$0.017
                                                                           $0.0
UST systems with Field-Constructed Tanks (FCTs)
                                                                            $11
                                                                         $0.066
                                                                           $0.0
Cost to Owners/Operators to Read Regulation
                                                                           $5.5
                                                                           $5.5
                                                                           $5.5
State Government Administrative Costs [d]
                                                                          $0.12
                                                                          $0.12
                                                                          $0.12
Total Annual Compliance Costs e
                                                                           $160
                                                                           $290
                                                                            $70
[a] Cost estimates were derived using a seven percent discount rate.
[b] Compliance costs include direct compliance costs and state oversight costs. For this regulatory impact analysis, direct compliance costs and state oversight costs provide a reasonable proxy to assess the final UST regulation's social costs. See Chapter 3.1 for further discussion.
[c] Conventional UST systems include all systems that are not AHFDSs, FCTs, or EGTs.
[d] The costs for UST systems directly owned or operated by local, state, and federal government entities are included in the estimates of compliance costs within the other categories. Costs shown here reflect the administrative costs for state governments to read the regulation, apply for state program approval, process notifications of ownership changes, and process one-time notifications of EGT, AHFDS, and FCT existence.
[e] Totals may not add up due to rounding.

Under the alternative baseline universe assumption described in Section 3.3.1, EPA estimates that the Selected Option for the final UST regulation will produce incremental compliance costs of approximately $155 million per year compared to $156 million in annual costs in the primary analysis; the results of both the primary and alternative scenario round to $160 million in total annual social costs. Under Alternative 1, the alternative baseline universe assumption yields an estimate of approximately $286 million per year in incremental compliance costs, compared to $287 million in the primary analysis; the results in both the primary and alternative scenarios round to $290 million in total annual social costs. Similarly, under Alternative 2, total annual social costs are approximately $70 million in both the alternative baseline scenario and the primary analysis.
Limitations of Compliance Cost Analysis
While EPA has taken steps to present a sound analysis of compliance costs, it recognizes that certain assumptions and limitations are inherent to this assessment.
Tank configuration: This analysis assumes that a particular configuration of equipment represents the average UST system. This assumption affects the compliance costs of the final UST regulation because systems with different configurations (e.g., more sumps per tank) could have different costs. Mischaracterizing this configuration may under- or overstate total costs as well as system-level costs.
System-level compliance costs: As discussed in Section 3.3, system-level compliance costs are based on public information, input from UST industry professionals, and EPA professional judgment, all of which are assumed to provide the most accurate available data at the time of this regulatory action. EPA recognizes that these data sometimes reflect only a small number of sources, and are therefore characterized by uncertainty.
As a result of these uncertainties, the precise cost of the final UST regulation may differ from the estimate generated by EPA's analysis. The above sensitivity analyses, though not strictly additive, suggest that the outside range of cost uncertainty is less than 35 percent from EPA's central estimates. Moreover, because EPA's estimate is framed by a number of conservative assumptions (outlined in section 3.3), it is unlikely that this analysis understates the costs of the final UST regulation significantly.

 Chapter 4.	Assessment of Cost Savings and Benefits

4.1	Introduction
      The beneficial impacts of a regulatory change are typically measured in one of two ways: as "social benefits" or as avoided costs. Social benefits usually take the form of reduced environmental damage, reduced human health risk, and improvements in the value of environmental amenities. Benefits also include avoided costs associated with reduced need for cleanup and avoided costs of "averting behavior" (e.g., obtaining replacement water supplies). Ideally, social benefits reflect accurate measures of the total "willingness to pay" (WTP) of consumers to obtain improvements in environmental quality. In other cases, avoided costs (e.g., medical care) can be used to inform proxy estimates of WTP when direct estimates of WTP are unavailable. In the context of this regulation, EPA considers the avoided costs associated with reduced need for remediation (cleanup) of releases because avoided costs represent a real economic cost savings, and because reliable WTP estimates for the value of an avoided cleanup are not available. While avoided costs, or cost savings, could be subtracted from total costs and reported in Chapter 3, they do not typically accrue to the same parties that incur compliance costs. Therefore, for clarity of presentation, we examine them with other benefits and beneficial impacts in this chapter.
      This chapter describes the approaches used to evaluate avoided remediation costs and other benefits. It first outlines several different methods attempted for measuring benefits and cost savings in the context of the proposed regulation, and describes the final selected method (expert consultation) in detail. Next, it provides a description of monetized cost savings, including avoided cleanup costs, avoided vapor damage cleanup estimates, and avoided product loss associated with anticipated reductions in releases and reductions in severity of releases. The chapter then presents a screening-level analysis of the quantity of groundwater potentially protected by the regulation. Finally, we provide a qualitative discussion of ecological, human health, and other social benefits.
4.2	Investigation of Empirical Methods for Measuring Cost Savings
	The cost savings of the final UST regulation result from the reduced incidence and size of releases that would occur due to the new requirements. EPA examined a number of ways to use quantitative, empirical data on release rates, inspection effectiveness, and program performance to directly estimate the changes in releases that could be expected under the final UST regulation. This section describes the different data sources and methods considered, and the limitations of each.
4.2.1	Engineering Estimates and Literature
	One approach to estimating the benefits of this regulation would be to develop an engineering model of the release rates associated with equipment and practices before and after the implementation of the regulation requirements. However, this approach would address only a small number of the final UST regulation components because most of the requirements are not focused on equipment modifications, but instead call for inspections, testing, and maintenance. These are requirements for changes in human behavior, and are not easily measured using equipment testing.
	This suggests that EPA could best measure benefits empirically by examining studies of how release rates change in response to more frequent inspection and testing. Therefore, in the context of the proposed regulation, EPA conducted a targeted review of engineering literature and studies on the effectiveness of testing and inspection programs. While we were unable to identify any studies directly applicable to the proposed UST regulation, we did identify several studies that examined the effects of better inspection and testing rates more generally. We summarize three key studies below.
   *       California study of impact of secondary containment on UST system releases (2002): This study examined whether use of secondary containment throughout UST systems resulted in differences in release rates. The study's conclusions were hampered by a limited sample size, and authors note that releases from other parts of the systems may have affected results. The study did not find a significant relationship between secondary containment and release rates at sites, but did find that facility-level factors (e.g., improper installations) made it more likely than expected that all systems at a facility would either have or lack releases. While the study cannot be used to directly estimate the benefits associated with the proposed or final UST regulation, its conclusions suggest that regulations focusing on effective facility-level inspections may be well-targeted.
   *       National Research Council study of effectiveness of state vehicle emissions inspection and maintenance programs (2001): This study reviewed four state programs and one city program aimed at reducing motor vehicle emissions by requiring inspections and maintenance. While the study did not address UST systems, the structure of vehicle inspection programs is similar to the UST regulation in that both require owners/operators to undertake routine inspections and perform maintenance as needed. The study found that the programs had a measureable impact on ambient air quality, but did not identify whether the differences were statistically significant. The results do not provide a quantitative basis for estimating the impacts of the final UST regulation, but the study suggests that mandatory inspection programs can reduce emissions.

   *       Environmental Results Program (ERP) data: Data from several environmental results programs (ERPs) show a statistically significant improvement in verified compliance as a result of a combination of self-certification, technical assistance, and inspections. While these programs do not isolate the impact of specific regulatory changes, the results are consistent with other findings that programs that rely in part on self-implemented inspections and reporting can reduce noncompliance.
In general, the literature does not address UST inspection programs directly, and does not provide quantitative results that can be used to estimate the impacts of the final UST regulation. However, the literature does provide data that generally indicate that self-implementing inspection programs (with external validation) do have an impact on equipment maintenance, and generally lead to a reduction in environmental impacts. This suggests that some positive impact should be expected from the final UST regulation.
4.2.2	Statistical Analysis of State Release Data
	A different approach to a robust analysis of benefits would be to develop a database of state UST regulations and reported release rates before and after the effective dates of regulations similar to the final UST regulation. With good quality data, it is possible to combine these regulations and reported release rates, and isolate the marginal impacts of various components of the final UST regulation. To collect detailed data at the facility level, however, would require visiting state UST programs individually and collecting detailed site inspection data from state case files and archives. Not only would such an effort be prohibitive in terms of available resources, but our current knowledge of the state programs suggests that variable inspection practices and changes in record-keeping practices over time may limit the ability of the exercise to provide robust results.
	In the absence of site-specific data, however, we collected and examined data on state regulatory programs and reported releases from available aggregate sources at the time of the proposed regulation. Specifically, we identified and evaluated data from the following sources:

   *       Leak Autopsy Reports: In 2004 and 2005, EPA released two draft "leak autopsy" studies ("the draft 23-state Autopsy Report" and a separate study examining the State of Florida). These studies examined the sources and extent of releases that occurred in systems that were compliant with the 1998 standards, and identifies the extent to which different baseline releases are associated with failures of equipment in different parts of the UST system (e.g., piping, overfill protection equipment).
   *       State Regulatory and Report Data: State programs are required to report aggregated information to EPA on the number of active UST systems, the number of inspections, and the number of confirmed releases reported in each six-month period. In addition, EPA obtained information about state regulatory programs and the effective dates for state requirements that are similar to the requirements of the proposed regulation.
      Using the available data, EPA examined several different statistical approaches, focusing on regression analysis, to compile and examine a set of state-level data that included the number of UST systems in each state in a given year, the number of releases from UST systems in each year, the number of UST inspections conducted in each year, and the presence or absence of regulations designed to prevent releases.
      Before conducting regression analysis on the data set of state USTs and releases, EPA first adjusted the data to account for a number of data quality concerns. Of particular concern was the relationship between states with low-frequency inspections and states reporting small numbers of confirmed releases. To ensure that the reported UST releases accurately reflected most or all releases taking place, EPA developed an index that scored each state based on the frequency of inspections. States that reported inspection rates less frequent than every five years, and/or inconsistent inspection frequencies over time, were removed from the sample, based on the assumption that release data from those states may be less reliable due to less frequent third party verification (i.e., state inspection) of system operations. In other words, we assume that owners/operators may be less inclined to report releases or properly maintain their equipment if they are in a state where inspections occur infrequently or inconsistently.
      In conducting the analysis, however, EPA identified several fundamental problems with the available data, further limiting the value of a regression analysis approach. These include significant data availability and reliability issues related to the limited number of observations and programmatic changes among states that prevent the isolation of regulation-related impacts. Specifically:

      *       Consistent, accurate release data are not available. It is likely that measurement error exists in the recording of confirmed releases across states (the dependent variable) and that it is related in some systematic way to the regulatory structure of the state or other explanatory variables (as opposed to random reporting error) in the analysis. In addition, state inspections vary in timing and focus across states; this, in turn, affects the consistency of third-party verified compliance and release information. While EPA attempted to account for this by selecting only states with a high frequency of inspections for inclusion in the analysis, the interaction between inspection frequency and degree and effectiveness of regulation creates sample selection problems (i.e., states with higher release rates due to limited regulation may also be states that do not conduct frequent inspections and therefore have less reliable data). Therefore, normal regression properties do not hold, and results may be biased in ways that do not allow for a reliable interpretation.
      *       Many regulations consistent with the proposed UST regulation are currently in place in only a small number of states. EPA addressed limited variation in the presence of regulations by dropping several regulatory variables from the analysis, but the resulting lack of variation and the small number of observations make it likely that regulatory indicators will proxy for other relevant characteristics of that state.
      *       Study design is limited by available data. Ideally, an analysis of the effectiveness of UST leak prevention regulations would employ observations from a large number of states over a time period that includes years before and after regulations were in place. Such "panel" data would allow for identification of impacts temporally and spatially. Panel data would also allow for fixed-effects estimation, which controls for any unobserved characteristics of states that might affect release rates (such as soil pH or climate), independent of any effect of regulation. Available data superficially appear to be panel data, since they provide information on the number or rate of releases from different states in multiple time periods, along with information on the presence or absence of UST regulations by state. However, for many regulations it is unclear both when the regulation was first promulgated and when the effects of the regulation would be expected to be fully realized (e.g., through inspections).
      As discussed in more detail in Appendix F, quantitative analysis of annual UST releases by state did not reveal a consistent measure of the potential impact of release prevention regulations. The data limitations noted above prevented the use of the preferred method of fixed effects estimation using panel data. In the absence of fixed-effects estimation, the analysis cannot reliably draw conclusions about the impacts of regulations on releases, independent of any unmeasured characteristics of states that could be affecting the number of releases in each state. In other words, in addition to data quality issues discussed above, the small number of states with specific UST release prevention regulations prevents identification of robust relationships between individual regulations and the number of releases per year.
      However, through cross-sectional analysis, EPA was able to estimate that release rates in California and Florida  -  two states with mature UST regulation regimes  -  were about 55-65 percent less than one would expect based on release rates at other states during the time period examined. This difference could serve as an upper bound for the potential of leak prevention regulations to reduce the rate of UST releases.
4.3	Final Methodology for Assessment of Positive Impacts: Expert Consultation
      In the absence of applicable engineering models and limited empirical state data, we resorted to a consultation with four experts with experience in regulation of USTs and implementation of state inspection programs to estimate the individual effects of each regulatory change. The remainder of this chapter describes in detail the final methodology used to identify reductions in releases associated with the final UST regulation, and the calculation of cost savings associated with those avoided releases.
      For the proposed regulation, to ensure that the assessment of regulatory effects relied on broad expertise in regulatory implementation, EPA developed a pool of technical experts with national reputations for leadership in implementation of underground storage tank regulatory programs, or with extensive expertise in assessing spill causation at UST sites. From this pool, several experts were interviewed and five experts were identified. Each of these identified experts has over 20 years of experience in the regulation, assessment, and/or remediation of underground storage tanks, including direction of state programs and implementation of regulations similar to some aspects of the proposed regulation. One of the five experts did not provide input consistent with EPA's analytical methods, and as a result his quantitative estimates were not usable for the evaluation of the proposed regulation. As a result, for the final UST regulation, EPA consulted the remaining four experts to evaluate avoided costs.
      EPA provided an identical set of written questions separately to each expert and conducted individual follow-up telephone interviews to clarify and verify responses. Appendix G provides a detailed explanation of the process EPA followed in identifying experts, more detailed information about the qualifications of the experts, the questions distributed to experts, and an explanation of the factors EPA considered when including and excluding expert feedback. Appendix H provides the experts' responses to EPA's questions.
      Avoided Costs as a Measure of Beneficial Impacts
      Avoided remediation costs represent the key beneficial impacts associated with the regulations. Avoided remediation costs represent cost savings that accrue to owners, operators and public entities charged with remediating releases at regulated facilities. While avoided remediation costs are not a direct measure of total willingness to pay for environmental improvements, and are therefore not equivalent to social benefits, they represent real cost savings due to reduced demand for baseline remediation.
Calculation of Annual Positive Impacts
The analysis presents the positive effects of the final UST regulation as a constant, recurring, annual value for analytical convenience. The timing of the positive impacts of the regulation is uncertain for several reasons:
   *       As shown in Exhibit 1-2 in Chapter 1, the regulatory changes do not take effect simultaneously.
   *       Irrespective of when they take effect, the changes may require varying lengths of time to achieve full effect.
   *       EPA relies on its reported confirmed releases to calculate the reductions due to the final UST regulation. Confirmed releases recorded in a particular evaluation year vary significantly in severity and length of time undetected, which introduces variability in the extent to which costs are avoided each year.
   *       The final UST regulation includes activities such as: frequent inspections and equipment testing to prevent, identify and address releases; near-term shifts in technology; and long-term changes in technology. Each class of changes necessarily focuses on release avoidance and mitigation over different time horizons.

In the absence of detailed data characterizing releases by age and type, EPA assumes that implementation of the final UST regulation will have a uniform annual impact, with beneficial impacts realized on the last day of the year in which costs are incurred (i.e., a one-year delay). For equipment that is phased in over a period of time, we assume that positive impacts accrue at the same rate as installation and adjust those impacts so that they are constant over time, maintaining the one-year delay.
4.3.1	Avoided Remediation Costs
      This section explains how EPA arrives at its estimates of avoided remediation costs. EPA first explains how it calculates avoided remediation costs based on the source of a release. This is followed by a discussion of the methods used to calculate the number of releases avoided and the number of releases for which severity is mitigated. Finally, the two elements are combined to estimate the total avoided remediation cost due to the final UST regulation.
4.3.2	Calculating Avoided Remediation Costs
      This analysis values avoided releases according to their cost of remediation. EPA developed average remediation costs for the four general release size categories reported in the draft 23-state Autopsy Report. The four categories generally conform with classification conventions used by state LUST offices, and the autopsy reports presented leak frequency data for different UST system components for each of the categories. The four categories include:
*       Local site extent with soil contamination;
*       Local site extent with water contamination;
*       Large site extent with soil contamination; and
*       Large site extent with water contamination.

       EPA obtained remediation costs aligned with each of these size categories from a survey of state LUST offices and calculated average expected remediation costs for each of the release categories outlined in the draft 23-state Autopsy Report (Exhibit 4-1). Remediation costs associated with groundwater remediation are generally higher than costs for soil remediation. Administrative, response, and oversight costs were provided by New Hampshire, and remediation costs reflect an average of the costs provided by New Hampshire and Utah.,

Exhibit 4-1
                   REMEDIATION COSTS BY RELEASE EXTENT[a, b]
                           Remediation Cost Category
                       Site Size And Contamination Type

                            Small extent, soil only
                            Large extent, soil only
                                    Small
                                   extent,
                           Groundwater Contamination
                                    Large
                       extent, Groundwater Contamination
Typical administrative cost (public notification, fines, fees, etc)[c]
                                                                            $0
                                                                            $0
                                                                          $500
                                                                        $3,700
Typical response cost (e.g., alerting and sending personnel, assessments and planning, immediate actions to stop the release)[c]
                                                                       $10,000
                                                                       $10,000
                                                                       $10,000
                                                                       $10,000
Typical remediation cost[d]
                                                                       $14,800
                                                                      $103,000
                                                                       $98,500
                                                                      $409,500
Typical oversight cost (e.g., monitoring)[c]
                                                                          $500
                                                                        $1,000
                                                                        $1,500
                                                                        $5,000
Total typical cost per LUST category
                                                                       $25,300
                                                                      $114,000
                                                                      $110,500
                                                                      $428,200
Notes:
[a] Costs shown are one-time costs associated with a site remediation and have been rounded to the nearest hundred dollars.
b Costs are presented here in 2008 dollars. EPA inflates these costs to 2012 dollars for use in the analysis.
[c] The costs presented for administrative, response, and oversight costs are based on New Hampshire data only.
[d] The remediation costs shown represent the average costs from data provided by New Hampshire and Utah. Although New Mexico also reported costs, we excluded it for two reasons. First, groundwater cleanup cost estimates from New Mexico are much higher than those for other states ($2.5 million compared with $0.6 million or less for other states) but the state did not provide data on the number or type of sites that resulted in this high estimate of costs. Second, New Mexico has a relatively small number of UST systems (3,773 UST systems as of fiscal year 2013). As a result, New Mexico's costs may be atypical and could skew results to overstate avoided costs.
Sources:
1.	New Hampshire Department of Environmental Services, Underground Storage Tank Program, November 18, 2008.
2.	Utah Department of Environmental Quality, Underground Storage Tank Program, November 18, 2008.

      EPA then used the average cost data from states to develop weighted average costs associated with remediation of releases from different portions of the UST system, based on release frequency data for each source. Exhibit 4-2 presents, for each of the release sources identified in the draft 23-state Autopsy Report, the probability of a release by LUST category. Using the cost data from Exhibit 4-1, inflated to 2012 dollars, EPA estimates a weighted average avoided cost per release size by multiplying the cost per site by the probability of each release type. These are summed across the categories to obtain the weighted average cost by release source.,  The following section describes how this information is used to generate an estimate of incremental avoided costs.

Exhibit 4-2

Probability And Weighted Average Of Avoided Costs Per Release Source And Extent
           Release Source (as identified in 23-state Autopsy Report)
                            Small extent, soil only
                   Small extent, groundwater contamination
                           Large extent, soil only
                    Large extent, groundwater contamination
                            Total/ Weighted Average
Piping
                                                                    Probability
                                                                          40.5%
                                                                          22.0%
                                                                           4.5%
                                                                          33.0%
                                                                         100.0%

                                                                          Cost
                                                                       $10,900
                                                                       $25,900
                                                                        $5,500
                                                                      $150,700
                                                                      $193,000
Dispenser
                                                                    Probability
                                                                          71.6%
                                                                           9.7%
                                                                           5.4%
                                                                          13.3%
                                                                         100.0%

                                                                           Cost
                                                                       $19,300
                                                                       $11,400
                                                                        $6,600
                                                                       $60,900
                                                                       $98,100
Tank
                                                                    Probability
                                                                          30.7%
                                                                          17.7%
                                                                          17.3%
                                                                          34.3%
                                                                         100.0%

                                                                          Cost
                                                                        $8,300
                                                                       $20,800
                                                                       $21,000
                                                                      $156,700
                                                                      $206,800
STP Area
                                                                    Probability
                                                                          50.0%
                                                                          31.0%
                                                                           0.0%
                                                                          19.0%
                                                                         100.0%

                                                                          Cost
                                                                       $13,500
                                                                       $36,500
                                                                            $0
                                                                       $86,800
                                                                      $136,700
Delivery Problems
                                                                    Probability
                                                                          59.2%
                                                                          16.8%
                                                                           1.8%
                                                                          22.2%
                                                                         100.0%

                                                                          Cost
                                                                       $15,900
                                                                       $19,800
                                                                        $2,200
                                                                      $101,500
                                                                      $139,400
Note: Costs shown have been rounded to the nearest hundred dollars. Costs have been inflated to 2012 dollars.
Sources:
1.	U.S. EPA, Evaluation of Releases from New and Upgraded Underground Storage Tanks (Draft). 2004. ("23-state Autopsy Report")
2.	New Hampshire Department of Environmental Services, Underground Storage Tank Program, November 18, 2008.
3.	Utah Department of Environmental Quality, Underground Storage Tank Program, November 18, 2008.

4.4	Establishing Avoided Releases
      To estimate the number of baseline releases that would be either avoided completely or reduced in severity as a result of the final UST regulation, experts responded to a common set of questions about potential impacts of the regulatory changes under consideration and participated in subsequent individual discussions of specific areas of uncertainty.
      Each expert reviewed the requirements under consideration for the final UST regulation and estimated how they would affect the following dimensions of releases:
   1.       Changes in total frequency (number) of annual confirmed releases;
   2.       Changes in the number of remaining releases that reach groundwater; and/or
   3.       Changes in the average quantity released among remaining releases.
      Experts had the option of expressing reductions in release severity in terms of the percent reaching groundwater or volume (quantity) of product, depending on how they typically collected and reviewed release data. In addition, experts were given the option of expressing these changes either: 1) as a total national estimate that accounted for variation in existing regulation and technology among states and facilities, or 2) as a change applied to a specific subset of the tank universe (e.g., 10 percent change among tanks with a certain technology that are not currently regulated).
      Experts also estimated the sensitivity of results to changes in the frequency of regulatory requirements (e.g., the impact of inspections occurring at different intervals, consistent with different regulatory options) and noted synergies or dependencies between requirements, such as:
         * Dependency between equipment upgrades and walkthrough inspections: Experts consistently noted that simply replacing equipment with newer technologies (e.g., requiring that new systems have secondary containment) is insufficient for preventing all releases. Regular visual inspections are necessary to identify potential problems and ensure timely maintenance when a release has not yet occurred.
         * Synergy between equipment maintenance and walkthrough inspections: Experts noted that the combination of operability tests and visual (walkthrough) inspections would result in more avoided releases by identifying equipment problems quickly and ensuring effective maintenance.
         * Dependency between operator training and walkthrough inspections: Experts noted that training alone is not adequate to ensure effective site maintenance, and walkthrough inspection requirements are not effective without trained staff.
	Experts provided separate estimates of impacts for each regulatory requirement. EPA then used these requirement-specific estimates to calculate total avoided costs for the final UST regulation. It is important to note, however, that when considering relationships among regulatory requirements, experts differed in how they isolated and/or "allocated" impacts across specific requirements because the allocation of impacts across different regulatory requirements could potentially be interpreted in several ways (e.g., one expert might decide that inspections drove all impacts, while another might decide that testing was the primary factor). EPA therefore avoids emphasis on the requirement-specific estimates provided by each expert, and considers their results in total.

      In general, EPA applies the estimates presented by the experts to the number of affected units. In cases where reductions involved a range of values, EPA selected the midpoint of the range of values identified by each expert. Where experts' comments reflect qualitative assumptions that substantially affect their quantitative estimates, the analysis acknowledges those factors as caveats to estimated rates of release avoidance. If these assumptions assume regulatory language more stringent or significantly different than the final language, the analysis does not include any benefits for that requirement.
      To calculate the number of releases completely avoided as a result of potential regulatory changes, EPA combines the estimated reductions as identified by experts with a release distribution based on data from the draft 23-state Autopsy Report (see Appendix I for more detail). To estimate changes in release severity, the analysis uses the distribution of releases from the same report to quantify the number of groundwater releases avoided due to reduced release volume. Exhibit 4-3 provides a summary of our findings with respect to avoided releases. Experts' responses suggest that the Selected Option will avoid approximately nine percent to 50 percent of 6,128 annual releases, or roughly 560 to 3,000 releases in the first evaluation year. In addition, as summarized in Exhibit 4-4, of the remaining releases, approximately 210 to 900 releases would be reduced in severity (i.e., these releases would occur but instead of reaching groundwater they would remain soil contamination only).
Exhibit 4-3
                               Avoided Releases
                                    Expert
                                Selected Option
                                 Alternative 1
                                 Alternative 2
Expert 1
                                     1,100
                                     1,600
                                      590
Expert 2
                                      560
                                      690
                                      170
Expert 3
                                     1,600
                                     2,400
                                     1,200
Expert 4
                                     3,000
                                     3,700
                                     2,200
Average
(Range)
                                     1,600
                                  (560-3,000)
                                     2,100
                                  (690-3,700)
                                     1,000
                                  (170-2,200)
Note: See Appendices H and I for inputs and methods for calculating these values. Estimates were validated with experts to ensure they accurately capture their opinions.

Exhibit 4-4
                  Avoided Groundwater Contamination Incidents
                                    Expert
                                Selected Option
                                 Alternative 1
                                 Alternative 2
Expert 1
                                      900
                                     1,100
                                      620
Expert 2
                                      210
                                      460
                                      88
Expert 3
                                      320
                                      310
                                      280
Expert 4
                                      600
                                      480
                                      570
Average
(Range)
                                      510
                                   (210-900)
                                      600
                                  (310-1,100)
                                      390
                                   (88-570)
Note: See Appendices H and I for inputs and methods for calculating these values. Estimates were validated with experts to ensure they accurately capture their opinions.

4.4.1	Avoided Releases Using an Alternative Baseline
      EPA's primary analysis assumes that the universe of confirmed releases from UST systems remains constant over the time frame of the analysis. However, both the universe of UST systems and the release rate (defined as the number of confirmed releases divided by the number of UST systems in a given year) have declined over the last two decades. This is consistent with the regulatory context of the past 20 years, in which two key factors have been driving the number of releases. First, the universe of UST systems has been declining as older, smaller tanks have been replaced by newer, larger systems. Second, many of the confirmed releases reported in the 1990s and early 2000s were "legacy" releases associated with older systems that did not meet the technical standards under 40 CFR Part 280 (e.g., tanks that were installed prior to the promulgation of the UST regulation at 40 CFR Part 280). Many of these legacy releases are discovered when tanks are removed during property transactions and other development projects.
As the number of legacy releases has declined, the declining trend in total releases has "flattened"  -  trend data suggest that release rates have been approximately one confirmed release per hundred tanks in recent years. In addition, it is possible that confirmed releases may increase in future years, as UST systems continue to age, and as new fuel blends with potentially higher corrosivity are introduced into the industry. Given this uncertainty, EPA assumes in the primary analysis that release rates remain constant.
However, to address the uncertainty associated with the number of confirmed releases, EPA also assesses avoided costs under the final UST regulation using an alternative baseline that projects a continued decline in the release rate consistent with the recent historical trend, and also captures the decline in the number of UST systems as estimated in Chapter 3, Section 3.3.1. This represents a conservative avoided cost scenario because it does not account for the possibility that aging systems or changes in fuel could result in increases in the number of confirmed releases reported, or that the number of UST systems could increase (if, for example, an expanding economy or population growth demands more service locations).
      To estimate the rate of universe decline, EPA mapped historical data on the number of UST systems from 1991 through 2013 to an exponential one-phase decay function, which appears to most accurately represent the observed behavior of the UST system universe over time. EPA also mapped historical data on the release rate to a similar decay function.  These two functions were then used to project future UST universe sizes as well as future release rates. We used the results from these two projections to estimate future number of confirmed releases.
      The cumulative universe of releases over 20 years under this alternative baseline is approximately 69 percent of the number of cumulative releases over 20 years in the primary analysis. The alternative baseline contains proportionally fewer releases than UST systems because two separate declining trends, UST systems and release rate, are used to estimate the future decline in releases. This compounds the projected decline in releases.
	Exhibits 4-5 and 4-6 provide a summary of our findings with respect to avoided releases and avoided groundwater contamination events, respectively, assuming the alternative baseline releases occur. The alternative baseline results in a reduction of roughly 31 percent of both avoided releases and avoided groundwater contamination relative to the original baseline. Correspondingly, in the alternative baseline scenario, approximately 390 to 2,100 releases are avoided under the Selected Option, compared to 480 to 2,600 under Alternative 1 and 120 to 1,500 under Alternative 2. Under the alternative baseline, approximately 140 to 620 groundwater contamination incidents would be avoided under the Selected Option, 210 to 790 under Alternative 1, and 61 to 430 under Alternative 2.
Exhibit 4-5
                  Avoided Releases Under Alternative Baseline
                                    Expert
                                Selected Option
                                 Alternative 1
                                 Alternative 2
Expert 1
                                      760
                                     1,100
                                      410
Expert 2
                                      390
                                      480
                                      120
Expert 3
                                     1,100
                                     1,700
                                      840
Expert 4
                                     2,100
                                     2,600
                                     1,500
Average
(Range)
                                     1,100
                                  (390-2,100)
                                     1,500
                                  (480-2,600)
                                      720
                                  (120-1,500)
Note: See Appendices H and I for inputs and methods for calculating these values. Estimates were validated with experts to ensure they accurately capture their opinions.
Exhibit 4-6
    Avoided Groundwater Contamination Incidents Under Alternative Baseline
                                    Expert
                                Selected Option
                                 Alternative 1
                                 Alternative 2
Expert 1
                                      620
                                      790
                                      430
Expert 2
                                      140
                                      320
                                      61
Expert 3
                                      220
                                      210
                                      190
Expert 4
                                      420
                                      330
                                      390
Average
(Range)
                                      350
                                   (140-620)
                                      410
                                   (210-790)
                                      270
                                   (61-430)
Note: See Appendices H and I for inputs and methods for calculating these values. Estimates were validated with experts to ensure they accurately capture their opinions.

4.5	Benefits from Avoided Releases and Reduced Release Severity
Two sources of avoided costs constitute the majority of quantifiable positive impacts from the final UST regulation. First, some costs related to release remediation do not occur because a number of releases are altogether avoided. Second, some remaining releases are reduced in severity because of the regulatory requirements (e.g., through earlier detection from walkthrough inspections and improved operability of release detection equipment). To capture this dimension of avoided costs, the analysis relies on incremental avoided groundwater remediation costs -- the cost to remediate a groundwater release less the cost to remediate a soil release -- as groundwater releases are generally more costly to remediate than soil releases.
In addition to avoiding remediation costs, release prevention and mitigation results in a variety of other beneficial impacts, including:
*       Avoided vapor intrusion damages;
*       Avoided product loss;
*       Human health benefits;
*       Avoided acute exposure events and large-scale releases; and
*       Ecological benefits (including protection of groundwater quality).
The following sections monetize, quantify, or otherwise describe these impacts.
4.5.1	Avoided Release Remediation
      To determine the benefits of avoided releases, the analysis relies on the draft 23-state Autopsy Report's distribution of releases by source (i.e., the part of the UST system that produces the release), and applies the reduction associated with each regulation to the appropriate source to reduce the number of releases avoided by source.[,] Each avoided release is valued according to the weighted average of remediation costs shown in Exhibit 4-2.
      Exhibit 4-7 presents the total avoided remediation costs under each regulatory option. We estimate that discounted benefits from avoided remediation costs range between approximately $68 million and $380 under the Selected Option, while avoided costs amount to between $82 million and $530 million under Alternative 1 and between $24 million and $290 million under Alternative 2. Consistent with OMB's guidance on discount rates, this chapter presents results using a seven percent annual discount rate; for comparison, Chapter 7 presents results for the Selected Option using a three percent discount rate.
Exhibit 4-7
                 Discounted Avoided Release Remediation Costs
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                     $140
                                     $210
                                      $80
Expert 2
                                      $68
                                      $82
                                      $24
Expert 3
                                     $190
                                     $330
                                     $160
Expert 4
                                     $380
                                     $530
                                     $290
Average
(Range)
                                     $190
                                  ($68-$380)
                                     $290
                                  ($82-$530)
                                     $140
                                  ($24-$290)
Note: Cost estimates reflect a seven percent discount rate.

4.5.2	Reduction in Release Severity
      EPA expects that the regulatory requirements will reduce the volume and duration of releases. As a result of the smaller quantity released and the shorter duration of the release, releases are assumed to be less likely to reach groundwater, thus reducing release severity. To assess the impact on remediation costs associated with reduced release severity, the analysis focuses on changes in the number of releases that would have involved groundwater in the baseline, but because of the final UST regulation, involve only soil. While this metric does not capture all of the release mitigation effects of the regulatory requirements, avoided groundwater contamination is likely to be among the most significant effects of the regulation. The difference in remediation costs between soil and groundwater releases is substantial: remediation cost for an average groundwater release is approximately $290,000, while an average soil release costs approximately $74,000 to remediate. Remediation costs across release extent and medium contaminated range from $27,000 to $460,000 based on typical site remediation costs from New Hampshire and Utah.
      To estimate the number of releases that are reduced in severity, we use experts' estimates of reductions in groundwater involvement and distribute them across release source, medium contaminated, and release extent. We distribute remaining releases according to the draft 23-state Autopsy Report results and calculate additional benefits from remediation due to reductions in groundwater contamination following the regulation. We calculate avoided costs from reduced release severity by subtracting the cost to remediate all remaining releases after the final UST regulation is in effect from the cost to remediate all remaining releases in the baseline. In both cases, we remove from consideration the same number of fully-avoided releases and consider only the avoided costs from shifting releases from groundwater to soil.
      A key limitation of this approach may lead to a conservative estimate of the effects of the final UST regulation. The analysis assumes that the distribution of releases across size (i.e., extent) does not change as a consequence of changes in groundwater contamination. In reality, changes in the likelihood of groundwater contamination are probably (at least in part) a consequence of reductions in release volume and duration. The same reductions in release volume that lower the incidence of groundwater contamination would likely also reduce the number of large extent releases of all types and decrease the average size of smaller releases. That is, new requirements should both reduce the number of groundwater contamination events and large extent events of all types. Our model captures only changes in the number of times that groundwater would be contaminated, and does not consider cost savings associated with smaller soil-only sites or small groundwater contamination incidents. We therefore likely understate avoided remediation costs.
      Exhibit 4-8 displays EPA's findings regarding discounted avoided costs due to the mitigation of groundwater incidents. The analysis calculates avoided remediation costs by taking the difference between estimated remediation costs before and after the regulatory changes are implemented. This difference accounts for both the reduction in groundwater release incidents as well as the increase in soil contamination events. EPA estimates that benefits from averted groundwater releases range from approximately $46 million to $190 million under the Selected Option, $80 million to $290 million under Alternative 1, and $20 million and $130 million under Alternative 2. Avoided costs from reduced groundwater contamination are additive to avoided costs from avoided releases.
Exhibit 4-8
               Discounted Avoided Groundwater Remediation Costs
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                     $190
                                     $290
                                     $130
Expert 2
                                      $46
                                     $120
                                      $20
Expert 3
                                      $71
                                      $80
                                      $61
Expert 4
                                     $130
                                     $120
                                     $120
Average
(Range)
                                     $110
                                  ($46-$190)
                                     $150
                                  ($80-$290)
                                      $84
                                  ($20-$130)
Note: Cost estimates reflect a seven percent discount rate.

4.5.3	Total Avoided Remediation Costs from Avoided Releases and Reduced Release Severity
Exhibit 4-9 displays the sum of avoided remediation costs across both avoided releases and mitigated groundwater incidents for all four experts. Because experts with the lowest estimate in one of these categories did not necessarily have similarly low estimates in the other, the range of total avoided costs is not equal to the sum of the ranges from Exhibits 4-7 and 4-8.
Exhibit 4-9
                 Total Discounted Avoided Remediation Costs[a]
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                     $330
                                     $490
                                     $210
Expert 2[b]
                                     $110
                                     $200
                                      $44
Expert 3
                                     $260
                                     $410
                                     $220
Expert 4
                                     $510
                                     $650
                                     $410
Average
(Range)
                                     $300
                                  ($110-$510)
                                     $440
                                  ($200-$650)
                                     $220
                                  ($44-$410)
[a] Cost estimates were derived using a seven percent discount rate.
b Expert 2 provided responses that generate benefits that are relatively low compared to the other experts. Conversations with this expert indicated that he assumed partial noncompliance of at least 25 percent (that is, a compliance rate of at most 75 percent). To evaluate the potential magnitude of this inconsistency, we examined the impact of scaling Expert 2's avoided remediation costs from 75 percent compliance to 100 percent compliance. This adjustment resulted in avoided remediation costs of greater than $150 million annually under the Selected Option, assuming a seven percent discount rate. See Appendix H for additional discussion.

Although the values generated by the experts' responses cover a wide range, we note that the avoided cost estimates tend to spread evenly around the mean. Expert 4 consistently represents the high-end estimate of avoided costs, and Expert 2 consistently represents the low-end. While we are not able to explain why Expert 4's estimates are consistently higher than those of the other experts, we do note one source of uncertainty that applies to Expert 4's estimates. The experience of most experts is related to implementing state regulatory programs, which directly consider the universe of confirmed releases evaluated in this analysis. However, the experience of Expert 4 considers system engineering and changes in UST-related equipment. As a result, Expert 4's estimates consider all potential releases and then align these to EPA's universe of confirmed releases. While this approach is methodologically sound, it requires one more assumption on the part of the expert to derive a total estimate.
In contrast, Expert 2's responses generate benefits estimates that are low compared to the responses of other experts. Comments provided by the expert indicated, and subsequent conversations with him verified, that he assumed a significant level of noncompliance with the regulations in deriving his estimates. His estimates assume that at least 25 percent of facilities will not correctly implement the requirements (that is, a compliance rate of at most 75 percent). The expert noted that this assumed level of compliance did not include intentional noncompliance, but did attempt to account for a lack of awareness or human error by owners/operators. This assumption is methodologically sound, but is not consistent with the full compliance assumed in our cost analysis. As a result, the values provided by Expert 2 may significantly understate benefits relative to costs. To evaluate the potential magnitude of this inconsistency, we scale Expert 2's avoided remediation costs from 75 percent compliance to 100 percent compliance as a sensitivity analysis. This adjustment results in total avoided remediation costs greater than $150 million annually under the Selected Option, assuming a seven percent discount rate. Appendix H provides additional discussion of the effect of assumed noncompliance on the experts' responses and potential net benefits of the final UST regulation.
4.5.4	Benefits from Avoided Releases and Reduced Release Severity under the Alternative Baseline Scenario
	Exhibits 4-10 and 4-11 present avoided remediation costs associated with the avoided releases and avoided groundwater incidents shown in Exhibits 4-5 and 4-6 under the alternative baseline scenario. In the alternative baseline scenario, avoided release remediation costs range from $47 million to $260 million under the Selected Option, between $56 million and $370 million under Alternative 1, and between $17 million and $200 million under Alternative 2. Averted groundwater remediation costs, meanwhile, range from $32 million to $130 million under the Selected Option, $55 million to $200 million under Alternative 1, and $14 million to $92 million under Alternative 2. These alternative estimates represent conservative estimates of the potential value of avoided releases, because they do not consider possible factors that may lead to increases in the number of releases reported or the number of UST systems in the future.

Exhibit 4-10
    Discounted Avoided Release Remediation Costs Under Alternative Baseline
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                      $94
                                     $140
                                      $56
Expert 2
                                      $47
                                      $56
                                      $17
Expert 3
                                     $130
                                     $230
                                     $110
Expert 4
                                     $260
                                     $370
                                     $200
Average
(Range)
                                     $130
                                  ($47-$260)
                                     $200
                                  ($56-$370)
                                      $95
                                  ($17-$200)
Note: Cost estimates reflect a seven percent discount rate.

Exhibit 4-11
  Discounted Avoided Groundwater Remediation Costs Under Alternative Baseline
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                     $130
                                     $200
                                      $92
Expert 2
                                      $32
                                      $84
                                      $14
Expert 3
                                      $49
                                      $55
                                      $42
Expert 4
                                      $89
                                      $83
                                      $85
Average
(Range)
                                      $75
                                  ($32-$130)
                                     $100
                                  ($55-$200)
                                      $58
                                   ($14-$92)
Note: Cost estimates reflect a seven percent discount rate.

Exhibit 4-12 displays the sum of avoided remediation costs across both avoided releases and mitigated groundwater incidents under the alternative baseline scenario. Because experts with relatively lower estimates in one of these categories did not necessarily have similarly low estimates in the other, the range of avoided costs presented is not the sum of lower and higher bounds in Exhibits 4-10 and 4-11. As the cumulative release universe in the alternative baseline scenario is roughly 69 percent of cumulative releases in the original baseline, total avoided costs in the alternative baseline are approximately 31 percent lower than they are in the primary analysis.
Exhibit 4-12
     Total Discounted Avoided Remediation Costs Under Alternative Baseline
                                    Expert
                         Selected Option
($ millions)
                          Alternative 1
($ millions)
                          Alternative 2
($ millions)
Expert 1
                                     $230
                                     $340
                                     $150
Expert 2
                                      $79
                                     $140
                                      $31
Expert 3
                                     $180
                                     $290
                                     $150
Expert 4
                                     $350
                                     $450
                                     $280
Average
(Range)
                                     $210
                                  ($79-$350)
                                     $300
                                  ($140-$450)
                                     $150
                                  ($31-$280)
Note: Cost estimates reflect a seven percent discount rate.

4.5.5	Avoided Costs by Requirement
Exhibit 4-13 presents overall avoided remediation costs by requirement for the Selected Option. The exhibit shows the avoided costs for each requirement based on experts' responses to the effects of the individual requirements in the final UST regulation. Beneficial impacts are concentrated similarly to costs: the majority of avoided costs are captured by walkthrough inspections, overfill prevention equipment tests, spill bucket tightness tests, containment sump tests, and operability tests. Estimates in Exhibit 4-13 assume that cost savings associated with each regulatory requirement occur one year after implementation and reflect discounting. Similar exhibits presenting overall avoided remediation costs by requirement for Alternative 1 and Alternative 2 are included in Appendix I.
The model used by EPA to estimate avoided remediation costs is not designed to measure avoided costs from large-scale releases such as those typically associated with UST systems with FCTs and AHFDSs. Releases from these types of systems constitute a small portion of total releases, but may be large in volume and can result in significant groundwater impacts. Our analysis does not estimate the benefits associated with changes in operation of these systems. However, we include a qualitative discussion of these acute events later in this chapter.
Exhibit 4-13
Total Discounted Avoided Costs By Requirement For Conventional UST Systems[a,b] ($ millions)
Selected Option
                                 Descriptionc
                                   Expert 1
                                   Expert 2
                                   Expert 3
                                   Expert 4
                                    Average
Release Prevention
Walkthrough inspections
                                                                          $140
                                                                           $44
                                                                          $130
                                                                          $270
                                                                          $150
Overfill prevention equipment inspection
                                                                           $23
                                                                          $1.1
                                                                           $19
                                                                           $25
                                                                           $17
Spill prevention equipment testing
                                                                           $16
                                                                          $7.3
                                                                           $36
                                                                           $21
                                                                           $20
Containment sump testing
                                                                          $9.3
                                                                           $18
                                                                          $1.0
                                                                          $9.7
                                                                          $9.4
Testing after repairs to spill and overfill prevention equipment, and secondary containment
                                                                          $2.7
                                                                           $11
                                                                          $1.9
                                                                          $7.9
                                                                          $5.9
Eliminate flow restrictors in vent lines for all new tanks and when overfill prevention equipment is replaced
                                                                          $2.2
                                                                          $7.5
                                                                         $0.85
                                                                          $1.5
                                                                          $3.0
Subtotal - Release Prevention
                                                                          $190
                                                                           $89
                                                                          $190
                                                                          $330
                                                                          $200
Release Detection
Operability tests for release detection methods
                                                                          $130
                                                                           $13
                                                                           $61
                                                                          $170
                                                                           $92
Groundwater monitoring site assessment[d]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Vapor monitoring site assessment[d]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Add SIR and CITLDS usage[e]
                                                                         $0.21
                                                                         $0.00
                                                                         $0.94
                                                                         $0.56
                                                                         $0.43
Response to interstitial monitoring alarms
                                                                         $0.80
                                                                           $10
                                                                         $0.21
                                                                         $0.78
                                                                          $2.9
Remove release detection deferral for EGTs
                                                                         $0.68
                                                                          $2.2
                                                                          $7.6
                                                                          $5.9
                                                                          $4.1
Subtotal - Release Detection
                                                                          $130
                                                                           $25
                                                                           $70
                                                                          $170
                                                                           $99
Other
Notification of ownership changes[f]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Replacement of lined tanks that cannot be repaired according to a code of practice[g]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.01
                                                                         $0.00
                                                                         $0.00
Requirements for demonstrating compatibility with fuels >E10 and >B20[h]
                                                                         $0.00
                                                                         $0.11
                                                                         $0.00
                                                                         $0.12
                                                                         $0.06
Subtotal  -  Other
                                                                         $0.00
                                                                         $0.11
                                                                         $0.01
                                                                         $0.12
                                                                         $0.06
EPAct-related Provisions
Operator Training
                                                                          $1.0
                                                                         $0.04
                                                                         $0.60
                                                                          $1.5
                                                                         $0.80
Secondary containment
                                                                          $1.0
                                                                         $0.66
                                                                          $7.6
                                                                          $2.4
                                                                          $2.9
Subtotal - EPAct-related Provisions
                                                                          $2.1
                                                                         $0.69
                                                                          $8.2
                                                                          $3.9
                                                                          $3.7
                                                                          TOTAL
                                                                          $330
                                                                          $110
                                                                          $260
                                                                          $510
                                                                          $300
[a] Cost estimates were derived using a seven percent discount rate.
[b] Reductions in frequency and release severity (as measured by changes in groundwater contamination) do not adequately capture the positive impacts of preventing releases from very large systems such as AHFDSs and UST systems with FCTs. Releases from these types of systems constitute a small portion of total releases, but may be large in volume and can result in significant groundwater impacts. Especially in the case of AHFDSs, even minor problems can create large releases due to the significant pressure under which contents are stored. The model used by EPA to estimate avoided remediation costs is not designed to measure avoided costs from very large releases such as those typically associated with AHFDSs and FCTs, and we therefore do not offer an estimate of avoided costs for requirements that apply to these systems.
[c] Some requirements, particularly those that target narrow subpopulations of the UST system universe, may generate higher avoided costs than this analysis suggests. Three sources of uncertainty drive these smaller universe results: First, EPA's model is calibrated to estimate avoided costs for broad-based national changes at average facilities; extrapolation of these results to small populations may not reflect specific subpopulations (e.g., UST systems in Indian country). Second, several experts stated that their estimates of impacts for requirements affecting narrow subsets of UST populations are more uncertain than broader estimates. Finally, experts emphasized that equipment replacement, inspection, training, and testing are all essential to ensure release reductions, and they used judgment to emphasize the different roles of these different activities. Therefore, the assignment of specific impacts to each of the requirements is potentially less accurate than the aggregate estimates of avoided impacts.
[d] Experts 1, 2, and 3 attributed reductions to the groundwater and vapor monitoring site assessment requirements; however, these experts also noted that they assumed the requirements would lead users to switch to another leak detection method. Because EPA does not assume that users will necessarily switch methods, we conservatively removed the experts' assumed reductions for this requirement. Expert 4 did not attribute reductions to these requirements.
[e] Expert 2 assumed negligible effect of the requirement to add SIR and CITLDS usage on release frequency and severity.
[f] All experts assumed no effect, or in the case of Expert 3, a negligible effect, of the requirement for notification of ownership changes on reductions in release frequency or severity.
[g] Although all experts attributed some reduction in release frequency or severity to this requirement, the number of tanks that cannot be repaired according to a code of practice is assumed to be so small that estimated benefits are negligible.
[h] Experts 1 and 3 attributed reductions to the compatibility requirement but noted that the majority of the benefit should be attributed to E10 users, which are not included in this requirement. As a result, we conservatively removed these experts' assumed reductions for this requirement.

As noted in Exhibit 4-1, EPA excluded the highest state-level remediation cost values from its calculation of average cost of release remediation. While this step contributes toward a conservative (low) estimate of avoided costs, the possibility remains that the average remediation costs used in Exhibit 4-13 overestimate the positive impacts of the final UST regulation if state data provided are not representative of national average remediation costs. In Exhibit 4-14, we therefore estimate the positive effects of the final UST regulation using only the lowest remediation costs available. As shown in Exhibit 4-14, EPA's estimate of the avoided remediation costs of the final UST regulation using the lowest state cost estimates is $73 million to $330 million per year under the Selected Option. While this is not a true "lower bound" estimate, these estimates reflect costs that lead to lower than average costs when compared to figures reported by ASTSWMO. Similar exhibits presenting overall avoided remediation costs by requirement for Alternative 1 and Alternative 2 are included in Appendix I.
Exhibit 4-14
     Sensitivity Analysis: Total Discounted Avoided Costs By Requirement
  Based On New Hampshire Remediation Costs[a,b] ($ millions)
Selected Option
                                 Descriptionc
                                   Expert 1
                                   Expert 2
                                   Expert 3
                                   Expert 4
                                    Average
Release Prevention
Walkthrough inspections
                                                                           $86
                                                                           $27
                                                                           $81
                                                                          $170
                                                                           $92
Overfill prevention equipment inspection
                                                                           $15
                                                                         $0.74
                                                                           $13
                                                                           $16
                                                                           $11
Spill prevention equipment testing
                                                                           $11
                                                                          $5.0
                                                                           $24
                                                                           $14
                                                                           $14
Containment sump testing
                                                                          $6.1
                                                                           $13
                                                                         $0.68
                                                                          $6.5
                                                                          $6.5
Testing after repairs to spill and overfill prevention equipment, and secondary containment
                                                                          $1.7
                                                                          $6.9
                                                                          $1.2
                                                                          $5.1
                                                                          $3.7
Eliminate flow restrictors in vent lines for all new tanks and when overfill prevention equipment is replaced
                                                                          $1.3
                                                                          $5.1
                                                                         $0.57
                                                                         $0.97
                                                                          $2.0
Subtotal - Release Prevention
                                                                          $120
                                                                           $58
                                                                          $120
                                                                          $220
                                                                          $130
Release Detection
Operability tests for release detection methods
                                                                           $77
                                                                          $7.3
                                                                           $38
                                                                          $100
                                                                           $56
Groundwater monitoring site assessment[d]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Vapor monitoring site assessment[d]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Add SIR and CITLDS usage[e]
                                                                         $0.13
                                                                         $0.00
                                                                         $0.58
                                                                         $0.36
                                                                         $0.27
Response to interstitial monitoring alarms
                                                                         $0.49
                                                                          $6.2
                                                                         $0.13
                                                                         $0.50
                                                                          $1.8
Remove release detection deferral for EGTs
                                                                         $0.42
                                                                          $1.2
                                                                          $4.7
                                                                          $3.6
                                                                          $2.5
Subtotal - Release Detection
                                                                           $78
                                                                           $15
                                                                           $43
                                                                          $110
                                                                           $61
Other
Notification of ownership changes[f]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Replacement of lined tanks that cannot be repaired according to a code of practice[g]
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
                                                                         $0.00
Requirements for demonstrating compatibility with fuels >E10 and >B20[h]
                                                                         $0.00
                                                                         $0.07
                                                                         $0.00
                                                                         $0.08
                                                                         $0.04
Subtotal  -  Other
                                                                         $0.00
                                                                         $0.07
                                                                         $0.00
                                                                         $0.08
                                                                         $0.04
EPAct-related Provisions
Operator Training
                                                                         $0.66
                                                                         $0.02
                                                                         $0.38
                                                                          $1.0
                                                                         $0.52
Secondary containment
                                                                         $0.67
                                                                         $0.44
                                                                          $4.8
                                                                          $1.5
                                                                          $1.9
Subtotal - EPAct-related Provisions
                                                                          $1.3
                                                                         $0.46
                                                                          $5.2
                                                                          $2.5
                                                                          $2.4
                                                                          TOTAL
                                                                          $200
                                                                           $73
                                                                          $170
                                                                          $330
                                                                          $190
[a] Cost estimates were derived using a seven percent discount rate.
[b] Reductions in frequency and release severity (as measured by changes in groundwater contamination) do not adequately capture the positive impacts of preventing releases from very large systems such as AHFDSs and UST systems with FCTs. Releases from these types of systems constitute a small portion of total releases, but may be large in volume and can result in significant groundwater impacts. Especially in the case of AHFDSs, even minor problems can create large releases due to the significant pressure under which contents are stored. The model used by EPA to estimate avoided remediation costs is not designed to measure avoided costs from very large releases such as those typically associated with AHFDSs and FCTs, and we therefore do not offer an estimate of avoided costs for requirements that apply to these systems.
[c] Some requirements, particularly those that target narrow subpopulations of the UST system universe, may generate higher avoided costs than this analysis suggests. Three sources of uncertainty drive these smaller universe results: First, EPA's model is calibrated to estimate avoided costs for broad-based national changes at average facilities; extrapolation of these results to small populations may not reflect specific subpopulations (e.g., UST systems in Indian country). Second, several experts stated that their estimates of impacts for requirements affecting narrow subsets of UST populations are more uncertain than broader estimates. Finally, experts emphasized that equipment replacement, inspection, training, and testing are all essential to ensure release reductions, and they used judgment to emphasize the different roles of these different activities. Therefore, the assignment of specific impacts to each of the requirements is potentially less accurate than the aggregate estimates of avoided impacts.
[d] Experts 1, 2, and 3 attributed reductions to the groundwater and vapor monitoring site assessment requirements; however, these experts also noted that they assumed the requirements would lead users to switch to another leak detection method. Because EPA does not assume that users will necessarily switch methods, we conservatively removed the experts' assumed reductions for this requirement. Expert 4 did not attribute reductions to these requirements.
[e] Expert 2 assumed negligible effect of the requirement to add SIR and CITLDS usage on release frequency and severity.
[f] All experts assumed no effect, or in the case of Expert 3, a negligible effect, of the requirement for notification of ownership changes on reductions in release frequency or severity.
[g] Although all experts attributed some reduction in release frequency or severity to this requirement, the number of tanks that cannot be repaired according to a code of practice is assumed to be so small that estimated benefits are negligible.
[h] Experts 1 and 3 attributed reductions to the compatibility requirement but noted that the majority of the benefit should be attributed to E10 users, which are not included in this requirement. As a result, we conservatively removed these experts' assumed reductions for this requirement.

4.6	Avoided Vapor Intrusion Damages
      Vapor intrusion generally occurs when petroleum or highly-dissolved concentrations of free product come into direct contact with building sumps and foundations, elevator shafts, and preferential pathways (e.g. improperly sealed utility lines). Intrusion can also occur when these substances come close to building foundations. The cost to remediate vapor intrusion is typically incremental to the cost to remediate a LUST site. Based on information provided by four states, EPA estimates that, on average, 5.5 percent of all releases cause vapor intrusion issues. Each of these instances requires additional remedial actions valued at approximately $42,000 beyond ordinary release remediation costs. As reported in Exhibit 4-15, given 770 to 3,600 avoided releases and mitigated groundwater incidents, we estimate between 42 and 200 avoided vapor intrusion incidents under the Selected Option. This reduction would avoid between $1.7 million and $7.9 million per year in avoided remediation costs related to vapor intrusion. Under Alternative 1, this range increases to $2.5 million to $9.1 million, and under Alternative 2, this range decreases to $0.6 million to $6.0 million per year.
Exhibit 4-15

                  Avoided Vapor Intrusion Costs ($ millions)

Expert 1
Expert 2
Expert 3
Expert 4
                                    Average
                                    (Range)
                                Selected Option
Total avoided releases and avoided groundwater incidents
                                                                          2,000
                                                                            770
                                                                          1,900
                                                                          3,600
                                                                          2,100
                                                                    (770-3,600)
Avoided vapor intrusion incidents
                                                                            110
                                                                             42
                                                                            100
                                                                            200
                                                                            110
                                                                       (42-200)
Avoided vapor intrusion costs
                                                                           $4.3
                                                                           $1.7
                                                                           $4.1
                                                                           $7.9
                                                                           $4.5
                                                                    ($1.7-$7.9)
                                 Alternative 1
Total avoided releases and avoided groundwater incidents
                                                                          2,700
                                                                          1,100
                                                                          2,700
                                                                          4,200
                                                                          2,700
                                                                  (1,100-4,200)
Avoided vapor intrusion incidents
                                                                            150
                                                                             63
                                                                            150
                                                                            230
                                                                            150
                                                                       (63-230)
Avoided vapor intrusion costs
                                                                           $5.9
                                                                           $2.5
                                                                           $5.9
                                                                           $9.1
                                                                           $5.9
                                                                    ($2.5-$9.1)
                                 Alternative 2
Total avoided releases and avoided groundwater incidents
                                                                          1,200
                                                                            260
                                                                          1,500
                                                                          2,800
                                                                          1,400
                                                                    (260-2,800)
Avoided vapor intrusion incidents
                                                                             66
                                                                             14
                                                                             82
                                                                            150
                                                                             78
                                                                       (14-150)
Avoided vapor intrusion costs
                                                                           $2.6
                                                                           $0.6
                                                                           $3.2
                                                                           $6.0
                                                                           $3.1
                                                                    ($0.6-$6.0)

	Under the alternative baseline, avoided vapor intrusion costs fall due to the smaller universe of releases. In the Selected Option, avoided costs are $1.2 million to $5.5 million. Under Alternative 1, avoided costs range from $1.7 million to $6.3 million; under Alternative 2, they range between $0.4 million and $4.1 million.
4.7	Avoided Product Loss
      Releases into the environment cause operators to lose otherwise marketable fuel products. Exhibit 4-16 presents costs avoided due to product loss. The analysis calculates the product loss associated with avoided releases by multiplying the average volume associated with each release source by the number of releases of that type before and after the final UST regulation is in effect. Based on the estimates of avoided releases presented by the experts, the draft 23-state Autopsy Report's distribution of releases, and average release volumes reported in the Florida study, EPA estimates that approximately 0.25 million gallons to 1.9 million gallons per year of diesel and gasoline releases are avoided as a consequence of the Selected Option. At an average price of $3.73 per gallon, owners and operators avoid losing approximately $0.9 million to $6.5 million in product due to releases. These values range from 0.22 million gallons to 2.2 million gallons, or $0.8 million to $7.6 million, under Alternative 1. Under Alternative 2, these values decrease to a range of 0.10 million gallons to 1.5 million gallons, or $0.4 million to $5.2 million. Limited data on release size do not support an analysis of avoided product loss associated with releases that are reduced in severity. This estimate of avoided product loss there understates total likely avoided product losses.
Exhibit 4-16

Value Of Avoided Product Loss
                                    Expert
                                Selected Option
                                 Alternative 1
                                 Alternative 2

                               Thousand gallons
                                  $ millions
                               Thousand gallons
                                  $ millions
                               Thousand gallons
                                  $ millions
Expert 1
                                                                            650
                                                                           $2.3
                                                                            750
                                                                           $2.6
                                                                            440
                                                                           $1.5
Expert 2
                                                                            250
                                                                           $0.9
                                                                            220
                                                                           $0.8
                                                                            100
                                                                           $0.4
Expert 3
                                                                            830
                                                                           $2.9
                                                                          1,200
                                                                           $4.1
                                                                            710
                                                                           $2.5
Expert 4
                                                                          1,900
                                                                           $6.5
                                                                          2,200
                                                                           $7.6
                                                                          1,500
                                                                           $5.2
Average
(Range)
                                                                            900
                                                                    (250-1,900)
                                                                           $3.1
                                                                    ($0.9-$6.5)
                                                                          1,100
                                                                    (220-2,200)
                                                                           $3.8
                                                                    ($0.8-$7.6)
                                                                            690
                                                                    (100-1,500)
                                                                           $2.4
                                                                    ($0.4-$5.2)
Releases are valued using an average price of motor fuel in 2012. Prices per gallon for all grades of retail motor gasoline and No. 2 diesel fuel (all concentrations of sulfur) were $3.63 and $3.97, respectively, as reported by: U.S. Bureau of Transportation Statistics. "Sales Price of Transportation Fuel to End-Users." National Transportation Statistics 2013. Table 3-11. Accessed at: http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/NTS_Entire_0.pdf. We weight these prices according to prime supplier sales volumes in 2012 published by the Energy Information Administration, which summed to 347,234.5 thousands of gallons per day for gasoline and 143,270.6 thousands of gallons per day for all grades of diesel fuel (U.S. Energy Information Administration. Petroleum & Other Liquids. Prime Supplier Sales Volumes. Accessed at: http://www.eia.gov/dnav/pet/pet_cons_prim_dcu_nus_a.htm.).

Under the alternative baseline, avoided costs due to product loss are lower than in the original baseline as there are relatively fewer releases. Under the Selected Option, avoided costs due to product loss are $0.6 million to $4.5 million. Under Alternative 1, avoided costs range from $0.5 million to $5.2 million; under Alternative 2, they range from $0.3 million to $3.6 million.
4.8	Human Health Benefits
      Exposure to petroleum through ingestion, dermal contact, and inhalation can cause a range of health effects, including cancer and non-cancer impacts associated with benzene, and non-cancer impacts (e.g., neurological impacts) associated with other petroleum constituents such as toluene. In addition, exposure to jet fuel, such as that stored in AHFDSs and FCTs at commercial and military airports, can result in non-cancer impacts to skin, nervous, and respiratory systems. The types of health risks that may be avoided by the final UST regulation are described in more detail below.
      The complex nature of petroleum mixtures and the limited toxicological data available both for petroleum mixtures and for individual component compounds of petroleum limits EPA's ability to comprehensively document the health effects associated with the most significant releases. However, the toxicological testing that has been conducted on some common components of total petroleum hydrocarbons (TPH) suggests that exposures to TPH through inhalation or ingestion of gasoline or diesel could result in the following effects:
    *       Neurological effects, such as central nervous system depression, have been associated with acute and chronic exposures to toluene and xylenes; n-hexane exposure has been associated with effects on peripheral neuropathy;
    *       Hematological effects associated with oral and inhalation exposure to benzene and with oral and inhalation exposure to naphthalene;
    *       Renal and hepatic effects associated with BTEX compounds and other aromatic hydrocarbon compounds;
    *       Developmental effects associated with intermediate exposures to ethylbenzene and xylenes; and
    *       Carcinogenic effects of oral exposures to certain polycyclic aromatic hydrocarbons (PAHs) including benzo(a)pyrene, benz(a)anthracene, and dibenz(a,h)anthracene.
	Health risks may also be associated with exposure to kerosene, which may be stored in USTs or used as a component in jet fuel. Although risks associated with kerosene have not been studied as widely as those associated with petroleum, existing data suggest that these risks primarily include non-cancer impacts to the skin, nervous, and respiratory systems. In the baseline, some of these risks may be reduced due to existing monitoring standards under the Occupational Safety and Health Administration (OSHA). However, because the final UST regulation includes new requirements for AHFDSs and UST systems with FCTs located at commercial and military airports, avoidance of health risks from kerosene could represent an additional benefit of the final UST regulation.
	The magnitude of health benefits associated with avoiding exposure to petroleum and jet fuel components depends on multiple factors. These factors include the number of cancer cases and non-cancer impacts per average UST release, which in turn depends on the number of groundwater users surrounding UST sites; the number of releases prevented through implementation of the final UST regulation; and the willingness-to-pay to avoid a fatal cancer (e.g., the value of a statistical life) or willingness-to-pay to avoid non-cancer impacts. In addition, assumptions about baseline behaviors, such as the assumption that individuals will limit their own exposure in certain cases (e.g., when petroleum contamination exceeds a "taste/odor threshold" and water is no longer palatable), affect the estimated magnitude of health benefits. Based on available information on average plume volumes and ages and the distribution of groundwater users, these benefits are expected to be small. Nevertheless, some larger releases may have significant cancer and non-cancer risks associated with them. Although these health effects are not able to be reliably quantified with available data, they represent additional potential benefits of the regulation.
4.9	Avoided Acute Exposure Events and Large-Scale Releases
      Most health effects associated with leaking underground storage tanks reflect long-term exposures, but some releases from UST systems relate to acute events such as fire or explosion. These releases can involve acute exposures, large volumes of free product, extensive ecological damage, and injuries and death, depending on the circumstances of the event. Because these events are both infrequent and difficult to predict, it is not possible to quantify or monetize the impact associated with avoiding them, but the response, remediation, and medical costs associated with a single acute incident could be significant. The final UST regulation is designed to ensure effective maintenance of UST systems, and one benefit will be to reduce the chances of an acute event that could result in a large-scale release and its associated damages (e.g., a well-maintained UST system is less likely to be in a condition where it may explode).
      Acute events are especially important in the case of UST systems such as AHFDSs and UST systems with FCTs, which can hold large volumes of fuel. Releases from these systems can result in extensive groundwater and other environmental and health impacts. For instance, an estimated 300,000 to 500,000 gallons of fuel was released from a 2.1 million gallon underground field-constructed tank at a fuel depot in Portsmouth, VA that was in operation from the 1950s to mid-1980s. Free product was found within 20 feet of a nearby creek in 1987. As of 2011, approximately 143,000 gallons of product had been recovered.
      In addition, the final UST regulation may large-scale releases associated with AHFDSs and FCTs. An example of the potential magnitude of the releases from these systems is the pattern of releases at Pease Air Force Base, where jet fuel was delivered to the runway apron via an underground fueling system. Historical leakage from the system contaminated soil and groundwater, forming groundwater plumes at many sites along the system. A site release study identified 60 to 70 release points with varying degrees of severity along the refueling system line with free product found under the apron at closure. While there are no historical records available indicating the amount of leaked fuel or leak origins, the presence of residual soil and groundwater contamination poses a significant threat to human health and the environment.
      While the analytical procedure used by EPA to estimate monetized benefits was unable to capture the positive impacts of preventing releases from these types of systems, we note that preventing or mitigating these releases may generate substantial reductions in remediation costs and public exposure.
4.10	Ecological Benefits
	A document prepared for EPA outlines the types of ecological damages that can result from land-based pollution releases:

      Measurable damage to ecological resources from land releases generally occurs when groundwater or overland flow of water carry contaminants to a nearby surface water body. Flood events and other acute incidents can cause releases of waste that have an immediate and significant effect on ecological resources (e.g., a surface impoundment dike fails and releases contaminants into a river, killing fish and other biota). More common are gradual increases in contaminant levels due to long-term releases to groundwater. These may have a broad array of impacts on both resources used by humans (such as fish populations) and on "non-use value" such as the value of preserving habitat and species diversity. In addition, biota can be affected by uptake of contaminants from soil, particularly in wetlands or areas where the water table is high.

Because releases from USTs typically reach soil before reaching groundwater, such releases would likely be classified as land releases. Any releases avoided due to the final UST regulation may result in ecological benefits. A complete assessment of ecological benefits, however, requires significant location-specific data, and it is often difficult to identify sufficient data to support valuation of both use and non-use values of preserving habitat and species diversity.

      The ecological benefits that accrue from the final UST regulation are likely to occur as a consequence of averted groundwater contamination. The resource economics literature contains numerous examples of studies that value these services, as demonstrated by the public's willing-to-pay (WTP) for groundwater protection programs (e.g., see Poe et al. 2001). However, these values are largely context-specific in terms of location, scale, and the specific threat to groundwater considered and do not provide broadly-applicable information on the value of groundwater.
      Some attempts have been made to develop standardized values for groundwater, often for purposes of Natural Resource Damage Assessment (NRDA). For instance, the State of New Jersey currently employs a replacement cost approach to determine interim economic losses associated with injuries to groundwater. Even so, replacement cost methods do not constitute a proper WTP valuation. The replacement costs of natural resources and their services capture WTP only when they meet three criteria: 1) replacement provides equivalent quality and quantity of services; 2) the public is actually willing to pay for the replacement; and 3) replacement is the most cost-effective means of restoring the lost services. Even if these conditions are true, this approach may overestimate groundwater values in urban areas, as land is typically more expensive, and underestimate groundwater values in areas where land is less expensive.
      Because an assessment of the value of groundwater protected by the final UST regulation is affected by spatial heterogeneity, it requires information about the public's WTP for protection in all states and territories. These data are not available, and EPA is therefore unable to place a value on the groundwater protected. Instead, we provide an estimate below of the total quantity of groundwater that may be protected by the regulation. We note, though, that a portion of the value of restoring groundwater is captured as part of the cost to remediate each release discussed earlier in this chapter. However, while the cost of restoring groundwater to a higher quality after contamination is captured as part of the cost to remediate each release, it cannot be assumed that remediation captures WTP. In many cases, performing remediation to "safe" levels does not fully eliminate contamination, and therefore does not restore the resource to its original value. Therefore, while a significant portion of the value of the quantity of groundwater protected may be captured by the avoided remediation costs, it may not reflect the full WTP of groundwater protection.
      Exhibit 4-17 summarizes a screening assessment of the volume of groundwater contamination potentially avoided because of reductions in releases and groundwater contamination incidents. The analysis relies on the EPA risk assessment, which describes typical volumes of groundwater affected by releases of different sizes over various discovery time frames. EPA's analysis estimates that, under the Selected Option, 19 billion gallons to 88 billion gallons of groundwater per year are protected under conservative assumptions of 10-gallon release volumes that migrate for only one year before discovery. Under the upper bound conditions of 5,000-gallon release volumes and 100-year lifetimes, up to 3.9 trillion gallons of groundwater per year would be potentially protected by the Selected Option. We also calculate the impact of 50-gallon releases over one- and five-year time frames. These releases appear most consistent with empirical data in the draft 23-state Autopsy Report. Assuming that 50-gallon releases and one- to five-year time frames represent the average parameters of avoided releases, we estimate that approximately 50 to 240 billion gallons of groundwater would be protected annually from LUST-related releases due to the regulatory changes.

Exhibit 4-17

          Volume Of Groundwater Protected (billion gallons per year)

Expert 1
Expert 2
Expert 3
Expert 4
                                    Average
                                    (Range)
                                Selected Option
Total avoided releases and avoided groundwater incidents
                                                                          2,000
                                                                            770
                                                                          1,900
                                                                          3,600
                                                                          2,100
                                                                    (770-3,600)
1 year until discovery, 10 gal. release
(24,068,183 gal. GW contaminated)[*]
                                                                             48
                                                                             19
                                                                             45
                                                                             88
                                                                             50
                                                                        (19-88)
1 year until discovery, 50 gal. release
(48,785,436 gal. GW contaminated)[*]
                                                                             97
                                                                             38
                                                                             92
                                                                            180
                                                                            100
                                                                       (38-180)
5 years until discovery, 50 gal. release
(80,192,581 gal. GW contaminated)[*]
                                                                            160
                                                                             62
                                                                            150
                                                                            290
                                                                            170
                                                                       (62-290)
100 year until discovery, 5,000 gal. release
(1,056,971,192 gal. GW contaminated)[*]
                                                                          2,100
                                                                            820
                                                                          2,000
                                                                          3,900
                                                                          2,200
                                                                    (820-3,900)
Primary estimate (average of 50 gal. release over 1 and 5 years)
                                                                            130
                                                                             50
                                                                            120
                                                                            240
                                                                            130
                                                                       (50-240)
                                 Alternative 1
Total avoided releases and avoided groundwater incidents
                                                                          2,700
                                                                          1,100
                                                                          2,700
                                                                          4,200
                                                                          2,700
                                                                  (1,100-4,200)
1 year until discovery, 10 gal. release
(24,068,183 gal. GW contaminated)[*]
                                                                             66
                                                                             28
                                                                             66
                                                                            100
                                                                             65
                                                                       (28-100)
1 year until discovery, 50 gal. release
(48,785,436 gal. GW contaminated)[*]
                                                                            130
                                                                             56
                                                                            130
                                                                            210
                                                                            130
                                                                       (56-210)
5 years until discovery, 50 gal. release
(80,192,581 gal. GW contaminated)[*]
                                                                            220