[Federal Register Volume 76, Number 20 (Monday, January 31, 2011)]
[Pages 5370-5373]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-1934]



[EPA-HQ-SFUND-2010-1086; FRL-9260-1]

Potential Addition of Vapor Intrusion Component to the Hazard 
Ranking System

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of Opportunity for Public Input.


SUMMARY: The Environmental Protection Agency (``EPA'') is soliciting 
stakeholder input on whether to include a vapor intrusion component to 
the Hazard Ranking System (``HRS''). The HRS is the principal mechanism 
EPA uses to place sites on the Comprehensive Environmental Response, 
Compensation, and Liability Act (CERCLA) National Priorities List 
(NPL). This potential addition would allow the HRS to directly consider 
the human exposure to contaminants that enter building structures 
through the subsurface environment and thus, enabling sites with vapor 
intrusion contamination to be evaluated for placement on the NPL. EPA 
is accepting public feedback on specific topics related to the 
potential HRS revision (see SUPPLEMENTARY INFORMATION section of this 
Notice), and will consider information gathered during this comment 
period, as well as input from three public listening sessions before 
making a decision on whether to issue a proposed rulemaking to add a 
vapor intrusion component to the HRS. The Agency is requesting comments 
only regarding this potential addition to the HRS. The Agency is not 
considering changes to the remainder of the HRS.

DATES: Comments on the topics identified in the SUPPLEMENTARY 
INFORMATION section of this notice must be submitted (postmarked) on or 
before April 16, 2011.

ADDRESSES: Submit comments on the topics identified in the 
SUPPLEMENTARY INFORMATION section of this notice, identified by Docket 
ID No. EPA-HQ-SFUND-2010-1086, by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: [email protected].
     Fax: (202) 566-9744.
     Mail: U.S. Environmental Protection Agency; EPA Docket 
Center, Superfund Docket, Mail Code 28221T; 1200 Pennsylvania Avenue, 
NW., Washington, DC 20460.
     Hand Delivery: EPA Docket Center--Public Reading Room; EPA 
West Building, Room 3334; 1301 Constitution Avenue, NW., Washington, DC 
20004. Such deliveries are only accepted during the Docket's normal 
hours of operation, and special arrangements should be made for 
deliveries of boxed information.
     Listening Session: Oral and written comments on the topics 
in the SUPPLEMENTARY INFORMATION section of this Notice will be 
accepted at each of the three listening sessions. Follow the 
instructions provided on the listening session Web site at http://www.epa.gov/superfund/sites/npl/hrsaddition.htm for preparing written 
comments to be submitted at one of the listening sessions.
    Instructions: Direct comments on the topics identified in the 
SUPPLEMENTARY INFORMATION section of this notice to Docket ID No. EPA-
HQ-SFUND-2010-1086. EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at http://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through http://www.regulations.gov or [email protected]. Note that the http://www.regulations.gov Web site is an ``anonymous access'' system, which 
means EPA will not know your identity or contact information unless you 
provide it in the body of your comment.
    If you send an e-mail comment directly to EPA without going through 
http://www.regulations.gov, your e-mail address will be automatically 
captured and included as part of the comment that is placed in the 
public docket and made available on the Internet. If you submit an 
electronic comment, EPA recommends that you include your name and other 
contact information in the body of your comment and along with any disk 
or CD-ROM submitted. If EPA cannot read your comment due to technical 
difficulties and cannot contact you for clarification, EPA may not be 
able to consider your comment.
    Electronic files should avoid the use of special characters, any 
form of encryption, and be free of any defects or viruses. For 
additional information about EPA's public docket, visit the EPA Docket 
Center homepage at http://www.epa.gov/epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is

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not publicly available, e.g., CBI or other information whose disclosure 
is restricted by statute. Certain other material, such as copyrighted 
material, will be publicly available only in hard copy. Publicly 
available docket materials are available either electronically in 
http://www.regulations.gov or in hard copy at the EPA Docket Center--
Public Reading Room, EPA/DC, EPA West, Room 3334; 1301 Constitution 
Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The 
telephone number for the Public Reading Room is (202) 566-1744, and the 
telephone number for the Superfund docket is (202) 566-0276.

FOR FURTHER INFORMATION CONTACT: Terry Jeng, phone: (703) 603-8852, e-
mail: [email protected], Site Assessment and Remedy Decisions Branch, 
Assessment and Remediation Division, Office of Superfund Remediation 
and Technology Innovation (Mail Code 5204P), U.S. Environmental 
Protection Agency, 1200 Pennsylvania Avenue, NW., Washington, DC 20460.

SUPPLEMENTARY INFORMATION: EPA is considering adding a vapor intrusion 
component as a new mechanism to the HRS that would enable vapor 
intrusion contamination to be included in an HRS evaluation. Presented 
below is background information on the HRS, its statutory basis, and 
further detail regarding this potential addition and related topics on 
which EPA is requesting public comment.
    The Agency will conduct public outreach activities, including 
facilitating public listening sessions, providing public information 
documents, and establishing a Web site with more information regarding 
this potential addition to the HRS. The Agency will consider the 
information gathered from this Notice, listening sessions, and other 
sources before making a decision on whether to issue a proposed 
rulemaking to add subsurface contaminant intrusion to the HRS. The 
Agency is therefore requesting comments only regarding this potential 
addition to the HRS, and is not considering changes to the remainder of 
the HRS.
    EPA is currently scheduled to hold three listening sessions 
following publication of this Notice to allow interested parties to 
present feedback on the potential HRS addition. EPA welcomes the input 
that will be provided to the Agency by listening session participants. 
This input will be considered by the Agency as it determines the need 
for and nature of the addition to the HRS.
    For those stakeholders who cannot attend one of the listening 
sessions, comments on the topics described below in the Potential 
Addition of Vapor Intrusion Component to the HRS subsection of this 
Notice should be submitted in accordance with the instructions in the 
DATES and ADDRESSES sections of this Notice. Written comments will also 
be accepted at the listening sessions. Follow the instructions provided 
on the listening session Web site at http://www.epa.gov/superfund/sites/npl/hrsaddition.htm for preparing written comments to be 
submitted at one of the listening sessions; see also the ADDRESSES 
section of this Notice.
    In a separate effort, EPA is also preparing a final guidance 
document on vapor intrusion that will replace the 2002 Office of Solid 
Waste and Emergency Response (OSWER) Draft Guidance for Evaluating the 
Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils 
(Subsurface Vapor Intrusion Guidance). The guidance document is not 
directly related to the potential addition of a vapor intrusion 
component to the HRS and more information about this effort will be 
provided in a future Federal Register Notice. More information can be 
found on EPA's vapor intrusion Web site at http://www.epa.gov/oswer/vaporintrusion/.


Vapor Intrusion

    When hazardous substances, pollutants or contaminants are spilled 
on the ground or otherwise migrate to the subsurface, they can move in 
the subsurface environment and eventually enter buildings as a gas or 
vapor, or even as a liquid in some cases. Dry cleaning solvents and 
industrial de-greasers are products that contain hazardous substances 
that when released to the environment, can migrate into the soil and 
subsurface environment, enter buildings by seeping through cracks in 
basements, foundations, sewer lines and other openings and ultimately 
result in human exposures. Vapor intrusion is of particular concern 
because concentrations of vapors can rise to a point where the health 
of residents or workers in those buildings could be at risk. Intrusion 
of contaminants in a non-vapor state may also be a pathway of concern 
because of the potential for human exposure to the liquids, the 
resulting precipitates, or associated vapors.

Statutory Basis

    In 1980, Congress enacted the Comprehensive Environmental Response, 
Compensation, and Liability Act, 42 U.S.C. 9601, et seq. (``CERCLA or 
``the Act'') in response to the dangers posed by uncontrolled releases 
of hazardous substances, pollutants, or contaminants. Section 
105(a)(8)(A) of CERCLA required that the National Oil and Hazardous 
Substances Pollution Contingency Plan (NCP) include criteria for 
determining priorities among releases or threatened releases for the 
purpose of taking remedial or removal action. Criteria were to be based 
upon relative risk or danger, taking into account the population at 
risk, the hazardous potential of the substances at a facility, the 
potential for contamination of drinking water supplies, direct human 
contact, destruction of sensitive ecosystems, and other appropriate 
factors. Section 105(a)(8)(B) of CERCLA requires that the statutory 
criteria described in section 105(a)(8)(A) be used to prepare a list of 
national priorities among the known releases, or threatened releases 
throughout the United States, and that at least 400 sites be designated 
for priority. The list, which is Appendix B of the NCP, is the National 
Priorities List (NPL).
    To implement CERCLA, EPA promulgated the revised NCP, 40 CFR Part 
300, on July 16, 1982 (47 FR 31180) pursuant to section 105 of CERCLA 
and Executive Order 12316 (48 FR 42237 August 20, 1981). The NCP, 
further revised by EPA on September 16, 1985 (50 FR 37624) and November 
20, 1985 (50 FR 47912), sets forth the guidelines and procedures needed 
to respond to releases and threatened releases of hazardous substances, 
pollutants, or contaminants under CERCLA. The Agency developed the 
Hazard Ranking System (``HRS'') to implement Section 105(a)(8)(A). The 
HRS was codified as Appendix A of the NCP. The HRS is the primary 
mechanism EPA uses to evaluate a site for placement on the NPL.
    CERCLA was amended by the Superfund Amendments and Reauthorization 
Act (SARA) in 1986. This amendment required the HRS to be revised to 
more accurately assess the relative degree of risk to human health and 
the environment posed by sites and facilities subject to review. 
Revisions to the HRS were proposed in 1988 (53 FR 51962) and 
promulgated in 1990 (55 FR 51532). The revisions changed the way EPA 
evaluates potential threats to human health and the environment from 
hazardous waste sites, as well as

[[Page 5372]]

made the HRS more accurate in assessing relative risk. The revisions 
included the addition of the human food chain and recreation threats to 
the surface water pathway and the addition of a new exposure pathway 
(i.e., soil exposure pathway). CERCLA called for the establishment of 
both the NPL and the HRS.

National Priorities List

    CERCLA established in Appendix B of the NCP, the NPL, which is also 
commonly known as the Superfund List. The NPL is a list of contaminated 
sites identified to have known releases or threatened releases of 
hazardous substances, pollutants, or contaminants throughout the United 
States and its territories. The NPL is intended primarily to guide EPA 
in determining which sites warrant further investigation. A site can be 
placed on the NPL via three methods (see 40 CFR 300.425(c) of the NCP 
for further information):
     Achieving a score of 28.50 or greater under the HRS;
     Designating by a State or Territory as its top priority 
for listing on the NPL (regardless of its HRS score); or
     Using the Agency for Toxic Substances and Disease Registry 
(ATSDR) listing mechanism (see 40 CFR.300.66(b)(4) of the NCP for 
further information).

Rationale for Adding Vapor Intrusion to the Hazard Ranking System

    In a May 2010 report (EPA's Estimated Costs to Remediate Existing 
Sites Exceed Current Funding Levels, and More Sites are Expected to Be 
Added to the National Priorities List, GAO Report to Congressional 
Requesters, GAO-10-380, May 2010), the Government Accountability Office 
(GAO) concluded that if vapor intrusion sites are not assessed and, if 
needed, listed on the NPL, there is the potential that contaminated 
sites with unacceptable human exposure will not be acted upon. GAO 
recommended that the EPA Administrator determine the extent to which 
EPA will consider vapor intrusion in listing NPL sites and how this 
will affect the number of NPL sites listed in the future.
    Many sites on the NPL that have subsurface contaminant intrusion 
problems were placed on the NPL by evaluation of pathways other than a 
contaminant intrusion pathway. There are other contaminated sites, 
however, that did not qualify for placement on the NPL under the 
current HRS. However, these sites may qualify for placement on the NPL 
if the threat from vapor intrusion was included in the HRS. A new HRS 
mechanism would enable EPA to identify situations in which individuals 
are exposed or potentially exposed to vapor or other contaminant 
intrusion in dwellings, work places, or other structures or enclosures.

Hazard Ranking System

    The HRS is a screening tool used by EPA to assess the relative 
threat that sites with actual or potential contaminant releases pose to 
human health or the environment. The HRS is the primary mechanism EPA 
uses to place a site on the NPL. (As noted earlier, there are two other 
mechanisms that can be used to place sites on the NPL.) The sites on 
the NPL are then further investigated to determine the extent of the 
threat and whether cleanup of the site under EPA's Superfund Remedial 
program is warranted. The HRS is a numerically based screening system 
that uses information from initial, limited investigations that can be 
collected relatively quickly and inexpensively, thus allowing most 
Superfund resources to be directed to remedial actions at sites on the 
NPL. The HRS does not provide a risk assessment of a specific site, but 
serves as a screening level indicator of the highest priority hazardous 
releases or potential releases.
    The HRS score is currently based on an evaluation of up to four 
separate pathways: ground water migration, soil exposure, surface water 
migration, and air migration. Pathways are routes by which exposure to 
contaminant releases by human or sensitive environments can occur.
    1. The ground water migration pathway evaluates the likelihood that 
hazardous substances will travel through the ground below and 
contaminate aquifers and drinking water wells that draw on those 
aquifers. The groundwater pathway does not consider the potential risk 
of exposure to vapor intrusion from contaminated 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 drinking 
water, the human food chain (i.e., contaminants build up in the aquatic 
organisms that humans in turn consume), and sensitive environments.
    3. The soil exposure pathway evaluates the potential threats to 
humans and terrestrial environments posed by direct, physical contact 
with hazardous substances or contaminated soil. This pathway includes 
threats to those living on property with hazardous substances or soils 
contaminated with hazardous substances, and those living nearby with 
access to the property.
    4. Finally, the air migration pathway evaluates the likelihood of 
release of hazardous substances into the atmosphere and how many people 
and sensitive environments could be exposed to hazardous substances 
carried in the air, including gases and particulates. The air migration 
pathway does not consider indoor air contamination.
    The scoring system for each pathway is based on a number of 
individual factors associated with risk-related conditions at the site. 
These factors are grouped into three categories:
    1. Likelihood of exposure (i.e., likelihood that a site has 
released or has the potential to release hazardous substances into the 
    2. Waste characteristics (i.e., inherent toxicity, mobility of the 
substances and the quantity of the hazardous substances that has been 
    3. Targets (i.e., people or sensitive environments actually or 
potentially exposed to the release).
    The HRS site score, which ranges from 0 to 100, is obtained by 
combining the pathway scores. A site may be scored for one or more of 
the pathways depending on the nature of the release. Any site scoring 
28.50 or greater is eligible for placement on the NPL. As noted 
previously, the HRS score does not represent a specified level of risk, 
but is a cutoff point that serves as a screening-level indicator of the 
highest priority hazardous releases or potential releases based on the 
criteria identified in SARA.

Potential Addition of Vapor Intrusion Component to the HRS

    Consistent with CERCLA Section 105 and SARA, the Agency regards it 
appropriate to consider amending or adding to the HRS when such 
amendments would identify sites of the highest priority for evaluation. 
EPA is considering the potential enhancement of the HRS by including a 
vapor intrusion component that address issues related to the intrusion 
of hazardous substances, pollutants, and contaminants into structures 
(e.g., homes, offices, schools, manufacturing facilities). To 
comprehensively explore, and if determined appropriate, identify 
approaches for adding the threat posed by contaminant vapor intrusion 
into occupied structures to the HRS, EPA is beginning the process of 
soliciting stakeholder input. To determine whether to move forward with 
this addition, and if so, to determine a range of potential approaches, 
EPA is

[[Page 5373]]

soliciting input on the topics described below.
    1. The level and extent of vapor intrusion contamination that would 
warrant evaluation for placement on the NPL, as well as the 
identification of screening level information sufficient to perform 
this evaluation.
    2. Methods for incorporating vapor intrusion into the HRS while, to 
the extent possible, maintaining the structure of the other pathways in 
the current HRS and retaining that same structure throughout the new 
mechanism for vapor intrusion (i.e., likelihood of release, waste 
characteristics, and targets). These methods could include the addition 
of vapor intrusion as a migration pathway (e.g., groundwater), or part 
of an exposure pathway (e.g., threat within a direct exposure pathway 
along with soil).
    3. Consideration of the importance of evaluating the potential 
threat to populations not demonstrated to be exposed to contaminant 
    4. The identification of sampling procedures available and 
practical to detect the presence of contamination due to vapor 
    5. The availability of screening sampling strategies that can 
adequately compensate for the variability in vapor intrusion rates 
under different climatic and seasonal conditions.
    6. Identification of analytical methods that are sufficiently 
precise and accurate to demonstrate a significant increase in 
contaminant levels from vapor intrusion.
    7. The importance of the threat posed by exposure to contaminant 
vapor intrusion via inhalation, dermal contact with the vapors or 
condensate on surfaces, and ingestion.
    8. The identification of what environmental factors (e.g., porosity 
of soil, presence of a contaminated aquifer, climate) and structural 
and lifestyle factors (e.g., houses with basements) should 
appropriately be considered in determining whether a site warrants 
sampling for contaminant vapor intrusion.
    9. In addition to residences, schools and other occupied 
structures, the identification of structures in which contaminant vapor 
intrusion could result in a significant threat to human health (e.g., 
community recreation centers, cultural centers, museums, athletic 
    10. The possible need to consider not only contaminant vapor 
intrusion, but also intrusion of contaminants in solid (i.e., 
particulates) and liquid forms.
    In addition to these topics, EPA also solicits input on community 
outreach methods that would be most effective in gathering and 
disseminating information regarding this potential addition to the HRS. 
To further support this effort, EPA requests public input on the 
identification of possible vapor intrusion sites. This information will 
be used for informational purposes only.
    EPA will consider all public input when evaluating whether changes 
to the HRS are appropriate, and whether to issue a proposed amendment 
to the HRS.

Listening Sessions

    The first listening session will be held in Arlington, VA on 
February 24, 2011. Specific details of the listening sessions, 
including dates and locations for the other two sessions, and 
instructions for those wishing to present oral comments will be posted 
at: http://www.epa.gov/superfund/sites/npl/hrsaddition.htm. At this 
site, users will also be able to sign up for a mailing list that will 
be used to distribute logistical information on these listening 
sessions. Registration is not required to attend a listening session 
with the following exceptions.
    Due to space limitations, parties interested in presenting oral 
comments at the Arlington, VA listening session only, must register for 
that session. Registration must be completed at least 3 calendar days 
prior to the session. Details for registration will be posted on the 
Web at http://www.epa.gov/superfund/sites/npl/hrsaddition.htm. If no 
speakers have registered by 2 calendar days prior to this listening 
session, it will be cancelled and EPA will notify those registered of 
the cancellation. The Agency will also post on its Web site that the 
listening session has been cancelled.
    In addition to attending in person, participation in the Arlington, 
VA listening session will be available via a teleconference. Those 
wishing to attend via teleconference must register as described above. 
EPA will provide the teleconference information to registrants via e-
mail notification in advance of the session.
    The Arlington, VA listening session will be held at EPA's Potomac 
Yard office located at: 2777 Crystal Drive, Arlington, VA 22202. The 
listening session will begin at 9 a.m. and end at 5 p.m. The Arlington, 
VA listening session may be webcast. Please refer to the Superfund 
``Addition of Vapor Intrusion to HRS'' Web Site, http://www.epa.gov/superfund/sites/npl/hrsaddition.htm for information on how to access 
the webcast. Please note that the webcast is a supplementary public 
process provided only for convenience. If difficulties arise resulting 
in webcasting outages, the meeting will continue as planned.
    In general, each oral comment at listening sessions should be 
limited to no more than 15 minutes in length. If, however, there are 
more individuals who wish to present comments than the allotted time 
for the listening session allows, an announcement will be made at the 
beginning of the listening session that the time limit has been 
adjusted to allow for the presentation of more comments.

    Dated: January 25, 2011.
Mathy Stanislaus,
Assistant Administrator, Office of Solid Waste and Emergency Response.
[FR Doc. 2011-1934 Filed 1-28-11; 8:45 am]