $40

(0.1%)

Equipment Design $4,000
(10%) Utilities $800
(2%) Annual precision

testing $400
(1%) Missed
detections* $938
(0.125%)

Equipment purchase $40,000
(100%) Consumable and supplies $400
(1%) Facility
shutdown costs for testing $1,200
(3%)

Installation $8,000
(20%) Equipment
maintenance $2,000
(5%)

Training of Operators $2,000
(5%) Training of
operators $800
(2%)

Total $58,000

(145%) Total $8,000

(20%) Total $2,000

(5%) Total $978

* It is assumed that the P D = 95% against a TLR = 0.2 gal/h and the number of leaking tanks is 10% of the 300 bulk USTs owned by the DoD. It is further assumed that all of the tanks are tested at a TLR of 0.2 gal/h, and as a consequence of testing at such a small leak rate, the remediation average remedi ation costs are assumed to be 25% of the average remediation costs.

Table 23 summarizes the costs associated with regulatory compliance with the LRDP. A Parts List for the LRDP is presented in Section 6.3. The purchase price of an LRDP assumed for this estimate is based on the purchase of 10 to 20 in-t ank sensor units. Table 23 presents the cost model in terms of a percentage (%) of the equipm ent purchase price. The costs of false alarms and missed detections are based on an assumed pr ice for additional testin g ($500) and an average remediation cost ($750,000 per incident). Th e average remediation cost is based on 890 remediation jobs performed by the Navy. These two co sts are indicated in the table heading. It is60 assumed that the P FA is less than 0.1%, and that the pr obability of a missed detection is P MD = 1-

P D = 5% for a target leak rate of 0.2 gal/h. It is further assumed for this computation that 10% of all of the bulk USTs owned by the military are leak ing. Because small leaks can be detected with the LRDP, the large average cost of remediation can be greatly reduced; fo r this calculation, it is
assumed that the cost of remedia tion is 25% of th e average cost.

An important cost is the cost of shutdown associated with testing and testing mistakes (false alarm investigations). Since the military is not selli ng fuel commercially, any short-term or permanent shutdown of fueling operations is difficult to quantify in term s of dollars. However, it is unacceptable to shutdown military operations, or to seriously impact operational readiness. An estimate of $40,000 for a False Alarm mitigation was used in Table 23, resulting in a $40 per tank

cost at a P FA of 0.1%. The total cost per tank is $ 69,000. A cost comparison of the LRDP and tracer and other mass-measurement systems is given in Section 6.2.

6.2 Cost Comparison to Conventional and Other Technologies

The LRDP has several significant cost advantages over other technologies. The cost advantages are realized because of the extremely high pe rformance of the LRDP, the on-line monitoring capability of the LRDP when perm anently installed in a tank, th e capability of the system to conduct a short test (an overnight test), and th e low maintenance and re curring costs associated with the system and the testing. The monthly monitoring and precision te sting requirements in California, for example, indicate that at least 12 and more likel y 13 tests need to be conducted each year just for regulatory compliance, and one of these tests must be conducted at 0.2 gal/h. Only a permanently installed system can cost -effectively address such regulatory monitoring requirements. A number of the in-tank mass-ba sed systems that are commercially available cannot be permanently installed in a tank and used for monitoring. The number of tests to be conducted each year will be increased (1) if the leak detection system is susceptible to false alarms, or (2) if tests need to be repeated, be cause they are too long a nd must be prematurely terminated or because they interfere w ith operations.

An estimate of the cost savings realized by th e LRDP over two other methodologies is shown in Tables 24 through 27. Method 1 represents a tr acer method with a high recurring cost of Compliance Testing. Method 1 assumes that a tracer must be added to the tank; no cost estimate is provided for tracer methods that use constitu ents in the fuel as tracers, because their performance has been found to be unacceptable. Method 2 is an in-tank mass-based method with the capability to only meet the monthly monitoring requirements. No other permanently installed in-tank, mass-based system besides the LRDP ha s the capability to meet the annual 0.2-gal/h performance standard. No specific commercial methods are identified by brand name here, but the cost savings achieved with the LRDP over a trac er method is due to the small recurring cost of testing with the LRDP and over th e other permanently installed in-t ank methods is due to the fact
that the LRDP can be used to meet the annual precision test as well as the monthly monitoring tests. The best way to interpret the tables is to examine the relative cost savings between the
LRDP and the other methods. The calculation us es the fixed Start-up costs and the recurring Compliance Testing costs from Table 23 for the LRDP.61 The cost comparison calculation is done as follows. First, it was assumed that the Startup and
O&M costs are the same for all methods. Establis hed price lists for bulk leak detection systems are not generally available, because most produc t sales or testing jobs are performed under a unique contract bid. In many instances, the purchase price of th e equipment or of the testing depends on the number of tanks that need to be tested. Therefore, it is difficult to make an estimate of the cost of other methods besides the LRDP. Historically, because the pr ice of leak detection equipment and testing with the equipment tends to be market driven rather than co st driven, it is safe to assume that the price of all

methods will be similar. This computation assumes $75,000, which is higher than anticipated for the LRDP and is probably lower than anticipated fo r Methods 1 and 2. This estimate includes the one-time purchase of the equipment for $40,000 (sam e as for the LRDP), as well as the operation and maintenance cost, the cost of testing a nd testing mistakes. The one-time purchase of equipment can be as high as $75,000 for mass-based sy stems. Second, the real cost savings of the testing tends to be controlled by the recurring cost of testing or the cost of additional testing because of lack of capability of the method to satisfy both the monthly monitoring and the annual precision test. The estimate assumes that 12 m onthly tests and one annua l precision at 0.2 gal/h are conducted each year. Third, ther e are significant cost savings a ssociated with cost avoidance and remediation/cleanup because accurate and reliab le leak detection is being performed. It is safe to say that the DoD would realize significant cost savings (many hundreds of millions of dollar) if any leak detection syst em was installed and used. If a reliable and accurate leak detection system is used, these savings can be a f actor of 2 to 5 greater. These latter cost savings
are not included in this calcul ation. Fourth, this cost compar ison does not include the costs of Testing Mistakes. The number of te sts to be conducted each year will be increased (1) if the leak detection system is susceptible to false alarms, or (2) if tests need to be repeated, because they are too long and must be prematurely terminated or because they interf ere with operations.

Table 24 summarizes the cost of the initial purchase and installation of the leak detection system, the cost of performing 12 monthly tests, and the cost of performing an annual precision test. It is assumed that Methods 1 and 2 have the capability for performing the monthly monitoring test, but only Method 1 also has the capabil ity for performing the annual test. It is assumed that Method 2 must use Method 1 to perform the annual precision te st. It is also assume d that the recurring cost of testing is high for Method 1 as compared to the LRDP and that the recurring cost of testing is
the same as the LRDP for Method 2. Table 25 summa rizes the total cost of meeting the regulatory

Table 24. Comparison of the Cost of Testing in Dollars ($) with Monthly Monitoring and an Annual Precision Test
for Each Bulk UST for the First Year

Purchase of System Monthly Monitoring Precision Test Total

Initial Purchase

for One UST Conduct of a Single

Test Cost of 12 Monthly

Tests Cost of Monthly Monitoring for

First Year Annual Cost of
Precision Test Cost of Compliance
for Year 1

Method 1 75,000 10,000 120,000 195,000 195,000

Method 2 75,000 240 2,880 77,880 25,000 102,880

LRDP 75,000 240 2,880 77,880 77,880
Method 1/LRDP 2.5
Method 2/LRDP 1.362 requirements for a single bulk UST for all three me thods. Clearly, the recu rring cost of Method 1 dominates the cost of testing. Table 26 summarizes the cost for a fuel farm containing 15 bulk USTs, and Table 27 summarizes the cost for all 300 tanks throughout the DoD complex.

The ratio of the cost of each method relative to th e LRDP are given in the tables. The savings of the LRDP compared to Method 1 w ould result in a payback period of less than one year, and the savings compared to Method 2 would result in a payback period of approximately three years, even without including the savings due to fewer tank replacements and lower remediation costs.

Table 22 summarizes the total cost of meeting the regulatory requirements for a single bulk UST for all three methods. Clearly, the recurring cost of Method 1 do minates the cost of testing.
Table 23 summarizes the cost for a fuel farm containing 15 bulk USTs, and Table 23 summarizes
the cost for 300 bulk USTs. When Methods 1 and 2 are compared to the LRDP, the cost of the other methods is a factor of 3 to 12 higher than the LRDP.

Table 25. Comparison of the Cost of Testing in Dollars ($) with Monthly Monitoring

and an Annual Precision Test for Each Bulk UST Over 1, 3, 5 and 10 Years

Testing Method Total Cost of Compliance for

First Year Three Years Five Years Ten Years

Method 1 195,000 435,000 675,000 1,275,000

Method 2 102,880 158,640 214,400 353,800

LRDP 77,880 83,640 89,400 103,800
Method 1/LRDP 2.5 5.2 7.6 12.3

Method 2/LRDP 1.3 1.9 2.4 3.4

Table 26. Comparison of the Cost of Testing in Dollars ($) with Monthly Monitoring

and an Annual Precision Test for 15 Bu lk USTs Over 1, 3, 5 and 10 Years

Testing Method Total Cost of Compliance for

First Year Three Years Five Years Ten Years

Method 1 2,925,000 6,525,000 10,125,000 19,125,000

Method 2 1,543,200 2,379,600 3,216,000 5,307,000

LRDP 1,168,200 1,254,600 1,341,000 1,557,000
Method 1/LRDP 2.5 5.2 7.6 12.3
Method 2/LRDP 1.3 1.9 2.4 3.4

Table 27. Comparison of the Cost of Testing in Dollars ($) with Monthly Monitoring

and an Annual Precision Test for 300 bulk USTs Over 1, 3, 5 and 10 Years

Testing Method Total Cost of Compliance for

First Year Three Years Five Years Ten Years

Method 1 58,500,000 130,500,000 202,500,000 382,500,000

Method 2 30,864,000 47,592,000 64,320,000 106,140,000

LRDP 23,364,000 25,092,000 26,820,000 31,140,000

Method 1/LRDP 2.5 5.2 7.6 12.3
Method 2/LRDP 1.3 1.9 2.4 3.4

6.3 Cost Avoidance63 The magnitude of the cost savings that can be realized by minimizing te sting mistakes, managing tank replacement efforts and minimizing remediati on/cleanup efforts through early detection of a release is a direct function of the use and perf ormance of the leak detection system. If the equipment is used frequently and the performance is high (i.e., the probabilities of false alarm and missed detection are low), then the integrity of th e tanks can be verified periodically and do not need to be routinely replaced. They can continue to be used with confidence that they are not leaking, and if a leak develops, th at it will be quickly detected. This reduces the volume of fuel released into the ground and the scope and cost of the clea nup. The high performance of the
LRDP means that the number of false alarms an d missed detections will be much smaller than other technologies. Furthermore, the high perfor mance of the LRDP allows the probability of false alarm of the system to be set to a very lo w level without sacrificing the detection of small leaks. The other mass-based systems and so me tracer-based appro aches do not have the performance to operate with a low probability of false alarm. In addition, other mass-based methods must operate at a higher ta rget leak rate. The total cost savings that can be realized by implementing a reliable leak detection program can be $500 million to $1 billion dollars. These cost savings are described below.

Fines and Shutdown of Operations. The cost of testing more than offsets the cost of the fines that may be levied if the tanks are not tested within the specifie d regulatory guidelines and are out of compliance. Fines may be $25,000 per day per f acility, or more. Ultimately, if the bulk USTs are not in compliance, fuel operations can be shut down. Since the military is not selling fuel, any permanent or short-term shutdown of fueling operations is difficult to quantif y in terms of dollars. However, it is unacceptable to shutdown military operations, or to seriously impact operational
readiness. Because the LRDP has the performance to perform both the monthly monitoring and the annual precision test, it is the most cost effective way to be in compliance. Because in many instances, an LRDP test can be performed in 10 h rather than the 48 or 72 h required by other methods, the impact on shutdown is significant.

Tank Replacement Cost Avoidance. Most bulk USTs are expensive to replace; the costs per tank can be tens of millions of dollars. Replacemen t costs can be minimized, avoided, or delayed by using accurate and reliable leak detection. Th ere are two types of tank replacement programs. First, the DoD has considered simply replacing a ll of the bulk USTs with bulk ASTs. The costs associated with such an approach would be well over $400,000,000. Such an approach can be
avoided or minimized. It assumes that there are no accurate or reliable methods of leak detection, which is not true. Second, the DoD will need to replace or retrofit tanks as required for safe storage. The use of accurate and reliable leak detection can justif iably and safely avoid premature replacement of tanks. The cost savings associated with the use of leak detection is very large. For example, the U. S. Army has estimated that it would cost over $10,00 0,000 just to replace the 50,000-gal USTs at the Hunter Army Airfield (without testing equi pment or testing services) as opposed to $3,100,000 for implementation of a tes ting program with the LRDP over a 10-year period. For our calculations, we assumed that the cost of replacement is $5 per gallon of stored
fuel. Remediation/Cleanup Cost Avoidance. The cost of remediation and cleanup are by the largest costs associated with leaking tanks and clean-up cost avoidance can be the most significant cost savings realized with the purchase, installation and use of reliable l eak detection. It is difficult to estimate the portion of the costs asso ciated with clean-up that can be avoided, but it is significant.64 The Navy has 659 future LUFT sites to clean up and has estimated that the total cost will be $890,000,000. Early detection of leaks can significantl y reduce the total cost of cleanup because
the concentration and areal extent of the plume is smaller than it would be if the leak was not detected early.

Commercialization and Technology Transfer. The costs associated w ith technology transfer and
commercialization have been minimized for the LRDP, because the third-party evaluation has already been completed and submitted to the NWGLDE for review and approval, and one company, Vista Research, has alr eady commercialized the pre-production system. The former is a significant barrier (both in cost and time) for entry into the ma rketplace, and the later can take many years for industry to commit the re sources needed for commercialization.

6.4 Cost of the Parts to Manufacture the LRDP

Table 28 summarizes the cost of th e parts to assemble an LRDP.

Table 28. Parts List for the LRDP

System Item Specification Vendor Price/ea Qty Total Price

In-Tank Differential Pressure Sensor Rosemount $1,568 1 $1,568 Pressure Sensors Pressure Sys. $680 2 $1,360
Indelas Electrical Actuator Flow Soln. $252 1 $252 RTD and Transmitter Omega $173 1 $173 Bellows (1) $86 1 $86 Bellows (2) $181 1 $181 SS Tubing (1) Peterson&Marsh $273 1 $273 SS Tubing (2) Peterson&Marsh $635 1 $635 Flanges, Ring, Cover Premier Tool $1,410 1 $1,410
Valve RS Crum $130 1 $130 Subtotal: $6,068

Above-Tank DM6430X PC104 DAQ -40 to 85 deg C RTD $845 1 $845 SKH486DX100 PC104 CPU Ext. Temp. RTD $1,296 1 $1,296 72Mbyte Disk-On-Chip (M-systems) Normal Temp. AtOnce $683 1 $683 Explosion Proof Box N/A Appleton $580 2 $1,160 24 Volt Power Supply (chg to 25V) -10 to 71 deg C Acopian $205 1 $205 ASTEC DC-DC (AA258024L0505) -25 to 70 deg C Bell Industries $83 1 $83 RTD and Transmitter Omega $173 1 $173 Voltage Reference (AD586) 0 to 70 deg C Newark $13 1 $13 Red LED (XP) Miller Wholesale $69 1 $69 Green LED (XP) Miller Wholesale $85 1 $85
XP Barrier R. Stahl $153 4 $612 Battery (Gell Cell) Newark $10 2 $21
Labor to Drill Holes in XP boxes Danco Machine $300 1 $300 Subtotal: $5,545

Misc. Electrical $644

Misc. Mechanical $2,692

Total Parts: $14,95165 

### 7.0 Regulatory Compliance

The DoD owns and/or operates almost all of the bulk USTs in the United States. While the leak detection requirements for bulk USTs (i.e., fiel d erected USTs) were deferred in EPA’s UST regulation issued on 22 September 1988, many of the st ates have or are in the process of requiring testing of such tanks. California is a major ex ample, but the bulk USTs in New York, Michigan, Maine, and Florida also require that these tanks be tested routinely for leaks. It is not surprising
that the members of the NWGLDE for bulk USTs are comprised of senior and active regulators from each of these states. The NFESC team has had major interactions, meetings, and
discussions with the members of the NWGLDE , both as work group representatives and as regulators. The process for obt aining approval of the LRDP-24 and the LRDP-48, based on the LRDP evaluated North Island, took over 18 months of frequent interactions. A number of important issues were derived from these interact ions. The NFESC team took a lead role in these discussions and was responsible for many of th e major regulatory changes that took place and allowed for DoD tanks to be in compliance.

A new evaluation protocol was deve loped for mass-based leak detection systems, because of real
differences between volumetric l eak detection systems and mass-ba sed leak detection systems. The NFESC team, in conjunction with KWA, took a lead role in developing and technically supporting these changes. The basic evaluation procedure comprised of conducting 12 blind tests did not change. Nor did the evaluation condition s change. What did change was how to report and apply the results of the evalua tion. The new evaluation procedure

• increased the range of tank si zes (diameters) for which the results of the evaluation would apply,

• acknowledged the concept that mass-measurem ent systems compensate for the thermal expansion and contraction of the fuel in the tank and the performance and

• acknowledged that the performance of ma ss-measurement systems scale with the surface area of the product in the tank and not the volume of the product in the tank,

• allowed the performance to scale with tank size (more specifically, the surface area of the product in the tank),

• limited the scaled perfor mance of the method to no less than 0.2 gal/h,

• allowed two or more tests to be averaged together to improve performance, and

• limited how the threshold used to declare a leak could be set.

The new evaluation procedure increased the ranged of USTs for which the evaluation was valid
from 150% of the surface area of the product in the tank to 250% of the product surface area of the tank. This had significant positive ramifica tions. This meant that if an evaluation was performed in a tank with a diameter of 88 ft or gr eater, the leak detection sy stem could be used to66 test all of the tanks owned and operated by DoD w ithout having to be reevaluated. Before this change, the same system would have had to be ev aluated a total of three times to cover the range of bulk USTs owned by DoD. Since the number of tanks is limited to 300, vendors would not
have found it cost effective to have the evalua tions conducted and a larg e number of DoD tanks would go untested and be out of regulatory comp liance. The NFESC team provided analysis and technical arguments to suppor t this increase to 250%.

The new evaluation procedure acknowledged that the volume of product in the tank does not
affect the result of a leak detection test with a mass-measurement system. Rather, the performance was affected by the surface area of the product in the tank. This was important, because, previously, the applicability of the evaluation was determined from the volume of product in the tank. This was also important, beca use, at the time, the NWGLDE was considering the option of scaling the performa nce of the evaluated method so th at it could be used to test smaller and larger tanks than th e one used in the eval uation. The NFESC team was the first group to make this argument with the regulators and pr ovided experiment evidence, theory, and analyses to support this premise.

The new evaluation procedure allowed the performa nce of the evaluated me thod to scale with the product surface area of the tank, provided that the ta rget leak rate of the scaled performance was not less than 0.2 gal/h. Thus, any tank that had a product surface area that resulted in a scaled target leak rate less than 0.2 gal/h would be tested at 0.2 gal/h. There was no upper bound on performance except that the larg est tank for which the evaluation was applicable was set at 250% of the product surface area of th e tank used in the evaluation. The NFESC team provided experiment evidence, theory, and analyses to support this performance scaling.

The new evaluation procedure acknowledged th at averaging test results would increase performance for methods whose results were rand om, additive, and independent, and accepted the approach for computing the performance without having to be reevaluated. The NFESC team played the primary role in advancing this me thodology. Its acceptance meant that a mass-based measurement system could be used for both mont hly monitoring and annual precision testing for high performing systems, even if the tank being te sted is too large for th e method to meet the 0.2- gal/h target leak rate crit erion in a single test.

The new evaluation procedure also established lim itations on how some of the methods could be used. For small USTs found at service stations, the threshold of the leak detection system was selected to operate with at the MDLR = 0.2 gal/h (i.e., P D = 95% for a TLR = 0.2 gal/h and a P FA = 5%), or with a threshold that was set so that the P D = 95% for a TLR = 0.2 gal/h and the P FA < 5%. The performance of the LR DP was deemed to be too good by the NWGLDE to operate in this latter manner, because the threshold that would be used to detect a leak rate of 2 gal/h with a

P D = 95% would be 1.9 gal/h. The regulators were afraid that sm aller leaks would go undetected using such a threshold and limited the target l eak rate to no larger than twice the MDLR. Practically, this prevented the LR DP from using the 3 gal/h monitoring standard in California, because its performance was too good, but allowed poor or marginal methods to use this standard. This NWGLDE-imposed usage limitation is unfort unate because it did not allow the LRDP to be operated as it was originally in tended. It is also the reason th at Versions 1.0, 1.1, and 1.2 exist. The performance of the LRDP is sufficiently good, however, that this regulatory limit does not67 impact its use. The NWGLDE also felt that the use of this approach fo r selecting a threshold would be confusing to tank owners because the PFA would change for every tank size tested (even though the P FA was always less than 5%). They agr eed that a threshold could be selected that was less than 5% provided that the target leak rate would scale with tank size. The NWGLDE developed a table to show examples of the performance of the method when testing
different size tanks. This table was added to the standard results fo rm of the third-party
evaluation.

In addition to the changes to the evaluation pr otocol, the NFESC team helped developed two
California leak detection standa rds for bulk USTs. In 1998, California developed a number of regulatory leak detection guideli nes for the owners and operators of bulk USTs. The original guidelines were based on the target leak rates (0.1 and 0.2 gal/h) being used for 10,000-gal USTs
at service stations. For monthl y monitoring purposes, California deve loped a target leak rate of 1 to 2 gal/h and 2 to 3 gal/h to accommodate the pe rformance of the one evaluated mass-based leak detection system, provided that a 0.1-gal/h precision (ti ghtness) test be conducted annually or biannually by another method. There were several problems with this approach. First, the guidelines do not acknowledge th e differences between the small USTs found at service stations and the large infrastructure USTs found at bulk fueling facilities. Second, the emphasis on the use of a target leak rate of 0.1- gal/h was misguided, because even at service stations, this standard is difficult to meet. The NFESC team proposed th at several guidelines be developed that replace the annual precision test at 0.1 gal/h with an annual precision test at 0.2 gal/h. This is significant, because a high performance mass-based leak detec tion system, like the LRDP, can be operated at 0.2-gal/h. The two guidelines presented in Table 1 (options 7 and 10) we re the result of the
interactions.

Finally, before the first evaluation was conducted, the NFESC team had seve ral meeting with the NWGLDE and the California regulators to inform th em of the evaluation pr ocedure and to insure that the procedure being followed was acceptabl e. The evaluation procedure and reporting procedure followed at Point Loma is identical to that approved by the NW GLDE and various state regulatory agencies for the first evaluation.

The NFESC team has worked closely with the NW GLDE and the state regul ators to insure that the DEM/VALs conducted to evaluate the performan ce of the LRDP would be acceptable. This interaction has also played a very significant role in the accepta nce of the LRDP, development of new ways to use bulk UST leak detection systems, development of better ways of evaluating and reporting the results of a third- party evaluation, and development of regulatory guidelines.68 

### 8.0 Technology Implementation

8.1 DoD Need

As stated in the introduction, the DoD owns and/or operates almost all of the bulk USTs in the United States. While the leak detection require ments for bulk USTs (i.e ., field erected USTs) were deferred in EPA’s UST regulation issued on 22 September 1988, many of the states have or are in the process of requiring te sting of such tanks. California has developed a set of regulatory guidelines for testing bulk USTs. Other states, like New York, Mi chigan, Maine, and Florida also require bulk USTs to be tested. The requirement for testing may cost many tens to hundreds of millions of dollars, depending on the testing approach used. The use of the LRDP, because of its ability to address the monthly m onitoring and the annual precision testing with the same system, can realize significant cost savings for the DoD.

8.2 Transition

The LRDP is ready for commercialization. The drawings, specifications, and software screens are described in Appendices C and D. A workshop was conducted by the Environmental Technology Evaluation Center (EvTEC) of the Ci vil Engineering Research Foundation (CERF) with representatives present from the petrol eum industry, the Defense Energy Support Center (DESC), the U. S. Air Force, Army, and Navy, and technical experts to introduce the technology and to describe the advantages of the system fo r regulatory compliance [27]. The LRDP was also
submitted for an R&D 100 award.

The LRDP already has regulatory approval, and the evaluation conducted as a DEM/VAL at Point Loma has been submitted for approval by the NWGLDE in April 2001. Since this submittal parallels the previous submittal, no significant te chnical acceptance problems are anticipated. As of this publication date, the thir d-party evaluation is still under review by the NWGLDE. If the LRDP is used to test 50,000-gal USTs or tanks with curved walls for regulatory compliance, another third-party evaluati on will have to be conducted.

Vista Research has commercialized the LRDP. Product description and specification sheets are included in Appendix C. Immediate commercializa tion of this technology has been possible, because industry was involved during the demonstra tions and the bulk storage tank facilities had a real need to be in regulatory compliance.69 

### 9.0 Lessons Learned

Generally, the demonstrations of the LRDP at the three sites went smoothly. It is important that the site selected for the dem onstration will be ade quate for demonstration
and validation and that the owners and/or operators of the site are interested in participating in and the outcome of the de monstration, because of the time and effort required to conduct a DEM/VAL. The LRDP teams received excellent support at all
three sites.

One problem was encountered during the de monstrations that is specific to the performance evaluations of in-tank leak dete ction systems. The third-party evaluation was originally scheduled to be conducted at the San Pedro Fuel Farm. The valves on the
bulk UST selected for the evaluation at the San Pedro fuel farm did not completely seal. This allowed a very small flow (~ 0.1 gal/h) to occur. Such flows are too small to interfere with monthly mon itoring tests that might be conducted on a tank, because the monitoring standards require that the threshold be set to detect the much larger leaks of 1 or 2 gal/h, and the performance of the LRDP is easily capable of detecting such leaks. However, this problem could have had signi ficant impact on the conduct of a precision
test in which the leak to be detected is of similar magnitude. For the conduct of the annual precision test, the valves might need to be sealed more tight ly or replaced with new valves, or valve blinds may need to be installed.

The EPA standard test procedures require that the tank used in the evaluation be free of
leaks and that no inflows or outflows occu r during the evaluation. Unfortunately, the LRDP is the only system that could identify such small flows. The problem was
identified and verified after a few tests dur ing the checkout of the LRDP at San Pedro, but the problem could not be corrected in a timely manner. As a consequence, the evaluation was performed on a bulk UST at th e Point Loma Fuel Terminal. New double block and bleed valve, which sealed tightly, had just been installed on the tanks in the
fuel farm.

It was important to conduct the evaluati on on a tight tank, because in the previous evaluation conducted at North Island, small in flows were present, but even though they were identified and quantified, the NWGLDE imposed unrealistic constraints on the use of the method in their listing [5]. Thes e constraints included requiring a much longer waiting period (24 h vice 2 h) and the suggest ion of a system bias (due to a non-zero mean) even though none existed. The former wa s due to a data qual ity index preventing the start of the test until in the inflow, wh ich took about 24 h to become small enough to be negligible, ceased. The latter had the potential for increasing the threshold, which would have result in declaring a leak wh en none was present during the conduct of an annual precision test at 0.2 gal/h.70 The magnitude of this valve problem is not known for bulk tanks, but it is the same problem encountered and successfully addr essed for routine monitoring of underground storage tanks at se rvice stations.

Unlike many other environmental technologies, the LRDP and the DEM/VAL procedure is not site specific or geology dependent. The EPA evaluation procedure is designed to accommodate a wide range of conditions that might be encountered during actual leak
detection tests at or other bulk fuel farms. The procedure places a constraint on the use of the equipment based on the conditions used in the evaluation. Thes e constraints involve temperature conditions and tank size. Fifteen years of expe rience indicates that once a
leak detection method is evalua ted following an EPA standard test procedure, it can be used to test any tank.71 

### 10.0 Summary

A reliable, flexible, easy-to-use, and cost -effective system for leak detection and inventory control has been demonstrated a nd validated for bulk USTs. The novel design of the LRDP allows off-the-shelf, commerc ially available process-control pressure sensors, which have a long-term demonstrated track record of performance, to be used. Delicate, expensive, one-of-a-kind, or special sensors are not required. The LRDP is a fully automatic, computer-controlled system th at can easily integrated with FAS or other fuel management systems. The LRDP has been evaluated for performance for bulk USTs with vertical walls following the standard test procedures developed by the EPA and approved by the National Work Group on Leak Detection Evaluations. The performance of the LRDP exceeds regulatory requirements for leak detection and is currently on the listing of the National Work Group for Leak De tection Evaluations. The results obtained on this ESTCP project have been submitted as an update to these results. Precision leak detection tests at 0.2-gal/h can be completed in 10 h for tanks with diameters less than 90 ft and in 24 h for larger tanks. Monthly monitoring tests at 1 or 2 gal/h can be accomplished with 10-h tests.

The DEM/VAL conducted in a 50,000-gal US T indicates that the LRDP has the performance to meet the 0.2-gal/h monthly monitoring requirements in EPA’s UST regulations. If the LRDP is used to test these USTs, then a thir d-party evaluation will
have to be conducted.

With some simple modifications, the LRDP should be able to test aboveground storage tanks for leaks with a performance that is si milar to that obtained for bulk USTs. These
modifications must address the effect of the large diurnal swin gs in ambient air temperature that occurs during a test.

The LRDP is ready for commercial use as a permanently installed system for monitoring, or a portable system for use in a testi ng service. Vista Research, Inc., has commercialized the system.72 

### 11.0 References

1. J. W. Maresca, Jr. and J. W. Starr. “The LRDP System fo r Detection of Leaks in Bulk Storage Tanks.” Final Report, prepared for the Naval Facilities Engineering Service Center, 110023 rd Avenue, Port Hueneme, CA 93043-4370, prepared by Vista Research, Inc., 100 View Street, Mo untain View, CA 94042, 25 March 1998.

2. W. Major, L. Karr, G. Warren, and J. Norbutas. “Red Hill Fuel Tank Leak Detection.” Proceedings of the Seventh (1997) Intern ational Offshore and Polar Engineering Conference, Honolulu, Hawaii, Naval Facil ities Engineering Service Center, Port Hueneme, California, 25-30 May 1997.

3. U.S. Environmental Protection Agency. “40 CFR 280 - Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage
Tanks.” Federal Register , Vol. 53, No. 185, 23 September 1988.

4. California Water Resources Control Board. “Local Guidance Letters LG 151-2.” 22
October 1999.

5. National Work Group on Evaluation of L eak Detection Methods. “List of Leak Detection Evaluations for Undergro und Storage Tank Systems.” Office of Underground Storage Tanks, U.S. En vironmental Protection Agency, 7 th Edition, April

2000.

6. U.S. Environmental Protection Agency. “Alte rnative Test Procedures for Evaluating
Leak Detection Methods: Evaluation of Bu lk Field Constructed Tanks.” Region VII, Memorandum, March 1996.

7. American Society of Testing Materials. “Standard Practice for Evaluating the Performance of Release Detection System s for Underground Storage Tank Systems (ASTM E 1526 - 93).” in Annual Book of ASTM Standards (Philadelphia: American Society of Testing a nd Materials, May 1993.

8. J. K. Wilcox. “Evaluation of the LRDP-10 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 4 December 2000.

9. J. K. Wilcox. “Evaluation of the LRDP-10 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Dr ive, Grain Valley, MO 64029, 4 December

2000.73 10. J. K. Wilcox. “Evaluation U pdate of the LRDP-24 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Repor t, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Dr ive, Grain Valley, MO 64029, 4 December

2000.

11. J. K. Wilcox. “Evaluation U pdate of the LRDP-24 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Fo rms, prepared for th e Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Dr ive, Grain Valley, MO 64029, 4 December

2000.

12. J. K. Wilcox. “Evaluation of the LRDP-10-n Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 4 December 2000.

13. J. K. Wilcox. “Evaluation of the LRDP-10-n Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Dr ive, Grain Valley, MO 64029, 4 December

2000.

14. J. K. Wilcox. “Evaluation Update of the LRDP-24-n on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Dr ive, Grain Valley, MO 64029, 4 December

2000.

15. J. K. Wilcox. “Evaluation Update of the LRDP-24-n on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluati on EPA Forms, prepared for the Naval Facilities Engineering Service Center a nd Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ri dge Drive, Grain Valley, MO 64029, 4
December 2000.

16. L. A. Karr, W. R. Major, J. W. Maresca, Jr., M. J. Talhami, J. W. Starr, and R. F.
Wise. “Pre-Production Initiative: Low Ra nge Differential Pressure (LRDP) Leak Detection System - Red Hill Test Results.” Final Report. Naval Facilities Engineering Service Center, 1100 23 rd Avenue, Port Hueneme, California 93043-4370 and Vista Engineering Technologies, L.L.C., 8203 W. Quinault, Kennewick, Washington 99336, 31 July 2001.

17. J. W. Maresca, Jr., “System and Method for Leak Detection in Liquid Storage Tanks.” U. S. Patent No. 4,646,560, Vista Research, In c., Palo Alto, Calif ornia, 3 March 1987.74 18. W. R. Major, L. A. Karr, G. A. Hayter , and J. W. Maresca, Jr. “ESTCP Technology
Demonstration Plan: Validation of the Low Range Differential Pressure (LRDP) Leak Detection System for Small Leaks in Bulk Fuel Tanks.” Naval Facilities Engineering Service Center, Port Hueneme, California, 18 July 1988.

19. J. K. Wilcox. “Evaluation of the LRDP-24 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 29 January 1998.

20. J. K. Wilcox. “Evaluation of the LRDP-24 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Driv e, Grain Valley, MO 64029, 29 January 1998.

21. J. K. Wilcox. “Evaluation of the LRDP-48 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 29 January 1998.

22. J. K. Wilcox. “Evaluation of the LRDP-48 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Driv e, Grain Valley, MO 64029,29 January 1998.

23. J. K. Wilcox. “Evaluation of the LRDP-24-5 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 29 January 1998.

24. J. K. Wilcox. “Evaluation of the LRDP-24-5 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Driv e, Grain Valley, MO 64029, 29 January 1998.

25. J. K. Wilcox. “Evaluation of the LRDP-48-4 on Bulk Field-Constructed Tanks: Final Report.” Third-Party Evaluation Report, prep ared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Drive, Grain Valley, MO 64029, 29 January 1998.

26. J. K. Wilcox. “Evaluation of the LRDP-48-4 on Bulk Field-Constructed Tanks: EPA Forms.” Third-Party Evaluation EPA Form s, prepared for the Naval Facilities Engineering Service Center and Vista Research, Inc., prepared by Ken Wilcox Associates, Inc., 1125 Valley Ridge Driv e, Grain Valley, MO 64029, 29 January 1998.

27. Environmental Technology Evaluation Cent er (EvTEC). “Low Range Differential Pressure (LRDP) Leak Detection Syst em Workshop Report.” Workshop Report.75 Environmental Technology Evalua tion Center (EvTEC), 1015 15 th Street, Suite 600, Washington D.C. 20005-2605, June 2000.A-1 

### Appendix A

Points of Contact

Point of Contact Organization Ph one/Fax/Email Role in Project Leslie A. Karr, REM Program Manager Naval Facilities Engineering Service Center (NFESC)
1100 23 rd Avenue Port Hueneme, CA 93043-4370 voice: (805) 982-1618 fax: (805) 982-4304 e-mail: karrla@nfesc.navy.mil Project Manager

William R. Major Project Engineer Naval Facilities Engineering Service Center (NFESC)
1100 23 rd Avenue Port Hueneme, CA 93043-4370 voice: (805) 982-1808 fax: (805) 982-4304 e-mail: majorwr@nfesc.navy.mil Project Engineer

Dr. Vincent F. Hock Program Manager U. S. Army Corps of Engineers Construction Engineering Research Laboratory (CERL)
2902 Nemark Drive Champaign, Illinois 61826 Voice: (217)373-6753 fax: (217)373-6732 e-mail: v-hock@cecer.army.mil Project Engineer

Dr. Joseph W. Maresca, Jr.
Vice President Vista Research, Inc. 755 North Mary Avenue Sunnyvale, California 94086 voice: (408) 830-3306 fax: (408) 830-3399 e-mail: maresca@vrinc.com Technical Director, Industry

Partner
James W. Starr, P. E. Staff Engineer Vista Research, Inc.
139 Glendale Avenue Edison, New Jersey 08817 Voice: (732) 777-2100 Fax: (732) 777-9495 e-mail: jstarr@vrinc.com Project Engineer

Gary A. Hayter Sr. Research Engr Vista Research, Inc. 755 North Mary Avenue Sunnyvale, California 94086 voice: (408) 830-3300; fax: (408) 830-3399 e-mail: ghayter@vrinc.com Project Engineer

Dr. H. Kendall Wilcox
President Ken Wilcox Associates, Inc. 1125 Valley Ridge Drive Grain Valley, MO 64029, USA voice: (816) 443-2494 fax: (816) 443-2495 e-mail: kwilcox@kwaleak.com Third-Party
Evaluator

Col Patrick L. Fink
U. S. Air Force Randolph Air Force Base San Antonio, TX voice: (210) 652-6375 DEM/VAL
Liaison

George E. Cook, III Director, Fuel Farm Supply Department Code 199, Building 426
NAS North Island
P. O. Box 357039 San Diego, CA 92135-7039 Voice: (619) 545-8841 fax: (619) 545-8841 DEM/VAL
Liaison

Clarence Wilson Director, Fuel Farm Defense Energy Office, Los Angeles 3171 North Gaffey Street San Pedro, CA 90731-1099 voice: (310) 335-3090 ext. 404 fax: (310) 335- DEM/VAL
Liaison

LCDR R. C. Griffin, SC,

USN
Point Loma Site Director FISC San Diego
Point Loma Fuel Terminal 937 N. Harbor Drive, STE 480 San Diego, CA 92132-0480 voice: (619) 553-1312 fax: (619) 553-4877
e-mail: Rowdy_Griffin@sd.fisc.navy.mil DEM/VAL
Liaison

Stephen L. Frey
Fuels Terminal Director FISC San Diego
Point Loma Fuel Terminal 937 N. Harbor Drive, STE 480,
Code 701 San Diego, CA 92132-0480 voice: (619) 553-1314 fax: (619) 553-4877
e-mail: Stephen_L_Frey@sd.fisc.navy.mil DEM/VAL
Liaison

Dale Kiefer
Environmental Division
Head Hunter Army Airfield Ft Stewart, GA 31314 voice: 912-767-2010 DEM/VAL
Liaison

Terry Nierenhausen Hunter Army Air Field 98 South Middleground Road, Building 1216 Savannah, GA 31409 voice: (912) 352-5535 DEM/VAL
LiaisonA-2 William Middleton Defense Energy Office – Los Angeles Defense Energy Supply Center (DESC) John J. Kingman Road, Suite 4950 Fort Belvoir, VA22060-6222 voice: (702) 767-8313 fax: (703) 767-8331 e-mail: wmiddleton@desc.dla.mil DEM/VAL
Liaison

Brian Rustia EvTEC

1015 15 th Street, NW, Suite 600 Washington D.C. 20005-2605 voice: (202) 842-0555 fax: (202) 842-2605 CERF Workshop

Heather Warkentien EvTEC

1015 15 th Street, NW, Suite 600 Washington D.C. 20005-2605 voice: (202) 842-0555 fax: (202) 842-2605 CERF Workshop

Russ Brauksieck
New York DEC New York State Department of
Environmental Conservation 50 Wolf Road, Room 360 Albany, NY 12233-3750 voice: (518) 457-4351 fax: (518) 457-4332
e-mail: rxbrauks@gw.dec.state.ny.us NWGLDE,
Chairman Bulk USTs,
New York Regulator
Beth DeHaas
Maine DEP Maine Department of
Environmental Protection
Statehouse Station No. 17 Augusta, ME 04333 voice: (207) 287-2651 fax: (207) 287-7826 e-mail: beth.dehaas@state.me.us NWGLDE, Bulk USTs, Maine Regulator

Shahla Farahnak
California SWRCB California State Water Resource
Board Division of Clean Water Program

P. O. Box 944212 Sacramento, CA 94244-2120 voice: (916) 227-4320 fax: (916) 227-4349
e-mail: farahnas@gwgate.swrcb.epa.gov NWGLDE, Bulk USTs,
California Regulator

John Reeder
Florida DEP Florida Department of
Environmental Protection
3804 Coconut Palm Drive Tampa, FL 33619-8318 voice: (813) 744-6100 ext. 472 fax: (813) 744-6125 e-mail: jon.reeder@dep.state.fl.us NWGLDE, Florida Regulator

John Kneece
South Carolina DHEC South Carolina Department of
Health and Environmental Control
2600 Bull Street Columbia, SC 29201 voice: (803) 898-4364 fax: (803) 898-4330
e-mail: kneeceje@colum26.dhec.state.sc.us NWGLDE, South Carolina Regulator

Curt D. Johnson
Alabama DEM Alabama Department of Environmental Management

P. O. Box 301463 Montgomery, AL 36130-1463 voice: (334) 271-7986 fax: (334) 270-5631 e-mail: cdj@adem.state.al.us NWGLDE, Chairman,
Alabama Regulator

### Appendix B

Listings for the LRDP-10 and the Update for the LRDP-24

Submitted to the National Work Group on Leak Detection Evaluations (NWGLDE)B-2 Revision Date: December 4, 2000 Vista Research, Inc. and Naval Fac ilities Engineering Service Center

LRDP-24 (V1.0a.1.65,V1.0a.2.40)

BULK FIELD-CONSTRUCTED AUTOMATIC TANK GAUGE MONITORING
AND TIGHTNESS TEST LEAK DETECTION METHOD

Certification: Leak rate is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak rate is 1.65 or 2.40 gph with P D = 95% and P FA = 0.0015% or P FA < 0.001%, respectively. Choose one to determine the scaled leak rate and scaled leak threshold for the tank being monitored. For other tank sizes, scaled leak rate equals [(PSA in ft2 ÷ 11,786 ft2) x (leak rate in gph)]. Example: For a tank with PSA = 10,000 ft2, leak ra te = 1.65 gph; scaled leak rate = [(10,000 ft2 ÷ 11,786 ft2) x 1.65 gph] = 1.40 gph.
Calculated minimum detectable leak rate is 0.690 gph with P D = 95% and P FA = 5%. Leak rate may not be scaled below 0.2 gph.

Leak Threshold: Leak threshold is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2 and leak rate of 1.65 or 2.40 gph, leak threshold is 1.31 or 2.06 gph respectively. For other tank sizes, scaled leak threshold equals [( PSA in ft2 ÷ 11,786 ft2) x (leak rate in gph - 0.345 gph)]. Example: For a tank with PSA = 10,000 ft2, leak ra te = 1.65 gph; scaled leak threshold = [(10,000 ft2 ÷ 11,786 ft2) x (1.65 gph - 0.345 gph)] = 1.40 gph. A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds the
calculated leak threshold.

Applicability: Gasoline, diesel, aviation fuel. Other liquids may be tested after consultation with the manufacturer.

Tank Capacity: Use limited to single field-constructed ve rtical tanks larger than 50,000 gallons. Maximum product surface area (PSA) is 29, 465 ft2 (approximately 193.7 ft. diameter). Performance not sensitive to product level.

Waiting Time: Minimum of 2 hours after delivery or dispensing. Valve leaks and pump drain-back may mask a leak. Allow sufficient waiting time to minimize these effects. Waiting times during evaluation ranged from 0 to 3 hours.

Test Period: Minimum of 24 hours. There must be no dispensing or delivery during test.

Temperature: Measurement not required by this system.

Water Sensor: None. Water leaks are measured as increase in mass inside tank.

Calibration: Differential pressure sensor must be checked regul arly in accordance with ma nufacturer's instructions.

Comments: Tests only portion of tank containing product. As product level is lowered, leak rate in a leaking ta nk decreases (due to lower he ad pressure). Consistent testing at low levels could allo w a leak to remain undetected. Evaluated in a nominal 2,100,000 gallon, vertical underground tank w ith product surface area (PSA) of 11,786 ft2. Evaluated as a stand-alone system. Performance of the system can be improved by combining re sults of 2 or more tests. If this option is used, it is important to determine the number of tests, thei r timing and the number of passing results necessary to confirm a tank is tight. The LRDP-24-n (V1.0a, V1.1a, V1.2a) combines the results of n tests, where n < 12 and is one evaluated option to improve the performance of this system.

Vista Research, Inc. Evaluato r: Ken Wilcox Associates 100 View St. Tel: (816) 443-2494 Mountain View, CA 94042 Date of Evaluation: 01/29/99 Tel: (650) 966-1171B-3 Revision Date: December 4, 2000 Vista Research, Inc. and Naval Fac ilities Engineering Service Center

LRDP-10 (V1.0a.1.90,V1.0a.2.40)

BULK FIELD-CONSTRUCTED AUTOMATIC TANK GAUGE MONITORING
AND TIGHTNESS TEST LEAK DETECTION METHOD

Certification: Leak rate is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak rate is 1.90 or 2.40 gph with P D = 95% and P FA = 0.075% or 0.006%, respectively. Choose one to determine the scaled leak rate and scaled leak threshold for the tank being
monitored. For other tank sizes, scaled leak rate equals [(PSA in ft2 ÷ 11,786 ft2) x (leak rate in gph)]. Example: For a tank with PSA = 10,000 ft2, leak ra te = 1.90 gph; scaled leak rate = [(10,000 ft2 ÷ 11,786 ft2) x 1.90 gph] = 1.61 gph.
Calculated minimum detectable leak rate is 1.14 gph with P D = 95% and P FA = 5%. Leak rate may not be scaled below 0.2 gph.

Leak Threshold: Leak threshold is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2 and leak rate of 1.90 or 2.40 gph, leak threshold is 1.33 or 1.83 gph respectively. For other tank sizes, scaled leak threshold equals [( PSA in ft2 ÷ 11,786 ft2) x (leak rate in gph - 0.569 gph)]. Example: For a tank with PSA = 10,000 ft2, leak ra te = 1.90 gph; scaled leak threshold = [(10,000 ft2 ÷ 11,786 ft2) x (1.90 gph - 0.569 gph)] = 1.13 gph. A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds the
calculated leak threshold.

Applicability: Gasoline, diesel, aviation fuel. Other liquids may be tested after consultation with the manufacturer.

Tank Capacity: Use limited to single field-constructed ve rtical tanks larger than 50,000 gallons. Maximum product surface area (PSA) is 29, 465 ft2 (approximately 193.7 ft. diameter). Performance not sensitive to product level.

Waiting Time: Minimum of 2 hours after delivery or dispensing. Valve leaks and pump drain-back may mask a leak. Allow sufficient waiting time to minimize these effects. Waiting times during evaluation ranged from 0 to 3 hours, with one at 7 hours and another at 10 hours.

Test Period: Minimum of 10 hours. There must be no dispensing or delivery during test.

Temperature: Measurement not required by this system.

Water Sensor: None. Water leaks are measured as increase in mass inside tank.

Calibration: Differential pressure sensor must be checked regul arly in accordance with ma nufacturer's instructions.

Comments: Tests only portion of tank containing product. As product level is lowered, leak rate in a leaking ta nk decreases (due to lower he ad pressure). Consistent testing at low levels could allo w a leak to remain undetected. Evaluated in a nominal 2,100,000 gallon, vertical underground tank w ith product surface area (PSA) of 11,786 ft2. Evaluated as a stand-alone system. Performance of the system can be improved by combining re sults of 2 or more tests. If this option is used, it is important to determine the number of tests, thei r timing and the number of passing results necessary to confirm a tank is tight. The LRDP-10-n (V1.0a, V1.1a, V1.2a) combines the results of n tests, where n < 12 and is one evaluated option to improve the performance of this system.

Vista Research, Inc. Evaluato r: Ken Wilcox Associates 755 North Mary Avenue Tel: (816) 443-2494 Sunnyvale, CA 94085 Date of Evaluation: 06/07/00 Tel: (408) 830-3300B-4 Revision Date: December 4, 2000 Vista Research, Inc. and Naval Fac ilities Engineering Service Center

LRDP-24 (V1.1a)

BULK FIELD-CONSTRUCTED AUTOMATIC TANK GAUGE MONITORING
AND TIGHTNESS TEST LEAK DETECTION METHOD

Certification: Leak rate is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak rate is 0.95 gph with P D = 95% and P FA =0.48%. For other tank sizes, leak rate equals [(PSA in ft2 ÷ 11,786 ft2) x 0.95 gph]. Example: For a tank with PSA = 10,000 ft2; leak rate = [(10,000 ft2 ÷ 11,786 ft2) x 0.95 gph] = 0.81 gph.
Calculated minimum detectable leak rate is 0.690 gph with P D = 95% and P FA = 5%. Leak rate may not be scaled below 0.2 gph.

Leak Threshold: Leak threshold is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak threshold is 0.60 gph. For other tank sizes, leak threshold equa ls [(PSA in ft2 ÷ 11,786 ft2) x 0.60 gph]. Example: For a tank with PSA = 10,000 ft2; leak th reshold = [(10,000 ft2 ÷ 11,786 ft2) x 0.60 gph] = 0.51 gph. A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds the
calculated leak threshold.

Applicability: Gasoline, diesel, aviation fuel. Other liquids may be tested after consultation with the manufacturer.

Tank Capacity: Use limited to single field-constructed ve rtical tanks larger than 50,000 gallons. Maximum product surface area (PSA) is 29, 465 ft2 (approximately 193.7 ft. diameter). Performance not sensitive to product level.

Waiting Time: Minimum of 2 hours after delivery or dispensing. Valve leaks and pump drain-back may mask a leak. Allow sufficient waiting time to minimize these effects. Waiting times during evaluation ranged from 0 to 3 hours.

Test Period: Minimum of 24 hours. There must be no dispensing or delivery during test.

Temperature: Measurement not required by this system.

Water Sensor: None. Water leaks are measured as increase in mass inside tank.

Calibration: Differential pressure sensor must be checked regul arly in accordance with ma nufacturer's instructions.

Comments: Tests only portion of tank containing product. As product level is lowered, leak rate in a leaking ta nk decreases (due to lower he ad pressure). Consistent testing at low levels could allo w a leak to remain undetected. Evaluated in a nominal 2,100,000 gallon, vertical underground tank w ith product surface area (PSA) of 11,786 ft2. Evaluated as a stand-alone system. Performance of the system can be improved by combining resu lts of 2 or more tests. If this option is used, it is important to determine the number of tests, their timing and the number of passing results necessary to confirm a tank is tight. The LRDP-24-n (V1.0a, V1.1a, V1.2a) combines the results of n tests, where n < 12 and is one evaluated option to improve the performance of this system.

Vista Research, Inc. Evaluato r: Ken Wilcox Associates 755 North Mary Avenue Tel: (816) 443-2494 Sunnyvale, CA 94085 Date of Evaluation: 06/07/00 Tel: (408) 830-3300B-5 Revision Date: December 4, 2000 Vista Research, Inc. and Naval Fac ilities Engineering Service Center

LRDP-10 (V1.1a)

BULK FIELD-CONSTRUCTED AUTOMATIC TANK GAUGE MONITORING
AND TIGHTNESS TEST LEAK DETECTION METHOD

Certification: Leak rate is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak rate is 1.65 gph with P D = 95% and P FA =0.29%. For other tank sizes, leak rate equals [(PSA in ft2 ÷ 11,786 ft2) x 1.65 gph]. Example: For a tank with PSA = 10,000 ft2; leak rate = [(10,000 ft2 ÷ 11,786 ft2) x 1.65 gph] = 1.40 gph.
Calculated minimum detectable leak rate is 0.690 gph with P D = 95% and P FA = 5%. Leak rate may not be scaled below 0.2 gph.

Leak Threshold: Leak threshold is proportional to product surface area (PSA). For tanks with PSA of 11,786 ft2, leak threshold is 1.08 gph. For other tank sizes, leak threshold equa ls [(PSA in ft2 ÷ 11,786 ft2) x 1.08 gph]. Example: For a tank with PSA = 10,000 ft2; leak th reshold = [(10,000 ft2 ÷ 11,786 ft2) x 1.08 gph] = 0.92 gph. A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds the
calculated leak threshold.

Applicability: Gasoline, diesel, aviation fuel. Other liquids may be tested after consultation with the manufacturer.

Tank Capacity: Use limited to single field-constructed ve rtical tanks larger than 50,000 gallons. Maximum product surface area (PSA) is 29, 465 ft2 (approximately 193.7 ft. diameter). Performance not sensitive to product level.

Waiting Time: Minimum of 2 hours after delivery or dispensing. Valve leaks and pump drain-back may mask a leak. Allow sufficient waiting time to minimize these effects. Waiting times during evaluation ranged from 0 to 3 hours, with one at 7 hours and another at 10 hours.

Test Period: Minimum of 10 hours. There must be no dispensing or delivery during test.

Temperature: Measurement not required by this system.

Water Sensor: None. Water leaks are measured as increase in mass inside tank.

Calibration: Differential pressure sensor must be checked regul arly in accordance with ma nufacturer's instructions.

Comments: Tests only portion of tank containing product. As product level is lowered, leak rate in a leaking ta nk decreases (due to lower he ad pressure). Consistent testing at low levels could allo w a leak to remain undetected. Evaluated in a nominal 2,100,000 gallon, vertical underground tank w ith product surface area (PSA) of 11,786 ft2. Evaluated as a stand-alone system. Performance of the system can be improved by combining resu lts of 2 or more tests. If this option is used, it is important to determine the number of tests, their timing and the number of passing results necessary to confirm a tank is tight. The LRDP-10-n (V1.0a, V1.1a, V1.2a) combines the results of n tests, where n < 12 and is one evaluated option to improve the performance of this system.

Vista Research, Inc. Evaluato r: Ken Wilcox Associates 755 North Mary Avenue Tel: (816) 443-2494 Sunnyvale, CA 94085 Date of Evaluation: 06/07/00 Tel: (408) 830-3300

### Appendix C

Product Description and Product Specification SheetsVISTA RESEARCH, INC.  755 North Mary Avenue  Sunnyvale, CA 94085  (408) 830-3300 Dimensions Diameter of Base Sensor Cylinder Height of Base Sensor Cylinder

Diameter of reference tube Height of constant diameter reference tube Height of shaped reference tube

Embedded controller (2 connected units) 7 13/16 in. (19.9 cm) 16.0 in. (45.7 cm)

3 1⁄2 in. (8.9 cm) 0 to 50 ft (15.2 m) 0-12 ft (3.7 m); 0-50 ft (15.2 m)

12 in. x 12 in. x 8 in. (ea. unit) (30.5 cm x 45.7 cm x 10.2 cm)

Weight Base Sensor Cylinder (Empty)

Constant diameter reference tube, including conduit Shaped reference tube, including conduit

Embedded controller (2 units) 35 lbs (16 kg)

5 lbs/ft (2.3 kg) 5 lbs/ft (2.3 kg)

60 lbs (27.3 kg)

Detectable Leak Rate
(Probability of detection of 95% with a probability of false alarm of 5%) For tank diameters less than 51.3 ft For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [2,635.0*(n) 0.5 ] 0.5 (LRDP-10-n) 0.20 gal/h (3.14*(D*0.5) 2 /11,786)*1.139 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of 95% with a probability of false alarm of 0.29%) For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [1,817.3*(n) 0.5 ] 0.5 (LRDP-10-n) (3.14*(D*0.5) 2 /11,786)*1.653 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of 95% with a probability of false alarm of <0.15%) For tank diameters (D in ft) up to 193.4 ft For tank diameters (D in ft) up to 193.4 ft (3.14*(D*0.5) 2 /11,786)*(2.0-0.569) gal/h (3.14*(D*0.5) 2 /11,786)*(3.0-0.569) gal/h

Power In-tank sensor unit, embedded controller, interface computer Single-phase 120 VAC 60 Hz

Temperature Operating -20 o to 100 o F (-29 o to 38 o C)

User Interface System monitor Vista GUI software
Windows 95 or FAS software 

# LRDP-10

Low Range Differential Pressure System 

## Product Data Sheet and System SpecificationVISTA RESEARCH, INC.  755 North Mary Avenue  Sunnyvale, CA 94085  (408) 830-3300 Dimensions Diameter of Base Sensor Cylinder Height of Base Sensor Cylinder

Diameter of reference tube Height of constant diameter reference tube Height of shaped reference tube

Embedded controller (2 connected units) 7 13/16 in. (19.9 cm) 16.0 in. (45.7 cm)

3 1⁄2 in. (8.9 cm) 0 to 50 ft (15.2 m) 0-12 ft (3.7 m); 0-50 ft (15.2 m)

12 in. x 12 in. x 8 in. (ea. unit) (30.5 cm x 45.7 cm x 10.2 cm)

Weight Base Sensor Cylinder (Empty)

Constant diameter reference tube, including conduit Shaped reference tube, including conduit

Embedded controller (2 units) 35 lbs (16 kg)

5 lbs/ft (2.3 kg) 5 lbs/ft (2.3 kg)

60 lbs (27.3 kg)

Detectable Leak Rate
(Probability of detection of 95% with a probability of false alarm of 5%) For tank diameters less than 66.0 ft For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [4,349.7*(n) 0.5 ] 0.5 (LRDP-24-n) 0.20 gal/h (3.14*(D*0.5) 2 /11,786)*0.69 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of 95% with a probability of false alarm of 0.48%) For tank diameters (D in ft) up to 193.7 ft For tank diameters D = [3,172.4*(n) 0.5 ] 0.5 (LRDP-24-n) (3.14*(D*0.5) 2 /11,786)*0.946 gal/h

0.20 gal/h (average of 1 < n < 12 tests)

(Probability of detection of 95% with a probability of false alarm of <0.003%) For tank diameters (D in ft) up to 193.4 ft For tank diameters (D in ft) up to 193.4 ft (3.14*(D*0.5) 2 /11,786)*(2.0-0.345) gal/h (3.14*(D*0.5) 2 /11,786)*(3.0-0.345) gal/h

Power In-tank sensor unit, embedded controller, interface computer Single-phase 120 VAC 60 Hz

Temperature Operating -20 o to 100 o F (-29 o to 38 o C)

User Interface System monitor Vista GUI software
Windows 95 or FAS software 

# LRDP-24

Low Range Differential Pressure System 

## Product Data Sheet and System Specification

### Appendix D

Software User Interface ScreensD-2 Figure D-1. LRDP Main Menu: display screen allowing the user to conduct a leak detection test or to review the results of previous leak detection tests

Figure D-2. Enter New Test Parameters: display screen allowing the user to use the default testing option and test parameters shown on the screen or to enter new test parameters.D-3 Figure D-3. T est Initiation: display screen allowing the user to start the test immediately or to
schedule the start of the test for a later time.

Figure D-4. Leak Detection Test Preparation: display screen reminding the user that valves need to be
closed before a test can be conducted.D-4 Figure D-5. Leak Detection Test Setup/Monitor Screen: display screen allowing the user to monitor the level

in real time

.

Figure D-6. LRDP Test Results: display screen presenting the results of the leak detection to the user.D-5 Figure D-7. Leak Detection Test Archives: display screen allowing the user to review previous test results

and test data

.

### Appendix E

Performance Equations for Version a of the LRDP-10, LRDP-24, LRDP-10-n and LRDP-24-nE-2 Operation of the Evaluated System

Version a Mass Based Systems (with scaling included)

Test Threshold * , ** Set PD = 95% against a Target Leak Rate > MDL
to insure PFA < 5% Target Leak Rate, TLR – gal/h TLR > [MDL (A 2 /A 1 )] > 0.2
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2 Threshold,

C – gal/h [TLR - C MDL (A 2 /A 1 )] > 0.1 or 0.1 for [TLR - C MDL (A 2 /A 1 )] < 0.1

PD – % 95%

PFA - % < 5% *There may be more than one threshold specification for system operation; TLR = target leak rate.
**Define MDL and C MDL = MDL/2 for A 1 ; S for A 1 ; and A 1

Operation of the Evaluated System

Version a Mass Based Systems (with scal ing and averaging included)

Test Threshold * , ** Set PD = 95% against a Target Leak Rate > MDL
To insure PFA < 5% Target Leak Rate, TLR – gal/h [(MDL/n 0.5 ) (A 2 /A 1 )] = 0.2
such that 1 < n < 12
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2 Threshold,

C – gal/h [TLR-(C MDL /n 0.5 ) (A 2 /A 1 )] > 0.1
such that 1 < n < 12
or 0.1 for [TLR- (C MDL /n 0.5 ) (A 2 /A 1 )] < 0.1

PD – % 95%

PFA - % < 5% *There may be more than one threshold specification for system operation; TLR = target leak rate.

**Define MDL and C MDL = MDL/2 for A 1 ; S for A 1 ; and A 1 ; 1 < n < 12E-3 LRDP-24 Version a

Test Threshold 1* , ** Set PD = 95% against a Target Leak Rate > MDL to insure PFA < 5%

Target Leak Rate, TLR – gal/h [0.69 (A 2 /11,786)] > 0.2
or 0.2 for [0.69 (A 2 /11,786)] < 0.2

Threshold,

C – gal/h [TLR – (0.345) (A 2 /11,786)] > 0.1
or 0.1 for [TLR – (0.345) (A 2 /A 1 )] < 0.1

PD – % 95%

PFA - % < 5%

*There may be more than one threshold specification for system operation; TLR = target leak rate. **MDL = 0.69 gal/h; S = 0.192 gal/h; and A 1 = 11,786 ft 2

.

LRDP-24-n Version a

Test Threshold 1* , ** Set PD = 95% against a Target Leak Rate > MDL to insure PFA < 5%

Target Leak Rate, TLR – gal/h [(0.69/n 0.5 ) (A 2 /11,786] = 0.2
such that 1 < n < 12

or 0.2 for [(0.69/n 0.5 ) (A 2 /11,786)] < 0.2

Threshold,

C – gal/h [TLR-((0.345)/n 0.5 ) (A 2 /11,786] > 0.1
such that 1 < n < 12
and 0.1 for [TLR-((0.345)/n 0.5 ) (A 2 /11,786] < 0.1

PD – % 95%

PFA - % < 5%

*There may be more than one threshold specification for system operation; TLR = target leak rate. **MDL = 0.69 gal/h; S = 0.192 gal/h; and A 1 = 11,786 ft 2 ; 1 < n < 12.E-4 LRDP-10 Version a

Test Threshold 1* , ** Set PD = 95% against a Target Leak Rate > MDL to insure PFA < 5%

Target Leak Rate, TLR – gal/h [(1.139) (A 2 /11,786)] > 0.2
or 0.2 for [(1.139) (A 2 /11,786)] < 0.2

Threshold,

C – gal/h [TLR – (0.569) (A 2 /11,786)] > 0.1
or 0.1 for [TLR – (0.569) (A 2 /11,786)] < 0.1

PD – % 95%

PFA - % < 5%

*There may be more than one threshold specification for system operation; TLR = target leak rate. **MDL = 1.14 gal/h; S = 0.317 gal/h; and A 1 = 11,786 ft 2

.

LRDP-10-n Version a

Test Threshold 1* , ** Set PD = 95% against a Target Leak Rate > MDL to insure PFA < 5%

Target Leak Rate, TLR – gal/h [(1.139/n 0.5 ) (A 2 /11,786] = 0.2
such that 1 < n < 12 or 0.2 for [(1.139/n 0.5 ) (A 2 /11,786)] < 0.2

Threshold,

C – gal/h [TLR-((0.569)/n 0.5 ) (A 2 /11,786] > 0.1 such that 1 < n < 12
or 0.1 for [TLR-((0.569)/n 0.5 ) (A 2 /11,786] < 0.1

PD – % 95%

PFA - % < 5%

*There may be more than one threshold specification for system operation; TLR = target leak rate. ** MDL = 1.14 gal/h; S = 0.317 gal/h; and A 1 = 11,786 ft 2 ; 1 < n < 12 .

### Appendix F

Performance Equations for V ersions 1.0a, 1.1a, and 1.2a of the LRDP-10, LRDP-24, LRDP-10-n and LRDP-24-nF-2 Operation of the Evaluated System as Designed

LRDP-24 Mass Based Systems (with scaling included)

Version 1.0a
Test Threshold * , ** Set PD = 95% against a Target Leak

Rate > MDL
to insure PFA < 5% Version 1.1a
Test Threshold 2**
Set PFA < 5% and set

PD > 95% such that the Target Leak

Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h TLR > [MDL (A 2 /A 1 )] > 0.2
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2 [ α MDL (A 2 /A 1 )] > 0.2
or 0.2 for [( α MDL (A 2 /A 1 )] < 0.2

such that α < 2 [MDL (A 2 /A 1 )] > 0.2
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2

Threshold, C – gal/h [TLR - C MDL (A 2 /A 1 )] > 0.1 or 0.1
for [TLR – C MDL (A 2 /A 1 )] < 0.1 [ β MDL (A 2 /A 1 )] > 0.1
or 0.1 for [( β MDL (A 2 /A 1 )] < 0.1

such that α < 2 [(C MDL = MDL/2) (A 2 /A 1 )] > 0.1
or 0.1 for [(MDL/2) (A 2 /A 1 )] < 0.1

PD – % 95% > 95% 95%

PFA - % < 5% < 5% 5% *There may be more than one thre shold specification for system oper ation; TLR = target leak rate.

**Define MDL and C MDL = MDL/2 for A 1 ; S for A 1 ; and A 1 ; α < 2 and β is a constant multiplier on MDL

Operation of the Evaluated System as Designed

LRDP-24-n Mass Based Systems (with scal ing and averaging included)

Version 1.0a
Test Threshold 1* , ** Set PD = 95% against a Target
Leak Rate > MDL
To insure PFA < 5% Version 1.1a
Test Threshold 2**
Set PFA < 5% and set

PD > 95% such that the Target Leak

Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h [(MDL/n 0.5 ) (A 2 /A 1 )] = 0.2
such that 1 < n < 12
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2 [( α MDL//n 0.5 ) (A 2 /A 1 )] > 0.2
or 0.2 for [( α MDL//n 0.5 ) (A 2 /A 1 )] < 0.2

such that α < 2 [(MDL/n 0.5 ) (A 2 /A 1 )] > 0.2
or 0.2 for [(MDL//n 0.5 ) (A 2 /A 1 )] < 0.2

Threshold, C – gal/h [TLR-(C MDL /n 0.5 ) (A 2 /A 1 )] > 0.1
such that 1 < n < 12
or 0.1 for [TLR- (C MDL /n 0.5 ) (A 2 /A 1 )] < 0.1 [( β MDL/n 0.5 ) (A 2 /A 1 )] )] > 0.1
or 0.1 for [( β MDL//n 0.5 ) (A 2 /A 1 )] < 0.1

such that α < 2 [(0.5 MDL/n 0.5 ) (A 2 /A 1 )] )] > 0.1
or 0.1 for [(0.5 MDL//n 0.5 ) (A 2 /A 1 )] < 0.1

PD – % 95% > 95% 95%

PFA - % < 5% < 5% 5% *There may be more than one thre shold specification for system oper ation; TLR = target leak rate.

**Define MDL and C MDL = MDL/2 for A 1 ; S for A 1 ; and A 1 ; α < 2 and β is a constant multiplier on MDL; 1 < n < 12F-3 LRDP-24

Version 1.0a
Test Threshold 1* , ** Set PD = 95% against a Target Leak

Rate > MDL to insure PFA < 5% Version1.1a
Test Threshold 2**
Set PFA < 5% and set
PD = 95% such that the Target Leak Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h [0.69 (A 2 /11,786)] > 0.2
or 0.2 for [0.69 (A 2 /11,786)] < 0.2 [1.3711 (0.69) (A 2 /11,786)] > 0.2 or
0.2 for [(1.3711 (0.69) (A 2 /11,786] < 0.2

such that α < 2 [0.69 (A 2 /11,786)] > 0.2
or 0.2 for [(MDL (A 2 /A 1 )] < 0.2

Threshold, C – gal/h [TLR – (0.345) (A 2 /11,786)] > 0.1
or 0.1 for [TLR – (0.345) (A 2 /A 1 )] < 0.1 [0.8711) (0.69) (A 2 /11,786)] > 0.1
or 0.1 for [(0.8711) (0.69) (A 2 /11,786)] < 0.1

such that α < 2 [0.345 (A 2 /11,786)] > 0.1
or 0.1 for [(0.345 (A 2 /11,786)] < 0.1

PD – % 95% 95% 95%

PFA - % < 5% 0.48% 5%

*There may be more than one thre shold specification for system oper ation; TLR = target leak rate. **MDL = 0.69 gal/h; S = 0.192 gal/h; and A 1 = 11,786 ft 2 ; α = 1.3711; β = 0.8711.

LRDP-24-n

Version 1.0a
Test Threshold 1* , ** Set PD = 95% against a Target Leak

Rate > MDL to insure PFA < 5% Version 1.1a
Test Threshold 2**
Set PFA < 5% and set
PD = 95% such that the Target Leak Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h [(0.69/n 0.5 ) (A 2 /11,786] = 0.2
such that 1 < n < 12

or 0.2 for [(0.69/n 0.5 ) (A 2 /11,786)] < 0.2 [(1.3711 (0.69)//n 0.5 ) (A 2 /11,786)] > 0.2
or 0.2 for [(1.3711 (0.69)//n 0.5 ) (A 2 /11,786)] < 0.2

such that α < 2 [(0.69/n 0.5 ) (A 2 /11,786)] > 0.2
or 0.2 for [(0.69//n 0.5 ) (A 2 /11,786)] < 0.2

Threshold, C – gal/h [TLR-((0.345)/n 0.5 ) (A 2 /11,786] > 0.1
such that 1 < n < 12
and 0.1 for [TLR-((0.345)/n 0.5 ) (A 2 /11,786] < 0.1 [0.8711) (0.69)/n 0.5 ) (A 2 /11,786)] > 0.1
or 0.1 for [(0.8711) (0.69)//n 0.5 ) (A 2 /11,786)] < 0.1

such that α < 2 [(0.345/n 0.5 )} (A 2 /11,786)] )] > 0.1
or 0.1 for [(0.345/n 0.5 ) (A 2 /11,786)] < 0.1

PD – % 95% 95% 95%

PFA - % < 5% 0.48% 5%

*There may be more than one thre shold specification for system oper ation; TLR = target leak rate. **MDL = 0.69 gal/h; S = 0.192 gal/h; and A 1 = 11,786 ft 2 ; α = 1.3711; β = 0.8711; 1 < n < 12.F-4 LRDP-10

Version 1.0a
Test Threshold 1* , ** Set PD = 95% against a Target
Leak Rate > MDL to insure PFA <
5% Version 1.1a
Test Threshold 2**
Set PFA < 5% and set
PD = 95% such that the Target Leak Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set
PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h [(1.139) (A 2 /11,786)] > 0.2
or 0.2 for [(1.139) (A 2 /11,786)] < 0.2 [(1.4514) (1.139) (A 2 /11,786)] > 0.2
or 0.2 for [(1.4514) (A 2 /11,786)] < 0.2

such that α < 2 [1.139 (A 2 /11,786)] > 0.2
or 0.2 for [(1.139) (A 2 /11,786] < 0.2

Threshold, C – gal/h [TLR – (0.569) (A 2 /11,786)] > 0.1
or 0.1 for [TLR – (0.569) (A 2 /11,786)] < 0.1 [0.9514) (1.139) (A 2 /11,786)] > 0.1
or 0.1 for [(0.9514) (1.139) (A 2 /11,786)] < 0.1

such that α < 2 [(0.569) (A 2 /11,786)] > 0.1
or 0.1 for [(0.569) (A 2 /11,786)] < 0.1

PD – % 95% 95% 95%

PFA - % < 5% 0.29% 5%

*There may be more than one thre shold specification for system oper ation; TLR = target leak rate. **MDL = 1.14 gal/h; S = 0.317 gal/h; and A 1 = 11,786 ft 2 ; α = 1.4514; β = 0.9514.

LRDP-10-n

Version 1.0a
Test Threshold 1* , ** Set PD = 95% against a Target Leak

Rate > MDL to insure PFA < 5% Version 1.1a
Test Threshold 2**
Set PFA < 5% and set
PD = 95% such that the Target Leak Rate < 2 scaled-MDL Version 1.2a
Test Threshold 3** Operate at the MDL (Set PD = 95% and set PFA = 5%)

Target Leak Rate, TLR – gal/h [(1.139/n 0.5 ) (A 2 /11,786] = 0.2
such that 1 < n < 12
or 0.2 for [(1.139/n 0.5 ) (A 2 /11,786)] < 0.2 [(1.4514) (1.139)//n 0.5 ) (A 2 /11,786)] > 0.2
or 0.2 for [(1.4514 (1.139)//n 0.5 ) (A 2 /11,786)] < 0.2

such that α < 2 [(1.139/n 0.5 ) (A 2 /11,786)] > 0.2
or 0.2 for [(1.139//n 0.5 ) (A 2 /11,786)] < 0.2

Threshold, C – gal/h [TLR-((0.569)/n 0.5 ) (A 2 /11,786] > 0.1
such that 1 < n < 12
or 0.1 for [TLR-((0.569)/n 0.5 ) (A 2 /11,786] < 0.1 [0.9514) (1.139)/n 0.5 ) (A 2 /11,786)] > 0.1
or 0.1 for [(0.9514) (1.139)//n 0.5 ) (A 2 /11,786)] <

0.1

such that α < 2 [(0.569/n 0.5 )} (A 2 /11,786)] )] > 0.1
or 0.1 for [(0.569/n 0.5 ) (A 2 /11,786)] < 0.1

PD – % 95% 95% 95%

PFA - % < 5% 0.29% 5%

*There may be more than one thre shold specification for system oper ation; TLR = target leak rate. ** MDL = 1.14 gal/h; S = 0.317 gal/h; and A 1 = 11,786 ft 2 ; α = 1.4514; β = 0.9514; 1 < n < 12 .

### Appendix G

Performance Estimates for the LRDP-10 for Versions 1.0a, 1.1a, and 1.2a
as a Function of TLR and Tank DiameterG-2 Table G-1. LRDP-10. The threshold is set to give the MDLR (i.e., a system with a P D = 95% and a P FA = 5%) by selecting a threshold that gives a P D = 95% and a P FA = 5%. (Version 1.2a)

Index Volume Ht Dia Area MDLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 1.14 0.317 0.569 5.0% 95.0%

1 204,093 13.2 51.30 2,067 0.20 0.056 0.100 5.0% 95.0% 1.0 2 433,533 14.0 72.60 4,140 0.40 0.111 0.200 5.0% 95.0% 4.0 3 500,687 13.2 80.35 5,071 0.49 0.136 0.245 5.0% 95.0% 6.0 4 1,255,054 23.4 95.55 7,170 0.69 0.193 0.346 5.0% 95.0% 2 12.0 5 306,341 13.2 62.85 3,102 0.30 0.083 0.150 5.0% 95.0% 2.2 6 1,548,582 20.0 114.80 10,351 1.00 0.278 0.500 5.0% 95.0% 7 3,097,099 20.0 162.35 20,701 2.00 0.557 1.000 5.0% 95.0% 8 4,643,904 20.0 198.80 31,040 3.00 0.835 1.499 5.0% 95.0% 9 600,565 13.2 88.00 6,082 0.59 0.164 0.294 5.0% 95.0% 8.6 10 2,125,666 20 134.50 14,208 1.37 0.382 0.686 5.0% 95.0%
11 2,274,866 20 134.50 15,205 1.47 0.409 0.734 5.0% 95.0%
12 5,157,611 23.4 193.69 29,465 2.85 0.793 1.423 5.0% 95.0%

Table G-2. LRDP-10. The threshold is set to give a specific P FA < 5% and a specific P D > 95%. The largest tank needs to be below the regulatory standard (e.g., 2 gal/h). This is accomplished by selecting a threshold that gives
the P D and P FA of interest. The target leak rate is le ss or equal to twice the MDLR. (Version 1.1a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 1.65 0.317 1.083 0.288% 95.0%

1 140,739 13.2 42.60 1,425 0.20 0.038 0.131 0.288% 95.0% 1.0 2 281,987 13.2 60.30 2,856 0.40 0.077 0.262 0.288% 95.0% 4.0 3 344,504 13.2 66.65 3,489 0.49 0.094 0.321 0.288% 95.0% 6.0 4 864,695 23.4 79.31 4,940 0.69 0.133 0.454 0.288% 95.0% 12.0 5 211,479 13.2 52.22 2,142 0.30 0.058 0.197 0.288% 95.0% 2.3 6 1,067,177 20.0 95.30 7,133 1.00 0.192 0.656 0.288% 95.0% 7 2,133,576 20.0 134.75 14,261 2.00 0.384 1.311 0.288% 95.0% 8 3,200,970 20.0 165.05 21,395 3.00 0.575 1.967 0.288% 95.0% 9 600,565 13.2 88.00 6,082 0.85 0.164 0.559 0.288% 95.0% 10 2,125,666 20.0 134.50 14,208 1.99 0.382 1.306 0.288% 95.0% 11 2,274,866 20.0 139.14 15,205 2.13 0.409 1.398 0.288% 95.0% 12 5,157,611 23.4 193.69 29,465 4.13 0.793 2.708 0.288% 95.0%G-3 Table G-3. LRDP-10. The threshold is set to give a specific P FA < 5% and a specific P D > 95%. The largest tank needs to be below the regulatory standard (e.g., 2 gal/h). This is accomplished by selecting a threshold that gives the

P D and P FA of interest. The TLR = 1.90 gal/h for the evaluation tank. (Version 1.0a TLR = 1.9 gal/h)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 1.90 0.317 1.330 0.075% 95.0%

1 122,537 13.2 39.75 1,241 0.20 0.033 0.140 0.075% 95.0% 1.0 2 245,119 13.2 56.22 2,482 0.40 0.067 0.280 0.075% 95.0% 4.0 3 300,037 13.2 62.20 3,039 0.49 0.082 0.343 0.075% 95.0% 6.0 4 752,723 23.4 73.99 4,300 0.69 0.116 0.485 0.075% 95.0% 12.0 5 183,930 13.2 48.70 1,863 0.30 0.050 0.210 0.075% 95.0% 2.3 6 612,912 13.2 88.90 6,207 1.00 0.167 0.700 0.075% 95.0% 7 1,856,612 20.0 125.70 12,410 2.00 0.334 1.400 0.075% 95.0% 8 2,784,902 20.0 153.95 18,614 3.00 0.501 2.100 0.075% 95.0% 9 600,565 13.2 88.00 6,082 0.98 0.164 0.686 0.075% 95.0% 10 2,125,666 20.0 134.50 14,208 2.29 0.382 1.603 0.075% 95.0% 11 2,274,866 20.0 139.14 15,205 2.45 0.409 1.715 0.075% 95.0% 12 5,157,611 23.4 193.69 29,465 4.75 0.793 3.324 0.075% 95.0%

Table G-4. LRDP-10

. The threshold is set to give a specific P D > 95% and the P FA , which needs to be less than or equal to 5%, is computed for this P D . The TLR = 2.40 gal/h for the evaluation tank. (Version 1.0a TLR = 2.4 gal/h)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 2.40 0.317 1.831 0.00619% 95.0%

1 96,911 13.2 35.35 981 0.20 0.026 0.152 0.00619% 95.0% 1.0 2 193,881 13.2 50.00 1,963 0.40 0.053 0.305 0.00619% 95.0% 4.0 3 237,505 13.2 55.34 2,405 0.49 0.065 0.374 0.00619% 95.0% 6.0 4 595,429 23.4 65.81 3,402 0.69 0.091 0.528 0.00619% 95.0% 12.0 5 145,402 13.2 43.30 1,473 0.30 0.040 0.229 0.00619% 95.0% 2.2 6 734,453 20.0 79.06 4,909 1.00 0.132 0.763 0.00619% 95.0% 7 1,469,492 20.0 111.83 9,822 2.00 0.264 1.526 0.00619% 95.0% 8 2,203,812 20.0 136.95 14,730 3.00 0.396 2.288 0.00619% 95.0% 9 600,565 13.2 88.00 6,082 1.24 0.164 0.945 0.00619% 95.0% 10 2,125,666 20.0 134.50 14,208 2.89 0.382 2.207 0.00619% 95.0% 11 2,274,866 20.0 139.14 15,205 3.10 0.409 2.362 0.00619% 95.0% 12 5,157,611 23.4 193.69 29,465 6.00 0.793 4.577 0.00619% 95.0%H-1 

### Appendix H

Performance Estimates for the LRDP-24 for Versions 1.0a, 1.1a, and 1.2a
as a Function of TLR and Tank DiameterH-2 Table H-1. LRDP-24 . The threshold is set to give the MDLR (i.e., a system with a P D = 95% and a P FA = 5%) by selecting a threshold that gives a P D = 95% and a P FA = 5%. (Version 1.2a)

Index Volume Ht Dia Area MDLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 0.69 0.192 0.345 5.0% 95.0% 11.9

1 337,306 13.2 65.95 3,416 0.20 0.056 0.100 5.0% 95.0% 1.0 2 1,022,854 20.0 93.30 6,837 0.40 0.111 0.200 5.0% 95.0% 4.0 3 1,252,653 20.0 103.25 8,373 0.49 0.136 0.245 5.0% 95.0% 6.0 4 2,072,501 23.4 122.78 11,840 0.69 0.193 0.346 5.0% 95.0% 12.0 5 767,138 20.0 80.80 5,128 0.30 0.084 0.150 5.0% 95.0% 2.3 6 2,555,394 20.0 147.47 17,080 1.00 0.278 0.500 5.0% 95.0% 7 5,113,039 20.0 208.60 34,176 2.00 0.557 1.000 5.0% 95.0% 8 7,670,653 20.0 255.50 51,271 3.00 0.835 1.500 5.0% 95.0% 9 600,565 13.2 88.00 6,082 0.36 0.099 0.178 5.0% 95.0% 3.2 10 2,125,666 20 134.50 14,208 0.83 0.231 0.416 5.0% 95.0% 11 2,274,866 20.0 139.14 15,205 0.89 0.248 0.445 5.0% 95.0% 12 5,157,611 23.4 193.69 29,465 1.72 0.480 0.862 5.0% 95.0%

Table H-2. LRDP-24

. The threshold is set to give a specific P FA < 5% and a specific P D > 95%. The largest tank needs to be below the regulatory standard (e.g., 2 gal/h). This is accomplished by selecting a threshold that gives the

P D and P FA of interest. The target leak rate is le ss or equal to twice the MDLR. (Version 1.1a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%)

Eval 2,063,044 23.4 122.50 11,786 0.95 0.192 0.601 0.480% 95.0%

1 262,577 14.1 56.30 2,489 0.20 0.041 0.127 0.480% 95.0% 1.0 2 492,619 13.2 79.70 4,989 0.40 0.081 0.254 0.480% 95.0% 4.0 3 602,887 13.2 88.17 6,106 0.49 0.099 0.311 0.480% 95.0% 6.0 4 1,511,447 23.4 104.85 8,635 0.69 0.141 0.440 0.480% 95.0% 12.0 5 369,226 13.2 69.00 3,739 0.30 0.061 0.191 0.480% 95.0% 2.2 6 1,865,484 20.0 126.00 12,469 1.00 0.203 0.636 0.480% 95.0% 7 3,729,256 20.0 178.15 24,927 2.00 0.406 1.270 0.480% 95.0% 8 5,594,483 20.0 218.20 37,394 3.00 0.609 1.906 0.480% 95.0% 9 600,565 13.2 88.00 6,082 0.49 0.099 0.310 0.480% 95.0% 6.0 10 2,125,666 20.0 134.50 14,208 1.14 0.231 0.724 0.480% 95.0% 11 2,274,866 20.0 139.14 15,205 1.22 0.248 0.775 0.480% 95.0% 12 5,157,611 23.4 193.69 29,465 2.36 0.480 1.502 0.480% 95.0%H-3 Table H-3. LRDP-24

. The threshold is set to give a specific P D > 95% and the P FA , which needs to be less than or equal to 5%, is computed for this P D . The TLR = 1.65 gal/h for the evaluation tank. (Version 1.0a TLR = 1.65 gal/h)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 1.65 0.192 1.305 0.00148% 95.0%

1 141,069 13.2 42.65 1,429 0.20 0.023 0.158 0.00148% 95.0% 1.0 2 281,987 13.2 60.30 2,856 0.40 0.047 0.316 0.00148% 95.0% 4.0 3 345,539 13.2 66.75 3,499 0.49 0.057 0.388 0.00148% 95.0% 6.0 4 866,271 23.4 79.38 4,949 0.69 0.081 0.548 0.00148% 95.0% 12.0 5 211,317 13.2 52.20 2,140 0.30 0.035 0.237 0.00148% 95.0% 2.2 6 705,076 13.2 95.35 7,141 1.00 0.116 0.791 0.00148% 95.0% 7 2,136,744 20.0 134.85 14,282 2.00 0.233 1.582 0.00148% 95.0% 8 3,202,909 20.0 165.10 21,408 3.00 0.349 2.371 0.00148% 95.0% 9 600,565 13.2 88.00 6,082 0.85 0.099 0.674 0.00148% 95.0% 10 2,125,666 20.0 134.50 14,208 1.99 0.231 1.573 0.00148% 95.0% 11 2,274,866 20.0 139.14 15,205 2.13 0.248 1.684 0.00148% 95.0% 12 5,157,611 23.4 193.69 29,465 4.13 0.480 3.263 0.00148% 326.3% 2 0.9

Table H-4. LRDP-24. The threshold is set to give a specific P D > 95% and the P FA , which needs to be less than or equal to 5%, is computed for this P D . The TLR = 2.40 gal/h for the evaluation tank. (Version 1.0a TLR = 2.40 gal/h)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 2.40 0.192 2.055 0.000019% 95.0%

1 96,911 13.2 35.35 981 0.20 0.016 0.171 0.000019% 95.0% 1.0 2 193,881 13.2 50.00 1,963 0.40 0.032 0.342 0.000019% 95.0% 4.0 3 253,699 14.1 55.34 2,405 0.49 0.039 0.419 0.000019% 95.0% 6.0 4 595,429 23.4 65.81 3,402 0.69 0.055 0.593 0.000019% 95.0% 12.0 5 145,402 13.2 43.30 1,473 0.30 0.024 0.257 0.000019% 95.0% 2.2 6 484,739 13.2 79.06 4,909 1.00 0.080 0.856 0.000019% 95.0% 7 1,469,492 20.0 111.83 9,822 2.00 0.160 1.713 0.000019% 95.0% 8 2,578,460 23.4 136.95 14,730 3.00 0.240 2.569 0.000019% 95.0% 9 600,565 13.2 88.00 6,082 1.24 0.099 1.061 0.000019% 95.0% 10 2,125,666 20.0 134.50 14,208 2.89 0.231 2.478 0.000019% 95.0% 11 2,274,866 20.0 139.14 15,205 3.10 0.248 2.651 0.000019% 95.0% 12 5,157,611 23.4 193.69 29,465 6.00 0.480 5.138 0.000019% 95.0%

### Appendix I

Performance Estimates for the LRDP-10
as a Function of TLR and Tank Diameter (Product Surface Area)
for a Threshold Set to Yield a P D 

### = 95% for the Selected TLRI-2 Table I-1. LRDP-10. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 0.20 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n tests averaged (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.5 11,786 0.200 0.055 0.101 2.295% 95.0% 33.0

1 48,470 13.2 25.0 491 0.200 0.013 0.176 0.000001% 95.0% 1.0 2 69,797 13.2 30.0 707 0.200 0.019 0.166 0.000069% 95.0% 1.0 3 124,084 13.2 40.0 1,257 0.200 0.034 0.139 0.041125% 95.0% 1.0 4 193,881 13.2 50.0 1,963 0.200 0.053 0.105 1.742% 95.0% 1.0 5 279,188 13.2 60.0 2,827 0.200 0.054 0.103 1.956% 95.0% 2.0 6 337,306 13.2 65.950 3,416 0.200 0.053 0.105 1.793% 95.0% 3.0 7 380,006 13.2 70.0 3,848 0.200 0.052 0.107 1.526% 95.0% 4.0 8 496,334 13.2 80.0 5,027 0.200 0.055 0.101 2.298% 95.0% 6.0 9 506,273 13.2 80.8 5,127 0.200 0.052 0.106 1.599% 95.0% 7.0 10 628,173 13.2 90.0 6,362 0.200 0.054 0.103 2.034% 95.0% 10.0 11 1,175,034 20 100.0 7,854 0.200 0.055 0.102 2.137% 95.0% 15.0 12 1,421,791 20 110.0 9,503 0.200 0.054 0.102 2.126% 95.0% 22.0 13 1,692,049 20 120.0 11,310 0.200 0.056 0.100 2.386% 95.0% 30.0 14 1,985,808 20 130.0 13,273 0.200 0.055 0.101 2.271% 95.0% 42.0 15 250,591 14.1 55.0 2,376 0.200 0.045 0.119 0.567% 95.0% 2.0 16 600,565 13.2 88.0 6,082 0.200 0.055 0.102 2.134% 95.0% 9.0 17 2,125,666 20 134.5 14,208 0.200 0.055 0.101 2.289% 95.0% 48.0 18 2,273,551 20 139.1 15,197 0.200 0.056 0.100 2.408% 95.0% 54.0

Table I-2. LRDP-10. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 0.30 gal/h. (Version a)

Index Volume Ht Dia Area MDLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 48,470 13.2 25.00 491 0.30 0.013 0.276 0.000000% 95.0% 2.3

1 69,797 13.2 30.00 707 0.30 0.019 0.266 0.000001% 95.0% 2.3 2 124,084 13.2 40.00 1,257 0.30 0.034 0.239 0.001023% 95.0% 2.3 3 193,881 13.2 50.00 1,963 0.30 0.053 0.205 0.127% 95.0% 2.3 4 204,093 13.2 51.30 2,067 0.30 0.056 0.200 0.208% 95.0% 2.3 5 279,188 13.2 60.00 2,827 0.30 0.076 0.163 2.7% 95.0% 2.3 6 306,633 13.2 62.88 3,105 0.30 0.084 0.150 5.0% 95.0% 2.3 7 250,591 14.1 55.00 2,376 0.30 0.064 0.185 0.7% 95.0% 2.3 8 600,565 13.2 88.00 6,082 0.30 0.164 0.006 48.5% 95.0% 2.3I-3 Table I-3. LRDP-10. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 1.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 1.00 0.317 0.431 10.1% 95.0%

1 48,470 13.2 25.00 491 1.00 0.013 0.976 0.000000% 95.0% 2 69,797 13.2 30.00 707 1.00 0.019 0.966 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 1.00 0.034 0.939 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 1.00 0.053 0.905 0.000000% 95.0% 5 204,093 13.2 51.30 2,067 1.00 0.056 0.900 0.000000% 95.0% 6 279,188 13.2 60.00 2,827 1.00 0.076 0.863 0.000010% 95.0% 7 380,006 13.2 70.00 3,848 1.00 0.104 0.814 0.000384% 95.0% 8 496,334 13.2 80.00 5,027 1.00 0.135 0.757 0.008007% 95.0% 9 628,173 13.2 90.00 6,362 1.00 0.171 0.693 0.096% 95.0% 10 1,175,034 20 100.00 7,854 1.00 0.211 0.621 0.675% 95.0% 11 1,421,791 20 110.00 9,503 1.00 0.256 0.541 2.9% 95.0% 12 1,548,659 20 114.80 10,351 1.00 0.278 0.500 5.0% 95.0% 13 250,591 14.1 55.00 2,376 1.00 0.064 0.885 0.000001% 95.0% 14 600,565 13.2 88.00 6,082 1.00 0.164 0.706 0.061037% 95.0% 15 2,125,666 20 134.50 14,208 1.00 0.382 0.314 21.5% 95.0% 16 2,273,551 20 139.10 15,197 1.00 0.409 0.266 26.4% 95.0%

Table I-4. LRDP-10. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 2.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 2.00 0.317 1.431 0.044% 95.0%

1 48,470 13.2 25.00 491 2.00 0.013 1.976 0.000000% 95.0% 2 69,797 13.2 30.00 707 2.00 0.019 1.966 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 2.00 0.034 1.939 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 2.00 0.053 1.905 0.000000% 95.0% 5 204,093 13.2 51.30 2,067 2.00 0.056 1.900 0.000000% 95.0% 6 279,188 13.2 60.00 2,827 2.00 0.076 1.863 0.000000% 95.0% 7 380,006 13.2 70.00 3,848 2.00 0.104 1.814 0.000000% 95.0% 8 496,334 13.2 80.00 5,027 2.00 0.135 1.757 0.000003% 95.0% 9 628,173 13.2 90.00 6,362 2.00 0.171 1.693 0.000041% 95.0% 10 1,175,034 20 100.00 7,854 2.00 0.211 1.621 0.000485% 95.0% 11 1,421,791 20 110.00 9,503 2.00 0.256 1.541 0.004284% 95.0% 12 1,692,049 20 120.00 11,310 2.00 0.304 1.454 0.029% 95.0% 13 1,985,808 20 130.00 13,273 2.00 0.357 1.359 0.146% 95.0% 14 250,591 14.1 55.00 2,376 2.00 0.064 1.885 0.000000% 95.0% 15 600,565 13.2 88.00 6,082 2.00 0.164 1.706 0.000024% 95.0% 16 2,125,666 20 134.50 14,208 2.00 0.382 1.314 0.146% 95.0% 17 2,273,551 20 139.10 15,197 2.00 0.409 1.266 0.146% 95.0% 18 2,044,211 13.2 162.36 20,702 2.00 0.557 1.000 5.0% 95.0%I-4 Table I-5. LRDP-10. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 3.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 3.00 0.317 2.431 0.000488% 95.0%

1 48,470 13.2 25.00 491 3.00 0.013 2.976 0.000000% 95.0% 2 69,797 13.2 30.00 707 3.00 0.019 2.966 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 3.00 0.034 2.939 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 3.00 0.053 2.905 0.000000% 95.0% 5 204,093 13.2 51.30 2,067 3.00 0.056 2.900 0.000000% 95.0% 6 279,188 13.2 60.00 2,827 3.00 0.076 2.863 0.000000% 95.0% 7 380,006 13.2 70.00 3,848 3.00 0.104 2.814 0.000000% 95.0% 8 496,334 13.2 80.00 5,027 3.00 0.135 2.757 0.000000% 95.0% 9 628,173 13.2 90.00 6,362 3.00 0.171 2.693 0.000000% 95.0% 10 1,175,034 20 100.00 7,854 3.00 0.211 2.621 0.000004% 95.0% 11 1,421,791 20 110.00 9,503 3.00 0.256 2.541 0.000039% 95.0% 12 1,692,049 20 120.00 11,310 3.00 0.304 2.454 0.000302% 95.0% 13 1,985,808 20 130.00 13,273 3.00 0.357 2.359 0.001913% 95.0% 14 250,591 14.1 55.00 2,376 3.00 0.064 2.885 0.000000% 95.0% 15 600,565 13.2 88.00 6,082 3.00 0.164 2.706 0.000000% 95.0% 16 2,125,666 20 134.50 14,208 3.00 0.382 2.314 0.004128% 95.0% 17 2,273,551 20 139.10 15,197 3.00 0.409 2.266 0.008718% 95.0% 18 5,157,611 23.4 193.69 29,465 3.00 0.793 1.577 3.603773% 95.0% 19 3,066,365 13.2 198.85 31,054 3.00 0.835 1.500 5.0% 95.0%

### Appendix J

Performance Estimates for the LRDP-24
as a Function of TLR and Tank Diameter (Product Surface Area)
for a Threshold Set to Yield a P D 

### = 95% for the Selected TLRJ-2 Table J-1. LRDP-24. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 0.20 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n tests averaged (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.5 11,786 0.200 0.055 0.100 4.863% 95.0% 12.0

1 48,470 13.2 25.0 491 0.200 0.008 0.186 0.000000% 95.0% 1.0 2 69,797 13.2 30.0 707 0.200 0.012 0.179 0.000000% 95.0% 1.0 3 124,084 13.2 40.0 1,257 0.200 0.020 0.163 0.000337% 95.0% 1.0 4 193,881 13.2 50.0 1,963 0.200 0.032 0.143 0.048% 95.0% 1.0 5 279,188 13.2 60.0 2,827 0.200 0.046 0.117 1.359% 95.0% 1.0 6 337,306 13.2 65.950 3,416 0.200 0.056 0.100 4.982% 95.0% 1.0 7 380,006 13.2 70.0 3,848 0.200 0.044 0.120 1.004% 95.0% 2.0 8 496,334 13.2 80.0 5,027 0.200 0.047 0.115 1.657% 95.0% 3.0 9 506,273 13.2 80.8 5,127 0.200 0.048 0.113 1.919% 95.0% 3.0 10 628,173 13.2 90.0 6,362 0.200 0.052 0.107 3.173% 95.0% 4.0 11 1,175,034 20 100.0 7,854 0.200 0.052 0.106 3.345% 95.0% 6.0 12 1,421,791 20 110.0 9,503 0.200 0.055 0.102 4.505% 95.0% 8.0 13 1,692,049 20 120.0 11,310 0.200 0.056 0.100 4.930% 95.0% 11.0 14 1,985,808 20 130.0 13,273 0.200 0.054 0.103 4.170% 95.0% 16.0 15 250,591 14.1 55.0 2,376 0.200 0.039 0.130 0.312% 95.0% 1.0 16 600,565 13.2 88.0 6,082 0.200 0.050 0.111 2.330% 95.0% 4.0 17 2,125,666 20 134.5 14,208 0.200 0.055 0.102 4.415% 95.0% 18.0 18 2,273,551 20 139.1 15,197 0.200 0.055 0.101 4.826% 95.0% 20.0

Table J-2. LRDP-24. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 0.30 gal/h. (Version a)

Index Volume Ht Dia Area MDLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 48,470 13.2 25.00 491 0.30 0.008 0.286 0.000000% 95.0% 2.3

1 69,797 13.2 30.00 707 0.30 0.012 0.279 0.000000% 95.0% 2.3 2 124,084 13.2 40.00 1,257 0.30 0.020 0.263 0.000003% 95.0% 2.3 3 193,881 13.2 50.00 1,963 0.30 0.032 0.243 0.000541% 95.0% 2.3 4 279,188 13.2 60.00 2,827 0.30 0.046 0.217 0.031613% 95.0% 2.3 5 597,952 23.4 65.95 3,416 0.30 0.056 0.200 0.210% 95.0% 2.3 6 380,006 13.2 70.00 3,848 0.30 0.063 0.187 0.616% 95.0% 2.3 7 496,334 13.2 80.00 5,027 0.30 0.082 0.153 4.4% 95.0% 2.3 8 506,273 13.2 80.80 5,127 0.30 0.084 0.150 5.0% 95.0% 2.3 9 600,565 13.2 88.00 6,082 0.30 0.099 0.122 12.2% 95.0% 2.3J-3 Table J-3. LRDP-24. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 1.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%)

Eval 2,063,044 23.4 122.50 11,786 1.00 0.192 0.655 0.290% 95.0%

1 48,470 13.2 25.00 491 1.00 0.008 0.986 0.000000% 95.0% 2 69,797 13.2 30.00 707 1.00 0.012 0.979 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 1.00 0.020 0.963 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 1.00 0.032 0.943 0.000000% 95.0% 5 279,188 13.2 60.00 2,827 1.00 0.046 0.917 0.000000% 95.0% 6 597,952 23.4 65.95 3,416 1.00 0.056 0.900 0.000000% 7 380,006 13.2 70.00 3,848 1.00 0.063 0.887 0.000001% 95.0% 8 496,334 13.2 80.00 5,027 1.00 0.082 0.853 0.000025% 95.0% 9 628,173 13.2 90.00 6,362 1.00 0.104 0.814 0.000389% 95.0% 10 1,175,034 20 100.00 7,854 1.00 0.128 0.770 0.004338% 95.0% 11 1,421,791 20 110.00 9,503 1.00 0.155 0.722 0.034494% 95.0% 12 1,692,049 20 120.00 11,310 1.00 0.184 0.669 0.197% 95.0% 13 1,985,808 20 130.00 13,273 1.00 0.216 0.612 0.820% 95.0% 14 250,591 14.1 55.00 2,376 1.00 0.039 0.930 0.000% 95.0% 15 600,565 13.2 88.00 6,082 1.00 0.099 0.822 0.000% 95.0% 16 2,125,666 20 134.50 14,208 1.00 0.231 0.584 1.4% 95.0% 17 2,273,551 20 139.10 15,197 1.00 0.248 0.555 2.3% 95.0% 18 1,687,589 13.2 147.52 17,091 1.00 0.278 0.500 5.0% 95.0%

Table J-4. LRDP-24. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 2.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 2.00 0.192 1.655 0.000159% 95.0%

1 48,470 13.2 25.00 491 2.00 0.008 1.986 0.000000% 95.0% 2 69,797 13.2 30.00 707 2.00 0.012 1.979 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 2.00 0.020 1.963 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 2.00 0.032 1.943 0.000000% 95.0% 5 279,188 13.2 60.00 2,827 2.00 0.046 1.917 0.000000% 95.0% 6 597,952 23.4 65.95 3,416 2.00 0.056 1.900 0.000000% 7 380,006 13.2 70.00 3,848 2.00 0.063 1.887 0.000000% 95.0% 8 496,334 13.2 80.00 5,027 2.00 0.082 1.853 0.000000% 95.0% 9 628,173 13.2 90.00 6,362 2.00 0.104 1.814 0.000000% 95.0% 10 1,175,034 20 100.00 7,854 2.00 0.128 1.770 0.000001% 95.0% 11 1,421,791 20 110.00 9,503 2.00 0.155 1.722 0.000013% 95.0% 12 1,692,049 20 120.00 11,310 2.00 0.184 1.669 0.000098% 95.0% 13 1,985,808 20 130.00 13,273 2.00 0.216 1.612 0.000636% 95.0% 14 250,591 14.1 55.00 2,376 2.00 0.039 1.930 0.000000% 95.0% 15 600,565 13.2 88.00 6,082 2.00 0.099 1.822 0.000000% 95.0% 16 2,125,666 20 134.50 14,208 2.00 0.231 1.584 0.001391% 95.0% 17 2,273,551 20 139.10 15,197 2.00 0.248 1.555 0.002989% 95.0% 18 5,157,611 23.4 193.69 29,465 2.00 0.480 1.138 1.855026% 113.8% 0.9 19 3,375,098 13.2 208.62 34,181 2.00 0.557 1.000 5.0% 95.0%J-4 Table J-5. LRDP-24. The threshold is set to give a P D = 95% against a specific TLR given that the P FA < 5%. The

P FA will change with tank size, because the TLR is the same for all tank sizes. The TLR = 3.00 gal/h. (Version a)

Index Volume Ht Dia Area TLR Std Dev Threshold P FA P D n for
LR=0.2

gal/h (gal) (ft) (ft) ( ft 2 ) (gal/h) (gal/h) (gal/h) (%) (%) Eval 2,063,044 23.4 122.50 11,786 3.00 0.192 2.655 0.000001% 95.0%

1 48,470 13.2 25.00 491 3.00 0.008 2.986 0.000000% 95.0% 2 69,797 13.2 30.00 707 3.00 0.012 2.979 0.000000% 95.0% 3 124,084 13.2 40.00 1,257 3.00 0.020 2.963 0.000000% 95.0% 4 193,881 13.2 50.00 1,963 3.00 0.032 2.943 0.000000% 95.0% 5 279,188 13.2 60.00 2,827 3.00 0.046 2.917 0.000000% 95.0% 6 597,952 23.4 65.95 3,416 3.00 0.056 2.900 0.000000% 7 380,006 13.2 70.00 3,848 3.00 0.063 2.887 0.000000% 95.0% 8 496,334 13.2 80.00 5,027 3.00 0.082 2.853 0.000000% 95.0% 9 628,173 13.2 90.00 6,362 3.00 0.104 2.814 0.000000% 95.0% 10 1,175,034 20 100.00 7,854 3.00 0.128 2.770 0.000000% 95.0% 11 1,421,791 20 110.00 9,503 3.00 0.155 2.722 0.000000% 95.0% 12 1,692,049 20 120.00 11,310 3.00 0.184 2.669 0.000001% 95.0% 13 1,985,808 20 130.00 13,273 3.00 0.216 2.612 0.000005% 95.0% 14 250,591 14.1 55.00 2,376 3.00 0.039 2.930 0.000000% 95.0% 15 600,565 13.2 88.00 6,082 3.00 0.099 2.822 0.000000% 95.0% 16 2,125,666 20 134.50 14,208 3.00 0.231 2.584 0.000012% 95.0% 17 2,273,551 20 139.10 15,197 3.00 0.248 2.555 0.000027% 95.0% 18 5,157,611 23.4 193.69 29,465 3.00 0.480 2.138 0.048603% 95.0% 19 5,062,631 13.2 255.50 51,271 3.00 0.835 1.500 5.0% 95.0%