### Draft Peer Review Document – Do Not Cite Or Quote



# Evaluation Of Releases From New And Upgraded Underground Storage Tank Systems

Peer Review Draft – August 2004

EPA Office Of Underground Storage TanksDraft Peer Review Document– Do Not Cite Or Quote

1 

## Table Of Contents

Introduction................................................................................................................... ................ 3 Background ..................................................................................................................... .............. 3 Purpose Of This Report......................................................................................................... ....... 3 Methodology .................................................................................................................... .............. 4 Data Gathering................................................................................................................. ............... 4 Use Data....................................................................................................................... ................... 6 Statistical Analysis........................................................................................................... ............... 6 Limitations Of The Data ........................................................................................................ ...... 7 Results ........................................................................................................................ .................... 7 Number Of Data Points.......................................................................................................... ......... 7 Sources Of Releases............................................................................................................ ............ 8 Causes Of Releases............................................................................................................. ............ 9 Tank Releases .................................................................................................................. ............. 11 Relationship Between Tank Construction, Use, And Releases ................................................ 11 Causes Of Tank Releases........................................................................................................ .. 13 Piping Releases ................................................................................................................ ............. 15 Relationship Between Piping Cons truction, Use, And Releases .............................................. 15 Piping Product Delivery And Sumps........................................................................................ 16 Causes Of Piping Releases...................................................................................................... .. 17 Media Affected And Extent Of Releases...................................................................................... 19 Method Of Release Identification............................................................................................... .. 21 Age Distributions Of Tank And Piping Releases Versus Age Distributions Of Tank And Piping Use ............................................................................................................................ .................... 23 Summary And Conclusions........................................................................................................ 27 Releases And Causes ............................................................................................................ ........ 27 Tanks.......................................................................................................................... ................... 27 Piping ......................................................................................................................... ................... 28 Method Of Discovery And Leak Detection.................................................................................. 29 Extent Of Releases And Media Affected...................................................................................... 30Draft Peer Review Document– Do Not Cite Or Quote

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## List Of Figures And Tables
Figure 1 - States Participati ng In The Data Gathering.................................................................... 4 Table 1 - Information On Location, Begin-End Da tes Of Data Gathering, And Number Of Data Points Gathered................................................................................................................ ....... 5 Figure 2 - Valid And Invalid Data Points ....................................................................................... 8 Figure 3 - Sources Of Releases................................................................................................. ...... 9 Figure 4 – Known Causes Of Releases By Source....................................................................... 10 Figure 5 - Use And Release Frequenc ies For Different Tank Designs......................................... 11 Figure 6 - Use And Release Frequencies For Si ngle Walled And Double Walled Tank Designs 12 Figure 7 - Use And Release Frequencies For Single Walled And Double Walled Tanks............ 13 Figure 8 - Causes Of Releases From Steel Tanks......................................................................... 14 Figure 9 - Causes Of Releases From Single And Double Walled Steel Tanks ............................ 14 Figure 10 - Causes Of Releases From Si ngle And Double Walled Fiberglass Tanks.................. 15 Figure 11 - Use And Release Frequencie s For Different Piping Designs .................................... 16 Figure 12 - Use And Release Frequencies Fo r Single Walled And Double Walled Piping......... 16 Figure 13 - Causes Of Releases From Metal, Flexible Plastic, And Fiberglass Piping................ 18 Figure 14 - Causes Of Releases From Singl e Walled And Double Walled Fiberglass Piping Systems ........................................................................................................................ ......... 18 Figure 15 - Extent Of Releas es For Different Sources ................................................................. 19 Figure 16 – Media Affected For Different Sources...................................................................... 20 Figure 17 - Extent Of Releases To Soil Only For Different Sources ........................................... 20 Figure 18 - Extent Of Releases To Water For Different Sources................................................. 21 Figure 19 - Methods Of Re lease Identification............................................................................. 22 Figure 20 - Success Rates For L eak Detection Technologies....................................................... 23 Figure 21 – Age Distribution Of Ta nk And Piping Use And Releases ........................................ 24 Figure 22 – Examples Of Age Distribu tion Of Tanks And Tank Releases.................................. 25 Figure 23 - Age Distribution Of Piping And Piping Releases...................................................... 26 Figure 24 – Comparison Of Piping Use And Releases By Material Of Construction For Piping Less Than Or Equal To Ten Years Old ................................................................................ 26Draft Peer Review Document– Do Not Cite Or Quote

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## Introduction In this document EPA presents the results of the collec tion and analysis of release information from underground storage tank (U ST) systems. The report discusses the background, purpose, methodology used, data limita tions, results, and summary and conclusions. Supporting information is in the appendices. 

## Background In 1984, Congress responded to the increasi ng threat to groundwater posed by leaking underground storage tanks by adding Subtitle I to the Resource Conservation and Recovery Act (RCRA). This legislation required the U.S. E nvironmental Protection Agency (EPA) to develop a comprehensive regulatory program for USTs stor ing petroleum or certain hazardous substances in order to protect the envi ronment and human health from releases. EPA’s Office of Underground Storage Tanks (OUS T) developed regulations for owners and operators of UST systems covering leak detection and prevention, including minimizing the potential for USTs to corrode. (The regulations also cover additional requirements, such as financial responsibility and corrective action, not discussed in this report.) The regulatory requirements were phased in over ten years; the final deadli ne was December 1998. Federal and state regulations helped EPA achieve its manda te. As a result of these regulations, USTs are now significantly more pr otective of human health and the environment than those installed before the requirements we re implemented. Despite these improvements, however, releases from new and upgraded UST systems continue. To respond to this, OUST initiated an effort to evaluate the performance of UST systems. The sp ecific objectives of the effort are to:

• Identify the most common sources and causes of releases.
• Determine how successful leak detection methods are at detecting releases.
• Determine what, if any, improvements are needed in the UST program. EPA needs to know where problems are occurr ing, why they are occu rring, whether leak detection is quickly identifying the problems, and the extent of problem. In 1999, two EPA regional offices began gathering data from thei r state partners when a new release occurred. Two additional regions then joined in the data -gathering effort and one State Fund offered to provide data on new releases. EPA collected th e data from the regions and the State Fund and merged and summarized it in this report. 

## Purpose Of This Report The purpose of this report is for EPA to develop quantitative information on the sources and causes of releases from UST systems so that future work to improve UST system performance is appropriately focused. In addi tion, the report examines the performance of release (leak) detection methods in detecting releases at UST fac ilities. When tank or piping isDraft Peer Review Document– Do Not Cite Or Quote

4 the source of a problem, the report evaluates th e construction details of the tank or piping and compares the releases from different construction t ypes to their frequency of use. The report also looks at UST system age at the time of releas e, the extent of the release, and secondary containment. 

## Methodology Data Gathering Twenty-two states from EPA Regions 1, 3, 4, and 6 and the Missouri Petroleum Storage Tank Insurance Fund (MO Fund) provided data on 687 UST system problems for this report. EPA determined 580 of the data points contai ned useful information. Figure 1 shows a map highlighting the states that provided data for th is report. The data ga thered in the regions represents releases discovered between Sept ember 1999 and February 2003. Each region began gathering data at different times. The MO Fund provided data from the December 1998 deadline through July 2002. Table 1 shows th e regional data source, dates of data gathering, state where the data was gathered, and the numbe r of data points gathered.
Figure 1 - States Participating In The Data Gathering

ALASKA

CALIFORNIA IDAHO OREGON

WASHINGTON

MO NT ANA

WYOMING

UTAH

COLORADO

A RIZONA

TEXAS KANS AS NEBRASKA SOUTH DA KOT A MINNESOTA

WISCONS IN

IOWA

ILLINOIS OHIO INDIANA

K ENTUCKY WV
VIRGINIA

NO. CAROLINA

FLORIDA ALABAM A MISSOURI

A RKANSAS HAW AII MICHIGAN

PENNSYLVANIA NJ NEW YORK C T MA

TE NNESSE E

CAROL INA SO. MD DE RI

- DC - PR - VI

- Guam - NMI - American Samoa NEW M EXICO OKLAHOM A NORTH DA KO TA

GEORGIA MS
LA NH MAINE
VT

NEV ADA

= Participating StateDraft Peer Review Document– Do Not Cite Or Quote

5 Table 1 - Information On Location, Be gin-End Dates Of Data Gathering, And Number Of Data Points Gathered Data Source Begin-End Dates Of Data Gathering State Data Points Gathered Total Useful CT 11 9 MA 141 95 ME 91 84 NH 8 8 RI 1 1 Region 1 September 1999 - January 2003

VT 11 10 DE 10 5 MD 3 3 PA 54 49 VA 9 9 Region 3 October 2001 - October 2002
WV 13 10 AL 12 12 GA 16 14 KY 18 18 MS 11 11 NC 7 6 SC 50 46 Region 4 October 2000 - February 2003

TN 12 12 AR 59 48 LA 6 6 NM 6 6 Region 6 January 2000 - July 2002
OK 79 60 MO Fund December 1998 - July 2002 MO 59 58 Totals: 23 687 580 The data in Table 1 does not represent all re leases for these states over the time periods designated. The reasons for this are as follows:

• Data gatherers were not able to get to ever y release to document the appropriate details.
• Reliable or sufficient information was not available for many of the releases.
• Not all states gathered data over the full length of the data-gathering.
• Not all personnel in the participa ting states gathered information. EPA regions 1, 3, 4, and 6 worked with their states to develop information-gathering forms. States then voluntarily provided the sp ecific information to their region when a release occurred in their state. Each region’s form wa s slightly different, but contained the same base information (Appendix A contains the information gathering forms for each region). The regions provided OUST with the data; OUST merged the data and performed the analysis. The MO Fund volunteered to provide EPA with informa tion on releases that have occurred since December 1998. EPA added the MO Fund data to the data provided by the regions.Draft Peer Review Document– Do Not Cite Or Quote

6 States gathered the following data for UST systems:

• material of construction
• corrosion protection
• secondary containment
• spill protection
• overfill prevention
• age • product delivery system type
• leak detection In addition, the following information was gathered for the release:

• release discovery date
• date of initial release
• source of release
• cause of release
• method of identification
• media affected
• extent of release Some states attempted to gather some in formation on specific ma nufacturer or vendor, but that effort did not yield useful inform ation. There was a comments box on the forms for additional pertinent information. 

### Use Data Based on the 580 useful data points, EPA de veloped information which compared the magnitude of problems to how often each componen t was used. For this report, EPA determined whether a problem with a specific type of tank, piping, cathodic protection, leak detection, or piping delivery method was significant by compar ing how often there was a component problem with how often the component was used. To rem ove potential bias from the data, EPA did not count a tank data point if the tank was the sour ce of release, nor did EPA count a piping data point if piping was the source of release. 

### Statistical Analysis Appendix B contains the statistical methods applied in the analysis and explains the meaning of the statistical values . Statistical methods included the z-Test for difference of proportions, Fisher’s Exact Test /Yates-Corrected Chi-Square d Test, and Kolmorgorov-Smirnov Test. Appendix C contains the data and statistical analysis . Significant and marginally significant differences in proportions are highlighted in the statisti cal analysis tables. Important results of the data and statistic al analysis are incorporated in to the results of this report.Draft Peer Review Document– Do Not Cite Or Quote

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## Limitations Of The Data EPA identified the following limitations with the data:

• Some problems may be easier to identify and ga ther data on than others. For example, a person can see a problem if it occurs from an above ground component of the UST system. However, it is more difficult to gather information on problems from buried UST components.

• When a release occurred, the rate of rele ase was unknown. Therefore, EPA does not know whether the threshold for leak detection equipment was met. This limitation is especially important when looking at whether automatic lin e leak detectors identified piping problems.

• If a release occurred and was identified between leak detecti on checks, the leak detection method would not have detected the release. Under this circumstance, EPA considered leak detection as not dete cting the release.

• When analyzing piping construction, releases from metal piping components in a nonmetal piping system were attributed to the overall nonmetal piping system. For example, some fiberglass piping releases did not occur in the fiberglass, but rather at the metal connector associated with the piping system.

• It is often difficult to determine when faulty installation is the cause of a release. Other causes may be indicated when faulty installa tion might have been a contributing factor.

• Because 23 different organizations collected data , the quality of the data could be affected (and possibly vary). To address this, EPA reviewed each data point and associated comments to ensure the highest quality of data. If EPA f ound a discrepancy, the Agency contacted the collector for clarification. If EPA could not clarify the discrepancy, the Agency did not use that data point.


## Results Number Of Data Points EPA received 687 data points (or records) from 22 states and the MO Fund. Of these, EPA determined 580 data points were useful. EPA excluded a data point if the source was unknown or the component that exhibited the pr oblem did not meet the new or upgraded UST system requirements. Figure 2 shows the br eakdown of valid and invalid data points.Draft Peer Review Document– Do Not Cite Or Quote

8 Figure 2 - Valid And Invalid Data Points

Useful Data Points 85% Source Unknown 12% Component That Leaked Did Not Meet New Or Upgrade Requirements 3%



### Sources Of Releases Figure 3 summarizes the sources of releases for the data. A total of 608 releases were reported from 580 records (some records containe d multiple sources). Dispensers and piping each represent more than 30 percent of releases and are the two most frequent sources of releases. Releases from tanks 1 and delivery problems each represent 16 percent of releases. Releases from submersible turbine pump (STP) ar eas (including line leak detector problems) and “others” together account for the remaining 5 percent of the total. Other releases include those from vent lines, fill pipes (other than delivery problems), and vapor recovery lines. The number of release sources is large enough to support st atistical analyses of the distribution of releases across so urces. The proportions of rel eases from dispensers and piping are significantly greater than the proportions of releases from a ll other sources. The statistical analysis indicates that the difference between the number of piping and disp enser releases is not large enough to conclude that di spenser releases occur more fre quently than piping releases. Delivery problems and tank releases are significantly more common in the data set than releases from STP areas and other releases.

1 Eight of 97 tank releases were contained by secondary containment and are included as part of the tank release sources and causes. However, contained problems were not the intended focus of this effort and these cases were generally not documented. For use and age analysis, these eight contained problems were removed, resulting in 89 tank releases.Draft Peer Review Document– Do Not Cite Or Quote

9 Figure 3 - Sources Of Releases

Dispenser 32% Tank 16% STP Area 4% Others 1% Delivery Problems 16% Piping 31%



### Causes Of Releases Figure 4 shows the distribution of known causes of releases from the different sources. The distribution of causes is diffe rent depending on the source of re lease. Some release sources had multiple known causes. The cause was unknown fo r more than 20 percen t of releases. Of known causes of releases, physical/mechanical damage 2 is the most common, representing 50 percent of all causes. Spills/overfills (S/O) 3 are attributed to 34 per cent of releases and corrosion to 12 percent. Delivery problems at the tank fill area always came from a spill or overfill. Examples of delivery problems include tank overfills, uncoupling a delivery hose containing product, and deliveries to monitoring wells. Faulty installations are attri buted to 4 percent of releases, but this value is likely undercounted because one may not know whether a problem occurred as a result of improper installation. The differences in values for each of the known causes (physical/mechanical damage, spills/overfil ls, corrosion, and faulty installation) are significantly different.

2 Physical/mechanical damage includes causes such as jo int failures, seal/gasket problems, ruptures, punctures, cracking, dimensional change, vehicle accidents, or any other problems resu lting from physical or mechanical action. 3 There were 14 spills/overfills that occurred either at the dispenser or during delivery but the specific location was unknown. For the purposes of this analysis, EPA assumed that the distribution of spills/overfills where the location could not be determined was similar to the distribution of those where the specific source was known. Therefore, EPA attributed eight spills/overfills to delivery and six to the dispenser.Draft Peer Review Document– Do Not Cite Or Quote

10 Figure 4 – Known Causes Of Releases By Source

0% 20% 40% 60% 80% 100%

Piping Dispenser Tank STP Area Others Delivery Problems All Sources

Release SourcePercent Of Known Release Causes Corrosion Phys/Mech Damage Faulty Install Spill/Overfill

For piping, most known causes (74 percent) are due to physical/mechanical damage. Corrosion accounts for 16 percent of piping releases and faulty in stallation for 10 percent. For piping, physical/ mechanical dama ge was significantly greater than both corrosion and faulty installation. Corrosion was margina lly greater than faulty instal lation. The cause of 30 percent of piping releases is unknown. As with piping, physical/mechanical damage was the most common cause, representing 60 percent of known dispenser releases. The ca use of spill/overfill repr esented 38 percent of known dispenser releases. For di spensers, physical/mechanical dama ge was significantly greater than spills/ overfills, and spills/ overfills was significantly greate r than both corrosion and faulty installation. The cause was unknown for 14 percent of dispenser releases. More than half of the causes of tank probl ems are unknown. Because of the way the data was gathered, some of these unknowns could be spil ls/overfills associated with delivery. For the known causes, 67 percent are associated with corrosion, 25 percent are due to physical or mechanical damage, and 8 percent are attributed to faulty installation. For tanks, corrosion was significantly greater th an physical/mechanical damage and physical/mechanical damage was significantly greater than faulty installation. All of the releases from STP areas for whic h a cause is known are attributed to physical or mechanical damage. The cause was unknown for six out of seven other release sources, with the one known cause attributed to physical/mechanical damage.Draft Peer Review Document– Do Not Cite Or Quote

11 

### Tank Releases Relationship Between Tank Construction, Use, And Releases Figure 5 shows a comparison between tank mate rial of construction, tank releases, and tank use. There were 89 tank releases to the en vironment reported in the data. In addition, there were eight tank problems that came from doubl e walled steel tanks and were contained. 4 The number of walls was not reported for one tank release. Steel tanks were the most common source of tank releases at 60 pe rcent followed by fiberglass tanks at 32 percent. The most commonly used tanks in the data are fibe rglass tanks, followed closely by steel tanks. Figure 5 - Use And Release Frequenc ies For Different Tank Designs

12% 43% 45%
32%

9% 60%

0% 20% 40% 60% 80% 100%

All Steel Composite Fiberglass Type Of TankPercent Proportion Of Tanks Proportion Of Tank Releases

Figure 6 shows an overall comparison betw een single walled (SW) and double walled (DW) tank releases and use. Singl e walled steel tanks retrofit with cathodic protection (CP) were the most common tank source at 40 percent, with single walled fiberglass at 18 percent and double walled fiberglass at 14 percent. All ot her tank designs had releases under 10 percent. Single walled fiberglass was the most commonl y used tank in the database at 27 percent followed by single walled steel tanks retrofit with CP and double walled fiberglass each at just under 20 percent.

4 Problems with UST systems that did not result in a release to the environment were not the intended focus of this effort. These cases were generally not documented. Howeve r, in the cases where they were reported, EPA included them as part of the data. However, since the component did what it was intended to do (contain the release), EPA removed these cases from the use and age to release analyses.Draft Peer Review Document– Do Not Cite Or Quote

12 Figure 6 - Use And Release Frequencies Fo r Single Walled And Double Walled Tank Designs

3% 1% 5% 2% 6% 27% 18%
6% 19% 14%
2% 18%

2% 14% 7% 5% 3% 40%

8% 1% 0% 20% 40% 60%SW Steel(Manufacturer'sCP)DW Steel(Manufacturer'sCP)SW Steel(Retrofit CP)DW Steel(Retrofit CP)SW Steel(Lined)SW Steel(Lined, CP)SW CompositeDW CompositeSW FiberglassDW Fiberglass

Type Of TankPercent Proportion Of Tanks Proportion Of Tank Releases

Overall, the data show that steel tanks account for over 40 percent of use and 60 percent of releases. This difference is st atistically significant. However, to get a better picture of steel tank performance, a detailed breakdown of the nu mber of walls and type of corrosion protection is necessary. Single walled steel tanks with manufacturer’s cathodic protection represent 14 percent of the tank population and 5 percent of releases . The proportion of releases from single walled steel tanks with manufact urer’s cathodic protec tion is significantly lower than use of these tanks in the database. Conversely, sing le walled steel tanks re trofit with cathodic protection make up almost 20 percent of th e tank population, but account for 40 percent of releases. Releases from single walled stee l tanks retrofit with cathodic protection are significantly higher than the use of these tanks. Releases from double walled steel tanks with cathodic protection (both retrofit a nd manufacturer’s) and lined stee l tanks were not significantly different than their use. Overall, fiberglass tanks are used 45 percent of the time, but account for only 32 percent of releases. The proportion of releases from all fibe rglass tanks is signific antly lower than use of these tanks. Releases from single walled fiberglass tanks are marginally lower than use of these tanks. Although double walled fiberglass tanks have a lower incidence of problems than their use, the statistical analysis does not show these values to be significantly different. Composite tanks 5 are used 12 percent of the time and experienced releases 9 percent of the time. Single walled and double walled composite tanks are each used 6 percent of the time while single walled releases fo r this tank type are 7 percent and double walled releases are 2 percent. None of these differe nces are statistically significant.

5 Composite tanks are steel tanks clad with or jacketed with a non-corrodible material.Draft Peer Review Document– Do Not Cite Or Quote

13 Figure 7 shows a comparison between single wa lled and double walled tank releases and use. Overall, double walled tanks are used 28 percent of the time and represent 22 percent of tank releases. Although double walled tanks ha ve a lower incidence of problems than its corresponding use, the statistical analysis does not show these values to be significantly different. Figure 7 - Use And Release Frequencies Fo r Single Walled And Double Walled Tanks

28% 72% 78%

22%

0% 20% 40% 60% 80% 100%

Single Walled Tanks Double Walled Tanks Type Of TankPercent Proportion Of Tanks Proportion Of Tank Releases

Causes Of Tank Releases The proportion of tank releases due to differe nt causes varies significantly with the material of construction. For steel tanks, nearly 80 percent of all known release causes are attributed to corrosion (Figure 8), 12 percent to phys ical/mechanical damage, and 10 percent to faulty installation. Causes are unknown for 36 percent of releases from steel tanks. The proportion of steel tank releases due to corrosion is significantly gr eater than releas es due to all other known causes. For fiberglass tanks, the cause is unknown for over 70 percent of releases. All of the known release causes from fiberglass tanks are attr ibuted to physical/mechanical damage. Seven of the eight causes for composite tank releas es are unknown. The one known cause was due to corrosion. The distribution of causes of re leases from single walled steel tanks is different from that for double walled steel tanks (Figur e 9). 50 of 65 causes for steel tanks where the number of walls is known (77 percent) were from single walled tanks. 30 of 36 kno wn release causes (83 percent) from single walled steel tanks were attributed to co rrosion. 21 of the 30 corrosion causes for steel tanks were from single walled steel tanks retrofit with cathodic protection and 6 were from lined steel tanks. The cause of nearly 30 percent of single wall ed steel tank releases was unknown. In contrast, the cause of rel ease was unknown for 60 percent of double walled steel tanks. Of known release cau ses from double walled steel tanks , 3 of 6 (50 percent) wereDraft Peer Review Document– Do Not Cite Or Quote

14 attributed to corrosion, 2 of 6 were due to impr oper installation, and 1 of 6 were physical or mechanical damage. These data suggest that th e causes of releases are inherently harder to determine for double walled steel tanks. In a ddition, double walled steel ta nks appear to be less prone to corrosion failure than si ngle walled steel tanks (the differe nce is marginally significant). Figure 8 - Causes Of Rele ases From Steel Tanks

Corrosion 78% Faulty Installation 10% Physical/ Mechanical

Damage

12%

Figure 9 - Causes Of Releases From Single And Double Walled Steel Tanks

30

2 14
2 50

4 9 1 3 15

0 10 20 30 40 50 60

Total Steel Tank Causes Corrosion Physical/ Mechanical

Damage Faulty Installation Unknown

Steel Tank CausesNumber Of Causes. Single Walled Double Walled

The pattern of releases from single and doubl e walled fiberglass tanks is shown in Figure 10. The total numbers of reported releases are similar for single walled fiberglass tanks and double walled fiberglass tanks. The causes of releases from si ngle walled fiberglass tanks are also almost equally divided between physical/m echanical damage and unknown. As with double walled steel tanks, the causes of releases from double walled fiberglass tanks are generally unknown, perhaps because the origin of releases fr om these tanks are again harder to diagnose.Draft Peer Review Document– Do Not Cite Or Quote

15 For composite tanks, the cause is unknown for all but one release. The number of known causes from composite tanks is not su fficient to support further analysis. Figure 10 - Causes Of Releases From Si ngle And Double Walled Fiberglass Tanks

0 0 9
0 7 16 12

0 1 11

0 5 10 15 20 25

Total Fiberglass Tank Causes Corrosion Physical/ Mechanical

Damage Faulty Installation Unknown

Fiberglass Tank CausesNumber Of Causes. Single Walled Double Walled



### Piping Releases Relationship Between Piping Construction, Use, And Releases Figure 11 shows a comparison of piping materi al of construction, piping releases, and piping use. Fiberglass piping accounted for 64 percent of piping releases, metal piping for 27 percent, and flexible plastic piping for 9 percen t. 9 percent of all pi ping releases came from metal connectors directly associated with the piping (such as flexible connectors and swing joints). 6 Flexible plastic piping systems are used 18 percent of the time and account for 9 percent of releases. Releases from flexible plastic pi ping are significantly lower than flexible plastic piping use. Although the percentage of releases was higher than use for single walled fiberglass and single walled metal piping, the differences were not statistically significant. There were six double walled metal piping systems in the data se t and no releases occurred from double walled metal piping. This difference is marginally si gnificant. A breakout of single walled and double walled flexible plastic piping is not shown in Fi gure 11 because nearly all flexible plastic piping in the database was double walled. Figure 12 shows a comparison between single walled and double walled piping releases and use. Overall, double walled pipes are used 36 percent of the time and represent 26 percent of piping releases. Releases from double walle d piping are significantly lower than its corresponding usage.

6 Note that a release from a piping type that was the resu lt of a metal connector is considered a release from and counted as a problem with the piping type when compared to piping type use.Draft Peer Review Document– Do Not Cite Or Quote

16 Figure 11 - Use And Release Frequenc ies For Different Piping Designs

18% 18% 17% 41%
22% 27%
9% 47%

0% 20% 40% 60% 80% 100%

SW Metal Flexible Plastic SW Fiberglass DW Fiberglass Type Of PipingPercent Proportion Of Piping Proportion Of Piping Releases

Figure 12 - Use And Release Frequencies For Single Walled And Double Walled Piping

36% 64% 74%

26%

0% 20% 40% 60% 80% 100%

All SW All DW Type Of PipingPercent Proportion Of Piping Proportion Of Piping Releases

Piping Product Delivery And Sumps No significant differences were found betw een use and release frequencies for the different types of piping product delivery -- pres surized (82 percent of systems, 86 percent of releases); “safe” suction (7 perc ent of systems, 7 percent of re leases); and “American” or “US” suction (11 percent of systems, 8 percent of releases). “Safe” suction piping delivery has the following characteristics:

• there is only one check valve located immediately below the suction pump;
• piping slopes so that it drai ns back to the tank; and
• below grade piping operates at le ss than atmospheric pressure.Draft Peer Review Document– Do Not Cite Or Quote

17 “American” or “US” suction is any suction sy stem that does not meet the “safe” suction criteria. In addition, differences in release fr equencies relative to us e are not statistically significant for dispensers and turb ines with and without sumps. Causes Of Piping Releases The identified causes of piping releases differ across different materials of construction. Figure 13 shows a breakout of the causes of releases by piping construction. Of known causes, physical or mechanical damage was identified as the cause of nearly 75 percent of piping releases. Over 15 percent are attributed to corrosion, and 10 pe rcent to faulty installation. The causes of 30 percent of piping releases are unknown. Physical/mechanical damage occurs significantly more fre quently than any other known piping cause. For metal piping, physical/mechanical damage was the most common known cause (61 percent). The other major cause of release from metal piping was corrosion at 39 percent. The proportion of metal piping releases due to physic al/mechanical damage wa s significantly greater than the proportion of metal piping releases due to corrosion. The cause was unknown for 35 percent of releases from metal piping. Metal piping had two rele ases where the metal flexible connector was the problem – one swing join t problem and one case where the piping was accidentally punctured. Physical/mechanical damage wa s identified as the cause of over 70 percent of releases from flexible plastic pipe, and 80 percent of rele ases from fiberglass pi pe. Physical/mechanical damage was significantly greater th an any other cause for both fi berglass and flexible plastic piping. For flexible plastic pipe, the second most common cause of releases was improper installation at 24 pe rcent. The cause was unknown for 6 percen t of flexible piping releases. For fiberglass piping, the cause was unknown for over 30 pe rcent of releases. Flexible plastic piping had one release where a metal flexible connector corroded; fiberglass piping had 13 releases where a metal connector was the problem (seven of which were due to corrosion). There were also nine releases included under physical/mechanical damage where humans punctured fiberglass piping. Since all of the releases from metal pipi ng came from single walled systems and all but one release from flexible plastic piping came fr om double walled systems, there is no basis on which to compare the causes of releases fr om single and double walled piping systems constructed from these materials. In contrast , the numbers of releases from single walled and double walled fiberglass piping systems are suffic ient to allow a statis tical comparison of the causes of releases (Figure 14). For known causes, physical/mechanical damage was identified for 54 of 62 releases (87 percent) for single walled fiberglass piping and 11 of 16 (69 percent) for double walled fiberglass systems. This difference is marginally significant. In contrast, faulty installation was identified as a cause of release fr om 4 of 16 (25 percent) double walled fiberglass piping systems, but only 3 of 62 (5 per cent) single walled systems. This difference is statistically significant.Draft Peer Review Document– Do Not Cite Or Quote

18 Figure 13 - Causes Of Releases From Metal, Flexible Plasti c, And Fiberglass Piping

39%

6% 8% 16% 61% 71% 80% 74%

0% 24% 12% 10%
0% 20% 40% 60% 80% 100%

Metal Flexible Plastic Fiberglass All Materials Piping ConstructionNumber Of Known Release Causes Corrosion Physical/Mechanical Damage Faulty Installation

Figure 14 - Causes Of Releases From Single Walled And Double Walled Fiberglass Piping Systems

5 3 22
4 84

54

16 11 1 32

0 10 20 30 40 50 60 70 80 90 100

Total Fiberglass

Causes Corrosion Physical/ Mechanical

Damage Faulty Installation Unknown

Fiberglass Piping CausesNumber Of Causes Single Walled Double WalledDraft Peer Review Document– Do Not Cite Or Quote

19 

### Media Affected And Extent Of Releases The autopsy data also included information on the extent of releases (whether releases were local or large) 7 and media affected (soil or water) 8 . The patterns of releases from different sources in terms of local or large are shown in Figure 15. Figure 15 - Extent Of Releases For Different Sources

83% 83% 72% 54% 65%

17% 35% 18% 46% 28%

0% 20% 40% 60% 80% 100%

Piping Dispenser Tank STP Area Delivery Problems Release SourcePercentage Local Large

Among the 415 records where the extent of release was recorded, 71 percent were characterized as local and 29 percent as large. When releases to all media are considered, the majority of releases from all of the individual types of sources are local. The proportion of large releases ranges from under 20 percent for dispense rs and STP areas to 46 percent for tanks. The proportion of large releases from dispensers is significantly less than the proportion of large releases from both tanks and piping. The proporti on of large releases fro m tanks is significantly higher than large releases from dispensers, deliv ery problems, and STP areas. These findings are consistent with the presence of re latively larger volumes of product to be released when tanks are damaged than when releases occur from other sources. Figure 16 shows media affected information fo r the different sources. The proportion of releases to water from piping is significantly greater than the proportions of releases to water from dispensers and delivery problems. Also, the proportion of releases to water from dispensers is significantly smaller than th e proportion of releases to wate r from tanks, the STP area, and delivery problems.

7 Extent of release data was gathered on local, large, and off-site releases. EPA combined large and off-site into one category, representing releases that were not considered local. EPA believes this is a reasonable grouping because the extent of release categorie s are intended to represent increasingly severe releases. 8 For media affected, a release to so il means that only soil was impacted. Releases to water means that either groundwater or surface water was impacted.Draft Peer Review Document– Do Not Cite Or Quote

20 Figure 16 – Media Affected For Different Sources

77%

50% 61% 48% 45% 50% 55%

23% 52% 39%

0% 20% 40% 60% 80% 100%

Piping Dispenser Tank STP Area Delivery Problems Release SourcePercentage Soil Water

Releases to different media te nd to differ in terms of extent (Figures 17 and 18). For all sources combined, nearly 90 percent of releases to soil are local. For th e individual types of sources, the proportion of local rel eases to soil ranges from 64 percent for tanks to 100 percent for the STP area. Similarly, 90 percent of releases to soil from piping ar e local, as are 93 percent of releases from dispensers and 89 percent of rel eases from delivery problems. In contrast, just over 40 percent of releases affec ting water are local, and the proporti on of local releases to water ranges from 34 percent for tanks to 63 percent for releases associated with STP areas. The proportion of local releases to soil from all sources is significantly higher than the proportion of local releases to water. Likewi se, the proportion of la rge releases to soil from all sources is significantly lower than the proportion of large re leases to water. These patterns confirm that large releases tend to reach water while lo cal releases tend to only affect soil. Figure 17 - Extent Of Releases To Soil Only For Different Sources

93% 100% 97%

0% 64% 90%

10% 7% 36% 3% 0% 50% 100%

Piping Dispenser Tank STP Area Delivery Problems Release SourcePercentage Local LargeDraft Peer Review Document– Do Not Cite Or Quote

21 Figure 18 - Extent Of Releases To Water For Different Sources

63%
42% 43% 34% 40% 38% 60% 58% 66% 57%

0% 20% 40% 60% 80% 100%

Piping Dispenser Tank STP Area Delivery Problems Release SourcePercentage Local Large

EPA also examined media affected and exte nt of release for suction and pressurized piping delivery methods. For this analysis, only the release so urces of piping, STP area, and dispenser (excluding spills /overfills) were evaluated. There were no significant differences in proportions between suction and pre ssurized delivery for local releases , large releases, releases to soil, or releases to water. 

### Method Of Release Identification Figure 19 shows how releases were identifie d. Nearly one-half of releases were identified through someone seeing or smelling the problem (visual or olfactory). Other identification methods included leak detection at 17 percent and clos ure at 13 percent. Releases were occasionally detected during property transf er or through the observation of water in the tank. The method of release iden tification was identified as othe r for 15 percent of releases. 9 Other methods of identification included tightness testing performed for reasons other than leak detection and soil/groundwater sampling results. The frequency of visual or olfactory release identification was significantly greater than iden tification by any other means. The frequency of release identification by leak dete ction and closure were likewise significantly greater than the other less frequent methods of identificati on. The method of discovery was unknown for 4 percent of releases.

9 The data contain 18 cases where tightness testing was iden tified as the method of rel ease discovery, but tightness testing was not chosen as a method of leak detection for the UST system. EPA assumed that these tightness tests were performed in reaction to a potential problem rather than as part of regularly scheduled leak detection testing. These cases were included in the other category of method of release identification.Draft Peer Review Document– Do Not Cite Or Quote

22 Figure 19 - Methods Of Release Identification

17% 13%
2% 2% 47%

15%
4% 0% 10% 20% 30% 40% 50% 60%

Visual/ Olfactory Leak Detection Other Closure Property Transfer Water In Tank Unknown
Method Of DiscoveryPercentage

Success rates for leak detect ion technologies are summari zed in Figure 20. Leak detection identified releases only 17 percent of the time in the da ta. However, there are some releases in the data where the leak detection method was not capa ble of detecting the release. For example, many leak detection methods will not detect a delivery problem or dispenser problem. EPA eliminated those releases where l eak detection was not ca pable of detecting the release to obtain the success ra tes in Figure 20. Releases were eliminated based on the following criteria:

• Line tightness testing (LTT) and line leak det ectors (LLD) would not detect a tank problem.
• Manual tank gauging (MTG), tank tightness te sting (TTT), and automatic tank gauging (ATG) would not detect a piping problem or a STP area problem.
• MTG, ATG, interstitial monito ring, TTT, and line leak detector s (LLDs) would not detect a dispenser problem.
• Only groundwater or vapor monitoring would be able to detect spills/overfills, fill pipe, vent line, and vapor recovery problems. After eliminating those releases, the overall leak detection succe ss rate was 30 percent (detecting 100 of 330 rel ease opportunities). Also, some releases had multiple leak detec tion methods that could have detected the release. For example:

• If piping was the release source, both the LLD plus line tightness testing or monthly monitoring would have had the opport unity to detect the one release.
• Some UST systems were using multiple forms of leak detection at the time of release. Therefore, there were a total of 473 opportunities to detect a release. See Appendix C for details about opportunities for leak detection to detect a release.Draft Peer Review Document– Do Not Cite Or Quote

23 Figure 20 - Success Rates For Leak Detection Technologies

32% 26% 24% 24% 19%

9% 34% 29%

20%

0% 10% 20% 30% 40%

V a por G roun dw

ater ATG LTT Inte r stitial LL D M TG SIR
I C & TT

T

Release Detection MethodSuccess Rate

Success rates (the number of instances where releases were detected divided by number of opportunities to detect them) ranged from 34 percent for vapor monito ring to 9 percent for inventory control and tank tightness testi ng (IC&TTT). The success rate for IC&TTT was significantly lower than the succe ss rates for all the other leak detection methods except manual tank gauging (MTG) and statistical inventory rec onciliation (SIR) where there was no statistical significance. None of the other success rates were significantly different from one another. The apparently poor success ra te of the leak detection systems must be interpreted cautiously. The success rates are calculated only fo r those releases in the data set where leak detection was reportedly in use a nd where the leak detection met hod was specifically designed to detect releases from the specified release source. In addition, if facilities have more than one leak detection method in place, then it is only necessary for one method to succeed for a leak to be detected. Also, the rate of each release was not known, making it impossible to know whether the threshold value was met for the leak detection equipment. Finally, it may be that some leak detection methods would ultimately have detected re leases that were instead identified by visual or olfactory methods because the problem was immediately discovered and occurred between leak detection checks. Since there is no way to identify or extract thes e cases, the analysis counts these data points as missed detections. 

### Age Distributions Of Tank And Piping Releases Versus Age Distributions Of Tank And Piping Use 10 Overall age patterns of use a nd releases from tanks and pi ping are somewhat different (Figure 21). The proportion of releases from tanks at least 10 years old (88 percent) is significantly greater than the proportion of tanks in use at least 10 years old (68 percent). In contrast, the proportion of releas es from piping at least 10 ye ars old (60 percent) is not significantly different than the pr oportion of piping in use at leas t 10 years old (52 percent). In

10 Not all data points from tank and piping releases and use had age information. This analysis includes those data that had age information associ ated with the data point.Draft Peer Review Document– Do Not Cite Or Quote

24 summary, the data indicate the likelihood of release from the ta nk population generally increases with age while age does not have a significant e ffect on the likelihood of releases from piping. Figure 21 – Age Distribution Of Ta nk And Piping Use And Releases

0% 20% 40% 60% 80% 100%

<= 5 Years <= 10 Years <= 15 Years All AgeCumulative Proportion.Of Usage/Releases Tank Usage Tank Releases Piping Usage Piping Releases

Understanding the relative performance of diffe rent materials of construction for tanks and piping over time requires a comparison of th e age distributions of releases with the age distributions use. For example, releases from a particular tank design may predominantly be reported in older systems, but this does not mean th e design is more reliable if this type of tank is no longer used and the ones remaining in servic e are also predominantly old. Similarly, if a piping design or material has been in widespread use for only a relatively short time, determining its performance long-term will not be possible. EPA compared the use and release age distri butions for different tank constructions. Examples of this comparison for two tank designs are provided in Figure 22. For both single walled steel tanks and all co mposite tanks, there ar e higher proportions of relatively young tanks (10 years ol d or less) in use than there are releases from young tanks. Therefore, releases from these t ypes of tanks tend to occur more frequently in tanks greater than 10 years old (old). This is consistent with the idea that they are relatively reliable early in their service lives, with reliability decreasing with length of use. The age distributions of release for these types of tanks are both signifi cantly different from the age di stribution of tanks of the same construction. For all other tank constructions, th e differences in use and release patterns over time are not significantly different . Full results of the statistical tests are in Appendix C.Draft Peer Review Document– Do Not Cite Or Quote

25 Figure 22 – Examples Of Age Distribut ion Of Tanks And Tank Releases

0% 20% 40% 60% 80% 100%

<= 5 Years <= 10 Years <= 15 Years All Tank AgeCumulative Proportion.Of Usage/Releases Fiberglass Usage Fiberglass Releases Steel Usage Steel Releases

For piping, the age distribution of releases cl osely parallels the age distribution of use (Figure 23). This holds true for all fiberglass, all metal, and all flexible plastic piping combined. The age distributions of use a nd releases are not significantly different from one another, although the distributions of age and releases are very different across mate rials of construction. These data indicate that, for these three construc tion materials, releases are not concentrated either in young piping or in old piping. Rather, the release rates are rela tively constant across piping, independent of age. The proportions of releases from tanks and piping less than 10 years old (young) were compared for trends across material of constr uction using the Kolmorgorov-Smirnov statistical test (see appendix C). For tanks , the proportion of releases fr om young tanks is always lower than corresponding tank use. For steel tank s with corrosion protect ion, the proportion of young releases (5 percent) is signif icantly lower than the proportion of young tanks (19 percent). This difference is mainly associated with single wall ed tanks, which account for the majority of the steel tanks and releases in the data set. The proportion of yo ung releases from composite tanks (25 percent) is also signif icantly lower than the proporti on of young composite tanks (74 percent). For piping, the proportions of releases in the first 10 year s of service life are very close to the proportions of use in the same age cate gory for the various piping constructions. These data do not indicate that any t ype of piping has disproportionate rates of early failure; the differences in early release rates across the various types of piping are not statistically significant. EPA also performed statistical analyses on re leases and use for different tank and piping constructions less than 10 years old and older than 10 years using the z-test and Fisher’s Exact test. Figure 24 shows a comparison of use versus releases for the various young piping constructions. The analysis reaffirmed that re leases from young flexible plastic piping wereDraft Peer Review Document– Do Not Cite Or Quote

26 significantly lower than corre sponding use and releases fr om young fiberglass piping were significantly greater than corresponding use. Releases from double walled piping less than 10 years old were significantly lowe r than corresponding use. The converse is true for releases from young single walled piping. There were no significan t differences between releases and use for piping constructions grea ter than 10 years old. For tanks, the only notable difference for tank construction based on young or old age was for fiberglass tanks older than 10 years. Rele ases from old fiberglass tanks were lower than corresponding use. However, the more robust (Fishe r’s Exact) statistic al test did not indicate the difference was significant. Figure 23 - Age Distribution Of Piping And Piping Releases

0% 20% 40% 60% 80% 100%

<= 5 Years <= 10 Years <= 15 Years All Pipe AgeCumulative Proportion.Of Usage/Releases Fiberglass Usage Fiberglass Releases Steel Usage Steel Releases Flex. Plastic Usage Flex. Plastic Releases

Figure 24 – Comparison Of Piping Use And Rele ases by Material Of Construction For Piping Less Than Or Equal To Ten Years Old

5% 37% 54% 43%

6% 100%

49% 44% 48% 93%

0% 20% 40% 60% 80% 100%

Metal (CP) Flexible Plastic Fiberglass (SW) Fiberglass (DW) All Fiberglass Type Of PipePercentage Piping Usage <= 10 Years Old Piping Releases <= 10 Years OldDraft Peer Review Document– Do Not Cite Or Quote

27 

## Summary And Conclusions Releases And Causes EPA gathered information on 687 releases from more than 20 states. Of these, EPA determined 580 data points contained useful re lease information from a new or upgraded UST system. The number of useful data points is large enough to support statistical analyses using simple, robust statistical methods. EPA analy zed the data for sources, causes, methods of identification, media affected, release extent, and age. Piping and dispensers are the two most common sources of releases. Fuel deliveries and tanks are the next most common sources of releases , with releases from the STP area as the other notable source. Piping has been a leading source of releases sin ce before the federal regulations went into effect, and given the various juncti ons and connections in a piping run, it is not surprising that piping remains a common source of releases. Dispensers have emerged as a leading concern, and neither EPA nor most states have release prevention or detection programs to address releases at the dispenser. Physical and mechanical damage is the mo st common overall cause of releases, followed by spills and overfills. Corrosion accounts for onl y 12 percent of releases with a known cause, though certain components are still particularly susceptible to corrosion (see tanks and piping sections below for further discussion of corrosion ). Improper installation is only identified as a cause in a small number of cases. However, due to the difficulty of determining problems at the time of installation as the cause of a probl em, EPA believes the contribution of improper installation to releases is under-r epresented. While physical and mechanical damage emerged as the leading cause of releases, EPA was often unabl e to identify the true cause of physical or mechanical damage, be it faulty material, improper operation and maintenance, improper installation, natural causes, or so me combination of these. Gene rally only sudden events, such as a puncture of a tank or piping, had obvious root causes. Despite specifi c regulatory requirements to prevent spills and overfills during delivery, these activities still occur far too often. Looking more closely at causes from specific release sources, physical and mechanical damage are the leading causes of releases for dispensers and the STP area, with a significant secondary cause for dispensers be ing spills/overfills. Delivery pr oblems in this study are always due to spill or overfill. Caus es were unknown for more than 20 pe rcent of all releases. Causes of tank and piping releases are di scussed in more detail below. 

### Tanks Tanks are a significantly less fr equent source of releases th an dispensers or piping, but still represent a signific ant proportion of releases. Fiberglass tanks are the most commonly used type of tank, followed by steel, and then composite tanks. The various types of tank constructions performed differently from each othe r. Steel tanks with cathodic protection were significantly more likely to leak relative to their use, while fiberglass tanks were significantly less likely to have releases. Co mposite tanks were neither more nor less likely to have a release given their frequency of use. Looking more clos ely at steel tanks with cathodic protection, thereDraft Peer Review Document– Do Not Cite Or Quote

28 was a distinct difference between single walled tanks that were retrofit with cathodic protection and single walled tanks installed with manufacturer’s cathodic prot ection. Single walled retrofit steel tanks are significantly more likely to rele ase given their frequency of use, whereas single walled steel tanks with manufactur er’s cathodic protecti on are significantly less likely to have a release. These results indicate that newly installe d tanks of all types tend to perform fairly well, but raise concerns about e ither the quality or durability of single walled steel tanks retrofit with cathodic protection. Double walled tanks were less likely to have a release, relative to th eir use, than single walled tanks. However, partially due to the relatively low number of data points, that difference was not statistically significant. This analysis was largely influenced by single walled retrofit steel tanks, which performed significantly worse th an expected given their frequency of use. Single walled fiberglass tanks ac tually performed marginally be tter than expected given their frequency of use, while the improvement with doubl e walled fiberglass tanks was not statistically significant. For composite tanks, the improveme nt in double walled versus single walled tanks was not statistically significant. While the cause of releases for tanks was often unknown, corrosion is the most commonly identified known cause. This result is driven largely by the large number of corrosion-related releases of retr ofit steel tanks, as well as line d steel tanks. Physical and mechanical damage accounted for all known cause s of releases for fi berglass tanks. These results highlight the need for proper operation an d maintenance of corrosi on protection for steel tanks retrofit with cathodic pr otection and the need for care wh en working around UST systems. For tanks that met the new tank standards when in stalled, proper diligence when working in and around the tank field is critical, given the number of physical and mechanical problems due to human error, such as puncturing tanks. The large number of unknow n causes highlights the challenge of determining the cause of a release fo r buried tanks (except for sudden events such as punctures). For all tanks taken together, the release rate in creases as tanks get older. This holds true for all tank types, but the relationship was only statistically significant for composite tanks and single walled steel tanks. Thes e results are not surprising a nd support a common hypothesis that tank reliability decreases with tank age. 

### Piping Piping remains a leading source of releases, despite concentrated efforts to reduce piping releases. Fiberglass piping is the most common piping material used and also accounts for the majority of piping releases. In comparing mate rials of construction, flex ible plastic piping was found to leak less frequently than expected give n its use, while the release rates for steel and fiberglass piping were not significantly different from their use. For all piping types, these results relate to actual releases to the environment, not incidents corrected before releases occur. Double walled piping significantly outperfo rmed single walled piping. Double walled piping performed better for both steel and flex ible plastic piping re lative to their use.Draft Peer Review Document– Do Not Cite Or Quote

29 Physical/mechanical damage was the most common cause of piping releases for each type of piping. Corrosion was the second most common cause for piping and was attributed to flexible plastic and fiberglass piping as well, due to corrosion of meta l connectors used with those types of piping. As indicated above, faulty installation is likely unde rcounted as a cause of release because it can be difficult to identify faulty installation as the cause of releases that occur well after a system is installed, even though mistakes at installation can lead to releases well into the future. No significant differences were found between use and the release frequencies for the different types of piping delivery systems (suction and pressure). EPA found no distinguishable reliability differe nces with respect to piping age – both young and old piping are experiencing problems. With regard to sp ecific materials of construction, flexible plastic piping has not been used long enough to compare its short-term and long-term reliability. Conversely, almost all steel piping is more than 10 years old, so comparisons between short-term and long-term re liability of steel pipi ng were not possible. Fiberglass piping, which has been used for a long time and is still commonly installed today, shows no distinguishable pattern in terms of cha nges in reliability over ti me. The other notable age-related finding is that rel eases from young double walled pipi ng systems were significantly less than corresponding use. 

### Method Of Discovery And Leak Detection Nearly half of all releases were discover ed by someone either seeing or smelling the problem, despite comprehensive leak detection re quirements in place since 1993. Leak detection detected only 17 percent of all re leases reported. Part of the r eason for this low rate of leak detection success is because leak detection syst ems are generally designed to detect releases from tanks and piping, not from delivery spills/o verfills or problems at the dispenser. Since dispenser and delivery problems were such co mmon sources of releases, leak detection equipment often did not have an opportunity to de tect the release. To better gauge the success of the actual leak detection syst em, EPA narrowed the analysis to releases the leak detection systems should have been able to detect. In th is subset of releases, leak detection systems detected 30 percent of releases. While this result must still be interpreted cautiously, leak detection is clearly not detecti ng releases at the rate envisioned at the time EPA developed the regulations. In comparing the relative performance of vari ous types of leak dete ction equipment, the only significant result was that inventory control combined with tank tightness tests performed worse than most other leak dete ction equipment. This tends to support EPA’s decision to phase out the use of inventory cont rol and tank tightness testing. Some leaks are still discovered at the time of closure and/or prope rty transfer. This suggests there still may be existing releases not yet identified.Draft Peer Review Document– Do Not Cite Or Quote

30 

### Extent Of Releases And Media Affected Only about 30 percent of all rel eases were characterized as la rge. However, this varied significantly by source. Nearly ha lf of tank releases were characterized as large, whereas less than 20 percent of releases from dispensers or ST P areas were characterized as large. Given the volume of product contained in tanks, it is not su rprising that releases from tanks tend to be larger than most other releases. More than 40 percent of all releases a ffected either groundwater or surface water (collectively considered “water”). Releases from piping affected water more than half the time, which was significantly more than releases from dispensers or delivery problems. Dispenser releases affected water less than 25 percent of the time, significantly less than all other sources. For pressurized and suction piping delivery syst ems, there were no significant differences in proportions between the two deliv ery systems for local releases, la rge releases, rele ases to soil, or releases to water. Larger releases and releases to water are generally more problematic from an environmental perspective. Using these two indicators, individual ta nk and piping releases appear to be most significant whil e releases from dispensers appear to be less significant. The large number of piping releases coupled with the relatively large size and impact of piping releases indicates that piping is the most significant source of releases from UST systems.Draft Peer Review Document – Do Not Cite Or Quote



## Appendix A – Regional Forms
Appendix A contains instructions and forms used by EPA Regions 1, 3, 4, and 6 to capture and report informa tion about releases from unde rground storage tank systems.***DO NOT USE IF BARESTEEL*** Region 1 LUST Site Release Report Agency Information

___________________________________ ___________________________________ __________________________ (Inspector) (Agency) (Date) Site Information

__________________ _______________________________________________________________________________________ (Facility ID #) (Site Name/Street Address) _____________________________________________ Fac ility type: 

### “ Retail Gasoline Outlet (City / State / County / Zip Code) 

### “ Other _______________

__________________________________________________________________________________________________________________ System Information TANK Material: 

### “ Galv. Steel 

### “ Fiberglass 

### “ Composite 

### “ Unprotected Baresteel 

### “ Other ____________________
C.P./lining ( / all that apply): 

### “ Lined 

### “ Sacrificial Anode 

### “ Retrofit C.P/Impressed Current.

Walls: 

### “ Single wall 

### “ Double wall (same material) 

### “ Double wall (jacketed) 

### “ Unknown

Product: 

### “ Gasoline 

### “ Diesel 

### “ Used oil 

### “ Haz. Substance 

### “ Heating oil 

### “ Other
Age: 

### “ 0-5yr 

### “ 6-10yr 

### “ 11-15yr 

### “ >15yr 

### “ Unknown
Upgrade: 

### “ Spill bucket 

### “ Overfill protection 

### “ None 

### “ Unknown

------------------------------------------------------------------------------------------------------------------------ PIPING Material: 

### “ Galv. steel 

### “ C.P. 

### “ Rigid fiberglass 

### “ Flexible plastic 

### “ Other____________

Walls: 

### “ Single wall 

### “ Double wall (rigid) 

### “ Double wall (trench liner)
Age: 

### “ 0-5yr 

### “ 6-10yr 

### “ 11-15yr 

### “ >15yr 

### “ Unknown

Containment: 

### “ Dispenser sump 

### “ Turbine sump 

### “ None 

### “ Unknown
Pump type: 

### “ Pressure 

### “ Exempt European suction 

### “ Conventional suction 

### “ None 

### “ Other______________

__________________________________________________________________________________________________________________ Leak Detection Check all method(s) used at time of release identification



### “ Manual Inventory Reconciliation 

### “ Manual Tank Gauging


### “ SIR (Brand/Model________________________) 

### “ Dispenser sump LD


### “ TTT (Brand/ Model________________________) 

### “ LTT test (Brand/Model

_____________________ )


### “ ATG (Brand/Model________________________) 

### “ Interstitial (Brand/Model

____________________ )


### “ GW (Brand/Model_________________________) 

### “ Vapor (Brand/Model _____________ __________ )


### “ Mechanical LLD (Brand/Model_______________) 

### “ Electronic LLD (Brand/Model _______________ )


### “ No leak detection was used 

### “ Unknown

Last TTT? 

### “ Pass 

### “ Fail 

### “ Inconclusive Date:_____ ______________ Last LTT? 

### “ Pass 

### “ Fail 

### “ Inconclusive Date:______

_______________ Last SIR? 

### “ Pass 

### “ Fail 

### “ Inconclusi ve Date:_____________________

Release InformationDate release discove red___________________ Estim ated date of initial re lease ___________________

Source of release: 

### “ Tank 

### “ Piping 

### “ Dispenser 

### “ Spill/Overfill 

### “ Unknown

Cause: 

### “ Physical damage 

### “ Corrosion 

### “ Mechanical failure 

### “ Spill/Overfill


### “ Faulty installation 

### “ Unknown 

### “ Other____________________________

How identified? 

### “ LD method(s) specify _____________________ 

### “ Closure/Removal 

### “ Property transfer


### “ Visual/olfactory 

### “ Water in tank 

### “ Unknown 

### “ Other________________
Estimated age of spill/release: 

### “ Recent (< 1yr) 

### “ Old (>1yr) 

### “ Unknown

Estimated extent: 

### “ Localized tank 

### “ Localized piping 

### “ Localized Dispenser


### “ Large (beyond excavated area) 

### “ Off-site

Medium affected 

### “ Soil 

### “ Groundwater 

### “ Surface water

__________________________________________________________________________________________________________________ Additional Information:

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

Key to abbreviations C.P. Cathodic Protection TTT Tank Tightness Test (precision test) LD Leak Detection LTT Line Tightness Test Galv. Galvanized ATG Automatic Tank Gauging System SIR Statistical Inventory Reconciliation Vapor Vapor Monitoring System GW Groundwater Monitoring System LLD Line Leak Detector***DO NOT USE IF BARESTEEL*** Region 3 Version 1.01 LUST Site Release Report Agency Information

___________________________________ ___________________________________ __________________________ (Inspector) (Agency) (Date) Site Information

__________________ _______________________________________________________________________________________ (Facility ID #) (Site Name/Street Address) _____________________________________________ Fac ility type: 

### “ Retail Gasoline Outlet (City / State / County / Zip Code) 

### “ Other _______________

__________________________________________________________________________________________________________________ System Information TANK Material: 

### “ Steel 

### “ Fiberglass 

### “ Composite 

### “ Other _____________________________________
C.P./lining ( / all that apply): 

### “ Lined 

### “ Sacrificial Anode 

### “ Retrofit C.P/Impressed Current.

Walls: 

### “ Single wall 

### “ Double wall (same material) 

### “ Double wall (jacketed) 

### “ Unknown

Product: 

### “ Gasoline 

### “ Diesel 

### “ Used oil 

### “ Haz. Substance 

### “ Heating oil 

### “ Other
Age: 

### “ 0-5yr 

### “ 6-10yr 

### “ 11-15yr 

### “ >15yr 

### “ Unknown
Upgrade: 

### “ Spill bucket 

### “ Overfill protection 

### “ None 

### “ Unknown

------------------------------------------------------------------------------------------------------------------------ PIPING (Note: if nonmetal piping has metal connectors, and these are s ource of release, please provide details in the comments field) Material: 

### “ Steel 

### “ C.P. 

### “ Rigid fiberglass 

### “ Flexible plastic 

### “ Other____________

Walls: 

### “ Single wall 

### “ Double wall (rigid) 

### “ Double wall (trench liner)
Age: 

### “ 0-5yr 

### “ 6-10yr 

### “ 11-15yr 

### “ >15yr 

### “ Unknown

Containment: 

### “ Dispenser sump 

### “ Turbine sump 

### “ None 

### “ Unknown
Pump type: 

### “ Pressure 

### “ Exempt European suction 

### “ Conventional suction 

### “ None 

### “ Other______________

__________________________________________________________________________________________________________________ Leak Detection Check all method(s) used at time of release identification



### “ Manual Inventory Reconciliation 

### “ Manual Tank Gauging


### “ SIR (Brand/Model________________________) 

### “ Dispenser sump LD


### “ TTT (Brand/ Model________________________) 

### “ LTT test (Brand/Model

_____________________ )


### “ ATG (Brand/Model________________________) 

### “ Interstitial (Brand/Model

____________________ )


### “ GW (Brand/Model_________________________) 

### “ Vapor (Brand/Model _____________ __________ )


### “ Mechanical LLD (Brand/Model_______________) 

### “ Electronic LLD (Brand/Model _______________ )


### “ No leak detection was used 

### “ Unknown

Last TTT? 

### “ Pass 

### “ Fail 

### “ Inconclusive Date:_____ ______________ Last LTT? 

### “ Pass 

### “ Fail 

### “ Inconclusive Date:______

_______________ Last SIR? 

### “ Pass 

### “ Fail 

### “ Inconclusi ve Date:_____________________

Release InformationDate release discove red___________________ Estim ated date of initial re lease ___________________
Source of release: 

### “ Tank 

### “ Piping 

### “ Dispenser 

### “ Other ___________________________

Cause: 

### “ Physical damage 

### “ Corrosion 

### “ Mechanical failure 

### “ Spill/Overfill


### “ Faulty installation 

### “ Unknown 

### “ Other____________________________

How identified? 

### “ LD method(s) specify _____________________ 

### “ Closure/Removal 

### “ Property transfer


### “ Visual/olfactory 

### “ Water in tank 

### “ Unknown 

### “ Other________________

Estimated extent: 

### “ Localized tank 

### “ Localized piping 

### “ Localized Dispenser


### “ Large (beyond excavated area) 

### “ Off-site

Medium affected 

### “ Soil 

### “ Groundwater 

### “ Surface water

__________________________________________________________________________________________________________________ Additional Information:

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

_________________________________________________________________________________________

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_________________________________________________________________________________________

Key to abbreviations C.P. Cathodic Protection TTT Tank Tightness Test (precision test) LD Leak Detection LTT Line Tightness Test ATG Automatic Tank Gauging System Vapor Vapor Monitoring System SIR Statistical Inventory Reconciliation LLD Line Leak Detector GW Groundwater Monitoring SystemInstructions Agency and Site Information -Fill out details as appropriate. System Information - Fill out details regarding the Tank, Piping and Leak Detection at the time of the release. Check all appropriate boxes. If the tank or pipi ng are constructed of a metal other than steel, please indicate that information in the “Other” box. NOTE: It is most important to have specific details on the component that leaked. For example, if the piping was the source of the release and the cause was corrosion of a metal connector, detailed information about the piping, including information in the comments about details of the cause is needed.
Release Information - Fill out details regarding the release. The in formation most important in this section are:
Source: This is WHERE the release occurred from. Useful forms need to indicate the source of release. If the source of release is unknown, the form will not be useful. Some samples follow: Use Other = Delivery vehicle if a release occurred when the delivery driver unhooked the delivery hose from the fill pipe.
Use Source = Tank if there is an overfill at the tank. Use Other = Fill Pipe if there is a release due to some failure of the fill pipe. Use Source = Dispenser if a customer sp ills gas from the nozzle at the dispenser. Use Other = Turbine is the turbine pump is the source of the release. Use Source = Pipe AND Other = Metal Flex C onnector OR Metal Swing Joint if source is metal connector on nonmetal pipe.
Use Other = LLD if the line leak detector was source. Cause: This is WHY the release occurred. Cause is very good to know, but does not make the data unusable if this information is unknown. If you do not thi nk one of the categories fits under cause, choose Other and indicate specific details. Some samples follow: Use Cause = Spill/Overfill if there is a spill or overfill at the dispenser or at the tank.
Use Cause = Corrosion if the release was a result of corrosion. Use Other = loose component if a loose component was the cause. Use Other = Filter if the filter is the cause (you can be more specific too, such as loose filter or broken filter...) How Identified: The key information here is whether or not the release detection identified the release (and if so, specifically what leak detection. For example, the data should indicate specifically what method identified the release – such as the LLD or a tightness test, or the ATG) Estimated Extent and medium affected are good to know, but not crucial.
Additional Information - Fill out ANY additional information you have about the leak. For example, if fiberglass piping was the source, and the cause was corro sion of a flexible connector, the additional information area is the only place where we can identify the specific problem.U.S. Environmental Protection Agency Region 4 UST SYSTEM INTEGRITY FAILURE CHECKLIST
Refer to UST SYSTEM INTEGRITY FAIL URE CHECKLIST INSTRUCTIONS Report only on systems in compliance with post 1988 construction requirements (i.e. corrosion, spill and overfill protection are in place). DO NOT report on nonupgr aded systems. Please see INSTRUCTIONS.



###  Check here if filling out more than one form for this site. Number of forms for this site _____
I. State Information State_______________________________________________ Date form completed ______________________ Person completing form _____________________________________ Phone number ______________________ Employer ________________________________________________
II. Site Information Site name ___________________________________________________ Facility ID ______________________ Address __________________________________________________ ______________________ _________ (Street address) (City) (Zip Code) Facility type:



###  retail gasoline outlet



###  other ___________________________________________________ Status of tank:



###  active



###  temporary closure



###  permanent closure



###  abandoned, unclosed In compliance with:



###  release detection



###  operational requirements III. Description of system integrity failure Describe the tank failure: ____________________________________________________________________

____________________________________________________________________ Describe the piping failure: ____________________________________________________________________

____________________________________________________________________ IV. System Information Tank Material:



###  steel, dielectric coated



###  fiberglass reinforced plastic



###  fiberglass clad steel Design:



###  single wall



###  double wall



###  single wall in lined pit or vault



###  lined steel Corrosion protection:



###  galvanic, manufacturer installed



###  impressed current retrofit (date __________) Lining:



###  lined (date _______________) date of last inspection _______________________________ Date installed: ____________ years Capacity: ____________ gallons Product:



###  gasoline



###  diesel



###  used oil



###  kerosene



###  aircraft fuel



###  heating oil



###  hazardous substance Piping Material:



###  corrosion protected steel



###  rigid fiberglass



###  flexible plastic



###  other

__________________ Design:



###  single wall



###  double wall



###  single wall in lined trench Containment:



###  dispenser sump



###  turbine sump



###  none 

###  unknown Pump type:


###  pressure 

###  suction, check valve at dispenser



###  suction, check valve at tankV. Release Detection Method of tank release detection used:



###  inventory control/tank tightness testing



###  automatic tank gauging



###  statistical inventory control



###  groundwater wells



###  vapor monitor wells



###  interstitial monitoring



###  manual tank gauging Last tank tightness test:



###  pass 

###  fail



###  not applicable Method of piping release detection used:



###  automatic line leak detector and annual line tightness test (pressurized)



###  automatic line leak detector and monthly monitoring (pressurized)



###  line tightness test every three years (suction)



###  monthly monitoring (suction)



###  not required (suction) Last line tightness test:



###  pass 

###  fail



###  not applicable VI. Release information, if a release occurred Date release discovered: ________________________ Estimated date of release: _________________________
Source: (Check all that apply)



###  tank



###  piping



###  dispenser



###  unknown



###  other ________________________
Cause: (Check all that apply) 

###  physical damage



###  corrosion



###  mechanical failure



###  spill



###  overfill



###  other Who identified release? (Check all that apply)



###  owner/operator



###  third party



###  service contractor



###  state inspector



###  other ___________________ How was release identified? (Check all that apply)



###  release detection



###  during closure/removal



###  property transfer


###  visual/smell



###  water in tank



###  ground water contamination



###  surface water contamination



###  unknown



###  other _________________ Estimated extent (Check all that apply)



###  tank pit



###  piping trench



###  dispenser area



###  beyond construction excavations



###  off site Media affected (Check all that apply)



###  soil



###  ground water



###  surface water Estimated quantity of product released into environment: ___________________ gallons Estimated cleanup cost, if cleanup is required: $_________________________ Additional comments/information:UST SYSTEM INTEGRITY FAIL URE CHECKLIST INSTRUCTIONS
Background The purpose of this form is to document the effectiveness of federal and stat e UST regulations now that all interim deadlines f or release detection and upgrading have past. By analyzing facilities that are in complia nce with construction and opera tion and maintenance requirement s yet have had an integrity failure that might or has caused a release it can be determined where program improvements and priorities should be. Submit thi s form only when the means of integrity failure at such a site is known. Do not submit information on sites that have not met the 1998 upgrade requirements (i.e. bare steel t anks, whether still in operation or temporary closur e). Begin with sites for which informati on is available on or after October 1, 20 00. Multiple forms Whenever a site contains multiple failed systems complete one form for each different failed system and check the box indicatin g that more than one form has been completed for the site. Indicate the total number of form s to be filed for the site. Do not complete a form for other unfailed UST systems at the site. I. State Information Indicate the name, employer, and phone number of the person completing the form or, alte rnatively, the best person to contact s hould additional information or clarification be needed. II. Site Information Provide information about the site as requested. If the state assigns each site a unique identifying number please include that number in the Facility ID space, otherwise leave it blank. If checking box for abandoned, unclosed please insure the site is otherwise compliant with 1988 construction standards or upgraded. Operational requirements includes annual line leak detector calibration, periodi c corrosion protection system inspection, periodic lining inspection, etc. III. Description of system integrity failure Describe the tank or the piping failure in as much detail as is available, e.g., numerous tank pe rforations to lower third of t ank due to corrosion, tank cracked due to improper installation, piping leak at dispenser flex joint due to faulty seal. IV. System Information Tank material: Note the material of the failed tank’s construction. Tank design: Note design type that best fits the failed tank. Tank corrosion protection: If applicable, note whether the failed tank has manufacturer inst alled galvanic or a retrofit impressed current system. Some systems may be lined and use a corrosion protection system. Check all that apply. Tank lining: If applicable, note whether the failed tank has met upgrade requi rements by internal lining. If known, indicate when the tank was lined and, if more than ten years have elapsed, when its owner/operator last inspected it. Some systems may be lined and use a corrosion pro tection system. Check all that apply. Date installed: Note the failed tank’s date of installation. Tank product: Note all known contents of the failed tank. Piping material: Note the material of failed piping in c ontact with liquid product (not vent lines). Piping design: Note design type that best fits failed piping. Piping containment: This section refers to the presence of containment sumps under the dispenser or around the pump turbine. Check all those that apply. Piping, pump type: Note the type of pumping system. _V. Release Detection Note the method of release detection practiced at the failed ta nk or piping. If available and applicable, indicate the results of the latest tank and/or line tightness test. VI. Release Information, if a release occurred If a reportable, confirmed release occurred as a result of the sy stem integrity failure provide an estimated (or actual, if kno wn) date the release began and when it was discovered. Source: Identify the portion of the system that leaked or indicate th at the release came from a spill or overfill. A tank release is a ny failure of a tank surface that is not directly a part of any piping connection. A piping release is a failure of any porti on of the piping (except as def ined as a dispenser leak) up to and including connections to the tank. Dispense r releases are those from those portions of the piping above the shear valve. Check all that apply. Cause: Indicate the reason for the release. Check all that apply. Who identified release?: Indicate all those that identified the release. How was release identified?: Indicate any and all means that were used to identify the release. Estimated extent: Estimate the extent of the release based on the best current analysis. Media affected: Indicate which environmental media have been affected based on the best current analysis. Check all that apply. Estimated quantity of product rele ased into the environment: Based on the best current analysis how much product has been released? Estimated cleanup cost: Based on the best current analysis, should a clean up be necessa ry, how much will it cost to cleanup the release to state sta ndards?Region 6 - RELEASE DETECTION CHECKLIST If you have questions about this form or need furth er explanation please refer to the “Instructions” page.



###  Check here if filling out more than one form for this site Number of forms for this site______ I. Agency Information Inspector ___________________________ Agency ______________ Date__________ If not a State inspector Name _____________________________________________ Date__________ Company _______________________________ Phone number ___________________ II. Site Information Site name _____________________________________ Facility ID # ________________ Address ______________________________ _________________ ____________ (Street Address) (City) (Zip Code) Facility Type:



###  Retail Gasoline Outlet



###  Other ____________________ Status of tank:



###  Active



###  Temporary Closure



###  Permanent Closure



###  Abandoned In Compliance with:



###  1998 Equipment Requirements



###  Release Detection Equipment



###  Operational Requirements



###  None of the above III. System Information Tank Material



###  Galv. Steel



###  Fiberglass



###  Composite



###  Other __________________ C.P./Lining



###  Manufacturer’s C.P.


###  Retrofit C.P.



###  Lined Walls



###  Single Wall



###  Double Wall (same material) 

###  Double Wall (jacketed) 

###  Unknown Product



###  Gasoline



###  Diesel



###  Used Oil



###  Haz. Substance



###  Heating Oil



###  Other Age ______________ years Capacity ______________ gallons Piping Material



###  Galv. Steel



###  Galv. Steel w/C.P.



###  Rigid fiberglass



###  Flexible Plastic



###  Other

_______ Walls



###  Single wall



###  Double Wall



###  Trench Liner Age _____________ years Containment



###  Dispenser sump



###  Turbine sump



###  None


###  Unknown Pump Type


###  Pressure


###  Safe suction



###  Conventional suction



###  None



###  Other______________
IV. Leak Detection (Check all that apply) Method Tank(T) Pipe(P) Vendor/Model Working (y/n) Method Tank(T) Pipe(P) Vendor/Model Working (y/n) Inventory Control Manual Tank Gauging
Tank Tightness Test (TTT) Dispenser sump LD Automatic Tank Gauging (ATG) Hydrostatic line test (Line Tightness Test) Statistical Inventory Reconciliation (SIR) Electronic LLD
Ground Water Monitoring Wells (GWMW) Mechanical LLD

Vapor Monitoring No leak detection

Interstitial Monitoring Unknown
(Continued )Release Detection Checklist Page 2 IV. Leak Detection - Continued Last LLD?


###  Pass


###  Fail



###  Inconclusive Date:______________ Company:_____________________ Last TTT?


###  Pass


###  Fail



###  Inconclusive Date:______________ Company:_____________________ Last LTT?


###  Pass


###  Fail



###  Inconclusive Date:______________ Company:_____________________
Last SIR?


###  Pass


###  Fail



###  Inconclusive Date:______________ Company:_____________________
V. Release Information



###  Release to environment



###  Release to secondary containment Date release discovered _____________________ Estimated date of initial release _____________________
Source


###  Tank



###  Piping



###  Dispenser



###  Spill/Overfill



###  Unknown



###  Other_________________
Cause


###  Physical damage



###  Corrosion



###  Mechanical failure



###  Spill/Overfill



###  Other________________ Who identified? If more than one entity signaled the existence of the re lease, indicate (1) for primary and (2) for secondary

.



###  Owner/Operator



###  3 rd Party


###  Contractor


###  State


###  Federal



###  Other________________ How identified? If more than one item signaled the existence of the re lease, indicate (1) for primary and (2) for secondary

.



###  LD method(s) specify_________________



###  Closure/Removal



###  Property transfer



###  Visual/Olfactory



###  Water in tank



###  Ground water contamination



###  Surface water contamination



###  Unknown



###  Other_____________________ Estimated extent



###  Localized tank



###  Localized piping



###  Localized dispenser



###  Large (beyond excavated area) 

###  Off-site Medium affected



###  Soil



###  Groundwater



###  Surface water (check all that apply) Estimated quantity of product released into environment _______________ gallons. Estimated cleanup cost $__________________. Comments:_______________________________________________ (Attach additional comments on a separate page)

------------------------------------------------------------------------------------------------------------------------------- -------------- By my signature affixed below, I certify that I have reviewed this report for accuracy and completeness of information. I acknowledge that if I intentionally or knowingly make false statements, representations, or certifications in this report I may be subject to administrative, civil, and/or criminal penalties. Signature: ______________________________________________ Date: ___________________________ Title: __________________________________________________RELEASE DETECTION CHECKLIST INSTRUCTIONS Multiple Forms : Whenever a site contains multiple tank or piping configurations , multiple products or varied release detection methods, complet e one form for each different configuration and check the box indicating that more than one form has been completed for the site. Indicate th e total number of forms to be filed for the site. I. Agency Information: Some states may allow someone other than a State inspector to f ill out this form. If State inspector is completing this form p lease fill in relevant data. If a contractor or responsible party is completing form , please supply requested data following the statement “If not a State inspector”. II. Site Information : Provide information about the site as requested. If your agen cy assigns each site a unique identifying number, please include that number in the Facility ID# space, otherwise leave it blank. If checking box for abandoned tanks, fill out as much information as is available. If no information is available or is highly suspected as being unreliable, leave those sections blank. III. System Information : Tank Material : Note the material of tank construction. Composite means fiberglass bonded to steel. C.P./lining : Note whether the tank(s) have manufacturer installed or retr ofit cathodic protection and/or internal lining. Check all boxes that apply (e.g., retrofit C.P. and lined) Tank Walls : Note whether the tank(s) are single walled, doubl e walled, or jacketed with an interstitial space. Product : Note the last known contents of the tanks. Tank Age : Note the age of the tanks. Upgrade : Note whether the tanks(s) have spill and overfill devices in place at the time of inspection. Piping Material : Note the material of the piping in contact with liquid product (not vent lines). Piping Walls : Note whether the pipes are single walled, double wa lled or single walled contained in a trench liner. Piping Age : Note the age of the piping. If the site has piping of different ages, please note that. Containment : This section refers to the presence of containment sump s under the dispenser or around the pump turbine. Check the appropriate box(es) if the sump(s) are present. Pump type : Note the type of pumping system. Safe suction (European Suction) refers to suction lines with only one check valve located under dispenser. Conventional suction is any other suction system. IV. Leak Detection : Note the type of leak detection equipment at the site, and i ndicate whether it was working (properly functioning) at the time o f the inspection (this can be indicated with a check mark or yes/no). Check ALL that apply. Also denote whether it is for Tank (T) or Piping ( P). Last LLD : Note the result, date and testing company of last Line Leak Detector test, if any. Last TTT : Note the result, date and testing company of last Tank Tightness Test, if any. Last LTT : Note the result, date and testing company of last Line Tightness Test, if any. Last SIR : Note the result, date and testing company of last Statistical Inventory Reconciliation, if any. V. Release Information : Indicate whether there appears to have been no release at the site, a release to the e nvironment, or a release that was contain ed by the secondary containment system. Provide an estimate of the date the release began and/or the date the release was discovered, if known. I f the release was discovered during your inspection, please use the date of the inspection. Source : Identify the portion of the system that leaked or indicate th at the release came from a spill or overfill. A tank leak is an y failure of a tank surface that is not directly a part of any piping connection. A piping leak is a failure of any portion of the piping (ex cept as defined as a dispenser leak) up to and including connections to the tank. Dispenser leaks are releases from those portions of the piping which, if the piping is double walled, would be on the dispenser side of the terminus of the double walled condition, or if sin gle walled, those portions of the piping that are above grade under a dispenser. Cause : Indicate the reason for the release. Mark as many boxes as apply. Who Identified : Specify who identified the presence of a release. Can indicate more than one. How Identified : Specify how the system owner/operator became aware of th e presence of a release. Can indicate more than one. Estimated Extent : Estimate the extent of the release, based upon any and all in formation available to you at the time of the inspection and you r best professional judgement. Medium Affected : Indicate which environmental compartments have been affected by the release. Check as many as apply. Other Abbreviations (not previously clarified or spelled out on form) : C.P. Cathodic Protection Galv. Galvanized TTT Tank Tightness Test (precision test) LD Leak Detection LLD Line Leak Detector LTT Line Tightness Test (hydrostatic line test)Draft Peer Review Document – Do Not Cite Or Quote

B-1 

### Appendix B: Statistical Methods
EPA used three statistical tests to evalua te the significance of differences in the numbers and proportions of rel eases, releases as a function of use, and the differences between the patterns of facility age and age of facilities w ith releases. The first two procedures, the z-test and Fisher’s Exact Tes t/Yates-Corrected Chi-Squared, were used to evaluate differences in proportions in tw o independent samples and to measure the probability that a given pattern of results in a two-way comparison of outcomes would occur by chance, respectively. The Kolmorgorov-Smirnov test is a non-parametric test that compares cumulative distributions (in this case, the cumulative age of all facilities or facilities with releases) and indicates the pr obability that the observed difference between the distributions could arise by chan ce by sampling a single population. B-1. The z-Test For Di fference Of Proportions The z-test for difference of proportions tests the hypothesis that two independent proportions, p 1 and p 2 , are equal. The sta tistic (z) is calculated as (Sheskin, p. 379):
(B-1) (B-2)

Where: n 1 , n 2 = number of observations (e .g., facilities or records) in the sample X 1 , X 2 = number of positive successes (e.g., number of releases) in the sample p 1 , p 2 = sample proportions = X 1 /n 1 , X 2 /n 2 P = weighted average of the sample proportions Using a two-sided test, the hypothesis th at the proportions are equal can be discarded with 95 percent certainty (or p < 0.05) if (z) exceeds the critical value of 1.96. This value corresponds to the point on the normal (Gaussian) distribution which excludes 5 percent of the total probability density ( 2.5 percent on each end). The difference in proportions is characterized as marginally significant if the z value is between 1.65 and 1.96. The z value indicating a 90 percent certaint y is 1.65. The two-tailed test is used in non-directional situations wh ere there is no reason to believe that either p 1 or p 2 is greater or less than the other; it is more demandi ng (less likely to identify a difference in proportions as significant) than the one-tailed test. 

# ( ) z p p P Pn P Pn

P X X nn

=− − +−

=+ + 12 1 1 1 2

1 2 12 / ( )/ ( )/ ( )/( )Draft Peer Review Document – Do Not Cite Or Quote

B-2 In some cases, the proportions being compared are both drawn from the same set of observations (all records). In that case, the z-calculation is: (B-3)
(B-4) where: N is the total numbe r of observations (records) P is the average of the sample proportions The underlying assumption of the z-test is th at the two proportions are independent of one another and are the result of sets of Ber noulli trials having a constant probability of success. B-2. Fisher’s Exact Test /Yates-Corrected Chi-Squared When the number of observations is small, Fi sher’s Exact Test is considered to be superior for judging the differen ce in frequencies of outcomes. 1 This non-parametric (distribution-independent) pr ocedure tests the hypothesis that two sets of results (successes) in a number of observations (trials) are equal. Put another way, the procedure provides an estimate of the probability that the observed difference in proportions could have arisen by chance, assuming both samp les came from the same population. A low value (generally, p<0.05) indicates that the pr oportions being compared are significantly different. Computation of the test stat istic (p-value) is computat ionally intensive, involving exact evaluations of the probability that the specific permutations of results (n 1 successes in X 1 trials, n 2 successes in X 2 trials) could have arisen by chance, relative to all other permutations. (See Sheskin, pp. 371-376, for a comp lete description of the calculations.) In this analysis, p-values were calculated us ing the Fisher’s Exact Test algorithm in the STATISTICA® package, Version 5.0. P-valu es less than 0.05 were characterized as indications that two proportions were significantly different fr om one another. P-values between 0.05 and 0.10 were characterized as marginally different from one another.

1 Sheskin (p. 368) states that most sources recomme nd that parametric tests (Chi-Squared, z-test) not be used when the total number of observations (N, or n 1 + n 2 as defined in equations B-1 through B-4) is less than approximately 20. Some suggest that parametric tests are acceptable for N (or n 1 + n 2 ) between 20 and 40, but only if the expect ed values for all cells (the groups being compared) are at least five. 

# ( ) z p p P PN

PXX N

=− −

= + 12 1

1 22 / ( )/ ( )/Draft Peer Review Document – Do Not Cite Or Quote

B-3 Fisher’s Exact Test is also theoretical ly valid for large samples (hundreds of observations). However, because the test involves factorials, beyond a certain number of observations (on the order of a few hundr ed) the calculation exceeds the precision achievable with a PC. Thus for larger numbers of observations, EPA employed either the z-test described above, or the Yates-Corrected Chi-Square d test for the difference of proportions. The Yates-Correct ed Chi-Squared statistic ( χ 2 ) is calculated as:
(B-5)

In the equation, “i” and “j” refer to th e two groups being compared and “O” and “E” are analogous to the numbers of successes (e.g, releases, etc.) observed in one group versus the other. In a large sample from a homogeneous distribution, O and E would be equal, so the value of χ 2 would be zero. The calculated χ 2 value is compared to a table of critical values, and again, the difference in pr oportions is considered significant if the pvalue is less than 0.05 and marginally si gnificant if the p-value was between 0.05 and 0.10. As for the Fisher’s Exact Test, the Yates-Corrected Chi-Squared values were calculated using STATISTICA®. Examples of STATISTICA® output s for the Fisher’s Exact Test and Yates-Corrected Chi- Squared are given in Appendix C. B-3. Kolmorgorov-Smirnov Test As noted above, the Kolmorgorov-Smirnov (K S) test evaluates the probability that two cumulative distributi ons (such as cumulative numbe rs of releases over time) might have arisen by chance, rather than as a result of a real difference in the distributions. The KS test is simple and r obust, and performs reasonably well even when there are relatively few observations. The test statistic for the KS test is simply the largest vertical distance be tween two cumulative distributi ons. The calculation of the statistic can be illustrated using the data in Table B-1 below that compares the distribution of the age of single wall tanks with corrosi on protection with the age distribution of releases fr om this type of tanks. Table B-1. Age Distribution Of Single Wall Tanks And Releases Age Of Facility Number Cumulative Release Cumulative Proportion "M" (Difference)
Use Releases Use Releases Use Releases 0-5 yr 10 0 10 0 0.088 0.000 0.088 6-10 yr 7 0 17 0 0.150 0.000 0.150 11-15 yr 36 6 53 6 0.469 0.194 0.275 >15 60 25 113 31 1.000 1.000 0 The first columns of the table show the numbers of tanks in the data set in specified age groups (use) and the numbers of releases from the same kinds of tanks in the same age groups (releases). The numbers of tanks and releases ar e then re-expressed 

# ( )

x O E E ij ij
ij j i 2 2 05

= − −           

# ∑ ∑ .Draft Peer Review Document – Do Not Cite Or Quote

B-4 in cumulative form and are converted to cumulative probability distributions (proportions), starting at zero (no tanks, no releases) and ending at 1.0 (all tanks, all releases). The KS test then involves finding the maximum difference between the proportions of tanks and proportion of releases at any point in the age distribution. It can be seen in the final column of the table that the maximum difference occurs at 11-15 years, which corresponds to about 47 percent on the use distribution, but only about 19 percent on the release distributi on. This difference (0.275) is “M ,” the value that is used in the probability calculation. The p-values associated with different values of “M” for given degrees of freedom are tabulated in statistics texts. Ho wever, when the number of observations is large enough, the p-value can also be approximated using the Chi-Squared Approximation as follows: 2
(B-6)

Where: χ 2 = Chi-squared value (two degrees of freedom) M = Maximum vertical distance from KS test n 1 , n 2 = number of observati ons (tanks, releases) The p-value can thus be calculated usi ng the CHIDIST function in Excel®; two distributions are characterized as significantly different if the resulting p-value is less than 0.05 and marginally different if th e p-value was between 0.05 and 0.10. For the example data set, the chi-squared valu e corresponding to M = 0.275 is 7.38, and the corresponding p-value is 0.025. Thus, the two distributions are sign ificantly different. In this analysis, the KS test was used to compare cumulative age distributions of tank and piping designs and tank and pipi ng releases. The Fisher’s Exact Test described above was also used to determine if the proportion of use and releases fo r tanks and piping less than 10 years old, compared to a ll use/releases in the data set, are significantly different. The results of the two tests gi ve roughly equivalent results for the data that have been examined.
References: Sheskin, David J., Handbook of Parametric and Nonparam etric Statistical Procedures, Second Edition , Chapman and Hall, 2000.

2 When (n 1 and n 2 ) are suitably large, the quantity of the right-hand side equation B-6 is known to have a chi-squared distribution with two de grees of freedom (Sheskin, p 326). Above n 1 = n 2 = 25, the KS test critical values can be approximate d by well-behaved functions that are consistent with the Chi-squared distribution to approximate ly one percent accuracy. (Sheskin, Table A-23). x M n n n n 2 2 1 2
1 2 4 = +       *Draft Peer Review Document – Do Not Cite Or Quote



## Appendix C – Data And Statistical Analysis
Appendix C contains the release data and the statistical analysis of that data. Appendix C contains the following: Summary Of Sources.......................................................................... C-1 Causes Of Release From Each Source...................................................... C-2 Tank Use And Releases For Tanks W ith A Known Number Of Walls................. C-3 Tank Release Details........................................................................... C-4 Piping Use And Releases For Piping With A Known Number Of Walls............... C-5 Piping Release Details......................................................................... C-6 Extent Of Contamination By Source, Media............................................... C-7 Media And Extent Of Contamination Fo r Suction And Pressure Piping............... C-9 Methods Of Release Identification.......................................................... C-10 Leak Detection Success Rate Evaluation................................................... C-11 Leak Detection ID.............................................................................. C-12 Releases Versus Age Of Tanks, Piping (A ll Designs, Construction Materials)....... C-13 Age Patterns Of Use, Releases, For Ta nk Designs, Construction Materials........... C-15 Age Patterns Of Use, Releases For Pipi ng, Designs, Construction Materials......... C-16 Comparison Of Piping Types <10 Years Ol d and Piping Types >10 Years Old...... C-17 Comparison Of Tank Types <10 Years Old and Tank Types >10 Years Old......... C-18Summary Of Sources

Source Number of Releases Percentage of Records Piping 189 31.1% Dispenser 195 32.1% Tank 97 16.0% STP Area (Including LLD) 25 4.1% Others 7 1.2% Delivery Problem 95 15.6% TOTAL 1 608 100.0% 1. There were 580 records in the data set; 28 records identified two sources each. Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) Source (1) Source (2) p1 p2 p1-p2 P 1-P 1/n z p value Piping Versus Dispenser 0.31 0.32 -0.01 0.32 0.68 0.002 0.52 0.60 Tank 0.31 0.16 0.15 0.24 0.76 0.002 8.80 0.00 STP Area 0.31 0.04 0.27 0.18 0.82 0.002 17.47 0.00 Others 0.31 0.01 0.30 0.16 0.84 0.002 20.07 0.00 Delivery Problem 0.31 0.16 0.15 0.23 0.77 0.002 9.01 0.00 Dispenser Versus Tanks 0.32 0.16 0.16 0.24 0.76 0.002 9.30 0.00 STP Area 0.32 0.04 0.28 0.18 0.82 0.002 17.91 0.00 Others 0.32 0.01 0.31 0.17 0.83 0.002 20.49 0.00 Delivery Problem 0.32 0.16 0.16 0.24 0.76 0.002 9.52 0.00 Tank Versus STP Area 0.16 0.04 0.12 0.10 0.90 0.002 9.72 0.00 Others 0.16 0.01 0.15 0.09 0.91 0.002 13.05 0.00 Delivery Problem 0.16 0.16 0.00 0.16 0.84 0.002 0.22 0.82 STP Versus Others 0.04 0.01 0.03 0.03 0.97 0.002 4.56 0.00 Delivery Problem 0.04 0.16 -0.12 0.10 0.90 0.002 9.52 0.00 Other Versus Delivery Problem 0.01 0.16 -0.14 0.08 0.92 0.002 12.87 0.00 significant = marginally significant =

Appendix C C-1Causes Of Release From Each Source

Source Total Releases Total Known Causes Corrosion Phys/Mech Damage Faulty Install S/O Unknown Piping 189 135 21 100 14 0 57 Dispenser 195 178 4 106 1 67 28 Tank 97 51 34 13 4 0 51 STP Area (Including LLD) 25 22 0 22 0 0 3 Others 7 1 0 1 0 0 6 Delivery Problem 95 95 0 0 0 95 0 TOTAL 1 608 482 59 242 19 162 145 1. There were 580 records in the data set; 28 records identified 2 sources each. Some sources had multiple causes. Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n))

Cause (1) Cause (2) p1 p2 p1-p2 P 1-P 1/n z p - value Corrosion 0.502 0.122 0.380 0.31 0.69 0.00207 17.99 0.00 Spill/Overfill 0.502 0.336 0.166 0.42 0.58 0.00207 7.39 0.00 Faulty Install 0.502 0.039 0.463 0.27 0.73 0.00207 22.86 0.00 Spill/Overfill 0.122 0.336 -0.214 0.23 0.77 0.00207 11.16 0.00 Faulty Install 0.122 0.039 0.083 0.08 0.92 0.00207 6.68 0.00 Spill/Overfill Faulty Install 0.336 0.039 0.297 0.19 0.81 0.00207 16.68 0.00 Cause Comparison By Source Cause (1) Cause (2) p1 p2 p1-p2 P 1-P 1/n z p-value Corrosion Versus Phys/Mech 0.16 0.74 -0.59 0.45 0.55 0.007 13.67 0.00 Faulty Install 0.16 0.10 0.05 0.13 0.87 0.007 1.79 0.07 Phys/Mech. Versus Faulty Install 0.74 0.10 0.64 0.42 0.58 0.007 14.99 0.00 Corrosion Versus Phys/Mech 0.02 0.60 -0.57 0.31 0.69 0.006 16.55 0.00 Faulty Install 0.02 0.01 0.02 0.01 0.99 0.006 1.91 0.06 Spill/Overfill 0.02 0.38 -0.35 0.20 0.80 0.006 11.82 0.00 Phys/Mech. Versus Faulty Install 0.60 0.01 0.59 0.30 0.70 0.006 17.16 0.00 Spill/Overfill 0.60 0.38 0.22 0.49 0.51 0.006 5.85 0.00 Faulty Install Versus Spill/Overfill 0.01 0.38 -0.37 0.19 0.81 0.006 12.58 0.00 Corrosion Versus Phys/Mech 0.67 0.25 0.41 0.46 0.54 0.020 5.90 0.00 Faulty Install 0.67 0.08 0.59 0.37 0.63 0.020 8.69 0.00 Phys/Mech. Versus Faulty Install 0.25 0.08 0.18 0.17 0.83 0.020 3.38 0.00 Phys/Mech. Versus Corrosion 1.00 0.00 1.00 0.50 0.50 0.045 9.38 0.00 Faulty Install 1.00 0.00 1.00 0.50 0.50 0.045 9.38 0.00 Corrosion Versus Faulty Install 0.00 0.00 0.00 0.00 1.00 0.045 0.00 1.00 General Cause Comparison Physical/Mechanical Damage

Corrosion

Piping

significant = marginally significant = Dispenser

Tank

STP

Appendix C C-2Tank Use And Releases For Tanks With A Known Number Of Walls

Tank Type Number In Data Set 1 Proportion In Data Set Number Of Releases 2 Proportion Of Releases Tank Type Number In Data Set Proportion In Data Set Number Of Releases Proportion Of Releases Steel SW 184 39.2% 47 53.4% SW 64 13.6% 4 4.5% Steel DW 19 4.1% 5 5.7% DW 16 3.4% 3 3.4% All Steel 203 43.3% 52 59.1% Total 80 17.1% 7 8.0% All SW 339 72.3% 69 78.4% All DW 130 27.7% 19 21.6% SW 91 19.4% 35 39.8% All Tanks 469 100.0% 88 100.0% DW 3 0.6% 2 2.3% Total 94 20.0% 37 42.0% Steel w/Lining (SW) 22 4.7% 7 8.0% Steel w/Lining And CP (SW) 7 1.5% 1 1.1%
SW 27 5.8% 6 6.8% DW 27 5.8% 2 2.3% Total 54 11.5% 8 9.1%
SW 128 27.3% 16 18.2% DW 84 17.9% 12 13.6% Total 212 45.2% 28 31.8% Total All Tanks 469 88 1. Excludes records with tank release 2. Excludes 8 cases where problem was contained by secondary containment and 1 steel tank w/mfgr. CP where number of walls was not known Including the steel tank with an unknown number of walls, 60 percent (53/89) of tank releases came from steel tanks Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt p1 (Use) p2 (Releases) p1-p2 P 1-P 1/n z p - value
SW 13.6% 4.5% 9.1% 12.2% 87.8% 0.0135 2.39 0.02 DW 3.4% 3.4% 0.00% 3.4% 96.6% 0.0135 0.00 1.00 Total 17.1% 8.0% 9.1% 15.6% 84.4% 0.0135 2.16 0.03
SW 19.4% 39.8% -20.4% 22.6% 77.4% 0.0135 4.19 0.00 DW 0.6% 2.3% -1.6% 0.9% 99.1% 0.0135 1.49 0.14 Total 20.0% 42.0% -22.0% 23.5% 76.5% 0.0135 4.47 0.00 Steel w/Lining (SW) 4.7% 8.0% -3.3% 5.2% 94.8% 0.0135 1.26 0.21 Steel w/Lining, CP (SW) 1.5% 1.1% 0.4% 1.4% 98.6% 0.0135 0.26 0.80 All SW Stee l 39.2% 53.4% -14.2% 41.5% 58.5% 0.0135 2.48 0.01 All DW Stee l 4.1% 5.7% -1.6% 4.3% 95.7% 0.0135 0.69 0.49 All Stee l 43.3% 59.1% -15.8% 45.8% 54.2% 0.0135 2.73 0.01
SW 5.8% 6.8% -1.1% 5.9% 94.1% 0.0135 0.39 0.70 DW 5.8% 2.3% 3.5% 5.2% 94.8% 0.0135 1.35 0.18 Total 11.5% 9.1% 2.4% 11.1% 88.9% 0.0135 0.66 0.51
SW 27.3% 18.2% 9.1% 25.9% 74.1% 0.0135 1.79 0.07 DW 17.9% 13.6% 4.3% 17.2% 82.8% 0.0135 0.97 0.33 Total 45.2% 31.8% 13.4% 43.1% 56.9% 0.0135 2.33 0.02
SW 72.3% 78.4% -6.1% 73.2% 26.8% 0.0135 1.19 0.23 DW 27.7% 21.6% 6.1% 26.8% 73.2% 0.0135 1.19 0.23 Steel Retrofit w/CP

marginally significant = Steel w/ Mfgr. CP

Composite

Steel w/ Mfgr. CP

Fiberglass Composite Steel Retrofit w/CP

All Tanks

significant = Fiberglass

Appendix C C-3Tank Release Details

Material Walls Total Releases Corrosion Physical/ Mechanical

Damage Faulty Installation Unknown Total Known Causes SW 4 2 2 0 1 4 DW 10 2 1 2 7 5 Unknown 1 0 0 0 1 0 Total 15 4 3 2 9 9 SW 35 21 2 2 12 25 DW 3 1 0 0 2 1 Total 38 22 2 2 14 26 SW 7 6 0 0 1 6 DW 0 0 0 0 0 0 Total 7 6 0 0 1 6 SW 1 1 0 0 0 1 DW 0 0 0 0 0 0 Total 1 1 0 0 0 1 61 33 5 4 24 42 SW 6 1 0 0 5 1 DW 2 0 0 0 2 0 81 0 0 71 SW 16 0 7 0 9 7 DW 12 0 1 0 11 1 28 0 8 0 20 8 97 34 13 4 51 51 Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt Comparison 1 Comparison 2 p1 p2 p1-p2 P 1-P 1/n z p - value
Man. CP Versus Retrofit CP 0.2830 0.7170 -0.4340 0.5000 0.5000 0.0189 6.32 0.00
SW Corrosion Versus DW Corrosion 0.8333 0.5000 0.3333 0.7857 0.2143 0.1944 1.84 0.07 Steel Tanks: Causes Of Release Phys./Mech. 0.7857 0.1190 0.6667 0.4524 0.5476 0.0238 8.68 0.00 Faulty Install 0.7857 0.0952 0.6905 0.4405 0.5595 0.0238 9.01 0.00 Phys./Mech. Versus Faulty Install 0.1190 0.0952 0.0238 0.1071 0.8929 0.0238 0.50 0.62

Fisher's Exact Test - Comparison Of Corrosion Releases From Single- And Double-Wall Steel Tanks Configuration Corrosion Not Corrosion SW 30 6 DW 3 3 0.10 Note: No analysis was performed on composite tanks - only 1 known cause; for fiberglass tanks - all 8 known causes were physica l/mechanical damage. Total All Composite

Cause comparison is for known causes only. Unknown causes are not included in the totals.

Fisher's Exact Test p-value: Corrosion Versus

significant = marginally significant = Value of N is low for z-test (N=6) = Cause

Steel With Manufacturer Cathodic Protection
Steel Retrofit With Cathodic Protection
Steel With Internal Lining

BOLD Fiberglass Total All Fiberglass Total All Tanks

Steel Tanks: Corrosion Protection Steel Tanks: Single Wall Versus Double Wall Steel With Lining And Cathodic Protection
Total All Steel Composite

Appendix C C-4Piping Use And Releases For Piping With A Known Number Of Walls

Material Number In Data Set 1 Proportion In Data Set Number Of Releases 2 Proportion Of Releases Material Number In Data Set Proportion In Data Set Number Of Releases Proportion Of Releases
SW 85 22.1% 48 27.0% SW 248 64.4% 132 74.2% DW 6 1.6% 0 0.0% DW 137 35.6% 46 25.8% Total 91 23.6% 48 27.0% Total 385 178
SW 7 1.8% 1 0.6% DW 63 16.4% 15 8.4% Total 70 18.2% 16 9.0%
SW 156 40.5% 83 46.6% DW 68 17.7% 31 17.4% Total 224 58.2% 114 64.0% Total All Piping 385 178 1. Excludes records with piping releases 2. Excludes 11 piping releases where number of walls was not known Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt p1 (Use) p2 (Releases) p1-p2 P 1-P 1/n z p - value
SW 22.1% 27.0% -4.9% 23.6% 76.4% 0.008 1.27 0.20 DW 1.6% 0.0% 1.6% 1.1% 98.9% 0.008 1.67 0.09 Total Metal w/CP 23.6% 27.0% -3.3% 24.7% 75.3% 0.008 0.85 0.39
SW 1.8% 0.6% 1.3% 1.4% 98.6% 0.008 1.17 0.24 DW 16.4% 8.4% 7.9% 13.9% 86.1% 0.008 2.53 0.01 Total Flex. Plastic 18.2% 9.0% 9.2% 15.3% 84.7% 0.008 2.82 0.00
SW 40.5% 46.6% -6.1% 42.5% 57.5% 0.008 1.36 0.17 DW 17.7% 17.4% 0.2% 17.6% 82.4% 0.008 0.07 0.94 Total Fiberglass 58.2% 64.0% -5.9% 60.0% 40.0% 0.008 1.32 0.19
SW 64.4% 74.2% -9.7% 67.5% 32.5% 0.008 2.29 0.02 DW 35.6% 25.8% 9.7% 32.5% 67.5% 0.008 2.29 0.02 Piping Delivery And Dispenser/Turbine Sumps
Number In Data Set 1 Proportion In Data Set Number Of Releases Proportion Of Releases
Pressure 391 82.1% 244 85.6% Safe Suction 32 6.7% 19 6.7% US Suction 53 11.1% 22 7.7% Totals 476 285
Yes 40 27% 16 29% No 110 73% 40 71% Totals 150 56
Yes 58 30% 6 40% No 135 70% 9 60% Totals 193 15 Note: a significant number of dispenser/turbine sump Use and releases were unknown p1 (Use) p2 (Releases) p1-p2 P 1-P 1/n z p - value
Pressure 82% 86% -3% 83% 17% 0.0056 1.25 0.21 Safe Suction 7% 7% 0% 7% 93% 0.0056 0.03 0.98 US Suction 11% 8% 3% 10% 90% 0.0056 1.53 0.13
Yes 27% 29% -2% 27% 73% 0.0245 0.27 0.78 No 73% 71% 2% 73% 27% 0.0245 0.27 0.78
Yes 30% 40% -10% 31% 69% 0.0718 0.80 0.42 No 70% 60% 10% 69% 31% 0.0718 0.80 0.42

Value of N is low for z-test (N=18) = Fisher's Exact Test - Use-Release Comparison For Tanks With/Without Turbine Sumps
Configuration Releases No Releases Sump 6 52 No Sump 9 126 0.39 Turbine Sumps

Fisher's Exact Test p-value: All Piping

Piping Delivery Type

Dispenser Sumps

BOLD significant = marginally significant = Piping Delivery Type

Dispenser Sumps Metal w/CP

Turbine Sumps All Piping

Flexible Plastic

Fiberglass Metal w/CP

Flexible Plastic

Fiberglass

Appendix C C-5Piping Release Details

Material Walls Total Releases Corrosion Physical/ Mechanical

Damage Faulty Installation Unknown Total Known Causes SW 48 13 19 0 16 32 DW 0 0 0 0 0 0 Unknown 3 0 1 0 2 1 51 13 20 0 18 33 SW 1 0 1 0 0 1 DW 15 1 11 4 1 16 16 1 12 4 1 17 SW 83 5 54 3 22 62 DW 31 1 11 4 16 16 Unknown 8 1 3 3 1 7 122 7 68 10 39 85 189 21 100 14 58 135 Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt Comparison 1 Comparison 2 p1 p2 p1-p2 P 1-P 1/n z p - value Phys./Mech. 0.1556 0.7407 -0.5852 0.4481 0.552 0.03030 6.76 0.00 Faulty Install 0.1556 0.1037 0.0519 0.1296 0.870 0.03030 0.89 0.38 Phys./Mech. Versus Faulty Install 0.7407 0.1037 0.6370 0.4222 0.578 0.03030 7.41 0.00 Phys./Mech. 0.3939 0.6061 -0.2121 0.5000 0.500 0.03030 2.44 0.01 Faulty Install 0.3939 0.0000 0.3939 0.1970 0.803 0.03030 5.69 0.00 Phys./Mech. Versus Faulty Install 0.6061 0.0000 0.6061 0.3030 0.697 0.03030 7.58 0.00 Phys./Mech. 0.0588 0.7059 -0.6471 0.3824 0.6176 0.0588 5.49 0.00 Faulty Install 0.0588 0.2353 -0.1765 0.1471 0.8529 0.0588 2.05 0.04 Phys./Mech. Versus Faulty Install 0.7059 0.2353 0.4706 0.4706 0.5294 0.0588 3.89 0.00 SW Phys./Mech. Versus DW Phys./Mech. 0.8710 0.6875 0.1835 0.8333 0.1667 0.0786 1.76 0.08 SW Faulty Install Versus DW Faulty Install 0.0484 0.2500 -0.2016 0.0897 0.9103 0.0786 2.52 0.01 Phys./Mech. 0.0824 0.8000 -0.7176 0.4412 0.5588 0.0118 13.33 0.00 Faulty Install 0.0824 0.1176 -0.0353 0.1000 0.9000 0.0118 1.08 0.28 Phys./Mech. Versus Faulty Install 0.8000 0.1176 0.6824 0.4588 0.5412 0.0118 12.62 0.00

Fisher's Exact Test - Comparison Of Releases From Flexible Plastic Causes Configuration Yes No Configuration Yes No Phys/Mech 12 5 Phys/Mech 12 5 Corrosion 1 16 Faulty Install 4 13 0.00 0.02 Configuration Yes No Corrosion 1 16 Faulty Install 4 13 0.34 Fisher's Exact Test - Comparison Of Releases From SW And DW Fiberglass Piping Configuration Yes No Configuration Yes No SW Phys/Mech 54 8 SW Faulty Inst. 3 59 DW Phys/Mech 11 5 DW Faulty Inst. 4 12 0.13 0.03 Cause comparison is for known causes only. Unknown causes are not included in the totals. significant = marginally significant = Value of N is low for z-test (N=17) = BOLD Value of N is low for z-test (N=16) = BOLD Corrosion Versus Flexible Plastic Piping: Causes Total All Flexible Plastic Fiberglass
Total All Fiberglass Cause

Metal With Cathodic Protection
Total All Metal Flexible Plastic

Total

General Piping: Causes Of Release Corrosion Versus

Metal Piping: Causes Of Release Corrosion Versus

Corrosion Versus Fiberglass Piping: Single Wall Versus Double Wall

Fisher's Exact Test p-value: Fisher's Exact Test p-value: Fisher's Exact Test p-value: Fisher's Exact Test p-value:

Fisher's Exact Test p-value: Fiberglass Pipes: Causes Of Release

Appendix C C-6Extent Of Contamination By Source, Media

Local Large Unknown Total Media Soil 44 5 5 54 Water 25 37 4 66 Unknown 11 2 56

Total 80 44 Soil 79 6 1 86 Water 10 14 2 26 Unknown 29 5 43

Total 118 25 Soil 18 10 3 31 Water 11 21 2 34 Unknown 8 0 16

Total 37 31 Soil 9 0 0 9 Water 5 3 1 9 Unknown 1 0 6

Total 15 3 Soil 2 0 0 2 Water 2 1 0 3 Unknown 0 0 2

Total 4 1 Soil 30 1 4 35 Water 9 12 1 22 Unknown 2 3 25

Total 41 16 295 120
Total Soil 217 Total Water 160 Note: For the purposes of this analysis, off-site releases were considered to be "large" Source Media Affected Extent Piping

Dispenser (Including Spills/Overfills)

Tank (8 cases where release was contained are not included in this table)

Others (Vent Line, Fill Pipe, Vapor Recovery) STP Area

Delivery Problem

Total Extent

Appendix C C-7Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt Media (1) Media (2) p1 p2 p1-p2 P 1-P 1/n z p - value Proportion Of Releases: Soil Versus Water For Each Source Piping Soil Versus Piping Water 0.450 0.550 -0.100 0.500 0.500 0.00833 2.19 0.03 Dispenser Soil Versus Dispenser Water 0.768 0.232 0.536 0.500 0.500 0.00893 11.34 0.00 Tank Soil Versus Tank Water 0.477 0.523 -0.046 0.500 0.500 0.01563 0.74 0.46 STP Area Soil Versus STP Area Water 0.500 0.500 0.000 0.500 0.500 0.05556 0.00 1.00 Others Soil Versus Others Water 0.400 0.600 -0.200 0.500 0.500 0.20000 0.89 0.37 Deliv. Prob. Soil Versus Deliv. Prob. Water 0.614 0.386 0.228 0.500 0.500 0.01754 3.44 0.00 All Soil Versus All Water 0.576 0.424 0.151 0.500 0.500 0.00265 5.87 0.00
Extent (1) Extent (2) p1 p2 p1-p2 P 1-P 1/n z p - value Proportion Of Releases: Local Versus Large Piping Local Versus Large 0.645 0.355 0.290 0.500 0.500 0.00806 6.47 0.00 Dispenser Local Versus Large 0.825 0.175 0.650 0.500 0.500 0.00699 15.55 0.00 Tank Local Versus Large 0.544 0.456 0.088 0.500 0.500 0.01471 1.46 0.15 STP Area Local Versus Large 0.833 0.167 0.667 0.500 0.500 0.05556 5.66 0.00 Other Local Versus Large 0.800 0.200 0.600 0.500 0.500 0.20000 2.68 0.01 Deliv. Prob Local Versus Large 0.719 0.281 0.439 0.500 0.500 0.01754 6.62 0.00 Total Local Versus Large 0.711 0.289 0.422 0.500 0.500 0.00241 17.18 0.00 Source (1) Source (2) p1 p2 p1-p2 P 1-P 1/n z p - value Dispenser 0.550 0.232 0.318 0.397 0.603 0.01726 4.95 0.00 Tank 0.550 0.523 0.027 0.541 0.459 0.02372 0.35 0.73 STP Area 0.550 0.500 0.050 0.543 0.457 0.06389 0.40 0.69 Others 0.550 0.600 -0.050 0.552 0.448 0.20833 0.22 0.83 Deliv. Prob. 0.550 0.386 0.164 0.497 0.503 0.02588 2.04 0.04 Tank 0.232 0.523 -0.291 0.339 0.661 0.02431 3.94 0.00 STP Area * 0.232 0.500 -0.268 0.269 0.731 0.06448 2.38 0.02 Others 0.232 0.600 -0.368 0.248 0.752 0.20893 1.86 0.06 Deliv. Prob. 0.232 0.386 -0.154 0.284 0.716 0.02647 2.10 0.04 STP Area 0.523 0.500 0.023 0.518 0.482 0.07094 0.17 0.86 Others 0.523 0.600 -0.077 0.529 0.471 0.21538 0.33 0.74 Deliv. Prob. 0.523 0.386 0.137 0.459 0.541 0.03293 1.52 0.13 Others 0.500 0.600 -0.100 0.522 0.478 0.25556 0.40 0.69 Deliv. Prob. 0.500 0.386 0.114 0.413 0.587 0.07310 0.86 0.39 Others Deliv. Prob. 0.600 0.386 0.214 0.403 0.597 0.21754 0.94 0.35 Source (1) Source (2) p1 p2 p1-p2 P 1-P 1/n z p - value Dispenser 0.361 0.175 0.186 0.260 0.740 0.01519 3.44 0.00 Tank 0.361 0.456 -0.095 0.395 0.605 0.02290 1.29 0.20 STP Area 0.361 0.167 0.194 0.336 0.664 0.06375 1.63 0.10 Others 0.361 0.032 0.328 0.294 0.706 0.04045 3.58 0.00 Deliv. Prob. 0.361 0.281 0.080 0.335 0.665 0.02574 1.06 0.29 Tank 0.175 0.456 -0.281 0.265 0.735 0.02170 4.32 0.00 STP Area 0.175 0.167 0.008 0.174 0.826 0.06255 0.09 0.93 Others 0.175 0.032 0.143 0.149 0.851 0.03925 2.02 0.04 Deliv. Prob. 0.175 0.281 -0.106 0.205 0.795 0.02454 1.67 0.09 STP Area * 0.456 0.167 0.289 0.395 0.605 0.07026 2.23 0.03 Others 0.456 0.032 0.424 0.323 0.677 0.04696 4.18 0.00 Deliv. Prob. 0.456 0.281 0.175 0.376 0.624 0.03225 2.01 0.04 Others 0.167 0.032 0.134 0.082 0.918 0.08781 1.66 0.10 Deliv. Prob. 0.167 0.281 -0.114 0.253 0.747 0.07310 0.97 0.33 Others Deliv. Prob. 0.032 0.281 -0.248 0.193 0.807 0.04980 2.82 0.00
Media/Extent (1) Media/Extent (2) p1 p2 p1-p2 P 1-P 1/n z p - value Soil Versus Water Releases Local To Soil Versus Local To Water 0.891 0.408 0.483 0.688 0.312 0.01175 9.61 0.00 LargeTo Soil Versus Large To Water 0.109 0.592 -0.483 0.312 0.688 0.01175 9.61 0.00

Fisher's Exact Test - STP Area Comparisons For Asterisks Above Configuration Water Yes Water No Configuration Large Yes Large No Dispenser 26 86 Tank 31 37 STP Area 9 9 STP Area 3 15 0.02 0.03 Tank Versus Dispenser Versus

Tank Versus

STP Area Versus

Proportion Of Large Releases - Source Comparison Piping Versus

Dispenser Versus

STP Area Versus Proportion Of Releases To Water - Source Comparison Piping Versus

Fisher's Exact Test p-value: Fisher's Exact Test p-value: marginally significant = significant = Value of N is low for z-test (N=18) = Value of N is low for z-test (N=5) = BOLD BOLD Note: Others - Small value of observations (N=5) makes all statistical tests somewhat unreliable.

Appendix C C-8Media And Extent Of Contamination For Suction And Pressure Piping Releases from piping, dispensers, and the STP area were included in this data. All spills/overfills were excluded.

Local Large Unknown Total Media Soil 18 2 0 20 Water 6 5 0 11 Unknown 1 1

Total 25 8 Soil 76 5 3 84 Water 29 29 5 63 Unknown 15 1

Total 120 35 Note: For the purposes of this analysis, off-site releases were considered to be "large" Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt Extent(1) Extent(2) p1 p2 p1-p2 P 1-P 1/n z p - value Suction Local Versus Pressure Local 0.758 0.774 -0.017 0.771 0.229 0.03675 0.21 0.84 Suction Large Versus Pressure Large 0.242 0.226 0.017 0.229 0.771 0.03675 0.21 0.84

Media(1) Media(2) p1 p2 p1-p2 P 1-P 1/n z p - value Suction Soil Versus Pressure Soil 0.645 0.571 0.074 0.584 0.416 0.03906 0.76 0.45 Suction Water Versus Pressure Water 0.355 0.429 -0.074 0.416 0.584 0.03906 0.76 0.45 significant = marginally significant = Pressure Piping Delivery Media Affected Extent
Suction

Appendix C C-9Methods Of Release Identification
Method Of Identification Number Of Releases Percent Leak Detection 100 16.8% Closure 76 12.8% Property Transfer 12 2.0% Visual Or Olfactory 279 47.0% Water In Tank 12 2.0% Other 89 15.0% Unknown 26 4.4% Total Known Method of ID 594 Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) Method (1) Method (2) p1 p2 p1-p2 P 1-P 1/n z p - value Leak Detection Versus Closure 0.168 0.128 0.040 0.148 0.852 0.002 2.77 0.01 Property Transfer 0.168 0.020 0.148 0.094 0.906 0.002 12.36 0.00 Visual Or Olfactory 0.168 0.470 -0.301 0.319 0.681 0.002 15.76 0.00 Water In Tank 0.168 0.020 0.148 0.094 0.906 0.002 12.36 0.00 Closure Versus Property Transfer 0.128 0.020 0.108 0.074 0.926 0.002 10.03 0.00 Visual Or Olfactory 0.128 0.470 -0.342 0.299 0.701 0.002 18.20 0.00 Water In Tank 0.128 0.020 0.108 0.074 0.926 0.002 10.03 0.00 Property Transfer Versus Visual Or Olfactory 0.020 0.470 -0.449 0.245 0.755 0.002 25.47 0.00 Water In Tank 0.020 0.020 0.000 0.020 0.980 0.002 0.00 1.00 Visual Or Olfactory Versus Water In Tank 0.470 0.020 0.449 0.245 0.755 0.002 25.47 0.00 significant = marginally significant =

Appendix C C-10Leak Detection Success Rate Evaluation

Leak Detection Method Opportunities To Dectect Leaks Proportion Of Opportunites Leaks Detected Proportion Detected Leaks Not Detected Proportion Not Detected Vapor 29 6% 10 34% 19 66% Groundwater 25 5% 8 32% 17 68% ATG 28 6% 8 29% 20 71% LTT 78 16% 20 26% 58 74% LLD 103 22% 25 24% 78 76% Interstitial 51 11% 12 24% 39 76% MTG 5 1% 1 20% 4 80% SIR 78 16% 15 19% 63 81% IC&TTT 76 16% 7 9% 69 91% Total 473 100% 106 22% 367 78%

LD Method Vapor Groundwater ATG LTT LLD Interstitial MTG SIR IC&TTT Total Vapor -- p=1.00 p= 0.77 p= 0.47 p= 0.34 p= 0.31 p=1.00 p= 0.12 p= 0.01 p= 0.20 Groundwater -- p=1.00 p= 0.61 p= 0.45 p= 0.58 p=1.00 p= 0.27 p= 0.01 p= 0.33 ATG -- p= 0.80 p= 0.63 p= 0.79 p=1.00 p= 0.30 p= 0.02 p= 0.60 LTT -- p= 0.86 p= 0.84 p=1.00 p= 0.44 p= 0.01 p= 0.63 LLD -- p=1.00 p=1.00 p= 0.47 p= 0.01 p= 0.78 Interstitial -- p=1.00 p=0 .66 p= 0.04 p= 0.99 MTG -- p=1.00 p= 0.41 p=1.00 SIR -- p= 0.11 p= 0.63 IC&TTT

-- p= 0.01 Total

--
Shading: = significant Typical STATISTICA Fisher's Exact Test, Chi-Squared Output (Vapor Versus ATG)

Frequencies, row 1 10 19 29 Percent of total 17.544% 33.333% 50.877% Frequencies, row 2 8 20 28 Percent of total 14.035% 35.088% 49.123% Column totals 18 39 57 Percent of total 31.579% 68.421% Chi-square (df=1) 0.23 p= .6312 V-square (df=1) 0.23 p= .6342 Yates corrected Chi-square 0.04 p= .8454 Phi-square 0.00404 Fisher exact p, one-tailed p= .4231 two-tailed p= .7771 McNemar Chi-square (A/D) 2.7 p= .1004 Chi-square (B/C) 3.7 p= .0543 Significance Of Differences In Detection Success Rates (p-values) 1

All p-values are calculated based on Fisher's Exact Test, except for bold values, which are Yates-corrected Chi-squared values;

Row Totals Column 2 Column 1

Appendix C C-11Leak Detection ID- some LD not designed to detect problem beyond tank and piping while GW and vapor could - these areas BLACKED out- LD method associated with component that leaked (e.g., TTT is for tank only, LTT for piping only) # LD ShouldMIR MTG SIR TTT LTT ATG Interstitital GW Vapor LLD Have CaughtSource Total LD ID'd ID Opp ID Opp ID Opp ID Opp ID Opp ID Opp ID Opp ID Opp ID Opp ID OppPiping162 57 3 31 8 39 19 65 2 22 3 12 4 12 24 84 162Dispenser113 2 0 15 1 1 1 1 0 1 0 1 19Tank83 24 3 20 1 3 4 18 1 14 7 23 9 18 0 3 0 3 83STP Area (Including LLD)25 4 1 6 1 12 0 4 1 4 1 1 0 4 0 10 25Piping And Dispenser14 2 0 2 0 4 0 4 1 1 0 3 0 0 0 0 1 6 14Tank And Piping13 1 0 2 0 2 1 3 0 1 0 4 0 4 0 4 0 2 0 2 0 3 13Vent Line2 11 10 0 1Fill Pipe3 11 10 0 1Vapor Recovery2 00 00 0 0Tank And Dispenser1 00 00 0 0 10 0 0 0 0 00 00 0 1S/O At Tank (Delivery)87 40 24 5 7S/O At Dispenser61 00 00 0 0S/O At Tank Or Dispenser14 42 22 2 4100 7 76 1 5 15 78 1 15 20 78 8 28 12 51 8 25 10 29 25 103 330Total Opportunities =473ID - Number of leak detection identificationsOpp = Opportunities to detect the problem6 releases had multiple methods of leak detection identificationOpportunities are greater than total that LD should have caught because some sources used multiple forms of release detectionOpportunites exclude 15 TTT cases because those are assumed to be part of 76 MIR -- this is a combination LD methodAppendix CC-12Shaded values are significant at p < 0.05

Use Releases Use Releases 0-5 yr 49 4 53 21 6-10 yr 64 6 59 27 11-15 yr 121 36 70 30 >15 120 38 52 42 N 354 84 234 120
Cumulative Distributions 0-5 yr 13.8% 4.8% 22.6% 17.5% 6-10 yr 31.9% 11.9% 47.9% 40.0% 11-15 yr 66.1% 54.8% 77.8% 65.0% >15 100.0% 100.0% 100.0% 100.0%
Differences 9.1% 5.1% 20.0% 7.9% 11.3% 12.8% 0.0% 0.0% M 20.0% 12.8% Chi-squared 10.88 5.18 p - value 0.00 0.08

Significance Of Difference In Use/Releases Less Than/Greater Than Ten Years (Fisher's Exact Test)
N <=10 113 10 112 48 N >10 241 74 122 72 P <= 10 32% 12% 48% 40% P > 10 68% 88% 52% 60% p -value 0.00 0.18

marginally significant = Releases Versus Age Of Tanks, Piping (All Designs, Construction Materials)

Kolmorgorov-Smirnov Test For Difference In Age Patterns (Chi-Squared Approximation)

significant = Tanks (All) Piping (All)

Tanks (All) Piping (All)

Appendix C C-13Tanks Column 1 Column 2 Totals Frequencies, row 1 113 10 123 Percent of total 25.799% 2.283% 28.082% Frequencies, row 2 241 74 315 Percent of total 55.023% 16.895% 71.918% Column totals 354 84 438 Percent of total 80.822% 19.178% Chi-square (df=1) 13.47 p= .0002 V-square (df=1) 13.44 p= .0002 Yates corrected Chi-square 12.5 p= .0004 Phi-square 0.03075 Fisher exact p, one-tailed p= .0001 two-tailed p= .0001 McNemar Chi-square (A/D) 7.72 p= .0055 Chi-square (B/C) 210.76 p=0.0000

Piping Column 1 Column 2 Totals Frequencies, row 1 112 48 160 Percent of total 31.638% 13.559% 45.198% Frequencies, row 2 122 72 194 Percent of total 34.463% 20.339% 54.802% Column totals 234 120 354 Percent of total 66.102% 33.898% Chi-square (df=1) 1.98 p= .1594 V-square (df=1) 1.97 p= .1600 Yates corrected Chi-square 1.68 p= .1956 Phi-square 0.00559 Fisher exact p, one-tailed p= .0976 two-tailed p= .1765 McNemar Chi-square (A/D) 8.27 p= .0040 Chi-square (B/C) 31.35 p= .0000 Example STATISTICA® Outputs (Use Versus Releases Greater/Less Than 10 Years)

Appendix C C-14Age Patterns Of Use, Release For Tank Designs, Construction MaterialsKolmorgorov-Smirnov Test For Difference In Age Patterns (Chi-Squared Approximation)Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases0-5 yr10 0 2 0 12 0 1 0 0 0 11 0 2 0 13 0 3 0 14 1 17 1 6 0 13 3 19 36-10 yr7 0 5 2 12 2 0 1 0 0 7 1 5 2 12 3 1 0 24 1 25 1 8 1 19 1 27 211-15 yr36 6 9 11 45 17 3 2 0 0 39 8 9 11 48 19 10 4 3 0 13 4 32 6 28 7 60 13>1560 25 0 0 60 25 20 2 0 0 80 27 0 0 80 27 2 2 0 0 2 2 36 9 2 0 38 9N 113 31 16 13 129 44 24 5 0 0 137 36 16 13 153 49 16 6 41 2 57 8 82 16 62 11 144 27Cumulative Distributions0-5 yr8.8% 0.0% 12.5% 0.0% 9.3% 0.0% 4.2% 0.0% -- -- 8.0% 0.0% 12.5% 0.0% 8.5% 0.0% 18.8% 0.0% 34.1% 50.0% 29.8% 12.5% 7.3% 0.0% 21.0% 27.3% 13.2% 11.1%6-10 yr15.0% 0.0% 43.8% 15.4% 18.6% 4.5% 4.2% 20.0% -- -- 13.1% 2.8% 43.8% 15.4% 16.3% 6.1% 25.0% 0.0% 92.7% 100.0% 73.7% 25.0% 17.1% 6.3% 51.6% 36.4% 31.9% 18.5%11-15 yr46.9% 19.4% 100.0% 100.0% 53.5% 43.2% 16.7% 60.0% -- -- 41.6% 25.0% 100.0% 100.0% 47.7% 44.9% 87.5% 66.7% 100.0% 100.0% 96.5% 75.0% 56.1% 43.8% 96.8% 100.0% 73.6% 66.7%>15100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% -- -- 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%Differences8.8% 12.5% 9.3% 4.2% -- 8.0% 12.5% 8.5% 18.8% 15.9% 17.3% 7.3% 6.3% 2.1%15.0% 28.4% 14.1% 15.8% -- 10.4% 28.4% 10.2% 25.0% 7.3% 48.7% 10.8% 15.2% 13.4%27.5% 0.0% 10.3% 43.3% -- 16.6% 0.0% 2.8% 20.8% 0.0% 21.5% 12.3% 3.2% 6.9%0.0% 0.0% 0.0% 0.0% -- 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%M 27.5% 28.4% 14.1% 43.3% -- 16.6% 28.4% 10.2% 25.0% 15.9% 48.7% 12.3% 15.2% 13.4%Chi-squared 7.38 2.31 2.59 3.11 -- 3.14 2.31 1.55 1.09 0.19 6.65 0.82 0.87 1.64p - value 0.02 0.32 0.27 0.21 -- 0.21 0.32 0.46 0.58 0.91 0.04 0.66 0.65 0.44Significance Of Difference In Use/Releases Less Than/Greater Than Ten Years (Fisher's Exact Test)N <=10 17 0 7 2 24 2 1 1 0 0 18 1 7 2 25 3 4 0 38 2 42 2 14 1 32 4 46 5N >10 96 31 9 11 105 42 23 4 0 0 119 35 9 11 128 46 12 6 3 0 15 6 68 15 30 7 98 22P <= 10 15% 0% 44% 15% 19% 5% 4% 20% -- -- 13% 3% 44% 15% 16% 6% 25% 0% 93% 100% 74% 25% 17% 6% 52% 36% 32% 19%P > 10 85% 100% 56% 85% 81% 95% 96% 80% -- -- 87% 97% 56% 85% 84% 94% 75% 100% 7% 0% 26% 75% 83% 94% 48% 64% 68% 81%p -value 0.02 0.13 0.02 0.32 -- 0.13 0.13 0.10 0.54 1.00 0.01 0.29 0.52 0.25Significant =Example STATISTICA® Output (Use Versus Releases Greater/Less Than 10 Years, Steel w/CP , SW)RowColumn 1 Column 2 TotalsFrequencies, row 1 17 0 17Percent of total 11.806% 0.000% 11.806%Frequencies, row 2 96 31 127Percent of total 66.667% 21.528% 88.194%Column totals 113 31 144Percent of total 78.472% 21.528%Chi-square (df=1) 5.29 p= .0215V-square (df=1) 5.25 p= .0219Yates corrected Chi-square 3.94 p= .0471Phi-square 0.03672Fisher exact p, one-tailed p= .0122two-tailedp= .0237McNemar Chi-square (A/D) 3.52 p= .0606Chi-square (B/C) 94.01 p= .0000Steel w/CP (SW) Steel w/CP (DW) Steel w/CP (All) Steel w/Lining (SW)Composite (All)All SteelDW SteelSW SteelSteel W/Lining (DW) Composite (SW) Composite (DW)SW Steel DW Steel All SteelFiberglass (SW) Fiberglass (DW) Fiberglass (All)Steel w/CP (SW) Steel w/CP (DW) Steel w/CP (All) Steel w/Lining (SW) Steel W/Lining (DW) Composite (SW) Composite (DW) Composite (All)Fiberglass (SW) Fiberglass (DW) Fiberglass (All)Appendix CC-15Age Patterns Of Use, Releases For Piping Designs, Construction MaterialsKolmorgorov-Smirnov Test For Difference In Age Patterns (Chi-Squared Approximation)Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases Use Releases0-5 yr1 0 0 0 1 0 1 0 26 3 27 3 12 14 13 4 25 186-10 yr1 2 0 0 1 2 1 1 22 4 23 5 23 13 12 7 35 2011-15 yr14 5 1 0 15 5 1 0 2 0 3 0 35 14 17 11 52 25>1522 25 1 0 23 25 0 0 1 0 1 0 24 14 4 3 28 17N 38 32 2 0 40 32 3 1 51 7 54 8 94 55 46 25 140 80Cumulative Distributions0-5 yr2.6% 0.0% 0.0% -- 2.5% 0.0% 33.3% 0.0% 51.0% 42.9% 50.0% 37.5% 12.8% 25.5% 28.3% 16.0% 17.9% 22.5%6-10 yr5.3% 6.3% 0.0% -- 5.0% 6.3% 66.7% 100.0% 94.1% 100.0% 92.6% 100.0% 37.2% 49.1% 54.3% 44.0% 42.9% 47.5%11-15 yr42.1% 21.9% 50.0% -- 42.5% 21.9% 100.0% 100.0% 98.0% 100.0% 98.1% 100.0% 74.5% 74.5% 91.3% 88.0% 80.0% 78.8%>15100.0% 100.0% 100.0% -- 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%Differences2.6% -- 2.5% 33.3% 8.1% 12.5% 12.7% 12.3% 4.6%1.0% -- 1.3% 33.3% 5.9% 7.4% 11.9% 10.3% 4.6%20.2% -- 20.6% 0.0% 2.0% 1.9% 0.1% 3.3% 1.3%0.0% -- 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%M 20.2% -- 20.6% 33.3% 8.1% 12.5% 12.7% 12.3% 4.6%Chi-squared 2.84 -- 3.03 0.33 0.16 0.44 2.23 0.97 0.44p - value 0.24 -- 0.22 0.85 0.92 0.80 0.33 0.61 0.80Significance Of Difference In Use/Releases Less Than/Greater Than Ten Years (Fisher's Exact Test)N <=102 2 0 0 2 2 2 1 48 7 50 8 35 27 25 11 60 38N >10 36 30 2 0 38 30 1 0 3 0 4 0 59 28 21 14 80 42P <= 10 5% 6% 0% -- 5% 6% 67% 100% 94% 100% 93% 100% 37% 49% 54% 44% 43% 48%P > 10 95% 94% 100% -- 95% 94% 33% 0% 6% 0% 7% 0% 63% 51% 46% 56% 57% 53%p -value 1.00 -- 1.00 1.00 1.00 1.00 0.17 0.46 0.57Significant =Example STATISTICA® Output (Use Versus Releases Greater/Less Than 10 Years, Fiberglass, SW)RowColumn 1 Column 2 TotalsFrequencies, row 135 27 62Percent of total23.490% 18.121% 41.611%Frequencies, row 259 28 87Percent of total39.597% 18.792% 58.389%Column totals94 55 149Percent of total63.087% 36.913%Chi-square (df=1)2.01 p= .1565V-square (df=1)1.99 p= .1579Yates corrected Chi-square1.55 p= .2132Phi-square0.01347Fisher exact p, one-tailedp= .1068two-tailedp= .1716McNemar Chi-square (A/D)0.57 p= .4497Chi-square (B/C)11.17 p= .0008Metal w/CP (SW) Metal w/CP (DW) Metal w/CP (All) Flexible Plastic (SW) Flexible Plastic (DW) Flexible Plastic (All) Fiberglass (SW) Fiberglass (DW) Fiberglass (All)Steel w/CP (SW) Steel w/CP (DW) Steel w/CP (All) Flexible Plastic(SW) Flexible Plastic(DW) Flexible Plastic (All) Fiberglass (SW) Fiberglass (DW) Fiberglass (All)Appendix CC-16Comparison Of Piping Types <10 Years Old And Piping Types >10 Years Old

Material Number In Data Set 1 Proportion In Data Set Number Of Releases Proportion Of Releases
Metal w/CP 2 1.8% 2 4.2% Flexible Plastic 50 44.6% 8 16.7% Fiberglass 60 53.6% 38 79.2% Total 112 48 Single Wall 39 34.8% 30 62.5% Double Wall 73 65.2% 18 37.5%
Metal w/CP 38 31.1% 30 41.7% Flexible Plastic 4 3.3% 0 0.0% Fiberglass 80 65.6% 42 58.3% Total 122 72 Single Wall 96 78.7% 58 80.6% Double Wall 26 21.3% 14 19.4% 1. Excludes records with piping releases Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt p1 (Use) p2 (Releases) p1-p2 P 1-P 1/n z p - value
Metal w/CP 1.8% 4.2% -2.4% 2.5% 97.5% 0.030 0.88 0.38 Flexible Plastic 44.6% 16.7% 28.0% 36.3% 63.8% 0.030 3.37 0.00 Fiberglass 53.6% 79.2% -25.6% 61.3% 38.8% 0.030 3.05 0.00 Single Wall 34.8% 62.5% -27.7% 43.1% 56.9% 0.030 3.24 0.00 Double Wall 65.2% 37.5% 27.7% 56.9% 43.1% 0.030 3.24 0.00
Metal w/CP 31.1% 41.7% -10.5% 35.1% 64.9% 0.022 1.48 0.14 Flexible Plastic 3.3% 0.0% 3.3% 2.1% 97.9% 0.022 1.55 0.12 Fiberglass 65.6% 58.3% 7.2% 62.9% 37.1% 0.022 1.01 0.31 Single Wall 78.7% 80.6% -1.9% 79.4% 20.6% 0.022 0.31 0.76 Double Wall 21.3% 19.4% 1.9% 20.6% 79.4% 0.022 0.31 0.76 significant = marginally significant = Piping >10 Years Old Piping <10 Years Old

Piping >10 years old

Piping <10 Years Old

Appendix C C-17Comparison Of Tank Types <10 Years Old And Tank Types >10 Years Old

Material Number In Data Set 1 Proportion In Data Set Number Of Releases Proportion Of Releases
Steel 25 22.1% 3 30.0% Composite 42 37.2% 2 20.0% Fiberglass 46 40.7% 5 50.0% Total 113 10 Single Wall 36 31.9% 2 20.0% Double Wall 77 68.1% 8 80.0%
Steel 128 53.1% 46 62.2% Composite 15 6.2% 6 8.1% Fiberglass 98 40.7% 22 29.7% Total 241 74 Single Wall 199 82.6% 56 75.7% (Yates-corrected Chi2) Double Wall 42 17.4% 18 24.3% 1. Excludes records with piping releases Calculation of z-statistics: z = (p1 - p2) / sqrt (P * (1-P) * (1 / n)) where 1/n = 1/n1+1/n2 if proportions are independe nt p1 (Use) p2 (Releases) p1-p2 P 1-P 1/n z p - value
Steel 22.1% 30.0% -7.9% 22.8% 77.2% 0.109 0.57 0.57 Composite 37.2% 20.0% 17.2% 35.8% 64.2% 0.109 1.09 0.28 Fiberglass 40.7% 50.0% -9.3% 41.5% 58.5% 0.109 0.57 0.57 Single Wall 31.9% 20.0% 11.9% 30.9% 69.1% 0.109 0.78 0.44 Double Wall 68.1% 80.0% -11.9% 69.1% 30.9% 0.109 0.78 0.44
Steel 53.1% 62.2% -9.1% 55.2% 44.8% 0.018 1.37 0.17 Composite 6.2% 8.1% -1.9% 6.7% 93.3% 0.018 0.57 0.57 Fiberglass 40.7% 29.7% 10.9% 38.1% 61.9% 0.018 1.69 0.09 Single Wall 82.6% 75.7% 6.9% 81.0% 19.0% 0.018 1.32 0.19 Double Wall 17.4% 24.3% -6.9% 19.0% 81.0% 0.018 1.32 0.19 Tank <10 years old

Tank >10 years old

Tank <10 Years Old 0.51 0.81 0.73 0.77

Note: The Fisher's Exact Test for fiberglass tanks >10 years old shows no statistical difference while the z-test shows a margi nal difference. Fisher's Exact Test p-value

0.33 0.74 0.30 0.60 0.73 0.71

Tank >10 Years Old

(see Fisher's Exact Tests above) significant = marginally significant = BOLD Value of N is low for z-test (N=10) =

Appendix C C-18