Addition of a Subsurface Intrusion (SsI) Component to the Hazard Ranking System (HRS)

Regulatory Impact Analysis 
TABLE OF CONTENTS

Executive Summary....................................................................................................................................... ES-1

1. Introduction ................................................................................................................................................. 1

1.1. Background ........................................................................................................................................... 1

1.2. Need for Regulatory Action on HRS Rule ........................................................................................... 2

1.3. Summary of Proposed Rule .................................................................................................................. 3

1.4. Alternative Regulatory Options ............................................................................................................ 6

1.5. Scope of Analysis ................................................................................................................................. 7

1.6. Organization of Document.................................................................................................................. 10

2. Sites Affected by the Proposed Rule ......................................................................................................... 11

3. Impacts of the Proposed Rule .................................................................................................................... 14

3.1. Introduction ......................................................................................................................................... 14

3.2. Cost Estimation Methodology ............................................................................................................ 14

3.3. Cost Estimates .................................................................................................................................... 21

3.4. Summary of Costs ............................................................................................................................... 24

3.5. Benefits ............................................................................................................................................... 24

3.6. Caveats and Limitations...................................................................................................................... 25

4. Distributional Impacts and Considerations ................................................................................................ 26

4.1. Executive Order 12866 – Regulatory Planning and Review, and Executive Order 13563 – Improving 

Regulation and Regulatory Review ............................................................................................................... 26

4.2. Executive Order 12580 – Superfund Implementation ........................................................................ 27

4.3. Executive Order 12898 – Environmental Justice ................................................................................ 28

4.4. Executive Order 13045 – Protection of Children from Environmental Health Risks & Safety Risks 31

4.5. Executive Order 13132 – Federalism ................................................................................................. 32

4.6. Executive Order 13175 – Consultation and Coordination With Indian Tribal Governments ............. 32

4.7. Executive Order 13211 – Actions that Significantly Affect Energy Supply, Distribution, or Usage . 32

4.8. Paperwork Reduction Act ................................................................................................................... 33

4.9. Regulatory Flexibility Act .................................................................................................................. 33

4.10. Unfunded Mandates Reform Act ........................................................................................................ 34

4.11. National Technology Transfer and Advancement Act ....................................................................... 34

5. Summary of Costs, Benefits and Other Impacts ........................................................................................ 35

5.1. Cost Benefit Comparison .................................................................................................................... 35
5.2. Other Required Analyses .................................................................................................................... 36

APPENDIX A: Options Selection Matrix

APPENDIX B: Conceptual Site Model Used to Estimate Costs of Screening for Subsurface Intrusion 

Contamination 

APPENDIX C: Detailed Methodology for Estimating Impacts on Minority and Low-Income Populations 

APPENDIX D: Costs for Vapor Intrusion Site Inspection Tasks Compiled for Regulatory Impact Analysis 
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Executive Summary 

This regulatory impact analysis (RIA) document presents an analysis of the costs, benefits and economic impacts 

of the proposed amendment to the Hazard Ranking System (HRS) regarding identification of releases and 

threatened releases of hazardous substances, pollutants, or contaminants1

. The proposed rulemaking will add a 

subsurface intrusion (SsI) component to the existing soil exposure pathway of the U.S. Environmental Protection 

Agency’s (EPA) HRS. The HRS is the primary method EPA uses to identify the sites posing the greatest threat 

nationally for listing on the Superfund National Priorities List (NPL) under the Comprehensive Environmental 

Response, Compensation, and Liability Act (CERCLA) and the Superfund Amendments and Reauthorization Act 

(SARA). The economic assessment included in this analysis quantifies the expected cost impacts of the proposed 

action, in accordance with the requirements of Executive Order 12866 and Office of Management and Budget 

(OMB) Circular A-4.2 The analysis characterizes the expected benefits of the rule and satisfies other 

administrative requirements established by statute or executive order. 

Overview

CERCLA was passed in Congress in 1980 and amended by SARA in 1986 in response to environmental and 

public health concerns over uncontrolled hazardous waste sites. CERCLA, as amended by SARA, established the 

Superfund program to respond to releases and threatened releases of hazardous substances. CERCLA Section 105 

requires EPA to establish criteria for determining priorities among releases or threatened releases of hazardous 

substances for the purpose of taking remedial action. 

Pursuant to section 105 of CERCLA, EPA established the HRS as a tool to identify and prioritize sites posing the 

most immediate and serious potential threats to human health and the environment. As originally promulgated (47 

FR 31180), the HRS evaluated sites based on three scoring pathways: ground water, surface water and air. The 

HRS was amended in 1990 (55 FR 51532) to include a soil exposure pathway. The HRS site score, which ranges 

from 0 to 100, is obtained by combining the scores of all pathways examined at a given site. A site receiving a 

score of 28.50 or higher is eligible for placement on the National Priorities List (NPL), where it is targeted for 

further investigation and possible site remediation. Since the inception of the HRS in 1982, more than 1,700 sites 

have been placed on the NPL. 

EPA is now considering amending the HRS again to include consideration of subsurface intrusion. Subsurface 

intrusion is an issue at sites with subsurface contamination, where chemical contaminants (especially volatile 

substances) can enter into overlying structures. These contaminants can form vapors, which can pose a threat to 

individuals primarily through inhalation, but also through dermal contact, ingestion and fire or explosion hazards 

when concentrated. Currently, there is no mechanism in the HRS for evaluating threats to human health posed by 

subsurface intrusion. The existing pathways do not evaluate indoor air and site-related contaminants that may 

release vapors.

To implement the addition of an SsI contamination component to the HRS, EPA is considering amending the 

regulations at Title 40 of the Code of Federal Regulations (CFR) 300.425. The agency believes that including the 

evaluation of SsI contamination in the HRS serves the public interest by widening the scope of evaluation of 

 

1 For the purpose of this regulatory impact analysis, the term “hazardous substances, pollutants or contaminants” will be referred to simply as “hazardous 

substances.” 

2 Executive Order 12866, Regulatory Planning and Review, October 4, 1993; Office of Management and Budget, Circular A-4, September 17, 2003.
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human and environmental health issues posed by Superfund sites. Consideration of SsI threats will enable EPA to 

meet the Congressional mandate to assess the relative degree of risk posed to human health and the environment 

by an actual or potential release of hazardous substances into the environment. EPA considers the addition of an 

SsI component to the HRS to be consistent with CERCLA Section 105 and SARA because it will improve the 

agency’s ability to identify sites warranting further evaluation. Consideration of SsI threats also will enable EPA

to address risks posed by subsurface intrusion of contaminants into occupied structures for all populations who 

live and work in areas where releases to the subsurface may create exposures. 

Scope of the Effects of the Proposed Rule

Contaminated sites are evaluated through EPA’s Site Assessment program to determine their potential to be added 

to the NPL. The evaluation of sites involves a series of initial, limited site investigations and data collection 

efforts related to site conditions. This process is implemented by the EPA regional site assessment programs. 

Investigations often include a Preliminary Assessment, Site Inspection (SI), and related investigations. The HRS 

evaluation uses the information obtained from these initial, limited investigations to rank sites according to the 

risk they may pose, relative to other sites, and determine if further investigation is warranted through the 

Remedial or Removal programs.

Each EPA region has a set budget for conducting site assessments. The sites in each EPA region of the country 

are reviewed to determine those that pose the highest risk and are prioritized accordingly. The addition of an SsI 

component to the HRS is not expected to result in additional site assessment funding to account for any increase 

in site assessment costs. Instead, the pipeline of sites will continue to be reviewed under the site assessment 

process. If it is found that SsI-contaminated sites potentially pose a greater risk than other sites, then these sites 

will be prioritized over other sites with contamination not resulting from SsI. 

The proposed rule will affect how EPA and its State Cooperative Agreement partners conduct site assessments 

and HRS scoring. The proposed rule does not impose direct economic or cost impacts on any private entity

because the HRS is a screening tool that does not impose regulatory requirements on any non-governmental 

entity. The CERCLA site assessment program is operated strictly by the public sector using funds that are 

appropriated annually and reside in the Superfund Trust Fund. State and tribal partners may receive financial 

assistance from EPA to evaluate sites through a Cooperative Agreement. EPA and states or tribes collaborate 

closely throughout the Cooperative Agreement process, particularly when identifying sites to be evaluated and 

establishing priorities for performing evaluations. As necessary, sites where subsurface intrusion threats exist may 

then be evaluated using the HRS and, if warranted, proposed for placement on the NPL. Given the current budget 

climate, EPA does not expect that there will be additional funds made available to conduct additional site 

assessments. Because SsI sites have the potential to pose a high level of risk to residents and occupants of other 

buildings in their vicinity, EPA expects that there will be a realignment and reprioritization of its internal 

resources and state Cooperative Agreement funding to address SsI sites. Therefore, EPA will develop a strategy to 

assess SsI sites in a timely manner, while balancing other site assessment needs. For these reasons, EPA believes 

that this proposed rule will not result in the listing of more sites on the NPL during any particular interval. In 

order to better understand the potential size of the reprioritization the analysis estimates the costs nationally that 

EPA and its partners might divert from other resources in order to conduct SsI evaluations. 

The proposed addition may increase the costs to government agencies conducting assessments at SsI sites because 

the scope of a typical SI may need to be expanded or may require more expensive sampling to collect information 

for an SsI evaluation. SsI sampling may require additional sampling and different sample types than those 
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collected at other sites. This may result in an increase in some site assessment costs at some sites with possible SsI 

issues. However, SsI site assessment costs at some other sites may be comparable to, or even less than, sites 

scored under the existing HRS. For example, a site assessment requiring sampling of deep ground water 

monitoring wells under the existing HRS may cost as much as, or more, than sampling conducted at sites with 

possible SsI issues. Additionally, any newly increased costs to government agencies conducting assessments at 

SsI sites are expected to be minimal because federal agencies should already be identifying and addressing SsI as 

part of their environmental programs. 

However, as stated above, no other authority consistently and comprehensively addresses SsI contamination 

across all potential sites, particularly when SsI is the key exposure pathway. While most states have identified SsI 

sites as a high priority, not all states have SsI programs, and states with programs vary in their authority, resources 

and remediation criteria. A redirection of resources available to the states through Cooperative Agreement 

funding is expected to provide for greater national consistency in the identification and evaluation of SsI sites. 

Additionally, EPA issued new vapor intrusion guidance in June 2015, OSWER Technical Guide for Assessing and 

Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. Together with this 

proposed rule, EPA will provide a comprehensive framework to guide evaluation of SsI sites across the country.

Proposed Regulatory Changes 

The proposed addition of an SsI component to the HRS soil exposure pathway would be used by EPA and 

organizations performing work on behalf of EPA (state and tribal partners) to evaluate sites where SsI

contamination may be a concern. Through this proposed rulemaking, EPA would revise the HRS and its process 

for evaluating four pathways. EPA is considering various options for incorporating an SsI screening process into 

the existing HRS without altering the existing HRS structure and methodologies. 

This analysis considers the economic impacts of three regulatory options that vary in how a site with a potential 

SsI threat will be scored using the HRS:

• Option 1 – Score only populations and regularly occupied structures within a zone defined by observed 

exposures above background and resulting from subsurface intrusion attributable to the site being 

evaluated. Under this option, scoring will include both actual contamination for sampled structures and 

inferred contamination for regularly occupied structures within the Area of Observed Exposure (AOE). 

The AOE is bounded by structures with documented contamination resulting from subsurface intrusion 

attributable to the site being evaluated. 

• Option 2 (the preferred option) – Score only populations and regularly occupied structures within zones 

with actual exposure, as well as those above demonstrated subsurface contamination. Under this option, a 

site’s score will include actual contamination for sampled structures and inferred contamination both for 

regularly occupied structures in the AOE and for regularly occupied structures in the Area of Subsurface

Contamination (ASC). The ASC is defined as an area outside of the AOE by sampling locations with 

documented contamination significantly above background and the significant increase can be attributed, 

at least in part, to the site being evaluated (e.g., ground water and soil gas sampling points). 

• Option 3 –Score all populations in zones with actual or potential exposure. Under this option, in addition 

to actual contamination for sampled structures and inferred contamination for regularly occupied 

structures in the AOE and the ASC, a site’s score will include potential future contamination for regularly 

occupied structures in the Potential Ground Water Migration Zone (PMZ). The PMZ is defined as an 
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area between the ASC and a target distance limit encompassing the potential area where the ground water 

or soil gas contamination plume may migrate in the future. 

The three regulatory options are summarized and compared in Exhibit ES-1.
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EXHIBIT ES-1. OPTIONS CONSIDERED FOR THE PROPOSED RULE 

OPTION FOR SCORING POPULATIONS

POTENTIAL 

NUMBER OF 

INTRUSION SITES 

ASSESSED

POTENTIAL 

NUMBER OF NPL 

CALIBER 

INTRUSION SITES PROS/CONS CONSISTENCY WITH OTHER HRS PATHWAYS

Option 1 – Consider Only Actual and 

Inferred Exposures

• Includes all actual and inferred 

contamination for regularly occupied 

structures within the Area of Observed 

Exposure (AOE) 

• Does not include potential exposure for 

regularly occupied structures outside the 

AOE 

Less Least

Pro: Will have a high probability that 

identified releases pose a risk when 

scoring by zones of contamination

Con: Could fail to identify sites 

warranting placement on the NPL

because potential exposures will not 

be considered; does not consider 

future conditions/migration and may 

necessitate greater review of sites 

given a “no further action” designation

Option is consistent with:

• The soil exposure pathway in that it 

does not consider potential targets and 

infers Level II contamination

• All pathways in how Level I and II 

targets are weighted

Option 2 (Preferred Option) – Consider 

Actual, Inferred and Probable Exposures

• Includes those regularly occupied 

structures within the AOE and the Area of 

Subsurface Contamination (ASC) 

• Includes both actual contamination 

intrusion and probable exposure to 

subsurface contamination for regularly 

occupied structures within the AOE and 

ASC 

Less Middle

Pro: Would ensure that most releases 

posing a significant risk are identified 

by relying upon lines of evidence

Con: Could lead to an underestimate 

of the number of releases because 

future migration of subsurface 

contamination is not accounted for 

and/or because lines of evidence 

gathered during the Site Assessment 

process may be incomplete; does not 

consider future conditions/migration 

and may necessitate greater review of 

sites given a “no further action” 

designation

Option is consistent with:

• The soil exposure pathway in that there 

is no inference of contamination for 

Level I targets

• The soil exposure, air and surface water 

pathways in that there is inference of 

contamination for Level II targets

• The air pathway in that on-source 

targets are weighted (partially 

consistent – weighting values are 

different)

• All pathways in how Level I and II 

targets are weighted
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OPTION FOR SCORING POPULATIONS

POTENTIAL 

NUMBER OF 

INTRUSION SITES 

ASSESSED

POTENTIAL 

NUMBER OF NPL 

CALIBER 

INTRUSION SITES PROS/CONS CONSISTENCY WITH OTHER HRS PATHWAYS

Option 3 – Consider Actual, 

Inferred, Probable and Potential 

Exposures 

• Includes regularly occupied structures

within the AOE, the ASC and the

Potential Ground Water Migration Zone

(PMZ)

• Includes actual contamination intrusion,

probable and potential exposure to

subsurface contamination for structures

within the AOE, ASC and PMZ

• Includes unsampled structures, but are

considered to be potentially exposed

More Most

Pro: Would ensure that all releases 

posing a risk are identified 

Con: Could result in identification of 

low risk releases because not all 

identified releases will result in future 

exposure; limited rationale for 

projecting extent of PMZ; not assuming 

migration in all directions (i.e., <360 

degrees) could result in questioning 

the target delineation for ground water 

and air pathways

Option is consistent with:

• The air pathway in that there 2

different weightings for potential

targets

• The air pathway in that on-source

targets are weighted (partially

consistent – weighting values are

different)

• The ground water pathway in that the

same weighting values are used

• All pathways in how Level I and II

targets are weighted
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Assessment of Costs and Benefits

The analysis estimates costs of implementing the proposed rule. These costs include the cost of investigating SsI

at sites with probable SsI issues and the additional administrative cost of preparing HRS packages for sites that 

score 28.50 or higher due in part to SsI contamination. The analysis also qualitatively discusses the benefits of the 

proposed rulemaking, which include improved quality of information and more effective prioritization of 

remedial efforts by the Superfund program through a more comprehensive characterization of sites with SsI

threats. Although listing a site on the NPL may potentially lead to site remediation and potential improvements to 

human health, any such health benefits are realized at a later point in the Superfund process and are removed from 

the HRS scoring process.3

 Simply scoring a site with the HRS does not necessitate an improvement in human 

health. Therefore, any health benefits resultant from remediation of a site are contingent impacts and are not direct 

impacts of conducting an HRS evaluation. 

Affected Sites: To support the proposed rulemaking, EPA conducted a screening-level assessment of sites with 

potential or identified SsI threats. As a first step in collecting the list of sites potentially affected by the proposed 

rule, EPA consulted with site assessment experts that work in Superfund and other federal programs, including 

Brownfields, Resource Conservation and Recovery Act and other Federal/state programs. These experts used their 

professional knowledge and familiarity with their programs’ historical data to identify potential site candidates.

EPA also asked for input from state counterparts, in particular state programs that were known to have taken a 

more thorough review of the SsI pathway at sites. Through this process, EPA identified approximately 1,073 sites 

as potentially affected by the proposed rulemaking at the time of this analysis. These sites are not currently on the 

NPL, and all have a potential or identified SsI threat. Within the group of sites potentially affected by the 

proposed rule, EPA defined four categories:

1. Tier 4: Sites identified as having a suspected SsI threat based on EPA’s Superfund database and Agency

for Toxic Substances and Disease Registry keyword searches, as well as EPA or state self-identification,

but for which no sampling data were obtained;

2. Tier 3: Sites identified as having characteristics or evidence that indicate SsI may have occurred or will

occur;

3. Tier 2: Sites identified as having an SsI threat documented by subslab, crawl space, or indoor air

samples, but insufficient HRS-required evaluation factors to qualify for the NPL; and

4. Tier 1: Sites identified as having an SsI threat with documented actual exposure of a sufficient number of

targets with enough other HRS-required evaluation factors to suggest the site may qualify for the NPL.

Unit Costs: EPA used data from the Superfund Enterprise Management System (SEMS) during the 5-year period 

of FY2011 through FY2015 to estimate the typical number of sites assessed each year. EPA also developed a 

conceptual site model of a site with an SsI threat to identify unit costs associated with investigating a site with 

suspected SsI contamination as part of the HRS.4

3 Later remedial decisions that consider information collected under the proposed addition could separately have specific health benefits (e.g., reducing 

human exposure to hazardous substances), but these impacts are contingent upon a series of separate and often non-sequential actions that occur after listing 

a site on the NPL. The addition of subsurface intrusion to the HRS is several regulatory steps removed from realizing health benefits and therefore outside the 

scope of this regulatory impact analysis.

4 Superfund Enterprise Management System (SEMS) Accomplishment Reports data provided by Randy Hippen, EPA Office of Superfund Remediation and 

Technology Innovation (OSRTI), on October 30, 2015. The number of annual sites assessed between FY2011 and FY2015 ranged from 171 to 242. For purposes 

of this analysis a baseline of 200 assessments was selected as it was consistent with previous program activity. The EPA Superfund program is in the final 

stages of replacing the Comprehensive Environmental Response Compensation and Liability Act Information System (CERCLIS) data management system for 
ES-8 

Exhibit ES-2 identifies the numbers of sites evaluated and unit costs for the baseline and each regulatory scenario. 

In all scenarios, the analysis assumes that the program typically conducts assessments at approximately 200 sites

per year, and typically prepares 20 HRS packages per year at a cost of $65,000 per package.5 In the baseline 

scenario, all site assessments and HRS packages involve non-SsI sites. In the regulatory scenarios, the analysis 

assumes that some assessments and HRS packages would involve sites with SsI contamination replacing non-SsI 

sites. Site assessment unit costs for SsI sites incorporate the additional site inspection costs associated with 

investigating SsI threats. 6

 

EXHIBIT ES-2. UNIT VALUES USED TO ESTIMATE COST IMPACTS OF THE HRS SSI ADDITION UNDER THREE 

REGULATORY OPTIONS

BASELINE OPTION 1 OPTION 2 OPTION 3

Sites Assessed per Year

Non-SsI Sites 200 180 180 160

SsI Sites 0 20 20 40

Total Sites 200 200 200 200

HRS Packages per Year

Non-SsI Sites 20 19 18 16

SsI Sites 0 1 2 4 

Total Packages 20 20 20 20

Average Cost per Non-SsI Site Assessed $58,400 $58,400 $58,400 $58,400

Average Cost per SsI Site Assessed

High End n/a $107,000 $128,000 $132,000

Best Estimate n/a $80,900 $94,000 $97,800

Average Cost per HRS Package $65,000 $65,000 $65,000 $65,000

Total Costs and Benefits: The results of the analysis of the costs and benefits of the proposed rule are 

summarized in Exhibit ES-3. Total annual costs under Option 2 (the preferred option) are expected to range from 

$0.7 million to $1.4 million. Total annual costs in all scenarios are less than $3 million. 

The RIA does not provide a quantitative estimate of benefits of the proposed rule. Benefits of the rule are 

expected to be minimal, because the rule will not directly require actions that reduce risks. Any risk reduction that 

may result from the proposed action would come from future site-specific regulatory actions. However, 

qualitative benefits of this proposed action include improved quality of information and more effective 

 

Superfund site information, with the Superfund Enterprise Management System (SEMS) (hereinafter referred to interchangeably with the term EPA’s 

Superfund database).

5 The number and cost of HRS packages are based on data collected in support of Information Collection Request (ICR) 1488.08, provided by Randy Hippen, EPA 

Office of Superfund Remediation and Technology Innovation (OSRTI), on June 7, 2011. 

6 While the analysis portrays the various options as though they will result in additional expenditures for site assessments and HRS package preparations, in the 

context of a fixed site assessment budget, it is likely that the cost impacts of the proposed rule would manifest in a reduction in site assessment activity.
ES-9 

prioritization of remedial efforts by the Superfund program through a more comprehensive characterization of 

sites with SsI threats. For example, this proposed action could facilitate immediate removal actions if an early SsI 

investigation uncovers a significant threat.

Caveats and Limitations: Due to the limitations in data availability and uncertainties inherent in trying to predict 

future site assessment activities, this cost analysis made several simplifying assumptions in the development of a 

reasonable cost estimate for this proposed action. For example, the analysis did not consider whether the costs for 

investigating the SsI threat could be lower if other pathways (e.g., ground water) were investigated at the same 

time or if a pathway threat no longer needed to be investigated. Additionally, due to the ranges of cost estimates 

provided by data sources for SsI-related investigative activities, the analysis only estimated cost estimates using 

median and maximum task unit costs. Therefore, the analysis does not consider the possibility that future costs to 

investigate the SsI threat could be less than the median costs (e.g., due to improved sampling methods). 

The site assessment costs used in this analysis also represent a potential source of uncertainty. Costs provided by 

different data sources for the same investigative task, in some cases, have a wide range in values. To account for 

this potential variability in costs, during the evaluation of costs associated with investigating the SsI threat using a 

conceptual site model, EPA decided on a case-by-case basis whether to exclude outliers from the total SI cost 

estimate. For example, one dataset contained a cost estimate of $600/sample for Summa canister analysis, which 

appears to be an outlier on the high end. The $600 unit cost resulted in a cost of $45,600 to analyze 76 Summa 

canister samples (see Exhibit B-6), which is significantly higher than other estimates. 

Summary of Costs: 

Presented below is an example illustrating how the high end cost was derived for Option 1 (see Exhibit ES-3). 

The following formula was used to arrive at the high-end total cost of approximately $1 million for Option 1 (see 

Exhibit ES-2 for values): 

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA − AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA = AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA ∗ = $972,0007

 

7 Individual cost values were calculated using original unrounded input values; each final value presented in Exhibits ES-2 and ES-3 was rounded to three 

significant digits.
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EXHIBIT ES-3. SUMMARY OF COSTS AND BENEFITS OF PROPOSED HRS SS I REVISION (MILLION$)

TYPE OF IMPACT OPTION 1

OPTION 2 

(PREFERRED 

OPTION) OPTION 3

Costs

Annual Costs of Investigating SsI threats and of Preparing HRS Packages for SsI sites (million 2011$)

High-End Scenario $1.0 $1.4 $2.9

Best-Estimate Scenario $0.5 $0.7 $1.6

Benefits

Improved quality of information and more effective 

prioritization of remedial efforts by the Superfund program 

through a more comprehensive characterization of sites with 

SsI threats. 

Not quantifiable

Note: Because cost impacts are expected to be constant on an annual basis over time, presenting the net present value 

of costs would not add analytic value and is not presented here. Therefore, although alternative discount rates of seven 

percent and three percent were not considered, the costs presented in this exhibit satisfy OMB Circular A-4 and EPA 

policy requirements to annualize regulatory impacts using alternative discount rates of seven percent, three percent and 

zero percent (undiscounted).

Assessment of Demographic Impacts: Although the impacts of the proposed rulemaking are limited to increased 

EPA costs, it is possible that information collected under this rule will contribute to separate, future decisions to 

propose sites with SsI contamination for listing on the NPL and to undertake remediation. Because any 

subsequent change in risk or cost related to SsI sites would be contingent on future regulatory actions, any change 

in risk or cost related to site remediation would also be “contingent” impacts. While not a direct effect of the rule, 

one potential contingent impact of concern to EPA is the possibility that consideration of SsI sites might

contribute to future actions that would have disproportionate impacts on minority or low-income populations.8

The analysis assesses this possibility by examining the demographic characteristics of populations living within 1 

and 3 miles of sites potentially affected by the proposed action. 

The demographic analysis reveals that the areas around potentially affected sites have small but a statistically 

significant concentration of minority and low-income populations. In other words, the population surrounding 

potentially affected sites has a higher percentage of minority and low-income populations than the general 

population of the county in which the sites are located. This suggests that any remediation at sites associated with 

SsI contamination would be likely to reduce human health risk in the context of disproportionately high minority 

and low-income populations. Therefore, EPA does not anticipate any disproportionate adverse effects on these

communities, either as a direct or contingent impact of the proposed rule. Because SsI sites have the potential to 

pose a high level of risk to residents and occupants of other buildings in their vicinity, EPA expects that there will 

be a realignment and reprioritization of its internal resources to address SsI sites. If it is found that SsIcontaminated sites potentially pose a greater risk than other sites, then these sites will be prioritized over other 

sites without SsI contamination. EPA is not able to predict the location of the sites without SsI contamination or 

 

8 In the context of this analysis, “contingent impacts” refer to impacts of the proposed rule that are dependent on other potential actions that might occur 

outside of the proposed rule. The use of the word “contingent” in this analysis is unrelated to the “contingent valuation” methodology that economists use to 

estimate the value of nonmarket goods (e.g., clean air).
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demographic characteristics of populations living nearby. Additionally, because a precise geographic location

could not be determined for the majority of the sites (precise geographic coordinates were identified for 240 of 

approximately 1,073 sites), the result is an uneven distribution of sites used in the analysis. Additionally, to 

account for the range in sizes of potential sites, as well the uncertainty related to site extent and location, the 

analysis uses two distance rings (1- and 3-mile radii) for estimating affected populations near a site. EPA also 

conducted an analysis to determine if updated U.S. Census data would identify a reduction in the proportion of the 

population that is minority or below the poverty level near sites with potential SsI contamination. The results 

based on 2000 U.S. Census data, discussed above, were compared with 2009-2013 American Community Survey 

data. This analysis indicated that the proportion of the population that is minority or below the poverty level near 

sites with potential SsI threats did not decrease from 2000 to 2013. 
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Other Regulatory and Distributional Issues

As part of this RIA, EPA also assessed the proposed rule’s potential impacts related to a number of relevant 

executive orders and statutes, including the following:

• Executive Order 12866 – Regulatory Planning and Review;

• Executive Order 12898 – Environmental Justice;

• Executive Order 13045 – Protection of Children from Environmental Health Risks and Safety Risks; 

• Executive Order 13132 – Federalism;

• Executive Order 13175 – Consultation and Coordination With Indian Tribal Governments;

• Executive Order 13211 – Actions that Significantly Affect Energy Supply, Distribution, or Usage; 

• Executive Order 13563 – Improving Regulation and Regulatory Review; 

• Paperwork Reduction Act; 

• Regulatory Flexibility Act;

• Unfunded Mandates Reform Act; and

• National Technology Transfer and Advancement Act. 

EPA’s evaluation of the impacts of the proposed rule under all of these policies and statutes concludes that no 

significant impacts exist, due to the limited cost and narrow scope of the proposed action.
1 

1. Introduction

This document presents an analysis of the costs, benefits and economic impacts of the proposed amendment to the 

Hazard Ranking System (HRS) regarding identification of releases and threatened releases of hazardous 

substances, pollutants, or contaminants9

. The proposed rulemaking will add a subsurface intrusion (SsI) 

component to the existing soil exposure pathway of the U.S. Environmental Protection Agency’s (EPA) HRS. 

The HRS is the primary method EPA uses to identify the sites posing the greatest threat nationally for listing on 

the Superfund National Priorities List (NPL) under the Comprehensive Environmental Response, Compensation, 

and Liability Act (CERCLA) and the Superfund Amendments and Reauthorization Act (SARA). The economic 

assessment included in this analysis quantifies the expected cost impacts of the proposed action, in accordance

with the requirements of Executive Order 12866 and Office of Management and Budget (OMB) Circular A-4.10

The analysis characterizes the expected benefits of the rule and satisfies other administrative requirements 

established by statute or executive order. 

1.1. Background 

CERCLA was passed in Congress in 1980 and amended by SARA in 1986 in response to environmental and 

public health concerns over uncontrolled hazardous waste sites. CERCLA, as amended by SARA, established the 

Superfund program to respond to releases and threatened releases of hazardous substances. CERCLA Section 105 

requires EPA to establish criteria for determining priorities among releases or threatened releases of hazardous 

substances for the purpose of taking remedial action. 

Pursuant to section 105 of CERCLA, EPA established the HRS as a tool to identify and prioritize sites posing the 

most immediate and serious potential threats to human health and the environment. As originally promulgated (47 

FR 31180), the HRS evaluated sites based on three scoring pathways: ground water, surface water and air. The 

HRS was amended in 1990 (55 FR 51532) to include a soil exposure pathway. The HRS site score, which ranges 

from 0 to 100, is obtained by combining the scores of all pathways examined at a given site. A site receiving a 

score of 28.50 or higher is eligible for placement on the NPL, where it is targeted for further investigation and 

possible site remediation. Since the inception of the HRS in 1982, more than 1,700 sites have been placed on the 

NPL. 

EPA is now considering amending the HRS again to include consideration of subsurface intrusion. Subsurface 

intrusion is an issue at sites with subsurface contamination, where chemical contaminants (especially volatile 

substances) can enter into overlying structures. These contaminants can form vapors, which can pose a threat to 

individuals primarily through inhalation, but also through dermal contact, ingestion and fire or explosion hazards 

when concentrated. Currently, there is no mechanism in the HRS for evaluating threats to human health posed by 

subsurface intrusion. The existing pathways do not evaluate indoor air and site-related contaminants that may 

release vapors.

 

9 For the purpose of this regulatory impact analysis, the term “hazardous substances, pollutants or contaminants” will be referred to simply as “hazardous 

substances.”

10 Executive Order 12866, Regulatory Planning and Review, October 4, 1993; Office of Management and Budget, Circular A-4, September 17, 2003
2 

1.2. Need for Regulatory Action on HRS Rule

In order to implement the addition of an SsI contamination component to the HRS, EPA is considering amending 

the regulations at Title 40 of the Code of Federal Regulations (CFR) 300.425: Establishing remedial priorities. 

The agency believes that including the evaluation of SsI contamination in the HRS serves the public interest by 

widening the scope of evaluation of human health issues posed by Superfund sites. Consideration of SsI threats 

will enable EPA to meet the Congressional mandate to assess the relative degree of risk posed to human health by 

an actual or potential release of hazardous substances into the environment. EPA considers the addition of an SsI

component to the HRS to be consistent with CERCLA Section 105 and SARA because it will improve the 

agency’s ability to identify sites warranting further evaluation. Consideration of SsI threats also will enable EPA

to address risks posed by subsurface intrusion of contaminants into occupied structures for all populations who 

live and work in areas where releases to the subsurface may create exposures. Consideration of SsI threats will 

also support acceleration of cleanups where appropriate and return sites to productive use in a manner protective 

of human health and the environment. 

No mechanism for evaluating threats posed by SsI contamination currently exists within the HRS, and no other 

regulatory programs are available that consistently and permanently remediate the source of the threat posed by 

SsI contamination when it is the sole exposure route. 

Alternatives to Federal Regulatory Action

EPA considered, and ultimately rejected, the use of alternatives to Federal regulatory action to address the need to 

evaluate SsI threats.11 A critical factor in this consideration is the mandate under CERCLA Section 105 that EPA

implement the HRS to take into account “...to the extent possible the population at risk, the hazard potential of 

hazardous substances..., the potential for contamination of drinking water supplies and the potential for direct 

human contact.” Due to advances in technology since EPA last revised the HRS in 1990, SsI threats can now be 

evaluated comprehensively, improving the ability of EPA to prioritize releases at sites for further investigation.

EPA also considered whether existing Federal and non-Federal programs adequately address risks associated with 

SsI threats at contaminated sites. Under the existing HRS, several sites on the NPL have identified SsI-related 

health risks in later stages of site remediation (e.g., during remedial design or five- year reviews). For this reason, 

and consistent with the mandate under Section 105, EPA is adding an SsI component to the HRS. Considering SsI

contamination in the HRS would potentially speed the identification of risk at similar sites, and could contribute 

to a reduction in human exposures through earlier remediation, and possibly at a lower cost. In addition, some 

sites with SsI as the key exposure pathway may not currently score 28.50 on the HRS in spite of actual or 

potential human exposure. 

In addition to the Superfund removal and remedial programs, SsI threats are currently addressed under the 

authority of several other programs, including Superfund enforcement actions; the Superfund Alternative 

Approach; Superfund Removal; Resource Conservation and Recovery Act (RCRA) Corrective Action and RCRA 

enforcement; Brownfields; and State Superfund and voluntary cleanup programs. In addition, EPA examined the 

 

11 The alternatives to this proposed regulatory action considered by EPA are discussed in further detail in section V.A.2, What Alternative Regulatory Options to 

this Action Were Considered by EPA?, of the preamble to the SsI proposed rulemaking and section 2.1.b, Alternative Methods Considered for Addressing 

Subsurface Intrusion Sites, of the proposed rulemaking’s technical support document. 
3 

possibility of expanding use of the listing mechanism.12 However, no other authority consistently and 

comprehensively addresses SsI contamination across all potential sites, particularly when SsI is the key exposure 

pathway. In particular, state programs vary significantly in addressing SsI threats. Not all states have SsI

programs, and states with programs vary in their authority, resources and remediation criteria. 

The Interstate Technology and Regulatory Council’s Vapor Intrusion Team developed and conducted an on-line 

survey of state, federal and tribal agencies regarding SsI regulations, policy and guidance.13 Ninety-six percent of 

survey respondents consider SsI a concern, though only eleven percent have a procedure for evaluating SsI 

codified into law. A majority of the states that responded to the survey expressed that their procedures for 

addressing vapor intrusion were only informally adopted by their agencies, with most deferring to EPA guidance. 

Finally, EPA considered whether the 2002 OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor 

Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance), in addition to guidance 

published by states, might provide an alternative mechanism for addressing SsI. The available state and federal 

guidance provide useful tools and techniques for helping to conduct site assessments, which EPA hopes to apply 

in implementing this regulation.14 However, they do not establish a comprehensive science and legal framework 

for addressing SsI issues.

1.3. Summary of Proposed Rule

The proposed addition of an SsI component to the HRS soil exposure pathway would address sites nationwide 

where SsI contamination may be a concern but the sites do not qualify for the NPL using the present HRS. 

Through this proposed rulemaking, EPA would augment the HRS and its process for evaluating four pathways by 

considering various options for incorporating an SsI screening process into the existing HRS without altering the 

existing HRS structure and methodologies. 

The HRS is a numerically based screening tool and uses information from initial, limited investigations to assess 

the relative threat that sites with actual or potential contaminant releases pose to human health or the environment. 

Currently, HRS scoring is based on an evaluation of the release of hazardous substances from sites via four 

pathways: surface water migration, ground water migration, air migration and soil exposure. The HRS identifies 

the relative risk among sites with the calculated score reflecting the probability that one site poses a greater threat 

than another.

1. The ground water migration pathway evaluates the likelihood that hazardous substances will migrate to 

ground water and contaminate aquifers and drinking water wells that draw on those aquifers. 

2. The surface water migration pathway evaluates the likelihood that hazardous substances can enter 

surface water and affect people or the environment. Threats to humans from this pathway include 

 

12 EPA also considered the use of mitigation systems rather than source control at sites with SsI contamination. While mitigation systems can control human 

exposures, these systems have several limitations, including the need for multiple blowers at complex structures and the impact of these systems on climate 

control costs in large structures; the need for long-term monitoring due to long time frames for migration and exposure; and the need to maintain the 

systems to address the impacts of contamination.

13 The full survey and results are available at http://www.itrcweb.org/vaporintrusionresources/ITRC_VI_Survey_8-17-05/ITRC_1_VI_Survey_Index. 

14 See, for example, OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air, Office of 

Solid Waste and Emergency Response, U.S. Environmental Protection Agency, June 2015, and Final Guidance for the Evaluation and Mitigation of Subsurface 

Vapor Intrusion to Indoor Air, Department of Toxic Substances Control, California Environmental Protection Agency, October 2011. 
4 

drinking water, the human food chain (i.e., contaminants accumulate in the aquatic organisms that 

humans in turn consume) and sensitive environments. 

3. The air migration pathway evaluates the likelihood of release of hazardous substances into the 

atmosphere and the number of people and sensitive environments actually or potentially exposed to 

hazardous substances carried in the ambient air, including gases and particulates.

4. The soil exposure pathway evaluates the potential threats to humans and terrestrial environments posed 

by direct, physical contact with, and subsequent ingestion of, hazardous substances. This pathway 

includes threats to people living on property where hazardous substances are present in the 

surface/subsurface, including contaminated soils, and to people living nearby with access to the 

contaminated area. 

The HRS was last revised in 1990, but did not include an SsI component as the science was not sufficiently 

advanced to ensure the effectiveness of its use in a screening tool. The ground water and soil exposure pathways 

consider contaminated ground water and contaminated surfaces (e.g., surface soils), respectively, but neither 

addresses vapor-phase contaminants that can enter buildings and pose a threat to occupants. The air migration 

pathway considers the threat posed by contaminants released to ambient (atmospheric) air, but does not address 

indoor air, and has no subsurface component. The surface water pathway is not applicable to SsI contamination 

because contaminated surface water bodies are extremely unlikely to be a source of SsI contamination into 

occupied structures. Therefore, although the purpose of the HRS is to assess the relative degree of risk to human 

health and the environment posed by the release or potential release of contaminants, the HRS currently contains 

no mechanism for evaluating the threat to human health posed by SsI contamination. 

This proposed rule mandates only the addition to the HRS of the capability to rank sites with SsI threats. It does 

not specifically mandate how, to what sites, and under what conditions the HRS will be applied. Moreover, site 

listings and accompanying potential response actions are not directly affected by this proposed rulemaking. The 

primary purpose of the NPL is to serve as an informational and management tool. The identification of a site for 

the NPL is intended to guide EPA in determining which sites warrant further investigation to assess the nature and 

extent of the human health and environmental risks associated with a site, and to determine what Federallyfinanced remedial action(s), if any, may be appropriate. The NPL also serves to notify the public of sites EPA

believes warrant further investigation. Sites on the NPL are then further investigated to determine the nature and 

extent of the threat and whether cleanup of the site under EPA’s Superfund Remedial program is warranted. 

Placing a site on the NPL does not specifically mandate any specific remedial or removal action. In some cases, 

further investigation may conclude that no remedial action is necessary. 

Scope of the Effects of the Proposed Rule

Contaminated sites are evaluated through EPA’s Site Assessment program to determine their potential to be added 

to the NPL. The evaluation of sites involves a series of initial, limited site investigations and data collection 

efforts related to site conditions. This process is implemented by the EPA regional site assessment programs. 

Investigations often include a Preliminary Assessment, Site Inspection (SI), and related investigations. The HRS 

evaluation uses the information obtained from these initial, limited investigations to rank sites according to the 

risk they may pose, relative to other sites, and determine if further investigation is warranted through the 

Remedial or Removal programs.
5 

Each EPA region has a set budget for conducting site assessments. The sites in each EPA region of the country 

are reviewed to determine those that pose the highest risk and are prioritized accordingly. The addition of an SsI 

component to the HRS is not expected to result in additional site assessment funding to account for any increase 

in site assessment costs. Instead, the pipeline of sites will continue to be reviewed under the site assessment 

process. If it is found that SsI-contaminated sites potentially pose a greater risk than other sites, then these sites 

will be prioritized over other sites with contamination not resulting from SsI. 

This proposed addition to the HRS will have the most significant impact on EPA’s Superfund cleanup program. 

The current HRS considers releases to the ground water, surface water and air, as well as direct exposure to 

contamination such as soil in identifying the sites that most warrant g further investigation. If promulgated, this 

proposed rule will not impact the way the current HRS addresses these releases. However, in the course of present 

HRS assessments, sometimes subsurface intrusion issues are coincident with a ground water or soil contamination 

problem. The HRS presently does not consider the threat posed by sites with subsurface intrusion problems and 

direct human exposure, when ground water is not being used as a drinking water source or surficial soils are not 

contaminated. If promulgated, this proposed rule will for the first time allow the EPA site assessment program to 

address sites with only subsurface intrusion issues which do not have any coincidental exposure from another 

pathway already evaluated by the HRS. Furthermore, proposal of this addition will not disrupt EPA’s listing of 

sites. However, it could lead to an increase in some site assessment activities and related costs.

Although this proposed addition will impact both resources and costs to federal cleanup programs, EPA does not 

expect that this proposed change will result in additional site assessments being conducted per year or placement 

of more sites on the NPL per year. Rather, given potentially limited budgets and the possibility of increased costs 

for an SsI site assessment, EPA may conduct fewer assessments per year. The pipeline of sites will be reviewed to 

identify those sites that pose the highest risk and prioritized accordingly. This is not a change to how EPA 

currently evaluates and prioritizes sites for the NPL; EPA will simply have an additional mechanism to address 

sites that pose the greatest risk. Because assessing the worst sites first is a priority, EPA will continue to identify 

the sites posing the highest risk or potential risk and develop a strategy to assess those sites in a timely manner, 

while balancing their other site assessment needs.

The proposed rule will also affect how EPA, federal agencies and its State Cooperative Agreement partners 

conduct site assessments and HRS scoring. The CERCLA site assessment program is operated strictly by the 

public sector using funds that are appropriated annually and reside in the Superfund Trust Fund. State and tribal 

partners may receive financial assistance from EPA to evaluate sites through a Cooperative Agreement. EPA and 

states or tribes collaborate closely throughout the Cooperative Agreement process, particularly when identifying 

sites to be evaluated and establishing priorities for performing evaluations. As necessary, sites where subsurface 

intrusion threats exist may then be evaluated using the HRS and, if warranted, proposed for placement on the 

NPL. The proposed rule does not impose any costs on outside parties or any private entity; it does not require that 

EPA will necessarily undertake response actions, nor does it require any action by a private party or determine 

liability for site response costs. Costs are limited to screening relevant sites for SsI during site inspections and the 

resulting HRS evaluation and documentation record preparation. Costs that arise from site remedial responses are 

the result of site-specific decisions made post-listing, not directly from the act of listing itself. 

As discussed above, no other authority consistently and comprehensively addresses SsI contamination across all 

potential sites, particularly when SsI is the key exposure pathway. While most states have identified SsI sites as a 

high priority, not all states have SsI programs, and states with programs vary in their authority, resources and 

remediation criteria. A redirection of resources available to the states through Cooperative Agreement funding is 

expected to provide for greater national consistency in the identification and evaluation of SsI sites. Additionally, 
6 

EPA issued new vapor intrusion guidance in June 2015, OSWER Technical Guide for Assessing and Mitigating 

the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air, which together with this proposed 

rule, EPA expects will provide a comprehensive framework to guide evaluation of SsI sites across the country.

Additional Impacts Associated with Future Regulatory Actions that are Enabled by the Proposed 

Rule

Scoring a site in the HRS imposes no costs on any private entity. Once EPA or a State conducts a site assessment 

and determines that a site is NPL-caliber, additional regulatory actions must be taken before any costs or other 

impacts would occur. The information provided on SsI contamination through a revised HRS might be used in 

several ways. For example, a State may opt to address the SsI concern through state statutory and regulatory 

authorities; these subsequent site-specific state actions could potentially impose additional impacts on State 

taxpayers or on private entities that may be liable under state law. Placing a site on the NPL also imposes no

impacts on any private entity, because placement on the NPL does not ascribe liability or in any way impose 

requirements on private parties. Later decisions that consider information collected under the proposed rule could 

separately have specific economic costs and benefits (e.g., remediation costs and reduced risk), but these impacts 

are contingent on separate actions.15 The addition of SsI to the HRS is several regulatory steps removed from 

imposing any costs on private entities.

 

1.4. Alternative Regulatory Options

This analysis considers the economic impacts of three regulatory options that vary in how a site with a potential 

SsI threat will be scored for the HRS:

• Option 1 – Score only populations and regularly occupied structures within a zone defined by exposures 

above background and resulting from subsurface intrusion attributable to the site being evaluated. Under 

this option, scoring will include both actual contamination for sampled structures and inferred 

contamination for regularly occupied structures within the Area of Observed Exposure (AOE). The AOE 

is bounded by structures with documented contamination subsurface intrusion attributable to the site 

being evaluated. 

• Option 2 (the preferred option) – Score only populations and regularly occupied structures within zones 

with actual exposure, as well as those above demonstrated subsurface contamination. Under this option, a 

site’s score will include actual contamination for sampled structures and inferred contamination both for 

regularly occupied structures in the AOE and for regularly occupied structures in the Area of Subsurface

Contamination (ASC). The ASC is defined as an area outside of the AOE by sampling locations with 

documented contamination significantly above background and the significant increase can be attributed 

at least in part to the site being evaluated (e.g., ground water and soil gas sampling points). 

• Option 3 – Score all populations in zones with actual or potential exposure. Under this option, in addition 

to actual contamination for sampled structures and inferred contamination for regularly occupied 

 

15 It is important to recognize that when a site is scored and determined to warrant further investigation, community members may experience short term 

indirect (contingent) social costs and benefits. For example, release of a site score may affect property values in surrounding areas either by signaling 

contamination or by signaling intent to remediate known contamination. Similarly, the costs of remediating the site and the benefits of identifying and 

mitigating risk would be informed in part by the information provided under the proposed rule.
7 

structures in the AOE and the ASC, a site’s score will include potential future contamination for regularly 

occupied structures in the Potential Ground Water Migration Zone (PMZ). The PMZ is defined as an 

area between the ASC and a target distance limit encompassing the potential area where the ground water 

or soil gas contamination plume may migrate in the future. 

The three regulatory options are summarized and compared in Exhibit 1-1. 

1.5. Scope of Analysis

Within the constraints of data availability, this analysis attempts to capture all quantifiable and qualitative impacts 

of this proposed rule. Costs of implementing the proposed rule include the costs of investigating SsI

contamination at sites with probable SsI threats and the additional administrative costs of conducting HRS 

evaluations for sites that score 28.50 or higher due in part to SsI contamination. The analysis compares the costs 

of the three regulatory options presented in section 1.4 above. While the analysis portrays the various options as 

though they will result in additional expenditures for site assessments and HRS package preparations, in the 

context of a fixed site assessment budget, it is likely that the cost impacts of the proposed rule would manifest in a 

reduction in site assessment activity, and would result in no incremental costs at all. 

The analysis qualitatively discusses the potential benefits of adding an SsI component to the HRS. These potential 

benefits include, among others, improved quality of information about SsI threats; more effective prioritization of 

remedial efforts by the Superfund program through a more comprehensive characterization of sites with SsI 

threats; and alerting the Superfund removal program to early risks which may be mitigated through taking an 

immediate action.

Finally, this Regulatory Impact Analysis discusses the impact of this action within the context of relevant 

executive orders and statutes. Because the costs of the proposed rule are expected to be small (i.e., below $3 

million per year), this document does not include a separate analysis of potential economic impacts (e.g., job 

impacts, impacts on trade, impacts on productivity). 
8 

EXHIBIT 1-1. OPTIONS CONSIDERED FOR THE PROPOSED RULE 

OPTION FOR SCORING POPULATIONS

POTENTIAL 

NUMBER OF 

INTRUSION SITES 

ASSESSED

POTENTIAL 

NUMBER OF NPL 

CALIBER 

INTRUSION SITES PROS/CONS CONSISTENCY WITH OTHER HRS PATHWAYS

Option 1 – Consider Only Actual and 

Inferred Exposures

• Includes all actual and inferred 

contamination for regularly occupied 

structures within the Area of Observed 

Exposure (AOE) 

• Does not include potential exposure for 

regularly occupied structures outside the 

AOE 

Less Least

Pro: Will have a high probability that 

identified releases pose a risk when 

scoring by zones of contamination

Con: Could fail to identify sites 

warranting further investigation

because potential exposures will not 

be considered; does not consider 

future conditions/migration and may 

necessitate greater review of sites 

given a “no further action” designation

Option is consistent with:

• The soil exposure pathway in that it 

does not consider potential targets and 

infers Level II contamination

• All pathways in how Level I and II 

targets are weighted

Option 2 (Preferred Option) – Consider 

Actual, Inferred and Probable Exposures 

• Includes those regularly occupied 

structures within the AOE and the Area of 

Subsurface Contamination (ASC) 

• Includes both actual contamination 

intrusion and probable exposure to 

subsurface contamination for regularly 

occupied structures within the AOE and 

ASC 

Less Middle

Pro: Would ensure that most releases 

posing a significant risk are identified 

by relying upon lines of evidence

Con: Could lead to an underestimate 

of the number of releases because 

future migration of subsurface 

contamination is not accounted for 

and/or because lines of evidence 

gathered during the Site Assessment 

process may be incomplete; does not 

consider future conditions/migration 

and may necessitate greater review of 

sites given a “no further action” 

designation

Option is consistent with:

• The soil exposure pathway in that there 

is no inference of contamination for 

Level I targets

• The soil exposure, air and surface water 

pathways in that there is inference of 

contamination for Level II targets

• The air pathway in that on-source 

targets are weighted (partially 

consistent – weighting values are 

different)

• All pathways in how Level I and II 

targets are weighted
9 

OPTION FOR SCORING POPULATIONS

POTENTIAL 

NUMBER OF 

INTRUSION SITES 

ASSESSED

POTENTIAL 

NUMBER OF NPL 

CALIBER 

INTRUSION SITES PROS/CONS CONSISTENCY WITH OTHER HRS PATHWAYS

Option 3 – Consider Actual, Inferred, 

Probable and Potential Exposures 

• Includes regularly occupied structures 

within the AOE, the ASC and the 

Potential Ground Water Migration Zone 

(PMZ)

• Includes actual contamination intrusion, 

probable and potential exposure to 

subsurface contamination for regularly 

occupied structures within the AOE, ASC 

and PMZ

• Includes unsampled structures, but are 

considered to be potentially exposed

More Most

Pro: Would ensure that all releases 

posing a risk are identified 

Con: Could result in identification of 

low risk releases because not all 

identified releases will result in future 

exposure; limited rationale for 

projecting extent of PMZ; not assuming 

migration in all directions (i.e., <360 

degrees) could result in questioning 

the target delineation for ground water 

and air pathways

Option is consistent with:

• The air pathway in that there 2 

different weightings for potential 

targets

• The air pathway in that on-source 

targets are weighted (partially 

consistent – weighting values are 

different)

• The ground water pathway in that the 

same weighting values are used

• All pathways in how Level I and II 

targets are weighted
10

1.6. Organization of Document 

The remainder of this document is organized as follows: 

• Chapter 2: Sites Affected by the Proposed Rule. This chapter describes how EPA identified and 

characterized sites potentially affected by the proposed rule. 

• Chapter 3: Impacts of the Proposed Rule. This chapter presents quantitative estimates of the cost 

impacts of the proposed rule and includes a qualitative discussion of expected benefits of the rule.

• Chapter 4: Other Statutory and Executive Order Analyses. This chapter summarizes analyses required

by applicable statutes or executive orders, including impacts on low-income and minority populations; 

children’s health effects; federalism implications; effects on tribal governments; and a demographic 

analysis to assess the potential for disproportionate effects on low-income and minority populations. 

• Chapter 5: Summary. This chapter compares the costs of the proposed rule across the three regulatory 

options and includes a discussion of the rationale for selection of the preferred option. 
11

2. Sites Affected by the Proposed Rule

At some sites with subsurface contamination (e.g., chemical spills, leaks from underground storage tanks), many 

hazardous substances, especially volatile organic compounds, have been shown to migrate into the indoor air 

spaces of overlying or nearby structures. The most common hazardous substances that have been shown to 

migrate into indoor air include mercury, tetrachloroethylene, trichloroethylene, vinyl chloride carbon tetrachloride 

and naphthalene. 

To support the proposed rulemaking, the U.S. Environmental Protection Agency (EPA) conducted a screeninglevel assessment of sites with potential or identified subsurface intrusion (SsI) threats. As a first step in collecting 

the list of sites potentially affected by the proposed rule, EPA consulted with site assessment experts that work in 

Superfund and other federal programs, including Brownfields, Resource Conservation and Recovery Act and 

other Federal/state programs. These experts used their professional knowledge and familiarity with their 

programs’ historical data to identify potential site candidates. EPA also reached out to state counterparts, in 

particular state programs that were known to have taken a more thorough review of the SsI pathway at sites. 

These efforts to identify and classify sites that may pose a subsurface intrusion threat resulted in the identification 

of 1,073 sites that may or may not qualify for the National Priorities List (NPL) but are suspected of having vapor 

intrusion issues. (See Appendix A of the Technical Support Document for this proposed addition (Proposal TSD) 

for the inventory of vapor intrusion sites.) Many of the sites in this inventory are currently listed in the EPA’s 

Superfund database16. These sites are not currently on the NPL, and all have a potential or identified SsI threat.17

Within the group of sites potentially affected by the proposed rule, EPA defined four categories or tiers of sites: 

1. Tier 4: Sites identified as having a suspected subsurface intrusion threat based on EPA’s Superfund 

database and Agency for Toxic Substances and Disease Registry (ATSDR) key word searches, as well as 

EPA or state self-identification, but for which no sampling data were obtained; 

2. Tier 3: Sites identified as having characteristics or evidence that SsI (e.g., volatile hazardous substance in 

ground water) may have occurred or will occur; 

3. Tier 2: Sites identified as having an SsI threat documented by subslab, crawl space, or indoor air samples 

but insufficient HRS-required evaluation factors to qualify for the NPL; and 

4. Tier 1: Sites identified as having an SsI threat with documented actual exposure of a sufficient number of 

targets and sufficient other HRS-required evaluation factors to suggest the site may qualify for the NPL. 

These categories are summarized in Exhibit 2-1. 

 

16 The EPA Superfund program is in the final stages of replacing the Comprehensive Environmental Response Compensation and Liability Act Information System 

(CERCLIS) data management system for Superfund site information, with the Superfund Enterprise Management System (SEMS) (referred interchangeably with 

the term EPA’s Superfund database).

17 The list of potentially affected sites discussed in this RIA represents information compiled and evaluated to date as part of an ongoing data collection effort. 

The full inventory of sites affected by this rule continues to be refined and updated. The sites identified as part of the site inventory are not currently on the 

NPL. The sites currently part of the inventory of sites are all in varying stages of site assessment and only once the rule addition is promulgated and further 

information gathered, will it be known if these sites will be NPL-eligible.
12

EXHIBIT 2-1. CATEGORIES OF SITES POTENTIALLY AFFECTED BY THE PROPOSED RULEMAKING 

CATEGORY POTENTIAL IMPACT

NUMBER OF SITES 

IDENTIFIED1,2

Tier 4: Sites with a suspected SsI threat Site assessments for SsI are possible. 328

Tier 3: Sites with a probable SsI threat Site assessments for SsI are probable. 532

Tier 2: Sites with an identified SsI threat Site assessments for SsI are probable. 

HRS evaluations are possible.

202

Tier 1: Sites that currently may not score

above 28.50 without considering SsI in the 

HRS

HRS evaluations are probable; 

contingent impacts are possible if 

separate regulatory action is taken. 

11

Source: Technical Support Document for U.S. EPA’s Proposed Rule for Addition of a Subsurface Intrusion 

Component to the Hazard Ranking System, Appendix A, Inventory of Subsurface Intrusion Sites (2015). 

Note: 

1. Site numbers exclude current and former National Priorities List (NPL) sites and are based on a 

preliminary EPA Regional Office review of sites using readily available data; numbers are not 

representative of the total universe of possible SsI sites. NPL sites are excluded because they are not 

expected to be affected by the impacts of the proposed rule (i.e., SsI investigation in site 

assessments and HRS evaluations for sites with an SsI threat). The sites identified as part of the site 

inventory are not currently on the NPL and are all in varying stages of site assessment and only once 

the rule addition is promulgated and further information gathered, will it be known if these sites will 

be NPL-eligible.

2. Sites classified as Tiers 2, 3, and 4 are not currently on the NPL, but based on available information 

were determined to have possible vapor intrusion threats. Insufficient information is available to 

evaluate their eligibility for the NPL.

EPA is also considering sites with another form of subsurface intrusion, namely, intrusion of contaminated ground 

water into regularly occupied structures—which is an emerging issue. For example, a site was discovered where 

shallow (surficial) ground water contaminated with chromium had intruded into residential basements and after 

the water receded, or evaporated, a precipitate of chromium remained as a residue. The presence of this residue 

posed a significant threat to public health; however, the site could not be evaluated under the current HRS due to 

the lack of a mechanism to evaluate human exposure resulting from intrusion of contaminated ground water 

(subsurface intrusion contamination). The only viable option to place the site on the NPL was to rely on ATSDR 

to make a determination that the exposure at the site posed a significant threat to public health. The decision to 

include sites on the NPL based on a determination by the Agency for Toxic Substances and Disease Registry is 

made infrequently because the HRS is the primary mechanism for placing a site on the NPL. 

EPA regional site assessment programs have identified 7 additional sites where intrusion of contaminated ground 

water is a potential issue and the related threat cannot be evaluated using the current HRS. Under the proposed SsI 

addition, ground water intrusion would be evaluated using current conditions, which may involve situations where 

metals have precipitated from water or where volatile substances have entered a structure via infiltrating ground 

water. As EPA further explores this emerging issue, the agency considers it likely that other ground water 

intrusion sites requiring evaluation will be identified. 

This inventory of sites, identified by EPA, with a possible subsurface intrusion threat, is not representative of the 

magnitude of the potential scope of sites with subsurface intrusion contamination. EPA identified these sites 

based on currently available information to initially assess the subsurface intrusion problem. This list of sites 

illustrates that there currently exists at least 1,073 sites that have significant actual or potential human exposure 
13

due to subsurface intrusion, but because of the shortcomings of the 1990 HRS cannot be evaluated to determine if 

they warrant addition to the NPL. 

It is also important to emphasize that the inventory of sites compiled (where subsurface intrusion has been 

identified as a possible issue) does not represent a list of sites that will be placed on the NPL. EPA recognizes 

that, in many instances, additional information is needed to verify the presence, and to determine the 

nature/extent, of a subsurface intrusion problem. As such, the inventory should not be considered as a list of NPL 

candidate sites.

In Chapter 4, the analysis of possible indirect (contingent) demographic impacts uses data characterizing 

populations in the areas surrounding sites potentially affected by the proposed rulemaking to identify potential 

impacts to low-income and minority communities. Although this component does not reflect a representative 

sample of the total universe of possible SsI sites, EPA determined the group of potentially affected sites to be 

sufficiently indicative of possible SsI sites for purposes of identifying potential environmental justice concerns. 
14

3. Impacts of the Proposed Rule

3.1. Introduction

This Regulatory Impact Analysis (RIA) uses available data from Information Collection Review (ICR) 

documents, the U.S. Environmental Protection Agency (EPA) Regional Offices and other sources to quantify the 

expected costs of the proposed rule. As described in Chapter 1, the proposed rule is a narrow technical 

modification of the Hazard Ranking System (HRS). For the regulatory options examined in this analysis, the 

primary impact of the proposed action would be that the Superfund program would routinely consider subsurface 

intrusion (SsI) threats in site assessments. In addition, EPA expects that a number of sites investigated for SsI will 

achieve HRS scores of 28.50 or higher, resulting in increased administrative effort to prepare and evaluate listing 

packages. 

Executive Order 12866 requires that RIAs evaluate whether regulatory actions are “significant” rulemakings; one 

determination of significance is whether annual cost impacts exceed $100 million. To determine whether the 

annual cost of the proposed rulemaking exceeds the $100 million threshold, this analysis considers the following 

costs that would result from the proposed amendment to the HRS: 

• Cost to conduct SsI investigations, specifically site inspections (SIs) and expanded site inspections (ESIs) 

for sites with a probable SsI threat. 

• Cost to prepare HRS packages for sites that score 28.50 or higher based entirely or in part on 

consideration of an SsI threat. 

To differentiate the incremental benefits and costs of the proposed rule from baseline benefits and costs of the 

Superfund program, the analysis compares regulatory scenarios—in which the HRS is modified to consider SsI

threats according to the three regulatory options described in Chapter 1—to a baseline scenario, in which the HRS 

remains unchanged. Note that although the analysis portrays the various options as though they will result in 

additional expenditures for site assessments and HRS package preparations, in the context of a fixed site 

assessment budget, it is likely that the cost impacts of the proposed rule would manifest in a reduction in site 

assessment activity, and would have little or no incremental cost. 

In this chapter, the RIA quantitatively estimates the costs that will be an impact of the proposed action, comparing 

the costs across the three regulatory options. The chapter outlines the cost estimation methodology, including the 

key assumptions used to define the baseline and regulatory scenarios, and presents cost estimates for each option. 

Benefits of the proposed rule are expected to be limited and are therefore discussed qualitatively at the end of this 

chapter. 

3.2. Cost Estimation Methodology

This section presents the methodology used to estimate the two categories of cost impacts considered in the 

analysis. For the baseline scenario and for each regulatory option, the analysis first identifies values for the 

following variables: 

1. Number of site assessments at SsI and non-SsI sites.

2. Number of HRS packages prepared for SsI and non-SsI sites.
15

3. Average cost per site assessment at SsI and non-SsI sites.

4. Average cost per HRS package prepared for SsI and non-SsI sites.

For each regulatory option, the analysis estimates the average cost per site assessment at SsI sites for both a highend regulatory scenario, using the upper range of the estimated costs of a site investigation for an SsI site, and a 

best-estimate regulatory scenario, using the median estimated costs of an SsI investigation. 

The remainder of this section discusses how the analysis defines the baseline and regulatory scenarios and 

provides additional detail on how the analysis models the cost of site assessments at SsI and non-SsI sites.

3.2.1. Characteristics of the Baseline Scenario

The baseline scenario is defined as follows:

• SsI is not currently considered during site assessments or in the HRS. 

• The Superfund program typically assesses approximately 200 sites per year.

• The Superfund program typically prepares 20 HRS packages per year at a cost of $65,000 per package.18

The assumption of 200 sites assessed per year is consistent with the average number of sites assessed annually, 

based on data from EPA’s Superfund database during the 5 year period between 2011 and 2015.19 

3.2.2. Characteristics of the Regulatory Scenarios

The three regulatory options evaluated in this RIA are summarized in Exhibit 1-1. To estimate the costs 

associated with each option, the analysis makes the following assumptions, common to all three options: 

• For assessments of sites with SsI threats, only the costs of SIs and ESIs will change because evaluation of 

SsI threats occurs only during these investigations. Costs for other site assessment activities (i.e., 

preliminary assessments, integrated assessments and site reassessments) will be the same as for non-SsI

sites.

• All new SIs and ESIs for SsI will take place at sites that would not receive site assessments absent the 

regulation. This assumption is conservative because SsI threats will likely be investigated in conjunction 

with other pathways, such as ground water migration or soil exposure. 

• New site assessments for SsI will replace lower-priority site assessments at non-SsI sites that are expected 

to take place in the baseline scenario. 

• New HRS packages for sites scoring 28.50 or higher will be prepared for sites that score solely based on 

SsI or based on SsI combined with other factor/pathway scores. 

 

18 The number and cost of HRS packages are based on data collected in support of Information Collection Request (ICR) 1488.08, provided by Randy Hippen, 

EPA OSRTI, on June 7, 2011.

19 SEMS Accomplishment Reports data provided by Randy Hippen, EPA Office of Superfund Remediation and Technology Innovation (OSRTI), on October 30, 

2015. The number of annual preliminary assessments conducted between FY 2011 and FY 2015 ranged from 171 to 242. For purposes of this analysis a baseline 

of 200 assessments was selected as it was consistent with previous program activity.
16

• New HRS packages prepared for SsI sites will replace HRS packages for lower-priority sites expected to 

be prepared in the baseline scenario.

• The cost of preparing HRS packages for SsI sites will be the same as the cost for non-SsI sites: $65,000 

per site.

• Because of the uncertainty involved in determining the costs of evaluating SsI threats as part of the site 

assessment process, the analysis will use a range of values to represent the costs of SIs and ESIs for SsI. 

These values will be presented as high-end and best-estimate scenarios for each option. 

• The rule will not create any backlog effects (e.g., in which a larger number of sites are identified in initial 

years, then the number goes down over time). 

In addition, to compare costs across the three regulatory options, the analysis makes the following option-specific 

assumptions:

• For Option 1, the analysis assumes that the Superfund program will conduct 20 site assessments for SsI

and prepare one HRS package for SsI sites each year. 

• For Option 2, the analysis assumes that the Superfund program will conduct 20 site assessments for SsI

and prepare two HRS packages for SsI sites each year. 

• For Option 3, the analysis assumes that the Superfund program will conduct 40 site assessments for SsI

and prepare four HRS packages for SsI sites each year. 

The assumption that the Superfund Office will assess 20 SsI sites in place of non-SsI sites under Options 1 and 2 

is based on a survey EPA conducted of EPA Regional Superfund Offices indicating that approximately 10 percent 

of sites assessed will likely have SsI threats.

20 EPA considered the different thresholds and methods that would be 

used for each of the regulatory options to investigate SsI threats and determined that the modeling approach used 

in Option 3 would bring a larger number of sites into the scope of analysis for SsI threats. Accordingly, the 

analysis assumes that under this option, EPA would conduct 40 site assessments at SsI sites each year. 

The aforementioned survey of EPA Regional Offices also estimates that approximately one percent of site 

assessments are expected to result in HRS scores of 28.50 or higher, based in part or entirely on SsI threats. This 

percentage is based on the number of Tier 1 sites identified as having an SsI threat with documented actual 

exposure of a sufficient number of targets and other HRS-required evaluation factors to suggest the site may 

qualify for the National Priorities List (NPL). (Please see section 2 of this document for additional information on 

the inventory of sites identified with possible vapor intrusion threats.) These sites would be new sites that may not 

have previously qualified for placement on the NPL. However, given limited budgets, the addition of SsI to the 

HRS will not result in more sites listed per year. Rather, the pipeline of sites will be reviewed and if the SsIcontaminated sites identified potentially pose a greater risk than other sites, they will be more highly prioritized. 

This is not a change to how EPA currently lists sites on the NPL; EPA simply would have an additional 

mechanism to address sites that pose the greatest risk.

For Option 2, the analysis therefore assumes that the Superfund program will prepare two HRS packages per year 

due to SsI assessment activities under the proposed rule. Because Option 1 is less likely to identify risks that 

exceed an HRS score of 28.50 (see Exhibit 1-1), the analysis assumes that this option would involve preparation 

 

20 EPA conducted a survey of EPA Regional Superfund Offices in 2011 to support the development of the database of sites with an SsI threat. The survey asked 

EPA Regional Managers to submit information about Draft Vapor Intrusion Site Information Collection Matrix, Jennifer Wendel, National Priorities List 

Coordinator, EPA Region 4.
17

of only one HRS package per year for an SsI site. Similarly, because Option 3 allows consideration of broader 

populations and areas, the analysis assumes that the Superfund program would prepare four HRS packages per 

year for SsI sites under this option. Exhibit 3-1 summarizes the key characteristics of the baseline scenario and 

three regulatory options that affect the cost analysis. 

EXHIBIT 3-1. CHARACTERISTICS OF THE BASELINE SCENARIO AND THREE REGULATORY OPTIONS 

CONSIDERED IN THE COST ANALYSIS

BASELINE OPTIONS 1 OPTION 2 OPTION 3

Non-SsI Sites Assessed per Year 200 180 180 160

SsI Sites Assessed per Year 0 20 20 40 

HRS packages prepared at non-SsI 

sites per year 20 19 18 16

HRS packages prepared at SsI sites 

per year21 0 1 2 4 

Cost per HRS package $65,000

As discussed earlier in this section, for purposes of this analysis, it is assumed that new site assessments of sites 

with SsI threats will replace site assessments at non-SsI sites; therefore, the total number of sites assessed 

annually will remain the same for the baseline scenario and the three regulatory options being considered. The 

number of SsI sites evaluated and the number of HRS packages prepared for SsI threats in each of the three 

regulatory options reflects the methodology considered for evaluating the SsI threat. For example, Option 1 

considered only regularly occupied structures and populations within an area (i.e., area of observed exposure 

(AOE)) delineated by regularly occupied structures with documented contamination resulting from subsurface 

intrusion attributable to the site being evaluated. Option 2 considered regularly occupied structures and 

populations within an AOE and areas outside that of an AOE (i.e., areas of subsurface contamination (ASC)), for 

which subsurface intrusion has been documented at levels significantly above background and the significant 

increase can be attributed, at least in part, to the site being evaluated. Option 3 considered the aforementioned 

AOEs and ASCs, as well as a potential ground water migration zone, which represented an area where ground 

water or soil gas contamination may migrate in the future. The analysis also assumes that the cost of SIs and ESIs 

at SsI sites will be different for each option. These differences are discussed in detail in the following section. 

3.2.3. Methodology for Estimating the Cost of Site Assessments at SsI and non-SsI Sites

The analysis assumes that the proposed rule will result both in additional assessments at sites with potential SsI

threats and in additional costs to incorporate SsI investigation in SIs and ESIs. Because not every assessment at a 

site with a potential SsI threat will necessarily involve an SI or an ESI for SsI (i.e., some sites will not proceed 

beyond a preliminary site assessment), the analysis develops a weighted-average cost per site assessed for each 

regulatory option that accounts for different SI costs. The weighted-average cost per site assessed accounts for the 

costs of the five key activities that can take place during a typical site assessment:

 

21 The number of HRS packages prepared per year at SsI sites equals the number of SsI sites that are estimated to be added to the National Priorities List under 

each regulatory option considered. 
18

1. Preliminary Assessment

2. Site Inspection

3. Integrated Assessment

4. Site Reassessment

5. Expanded Site Inspection 

EPA looked at ICR data and SEMS Accomplishment Reports data to determine the frequencies of site assessment 

activities and average costs per activity.22 The analysis then weighted the cost of each activity by its frequency to 

calculate a weighted-average cost per site assessed. Exhibit 3-2 shows the derivation of the weighted-average cost 

per assessment at a non-SsI site (i.e., the cost of a site assessment in the baseline scenario). 

EXHIBIT 3-2. WEIGHTED AVERAGE COST PER ASSESSMENT AT A NON-SSI SITE

SITE ASSESSMENT ACTIVITY

COST PER 

ACTIVITY1

PERCENT OF SITES 

ASSESSED WITH 

EACH ACTIVITY2

WEIGHTED 

COST3

Preliminary Assessment $14,300 100% $14,300

Site Inspection $45,000 44% $19,700

Integrated Assessment $38,800 4% $1,400

Site Reassessment $20,300 66% $13,400

Expanded Site Inspection $92,300 10% $9,700

Total Weighted Average Site Assessment Cost $58,400

1. Costs per activity are based on data collected in support of ICR 1488.08, provided by 

Randy Hippen, EPA Office of Superfund Remediation and Technology Innovation

(OSRTI), on June 7, 2011.

2. Percent of sites assessed with each activity are based on national SEMS 

Accomplishment Reports data provided by Randy Hippen, EPA OSRTI, on October 30, 

2015. 

3. Individual cost values were calculated using original unrounded input values; each

final value presented in this exhibit was rounded to three significant digits.

To determine how investigating a potential SsI threat would affect the cost of site assessments, EPA developed a 

conceptual site model (CSM) to estimate costs of a site inspection at a typical SsI site.23 For this model, EPA

defined a typical site with an SsI threat. As noted previously, this analysis assumes that investigations for SsI

occur at sites where SsI is the only threat examined. The CSM specifies the following key variables related to SI 

cost:

 

22 Costs per activity are based on data collected in support of ICR 1488.08, provided by Randy Hippen, EPA OSRTI, on June 7, 2011. The percent of sites 

assessed with each activity are based on SEMS Accomplishment Reports data provided by Randy Hippen, EPA OSRTI, on October 30, 2015. The EPA Superfund 

program is in the final stages of replacing the Comprehensive Environmental Response Compensation and Liability Act Information System data management 

system for Superfund site information, with SEMS.

23 For purposes this model, EPA defined a site inspection to encompass both SIs and ESIs.
19

1. Duration of the SI (4 days), 

2. Number of new ground water monitoring wells installed and the number of ground water samples 

collected from new and existing wells (6 wells installed, 10 ground water samples collected); 

3. Number of soil gas samples taken (12 samples); 

4. Number of sub-slab vapor samples taken (32 samples); 

5. Number of indoor air samples taken (32 samples); and

6. Laboratory methods used to analyze and validate ground water and vapor samples (10 ground water 

samples and 76 vapor samples analyzed and validated).

EPA collected unit costs from EPA Regional Offices, the Army Corps of Engineers and an EPA contractor, Tetra 

Tech EM, Inc. to populate the model, using the median cost from the different sources as a best-estimate value 

and the maximum cost as the high-end value.24 For the base case CSM, the value used for the best-estimate 

scenario is $95,700 and the value used for the high-end scenario is $145,000. In addition, the analysis makes the 

following modifications to the CSM to model differences in SI costs for the three regulatory options: 

• Option 1: Option 1 uses the values from the base case CSM.

• Option 2: Option 2 modifies the CSM to include 12 additional ground water and 12 additional soil gas 

samples to characterize the extent of the ASC.

• Option 3: Option 3 modifies the CSM to include 12 additional ground water and 12 additional soil gas 

samples, as in Option 2, as well as additional analysis and reporting effort to identify the target population 

in the Potential Groundwater Migration Zone (PMZ). 

The variations on the CSM used to model costs for each of the regulatory options are summarized in Exhibit 3-4. 

The full methodology used to develop the conceptual site model is discussed in Appendix B. 

The analysis estimates the weighted-average cost of a site assessment at an SsI site by substituting the SI costs 

developed for the conceptual site model for both the cost of an SI and the cost of an ESI.25 Exhibit 3-3 shows the 

derivation of the weighted-average cost per assessment at an SsI site, using the high-end scenario costs for Option 

1 as an example. Exhibit 3-4 summarizes how the analysis estimates the cost of site assessments at SsI sites for 

each of the regulatory options. 

 

24 When estimating median and maximum cost values, the analysis first excludes unit costs considered to be outliers from certain SI tasks, particularly 

planning, staging, oversight and reporting tasks. A complete discussion of the analysis’ treatment of outliers is presented in Appendix B. Refer to Appendix D 

for costs associated with vapor intrusion site inspection tasks.

25 The site investigation activities specified in the CSM correspond most closely to an expanded site inspection (ESI). The RIA conservatively substitutes 

conceptual site model costs for both SI and ESI activities at SsI sites.
20

EXHIBIT 3-3. WEIGHTED AVERAGE COST PER ASSESSMENT AT AN SSI SITE, HIGH-END SCENARIO COSTS 

FOR OPTION 1

SITE ASSESSMENT ACTIVITY

COST PER 

ACTIVITY1

PERCENT OF SITES 

ASSESSED WITH 

EACH ACTIVITY3

WEIGHTED 

COST4

Preliminary Assessment $14,300 100% $14,300

Site Inspection $145,0002 44% $63,100

Integrated Assessment $38,800 4% $1,400

Site Reassessment $20,300 66% $13,400

Expanded Site Inspection $145,0002 10% $15,300

Total Weighted Average Site Assessment Cost $107,000

1. Costs per activity are based on data collected in support of ICR 1488.08, provided by 

Randy Hippen, EPA OSRTI, on June 7, 2011.

2. See Exhibit D-1 for costs associated with an SI/ESI.

3. Percent of sites assessed with each activity are based on SEMS Accomplishment 

Reports data provided by Randy Hippen, EPA OSRTI, on October 30, 2015. 

4. Individual cost values were calculated using original unrounded input values; each

final value presented in this exhibit was rounded to three significant digits.

EXHIBIT 3-4. SUMMARY OF SITE ASSESSMENT COSTS AT SSI SITES 26

OPTION 1 OPTION 2 OPTION 3

Conceptual Site Model Characteristics

Dwellings sampled for sub-slab and indoor air 

quality 32 32 32

Soil gas samples taken 12 24 24

Ground water samples taken 10 22 22 

Effort to identify the Potential Ground Water 

Migration Zone Not included Not included Included

Cost per SI/ESI

High-End Scenario $145,000 $182,000 $189,000

Best-Estimate Scenario $95,700 $120,000 $127,000

Weighted Average Cost per Site Assessed

High-End Scenario $107,000 $128,000 $132,000

Best-Estimate Scenario $80,900 $94,000 $97,800

Note: Option 2 and 3 costs include analysis and validation costs for the additional 12 soil gas and 12 ground water 

samples.

 

26 Refer to Appendix D for costs with vapor intrusion site inspections.
21

3.3. Cost Estimates

Exhibit 3-5 presents the key unit values used by the analysis to estimate the total costs of the proposed rule under 

the three regulatory options considered in this RIA. 

EXHIBIT 3-5. UNIT VALUES USED TO ESTIMATE COST IMPACTS OF THE PROPOSED RULE 27

BASELINE OPTION 1 OPTION 2 OPTION 3

Sites Assessed per Year

Non-SsI Sites 200 180 180 160

SsI Sites 0 20 20 40

Total Sites 200 200 200 200

HRS Packages per Year

Non-SsI Sites 20 19 18 16 

SsI Sites 0 1 2 4 

Total Packages 20 20 20 20

Average Cost per Non-SsI Site Assessed $58,400 $58,400 $58,400 $58,400

Average Cost per SsI Site Assessed

High End n/a $107,000 $128,000 $132,000

Best Estimate n/a $80,900 $94,000 $97,800

Average Cost per HRS Package $65,000 $65,000 $65,000 $65,000

Using the unit values presented in Exhibit 3-5, the analysis estimates high-end and best-estimate cost impacts for 

each regulatory option. These cost estimates are presented in Exhibits 3-6 and 3-7, respectively. Because all costs 

estimated in this chapter are annually occurring costs, no discount rates are used to estimate the present value of 

costs. Annual costs are constant regardless of the discount rates assumed.

 

27 Ibid. 
22

EXHIBIT 3-6. ESTIMATED ANNUAL COST IMPACTS OF THE PROPOSED RULE (HIGH-END SCENARIO, 2011$)* 

BASELINE

SCENARIO OPTION 1 OPTION 2 (PREFERRED OPTION) OPTION 3

NON-SSI 

SITES

NON-SSI 

SITES SSI SITES TOTAL

NON-SSI 

SITES SSI SITES TOTAL

NON-SSI 

SITES SSI SITES TOTAL

Total Sites Assessed 200 180 20 200 180 20 200 160 40 200

Average Cost per

Assessment $58,400 $58,400 $107,000 n/a $58,400 $128,000 n/a $58,400 $132,000 n/a

Total Assessment Costs $11,700,000 $10,500,000 $2,150,000 $12,700,000 $10,500,000 $2,550,000 $13,100,000 $9,350,000 $5,270,000 $14,600,000

Total HRS Packages 20 19 1 20 18 2 20 16 4 20

Average Cost per HRS 

Package $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000

Total HRS Package Costs $1,300,000 $1,230,000 $65,000 $1,300,000 $1,170,000 $130,000 $1,300,000 $1,040,000 $260,000 $1,300,000

Total Costs $13,000,000 $11,800,000 $2,210,000 $14,000,000 $11,700,000 $2,680,000 $14,400,000 $10,400,000 $5,530,000 $15,900,000

Total Costs Attributed to 

Proposed Rule $979,000 $1,380,000 $2,930,000

* Individual cost values were calculated using original unrounded input values; each final value presented in this exhibit was rounded to 

three significant digits.
23

EXHIBIT 3-7. ESTIMATED ANNUAL COST IMPACTS OF THE PROPOSED RULE (BEST-ESTIMATE SCENARIO, 2011$)* 

BASELINE

SCENARIO OPTION 1 OPTION 2 (PREFERRED OPTION) OPTION 3

NON-SSI 

SITES

NON-SSI 

SITES SSI SITES TOTAL

NON-SSI 

SITES SSI SITES TOTAL

NON-SSI 

SITES SSI SITES TOTAL

Total Sites Assessed 200 180 20 200 180 20 200 160 40 200

Average Cost per

Assessment $58,400 $58,400 $80,900 n/a $58,400 $94,000 n/a $58,400 $97,800 n/a

Total Assessment Costs $11,700,000 $10,500,000 $1,620,000 $12,100,000 $10,500,000 $1,880,000 $12,400,000 $9,350,000 $3,910,000 $13,300,000

Total HRS Packages 20 19 1 20 18 2 20 16 4 20

Average Cost per HRS 

Package $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000 $65,000

Total HRS Package Costs $1,300,000 $1,230,000 $65,000 $1,300,000 $1,170,000 $130,000 $1,300,000 $1,040,000 $260,000 $1,300,000

Total Costs $13,000,000 $11,800,000 $1,680,000 $13,400,000 $11,700,000 $2,010,000 $13,700,000 $10,400,000 $4,170,000 $14,600,000

Total Costs Attributed to 

Proposed Rule $450,000 $712,000 $1,580,000

* Individual cost values were calculated using original unrounded input values; each final value presented in this exhibit was rounded to 

three significant digits.
24

3.4. Summary of Costs

Employing several conservative assumptions about the number of site assessments conducted and HRS packages

prepared at SsI sites, as well as the high end of the range of estimated costs of an SsI investigation, the RIA 

estimates that the cost impact of the proposed rule will be approximately $1.0 million for Option 1, $1.4 million 

for Option 2 and $2.9 million for Option 3. Using the median costs of an SsI investigation from the CSM, the RIA 

estimates that the costs of the proposed action will be approximately $0.5 million for Option 1, $0.7 million for 

Option 2 and $1.6 million for Option 3. These costs are summarized in Exhibit 3-8. 

EXHIBIT 3-8. SUMMARY OF ANNUAL COST ESTIMATES FOR THE PROPOSED RULE (2011$)

REGULATORY OPTION

HIGH-END COSTS

(MILLIONS)

BEST-ESTIMATE COSTS

(MILLIONS)

Option 1 $1.0 $0.5 

Option 2 (Preferred Option) $1.4 $0.7

Option 3 $2.9 $1.6 

3.5. Benefits

As noted in the introduction to this chapter, the RIA does not provide a quantitative estimate of benefits. Benefits 

of the rule are expected to be minimal, because the rule will not directly require actions that reduce risks. Any risk 

reduction that may result from the proposed action would come from future site-specific regulatory actions.

As stated in Chapter 1, the proposed action only affects EPA’s ability to evaluate sites with actual or potential SsI

threats for placement on the NPL if warranted; NPL listing informs the public that the site warrants further 

investigation and possibly response actions contingent on the results of future investigation. Benefits of the 

proposed action include improved quality of information and more effective prioritization of remedial efforts by 

the Superfund program through a more comprehensive characterization of sites with SsI threats. 

Specifically, the proposed rule could improve the decision-making of the Superfund program in three distinct 

ways: 

1. For sites not yet on the NPL (but where SsI-related contamination may be a concern), the proposed 

rule would facilitate a more proactive and consistent SsI evaluation as part of the site assessment process, 

including application of the HRS, where necessary, to identify and prioritize sites posing the most 

immediate and serious potential threats to human health and the environment. 

2. For sites already placed on the NPL (scored by another pathway), an early evaluation of potential SsI 

threats, including collection of SsI-related data, during the site assessment process would allow for a more 

careful consideration of such threats as part of the remedial investigation. As a result, these threats could 

be more quickly and comprehensively addressed (i.e., through source/soil control, ground water cleanup 

and/or SsI mitigation) than is currently the case.

3. For all sites with potential SsI contamination, the development of site information about SsI could 

facilitate coordination between EPA and state and Federal agencies with authority related to site 

remediation, leading to more effective and integrated cleanup approaches.
25

In addition, it is possible—in situations where early SsI investigation uncovers a significant threat—that the 

proposed rule could facilitate immediate removal actions. The RIA does not attempt to estimate the likelihood of 

such impacts, however. Generally, the proposed action will not directly impact response actions that may occur at 

sites identified to pose a threat due to SsI. Accordingly, the proposed action is not expected to affect risk and will 

therefore not yield direct benefits to human health. Additionally, Option 2 has been selected as the preferred 

option as it is consistent with the 1990 HRS, serves as an effective screening tool that would both minimize 

unnecessary resource expenditures and the erroneous inclusion or exclusion of sites from possible placement on 

the NPL, and is based on proven science. 

3.6. Caveats and Limitations

Due to limitations in data availability and the uncertainties inherent in trying to predict future site assessment 

activities, the analysis makes several simplifying assumptions in order to develop a reasonable estimate of the 

impacts of the proposed rulemaking. Where possible, the analysis has chosen conservative assumptions in order to 

avoid underestimating costs. Examples of such assumptions include: 

• The analysis assumes that site assessments for SsI contamination would replace baseline activities that 

currently take place. The analysis does not consider the likelihood that some SsI site investigations might

take place in conjunction with investigation of other pathways, and would therefore likely have lower unit 

costs.

• The analysis does not consider the possibility that site assessments for SsI threats could reduce costs by 

eliminating the need to investigate one or more other pathways, such as ground water migration or soil 

exposure. 

• To account for the range of cost estimates provided by EPA Regional Offices, the Army Corps of 

Engineers and contractors for the costs of investigating SsI threats, the analysis estimates cost impacts 

using both the median CSM costs (in the best-estimate scenario) and the maximum CSM costs, excluding 

outliers (in the high-end scenario). The analysis therefore does not consider the possibility that future 

costs to investigate SsI threats could be less than the median CSM costs, particularly if investigation 

methods improve or greater economies of scale are realized when investigating a larger number of SsI

sites.

The use of such conservative assumptions in the analysis makes it possible that the analysis overestimates likely 

cost impacts of the proposed rule.
26

4. Distributional Impacts and Considerations

As required by applicable statutes and executive orders, this chapter summarizes the U.S. Environmental 

Protection Agency’s (EPA) analysis of equity considerations and other regulatory concerns associated with the 

proposed rule. Regarding distributive impacts, transfer payments do not apply to this proposed addition, as the 

costs related to implementation of this proposed addition are already considered in the cost evaluation (see 

sections 3.2 through 3.5 of this document). This chapter assesses potential impacts with respect to the following 

issues: 

• Executive Order 12866 – Regulatory Planning and Review, and Executive Order 13563 – Improving 

Regulation and Regulatory Review; 

• Executive Order 12580 – Superfund Implementation; 

• Executive Order 12898 – Environmental Justice;

• Executive Order 13045 – Protection of Children from Environmental Health Risks and Safety Risks;

• Executive Order 13132 – Federalism; 

• Executive Order 13175 – Consultation and Coordination With Indian Tribal Governments;

• Executive Order 13211 – Actions that Significantly Affect Energy Supply, Distribution, or Usage; 

• Paperwork Reduction Act; 

• Regulatory Flexibility Act; 

• Unfunded Mandates Reform Act; and 

• National Technology Transfer and Advancement Act. 

4.1. Executive Order 12866 – Regulatory Planning and Review, and Executive Order 13563 – 

Improving Regulation and Regulatory Review 

Under Executive Order (EO) 12866 the agency must determine whether a regulatory action is “significant” and 

therefore subject to Office of Management and Budget (OMB) review and the requirements of the Executive 

Order. The Order defines “significant regulatory action” as one that is likely to result in a rule that may: (1) Have 

an annual effect on the economy of $100 million or more or adversely affect in a material way the economy, a 

sector of the economy, productivity, competition, jobs, the environment, public health or safety, or State, local, or 

tribal governments or communities; (2) create a serious inconsistency or otherwise interfere with an action taken 

or planned by another agency; (3) materially alter the budgetary impact of entitlements, grants, user fees, or loan 

programs or the rights and obligations of recipients thereof; or (4) raise novel legal or policy issues arising out of 

legal mandates, the President’s priorities, or the principles set forth in the Executive Order. 

This Regulatory Impact Analysis (RIA) is designed to meet the requirements under Executive Order 12866. The 

cost analysis (Chapter 3) concludes the following:

1. The total annual costs of the proposed rulemaking are under $3 million in all regulatory scenarios, and 

will not have an annual effect on the economy of $100 million or more. In addition, because the proposed 

rule represents only a revision to EPA’s current site assessment activities and does affect any specific 

sector of the economy, it will not have a significant impact on productivity, competition, jobs, or State, 
27

local, or tribal governments or communities. As identified in Chapter 3, the proposed rule does not have 

any significant impacts on human health risk, the environment, or public health or safety.

2. The proposed rule is consistent with EPA’s current authority under section 105 of the Comprehensive 

Environmental Response, Compensation, and Liability Act (CERCLA), and does not alter the authority or 

affect actions taken or planned by another agency. No other regulatory programs comprehensively or 

consistently address remediation of the source of the threat posed by SsI contamination when it is the key 

exposure route. 

3. The proposed rule affects only EPA’s site assessment actions, and will not have a material impact on any

entitlements, grants, user fees, or loan programs or the rights and obligations of recipients thereof; and

4. The proposed rule represents a revision to one existing pathway in the existing Hazard Ranking System

(HRS), and is consistent with EPA’s current authority under section 105 of CERCLA. EPA has 

determined that this proposed rulemaking is a "significant regulatory action.” This proposed rule may 

raise novel legal or policy issues arising out of legal mandates, the President’s priorities, or the principles 

set forth in the EO. Accordingly, EPA submitted this action to the OMB for review under Executive 

Order 12866. 

Executive Order 13563 is supplemental to Executive Order 12866, and it reaffirms the principles of that order and 

requirements that agencies conduct a careful assessment of regulatory costs, benefits and other impacts. Executive 

Order 13563 also requires that EPA: 1) develop a regulatory adoption process that encourages public 

participation; 2) ensure that regulatory requirements do not place an inconsistent or overlapping burden on 

specific industries or sectors; 3) where feasible, consistent with regulatory objectives, and to the extent permitted 

by law, consider regulatory approaches that reduce burdens and maintain flexibility; and 4) ensure the objectivity 

of any scientific and technological information and processes used to support the agency's regulatory action. 

This rulemaking incorporates public comment procedures consistent with existing federal requirements, and does 

not represent an overlapping or inconsistent regulatory burden for any sector. The proposed rule is flexible in its 

application in that EPA has flexibility in developing effective approaches to site assessments at sites with 

potential SsI contamination. Finally, EPA has used objective and updated scientific and technological information 

in the development of this rulemaking.28

4.2. Executive Order 12580 – Superfund Implementation

Executive Order 12580, Section 1(d), states, “Revisions to the National Contingency Plan (NCP) shall be made in 

consultation with members of the National Response Team (NRT) prior to publication for notice and comment. 

Revisions shall also be made in consultation with the Director of the Federal Emergency Management Agency 

and the Nuclear Regulatory Commission in order to avoid inconsistent or duplicative requirements in the 

emergency planning responsibilities of those agencies.” Executive Order 12580 delegates responsibility for 

revision of the NCP to EPA. 

The agency has complied with Executive Order 12580 by consulting with the NRT concerning the proposed 

addition of a new component to the HRS. 

 

28 U.S. Environmental Protection Agency. Detailed Analytic Blueprint for HRS Addition of Vapor Intrusion: Tier 2 Action. July 21, 2011.
28

4.3. Executive Order 12898 – Environmental Justice 

Under Executive Order 12898, as well as through EPA's April 1995 Environmental Justice Strategy, the Office of 

Solid Waste and Emergency Response (OSWER) Environmental Justice Task Force Action Agency Report and 

National Environmental Justice Advisory Council, EPA has undertaken to incorporate environmental justice into 

its policies and programs.29 EPA is committed to addressing environmental justice concerns, and is assuming a 

leadership role in environmental justice initiatives to enhance environmental quality for all residents of the U.S.

The agency's goals are to ensure that no segment of the population, regardless of race, color, national origin, or 

income, bears disproportionately high and adverse human health and environmental effects as a result of EPA's 

policies, programs and activities.

As discussed in Chapter 3, the proposed rulemaking is expected to have only moderate costs and no impact on 

human health risk. Therefore, the rule has no impacts on communities considered under Executive Order 12898. 

Accordingly, EPA did not conduct a complete environmental justice analysis. 

EPA did consider whether the proposed action might have contingent impacts on minority or low-income 

populations located near potential subsurface intrusion (SsI) sites if future actions affect remediation of these 

sites. The contingent demographic analysis summarized below concludes that potentially affected sites are located 

in areas that have slightly higher concentrations of minority populations and populations below the poverty line 

than surrounding areas. Therefore, any future actions addressing risks in these communities would not contribute 

to disproportionate adverse impacts on human health. However, because SsI sites have the potential to pose a high 

level of risk to residents and occupants of other buildings in their vicinity, EPA expects that there will be a 

realignment and reprioritization of its internal resources to address SsI sites. EPA is not able to predict the 

location of the sites without SsI contamination or demographic characteristics of populations living nearby. 

This demographic analysis is summarized below and presented in Appendix C. 

4.3.1. Examination of Potential Contingent Demographic Impacts

Under Executive Order 12898, as well as through EPA’s April 1995 Environmental Justice Strategy, OSWER 

Environmental Justice Task Force Action Agency Report and National Environmental Justice Advisory Council, 

EPA has undertaken to incorporate environmental justice into its policies and programs. Specifically, Executive 

Order 12898 requires that EPA determine whether an action would have a disproportionate impact on low-income 

or minority populations.30

The proposed rulemaking does not have a specific impact on site remediation, and therefore has no impacts on 

risk that would be relevant under Executive Order 12898. Any potential changes to human health risk resulting 

from the proposed action will be contingent on additional site-specific rulemakings. To ensure comprehensive 

consideration of the possibility of impacts related to environmental justice, EPA considered the possibility that 

sites that are identified as having SsI contamination under the rule could potentially be located in areas 

 

29 See U.S. Environmental Protection Agency, Draft Technical Guidance for Assessing Environmental Justice in Regulatory Analysis (2013). 

30 Executive Order 12898, “Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations”, February 11, 1994. In 

addition, EPA is currently developing technical guidance to support this executive order, to provide detailed information on incorporating environmental 

justice into risk assessments, economic analyses and other scientific input and analytical documents as part of the agency’s rulemaking process. EPA is 

committed to addressing environmental justice concerns, and is assuming a leadership role in environmental justice initiatives to enhance environmental 

quality for all residents of the U.S. The agency's goals are to ensure that no segment of the population, regardless of race, color, national origin, or income, 

bears disproportionately high and adverse human health and environmental effects as a result of EPA's policies, programs and activities. 
29

characterized by populations with high concentrations of low-income or minority residents. This analysis 

examines demographic characteristics of populations living within 1 and 3 miles of sites identified in EPA’s list 

of potentially affected non-National Priorities List (NPL) sites (discussed in Chapter 2).

31 The demographic 

analysis indicates that areas around potentially affected sites have statistically higher concentrations of minority 

populations and populations below the poverty line than surrounding areas. 

 

4.3.2. Methodology 

The analysis relies on U.S. 2000 Census data for census block groups and counties, and on site location data 

available in CERCLIS (EPA’s Comprehensive Environmental Response, Compensation, and Liability 

Information System), to identify the percent of the population near each site defined as minority and the percent 

of the population below the poverty line.32 The analysis first calculates the proportion of the populations near each 

site that are minority or low-income, and then compares those populations with the population of the surrounding 

county for each site. Rather than comparing demographic characteristics of the areas surrounding each site to 

national averages, EPA determined that county-level statistics provide an appropriate scale for comparison to oneand three-mile buffers.33 

The demographic analysis examines populations within one and three miles of 240 of the approximately 1,073 

sites potentially affected by the proposed rule.34 While this group of sites does not represent a representative 

sample of all sites, the analysis includes 240 sites distributed geographically across all EPA Regions. All sites are 

equally weighted. 

For the areas within one- and three-mile radii of the selected sites, the analysis calculates the mean and median 

values for the minority share of the population and percent of the population below the poverty line. The analysis 

then applies a student’s paired, two-tailed t-test to determine whether these values are statistically different from 

the demographic characteristics of the counties surrounding the selected sites. A statistically significant positive 

difference indicates that a greater percentage of the target demographic (i.e., minorities or people living below the 

poverty line) exists in the affected population than in the larger reference population. A statistically significant 

negative difference indicates a smaller percentage of the target demographic in the affected population. 

4.3.3. Results

Exhibit 4-1 summarizes the demographic characteristics of the areas surrounding the selected sites. Overall, both 

minority and poverty demographics constitute a slightly larger proportion of the populations surrounding sites 

with potential SsI threats than the proportion of those demographics in the surrounding counties. For example, 

poor populations account for 15.4 percent of the population within 1 mile of the average site with potential SsI

 

31 See Appendix C for the complete demographic screening analysis, including a population-weighed estimate that more heavily weights sites with higher 

populations. Due to uncertainty about the location of actual sites, however, we discuss only the unweighted results here.

32 Minority data includes non-white non-Hispanics and both white and non-white Hispanics; poverty line refers to the 1999 Federal poverty line.

33 The analysis compared the demographic characteristics of the counties surrounding potentially affected sites to national averages to determine whether the 

selected counties had a higher proportion of low-income or minority populations, relative to the country as a whole. The analysis found that the selected 

counties had lower proportions of both low-income and minority populations than national averages but that these differences were not statistically 

significant. 

34 The demographic analysis considered only sites potentially affected by the proposed rule where the exact location of the site could be identified.
30

threats, while the county has a poverty level of 12.3 percent. Exhibit 4-2 provides the results of the statistical 

analysis of the differences between the one- and three-mile buffer populations and the county population. The 

exhibit shows that the differences within both one and three miles of the sites with potential SsI contamination are

statistically significant, as indicated by the p values. For the population within the one-mile buffer, the difference 

in percent minority population and percent below poverty level with respect to the reference population are 

significant at the 99 percent certainty level. For the population within the three-mile buffer, the difference in 

percent minority population is statistically significant at the 95 percent certainty level and the difference in 

percent below poverty level is significant at the 99 percent certainty. This suggests that the difference between the 

values is not a random occurrence. 

EXHIBIT 4-1. DEMOGRAPHIC CHARACTERISTICS OF THE POPULATIONS SURROUNDING SITES POTENTIALLY 

AFFECTED BY THE PROPOSED RULE

1 MILE 3 MILE COUNTY

MEAN MEDIAN MEAN MEDIAN MEAN MEDIAN

Percent Minority Population 32.3% 25.0% 30.8% 25.9% 28.7% 24.4%

Percent Below Poverty 

Level 15.4% 12.7% 14.2% 12.6% 12.3% 11.1%

EXHIBIT 4-2. STATISTICAL ANALYSIS COMPARING DEMOGRAPHIC CHARACTERISTICS OF 1- AND 3-MILE 

BUFFERS AROUND SELECTED SITES TO DEMOGRAPHIC CHARACTERISTICS OF SURROUNDING COUNTIES

DIFFERENCE BETWEEN SITE CHARACTERISTICS AND COUNTY CHARACTERISTICS

1-MILE BUFFER 3-MILE BUFFER

MEAN

STANDARD 

ERROR OF 

MEAN

TSTATISTIC P-VALUE MEAN

STANDARD 

ERROR OF 

MEAN

TSTATISTIC P-VALUE

Percent Minority Population 0.0366 0.0133 2.75 0.0064 0.0217 0.0103 2.11 0.036

Percent Below Poverty Level 0.0308 0.0063 4.93 <0.001 0.0188 0.0043 4.38 <0.001 

Overall, the demographic analysis identifies a small but statistically significant difference between the proportion 

of the population that is minority and the proportion of the population in poverty near sites with potential SsI

contamination and in the larger county-level populations. This result implies that any remediation at sites 

associated with SsI contamination would occur in the context of disproportionately high minority and low-income 

populations located near Superfund sites with potential SsI threats. Because any contingent impacts of the 

proposed rule would involve risk reduction at these sites, EPA does not anticipate that contingent impacts would 

have any disproportionately high and adverse human health or environmental effects on these minority or lowincome communities, or on any community. However, because SsI sites have the potential to pose a high level of 

risk to residents and occupants of other buildings in their vicinity, EPA expects that there will be a realignment 

and reprioritization of its internal resources to address SsI sites instead of sites without SsI contamination. EPA is 
31

not able to predict the location of the sites without SsI contamination or demographic characteristics of 

populations living nearby. 

This section summarizes a screening assessment and does not present a complete environmental justice 

analysis.The assessment is limited by the fact that demographic data from the U.S. Census are at the block group 

level, and are not as precise as the spatial distribution of population. As a result, if the demographic distribution of 

populations within block groups is uneven, the block group-level data may not accurately characterize populations 

living nearest to sites with potential SsI threats.

In an effort to determine if updated U.S. Census data would identify a reduction in the proportion of the 

population that is minority or below the poverty level near sites with potential SsI contamination, the results 

discussed above based on 2000 U.S. Census data were compared with 2009-2013 American Community Survey 

(ACS) data. 

EXHIBIT 4-3. DEMOGRAPHIC CHARACTERISTICS OF THE POPULATIONS SURROUNDING SITES POTENTIALLY 

AFFECTED BY THE PROPOSED RULE 

1 MILE 3 MILE

MEAN

(2000 U.S. 

CENSUS)

MEAN

(2009-2013 ACS) 

MEAN

(2000 U.S. 

CENSUS)

MEAN

(2009-2013 ACS)

Percent Minority Population 41.1% 46.1% 41.8% 47.7% 

Percent Below Poverty Level 16.8% 18.8% 14.8% 16.4% 

As was done for the analysis using 2000 U.S. Census data, the analysis first calculated the proportion of the 

populations near each site (based on the one-mile and three-mile buffers) that are minority or below the poverty 

level, and then compares those proportions. These proportions were then compared to the weighted mean results 

from the 2000 analysis. Exhibit 4-3 illustrates that the proportion of the population that is minority or below the 

poverty level near sites with potential SsI threats did not decrease. Therefore, these results continue to indicate 

that there would not be any expected disproportionately high or adverse human health or environmental impacts 

on these minority or low-income communities. 

4.4. Executive Order 13045 – Protection of Children from Environmental Health Risks & Safety Risks

Executive Order 13045 requires that EPA consider whether the proposed rulemaking could result in a 

disproportionate negative impact on children’s health. As discussed in Chapter 3, the proposed rulemaking is 

expected to have only moderate costs and no direct impact on human health risk. In addition, any impacts 

resulting from future actions to remediate sites with SsI contamination would reduce the human health risk at 

these sites. As a result, EPA concludes that this rule will have no significant impacts on children’s health. 
32

4.5. Executive Order 13132 – Federalism 

This action does not have federalism implications. It will not have substantial direct effects on the states, on the 

relationship between the national government and the states, or on the distribution of power and responsibilities 

among the various levels of government, as specified in Executive Order 13132, because it does not contain any 

requirements applicable to states or other levels of government. Thus, Executive Order 13132 does not apply to 

this action. 

In the spirit of Executive Order 13132 and consistent with EPA policy to promote communications between EPA

and state and local governments, EPA specifically solicits comment on this proposed action from state and local 

officials.

4.6. Executive Order 13175 – Consultation and Coordination With Indian Tribal Governments

This executive order requires EPA to “establish regular and meaningful consultation and collaboration with tribal 

officials in the development of Federal policies that have tribal implications.” The executive order further states 

that “policies that have tribal implications” refers to regulations; legislative comments or proposed legislation; 

and other policy statements or actions that have substantial effects on one or more Indian tribes, on the 

relationship between the Federal Government and Indian tribes, or on the distribution of power and 

responsibilities between the Federal Government and Indian tribes. 

This proposed rule does not contain any requirements applicable to tribal governments and will not have a 

substantial effect on any tribes. Thus, the requirements of the executive order do not apply to this rulemaking. In

addition, any contingent impacts related to later listing and remediation decisions would include all community 

outreach stipulated under CERCLA and existing EPA policy to ensure collaboration with tribal officials for any 

sites on tribal land. Although Executive Order 13175 does not apply to this action, EPA consulted with tribal 

officials through meetings; correspondence, including a letter sent to all federally recognized tribes asking for 

comment on the “Notice of Opportunity for Public Input” that was published in the Federal Register on January

31, 2011 (see 76 FR 5370); and public listening sessions regarding the decision to proceed with the development 

of this action. 

4.7. Executive Order 13211 – Actions that Significantly Affect Energy Supply, Distribution, or Usage 

This EO requires federal agencies to prepare a “Statement of Energy Effects” when undertaking certain regulatory 

actions. A Statement of Energy Effects describes the adverse effects of a “significant energy action” on energy 

supply, distribution and use, reasonable alternatives to the action, and the expected effects of the alternatives on

energy supply, distribution and use. 

This rulemaking is not a “significant energy action.” It is not likely to have any adverse energy impacts because 

the site assessment activities affected by this rule are limited in scope and number and rely on existing energy 

distribution systems. The proposed rule would not significantly expand the energy demand for site assessments, 

and would not require an entity to conduct any action that would require significant energy use. The proposed rule 

would have no impact on energy supply, distribution or usage. 
33

4.8. Paperwork Reduction Act

According to the Paperwork Reduction Act (PRA), 44 U.S.C. 3501 et seq., an agency may not conduct or 

sponsor, and a person is not required to respond to a collection of information that requires OMB approval under 

the PRA, unless it has been approved by OMB and displays a currently valid OMB control number. 

This proposed regulatory change will only affect how EPA, and organizations performing work on behalf of EPA

(state or tribal partners), conducts site assessments and HRS scoring at sites where certain environmental 

conditions exist. These conditions involve human exposure from subsurface intrusion of hazardous substances 

that enter building structures through the subsurface environment either as a vapor or liquid. This proposed 

regulatory change will result in data collection at these types of sites in order to allow evaluation under the HRS. 

EPA expects that the total number of site assessments performed and number of sites added to the NPL will not 

increase, but rather expects that there will be a realignment and reprioritization of its internal resources and state 

cooperative agreement funding. This is because SsI sites have the potential to pose a higher level of risk than 

other exposure routes, and thus, will allow the agency to evaluate sites with SsI contamination for potential 

placement on the NPL. The burden for collecting data under the HRS, which includes performance of site 

assessments, is already covered under the Information Collection Request (ICR) for Superfund Site Evaluation 

and Hazard Ranking System; EPA ICR No. 1488.08, OMB Control No. 2050-0095, Docket # EPA-HQ-SFUND2011-0052. The information collection requirements are contained in the statute at CERCLA Section 

105(a)(8)(A) under the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and, as mentioned 

above, has the assigned OMB control number 2050-0095. The OMB control numbers for EPA's regulations in 

Title 40 of the Code of Federal Regulations (CFR) are listed in 40 CFR 9. Because this proposed rulemaking only 

involves adding an additional component (i.e., SsI) to an existing HRS pathway, a new ICR is not needed. 

Therefore, the agency does not believe this action will impose any new information collection burden, as the term 

"burden" is defined at 5 CFR 1320.3(b). 

4.9. Regulatory Flexibility Act

Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., as amended by the Small Business Regulatory 

Enforcement Fairness Act of 1996), whenever an agency is required to publish a notice of rulemaking for any 

proposed or final rule, it must prepare and make available for public comment a regulatory flexibility analysis that 

describes the effect of the rule on small entities (i.e., small businesses, small organizations and small 

governmental jurisdictions).

This rulemaking does not impose any obligations on any group, including small entities. This proposed regulatory 

change enables the HRS evaluation to directly consider human exposure to hazardous substances that enter 

building structures through subsurface intrusion. The HRS is a screening tool that does not impose regulatory 

requirements on any non-governmental entity. It does not establish any standards or requirements that any small 

entity must meet, and it imposes no direct costs on any small entity. Whether an entity, small or otherwise, is 

liable for response costs for a release of hazardous substances depends on whether the entity is liable under 

CERCLA 107 (a)35; therefore, this rulemaking will not impose any further requirements on any small businesses.

 

35 CERCLA section 107(a) establishes the categories of potentially responsible persons (PRPs) that may be found liable for CERCLA related costs. PRPs include 

current or past owners and operators, a person who arranges for disposal or treatment of a hazardous substance, and any person who accepts hazardous 

substances for transport to disposal or treatment facilities. PRPs are liable for removal or remedial response action costs, other necessary costs, natural 

resource damages, and the cost of health studies conducted pursuant to CERCLA section 9604(i).
34

4.10. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 1531-1538 requires federal agencies, 

unless otherwise prohibited by law, to assess the effects of their regulatory actions on state, local, and tribal 

governments and the private sector. Federal agencies must also develop a plan to provide notice to small 

governments that might be significantly or uniquely affected by any regulatory requirements. The plan must 

enable officials of affected small governments to have meaningful and timely input in the development of EPA 

regulatory proposals with significant federal intergovernmental mandates and must inform, educate, and advise 

small governments on compliance with the regulatory requirements. 

The proposed rule contains no federal mandates (under the provisions of Title II of the UMRA) for state, local, or 

tribal governments or the private sector. The action imposes no enforceable duty on any state, local or tribal 

governments or the private sector. Therefore, this action is not subject to the requirements of 202 or 205 of the 

UMRA. This action is also not subject to the requirements of section 203 of UMRA because it contains no 

regulatory requirements that might significantly or uniquely affect small governments. The proposed regulatory 

change will allow the HRS evaluation to directly consider human exposure to hazardous substances that enter 

building structures through subsurface intrusion. This addition to the HRS would not impose direct impacts on 

any other entities. 

4.11. National Technology Transfer and Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995, Public Law 104–113, section 

12(d) (15 U.S.C. 272 note), directs EPA to use voluntary consensus standards in its regulatory activities unless to 

do so would be inconsistent with applicable law or otherwise impractical. 

This rulemaking will not involve technical standards; therefore, EPA will not consider the use of any voluntary 

consensus standards.

 
35

5. Summary of Costs, Benefits and Other Impacts

This chapter documents the comparison of costs and benefits associated with the proposed rule, and addresses 

U.S. Environmental Protection Agency (EPA) and Office of Management and Budget (OMB) requirements that 

regulatory impact analysis consider cost-effectiveness of regulations and alternative discount rates.

5.1. Cost Benefit Comparison

Regulatory impact analyses typically use a formal cost-benefit analysis to assess the impacts of proposed 

rulemakings. Due to the limited scope of the proposed amendment to the regulations at Title 40 of the Code of 

Federal Regulations (CFR) 300.425, the analysis considers only the cost impacts of considering subsurface 

intrusion (SsI) threats in site assessments and does not develop a quantitative estimate of benefits. The results of 

the analysis of the costs and benefits of the proposed rule are summarized in Exhibit 5-1. As the exhibit shows, 

total annual costs of Option 2 (the preferred option) are expected to range from $0.7 million to $1.4 million. Total 

annual costs in all scenarios are less than $4 million. Because the Regulatory Impact Analysis does not 

quantitatively estimate benefits, a formal quantitative comparison of the expected costs and benefits of the 

proposed rule is not possible. However, Option 2 has been selected as the preferred option as it is consistent with 

the 1990 Hazard Ranking System (HRS), serves as an effective screening tool that would both minimize 

unnecessary resource expenditures and the erroneous inclusion or exclusion of sites from possible placement on 

the NPL, and is based on proven science. 

EXHIBIT 5-1. SUMMARY OF COSTS AND BENEFITS (MILLION$)

TYPE OF IMPACT OPTION 1

OPTION 2 

(PREFERRED 

OPTION) OPTION 3

Costs

Annual Costs of Investigating SsI threats and of Preparing HRS Packages for SsI sites (million 2011$)

High-End Scenario $1.0 $1.4 $2.9

Best-Estimate Scenario $0.5 $0.7 $1.6

Benefits

Improved quality of information and more effective prioritization of 

remedial efforts by the Superfund program through a more 

comprehensive characterization of sites with SsI threats.

Not quantifiable

Note: Because cost impacts are expected to be constant on an annual basis over time, presenting the net present value 

of costs would not add analytic value and are not presented here. Therefore, although alternative discount rates of 

seven percent and three percent were not considered, the costs presented in this exhibit satisfy OMB Circular A-4 and 

EPA policy requirements to annualize regulatory impacts using alternative discount rates of seven percent, three percent

and zero percent (undiscounted).
36

5.2. Other Required Analyses

OMB Circular A-4 directs Federal agencies to support rulemakings with cost-effectiveness analysis wherever 

possible and to consider costs and benefits under alternate discount rates of three percent and zero percent (i.e., no 

discounting). 

• Cost-Effectiveness Analysis: Because the expected benefit of the proposed rulemaking is an 

improvement in the overall efficiency of the Superfund program, there is no unit measure of benefit that 

could be used to conduct a cost-effectiveness analysis. 

• Assessment of Costs and Benefits under Alternative Discount Rates: Because cost impacts are 

presented on an annual basis, the analysis does not estimate present value of costs. The costs presented in 

Exhibit 5-1 therefore satisfy OMB Circular A-4 and EPA policy requirements to annualize regulatory 

impacts using alternative discount rates of seven percent, three percent and zero percent (i.e., 

undiscounted). 
A-1 

APPENDIX A: Options Selection Matrix

EXHIBIT A-1. FULL COMPARISON OF OPTIONS CONSIDERED FOR THE PROPOSED RULE 36

OPTIONS FOR SCORING 

POPULATIONS

POTENTIAL 

NUMBER OF 

NPL CALIBER 

INTRUSION 

SITES

PROS/CONS CONSISTENCY WITH 

OTHER HRS PATHWAYS

POPULATIONS NECESSARY TO QUALIFY A SITE FOR THE 

NPL

Option 1 – Consider Only 

Actual and Inferred Exposures

• Includes all actual and

inferred contamination for

regularly occupied

structures within the AOE

• Does not include potential

exposure for regularly

occupied structures outside

the AOE

Less

Pro: Will have a high probability that 

identified releases pose a risk when 

scoring by zones of contamination

Con: Could fail to identify sites 

warranting further investigation

because potential exposures will not 

be considered 

Con: Does not consider future 

conditions/migration and may 

necessitate greater review of sites 

given a “no further action” 

designation 

Option is consistent with:

• The soil exposure

pathway in that it does

not consider potential

targets and infers Level

II contamination

• All pathways in how

Level I and II targets

are weighted

• 23 people actually exposed to contamination above

Health-Based Benchmarks (Level I in the AOE), or

• 10 people actually exposed to contamination above

Health-Based Benchmarks (Level I) and 130 people

actually exposed to or inferred to be exposed to

contamination above background (Level II), or

• 231 people actually exposed to or inferred to be exposed

to contamination above background (Level II in the

AOE)

Assumes a Waste Characteristics value of 32

Option 2 – Consider Actual, 

Inferred and Probable 

Exposures

• Includes those regularly

occupied structures within

the AOE and the ASC

• Includes both actual

contamination intrusion and

probable exposure to

subsurface contamination

for regularly occupied

structures within the AOE

and ASC

Middle

Pro: Would ensure that most releases 

posing a significant risk are identified 

by relying upon lines of evidence

Con: Could lead to an underestimate 

of the number of releases because 

future migration of subsurface 

contamination is not accounted for 

and/or because lines of evidence 

gathered during the Site Assessment 

process may be incomplete 

Con: Does not consider future 

conditions / migration; therefore, may 

necessitate greater review of sites 

given a “no further action “ 

designation

Option is consistent with:

• The soil exposure, air

and surface water

pathways in that there

is inference of

contamination for

Level II targets

• The air pathway in that

“on-source” targets are

included in the scoring

• All pathways in how

Level I and II targets

are weighted

• 23 people exposed to contamination above Health-Based

Benchmarks (Level I in the AOE), or

• 10 people exposed to contamination above Health-Based

Benchmarks (Level I) and 130 people exposed to

contamination above background (Level II), or

• 231 people exposed to contamination above background

(Level II in the AOE), or

• 10 people exposed to contamination above Health-Based

Benchmarks (Level I) and 100 people exposed to

contamination above background (Level II) (in AOE) and

36 people living above subsurface contamination

(Probable Exposure in ASC), or

• 548 people living above subsurface contamination

(Probable Exposure in ASC) assuming a Likelihood of

Exposure of 500

Assumes a Waste Characteristics Value of 32 and a weighting 

of 0.5 for Probable Exposure Populations 

36 The methodologies used to evaluate the waste characteristics and targets factor category values in the proposed HRS addition have been revised since these three options were created to model different scoring 

scenarios. Please see the preamble, rule, and technical support document for the proposed HRS addition for additional information. 
A-2 

Option 3 – Consider Actual, 

Inferred, Probable and 

Potential Exposures 

• Includes regularly occupied

structures within the AOE,

the ASC and the PMZ

• Includes actual

contamination intrusion,

probable and potential

exposure to subsurface

contamination for regularly

occupied structures within

the AOE, ASC and PMZ

• Includes unsampled

structures, but are

considered to be potentially 

exposed

Most

Pro: Would ensure that all releases 

posing a risk are identified 

Con: Could result in identification of 

low risk releases because not all 

identified releases will result in future 

exposure 

Con: Limited rationale for projecting 

extent of potential migration zone

Con: Not assuming migration in all 

directions (i.e., <360 degrees) could 

result in questioning the target 

delineation for ground water and air 

pathways

Option is consistent with:

• The air pathway in that

“on-source” targets are

included in the scoring

• The ground water

pathway in that the

way PMZ targets are

weighted

• All pathways in how

Level I and II targets

are weighted

• 23 people exposed to contamination above Health-Based

Benchmarks (Level I in the AOE), or

• 10 people exposed to contamination above Health-Based

Benchmarks (Level I) and 130 people exposed to

contamination above background (Level II), or

• 231 people exposed to contamination above background

(Level II in the AOE), or

• 10 people exposed to contamination above Health-Based

Benchmarks (Level I) and 100 people exposed to

contamination above background (Level II) (in AOE) and

36 people living above subsurface contamination

(Probable Exposure in ASC), or

• 548 people living above subsurface contamination

(Probable Exposure in ASC) and assuming a Likelihood

of Exposure of 500, or

• 21,962 people living in an area where subsurface

migration could occur (Potentially Exposed People in the

PMZ) and a Likelihood of Exposure of 320

Assumes a Waste Characteristics value of 32, a weighting of 

0.5 for Probable Exposure Populations and 0.02 for 

Potentially Exposed Populations

Definitions of Zones

Area of Observed Exposure (AOE) – An area of observed contamination; the AOE is bounded by regularly occupied structures with documented contamination intrusion 

above background; the AOE includes sampled and unsampled structures, which are assumed to be contaminated, and only actually exposed populations. 23 Represents 

people subject to Level I contaminant concentrations. Represents people subject to Level II contaminant concentrations.

Area of Subsurface Contamination (ASC) – An area with documented contamination significantly above background; the ASC is bounded by sampling points meeting 

observed release criteria for subsurface intrusion (e.g., ground water and soil gas sampling points); the area within the ASC includes both sampled and unsampled 

structures and probable exposure populations; the ASC does not include the AOE. 

Potential Ground Water Migration Zone (PMZ) – An area between the ASC and target distance limit that includes all occupied structures; occupied structures may be 

unsampled, but populations are potentially exposed to intrusion currently or in the future given the proximity to the source and future migration of the ground water or soil 

gas contamination plume; the PMZ does not include the AOE or the ASC.
B-1 

APPENDIX B: Conceptual Site Model Used to Estimate Costs of Screening for Subsurface 

Intrusion Contamination 

This appendix describes the conceptual site model (CSM) used to estimate the costs of the proposed addition of a 

subsurface intrusion (SsI) component to the Hazard Ranking System (HRS). It first presents a discussion of the 

data sources, methods and assumptions used to develop the base case CSM written in support of the proposed 

rulemaking. It then describes adjustments made to the CSM in order to exclude outlier cost estimates and compare 

the costs of the preferred regulatory option and two alternate options. 

SsI Site Inspection Cost Estimate

Introduction

The U.S. Environmental Protection Agency (EPA) is proposing the addition of an SsI component to the HRS. 

Subsurface intrusion is the result of contaminated subsurface soil or ground water plumes releasing contaminants 

into occupied structures, mainly as a gas or vapor. This rulemaking will enable EPA to evaluate sites where SsI 

contamination poses a potentially significant threat to human health using the HRS, thereby fulfilling the agency’s 

obligations to protect human health. 

Determining the costs associated with evaluating SsI threats as part of the site assessment process is necessary in 

order to better understand the financial impacts the proposed rule represents. To this end, EPA prepared a survey 

for the purpose of evaluating the cost of performing a site inspection (SI), including typical sampling/screening 

techniques used for evaluating SsI threats. The survey, which included instructions to develop cost estimates for 

particular SI tasks, was submitted to each of EPA Regions on the HRS/SsI work group, an EPA Regional 

contractor (Tetra Tech Incorporated) and the U.S. Army Corps of Engineers (USACE). 37 

The primary objectives of this survey and subsequent analysis of provided cost estimates were to: (1) estimate the 

unit costs for conducting specific tasks (e.g., installing a sub-slab vapor probe) related to investigating a site for 

potential SsI threats and (2) use unit cost information to estimate the total cost for conducting an SI to evaluate 

SsI. This preliminary cost estimate was developed using cost data provided in response to the survey and was 

based on previous site assessments. Data obtained from the survey should be considered only for estimation 

purposes as investigation costs can vary greatly depending on the scope of work performed, which is a function of 

geographic location, geologic setting, nature/extent of contamination and demographics, along with numerous 

additional factors. It should also be noted that, although the survey requested cost information for performance of 

an SI, such investigations can include a level of effort associated with an expanded site inspection. The cost 

information gathered was used to project the estimated cost of an assessment to evaluate SsI threats using a 

conceptual site model as described in this document. 

 

37 Cost information for conducting an SI of a site with vapor intrusion contamination was requested from the data sources. For the purposes of this analysis, the 

more general term, subsurface intrusion, was used instead of vapor intrusion to refer to the component proposed for addition to the HRS. The costs for a 

vapor intrusion SI would likely be more expensive than that for a typical site with ground water intrusion into structures.
B-2 

Data Sources 

Survey data were received from EPA Regions 3, 5 and 6 and an EPA contractor, Tetra Tech Incorporated (Tetra 

Tech), through Dave Bartenfelder of EPA Headquarters, and a representative of USACE’s Baltimore District. 

Additionally, costs associated with data validation were obtained from several EPA Regions who supplied 

estimates based on validation work performed by an agency contractor. Cost estimates from Tetra Tech and 

USACE were considered primary sources, with estimates from EPA Regions used for purposes of comparison 

and verification when unable to calculate task unit costs from the data provided. Please refer to Appendix D: Costs 

for Vapor Intrusion Site Inspection Tasks Compiled for Regulatory Impact Analysis for additional details.

Throughout this section, cost estimates that appear to be outliers (i.e., that differ substantially from estimates 

provided by other data sources) are highlighted. When applying the CSM to the cost analysis in the Regulatory 

Impact Analysis (RIA), EPA decided on a case-by-case basis whether to exclude these outliers from the total SI 

cost estimate. The full treatment of outliers is discussed below in the section describing how the CSM was 

adjusted for use in the RIA. 

U.S. EPA Regional Cost Data 

EPA Region 3 provided cost summaries that contained unit and/or total costs from three previous site assessments 

for the following tasks: in-house preparation, field sampling and analysis, report preparation, travel and per diem. 

This included discrete costs for materials and labor for probe construction, as well as labor costs for what was 

assumed to be preparation of Summa canisters. The field sampling and analysis costs included unit costs for 

Summa canisters (assumed to be analytical costs), labor costs and shipping costs. Cost data for project planning 

(except for one site where costs for a health and safety plan and a work plan were provided), mobilization fees 

and equipment rental costs were not reported. Quality assurance/quality control costs of $100 per sample listed 

under the “Report” section of the provided cost summaries were assumed to be data validation costs. 

• Data Outlier: This dataset contained a cost estimate of $600/sample for Summa canister analysis, which 

appears to be an outlier. This unit cost resulted in the significantly higher cost of $45,600 to analyze 76 

Summa canister samples (see Exhibit B-6). 

EPA Region 6 provided cost summaries for four previous field investigations that contained total costs for the 

following tasks: planning, equipment rental, field supervision, project management and incidental costs. The data 

for one investigation stated that the total cost of collecting 12 Summa canister samples was included in these 

costs. The total costs for installing exposed screen monitoring wells were provided, but not a breakdown of their 

associated equipment, materials, or labor costs. Costs related to collecting ground water monitoring well samples 

were not provided. Additional costs provided were material and analytical unit costs for passive diffusion 

samplers. Costs relating to data validation activities were not provided and were assumed to be included in 

analytical costs provided. 

 

• Data Outlier: The costs provided for field supervision (range of $20,500-$35,308), project management 

(high cost of $17,600) and incidental costs (high cost of $11,226) are potentially higher compared to those 

of other source estimates, and may include some unrelated costs (see Exhibit B-1). 
B-3 

EPA Region 5 provided more limited information on the total costs of collecting an individual indoor air, ambient 

air, sub-slab and soil gas sample from previous investigations, and did not include any discrete planning, staging, 

oversight or reporting costs. These cost estimates did not break out the individual components for labor, 

equipment and materials used, but the information provided was compared to the more detailed data obtained 

from other sources to verify that costs were similar. 

Data validation cost estimates, which reflected validation work performed by contractors (as opposed to EPA inhouse), were also obtained from representatives at several EPA Regional laboratories. All costs were provided on 

a “per sample” basis, reported separately for differing media (air versus water) and, to the extent practicable, took 

into account whether a streamlined or full-level quality assurance (QA) review was conducted. For the most part, 

unit costs were higher than those estimated by USACE, which assumed streamlined QA review, and Tetra Tech, 

whose QA costs were low even for streamlined review. 

• Data Outlier: The costs provided by EPA Region 1 for a streamlined QA review ($202 per sample) and a 

full QA review ($275 per sample) of water sample data appear to be outliers compared to the information 

received from other EPA Regions. In addition, the data validation costs received from EPA Regions ($39-

$115 per sample for air and $19-$275 per sample for water) are greater than the costs provided by Tetra 

Tech ($10-$17 per sample for air and $10-$15 per sample for water) and USACE (assumed $27.82-$30 

per sample for both air and water). This cost differential results in higher data validation costs when using 

EPA Regional estimates (see Exhibit B-6). 

U.S. EPA Contractor Cost Data (Tetra Tech) 

Cost estimates for all of the tasks listed in this cost survey were received from Tetra Tech. Their estimates were 

based on previous experience and recent bids and quotes. If they received more than one bid for a task, the most 

reasonable bid, based again on their experience, was selected. For the most part, except where noted in the 

following tables, the unit and total costs provided for each task included labor, equipment and material costs (but 

not shipping). Data validation costs for SW-846 method 8260 analysis (water or soil-gas) and for EPA method 

TO-15 analysis (soil-gas or indoor air) were also obtained. The cost estimates were based on an assumed quantity 

of samples and timeframe needed to accomplish a particular task. Certain tasks listed in the Tetra Tech summary 

included a range of unit and/or total costs, which was the result of the assumed number of samples and estimated 

timeframe utilized. 

It was also noted by Tetra Tech that “Target Identification” data requested in the cost survey was covered by the 

pre-sampling building survey task shown in Exhibit B-5. The estimated cost provided for conducting a presampling building survey was $1,000/day in labor costs covering one industrial building or eight residential 

buildings per day. 

 

• Data Outlier: The data included cost estimates for certain tasks that were noted as being highly variable 

and based on such factors as the size/complexity of the site, the seniority and number of crew members, 

the location of the site and the scope/duration of the project. Two tasks in particular, planning and project 

management, had costs showing especially large ranges ($10,000-$100,000 and $10,000-$80,000 

respectively), where the high estimates appear to be an outlier (see Exhibit B-1). The data provided also 

included a separate “Reporting” task that contained a cost range of $10,000 - $100,000 that was not 
B-4 

included in this cost analysis as a line item due to the wide variability in the Tetra Tech costs already 

present. These three outliers also potentially represent costs associated with site investigations that are 

beyond the scope of a typical site inspection for HRS purposes. 

U.S. Army Corps of Engineers Cost Data 

The data provided by the USACE included unit and total costs for all tasks listed in this cost analysis and were 

based on previous experience, future projects and internet research for a “typical number of sites.” The estimated 

unit costs typically included the relevant equipment, material and labor cost components for each task listed in 

this analysis. Unlike in the data provided by Tetra Tech and EPA Region 3, the only cost associated with 

collecting a Summa canister sample was the labor to set up, collect and ship (shipping costs were included in 

incidental costs) the resulting samples. The material and preparation costs for Summa canisters were included in 

the analytical costs, in contrast to data obtained from Tetra Tech and EPA Region 3, which included these costs as 

part of sample collection. Data validation costs were also obtained for SW-846 method 8260B. The USACE 

provided cost estimates for conducting a pre-sampling building survey that was based on labor costs for two 

people (1/2 day) for 5-15 locations and a unit cost of $600. The USACE also provided estimated total costs for 

collecting “Target Identification” information.

 

• Data Outlier: The cost provided for conducting a pre-sampling building survey was significantly greater 

than the estimated cost provided by Tetra Tech ($600/residence vs. $1,000 per day to sample up to 8 

residences) (see Exhibit B-5). 

Data Analysis 

Cost data were used to estimate a unit cost (e.g., per sample or per well) for performing a particular task. The data 

received from the aforementioned sources were used to calculate the range, median and mean cost values for 

individual tasks that could be used in an SsI investigation. If the unit cost was not provided, it was extrapolated by 

assuming uniformity between total cost and total number of units. For example, if 10 wells were installed for a 

total cost of $18,000, a unit rate of $1,800/well was projected. 

In conducting this analysis, because the data received were often in different formats, assumptions were made, as 

needed, regarding what the provided costs included and into which tasks they appeared to best fit. Additionally, 

unit rates were often calculated based on information assuming a minimum number of units; therefore, unit prices 

may differ depending on the number of samples required at a particular site (i.e., economies of scale). For 

example, the range in unit costs provided by Tetra Tech for collecting sub-slab samples using batch certified 

Summa canisters (see Exhibit B-4) were based on the total costs for collecting 25 samples at residences with 

basements, 15 samples at residences with enclosed crawl spaces and 10 samples at residences without basements 

(e.g., slab-on-grade). Although the daily labor rate and equipment and material costs at each type of sampling 

location were the same, the unit costs ranged from $270-$370 per sample due to the differences in the number of 

days needed to collect the assumed number of samples. 

This CSM analysis assumes the collection of 32 samples (including two background locations); divided equally 

between residences with basements and those constructed with a slab-on-grade foundation). For the purposes of 

this analysis, the unit costs derived from the above data sources were used to calculate the estimated total costs to 
B-5 

the USACE, EPA and an EPA contractor of conducting an SI for SsI. Therefore, the estimated low ($270/sample) 

and high costs ($370/sample) for collecting one of the 32 sub-slab Summa canister samples were calculated based 

on the aforementioned unit costs and not the specific cost of collecting 32 samples. Extrapolating total costs 

below the minimum number of units required for a task may underestimate per unit costs, as there are minimum 

costs associated with some of these tasks. For example, the mean unit rate for collecting a single Tedlar bag 

indoor air quality sample was calculated to be $55; however, the labor to mobilize to the site and deploy a single 

sample is likely much higher. 

Conceptual Site Model

To project the cost of an assessment to evaluate SsI threats, the unit costs provided by EPA Regions, Tetra Tech 

and USACE were applied to a CSM. It is assumed that only SsI is being evaluated as part of the site assessment 

process and that the level of effort entailed would be sufficient to determine whether a site would likely qualify 

for placement on the National Priorities List. Furthermore, the CSM is based on the assumption that a minimum 

of 25 residences are present on or adjacent to the site and reflects the most common waste characteristics scoring 

values used at sites evaluated under the current HRS. Finally, it is assumed that sufficient staff would be available 

to conduct all on-site SI activities in one site visit covering a four-day period. 

General Site Description 

The site is in an old industrial area on the outskirts of an urban area. The site is the location of a release of 

chlorinated solvents from a facility that used solvents during various stages of production to prepare the product 

for further processing. On the facility are solvent storage tanks with varying amounts of solvents, abandoned 

drums of waste solvents and at least one surface impoundment. Contaminated soil areas at the facility have been 

identified in and around these units. A 35-acre residential/commercial area is adjacent to and hydrologically 

downgradient of the facility, with approximately 50 residences, small stores and restaurants.

Geologic Setting 

The site is located in a relatively flat area. The original surface soil is a sandy loam, but at least 60% of the land 

surface is covered by structures, roads and other impervious surfaces. The subsurface soil has a depth of 30 to 40 

feet and is silty sand with fingerings of clay lenses. Depth to ground water varies between 10 and 15 feet. The 

stratum below the silty sand is fractured sandstone.

Known Extent of Contamination 

Based on preliminary sampling, contamination significantly above background has been estimated based on four 

monitoring wells to extend below 70% of the residential/commercial area. Limited sampling in the rest of the area 

indicates sporadic chlorinated solvent contamination above detection limits. Soil gas sampling indicates 

detectable contamination in a subarea that encompasses about 25 residences. Passive diffusion sampling results 

(i.e., contamination in subsurface below structures) suggests subsurface intrusion could occur in 15 homes; the 

other 10 residences have not been sampled. 
B-6 

Demographics 

The ground water in the area is not used as a drinking water supply. Based on real estate listings, the residences 

are mainly three-bedroom homes, averaging 1800 square feet; 50 percent have basements, 25 percent have 

enclosed crawl spaces and the rest have concrete slab foundations. A day care center servicing seven children has

been documented at one of the residences. The county average population per household is 2.6. There are at least 

five commercial structures but they have not been canvassed or sampled.

Estimated Site Inspection Costs to Evaluate SsI Threat 

Because ground water does not represent a current or potential drinking water source, cost estimates have been 

generated assuming SsI as the only pathway being evaluated. A scope of work was developed using previously 

utilized methods for addressing an SsI threat and the following data tables provide low and high value cost 

estimates for conducting site assessment activities based on the cost survey described earlier. If only one cost 

estimate for a task was derived from the data provided, the value was repeated in the high cost column. It was 

assumed sufficient staff and resources would be available to complete on-site SI activities in four days.

Planning, Staging, Oversight and Reporting 

Costs associated with planning, staging, oversight and reporting varied greatly, as expected, depending on the 

scope of work and nature/extent of the site evaluation. The travel, per diem and shipping costs provided by EPA 

Region 3 were consolidated under the “Incidental Costs” task and the reporting costs were consolidated under the 

“Project Management, Oversight and Reporting” task in Exhibit B-1. EPA Region 3 did not provide costs relating 

to planning (except for one site where costs for a health and safety plan and work plan were provided), 

mobilization fees and equipment rental costs. Data received from the USACE included information that enabled 

the calculation of daily rates for certain Exhibit B-1 tasks, with the remaining tasks left defined with perinvestigation costs. Tetra Tech provided either daily or per-investigation rates for relevant tasks.
B-7 

EXHIBIT B-1. COST RANGES FOR CONDUCTING PLANNING, STAGING, OVERSIGHT AND REPORTING 

ACTIVITIES FOR AN SSI SITE INSPECTION

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Planning costs based on previous projects of 

similar size and scope 5,000 10,000 10,000* 100,000* 3,000 5,900

Project mobilization fees (e.g. Geoprobe®) 3,000 3,000 1,000 1,000 N/A N/A

General equipment rental costs based on 

previous projects of similar size and scope

4,000**

(1,000/day)

4,000**

(1,000/day)

400**

(100/day)

2,000**

(500/day) 528 1,055

Field supervision (e.g., well logging, fieldscreening and drilling supervision costs)8,000**

(2,000/day)

8,000**

(2,000/day)

2,000**

(500/day)

8,000**

(2,000/day) 20,500 35,308

Project management, oversight and reporting 

costs based on previous projects of similar size 

and scope

10,000 10,000 10,000* 80,000* 8,000 17,600

Incidental costs (e.g., travel, mileage, 

shipping) based on previous projects of similar 

size and scope

4,000 4,000 100**

(25/day)

2,000**

(500/day) 3,765 11,226

Task subtotal 34,000 39,000 23,500 193,000 35,793 71,089

* Cost estimates provided by Tetra Tech for these tasks were stated to be highly variable depending on such variables as the composition of 

the crew and the size/complexity of the site being investigated. 

** Denotes task costs that are based on a daily rate. All other Exhibit B-1 values represent the cost for a single investigation.

N/A refers to data not provided but assumed to be included in other Exhibit B-1 tasks within the same information source.

Ground Water Characterization 

To further delineate the horizontal extent of ground water contamination, it was projected that a minimum of eight 

monitoring wells throughout the plume and surrounding residential neighborhood would be required. Utilizing the 

four existing monitoring wells, an additional four temporary, exposed screen wells would be installed using direct 

push technology (e.g., Geoprobe®). Because background contaminant levels are necessary to correlate 

contaminant association with the site, two additional temporary, exposed screen wells would be installed upgradient from the source, resulting in a total of six newly installed wells. 
B-8

EXHIBIT B-2. GROUND WATER WELL INSTALLATION AND SAMPLING COSTS

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Installation of six temporary exposed screen monitoring 

wells utilizing direct push technology (USACE and 

EPA Region 6 provided total costs; Tetra Tech 

provided equipment, material and labor costs) 

6,000 9,000 8,160 8,760 3,648 5,328

Sample collection from the six newly installed 

temporary monitoring wells (USACE provided 

equipment, material and labor costs; Tetra Tech 

provided labor costs)

2,400 2,400 1,200 1,200 1,800* 1,800*

Sample collection from the four existing monitoring 

wells (USACE provided equipment, material and labor 

costs; Tetra Tech provided labor costs)

1,600 1,600 800 800 1,200* 1,200*

Task subtotal 10,000 13,000 10,160 10,760 6,648 8,328

* Cost estimates for sample collection were not provided by EPA Regions; therefore, the median of all received cost estimates was used in

this analysis.

Soil Gas Characterization 

To characterize the extent of soil gas contamination, it was projected that a minimum of 10 soil gas samples 

within the residential neighborhood and suspected contaminated ground water plume would be required to 

evaluate the SsI threat. Soil gas samples would be installed using direct push technology. Two soil gas samples 

would need to be collected from locations up-gradient from the source and outside of the zone of influence, 

resulting in a total of 12 soil gas samples being collected. The use of Summa canisters in conjunction with the 

direct push methods would be employed to collect the samples. 

EXHIBIT B-3. SOIL GAS SAMPLING COSTS

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Collection of 12 soil gas samples utilizing direct push 

technology (USACE provided equipment, material and labor 

costs; Tetra Tech provided equipment and labor costs)

3,996 4,800 1,860 2,520 3,264* 3,264* 

Task subtotal 3,996 4,800 1,860 2,520 3,264 3,264

* This sample collection method was not utilized in the examples provided by EPA Regions; therefore, the median of all other received

cost estimates was used in this analysis.

Sub-Slab Vapor Characterization 

To evaluate vapor concentrations beneath homes within the identified residential neighborhood, it was determined 

that the 25 residences suspected to be impacted based on earlier passive soil-gas assessments represented the 

greatest threat. Temporary sub-slab vapor points would be installed in each of these structures using hand-held 
B-9 

roto-hammer methods. An additional five points would be installed in other structures within the neighborhood 

and along the suspected ground water plume boundary. It was assumed that approximately 50 percent of the 

residences where sub-slab vapors are sampled have basements and the remaining 50 percent are slab-on-grade 

construction. All basements were assumed to have concrete floors. Two occupied structures of similar 

construction (i.e., one basement and one slab-on-grade) and socioeconomic status, and located up-gradient of the 

source and outside of the zone of influence, would be needed to establish background sub-slab contaminant 

concentrations. Temporary sub-slab vapor points would be installed in each of these locations as well. Sampling 

from each of the 32 residences would be conducted using Summa canisters and 24-hour sampling periods. 

EXHIBIT B-4. SUB-SLAB SAMPLING COSTS*

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Installation of 32 temporary sub-slab vapor points 

utilizing hand-held roto-hammer methods (USACE 

and Tetra Tech provided equipment, material and 

labor costs; EPA Region 3 specified labor costs)

9,600 9,600 3,360 4,480 5,600 8,000

Sample collection from the 32 newly installed subslab vapor points utilizing Summa canisters and 

24-hour sampling periods (USACE provided labor 

costs; Tetra Tech and EPA Region 3 provided 

Summa canister preparation costs and labor) 

4,800 4,800 8,640 11,840 3,232 11,360

Task subtotal 14,400 14,400 12,000 16,320 8,832 19,360

* Assumes sub-slab vapor points (including the background location) would be installed in 16 homes with basements and 16 with slab-ongrade construction.

Indoor Air Characterization 

To evaluate indoor air vapor concentrations within the residential neighborhood, it was determined that 

comparative values between sub-slab and indoor air concentrations represented the best method for evaluating the 

SsI threat. A total of 32 indoor air quality samples utilizing Summa canisters and 24-hour sampling periods would 

be collected from the same homes where a sub-slab sample would be collected, including from the two homes 

considered to be background. EPA Regional costs estimates did not include costs for conducting pre-sampling 

building surveys; therefore the cost estimates provided by Tetra Tech of $1,000 in labor costs to survey up to 

eight residential buildings per day was used. This information, instead of the median cost for this task from all 

sources, was used as it was provided by an EPA contractor. Cost estimates for conducting a separate background 

indoor air quality sampling event were also provided by Tetra Tech but, as the equipment and labor costs were 

similar to the costs for collecting indoor air samples, these costs were not used. The USACE provided unit and 

total costs for conducting a pre-sampling building survey that included unit costs of $600 per structure (2 people 

for 1⁄2 day) and typical past total costs of $10,000 for up to 15 structures. For the purposes of this cost model, it 

was assumed the best approach would be to calculate the cost of surveying 32 structures based on the unit cost 

provided. 
B-10

EXHIBIT B-5. INDOOR AIR SAMPLING COSTS

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Pre-sampling building survey (labor costs) 19,200 19,200 4,000 4,000 4,000* 4,000*

Sample collection from 32 homes utilizing 

Summa canisters and 24-hour sampling periods 

(USACE provided labor costs; Tetra Tech and 

EPA Region 3 provided Summa canister 

preparation costs and labor)

4,800 4,800 9,920 9,920 3,232 11,360

Task subtotal 24,000 24,000 13,920 13,920 7,232 15,360

* Estimated costs for this task were not received from EPA Regions; therefore, the estimated unit cost provided by Tetra Tech, an EPA

contractor, was used.

Laboratory Analysis 

Based on a review of the cost data received for this analysis, the use of Summa canisters and EPA method TO-15 

analysis for volatile organic compounds (VOCs) appears to represent the most commonly employed approach for 

collection and analysis of air samples. EPA SW-846 method 8260B Modified represents a widely accepted 

method for analysis of ground water samples. It was assumed that, although the analytical method was not cited in 

the information submitted by EPA Region 3 for prior investigations, EPA method TO-15 was used for the 

analysis of air samples. The estimated unit costs provided by eight EPA Regions for data validation of air (six 

Regions) and water (eight Regions) samples were for unknown, variable, streamlined and full levels of review. 

For the purposes of this analysis, the low and high unit costs of all levels of review were used to calculate the total 

cost of data validation. 

EXHIBIT B-6. ANALYTICAL COSTS

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA 

TECH

LOW 

ESTIMATE

($)

TETRA 

TECH

HIGH 

ESTIMATE

($)

EPA 

REGIONS

LOW 

ESTIMATE

($)

EPA 

REGIONS

HIGH 

ESTIMATE

($)

Laboratory analysis of 10 ground water 

samples using EPA method 8260B Modified. 1,000 1,000 850 850 930** 930** 

Laboratory analysis of 76 Summa canister 

samples using EPA Method TO-15 (12 soil 

gas, 32 sub-slabs and 32 indoor air quality).

19,000 19,000 12,540 12,540 19,000 45,600

Data validation (86 samples). 2,393 2,580 1,012 1,442 3,154* 11,490*

Task subtotal 22,393 22,580 14,402 14,832 23,084 58,020

* Estimated unit costs were derived from per sample costs (air and water media) received from eight EPA Regional offices and costs

provided by EPA Region 3 for three previous investigations. It was assumed that data validation costs for investigations provided by 

Region 6 were included in their method analytical costs.

** This analytical method was not utilized in the examples provided by EPA Regions; therefore, the median cost of all other received

estimates was used in this analysis.
B-11

Target Identification

The survey used to solicit cost data for performing various tasks associated with conducting an SsI evaluation 

included a request for estimated costs to identify the composition and use of occupied structures and the number 

of people living or working within each. Tetra Tech stated that this information was covered by their presampling building survey (Exhibit B-5) and EPA Regions did not provide this information. The USACE provided 

cost ranges for each task, where the lower value reflects targets or properties located entirely on federal property. 

EXHIBIT B-7 – TARGET IDENTIFICATION

TASK

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA TECH

ESTIMATE

($)

EPA REGIONS 

ESTIMATE

($)

Identify structure composition for each property within 

the target area (e.g., basement, slab-on-grade). 1,000 15,000

Covered in Exhibit B-5 

Pre-sampling building 

survey 

Not provided

Identify property use characteristics for each property 

within the target area (e.g., residence, retail, office, 

school).

1,000 5,000

Covered in Exhibit B-5 

Pre-sampling building 

survey 

Not provided

Quantify the number of human targets per property (e.g., 

field verify how many people live at each residence? 

year-round?).

5,000 15,000

Covered in Exhibit B-5 

Pre-sampling building 

survey 

Not provided

Task subtotal 7,000 35,000 N/A N/A

N/A refers to either this task being covered by another task or data not having been provided.

Estimated Total SsI Site Inspection Costs

Based on the scope of work and tasks outlined above, the following estimated totals for conducting a site 

assessment where SsI is the primary pathway being evaluated were calculated based on available data:

EXHIBIT B-8 - TOTAL ESTIMATED SITE INSPECTION COSTS FOR SUBSURFACE INTRUSION

USACE

LOW 

ESTIMATE

($)

USACE

HIGH 

ESTIMATE

($)

TETRA TECH

LOW 

ESTIMATE

($)

TETRA TECH

HIGH 

ESTIMATE

($)

EPA REGIONS

LOW 

ESTIMATE

($)

EPA REGIONS

HIGH 

ESTIMATE

($)

MEAN 

($)

MEDIAN

($)

115,789 152,780 75,842 251,352 84,853 175,421 130,502 110,378

The following methods were used to calculate the mean and median total estimated assessment costs for 

individual tasks:

• Cost data for Exhibit B-1 tasks were provided by sources either as a daily rate or as the cost for an entire

investigation. Data provided as a daily rate were converted into the costs for a four-day investigation, with

mean and median values derived from the resulting common dataset.
B-12

• Per unit mean and median costs for individual tasks were multiplied by the number of units required for 

completion in the CSM to determine the total cost for each task.

• The mean and median cost of conducting a pre-sampling building survey (see Exhibit B-5) was derived 

from daily rates of $1,000 and $1,200 provided by Tetra Tech (up to eight residences) and the USACE 

(two residences) respectively.

The mean and median total estimated assessment costs do not include costs from Exhibit B-7-Target 

Identification, as only the USACE provided cost estimates for these tasks.

Factors Influencing Variability in Cost Estimates

The main sources of variability in site assessment costs result from the wide ranges in cost estimates associated 

with planning, project management and reporting, along with incidental costs, as provided by Tetra Tech and EPA

Regions. The ranges in values could be influenced by sources including task costs in different categories. 

Variability could also be the result of comparing cost estimates provided by one source as a daily rate and by 

another source for an entire investigation, as well as the assumptions used in deciding how to categorize the data 

received. Specific areas of variability in this cost analysis include the following: 

• EPA Regional cost data for field supervision, project management and incidental costs tasks (see Exhibit 

B-1) were obtained from previous investigations and may not realistically compare to the costs associated 

with this CSM, due to such factors as the scope, size and location of the projects.

• Data provided by EPA Regions did not contain apparent costs for every relevant task in the CSM. For 

example, the data for previous site investigations received from EPA Region 3 did not include apparent 

costs for such Exhibit B-1 tasks as: project planning, mobilization fees, equipment rental and field 

supervision. The data from EPA Region 6 for previous investigations provided installation costs for 

exposed screen monitoring wells, but not sampling costs. Additionally, one EPA Region 6 cost summary 

noted that the costs for 12 Summa canister samples were included in Exhibit B-1 tasks. Therefore, there is 

the potential for missing cost data or the inclusion of unrelated tasks, resulting in underestimates or 

overestimates, respectively, in Exhibit B-1 costs.

• Data received from Tetra Tech included wide cost ranges ($10,000-$80,000 or $10,000-$100,000 each) 

for such Exhibit B-1 tasks as project planning, project management and reporting. These tasks were noted 

as being highly variable depending on the size, scope and location of the site and the staff needed to 

accomplish the assessment. 

• Analytical cost data provided by EPA Region 3 included an assumed unit cost of $600 per sample for 

Summa canister analysis (see Exhibit B-6). This value was double the next highest value of $300 per 

sample provided by two other EPA Regions. 

• Data validation costs were received from eight EPA Regional offices, with six EPA Regions providing 

per sample cost information for validation of air sample data and water sample data and two EPA Regions 

providing per sample cost information only for validation of water sample data. Costs provided by EPA 

Region 1 for validation of water sample data appeared to be an outlier ($202/sample for streamlined QA 

review and $275/sample for full QA review). The next highest costs were $76/sample (streamlined QA 

review) and $119/sample (full QA review) for EPA Regions 6 and 9, respectively. 

• Discrete target identification costs (see Exhibit B-7) were only provided by the USACE, while Tetra Tech 

stated that this task was covered in the pre-sampling building survey task (see Exhibit B-5). 
B-13

Adjustment of the CSM for use in the Regulatory Impact Analysis

EPA adjusted the CSM in two ways in order to apply the total SI cost estimates to the analysis of the proposed 

rule’s costs:

1. To account for the high degree of variability in the cost estimates provided by different data sources, the 

analysis excludes several outlier cost values. 

2. To compare the costs of the three regulatory options considered in the RIA, the analysis develops two

modified CSMs (in addition to the base case CSM) that include the costs of additional sampling, analysis 

and reporting, as required by each option. 

Treatment of Outliers

EPA considered each of the outlier cost values discussed in this document and decided on a case-by-case basis 

whether to exclude outlier costs from the total cost estimate. Adopting a conservative approach, the analysis 

excludes only high-cost outliers that are not corroborated by at least one other data source. Exhibit B-9 lists the 

outlier values that were excluded from the total estimate of the costs of conducting an SI to evaluate SsI threats, 

together with the range of costs used for each task once outlier values are ignored. 

EXHIBIT B-9. OUTLIER COST VALUES EXCLUDED FROM TOTAL COST ESTIMATES

TASK DATA SOURCE

OUTLIER COST 

ESTIMATE ($)

COST RANGE 

EXCLUDING OUTLIER 

VALUE(S) ($)

Planning costs based on previous projects of similar 

size and scope

Tetra Tech 

(high estimate) 100,000 3,000-10,000

Field supervision (e.g., well logging, field-screening 

and drilling supervision costs)

EPA Region 6 

(all estimates) 20,500-34,031 2,000-8,000

Project management, oversight and reporting costs 

based on previous projects of similar size and scope

Tetra Tech 

(high estimate) 80,000 8,000-17,600

Pre-sampling building survey (labor costs) USACE 

(single estimate) 19,200 4,000-4,800

Laboratory analysis of 76 Summa canister samples 

using EPA Method TO-15 (12 soil gas, 32 sub-slabs 

and 32 indoor air quality).

EPA Region 3 

(single estimate) 45,600 12,540-22,800

After excluding outliers, the analysis uses the median and maximum total cost estimates to represent the costs of 

conducting an SI for SsI threats in the best-estimate and high-end scenarios. These values are presented in Exhibit 

B-10. As with the mean and median total estimated assessment costs presented in Exhibit B-8, the median and 

maximum costs in Exhibit B-10 do not include costs from Exhibit B-7-Target Identification.
B-14

EXHIBIT B-10. MEDIAN AND MAXIMUM TOTAL COST ESTIMATES, EXCLUDING OUTLIERS

TASK MEDIAN COST ($) MAXIMUM COST ($)

Planning, Staging, Oversight and Reporting 33,179 53,826

Ground Water Characterization 9,000 13,000

Soil Gas Characterization 3,258 4,800

Sub-slab Vapor Characterization 14,240 21,440

Indoor Air Characterization 11,760 16,160

Laboratory Analysis and Data Validation 24,281 35,290

Total 95,718 144,516

Alternate CSMs for Regulatory Option Comparison 

As described in the body of the report and in Appendix A, the three regulatory options considered for the 

proposed rulemaking differ in how SsI threats would be scored and—by extension—how investigation of SsI 

threats would be conducted. In order to compare the expected cost impacts of each regulatory option, the analysis 

developed two alternate CSMs in addition to the base case CSM. To develop alternate CSMs, the analysis made 

the following option-specific modifications: 

• Option 1: Option 1 uses the values from the base case CSM.

• Option 2: Option 2 modifies the CSM to include 12 additional ground water and 12 additional soil gas 

samples in order to characterize the extent of the area of subsurface contamination. The CSM for Option 2 

therefore includes the costs of installing additional ground water wells; collecting additional ground water 

and soil gas samples; and analysis and validation of the additional water and vapor samples. Because 

sampling additional ground water and soil gas points is not expected to substantially change the total 

duration of the SI, the analysis does not change planning, staging, oversight and reporting costs for this 

option. 

• Option 3: Option 3 uses the modified CSM as Option 2 (i.e., including all costs associated with 12 

additional ground water and 12 additional soil gas samples) with one addition. To identify the target 

population in the potential groundwater migration zone, the CSM for this option includes 64 person-hours 

of additional analysis and reporting effort. 

Incorporating the modifications listed above, the analysis developed alternate median and maximum cost 

estimates for each of the regulatory options. Exhibit B-11 presents the median costs by task for the base case 

CSM and the two alternate CSMs developed for Options 2 and 3. Total median and maximum cost estimates for 

the three regulatory options are presented in Exhibit B-12. 
B-15

EXHIBIT B-11. MEDIAN COST ESTIMATES BY TASK FOR THE BASE CASE AND ALTERNATIVE CSMS

TASK

OPTION 1

(BASE CASE) MEDIAN COST 

($)

OPTION 2 MEDIAN COST 

($)

OPTION 3 MEDIAN COST 

($)

Planning, Staging, Oversight and 

Reporting 33,179 33,179 33,179

Ground Water Characterization 9,000 24,600 24,600

Soil Gas Characterization 3,258 6,516 6,516

Sub-slab Vapor Characterization 14,240 14,240 14,240

Indoor Air Characterization 11,760 11,760 11,760

Laboratory Analysis and Data 

Validation 24,281 29,579 29,579

Identifying the Potential Ground Water 

Migration Zone 0 0 7,040

Total 95,718 119,874 126,914

EXHIBIT B-12. TOTAL MEDIAN AND MAXIMUM COST ESTIMATES FOR THE THREE REGULATORY OPTIONS

REGULATORY OPTION MEDIAN COST ($) MAXIMUM COST ($)

Option 1 (Base Case CSM) 95,700 144,516

Option 2 119,874 181,596

Option 3 126,914 189,276
C-1 

APPENDIX C: Detailed Methodology for Estimating Impacts on Minority and Low-Income 

Populations 

This appendix documents the assessment of demographic data for populations in the vicinity of sites with 

potential subsurface intrusion (SsI) contamination.38 The primary objective of the demographic analysis is to 

determine whether socioeconomically disadvantaged populations (e.g., racial minority and low-income 

communities) are located preferentially within the vicinity of sites potentially affected by the proposed rule. This 

analysis provides information related to potential environmental justice concerns regarding the location of 

potentially affected sites. Because the proposed rule does not require actions that directly affect human health risk, 

this analysis does not connect population information with potential health risks and is therefore not a full 

environmental justice analysis.

Methodology 

This analysis is based on population statistics from the 2000 Census that indicate the prevalence of potentially 

disadvantaged populations (e.g., racial minorities). The analysis compares “potentially affected populations” in 

the vicinity (i.e., within one-mile and three-mile radii) of sites with potential SsI contamination to “reference 

populations” (county-level populations). This comparison indicates whether potentially disadvantaged 

populations are located preferentially within the vicinity of SsI sites. Data sources and analysis methods are 

described below. 

Potentially Affected and Reference Communities

To represent potentially affected populations, the demographic analysis selected sites from the list of sites 

potentially affected by the proposed rule. For 47 of the approximately 1,073 sites in this list, latitude and 

longitude data were obtained from the data sources used to populate the group of sites.

39 The analysis used street 

address data to determine geographic coordinates for an additional 193 sites, for a total of 240 sites used in the 

demographic analysis. Sufficient data were not available to determine a precise geographic location for the 

remaining sites in the list. Exhibit C-1 presents the distribution of selected sites across the U.S. Environmental 

Protection Agency (EPA) regions. Though the selected sites come from all ten EPA regions, they are not evenly 

distributed, with the highest percentage of sites in Regions 6 and 8. 

 

38 The analysis follows methods outlined in “Analysis of Statistics for Populations Residing Near UST Facilities,” Memorandum prepared by RTI International, 

July 22, 2010.

39 See Chapter 2 of this report for a detailed description of the site sites potentially affected by the proposed rule.
C-2 

EXHIBIT C-1. EPA REGIONAL DISTRIBUTION OF SITES SELECTED FOR THE DEMOGRAPHIC ANALYSIS

EPA REGION

NUMBER OF SITES

ANALYZED

PERCENTAGE OF 

TOTAL SITES

Region 1 5 2.1%

Region 2 27 11.3%

Region 3 32 13.3%

Region 4 21 8.8%

Region 5 13 5.4%

Region 6 55 22.9%

Region 7 13 5.4%

Region 8 56 23.3%

Region 9 17 7.1%

Region 10 1 0.4%

Total 240 100.0%

Lacking more conclusive information about the geographic spread of potentially affected sites, the analysis 

assumes that the geographic coordinates used for each site represent centroids of the site’s extent. In order to 

ensure that the demographic analysis considers all communities potentially affected by SsI contamination and 

remedial actions, the analysis defines “potentially affected populations” in two ways:

1) All people living within a one-mile radius of potentially affected sites, and

2) All people living within a three-mile radius of potentially affected sites.

These distances were chosen to accommodate the size of potential Superfund sites, which may range from a 

single facility to a large military installation spanning several square miles. In addition, these radii address the 

uncertainty related to both the spatial extent of plumes and SsI pathways, and the uncertainty related to location of 

site boundaries. 

The analysis uses county-level populations as references to which the potentially affected populations are 

compared. County-level statistics provide a useful comparative measure of populations at a scale that is larger 

than the site level but still local enough to allow the analysis to distinguish between local demographic shifts and 

regional demographic patterns (e.g., higher minority populations in the southeastern U.S.). Exhibit C-2 compares 

the (unweighted) average demographic characteristics of the counties surrounding potentially affected sites to 

national averages. As the exhibit shows, the selected counties have, on average, lower concentrations of both 

minority and low-income populations, relative to the country as a whole. However, these differences are not 

statistically significant.
C-3 

EXHIBIT C-2. DEMOGRAPHIC CHARACTERISTICS OF COUNTIES SURROUNDING SELECTED SITES

DEMOGRAPHIC 

CHARACTERISTIC

COUNTIES AROUND 

SELECTED SITES NATIONAL AVERAGE

Percent Minority Population 28.7% 31.0%

Percent Below Poverty Level 12.3% 13.0%

Socioeconomic Census Data

The analysis evaluates the following socioeconomic parameters from the 2000 Census for the potentially affected 

and reference populations: 

• Percent minority population (including both percent nonwhite and percent white Hispanic) 

• Percent below poverty level (i.e., the percentage of individuals below the Federal poverty line in 1999). 

These parameters were selected in order to best address the populations of concern identified in Executive Order 

12898 (Environmental Justice). The smallest unit at which these data are available is the Census block group. The 

analysis retrieved county-level data directly from the 2000 Census county-level results. To obtain demographic 

data for the potentially affected populations, the analysis employed an ArcGIS aggregation of associated block 

groups within one- and three-mile buffers of the selected sites, as described in more detail below.

Data for Potentially Affected Populations 

The analysis used ArcGIS software to define one- and three-mile buffers around each selected site and collate 

socioeconomic data for the block groups contained within these buffers. When apportioning 2000 census block 

group data to the buffers around each site, the analysis employed aerial apportionment to assess the demographic 

characteristics of populations living near each facility. Under this approach, if x percent of a block group’s land 

area is within the one-mile (or three-mile) buffer around a facility, the analysis assumed that x percent of the 

block group’s population is also within the one-mile (or three-mile) buffer. This approach relies on the 

assumption that populations are evenly distributed across block groups, which is a limitation of the analysis. 

However, in the absence of demographic data at a smaller unit than census block groups, EPA determined that 

this approach was reasonable.

Results

Exhibits C-3 and C-4 present the results of the unweighted demographic analysis, including the mean and median 

values for each Census socioeconomic indicator and for each population (i.e. potentially affected and reference 

populations) as well as the mean and median difference in percentages between populations. Exhibit C-3 presents 

unweighted results for the one-mile buffer and Exhibit C-4 presents results for the three-mile buffer. In each 

exhibit, the difference values result from subtracting the reference community values from the potentially affected 

community values (so that a positive result indicates a greater percentage in the potentially affected community). 

A difference result was produced for each site, thus generating a distribution of 240 difference values. The 

exhibits also provide the estimated 95 percent confidence intervals for the mean differences (i.e., based on the 
C-4 

statistical evaluation, it can be concluded with 95 percent confidence that the differences in means are between the 

upper and lower bounds listed in the exhibits). 

The results in Exhibits C-3 and C-4 show that the mean differences are relatively small (less than four percent in 

all cases). However, the differences in the means do consistently suggest that the potentially disadvantaged 

populations are present at slightly greater percentages in the vicinity of VI sites, both within the one- and threemile radii. Specifically, the difference value for percent minority population is roughly four percent higher than 

the county level within the one-mile buffer and about three percent higher than the county level for the three-mile 

buffer. The poverty differences are similarly small positive values: about two percent higher than the county level 

for both the one-mile buffer and the three-mile buffer. 

Exhibits C-5 and C-6 provide additional statistical results, including standard errors of the mean (SE), a relative 

risk ratio (i.e., the mean of potentially affected populations divided by the mean of the reference populations), 

results of a T test evaluating the statistical significance of the difference in means (i.e., whether the differences in 

the estimated demographic characteristics are statistically significant). Results for the one-mile buffer are 

presented in Exhibit C-5, while Exhibit C-6 has results for the three-mile buffer. The T test evaluates the null 

hypothesis that the means between the reference and potentially affected populations are equal. The resulting pvalues indicate the probability of observing differences larger than the observed differences under the test 

assumption that the null hypothesis is true. For the population within the one-mile buffer, the differences in 

percent minority population and percent below poverty level with respect to the reference population are 

significant at the 99 percent certainty level, as indicated by the p values less than 0.01 for both comparisons. This 

equates to a probability of less than one percent that the results reflect a random distribution. Similarly, for the 

population within the three-mile buffer, the difference in percent minority population is statistically significant at 

the 95 percent certainty level (p-value of 0.036) and the difference in percent below poverty level is significant at 

the 99 percent certainty level (p-value <0.01). 

Exhibits C-7, C-8, C-9 and C-10 present results for the population-weighted statistical analysis. The patterns in 

the results are similar to the unweighted results in Exhibits C-3 through C-6. However, the relative magnitudes of 

the population differences are larger for the weighted analysis results. Comparison of the weighted and 

unweighted results suggests that sites in higher population areas tend to have more pronounced differences 

between the local, potentially affected communities and the reference, county-level communities. 

Exhibit C-11 presents results of an analysis conducted to determine if updated census data (i.e., since the 2000 

U.S. Census) would indicate that the proportions of minority and below poverty level populations (weighted) 

found in 1- and 3-mile buffers around the same sites analyzed using 2000 U.S. Census data had decreased. The 

results show that the proportion of the minority and below poverty level populations found within the 1- and 3-

mile buffers around the same 240 sites analyzed using 2000 U.S. Census data did not decrease. A one-sided twosample Z-test (testing for decreases only) of the minority and below-poverty-level proportions was performed for 

each buffer. For all four comparisons, the p-values were greater than 0.99, indicating that the null hypothesis that 

the percentage of minorities and below-poverty-level populations around the 240 sites did not decrease could not 

be rejected. Therefore, conclusions made based on the 2000 Census data regarding the potentially affected 

populations could still be applied to the 240 sites. A key limitation of the population-weighted results, however, 

is the assumption of even distribution of population across census block groups. If populations are distributed 

unevenly either toward or away from individual sites, then the results of this analysis could change significantly. 

Additionally, the 2009-2013 American Community Survey data based the population below the poverty level as 

being based on the household level, while the population-weighted analysis using 2000 U.S. Census data based 

the below poverty level population on the number of people for which income data was available. As a result, the 
C-5 

population-weighted results are uncertain and should only be used as a general qualitative indicator that 

population density may be an important factor in a full analysis of environmental justice impacts.

Conclusion

In summary, this analysis used Census data to compare demographic characteristics for potentially affected 

populations in the vicinity of vapor intrusion sites versus reference communities (county-level populations). The 

differences in the mean percentage socioeconomic results between the potentially affected and the reference 

communities are relatively small (less than four percent in all cases). However, the differences are statistically 

significant in all cases, and the results do suggest that potentially disadvantaged populations are located 

preferentially in the vicinity of sites with potential SsI threats. 
C-6 

EXHIBIT C-3. SUMMARY RESULTS FOR CENSUS PARAMETERS: 1-MILE BUFFER (UNWEIGHTED)

CENSUS PARAMETER

1-MILE BUFFER AROUND 

FACILITY

COUNTY WHERE FACILITY 

IS LOCATED DIFFERENCE

MEAN MEDIAN MEAN MEDIAN MEAN MEDIAN

95% CONFIDENCE INTERVAL OF 

MEAN DIFFERENCE

LOWER BOUND UPPER BOUND

Percent Minority Population 32.3% 25.0% 28.7% 24.4% 3.66% 1.74% 1.05% 6.26% 

Percent Below Poverty Level 15.4% 12.7% 12.3% 11.1% 3.08% 1.74% 1.86% 4.31% 

Note: Difference summary statistics (mean and median) were calculated from the distribution of difference values (i.e., one result per facility, 

yielding a distribution of 240 results). Mean values reflect the entire distribution, whereas the median values are based only on the 50th percentile 

result. For this reason, the mean difference results could also be calculated simply by subtracting the reference community mean from the potentially 

affected community mean (e.g., for mean percent below the poverty line in the one-mile buffer 15.4 – 12.3 = 3.08). In contrast, the median difference 

values do not necessarily match values derived by subtracting the median values from the underlying distributions. Although the primary results of the 

analysis are based on mean values, median results are provided for completeness and as an alternative indicator of the distributions’ central tendency.

EXHIBIT C-4. SUMMARY RESULTS FOR CENSUS PARAMETERS: 3-MILE BUFFER (UNWEIGHTED)

CENSUS PARAMETER

3-MILE BUFFER AROUND 

FACILITY

COUNTY WHERE FACILITY 

IS LOCATED DIFFERENCE

MEAN MEDIAN MEAN MEDIAN MEAN MEDIAN

95% CONFIDENCE INTERVAL OF 

MEAN DIFFERENCE

LOWER BOUND UPPER BOUND

PERCENT MINORITY POPULATION 30.8% 25.9% 28.7% 24.4% 2.17% 1.10% 0.15% 4.19% 

PERCENT BELOW POVERTY LEVEL 14.2% 12.6% 12.3% 11.1% 1.88% 1.04% 1.04% 2.72% 

Note: Difference summary statistics (mean and median) were calculated from the distribution of difference values (i.e., one result per facility, 

yielding a distribution of 240 results). Mean values reflect the entire distribution, whereas the median values are based only on the 50th percentile 

result. For this reason, the mean difference results could also be calculated simply by subtracting the reference community mean from the potentially 

affected community mean (e.g., for mean percent below the poverty line in the one-mile buffer 14.2 – 12.6 = 1.88). In contrast, the median difference 

values do not necessarily match values derived by subtracting the median values from the underlying distributions. Although the primary results of the 

analysis are based on mean values, median results are provided for completeness and as an alternative indicator of the distributions’ central tendency.
C-7

EXHIBIT C-5. STANDARD ERROR, T TEST AND RISK RATIO RESULTS: 1-MILE BUFFER (UNWEIGHTED)

CENSUS PARAMETER

1-MILE BUFFER

AROUND SITE

COUNTY WHERE 

FACILITY IS 

LOCATED DIFFERENCE

STANDARD ERROR 

OF MEAN

STANDARD ERROR 

OF MEAN

STANDARD ERROR

OF MEAN T-STATISTIC P-VALUE RATIO SE OF RATIO

PERCENT MINORITY POPULATION 0.0171 0.0123 0.0133 2.75 0.0064 1.13 0.0512 

PERCENT BELOW POVERTY LEVEL 0.0070 0.0035 0.0063 4.93 <0.001 1.25 0.0539

EXHIBIT C-6. STANDARD ERROR, T TEST AND RISK RATIO RESULTS: 3-MILE BUFFER (UNWEIGHTED)

CENSUS PARAMETER

3-MILE BUFFER

AROUND SITE

COUNTY WHERE 

FACILITY IS 

LOCATED DIFFERENCE

STANDARD ERROR 

OF MEAN

STANDARD ERROR 

OF MEAN

STANDARD ERROR

OF MEAN T-STATISTIC P-VALUE RATIO SE OF RATIO

PERCENT MINORITY POPULATION 0.0151 0.0123 0.0103 2.11 0.036 1.08 0.0399

PERCENT BELOW POVERTY LEVEL 0.0051 0.0035 0.0043 4.38 <0.001 1.15 0.0363
C-8 

EXHIBIT C-7. SUMMARY RESULTS FOR CENSUS PARAMETERS: 1-MILE BUFFER (WEIGHTED)

CENSUS PARAMETER

1-MILE BUFFER AROUND 

FACILITY

COUNTY WHERE FACILITY 

IS LOCATED DIFFERENCE

MEAN MEDIAN MEAN MEDIAN MEAN MEDIAN

95% CONFIDENCE INTERVAL OF 

MEAN DIFFERENCE

LOWER BOUND UPPER BOUND

PERCENT MINORITY POPULATION 41.1% 14.8% 32.9% 14.9% 8.23% 0.332% 4.13% 12.3% 

PERCENT BELOW POVERTY LEVEL 16.8% 8.84% 11.6% 7.37% 5.22% 0.312% 3.33% 7.11% 

Notes: 

1. Difference summary statistics (mean and median) were calculated from the distribution of difference values (i.e., one result per facility, yielding a 

distribution of 240 results). Mean values reflect the entire distribution, whereas the median values are based only on the 50th percentile result. For 

this reason, the mean difference results could also be calculated simply by subtracting the reference community mean from the potentially 

affected community mean (e.g., for mean percent below the poverty line in the one-mile buffer 16.8 – 11.6 = 5.22). In contrast, the median 

difference values do not necessarily match values derived by subtracting the median values from the underlying distributions. Although the primary 

results of the analysis are based on mean values, median results are provided for completeness and as an alternative indicator of the distributions’ 

central tendency.

2. In the weighted analysis, the county-level demographic characteristic for the one-mile buffer comparison are different from the characteristics for 

the three-mile buffer comparison because the county-level characteristics are weighted by the population around the site, which varies by buffer 

size. 
C-9 

EXHIBIT C-8. SUMMARY RESULTS FOR CENSUS PARAMETERS: 3-MILE BUFFER (WEIGHTED)

CENSUS PARAMETER

3-MILE BUFFER AROUND 

FACILITY

COUNTY WHERE FACILITY 

IS LOCATED DIFFERENCE

MEAN MEDIAN MEAN MEDIAN MEAN MEDIAN

95% CONFIDENCE INTERVAL OF 

MEAN DIFFERENCE

LOWER BOUND UPPER BOUND

PERCENT MINORITY POPULATION 41.8% 15.7% 35.9% 15.3% 5.90% 0.186% 2.74% 9.06% 

PERCENT BELOW POVERTY LEVEL 14.8% 7.19% 11.6% 7.04% 3.16% 0.196% 2.00% 4.33% 

Notes: 

1. Difference summary statistics (mean and median) were calculated from the distribution of difference values (i.e., one result per facility, yielding a 

distribution of 240 results). Mean values reflect the entire distribution, whereas the median values are based only on the 50th percentile result. For 

this reason, the mean difference results could also be calculated simply by subtracting the reference community mean from the potentially 

affected community mean (e.g., for mean percent below the poverty line in the one-mile buffer 14.8 – 11.6 = 3.16). In contrast, the median 

difference values do not necessarily match values derived by subtracting the median values from the underlying distributions. Although the primary 

results of the analysis are based on mean values, median results are provided for completeness and as an alternative indicator of the distributions’ 

central tendency.

2. In the weighted analysis, the county-level demographic characteristic for the one-mile buffer comparison are different from the characteristics for 

the three-mile buffer comparison because the county-level characteristics are weighted by the population around the site, which varies by buffer 

size.

EXHIBIT C-9. STANDARD ERROR, T TEST AND RI SK RATIO RESULTS: 1-MILE BUFFER (WEIGHTED)

CENSUS PARAMETER

1-MILE BUFFER 

AROUND 

FACILITY

COUNTY WHERE 

FACILITY IS 

LOCATED DIFFERENCE

STANDARD ERROR 

OF MEAN

STANDARD ERROR 

OF MEAN

STANDARD ERROR

OF MEAN T-STATISTIC P-VALUE RATIO SE OF RATIO

PERCENT MINORITY POPULATION 0.0421 0.0311 0.0209 3.94 <0.001 1.25 0.110

PERCENT BELOW POVERTY LEVEL 0.0146 0.0087 0.0096 5.42 <0.001 1.45 0.126
C-10

EXHIBIT C-10. STANDARD ERROR, T TEST AND RISK RATIO RESULTS: 3-MILE BUFFER (WEIGHTED)

CENSUS PARAMETER

3-MILE BUFFER 

AROUND 

FACILITY

COUNTY WHERE 

FACILITY IS 

LOCATED DIFFERENCE

STANDARD ERROR 

OF MEAN

STANDARD ERROR 

OF MEAN

STANDARD ERROR

OF MEAN T-STATISTIC P-VALUE RATIO SE OF RATIO

PERCENT MINORITY POPULATION 0.0477 0.0381 0.0164 3.60 <0.001 1.16 0.099

PERCENT BELOW POVERTY LEVEL 0.0131 0.0101 0.0064 4.95 <0.001 1.27 0.101

EXHIBIT C-11. DEMOGRAPHIC CHARACTERISTICS OF THE POPULATIONS SURROUNDING SITES POTENTIALLY AFFECTED BY THE PROPOSED RULE 

1-MILE BUFFER AROUND SITES 3-MILE BUFFER AROUND SITES

MEAN* 

(2000 U.S. 

CENSUS)*

MEAN

(2009-2013 ACS)

DIFFERENCE IN 

MEANS

MEAN* 

(2000 U.S. 

CENSUS)

MEAN

(2009-2013 ACS)

DIFFERENCE IN 

MEANS

Percent Minority Population 41.1% 46.1% -5.0% 41.8% 47.7% -5.0%

Percent Below Poverty Level 16.8% 18.8% -2.0% 14.8% 16.4% -5.0%

*WEIGHTED MEANS USED IN THE ANALYSIS USING 2000 U.S. CENSUS DATA
D-1

APPENDIX D: Costs for Vapor Intrusion Site Inspection Tasks Compiled for Regulatory Impact Analysis 

EXHIBIT D-1. SUMMARY STATISTICS FOR VAPOR INTRUSION SITE INSPECTION TASK COSTS 

Task Task Name Units

Range 

($)

Max Value

($)

Min Value 

($)

Mean

($)

Median

($)

CSM Mean 

($)

CSM 

Median 

($)

CSM 

Max 

($)

Min - No 

Outliers ($)

Mean - No 

Outliers 

($)

Median -

No 

Outliers 

($)

Max - No 

Outliers ($)

Planning, Staging, Oversight, and Reporting 

1 Project Planning Costs - provided from past investigations (e.g., sampling plan 

development) 

Per 

Investigation 3000 - 10000 100,000 3,000 15,015 4,750 15,015 4,750 100,000 3,000 5,572 4,500 10,000

3 Project Mobilization Fees for Past Investigations (e.g., staging costs)

Per 

Investigation 3000 3,000 1,250 N/A N/A 2,000 2,000 3,000 1,000 2,000 2,000 3,000

8 General Equipment Rental Costs - provided from past investigations (e.g., peristaltic 

pump, air pumps, photo ionization detector)

Per 

Investigation 528 - 1055 4,000 400 1,448 879 1,448 879 4,000 400 1,448 879 4,000

10 Field Supervision Costs - provided from past investigations (e.g., well-logging, fieldscreening, well development, sample collection)

Per 

Investigation 20500 - 35308 35,308 2,000 19,044 20,500 19,044 20,500 35,308 2,000 6,000 8,000 8,000

12 Project Management, Oversight, and Reporting Costs - provided from past investigations 

(e.g., project planning, report preparation)

Per 

Investigation 8000 - 17600 80,000 8,000 18,354 12,000 18,354 12,000 80,000 8,000 12,189 12,000 17,600

15 Incidental Costs - provided from past investigations (e.g., travel, mileage, sample 

shipping, personal protective equipment (PPE)

Per 

Investigation 3765 - 11226 11,226 100 5,907 5,800 5,907 5,800 11,226 100 5,907 5,800 11,226

Ground Water Well Installation 

18 Direct Push Technology – Exposed Screen Monitoring Well Installation Per Well 608 - 1500 1,500 608 1,084 1,000 6,501 6,000 9,000 3,648 6,501 6,000 9,000

Ground Water Well Sampling 

24 Direct Push Technology - Exposed Screen Monitoring Well Single Sampling Event Per Well 200 - 400 400 200 300 300 1,800 1,800 2,400 1,200 1,800 1,800 2,400

26 Additional Well Sampling Event Per Well 200 - 400 400 200 300 300 1,200 1,200 1,600 1,200 1,200 1,200 1,600

Soil Gas Sampling 

30 Direct Push Technology - soil-gas sample collection (PRT sampling) Per Sample 155 - 400 400 155 275 272 3,294 3,258 4,800 1,860 3,294 3,258 4,800

Sub-slab and Crawl Space Vapor Probe Installation

34 Roto-hammer-drill - Installation only of sub-slab soil-gas probes Per Probe 105 - 300 300 105 192 175 6,149 5,600 9,600 3,360 6,149 5,600 9,600

Sub-slab and Crawl Space Sampling 

35 Sub-slab sample collection utilizing Summa canisters Per Sample 101 - 370 370 101 257 270 8,219 8,640 11,840 3,232 8,219 8,640 11,840

Indoor Air Quality Assessment

41 Pre-sampling Building Survey Daily 1000 - 1200 1,200 1,000 1,100 1,100 4,400 4,400 4,800 4,000 4,400 4,400 4,800

42 Summa canister sampling (assumes batch certification, see comments section) Per Sample 101 - 355 355 101 229 230 7,328 7,360 11,360 3,232 7,328 7,360 11,360

Analytical Costs 

47 GC/MS TO-15 (i.e. Polar and nonpolar VOCs – canister) Per Sample 165 - 600 600 165 311 275 23,623 20,900 45,600 12,540 19,228 19,000 22,800

52 GC/MS 8260B Modified (i.e. VOCs – syringe, bag, vial) Per Sample 85 - 100 100 85 93 93 925 925 1,000 850 925 925 1,000

57 Data Validation (air media) Per Sample 10 - 115 115 10 59 51 4,519 3,876 8,740 760 4,519 3,876 8,740

58 Data Validation (water media) Per Sample 10 - 275 275 10 74.6 48 746 480 2,750 100 746 480 2,750

Target Identification

59 Identify structure composition for each property within the target area (e.g., basement, 

slab-on-grade)

Per 

Investigation 1000 - 15000 15,000 1,000 N/A N/A

60 Identify property use characteristics for each property within the target area (e.g., 

residence, retail, office, school)

Per 

Investigation 1000 - 5000 5,000 1,000 N/A N/A

61 Quantify the number of human targets per property (e.g., field verify how many people 

live at each residence and year-round)

Per 

Investigation 5000 - 15000 15,000 5,000 N/A N/A

Additional Option 2 and 3 SsI Investigative Costs:

18 Direct Push Technology – Exposed Screen Monitoring Well Installation Per Well 608 - 1500 1,500 608 1,084 1,000 13,003 12,000 18,000 7,296 13,003 12,000 18,000

24 Direct Push Technology - Exposed Screen Monitoring Well Single Sampling Event Per Well 200 - 400 400 200 300 300 3,600 3,600 4,800 2,400 3,600 3,600 4,800

30 Direct Push Technology - soil-gas sample collection (PRT sampling) Per Sample 155 - 400 400 155 275 272 3,294 3,258 4,800 1,860 3,294 3,258 4,800

47 GC/MS TO-15 (i.e. Polar and nonpolar VOCs – canister) Per Sample 165 - 600 600 165 311 275 3,730 3,300 7,200 1,980 3,036 3,000 3,600

52 GC/MS 8260B Modified (i.e. VOCs – syringe, bag, vial) Per Sample 85 - 100 100 85 93 93 1,110 1,110 1,200 1,020 1,110 1,110 1,200

57 Data Validation (air media) Per Sample 10 - 115 115 10 59 51 714 612 1,380 120 714 612 1,380

58 Data Validation (water media) Per Sample 10 - 275 275 10 75 48 896 576 3,300 120 896 576 3,300
D-2

Min - No Mean - No Median - Max - No 

CSM CSM Outliers ($) Outliers No Outliers ($)

Range Max Value Min Value Mean Median CSM Mean Median Max ($) Outliers 

Task Task Name Units ($) ($) ($) ($) ($) ($) ($) ($) ($)

Option 3 Additional Reporting Costs

66 Identifying the target population in the "Potential Ground Water Migration Zone"

Per 

Investigation 6400-7680 7,680 6,400 7,040 7,040 7,040 7,040 7,680 6,400 7,040 7,040 7,680

Total 

(Option 

1)

130,472 110,368 347,024 50,482 97,425 95,718 144,516

Total 

(Option 

2)

156,818 134,824 387,704 65,278 123,077 119,874 181,596

Total 

(Option 

3)

163,858 141,864 395,384 71,678 130,117 126,914 189,276

EXHIBIT D-2. EPA REGIONAL/CLP ANALYTICAL AND DATA VALIDATION COSTS

R3 R3 

R2 Var. QA Var. QA R4 R4 R5 

R1 R1 Unknown Costs Costs Full QA Full QA Unknown R6 R6 R9 R10 Strl. EPA CLP EPA CLP 

Strl. QA Full QA Level QA Low Est. High Est. Low Est. High Est. Level QA Strl. QA Full QA Strl. QA QA Low Est. High Est. R 5 email

Task Task Name Units ($) ($) ($) ($) ($) ($) ($) ($) ($) ($) ($) ($) ($) ($) ($)

Analytical Costs

GC/MS TO-15 (i.e. Polar and nonpolar 

47 VOCs – canister) Per Sample 300

56 OERR/AOC SOW OLC03.2 Per Sample 65 210

57 Data Validation (air media) Per Sample 51 71 87 40 60 48 115 39

58 Data Validation (water media) Per Sample 202 275 19 50 40 60 48 76 115 119 32.84

EXHIBIT D-3. COMPREHENSIVE SUMMARY COSTS FOR VAPOR INTRUSION SITE INSPECTION TASKS 

R3

Site B R3 TetraTech

Task Task Name Units

R6

Site 

($)

A 

R6

Site 

($)

B 

R6 

Site 

($)

C

R6

Site D

($)

R3

Site A

($)

Summa 

Canister

($) 

Site B 

TAGA

($) 

R3

Site 

($)

C 

USACE 

Low Est.

($) 

USACE

High Est.

($)

TetraTech

Low Est.

($)

Mid-range 

Est.

($)

TetraTech

High Est.

($)

Planning, Staging, Oversight, and Reporting

Per 

1 Project Planning Costs - provided from past investigations (e.g., sampling plan development) Investigation 5,900 4,500 4,245 4,500 3,000 3,000 5,000 10,000 10,000 100,000

Per 

3 Project Mobilization Fees for Past Investigations (e.g., staging costs) Investigation 3,000 1,250

8 

General Equipment Rental Costs - provided 

air pumps, photo ionization detector)

from past investigations (e.g., peristaltic pump, Per 

Investigation 1,055 528 703 4,000 400 2,000

10

Field Supervision Costs - provided from 

well development, sample collection)

past investigations (e.g., well-logging, field-screening, Per 

Investigation 20,500 35,308 25,469 34,031 8,000 2,000 8,000

12

Project 

project 

Management, Oversight, and Reporting 

planning, report preparation)

Costs - provided from past investigations (e.g., Per 

Investigation 17,600 17,060 12,734 10,500 8,000 12,000 12,000 12,000 10,000 10,000 80,000

15

Incidental Costs - provided from past 

personal protective equipment (PPE)

investigations (e.g., travel, mileage, sample shipping, Per 

Investigation 3,765 11,226 7,171 5,662 10,975 6,750 5,800 7,525 4,000 100 2,000

Ground Water Well Installation 

17 Conventional Monitoring Well Installation Per Well 3,000 1,800 1,950

18 Direct Push Technology – Exposed Screen Monitoring Well Installation Per Well 608 888 769 1,000 1,500 1,360 1,460

Ground Water Well Sampling 

24 Direct Push Technology - Exposed Screen Monitoring Well Single Sampling Event Per Well 400 200
D-3 

R3

Site B R3 TetraTech

Task Task Name Units

R6

Site 

($)

A 

R6

Site 

($)

B 

R6 

Site 

($)

C

R6

Site D

($)

R3

Site A

($)

Summa 

Canister

($) 

Site B 

TAGA

($) 

R3

Site 

($)

C 

USACE 

Low Est.

($) 

USACE

High Est.

($)

TetraTech

Low Est.

($)

Mid-range 

Est.

($)

TetraTech

High Est.

($)

26 Additional Well Sampling Event Per Well 400 200 

 Soil Gas Sampling 

30 Direct Push Technology - soil-gas sample collection (PRT sampling) Per Sample 333 400 155 210

 Sub-slab and Crawl Space Vapor Probe Installation 

34 Roto-hammer-drill - Installation only of sub-slab soil-gas probes Per Probe 250 175 175 200 300 105 140

 Sub-slab and Crawl Space Sampling 

35 Sub-slab sample collection utilizing Summa canisters Per Sample 355 242 101 150 270 310 370

 Indoor Air Quality Assessment 

41 Pre-sampling Building Survey Daily 1,200 1,000 

42 Summa canister sampling (assumes batch certification, see comments section) Per Sample 355 101 150 310 

 Analytical Costs 

47 GC/MS TO-15 (i.e. Polar and nonpolar VOCs – canister) Per Sample 600 250 300 250 165 

52 GC/MS 8260B Modified (i.e. VOCs – syringe, bag, vial) Per Sample 100 85 

57 Data Validation (air media) Per Sample 100 100 100 100 28 30 10 15 17

58 Data Validation (water media) Per Sample 28 30 10 15

 Target Identification 

59

Identify structure 

on-grade)

composition for each property within the target area (e.g., basement, slab- Per 

Investigation 1,000 15,000 

60

Identify property use 

retail, office, school)

characteristics for each property within the target area (e.g., residence, Per 

Investigation 1,000 5,000 

61

Quantify the number of human targets 

each residence and year-round) 

per property (e.g., field verify how many people live at Per 

Investigation 5,000 15,000 

Additional Option 2 & Option 3 Site Investigation Costs: 

18 Direct Push Technology – Exposed Screen Monitoring Well Installation Per Well 608 888 769 1,000 1,500 1,360 1,460

24 Direct Push Technology - Exposed Screen Monitoring Well Single Sampling Event Per Well 400 200 

30 Direct Push Technology - soil-gas sample collection (PRT sampling) Per Sample 333 400 155 210

47 GC/MS TO-15 (i.e. Polar and nonpolar VOCs – canister) Per Sample 600 250 300 250 165 

52 GC/MS 8260B Modified (i.e. VOCs – syringe, bag, vial) Per Sample 100 85 

57 Data Validation (air media) Per Sample 100 100 100 100 28 30 10 15 17

58 Data Validation (water media) Per Sample 28 30 10 15

Option 3 Additional Reporting Costs

Per 

66 Identifying the target population in the "Potential Ground Water Migration Zone" Investigation 6,400 7,680 7,680 

Notes:

1 N/A refers to a value not calculated due to only one value being provided or insufficient data available to perform a calculation.

2 R = EPA Regional Office (e.g., R6 = EPA Region 6)

3 When only one value was provided for an individual task, it was placed in the "low estimate" column.

Final values utilized provided via Tetra Tech Inc. and USACE when calculating or adding unit values, therefore the final task values provided may not equal the sum of the 4 

individual costs used in their calculation. When realistic, cost information received for multiple groups was combined into larger groupings.

5 The cost data provided for the EPA Region 3 Site B investigation was presented for conducting an investigation with Summa canisters or the TAGA bus.

6 The cost data provided for the EPA Region 3 Site C investigation was assumed to be an investigation conducted in two parts, with the TAGA analysis included in the second trip.

Tetra Tech Inc. provided costs for conducting a background indoor air quality sampling event, but as the equipment and labor costs were similar, these costs were not included in 7 the spreadsheet. The only difference was that labor costs were $1,000/day instead of $1,500/day.

Abbreviations:

1 CSM = conceptual site model

2 PRT = post run tubing

3 VOCs = volatile organic compounds
D-4 

4 QA = quality assurance

5 EPA CLP = U.S. Environmental Protection Agency Contract Laboratory Program

6 USACE = U.S. Army Corps of Engineers

Assumptions: 

1 Analytical methods and costs were often provided separately for ground water, soil gas, vapor intrusion and indoor air media, but with equal costs, therefore information was 

combined into one grouping.

2 Cost estimates provided by EPA included costs for conducting a separate background indoor air quality sampling event. It was assumed that costs for conducting a background 

indoor air quality sampling event would be similar to the costs listed in tasks 41-46, therefore no separate breakout costs were provided.

3 Summa canister preparation costs were noted when provided, otherwise they were assumed to be included in other provided costs (e.g., analytical costs).

4 EPA Regional cost estimates providing Field Sampling and Analysis costs for Summa canisters and labor were handled by assuming the Summa canister unit costs were the 

analytical costs, while the sampling unit costs were derived by dividing the labor costs by the overall number of samples collected.

5 Unless specified otherwise, analytical method used for indoor air, soil gas and sub-slab samples was assumed to be TO-15.

6 The same analytical methods and costs were often provided separately for ground water, soil gas, vapor intrusion, and indoor air media, as the costs were the same, so 

information was combined into one grouping.