METHOD FOR EXTENDING THE TIME BETWEEN OUT-OF-SERVICE, IN-TANK INSPECTIONS USING ULTRASONIC SENSOR

Abstract

A method and apparatuses to extend the time interval between out-of-service, in-tank inspections while insuring structural integrity using a risk-based, Bayesian statistical approach comprised of a passing leak detection test and the using the results from (1) tank floor thickness measurements, (2) prior out-of-service tank floor inspection results, and/or (3) acoustic emission corrosion maps of the tank floor to estimate the minimum thickness and maximum corrosion rate of the tank during the extension period. The present invention uses an in-tank, mass-based leak detection system to establish tank integrity, three or more ultrasonic (UT) thickness measurement sensors for measurements of the tank floor at one location, and to establish the spatial distribution of corrosion of the tank floor, one or more prior API 653/12R1 or STI SP001 tank floor thickness inspections and/or three or more in-tank AE sensors mounted inside the tank with vertical and horizontal locations in an oblique plane relative to the tank floor.

Claims

1. A method for determining an integrity of a storage tank including a tank floor, comprising the steps of: (a) performing a leak-detection test; (b) determining that the tank is not leaking based on a result of the leak detection test; (c) estimating a thickness of the tank floor in at least one location of the tank at one or more places, wherein the thickness of the tank floor over at least one region of the tank is measured in-tank and used to estimate a corrosion rate and the thickness of the tank floor as a function of a selected time period to determine if a minimum floor thickness can be maintained during said period, and wherein in-tank floor thickness estimates are made using an ultrasonic thickness (UT) measurement sensor; and (d) conducting a risk assessment using statistical data of tank failures including data related to tank corrosion conditions, thereby assessing a probability of structural failure or leaking of the tank within the selected time period.

Description

IN THE DRAWINGS

[0047] FIG. 1 illustrates the preferred method and apparatus of the present invention with an in-tank floor thickness and an in-tank corrosion assessment system integrated with the mass-based leak detection system.

[0048] FIG. 2 illustrates the preferred method and apparatus of the present invention with an in-tank floor thickness and an in-tank corrosion assessment system separated from the mass-based leak detection system.

[0049] FIG. 3 illustrates an alternative embodiment of the preferred method and apparatus of the present invention with an in-tank floor thickness system integrated with the mass-based leak detection system and combined with an external walled-mounted corrosion assessment system.

[0050] FIG. 4 illustrates an alternative embodiment of the preferred method and apparatus of the present invention with an in-tank floor thickness system separated from the mass-based leak detection system and combined with an external walled-mounted corrosion assessment system.

[0051] FIG. 5 illustrates a cumulative frequency distribution (CFD) of floor thickness in an aboveground tank. The distribution is normally distributed and three standard deviations would normally predict the lowest and highest floor thickness.

[0052] FIG. 6 illustrates the CFDs of the floor thickness of the five aboveground storage tanks analyzed.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The method and apparatuses of the present invention can be used to provide critical data and information about the structural integrity of an aboveground or bulk underground storage tank needed to better prioritize and better schedule out-of-service tank inspections for these tanks, because it can be used to assess the condition of the tank floor, i.e., the thickness of the tank floor, the rate of corrosion of the floor, and whether or not any holes or cracks exist in the floor. If the floor is in good condition, then it is possible to postpone a scheduled inspection or to extend the time between inspections so that the maintenance and repair activities can focus on those tanks with the most need.

[0054] The method is comprised of a leak detection test and one or more actual measurements of the thickness and corrosion condition of the bottom floor of the tank in a least one section of the tank. This approach will work well for tanks in which the corrosion is either small or relatively uniform. If not, information about the spatial distribution of floor thickness and corrosion rate is needed to better use these data. This spatial information can be obtained from (1) thickness measurements of the floor of the tank using UT and/or magnetic flux or eddy current measurements made in previous out-of-service inspections according to API 653, AP12R1, or STI SP001, and/or (2) an AE inspection of the tank floor to assess the corrosion condition of the tank floor. The method and the apparatuses of the present invention provide important data to risk-based inspection assessments.

[0055] If an API 653 floor inspection was conducted previously, the results of this inspection can be used to increase the confidence in the risk assessment performed to determine if a scheduled tank inspection can be extended without risk of tank failure or a leak. The bottom inspection gives the results of bottom thickness measurements on all plates comprising the floor. Each plate can have a different rate of corrosion or initial thickness. The rate of corrosion can vary because of some inhomogeneity in the soil beneath the tank that accelerates local corrosion on the external or underneath side of the bottom or some local pools of water on the inside of the tank due to deflection in the tank floor. A complete floor inspection according to API 653 will identify such local pockets of accelerated corrosion. This information can be used to make a more conservative estimate of the corrosion rate for future local measurements of bottom thickness on one or a limited number of plates. This is really conservative since once these problem areas are identified, they are usually addressed as part of the API 653 inspection before the tank is brought back into service for another 10-year period. Even so, the UT thickness data provided during the tank test is used to estimate the corrosion rate between the last thickness measurement in the same location can be used to re-estimate the rate of corrosion at all of the previous measurements by the ratio of the local UT measurement and the previous API floor inspection measurements. Thus, if in the previous API 653 Inspection a corrosion rate of 0.035 in./year was estimated and the UT thickness measurement is different (higher or lower), the ratio of the corrosion rate measured with the UT sensor and the previous corrosion rate can be used to forecast the corrosion rate in the tank using the largest rate measurement in the previous API inspection. This corrosion rate can be used to extend the interval between inspections until the minimum plate thickness is met. This computation is really conservative, because it assumes that none of the corrective action taken at the last API 653 Inspection was of any value.

[0056] FIG. 1 illustrates the preferred method and apparatus of the present invention. It is comprised of a mass-based leak detection test (LRPD) 100 inserted into the tank 10 an at convenient opening 72 at the top of the tank, a set of at least three ultrasonic thickness sensors 142, 144, 146 on an arm 130 attached to the leak detection sensor tube 204, 206, and either the results of a previous out-of-service inspection of the tank floor via API 653, API12R1,′ STI SP001 or other approved inspection method and/or a set of three AE sensors 124, 134, 136 located near the bottom 60 of the tank 10 with one of the sensors 124 located at a different elevation from an ann 120 attached to the tube 204 and in a different plane than the other two sensors. FIG. 2 illustrates a very similar but alternative embodiment where the leak detection system 200 is separated from the UT and AE measurement system 100 and is inserted into a different opening 70 at the top of the tank. Both embodiments will produce very similar results. FIGS. 3 and 4 illustrate measurement configurations similar to FIGS. 1 and 2 except the AE sensors 124, 134, 136 are mounted on the outside wall 12 of the tank 10, where one of the sensors 124 is mounted at a different elevation than the other sensors. The elevation difference for AE measurements from both the internal and external sensor location allows for acoustic signals generated on the surface 50/top 40 part of the tank to be distinguished from acoustic signals generated from the floor 60 of the tank. This prevents false alarms on the surface due to condensation drips.

[0057] The preferred method of measuring thickness of the tank floor is to use one or more ultrasonic (UT) thickness probes that make contact with the floor and AE sensors that detect the presence of corrosion noise (or leaks) that propagate through the liquid product. The AE sensors can be placed on the external wall of the tank, or inserted in the product inside the tank on the staff used to make the UT floor thickness measurements, where at least one of the sensors is at a different elevation than the other sensors and not in the same vertical plane. The preferred configuration is three sensors mounted in the liquid inside the tank as illustrated in FIG. 1 or 2. Additional floor thickness measurements can be made by adding one or more additional UT sensor systems anus 130 at the bottom of the leak detection system in FIGS. 1 and 3 or to the bottom 130 of the staff 104 in FIGS. 2 and 4. Additional UT measurements can be most easily made with any of the two basic configurations by rotating the leak detection tube 204 or the mounting staff 104. This is possible because the UT measurements can be made in less than 1 min.

[0058] An analysis of the out-of-service, internal inspection of the floor of the tank obtained using the UT sensor thickness data was performed to determine if a small sample (i.e., 3 to 6) could be used to accurately estimate the minimum thickness and the maximum corrosion rate of the tank floor using a small number of UT measurements obtained in a local area of the tank when there were no local hot spots or high areas of corrosion. Approximately 4 or more UT thickness measurements were made per tank floor panel. We analyzed the inspections from five large USTs with ages ranging from 13 to 15 years old and diameters of 69.7 ft (3 tanks), 37.7 ft (1 tank) and 26.3 (1 tank). Table 4 presents an illustration for one of five cylindrical USTs; the histograms of the data in Table 4 are illustrated in FIG. 5 as a cumulative frequency distribution (CFD). The CFDs of all five tanks in illustrated in FIG. 6. Table 5 presents the results from a 82.5-ft-diameter aboveground storage tank containing 1,040,000 gal that was built in 1976 and last inspected in 2009 (34 years old). The tables summarize the statistics for each panel and for the floor as a whole. The general conclusion is that 3 to 6 UT measurements made on any floor panel or group of floor panels would be sufficient to make a good estimate of the minimum measured thickness and therefore the maximum corrosion rate. This estimate is made from by subtracting 3 times the standard deviation from the mean or median or by just using the minimum UT measurement. This is justified from the Gaussian behavior of the histograms.

[0059] The ultimate objective of these measurements is to determine if a scheduled out-of-service inspection should be performed now or can it be postponed so another inspection can be performed. The Extension/Postponement Time Interval will depend on the number of tests conducted and the results of these tests and previous measurements. A passing leak detection result with provides the basis for postponing or extending the time interval of an out-of-service inspection. Without any other tests or information about the condition of the tank, the time interval between inspections can be extended a year, which is the time required between tightness test specified by the EPA for smaller tanks to insure their integrity. With floor thickness measurements and some assessment of the spatial distribution of the thickness and corrosion of the tank floor, longer time intervals are possible depending on the extent of the testing and the results of the testing.

[0060] While all of these proposed measurement procedures have been used for tank integrity assessments for many years, they have not been used in combination or for in-service inspections. The proposed method and apparatuses make it possible to prioritize the order for tank inspections and to postpone out-of-service inspections safely for a period of time without taking the tank out of service, by using well understood methods of integrity inspection, and with a high probability that the tank will not structurally fail or leak during the extension period.

TABLE-US-00005 TABLE 4 Summary of the statistics of a UT internal inspection of the tank floor for an 65.6-ft diameter, 733,000-gal UST that is 15 years old. UT UT Reading Plate Reading Number Number (in) Mean StdDev Median Max Min Number 1 1 0.364 0.361 0.006 0.364 0.366 0.352 4 2 1 0.366 3 1 0.352 4 1 0.363 5 1 0.363 0.362 0.005 0.363 0.366 0.351 9 6 1 0.366 7 1 0.359 8 1 0.366 9 1 0.361 10 2 0.358 11 2 0.365 12 2 0.366 13 2 0.351 14 2 0.37 0.366 0.011 0.369 0.383 0.354 6 15 2 0.354 16 2 0.383 17 2 0.354 18 2 0.367 19 2 0.37 20 3 0.361 0.369 0.012 0.367 0.388 0.349 8 21 3 0.383 22 3 0.369 23 3 0.365 24 3 0.365 25 3 0.388 26 3 0.349 27 3 0.368 28 3 0.36 0.366 0.006 0.366 0.374 0.360 4 29 4 0.374 30 4 0.365 31 4 0.366 32 4 0.364 0.361 0.006 0.364 0.367 0.350 12 33 4 0.365 34 4 0.363 35 4 0.354 36 4 0.367 37 5 0.363 38 5 0.366 39 5 0.361 40 5 0.35 41 5 0.364 42 5 0.366 43 5 0.352 44 5 0.365 0.363 0.006 0.365 0.369 0.348 12 45 6 0.367 46 6 0.348 47 6 0.365 48 6 0.356 49 6 0.369 50 6 0.365 51 6 0.362 52 6 0.357 53 6 0.367 54 6 0.365 55 7 0.364 56 7 0.365 0.364 0.003 0.365 0.367 0.356 13 57 7 0.364 58 7 0.366 59 7 0.363 60 7 0.367 61 7 0.356 62 7 0.363 63 8 0.365 64 8 0.363 65 8 0.3652 66 8 0.366 67 8 0.364 68 8 0.367 69 8 0.366 0.364 0.005 0.365 0.373 0.352 13 69 8 0.366 0.364 0.005 0.365 0.373 0.352 13 70 8 0.365 71 8 0.363 72 8 0.373 73 9 0.365 74 9 0.367 75 9 0.352 76 9 0.365 77 9 0.363 78 9 0.364 79 9 0.365 80 9 0.364 81 9 0.365 82 9 0.364 0.364 0.005 0.355 0.369 0.357 4 83 9 0.369 84 9 0.357 85 10 0.367 86 10 0.366 0.366 0.006 0.368 0.371 0.352 8 87 10 0.37 88 10 0.367 89 10 0.352 90 10 0.368 91 10 0.371 92 11 0.368 93 11 0.363 94 11 0.366 0.364 0.005 0.366 0.367 0.355 6 95 11 0.367 96 11 0.355 97 11 0.367 98 11 0.365 99 11 0.363 100 12 0.365 0.362 0.004 0.364 0.366 0.356 8 101 12 0.366 102 12 0.356 103 12 0.363 104 12 0.359 105 12 0.366 106 12 0.356 107 12 0.366 108 12 0.364 0.371 0.005 0.372 0.375 0.364 4 109 13 0.371 110 13 0.375 111 13 0.373 112 14 0.366 0.370 0.005 0.368 0.378 0.366 4 113 14 0.367 114 14 0.378 115 14 0.369 116 14 0.369 0.367 0.002 0.368 0.369 0.364 4 117 14 0.369 118 14 0.367 119 14 0.364 120 15 0.364 Mean StdDev Median Max Min Number Mean 0.365 0.006 0.356 0.372 0.355 0.364 StdDev 0.003 0.003 0.002 0.007 0.005 0.006 Median 0.364 0.005 0.366 0.369 0.355 0.365 Max 0.371 0.012 0.372 0.388 0.366 0.388 Min 0.361 0.002 0.363 0.366 0.348 0.348 Number 16 16 16 16 16 120 3 StDev 0.009 0.008 0.007 0.020 0.017 0.019 Mean − 0.356 −0.002 0.359 0.352 0.339 0.345 3 StDev

TABLE-US-00006 TABLE 5 Summary of the statistics of a UT internal inspection of the tank floor for an 82.5-ft diameter, 1,040,000-gal AST that is over 34 years old. READING 1 READING 2 READING 3 READING 4 READING 5 Mean StDev 1 0.362 0.365 0.367 0.373 0.37 0.367 0.0043 2 0.375 0.378 0.371 0.369 0.368 0.372 0.0042 3 0.366 0.364 0.363 0.369 0.37 0.366 0.0030 4 0.375 0.372 0.363 0.371 0.375 0.371 0.0049 5 0.363 0.365 0.365 0.367 0.368 0.366 0.0019 6 0.375 0.374 0.378 0.369 0.373 0.374 0.0033 7 0.374 0.373 0.372 0.377 0.374 0.374 0.0019 8 0.373 0.375 0.378 0.369 0.37 0.373 0.0037 9 0.375 0.377 0.374 0.37 0.371 0.373 0.0029 10 0.362 0.365 0.366 0.369 0.362 0.365 0.0029 11 0.365 0.364 0.369 0.368 0.37 0.367 0.0026 12 0.375 0.374 0.369 0.378 0.37 0.373 0.0037 13 0.363 0.366 0.368 0.37 0.372 0.368 0.0035 14 0.362 0.362 0.362 0.371 0.364 0.364 0.0039 15 0.365 0.368 0.37 0.37 0.363 0.367 0.0031 16 0.362 0.365 0.366 0.364 0.369 0.365 0.0026 17 0.369 0.37 0.378 0.377 0.37 0.373 0.0043 18 0.37 0.37 0.365 0.372 0.374 0.370 0.0033 19 0.365 0.366 0.369 0.372 0.375 0.369 0.0042 Mean StDev Mean 0.368 0.369 0.369 0.371 0.370 0.369 0.0034 StDev 0.00545 0.00494 0.00504 0.00352 0.00375 0.00344 0.0008 Median 0.366 0.368 0.369 0.370 0.370 0.369 0.0033 Max 0.375 0.378 0.378 0.378 0.375 0.374 0.0049 Min 0.362 0.362 0.362 0.364 0.362 0.364 0.0019 N 19 19 19 19 19 19 19 Mean − 0.352 0.354 0.354 0.360 0.359 0.359 3*StDev Median − Mean − Median Max Min Min 3*StDev 3*StDev 1 0.367 0.373 0.362 0.005 0.0128 0.354 2 0.371 0.378 0.368 0.003 0.0125 0.358 3 0.366 0.370 0.363 0.003 0.0091 0.357 4 0.372 0.375 0.363 0.009 0.0148 0.357 5 0.365 0.368 0.363 0.002 0.0058 0.359 6 0.374 0.378 0.369 0.005 0.0098 7 0.374 0.377 0.372 0.002 0.0056 8 0.373 0.378 0.369 0.004 0.0110 0.362 9 0.374 0.377 0.370 0.004 0.0086 10 0.365 0.369 0.362 0.003 0.0088 0.356 11 0.368 0.370 0.364 0.004 0.0078 0.360 12 0.374 0.378 0.369 0.005 0.0111 13 0.368 0.372 0.363 0.005 0.0105 0.358 14 0.362 0.371 0.362 0.000 0.0117 0.350 15 0.368 0.370 0.363 0.005 0.0093 0.359 16 0.365 0.369 0.362 0.003 0.0078 0.357 17 0.370 0.378 0.369 0.001 0.0130 0.357 18 0.370 0.374 0.365 0.005 0.0100 0.360 19 0.369 0.375 0.365 0.004 0.0125 0.357 Median Max Min Diff Mean 0.369 0.374 0.365 0.004 StDev 0.00368 0.00370 0.00334 0.00193 Median 0.369 0.374 0.364 0.004 Max 0.374 0.378 0.372 0.009 Min 0.362 0.368 0.362 0.000 N 19 19 19 19 Mean − 3*StDev

[0061] The tables below summarize the types of tests and the potential Extension Time Interval in years if one or more of the tests are performed and passed. Table 6 summarizes the methods proposed are (1) a third-party approved leak detection test for like Vista's LRDP mass-based system; (2) ultrasonic (UT) measurements of floor thickness (0.001 in.); (3) a previous API inspection with UT and magnetic flux thickness measurements across the entire tank floor; and (4) an acoustic emission (AE) test for assessing active corrosion across the tank floor. A leak detection test can also be performed with the AE system. Its value is to confirm the approved test and to help interpret the AE corrosion measurements. The Extension Time Interval determined from the measurement program is dependent on the results. Only results a Pass leak detection test is shown. If the tank fails a leak detection test, it should be taken out of service and repair after confirming the presence of a leak.

TABLE-US-00007 TABLE 6 In-Service Tank Inspection Method for Prioritizing Out-of-Service Inspections 3.sup.rd Party UT Extension Approved Thickness API 653/ AE Corro- Time Inspection Leak Detec- at One STI sion/Leak Interval Method tion Test Location SP001 Detection (Years) 1 Yes 1 2 Yes Yes 1 or more to 3 or 4 3 Yes Yes 1 or more to 4 4 Yes Yes 1 or more to 3 5 Yes Yes Yes 2 to 5 6 Yes Yes Yes 1 to 4 7 Yes Yes Yes Yes 2 or 3 to 5

[0062] It is difficult to make a general statement about the number of years an out-of-service, internal inspection can be extended because it is heavily dependent on the results of the floor thickness estimates. Obviously, a tank floor that has a low rate of corrosion and greatly exceeds the minimum thickness will have a longer extension time than one that is experiencing a high rate of corrosion and is barely meeting the minimum thickness standard. Since all of the measurements made are trying to estimate the condition of the tank from limited data (as compared to a full, out-of-service, internal inspection, it is important to consider the degree of confidence in the spatial estimate of corrosion.

[0063] Table 7 illustrates the range of Extension Time Intervals that might be expected for various methods of the current invention for low to moderate corrosion rates. A more detail estimate for 203 implementations is illustrated below. If the rate of corrosion is high, then the Extension Time Interval would be shorted than those proposed in Table 2.

TABLE-US-00008 TABLE 7 In-Service Tank Inspection Method for Prioritizing Out-of-Service Inspections for Low to Moderate Corrosion Rates Unless Otherwise Specified 3.sup.rd Party UT Extension Approved Thickness API 653/ AE Corro- Time Inspection Leak Detec- at One STI sion/Leak Interval Method tion Test Location* SP001* Detection (Years) 1 Pass 1 2 Pass Floor > 2 0.1 in. 3a Pass A, B, C, 4 or 5** FU1/2 3b Pass D, FU3 1 or 2** 4 Pass >0.1 in. 2 or 3** 5 Pass >0.1 in. Floor > 4 or 5** 0.1 in. 6a Pass >0.1 in. A, B, C, 4 or 5** FU1/2 7a Pass >0.1 in. Floor > A, B, C, 5 0.1 in. FU1/2 6b Pass >0.1 in. D, FU3 1 or 2** 7b Pass >0.1 in. Floor > D, FU3 2** 0.1 in. 5 Pass >0.1 in. E, FU4 0 6 Pass >0.1 in. Floor > E, FU4 1 0.1 in. *Thickness if forecast out to Extension Time Interval based on max corrosion Rate **Use the longer year extension if all thickness measurements are safely greater than 0.1 in.

[0064] As noted above, the AE test results are reported as either A through E or FU1 through FU4, where E and FU4 are expected to have significant damage, need significant repair, and have a high probability of leaking. A grade of C means no damage or repair required, but some maintenance is needed. A grade of FU3 has more damage than C, but is not likely to be leaking.

[0065] The proposed method and apparatuses of the present invention are best used as part of a risk-based inspection procedure, where these measurements can provide a substantive basis for risk mitigation.

[0066] The method of the present invention for estimating the Extension Time Interval is based on a Bayesian statistical analysis. There are a variety of probability hypothesis statements that can be made that are essentially equivalent. One example is: “What's the probability that that there is adequate thickness in the floor of a tank to extend the time between inspections (a given time interval) given that we have conducted and passed a leak detection test?” If we assume that adequate floor thickness is 0.1 in. (0.05 in. for tanks with secondary containment), we can state this probability statement as, “What's the probability that that the thickness in the floor of a tank is greater than 0.1 in. (0.05 in.) so that the time between inspections can be extended (a given time interval) given that we have conducted and passed a leak detection test?” Another way of stating the hypothesis is “What's the probability that that the time between inspections (a given time interval) given that we have conducted and passed a leak detection test and there is adequate thickness in the floor of a tank?” In line with the assumption above, this hypothesis can be stated as “What's the probability that that the time between inspections (a given time interval) given that we have conducted and passed a leak detection test and the thickness of the floor of a tank is greater than 0.01 in. (0.05 in.)?” All of these statements can be made more complex by adding additional a priori information. For example, “What's the probability that that the time between inspections (a given time interval) given that (1) we have conducted and passed a leak detection test, (2) there is adequate thickness in the floor of a tank, and (3) the corrosion of the tank floor is low?,” or GIVEN that (1), (2), (3), and (4) . . . (n). We can also expand (2) to include additional sensors like those illustrated below in (2a) through (2e). We can add a minimum acceptable floor thickness in (3) like 0.1 in. (0.05 in. for secondarily contained tanks). We can also add state conditions like (4) low corrosion rates, (5) consistency between methods and data collected. [0067] (2a) Local UT thickness measurements, [0068] (2b) Previous Out-of-Service Floor Thickness Measurements over the nominal thickness at the Initial Installation, [0069] (2c) Previous Out-of-Service Floor Thickness Measurements over Previous Out-of-Service Inspection, [0070] (2d) An AE Corrosion Activity Measurement and a Previous Out-of-Service Inspection, [0071] (2e) An AE Corrosion Activity Measurement where the corrosion rate throughout the tank is low and the previous evaluation of the floor thickness throughout the entire tank floor is more than adequate (i.e., >> the minimum acceptable thickness (e.g., close to the original thickness of the tank floor).

[0072] The probability hypothesis can be very complicated. The heart of the Extension Time Interval is a Passing Leak Detection Test and an estimate of the minimum thickness of the tank floor that exceeds 0.1 in. (or 0.05 in.) throughout the extension period. There is a level of uncertainty on this thickness estimate depending on the number of sensors, when the in-tank measurements were made, and what the spatial distribution of the floor thickness is. Thus, a tank with hot spots or local areas of high corrosion would have a shorter Extension Time Interval than a tank with uniform corrosion, knowledge of the spatial distribution of floor thickness, and an up-to-date estimate of floor thickness. It is because of this uncertainty that longer Extension Time Intervals than 4 or 5 years is not recommended.

[0073] For the preferred method of the present invention, the probability hypothesis would be, “What's the probability that that the thickness in the floor of a tank is greater than 0.1 in. (0.05 in.) so that the time between inspections can be extended a certain time interval (to be specified as a function of the sensor measurements and sensor measurement results) given that (1) we have conducted and passed a leak detection test, (2) we have made several measurements of the local tank floor thickness, (3) we have made an estimate of the spatial distribution of floor thickness and corrosion rate with one or more methods, (4) the thickness and rate of corrosion are Low, Moderate, or High, (5) the floor thickness estimates are correlated and consistent with each other, and (6) the most current in-tank measurements of floor thickness (e.g., a UT sensor) or corrosion activity (e.g., an AE system) and whether or not the thickness and/or corrosion rate/activity are correlated with, consistent with, and/or smaller than the estimates made during previous out-of-service inspection?” For simplicity, we can start with only tanks that have Passed a Leak Detection Test and will result in a minimum floor thickness that is adequate or greater than 0.1 in. We can further combine the thickness measurements (items (2) and (3) from the results of the measurement (items (4)-(6)).

[0074] As stated above, we can break the probability statement into many parts as a complex statement, or simply combine it into a succinct statement as presented in the illustration below. Typically, one would assign a probability to Bayes Theorem, but one can also use a Confidence Level (from 0 to 10) to describe the Method and Results, and then associate an Extension Time Interval (0 to 5 Years) with each Confidence Level. This is described below.

[0075] A simple illustration of the application of this method is presented below. The following hypothesis is tested. What's the probability that the thickness in the floor of a tank is of adequate thickness (i.e., greater than 0.1 (or 0.05 in. for tanks that are secondarily contained)) so that the time interval between inspections can to be safely extended by a certain time interval GIVEN that the tank passes a leak detection test.” We consider a Passing Test with third-party evaluated LD Test Method with a P.sub.D≥95% and P.sub.FA≤5%. A Passing Test indicates that there is a high probability that there are no holes in the tank floor or no holes in the tank floor that are large enough to actually leak due to debris closing the hole or no holes in the tank floor that detected as leaking. For purposes of this illustration, we consider the five different measurement of floor thickness described above in (2a) through (2e) that will support the notion of adequate floor thickness or some pre-determined minimum, desirable floor thickness, i.e., P(W). For this illustration, P(W) incorporates the thickness inferences from one or more of the measurement methods of the present invention. For this illustration, we will assume 0.1 in. (and 0.05 in.).

[0076] Mathematically, Bayes' theorem gives the relationship between the probabilities of W and Q, P(W) and P(Q), and the conditional probabilities of Q given W and W given Q, P(Q|W) and P(W|Q). In its most common form, it is:

[00001]$P\left(W\text{/}Q\right)=\frac{P\left(Q\text{/}W\right)P\left(W\right)}{P\left(Q\right)}$

where this probability statement can also be expressed as

[00002]$P\left(W\text{/}Q\right)=\frac{P\left(Q\text{/}W\right)P\left(W\right)}{P\left(Q\text{/}W\right)P\left(W\right)+P\left(Q\text{/}M\right)P\left(M\right)}$$\mathrm{or}$$P\left(W\text{/}Q\right)=\frac{P\left(Q\text{/}W>a\right)P\left(W>a\right)}{P\left(Q\text{/}W>0\right)P\left(W>a\right)+P\left(Q\text{/}W<a\right)P\left(M<a\right)}$

where
W=adequate floor thickness or FT>a, where “a” may be 0.0 in. or 0.1 or 0.05 in. or some acceptable thickness, which is estimated from one or more of the five current and previous measurements of the tank floor thickness or tank floor corrosion for this illustration.
Q=Pass a leak detection test with a known P.sub.D, LR, and P.sub.FA
P(Q) is the probability of Passing a Leak Detection Test. We normally define P(Q) for a Leak Rate (i.e., Hole Size) and perform the test such that the probability of detection of a leak of a certain size is at least 95%. If the LR is smaller than the smallest hole that will leak, then this become the P(Q) for all leak rates. If not, then it is possible that a leak may still exist and be too small to detect with a high reliability. Also, a leak of a detectable size can be missed to because of the statistic nature of the test.
P(W)=Probability that the floor is of adequate thickness to extend the time interval between tests.
P(W/Q)=Probability that floor is of adequate thickness to extend the time interval between tests given that a Passing Leak Detection Test.
P(Q/W)=Probability of Passing a Leak Detection test given that the floor has adequate thickness.

[00003]$P\left(Q\text{/}W>a\right)P\left(W>a\right)+P\left(Q\text{/}W<a\right)P\left(W<a\right)$$\begin{array}{c}P\left(W\text{/}Q\right)=\frac{P\left(Q\text{/}W>a\right)P\left(W>a\right)}{P\left(Q\text{/}W>a\right)P\left(W>a\right)+P\left(Q\text{/}W<a\right)P\left(W<a\right)}\\ =\frac{\left(95\%\right)\left(80\%\right)}{\left(95\%\right)\left(80\%\right)+\left(5\%\right)\left(20\%\right)}=98.7\%\end{array}$

where the test was originally conducted with a probability of passing of 95%. While 95% is very good, 98.7% is even better. The added reliability is provided by the a priori information about the expectations of conducting a test with information about the tank thickness. We have assumed the application of different measurement systems and incorporate one type of result, i.e., whether or not the measured corrosion rate is high or low.

[0077] Tables 8 and 9 below illustrate some results for different methods of the present invention. These results present the likelihood of a tank not failing or not leaking. We assume that a probability of 95% or 99% is generally acceptable to justify extending the time interval between inspections. The 99% probabilities are designated in red font and the 95% probabilities are designate in blue font. The 90% probabilities are deemed questionable and are highlighted in yellow. The 90% probabilities designate the maximum extension time that might be considered. More measurement data, such as spatial floor thickness data, would be required to justify an extension. Table 8 is for low corrosion rates, and Table 9 is for high corrosion rates. One can see that the time between inspections can be longer for tanks with low corrosion vice tanks with high corrosion rates.

TABLE-US-00009 TABLE 8 Illustration of the Number of Years that an Internal Inspection can be Extended for Methods where All of the Sensors Indicate Low Corrosion and More than Adequate Floor Thickness at the End of the Inspection Interval Extension Methods Low CR Probability of Extension Low Corrosion Activity with More than Adequate Thickness Number of Time Interval - Years Decision for Each Sensor Sensors/Tests 1 2 3 4 5 in Years Leak Detection Pass* 1 95.0% 70.0% 60.0% 50.0% 50.0% 1 Leak Detection Pass & Local UT Floor Thickness 2 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Leak Detection Pass & Previous Internal 2 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Floor Thickness Inspection Leak Detection Pass & AE Corrosion Activity 2 99.0% 95.0% 90.0% 80.0% 70.0% 2 to 3 Leak Detection Pass & Local UT & Previous 3 99.0% 99.0% 99.0% 95.0% 90.0% 4 to 5 Internal Floor Thickness Inspections Leak Detection Pass & Local UT & AE Corrosion Activity 3 99.0% 99.0% 95.0% 90.0% 90.0% 3 to 4 Leak Detection Pass & Local UT & Previous 4 99.0% 99.0% 99.0% 99.0% 99.0% 5 Internal & AE Corrosion Activity *Assumes some risk/probabilitic information about the tanks, tank history, and environment exist

TABLE-US-00010 TABLE 9 Illustration of the Number of Years that an Internal Inspection can be Extended for Methods where All of the Sensors Indicate High Corrosion and Minimum Floor Thickness at the End of the Inspection Interval Extension Methods High CR Probability of Extension High Corrosion Activity that has Minimum Thickness for Number of Time Interval - Years Decision Each Sensor Sensors/Tests 1 2 3 4 5 in Years Leak Detection Pass* 1 95.0% 70.0% 60.0% 50.0% 50.0% 1 Leak Detection Pass & Local UT Floor Thickness 2 99.0% 90.0% 70.0% 60.0% 50.0% 1 to 2 Leak Detection Pass & Previous Internal 2 99.0% 90.0% 80.0% 80.0% 70.0% 1 to 2 Floor Thickness Inspection Leak Detection Pass & AE Corrosion Activity 2 95.0% 90.0% 80.0% 70.0% 60.0% 1 to 2 Leak Detection Pass & Local UT & Previous 3 99.0% 95.0% 90.0% 70.0% 60.0% 2 to 3 Internal Floor Thickness Inspections Leak Detection Pass & Local UT & AE Corrosion Activity 3 99.0% 90.0% 70.0% 60.0% 50.0% 1 to 2 Leak Detection Pass & Local UT & Previous 4 99.0% 95.0% 90.0% 80.0% 70.0% 2 to 3 Internal & AE Corrosion Activity *Assumes some risk/probabilitic information about the tanks, tank history, and environment exist

[0078] Powerful statements can be made depending on the type and the results of the Leak Detection and the Thickness Measurements. As described above, the study of the use of AE for determining the corrosion activity across the tank floor has generated some interesting statistics about the integrity status of the tank. The studies suggest that about ⅔ of the tanks studied are in really good shape and do not need maintenance or repair. Stated another way 2 out of 3 tanks are in good shape. Thus, this type of information can be taken into account when establishing the probabilities in Tables 8 and 9 and is the reason the probabilities did not drop below 50%.

[0079] A risk-based inspection needs to estimate both the likelihood of a failure and the consequence of the failure. We have made an estimate of the likelihood of that the tank will not leak and that the thickness of the tank floor will maintain a certain minimum thickness (0.1 in. or 0.05 in.) over the Extension Time Interval given that a certain suite of sensor measurement systems were used to generate the data as input to the decision making models and given that certain results were obtained with this sensor suite. If this assessment is inaccurate, then the tank may leak and/or the floor may corrode more than desired. The consequence of an inaccurate decision is the cost of characterizing and remediating the leak, the cost of repairing the tank floor, and the cost of lost operations while the tank is out of service. This latter can be the most significant cost and in a small facility where only 1 or 2 tanks can be used to store a specific type of product, the cost of lost operations can be even more significant. In addition to actual cost, there is a public image issue and potential health hazards. While there is a consequence to having an incident during the Extension Time Interval, there is also a cost to prematurely scheduling an internal inspection where none is required. There is no need to remove a tank from service for maintenance and/or repair when it is not needed. There is no need to lose operational services during this period. In fact, this often leads to more problems because an inspection may not be performed on a tank that really needs one because the decision making process is lacking information. Thus, there are multiple consequences, one for inspecting a tank when it is not really required, another for not inspecting a tank when it would benefit from the inspection, and final one for extending the time between inspections too long, allowing the possibility of an incident to occur. The former is not usually considered and should be, because it is a real expenditure of funds, funds that could be better used on tanks that could benefit more. The proposed method of the present invention helps prioritize and manage tank maintenance and repair operations. It allows the best use of available funds to maintain the tanks in a facility in the best operational shape.

[0080] The cost of performing an inspection can be estimated reasonably well. This is also true of the cost of lost operations. The cost of characterizing and remediating a leak is not as easy to estimate and is dependent on the size of the leak and the environmental and health damage resulting from the leak; the cost of lost operations is then a direct function of how long this takes to characterize and remediate the leak. The other costs (e.g., dealing with the public) are equally uncertain and depend up the severity of the incident. The probability of a large leak or a structural failure is relatively small and should be taken into account when estimating the consequence of a problem. Thus, if there is a probability of 3% of the tanks leaking in a facility and the estimated cost of to correct an incident is $3 M, the actual consequence is 3% of $3 M, or $90,000. In general, the cost saving of each inspection dwarfs this consequence cost (e.g., $300,000). While the cost of an incident can be an order of magnitude larger than an inspection if an incident occurs, the probability is low and for facilities with secondary containment, the consequences and the costs are even lower. Estimating the probability of a leak is difficult, and if it is unrealistically large or not taken into account at all (e.g., assuming a probability of a leak of 100%), then it can seriously bias the inspection process and increase the overall costs and increase the chance of an incident. Regardless, it is clear from any reasonable estimate that the consequences of not prioritizing and managing optimally will outweigh the consequence of a leak.

[0081] In its simplest application, we can assume the consequences apply equally for all tanks and all extension time intervals. This is probably a reasonable approach if the sensor suite used in the assessment is adequate and includes a passing leak detection test with a reliable method, an in-tank measurement of floor thickness and corrosion rate, and information about the spatial characteristics of the tank floor. If not, one can increase the probability of a leak as a function of the Extension Time Interval, i.e., the longer Extension Time, the higher the probability of a leak. Other things may increase the probability of a leak. For example, the probability may also be higher for tanks with a high rate of corrosion and the floor thickness forecast. In general, if the sensor suite is adequate and the minimum acceptable floor thickness of 0.1 in. (or 0.05 in. for secondarily contained tanks), then the probability of a leak is about the same for all tanks.

[0082] Table 10 illustrates the decision making process. If the probability of successfully extending the time interval 5 years between inspections is 95%, the present value of the cost savings of a $300,000 internal inspection is $366,314. If the probability of a leak is 3% for a method with a 99% probability of success, and the probability increases as the probability of success decreases, we can compare the cost savings to the cost. If the cost consequence of a leak exceeds the cost savings, then the method should not be used to extend the time interval. This model increases the probability of a leak for all method probabilities less than 95% by 1.25. Thus, the probability of a leak for a method with a 50% confidence level in the method, the probability of a leak to use in the computation is 1.25 times 6% (1.25*3%/(100%−50%)=7.5%).

[0083] In general, the decision about extension is best made assuming a confidence level of 99% or 95%, and it is assumed that the consequence for using a lesser method to base the extension period is too low to accept.

TABLE-US-00011 TABLE 13 Summary of Confidence Levels on Different Methods and the Recommended Extension Times Overall Confidence of Extension Time Integrity Assessment Interval (Years) 0 0 1 0 2 1 3 2 4 2 5 2 6 3 7 3 8 4 9 5 10 5

[0084] Tables 11 and 12 summarize a more comprehensive list of various types of Methods and the various types of types of Test Results to illustrate the methods summarized in Table 6 and Table 7, respectively. All of the methods assume that they have Passed a Leak Detection Test. Furthermore, all of the preferred methods have a high probability that the floor thickness will be greater than 0.1 in., or some acceptable minimum floor thickness, and that the corrosion rate is low to moderate, but not high, because of one or more in-tank floor measurements. The Extension Time Interval, described above in terms of Bayesian statistics is selected on the basis of a Confidence Interval that the method will achieve a 95% or 99% probability of not leaking or structurally failing during the Extension Time Interval. In general, the probability is 99%, except where two or more levels of confidence are expressed and the lower probability is assigned. Table 13 summarizes the Confidence Levels estimated for each method and the Extension Time Interval in years.

[0085] The Confidence Intervals were assessed in terms of Low, Moderate, and High rates of corrosion rates for the local UT thickness measurements, the previous Out-of-Service Floor Thickness Measurements, and the AE corrosion activity, whether or not the minimum thickness of the tank floor will be exceeded before the Extension Time Interval as assessed by the UT local measurements and the previous Out-of-Service floor inspection measurements, whether or not the UT measurements are correlated and are consistent with these three floor thickness and/or corrosion measurements, whether or not the UT local thickness and corrosion rate measurements are smaller/larger than the Out-of-Service floor thickness and corrosion rate measurements, and whether or not the leak detection results of the AE system are consistent with the results of the Leak Detection test.

[0086] In general, almost all of the various methods include local in-tank measurements of the floor thickness so that an estimate of the maximum general or uniform corrosion rate and minimum floor thickness can be determined for the whole tank and to use it in estimating the spatial distribution of the corrosion rate and floor thickness if the floor corrodes evenly. The local measurement of floor thickness is very powerful, because it is a direct indication of the floor thickness made at the time in which the extension time interval is made.

[0087] As illustrated in Tables 7 and 8 and 11 and 12, the Methods that permit greater than a 1-year extension all include a Leak Detection Test and at least one other in-tank measurement of the tank floor thickness. A 1-year extension is permitted if only a Leak Detection Test is Passed with an EPA-approved test method providing the corrosion activity of the tank is known to be Low. Given the ease and low incremental cost of making one- or more local measurements of the floor thickness with an in-tank UT sensor, it is unlikely that only a Leak Detection Test will be performed. Thus, it is easy to verify the corrosion activity for a 1-year extension and with adequate floor thickness, more than a 1-year extension is possible. The Methods that permit the longest extension times all include measurements that allow a quantitative estimate of the spatial distribution of corrosion potential of the floor. Up to 5 years is possible.

[0088] Table 14 sorts the methods in Table 11 so that the methods with the highest Confidence Intervals and the longest Extension Time Intervals are at the top of the table. Table 15 summarizes a composite interpretation of the Extension Methods. The Extension Time Intervals with the longest extension times involves the use of multiple sensor measurements and low to moderate corrosion rates. All the methods illustrated here have required that the floor thickness at the end of the Extension Time Interval meet the 0.1 in. or 0.05 in. minimum thickness. This does not need to be the case, but it is for all of the illustrated methods because it gives a high level of confidence. It is important to note that unless the tank is taken out-of-service and a full inspection like the ones following API 653, API 12R, or STI SP001, the thickness estimated using the methods of the present invention are all estimates without complete information of the actual spatial distribution of floor thickness.

[0089] The number of methods and the summary of the methods is presented in Table 15. The methods with the longest Extension Time involve the use of a “Passing” Leak Detection Test and at least 2 other measurements of floor thickness, where one of those measurements is almost always a local floor thickness measurement with a UT sensor (i.e., 2 to 5 years). The longest Extension Times occur for the tanks with the lowest rates of corrosion (and highest floor thickness). While it would be preferred that the local UT measurements of floor thickness be correlated and consistent with and lower than the previous API 653 inspection, the results do not support this premise. However, the results indicate that such correlation and consistency is required when using the AE corrosion activity method, because actual measurements of floor thickness are not made. For each Extension Time Interval, there is generally two levels of confidence. Methods with the highest level of confidence are preferred. The higher level of confidence is generally associated with the lower rates of corrosion.

TABLE-US-00012 TABLE 15 Summary of the Extension Time Interval and Confidence Level for 203 Different Measurement Methods and Test Results Methods Methods Methods Methods UT Local API 653 4 Sensors 4 Sensors 4 Sensors 4 Sensors Leak Measurement Tank Floor (1 LD + 3 (1 LD + 2 (1 LD + 1 (1 LD + 0 Number of % of Detection Corrosion Thickness Floor) Floor) Floor) Floor) Methods Methods Method Rate Corrosion Rate 65.0% 35.0% 0.0% 0.0% 20 9.9% PASS Low, >,< Low, Moderate Moderate 63.2% 36.8% 0.0% 0.0% 19 9.4% PASS Low, >,< Low, Moderate Moderate 77.3% 22.7% 0.0% 0.0% 44 21.7% PASS Low, >,< Low, Moderate Moderate 65.2% 26.1% 8.7% 0.0% 69 34.0% PASS Low, >,< Low, Moderate, Moderate, High High 52.6% 42.1% 5.3% 0.0% 19 9.4% PASS Moderate, >,< Moderate, High High 59.4% 21.9% 9.4% 9.4% 32 15.8% PASS Moderate, >,< Moderate, High High UT Local UT Min API 653 Min Extension Methods Correlated UT Local AE Thick- Thick- Overall Time Interval 4 Sensors with API 653 AE Correlated Correlated ness >0.1, ness >0.1, Confidence (Years) UT > (1 LD + 3 Corrosion Corrosion with AE Leak 0.05 in. 0.05 in. of Integrity OOSI &/OR Floor) Rate Activity Corrosion Detection Over ETI Over ETI Assessment AE PASS 65.0% No, Yes Low, Yes Yes Yes Yes  9, 10 5 Moderate 63.2% No, Yes Low, Yes, Some Yes Yes Yes 8 4 Moderate No 77.3% No, Yes Low, Yes, Some Yes, Some Yes Yes, Some 6, 7 3 Moderate No No No 65.2% No, Yes Low, Yes, Some Yes, Some Yes Yes, Some 3, 4 2 Moderate, No No No High 52.6% No, Yes Moderate, Yes Yes Yes Yes 2, 3 1 High 59.4% No, Yes High Yes, Some Yes, Some Yes Yes, Some 0, 1 0 No No No

[0090] About 20% (19.3%) of the methods illustrating the present invention would permit an Extension Time Interval of 4 or 5 years, and about 16% (15.8%) would not permit any extension and require an out-of-service inspection. About 55% (55.7%) of the methods would permit a 2- or 3-year extension with 10% (9.4%) allowing only a 1-year extension. Thus, 75% (74.8%) of the methods illustrating the present invention would allow a 2 to 5 year extension in the time interval between out-of-service inspections.

[0091] The methods and apparatuses of the present invention can include other measurement sensors and different combinations of such sensors. For example, a long range ultrasonic test (LRUT) might be used on the outside shell of the tank vice a previous out-of-service inspection or an AE corrosion activity measurement. In contrast to these two methods, this type of LRUT measurement only measures the tank floor condition in the outter 1.2 m or so of the tank floor, but this LRUT measurement is a measurement of floor thickness and the current floor thickness, where the other methods are not. Also, this LRUT measurement also measures the floor thickness in the area where the tank floor is likely to corrode the most. The confidence levels and the Extension Time Intervals would then change if this LRUT method were to replace the out-of-service inspection or the AE corrosion method. The preferred method of the present invention is comprised of a compact, in-tank set of measurements.

TABLE-US-00013 TABLE 11 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections API 653 UT Local UT AE API 653 Overall Extension UT Local Tank Corre- Local Corre- UT Min Min Confidence Time Measure- Floor lated with Corre- lated Thick- Thick- of Interval Leak ment Thickness API 653 AE lated Leak ness >0.1, ness >0.1, Integrity (Years) Detection Corrosion Corrosion Corrosion Corrosion with AE Detec- 0.05 in. 0.05 in. Assess- UT > OOSI &/ Method Method Rate Rate Rate Activity Corrosion tion Over ETI Over ETI ment OR AE PASS Method 0 - Leak Detection Only PASS 2 1 FAIL 0 0 Method 1 - Leak Detection and Previous Out-of-Service Floor Inspection PASS Low Yes 5 2 PASS Low No 0 0 PASS Moderate Yes 4 2 PASS Moderate No 0 0 PASS High Yes 4 2 PASS High No 0 0 Method 2 - Leak Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness  1 PASS Low Yes 5 2  2 PASS Low No 0 0  3 PASS Moderate Yes 4 2  4 PASS Moderate No 0 0  5 PASS High Yes 3 2  6 PASS High No 0 0 Method 3 - Leak Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness  1 PASS Low > Low Yes Yes Yes 9 5  2 PASS Low > Low No Yes Yes 8 4  3 PASS Moderate > Low No Yes Yes 8 4  4 PASS Moderate > Moderate Yes Yes Yes 9 5  5 PASS Moderate > Moderate No Yes No 7 3  6 PASS Moderate > High Yes Yes Yes 7 3  7 PASS Moderate > High No Yes No 2 1  8 PASS High > Moderate Yes Yes Yes 5 2  9 PASS High > Moderate No Yes No 2 1 10 PASS High > High Yes Yes Yes 5 2 11 PASS High > High No Yes No 1 0 Method 4 - Leak-Detection, UT Local Floor Thickness, and Previous Out-of-Service Floor Thickness  1 PASS Low < Low Yes Yes Yes 10 5  2 PASS Low ,<  Low No Yes Yes 9 5  3 PASS Moderate < Low No Yes Yes 9 5  4 PASS Moderate < Moderate Yes Yes Yes 10 5  5 PASS Moderate < Moderate No Yes No 8 4  6 PASS Moderate < High Yes Yes Yes 8 4  7 PASS Moderate ,<  High No Yes No 3 2  8 PASS High < Moderate Yes Yes Yes 6 3  9 PASS High < Moderate No Yes No 3 2 10 PASS High < High Yes Yes Yes 6 3 11 PASS High < High No Yes No 2 1 Method 5 - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity   A PASS Low Low Yes Yes Yes 9 5   B PASS Low Moderate Yes Yes Yes 8 4   C PASS Low High Yes Yes Yes 5 2   D PASS Moderate Low Yes Yes Yes 8 4   E PASS Moderate Moderate Yes Yes Yes 8 4   F PASS Moderate High Yes Yes Yes 5 2   G PASS High Low Yes Yes Yes 7 3   H PASS High Moderate Yes Yes Yes 5 2   I PASS High High Yes Yes Yes 2 1 Method 6 - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity   J PASS Low Low No Yes Yes 7 3   K PASS Low Moderate No Yes Yes 6 3   L PASS Low High No Yes Yes 3 2   M PASS Moderate Low No Yes Yes 6 3   N PASS Moderate Moderate No Yes Yes 6 3   O PASS Moderate High No Yes Yes 3 2   P PASS High Low No Yes Yes 5 2   Q PASS High Moderate No Yes Yes 3 2   R PASS High High No Yes Yes 0 0 Method 5a - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity   A PASS Low Low Yes No Yes 6 3   B PASS Low Moderate Yes No Yes 5 2   C PASS Low High Yes No Yes 2 1   D PASS Moderate Low Yes No Yes 5 2   E PASS Moderate Moderate Yes No Yes 5 2   F PASS Moderate High Yes No Yes 2 1   G PASS High Low Yes No Yes 4 2   H PASS High Moderate Yes No Yes 2 1   I PASS High High Yes No Yes 0 0 Method 6a - Leak Detection, UT Local Floor Thickness, and AE Corrosion Activity   J PASS Low Low No No Yes 4 2   K PASS Low Moderate No No Yes 3 2   L PASS Low High No No Yes 0 0   M PASS Moderate Low No No Yes 3 2   N PASS Moderate Moderate No No Yes 3 2   O PASS Moderate High No No Yes 0 0   P PASS High Low No No Yes 2 1   Q PASS High Moderate No No Yes 0 0   R PASS High High No No Yes 0 0 Method 7 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity  1 A PASS Low > Low Yes Low Yes Yes Yes Yes 10 5  1 B PASS Low > Low Yes Moderate Yes Yes Yes Yes 9 5  1 C PASS Low > Low Yes High Yes Yes Yes Yes 5 2  2 A PASS Low > Low No Low Yes Yes Yes Yes 9 5  2 B PASS Low > Low No Moderate Yes Yes Yes Yes 8 4  2 C PASS Low > Low No High Yes Yes Yes Yes 4 2  3 D PASS Moderate > Low No Low Yes Yes Yes Yes 8 4  3 E PASS Moderate > Low No Moderate Yes Yes Yes Yes 7 3  3 F PASS Moderate > Low No High Yes Yes Yes Yes 3 2  4 D PASS Moderate > Moderate Yes Low Yes Yes Yes Yes 9 5  4 E PASS Moderate > Moderate Yes Moderate Yes Yes Yes Yes 8 4  4 F PASS Moderate > Moderate Yes High Yes Yes Yes Yes 4 2  5 D PASS Moderate > Moderate No Low Yes Yes Yes No 8 4  5 E PASS Moderate > Moderate No Moderate Yes Yes Yes No 7 3  5 F PASS Moderate > Moderate No High Yes Yes Yes No 3 2  6 G PASS Moderate > High Yes Low Yes No Yes Yes 7 3  6 H PASS Moderate > High Yes Moderate Yes No Yes Yes 6 3  6 F PASS Moderate > High Yes High Yes No Yes Yes 2 1  7 G PASS Moderate > High No Low Yes No Yes No 6 3  7 E PASS Moderate > High No Moderate Yes No Yes No 5 2  7 F PASS Moderate > High No High Yes No Yes No 1 0  8 D PASS High > Moderate Yes Low Yes Yes Yes Yes 7 3  8 E PASS High > Moderate Yes Moderate Yes Yes Yes Yes 6 3  8 F PASS High > Moderate Yes High Yes Yes Yes Yes 2 1  9 D PASS High > Moderate No Low Yes No Yes No 6 3  9 E PASS High > Moderate No Moderate Yes No Yes No 5 2  9 F PASS High > Moderate No High Yes No Yes No 1 0 10 G PASS High > High Yes Low Yes Yes Yes Yes 6 3 10 H PASS High > High Yes Moderate Yes Yes Yes Yes 5 2 10 I PASS High > High Yes High Yes Yes Yes Yes 1 0 11 G PASS High > High No Low Yes Yes Yes No 5 2 11 H PASS High > High No Moderate Yes Yes Yes No 4 2 11 I PASS High > High No High Yes Yes Yes No 0 0 Method 8 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity  1 J PASS Low > Low Yes Low No Yes Yes Yes 8 4  1 K PASS Low > Low Yes Moderate No Yes Yes Yes 7 3  1 L PASS Low > Low Yes High No Yes Yes Yes 3 2  2 J PASS Low > Low No Low No Yes Yes Yes 7 3  2 K PASS Low > Low No Moderate No Yes Yes Yes 6 3  2 L PASS Low > Low No High No Yes Yes Yes 2 1  3 M PASS Moderate > Low No Low No Yes Yes Yes 6 3  3 N PASS Moderate > Low No Moderate No Yes Yes Yes 5 2  3 O PASS Moderate > Low No High No Yes Yes Yes 1 0  4 M PASS Moderate > Moderate Yes Low No Yes Yes Yes 7 3  4 N PASS Moderate > Moderate Yes Moderate No Yes Yes Yes 6 3  4 O PASS Moderate > Moderate Yes High No Yes Yes Yes 2 1  5 M PASS Moderate > Moderate No Low No Yes Yes No 6 3  5 N PASS Moderate > Moderate No Moderate No Yes Yes No 5 2  5 D PASS Moderate < Moderate No Low Yes Yes Yes No 9 5  5 E PASS Moderate ,<  Moderate No Moderate Yes Yes Yes No 8 4  5 F PASS Moderate < Moderate No High Yes Yes Yes No 4 2  6 G PASS Moderate < High Yes Low Yes No Yes Yes 8 4  6 H PASS Moderate < High Yes Moderate Yes No Yes Yes 7 3  6 F PASS Moderate ,<  High Yes High Yes No Yes Yes 3 2  7 G PASS Moderate < High No Low Yes No Yes No 7 3  7 E PASS Moderate ,<  High No Moderate Yes No Yes No 6 3  7 F PASS Moderate < High No High Yes No Yes No 2 1  8 D PASS High < Moderate Yes Low Yes Yes Yes Yes 8 4  8 E PASS High < Moderate Yes Moderate Yes Yes Yes Yes 7 3  8 F PASS High ,<  Moderate Yes High Yes Yes Yes Yes 3 2  9 D PASS High < Moderate No Low Yes No Yes No 7 3  9 E PASS High ,<  Moderate No Moderate Yes No Yes No 6 3  9 F PASS High < Moderate No High Yes No Yes No 2 1 10 G PASS High < High Yes Low Yes Yes Yes Yes 7 3 10 H PASS High < High Yes Moderate Yes Yes Yes Yes 6 3 10 I PASS High ,<  High Yes High Yes Yes Yes Yes 2 1 11 G PASS High < High No Low Yes Yes Yes No 6 3 11 H PASS High ,<  High No Moderate Yes Yes Yes No 5 2 11 I PASS High < High No High Yes Yes Yes No 1 0 Method 9 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity  1 A PASS Low < Low Yes Low Yes Yes Yes Yes 10 5  1 B PASS Low ,<  Low Yes Moderate Yes Yes Yes Yes 10 5  1 C PASS Low < Low Yes High Yes Yes Yes Yes 6 3  2 A PASS Low < Low No Low Yes Yes Yes Yes 10 5  2 B PASS Low < Low No Moderate Yes Yes Yes Yes 9 5  2 C PASS Low ,<  Low No High Yes Yes Yes Yes 5 2  3 D PASS Moderate < Low No Low Yes Yes Yes Yes 9 5  3 E PASS Moderate ,<  Low No Moderate Yes Yes Yes Yes 8 4  3 F PASS Moderate < Low No High Yes Yes Yes Yes 4 2  4 D PASS Moderate < Moderate Yes Low Yes Yes Yes Yes 10 5  4 E PASS Moderate < Moderate Yes Moderate Yes Yes Yes Yes 9 5  4 F PASS Moderate ,<  Moderate Yes High Yes Yes Yes Yes 5 2  5 D PASS Moderate < Moderate No Low Yes Yes Yes No 9 5  5 E PASS Moderate ,<  Moderate No Moderate Yes Yes Yes No 8 4  5 F PASS Moderate < Moderate No High Yes Yes Yes No 4 2  6 G PASS Moderate < High Yes Low Yes No Yes Yes 8 4  6 H PASS Moderate < High Yes Moderate Yes No Yes Yes 7 3  6 F PASS Moderate ,<  High Yes High Yes No Yes Yes 3 2  7 G PASS Moderate < High No Low Yes No Yes No 7 3  7 E PASS Moderate ,<  High No Moderate Yes No Yes No 6 3  7 F PASS Moderate < High No High Yes No Yes No 2 1  8 D PASS High < Moderate Yes Low Yes Yes Yes Yes 8 4  8 E PASS High < Moderate Yes Moderate Yes Yes Yes Yes 7 3  8 F PASS High ,<  Moderate Yes High Yes Yes Yes Yes 3 2  9 D PASS High < Moderate No Low Yes No Yes No 7 3  9 E PASS High ,<  Moderate No Moderate Yes No Yes No 6 3  9 F PASS High < Moderate No High Yes No Yes No 2 1 10 G PASS High < High Yes Low Yes Yes Yes Yes 7 3 10 H PASS High < High Yes Moderate Yes Yes Yes Yes 6 3 10 I PASS High ,<  High Yes High Yes Yes Yes Yes 2 1 11 G PASS High < High No Low Yes Yes Yes No 6 3 11 H PASS High ,<  High No Moderate Yes Yes Yes No 5 2 11 I PASS High < High No High Yes Yes Yes No 1 0 Method 10 - Leak Detection, UT Local Floor Thickness, Previous Out-of-Service Floor Thickness, and AE Corrosion Activity  1 J PASS Low < Low Yes Low No Yes Yes Yes 9 5  1 K PASS Low ,<  Low Yes Moderate No Yes Yes Yes 8 4  1 L PASS Low < Low Yes High No Yes Yes Yes 4 2  2 J PASS Low < Low No Low No Yes Yes Yes 8 4  2 K PASS Low < Low No Moderate No Yes Yes Yes 7 3  2 L PASS Low ,<  Low No High No Yes Yes Yes 3 2  3 M PASS Moderate < Low No Low No Yes Yes Yes 7 3  3 N PASS Moderate ,<  Low No Moderate No Yes Yes Yes 6 3  3 O PASS Moderate < Low No High No Yes Yes Yes 2 1  4 M PASS Moderate < Moderate Yes Low No Yes Yes Yes 8 4  4 N PASS Moderate < Moderate Yes Moderate No Yes Yes Yes 7 3  4 O PASS Moderate ,<  Moderate Yes High No Yes Yes Yes 3 2  5 M PASS Moderate < Moderate No Low No Yes Yes No 7 3  5 N PASS Moderate ,<  Moderate No Moderate No Yes Yes No 6 3  5 O PASS Moderate < Moderate No High No Yes Yes No 2 1  6 P PASS Moderate < High Yes Low No No Yes Yes 6 3  6 Q PASS Moderate < High Yes Moderate No No Yes Yes 5 2  6 R PASS Moderate ,<  High Yes High No No Yes Yes 1 0  7 P PASS Moderate < High No Low No No Yes No 5 2  7 Q PASS Moderate ,<  High No Moderate No No Yes No 4 2  7 R PASS Moderate < High No High No No Yes No 1 0  8 M PASS High < Moderate Yes Low No Yes Yes Yes 6 3  8 N PASS High < Moderate Yes Moderate No Yes Yes Yes 5 2  8 O PASS High ,<  Moderate Yes High No Yes Yes Yes 1 0  9 M PASS High < Moderate No Low No No Yes No 5 2  9 N PASS High ,<  Moderate No Moderate No No Yes No 4 2  9 O PASS High < Moderate No High No No Yes No 1 0 10 P PASS High < High Yes Low No Yes Yes Yes 5 2 10 Q PASS High < High Yes Moderate No Yes Yes Yes 4 2 10 R PASS High ,<  High Yes High No Yes Yes Yes 1 0 11 P PASS High < High No Low No Yes Yes No 4 2 11 Q PASS High ,<  High No Moderate No Yes Yes No 3 2 11 R PASS High < High No High No Yes Yes No 1 0

TABLE-US-00014 TABLE 12 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections Extension Extension Extension Extension Time Time Time Time Interval Interval Interval Interval (Years) (Years) (Years) (Years) 2 UT > 2 UT > 3 UT > 4 UT > OOSI & OOSI & OOSI & OOSI & AE Leak AE Leak AE PASS AE Leak Method 7 Method 8 Method 9 Method 10 5 4 5 5 5 3 5 4 2 2 3 2 5 3 5 4 4 3 5 3 2 1 2 2 4 3 5 3 3 2 4 3 2 0 2 1 5 3 5 4 4 3 5 3 2 1 2 2 4 3 5 3 3 2 4 3 2 0 2 1 3 2 4 3 3 2 3 2 1 0 2 0 3 2 3 2 2 2 3 2 0 0 1 0 3 2 4 3 3 2 3 2 1 0 2 0 3 2 3 2 2 2 3 2 0 0 1 0 3 2 3 2 2 2 3 2 0 0 1 0 2 2 3 2 2 1 2 2 0 0 0 0 Number 33 33 33 33 Sum 85 56 103 69 Mean 2.576 1.697 3.121 2.091 Median 3.000 2.000 3.000 2.000 StDev 1.458 1.159 1.409 1.308 Min 0.000 0.000 0.000 0.000 Max 5.000 4.000 5.000 5.000

TABLE-US-00015 TABLE 14 In-Service Tank Inspection Methods for Prioritizing Out-of-Service Inspections API 653 UT Local UT Local Tank Floor Correlated Leak Measurement Thickness with API 653 AE Detection Corrosion Corrosion Corrosion Corrosion Method Method Method Rate Rate Rate Activity Method 4 31  1 PASS Low < Low Yes Method 7 92  1 A PASS Low > Low Yes Low Method 9 180  1 A PASS Low < Low Yes Low Method 9 181  1 B PASS Low ,<  Low Yes Moderate Method 9 184  2 A PASS Low < Low No Low Method 4 34  4 PASS Moderate < Moderate Yes Method 9 192  4 D PASS Moderate < Moderate Yes Low Method 3 19  1 PASS Low > Low Yes Method 4 32  2 PASS Low ,<  Low No Method 7 93  1 B PASS Low > Low Yes Moderate Method 7 96  2 A PASS Low > Low No Low Method 9 185  2 B PASS Low < Low No Moderate Method 10 224  1 J PASS Low < Low Yes Low Method 5 43   A PASS Low Low Method 4 33  3 PASS Moderate < Low No Method 9 188  3 D PASS Moderate < Low No Low Method 3 22  4 PASS Moderate > Moderate Yes Method 7 104  4 D PASS Moderate > Moderate Yes Low Method 9 193  4 E PASS Moderate < Moderate Yes Moderate Method 9 196  5 D PASS Moderate < Moderate No Low Method 3 20  2 PASS Low > Low No Method 7 97  2 B PASS Low > Low No Moderate Method 8 136  1 J PASS Low > Low Yes Low Method 10 225  1 K PASS Low ,<  Low Yes Moderate Method 10 228  2 J PASS Low < Low No Low Method 5 44   B PASS Low Moderate Method 3 21  3 PASS Moderate > Low No Method 7 100  3 D PASS Moderate > Low No Low Method 9 189  3 E PASS Moderate ,<  Low No Moderate Method 4 35  5 PASS Moderate < Moderate No Method 7 105  4 E PASS Moderate > Moderate Yes Moderate Method 7 108  5 D PASS Moderate > Moderate No Low Method 9 197  5 E PASS Moderate ,<  Moderate No Moderate Method 10 236  4 M PASS Moderate < Moderate Yes Low Method 4 36  6 PASS Moderate < High Yes Method 9 200  6 G PASS Moderate < High Yes Low Method 5 47   D PASS Moderate Low Method 5 48   E PASS Moderate Moderate Method 9 208  8 D PASS High < Moderate Yes Low Method 8 137  1 K PASS Low > Low Yes Moderate Method 8 140  2 J PASS Low > Low No Low Method 10 229  2 K PASS Low < Low No Moderate Method 6 55   J PASS Low Low Method 7 101  3 E PASS Moderate > Low No Moderate Method 10 232  3 M PASS Moderate < Low No Low Method 3 23  5 PASS Moderate > Moderate No Method 7 109  5 E PASS Moderate > Moderate No Moderate Method 8 148  4 M PASS Moderate > Moderate Yes Low Method 10 237  4 N PASS Moderate < Moderate Yes Moderate Method 10 240  5 M PASS Moderate < Moderate No Low Method 3 24  6 PASS Moderate > High Yes Method 7 112  6 G PASS Moderate > High Yes Low Method 9 201  6 H PASS Moderate < High Yes Moderate Method 9 204  7 G PASS Moderate < High No Low Method 7 120  8 D PASS High > Moderate Yes Low Method 9 209  8 E PASS High < Moderate Yes Moderate Method 9 212  9 D PASS High < Moderate No Low Method 9 216 10 G PASS High < High Yes Low Method 5 51   G PASS High Low Method 8 141  2 K PASS Low > Low No Moderate Method 9 182  1 C PASS Low < Low Yes High Method 6 56   K PASS Low Moderate Method 5a 67   A PASS Low Low Method 8 144  3 M PASS Moderate > Low No Low Method 10 233  3 N PASS Moderate ,<  Low No Moderate Method 8 149  4 N PASS Moderate > Moderate Yes Moderate Method 8 152  5 M PASS Moderate > Moderate No Low Method 10 241  5 N PASS Moderate ,<  Moderate No Moderate Method 7 113  6 H PASS Moderate > High Yes Moderate Method 7 116  7 G PASS Moderate > High No Low Method 9 205  7 E PASS Moderate ,<  High No Moderate Method 10 244  6 P PASS Moderate < High Yes Low Method 6 59   M PASS Moderate Low Method 6 60   N PASS Moderate Moderate Method 4 38  8 PASS High < Moderate Yes Method 7 121  8 E PASS High > Moderate Yes Moderate Method 7 124  9 D PASS High > Moderate No Low Method 9 213  9 E PASS High ,<  Moderate No Moderate Method 10 252  8 M PASS High < Moderate Yes Low Method 4 40 10 PASS High < High Yes Method 7 128 10 G PASS High > High Yes Low Method 9 217 10 H PASS High < High Yes Moderate Method 9 220 11 G PASS High < High No Low 94  1 C PASS Low > Low Yes High Method 9 186  2 C PASS Low ,<  Low No High Method 1 5 PASS Low Method 5 45   C PASS Low High Method 5a 68   B PASS Low Moderate Method 8 145  3 N PASS Moderate > Low No Moderate Method 8 153  5 N PASS Moderate > Moderate No Moderate Method 9 194  4 F PASS Moderate ,<  Moderate Yes High Method 7 117  7 E PASS Moderate > High No Moderate Method 8 156  6 P PASS Moderate > High Yes Low Method 10 245  6 Q PASS Moderate < High Yes Moderate Method 10 248  7 P PASS Moderate < High No Low Method 5 49   F PASS Moderate High Method 5a 71   D PASS Moderate Low Method 5a 72   E PASS Moderate Moderate Method 3 26  8 PASS High > Moderate Yes Method 7 125  9 E PASS High > Moderate No Moderate Method 8 164  8 M PASS High > Moderate Yes Low Method 10 253  8 N PASS High < Moderate Yes Moderate Method 10 256  9 M PASS High < Moderate No Low Method 3 28 10 PASS High > High Yes Method 7 129 10 H PASS High > High Yes Moderate Method 7 132 11 G PASS High > High No Low Method 9 221 11 H PASS High ,<  High No Moderate Method 10 260 10 P PASS High < High Yes Low Method 5 52   H PASS High Moderate Method 6 63   P PASS High Low Method 2 12  1 PASS Low Method 7 98  2 C PASS Low > Low No High Method 10 226  1 L PASS Low < Low Yes High Method 6a 79   J PASS Low Low Method 9 190  3 F PASS Moderate < Low No High Method 7 106  4 F PASS Moderate > Moderate Yes High Method 9 198  5 F PASS Moderate < Moderate No High Method 8 157  6 O PASS Moderate > High Yes Moderate Method 8 160  7 P PASS Moderate > High No Low Method 10 249  7 O PASS Moderate ,<  High No Moderate Method 1 7 PASS Moderate Method 8 165  8 N PASS High > Moderate Yes Moderate Method 8 168  9 M PASS High > Moderate No Low Method 10 257  9 N PASS High ,<  Moderate No Moderate Method 7 133 11 H PASS High > High No Moderate Method 8 172 10 P PASS High > High Yes Low Method 10 261 10 O PASS High < High Yes Moderate Method 10 264 11 P PASS High < High No Low Method 1 9 PASS High Method 5a 75   G PASS High Low Method 2 14  3 PASS Moderate Method 8 138  1 L PASS Low > Low Yes High Method 10 230  2 L PASS Low ,<  Low No High Method 6 57   L PASS Low High Method 6a 80   K PASS Low Moderate Method 7 102  3 F PASS Moderate > Low No High Method 7 110  5 F PASS Moderate > Moderate No High Method 10 238  4 O PASS Moderate ,<  Moderate Yes High Method 4 37  7 PASS Moderate ,<  High No Method 8 161  7 O PASS Moderate > High No Moderate Method 9 202  6 F PASS Moderate ,<  High Yes High Method 6 61   O PASS Moderate High Method 6a 83   M PASS Moderate Low Method 6a 84   N PASS Moderate Moderate Method 4 99  9 PASS High < Moderate No Method 8 169  9 N PASS High > Moderate No Moderate Method 9 210  8 F PASS High ,<  Moderate Yes High Method 8 173 10 P PASS High > High Yes Moderate Method 8 176 11 P PASS High > High No Low Method 10 265 11 O PASS High ,<  High No Moderate Method 6 64   O PASS High Moderate Method 2 16  5 PASS High Method 8 142  2 L PASS Low > Low No High Method 5a 69   C PASS Low High Method 10 234  3 O PASS Moderate < Low No High Method 8 150  4 O PASS Moderate > Moderate Yes High Method 10 242  5 O PASS Moderate < Moderate No High Method 3 25  7 PASS Moderate > High No Method 7 114  6 F PASS Moderate > High Yes High Method 9 206  7 F PASS Moderate < High No High Method 5a 73   F PASS Moderate High Method 3 27  9 PASS High > Moderate No Method 7 122  8 F PASS High > Moderate Yes High Method 9 214  9 F PASS High < Moderate No High Method 4 41 11 PASS High < High No Method 8 177 11 O PASS High > High No Moderate Method 9 218 10 I PASS High ,<  High Yes High Method 5 53   I PASS High High Method 5a 76   H PASS High Moderate Method 6a 87   P PASS High Low Method 0 2 PASS Method 8 146  3 O PASS Moderate > Low No High Method 8 154  5 O PASS Moderate > Moderate No High Method 7 118  7 F PASS Moderate > High No High Method 10 246  6 R PASS Moderate ,<  High Yes High Method 10 250  7 R PASS Moderate < High No High Method 7 126  9 F PASS High > Moderate No High Method 10 254  8 O PASS High ,<  Moderate Yes High Method 10 258  9 O PASS High < Moderate No High Method 3 29 11 PASS High > High No Method 7 130 10 I PASS High > High Yes High Method 9 222 11 I PASS High < High No High Method 10 262 10 R PASS High ,<  High Yes High Method 10 266 11 R PASS High < High No High Method 1 6 PASS Low Method 6a 81   L PASS Low High Method 8 158  6 R PASS Moderate > High Yes High Method 8 162  7 R PASS Moderate > High No High Method 1 8 PASS Moderate Method 6a 85   O PASS Moderate High Method 8 166  8 O PASS High > Moderate Yes High Method 8 170  9 O PASS High > Moderate No High Method 7 134 11 I PASS High > High No High Method 8 174 10 R PASS High > High Yes High UT Local AE UT Min API 653 Min Overall Extension Time Correlated Correlated Thickness >0.1, Thickness >0.1, Confidence of Interval (Years) with AE Leak 0.05 in. 0.05 in. Integrity UT > OOSI Method Corrosion Detection Over ETI Over ETI Assessment &/OR AE PASS Method 4 Yes Yes 10 5 Method 7 Yes Yes Yes Yes 10 5 Method 9 Yes Yes Yes Yes 10 5 Method 9 Yes Yes Yes Yes 10 5 Method 9 Yes Yes Yes Yes 10 5 Method 4 Yes Yes 10 5 Method 9 Yes Yes Yes Yes 10 5 Method 3 Yes Yes 9 5 Method 4 Yes Yes 9 5 Method 7 Yes Yes Yes Yes 9 5 Method 7 Yes Yes Yes Yes 9 5 Method 9 Yes Yes Yes Yes 9 5 Method 10 No Yes Yes Yes 9 5 Method 5 Yes Yes Yes 9 5 Method 4 Yes Yes 9 5 Method 9 Yes Yes Yes Yes 9 5 Method 3 Yes Yes 9 5 Method 7 Yes Yes Yes Yes 9 5 Method 9 Yes Yes Yes Yes 9 5 Method 9 Yes Yes Yes No 9 5 Method 3 Yes Yes 8 4 Method 7 Yes Yes Yes Yes 8 4 Method 8 No Yes Yes Yes 8 4 Method 10 No Yes Yes Yes 8 4 Method 10 No Yes Yes Yes 8 4 Method 5 Yes Yes Yes 8 4 Method 3 Yes Yes 8 4 Method 7 Yes Yes Yes Yes 8 4 Method 9 Yes Yes Yes Yes 8 4 Method 4 Yes No 8 4 Method 7 Yes Yes Yes Yes 8 4 Method 7 Yes Yes Yes No 8 4 Method 9 Yes Yes Yes No 8 4 Method 10 No Yes Yes Yes 8 4 Method 4 Yes Yes 8 4 Method 9 Yes No Yes Yes 8 4 Method 5 Yes Yes Yes 8 4 Method 5 Yes Yes Yes 8 4 Method 9 Yes Yes Yes Yes 8 4 Method 8 No Yes Yes Yes 7 3 Method 8 No Yes Yes Yes 7 3 Method 10 No Yes Yes Yes 7 3 Method 6 No Yes Yes 7 3 Method 7 Yes Yes Yes Yes 7 3 Method 10 No Yes Yes Yes 7 3 Method 3 Yes No 7 3 Method 7 Yes Yes Yes No 7 3 Method 8 No Yes Yes Yes 7 3 Method 10 No Yes Yes Yes 7 3 Method 10 No Yes Yes No 7 3 Method 3 Yes Yes 7 3 Method 7 Yes No Yes Yes 7 3 Method 9 Yes No Yes Yes 7 3 Method 9 Yes No Yes No 7 3 Method 7 Yes Yes Yes Yes 7 3 Method 9 Yes Yes Yes Yes 7 3 Method 9 Yes No Yes No 7 3 Method 9 Yes Yes Yes Yes 7 3 Method 5 Yes Yes Yes 7 3 Method 8 No Yes Yes Yes 6 3 Method 9 Yes Yes Yes Yes 6 3 Method 6 No Yes Yes 6 3 Method 5a Yes No Yes 6 3 Method 8 No Yes Yes Yes 6 3 Method 10 No Yes Yes Yes 6 3 Method 8 No Yes Yes Yes 6 3 Method 8 No Yes Yes No 6 3 Method 10 No Yes Yes No 6 3 Method 7 Yes No Yes Yes 6 3 Method 7 Yes No Yes No 6 3 Method 9 Yes No Yes No 6 3 Method 10 No No Yes Yes 6 3 Method 6 No Yes Yes 6 3 Method 6 No Yes Yes 6 3 Method 4 Yes Yes 6 3 Method 7 Yes Yes Yes Yes 6 3 Method 7 Yes No Yes No 6 3 Method 9 Yes No Yes No 6 3 Method 10 No Yes Yes Yes 6 3 Method 4 Yes Yes 6 3 Method 7 Yes Yes Yes Yes 6 3 Method 9 Yes Yes Yes Yes 6 3 Method 9 Yes Yes Yes No 6 3 Yes Yes Yes Yes 5 2 Method 9 Yes Yes Yes Yes 5 2 Method 1 Yes 5 2 Method 5 Yes Yes Yes 5 2 Method 5a Yes No Yes 5 2 Method 8 No Yes Yes Yes 5 2 Method 8 No Yes Yes No 5 2 Method 9 Yes Yes Yes Yes 5 2 Method 7 Yes No Yes No 5 2 Method 8 No No Yes Yes 5 2 Method 10 No No Yes Yes 5 2 Method 10 No No Yes No 5 2 Method 5 Yes Yes Yes 5 2 Method 5a Yes No Yes 5 2 Method 5a Yes No Yes 5 2 Method 3 Yes Yes 5 2 Method 7 Yes No Yes No 5 2 Method 8 No Yes Yes Yes 5 2 Method 10 No Yes Yes Yes 5 2 Method 10 No No Yes No 5 2 Method 3 Yes Yes 5 2 Method 7 Yes Yes Yes Yes 5 2 Method 7 Yes Yes Yes No 5 2 Method 9 Yes Yes Yes No 5 2 Method 10 No Yes Yes Yes 5 2 Method 5 Yes Yes Yes 5 2 Method 6 No Yes Yes 5 2 Method 2 Yes 5 2 Method 7 Yes Yes Yes Yes 4 2 Method 10 No Yes Yes Yes 4 2 Method 6a No No Yes 4 2 Method 9 Yes Yes Yes Yes 4 2 Method 7 Yes Yes Yes Yes 4 2 Method 9 Yes Yes Yes No 4 2 Method 8 No No Yes Yes 4 2 Method 8 No No Yes No 4 2 Method 10 No No Yes No 4 2 Method 1 Yes 4 2 Method 8 No Yes Yes Yes 4 2 Method 8 No No Yes No 4 2 Method 10 No No Yes No 4 2 Method 7 Yes Yes Yes No 4 2 Method 8 No Yes Yes Yes 4 2 Method 10 No Yes Yes Yes 4 2 Method 10 No Yes Yes No 4 2 Method 1 Yes 4 2 Method 5a Yes No Yes 4 2 Method 2 Yes 4 2 Method 8 No Yes Yes Yes 3 2 Method 10 No Yes Yes Yes 3 2 Method 6 No Yes Yes 3 2 Method 6a No No Yes 3 2 Method 7 Yes Yes Yes Yes 3 2 Method 7 Yes Yes Yes No 3 2 Method 10 No Yes Yes Yes 3 2 Method 4 Yes No 3 2 Method 8 No No Yes No 3 2 Method 9 Yes No Yes Yes 3 2 Method 6 No Yes Yes 3 2 Method 6a No No Yes 3 2 Method 6a No No Yes 3 2 Method 4 Yes No 3 2 Method 8 No No Yes No 3 2 Method 9 Yes Yes Yes Yes 3 2 Method 8 No Yes Yes Yes 3 2 Method 8 No Yes Yes No 3 2 Method 10 No Yes Yes No 3 2 Method 6 No Yes Yes 3 2 Method 2 Yes 3 2 Method 8 No Yes Yes Yes 2 1 Method 5a Yes No Yes 2 1 Method 10 No Yes Yes Yes 2 1 Method 8 No Yes Yes Yes 2 1 Method 10 No Yes Yes No 2 1 Method 3 Yes No 2 1 Method 7 Yes No Yes Yes 2 1 Method 9 Yes No Yes No 2 1 Method 5a Yes No Yes 2 1 Method 3 Yes No 2 1 Method 7 Yes Yes Yes Yes 2 1 Method 9 Yes No Yes No 2 1 Method 4 Yes No 2 1 Method 8 No Yes Yes No 2 1 Method 9 Yes Yes Yes Yes 2 1 Method 5 Yes Yes Yes 2 1 Method 5a Yes No Yes 2 1 Method 6a No No Yes 2 1 Method 0 2 1 Method 8 No Yes Yes Yes 1 0 Method 8 No Yes Yes No 1 0 Method 7 Yes No Yes No 1 0 Method 10 No No Yes Yes 1 0 Method 10 No No Yes No 1 0 Method 7 Yes No Yes No 1 0 Method 10 No Yes Yes Yes 1 0 Method 10 No No Yes No 1 0 Method 3 Yes No 1 0 Method 7 Yes Yes Yes Yes 1 0 Method 9 Yes Yes Yes No 1 0 Method 10 No Yes Yes Yes 1 0 Method 10 No Yes Yes No 1 0 Method 1 No 0 0 Method 6a No No Yes 0 0 Method 8 No No Yes Yes 0 0 Method 8 No No Yes No 0 0 Method 1 No 0 0 Method 6a No No Yes 0 0 Method 8 No Yes Yes Yes 0 0 Method 8 No No Yes No 0 0 Method 7 Yes Yes Yes No 0 0 Method 8 No Yes Yes Yes 0 0 indicates data missing or illegible when filed

[0092] While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the methods and apparatus disclosed herein may be made without departing from the scope of the invention which is defined in the appended claims.