the HRS and EPA is proposing that this remains consistent in the
subsurface intrusion component. Furthermore, because intrusion by
contaminated ground water is documented by direct observation only,
targets residing within a structure subject to intrusion by
contaminated ground water are also proposed to be evaluated as Level II
(see section 2.5 of the proposed HRS addition).
    The targets within an ASC are also further divided based on the
type of sample (e.g., gas, soil, water) and the distance of the sample
from the targets (e.g., the depth of the sample below the structure).
Weighting factors ranging from 0.1 to 0.9 are then assigned accordingly
as discussed below in section 5.c.ii. See also section III.H. of the
preamble to the current HRS (55 FR 51547, December 14, 1990) for
supplemental information.
ii. Exposed Individual--See Section <IP_ADDRESS>.1 of the Proposed HRS
Addition
    The standard HRS approach for scoring targets includes a measure
reflecting the maximum level of exposure to individuals. The evaluation
of exposed individuals is proposed to include individuals living,
attending school or day care, or working in a regularly occupied
structure. The reasonably maximally exposed individuals are those
individuals in the eligible target population that are expected to be
exposed to the highest concentration of the hazardous substance in
question for a significant time. See section V.C.9 of the preamble to
the proposed 1988 HRS (53 FR 51978, December 28, 1988) for supplemental
information.
    EPA is proposing to retain the basic scoring approach used
throughout the current HRS for evaluating the exposed individual
factor. As is consistent with all pathways, a value of 50 points is
assigned if there is any individual exposed to Level I concentrations
or 45 points if there is any individual exposed to Level II
concentrations. If there are no individuals exposed to Level I or Level
II concentrations, but at least one individual is living, attending
school or day care, or working in a regularly occupied structure within
an ASC, EPA proposes to assign a value of 20. See section 2.5 of the
current HRS for supplemental information as to how EPA addresses
exposed individuals within the HRS structure.
c. Population--See Section <IP_ADDRESS>.2 of the Proposed HRS Addition
    The population factor is evaluated using media-specific, health-
based benchmarks as discussed above. EPA proposes the population factor
include all populations qualifying as exposed individuals, including
residents, students, workers and those attending day care. However,
workers are weighted slightly differently than other exposed
individuals to reflect that a worker's exposure is limited to the time
present in a workplace. Additionally, as workers may be employed on a
full-time or part-time basis, the number of workers present in a
structure or subunit is proposed to be adjusted by an appropriate
factor reflecting this difference in exposure durations. EPA is
proposing to retain the current scoring methodology for weighting
populations used throughout the HRS, with actual exposure more heavily
weighted than those potentially exposed. The proposed subsurface
intrusion component will evaluate populations based on the number of
individuals located within an identified AOE (i.e., those populations
exposed to Level I and Level II concentrations) and the number of
individuals located within an ASC (i.e., potential contamination as
determined based on subsurface sampling), which is further subdivided
as described in subsection ii below.
i. Weighting of Targets in the Area of Observed Exposure (AOE)--See
Sections <IP_ADDRESS>.2.1 and <IP_ADDRESS>.2.2 of the Proposed HRS Addition
    EPA is proposing to establish an AOE based on documented
contamination meeting observed exposure criteria (either by direct
observation or chemical analysis). Consistent with the weighting of
populations throughout the HRS (see section 2.5 of the current HRS),
the proposed subsurface intrusion component will weight targets subject
to Level I contaminant concentrations by a factor of 10 and weight
targets subject to Level II contaminant concentrations by a factor of
1. As noted previously, eligible populations also include individuals
working in regularly occupied structures. However, the number of
workers present in a regularly occupied structure will be adjusted to
reflect that their exposure is limited to the time they are in a
workplace. Therefore, the number of full- and part-time workers in a
structure or subunit will be identified and divided by an appropriate
factor prior to being summed with the number of other individuals
present. If information is unavailable to classify a worker as full- or
part-time, that worker will be evaluated as full-time.
    For example, if a single residence occupied by a family of four was
observed to be exposed to hazardous substance concentrations above a
media-specific, health-based benchmark, the number of residents would
be multiplied by 10 for a factor value of 40. However, if that same
family was exposed to a hazardous substance and the hazardous substance
concentration was below the applicable benchmark but met the criteria
for observed exposure, the number of residents would be multiplied by 1
for a factor value of 4. To ensure the entire population within an AOE
is included in the HRS evaluation, both Level I and Level II factor
values are counted and summed together.
    Within the AOE, EPA is proposing to consider as actually
contaminated those populations in regularly occupied structures for
which observed exposures have not been established but the structures
are surrounded by regularly occupied structures in which observed
exposures have been identified, unless evidence indicates otherwise.
This action is proposed because it is considered likely that if these
structures were sampled during the correct conditions, observed
exposures would be identified at levels similar to those in surrounding
structures. Targets inferred to be exposed to this contamination will
be weighted as Level II as there are no actual sample results to
compare against benchmarks. However, EPA has included an exception to
allow for situations where site-specific conditions clearly document
that there may be no observed exposures in these structures. The rule
language states that targets can be inferred to have observed exposures
in these situations ``unless available information indicates
otherwise''. This concept of inferred exposure is also included in the
existing soil exposure pathway and in the air migration pathway.
    In the case of multi-story/multi-subunit structures, all regularly
occupied subunits on a level with an observed exposure and all levels
below are considered to be within an AOE, unless available information
indicates otherwise. For multi-story/multi-subunit structures located
within an AOE, but where an observed exposure has not been documented,
only those

regularly occupied spaces on the lowest level are considered to be
within an AOE, unless available information indicates otherwise. (See
sections 5.0.1 and 6.3 of the current HRS.)
ii. Weighting of Targets in the Area of Subsurface Contamination
(ASC)--See Section <IP_ADDRESS>.2.3 of the Proposed HRS Addition
    EPA is proposing to establish an ASC as defined by documented
ground water, subslab, soil, semi-enclosed or enclosed crawl space, or
soil gas contamination meeting observed release criteria. These areas
are included in the subsurface intrusion component due to the potential
that limited sampling conducted during a site inspection may not
identify that subsurface intrusion is occurring because of the high
temporal and spatial variability associated with detecting subsurface
intrusion. Temporal and spatial differences can significantly impact
the rate at which volatile hazardous substances enter a structure.
However, when an ASC has been defined, that area represents a location
where subsurface hazardous substances have the potential to intrude
into a structure. EPA is limited in its extent of preliminary screening
activities, and a single indoor air sampling event is unlikely to
identify the full threat posed by subsurface intrusion.
    As is consistent with the 1990 HRS, EPA is proposing to weight
these potentially exposed targets at a value less than those targets
that have been identified to be actually exposed. Due to the
variability in subsurface intrusion rates, the potential weighting
factor values for targets within an ASC range from 0.1 to 0.9 and
depend on where the subsurface contamination has been found. Using
EPA's vapor intrusion attenuation factors published in 2012 and basic
subsurface contaminant transport concepts, EPA developed a relatively
proportional weighting for potential targets based on the sampling
media being considered. This range of weighting factors represents the
proportional probability of a target to be exposed as a result of
contaminant intrusion from the subsurface in a variety of likely
sampling scenarios. The potential target weighting factors presented in
the proposed addition do not directly correspond to attenuation factors
in themselves. Instead, the relative weighting between these values is
based on the published attenuation factors. These weighting factors are
presented in this manner to project that contaminants found in a crawl
space sample, for example, are more likely to attenuate less before
entering into an overlying structure, and thus more likely to pose a
threat, as opposed to those found in a shallow ground water sample.
    EPA is proposing that the weighting of potential targets also
reflect the distance to or the depth at which contamination is found.
For any contamination found at a horizontal or vertical distance of
five feet or less from a regularly occupied structure's foundation, EPA
is proposing to assign a minimum weighting factor of 0.4 regardless of
the sample medium. Similarly, EPA is proposing to assign a weighing
factor of 0.1 to any contamination found or inferred at depths greater
than 30 feet regardless of sampling medium. These minimum weighting
values are in response to an analysis of the data used in deriving
published attenuation values. The attenuation values were published
based on real-world sampling data collected from numerous sites across
the United States. The majority of sampling data collected as part of
this effort came from sites where contamination was generally found at
depths less than 30 feet. Therefore, EPA considers the attenuation
factors and relative weightings between them to only be appropriate for
shallower depths. The minimum value for the upper five feet allows
consideration of sites where contamination is found at extremely
shallow depths and therefore has a minimal vertical distance to travel
before intruding into a regularly occupied structure.
    In the case of multi-story/multi-subunit structures, all regularly
occupied subunits on a level above one where an observed exposure has
been documented or inferred, or where a gaseous indoor air sample
meeting observed release criteria is present, are considered to be
located within an ASC, unless available information indicates
otherwise. For multi-story/multi-subunit structures located only within
an ASC, only those regularly occupied subunits within the lowest level
are considered in an HRS evaluation.
    EPA proposes eligible populations include individuals living in, or
attending school or day care in the structure, and workers in regularly
occupied structures. The number of workers is adjusted to reflect that
their exposure is limited to the time they are in a workplace.
Therefore, the number of full- and part-time workers in a structure or
subunit will be divided by an appropriate factor prior to being summed
with the number of other individuals present. If information is
unavailable to classify a worker as full- or part-time, that worker
will be evaluated as full-time.
    The proposed weighting factors for exposed individuals in any
structure within an ASC are based on the probability of contamination
entering into occupied structures from the subsurface. The weighting
factors reflect depth to contamination, sample type, and media. The
magnitude of the factor is also based on attenuation factors from
current scientific literature including EPA's 2012 vapor intrusion
attenuation factors publication. Additional information regarding this
analysis is presented in section 6.0 of the Proposal TSD.
d. Resources--See Section <IP_ADDRESS>.3 of the Proposed HRS Addition
    The resources target factor is evaluated in all pathways under the
current HRS. A factor value of five is assigned if at least one
resource is present and a factor value of zero if no resource is
present. Eligible resources are pathway-, component-, or threat-
specific. These resources represent uses of a contaminated medium or
area where exposures occur and are not covered by the other identified
targets. For example, resources within the air migration pathway
include commercial agriculture or silviculture and major/designated
recreation areas. The resident population threat also includes
commercial livestock production or grazing. See section III.I of the
preamble to the current HRS (55 FR 51549, December 14, 1990) for
supplemental information.
    Because subsurface intrusion is limited to indoor spaces, EPA is
proposing to include regularly occupied structures that are located
within a defined AOE or ASC (as previously discussed in section VI.B.2
of this preamble) and in which populations, not including those already
counted as exposed individuals, may be exposed to contamination due to
subsurface intrusion. For example, libraries, recreational facilities,
and religious or tribal structures used by individuals, may qualify as
eligible resources.
e. Calculation of the Targets Factor Category Value--See Section
<IP_ADDRESS>.4 of the Proposed HRS Addition
    As is done throughout the HRS, EPA is proposing to sum all of the
target factor values together to establish a target factor category
value in calculating the proposed subsurface intrusion component score.
Unlike the likelihood of exposure and waste characteristics factor
category values in all HRS pathways, which are subject to maximum
values, the target factor

category is not limited in the current HRS. This is to ensure that all
individuals, populations, resources, and sensitive environments are
included; thereby, representing the full relative risk associated with
the identified threat. It is also consistent with the direction of
CERCLA section 105 to amend the HRS ``to the maximum extent feasible''
to address ``the relative degree of risk to human health and the
environment'' by putting the emphasis on the number of receptors
exposed to contamination.
6. Calculation and Incorporation of the SsI Component Score Into the
HRS Site Score
    The following subsections summarize the calculation of the
subsurface intrusion component score, how the component score is then
used in the calculation of the soil exposure and subsurface intrusion
pathway score, and how, in turn, the pathway score is subsequently
incorporated into the HRS site score.
a. Calculation of the SsI Component Score--See Section 5.2.2 of the
Proposed HRS Addition
    EPA is proposing to calculate the subsurface intrusion component
score using the same algorithm as in other components and pathways of
the HRS. (See section 2.2 of the 1988 Revised HRS TSD.) This involves
multiplying the likelihood of exposure factor category value times the
waste characteristics factor category value times the targets factor
category value and dividing that value by a weighting factor so that it
has equal magnitude to other component scores (subject to a maximum
value). The values are multiplied to reflect that it is the product of
these values that represents a relative risk level.
    In a relative risk (or in a site-specific risk) assessment, the use
of the product of the factor category values is considered appropriate
because the magnitude of each of the factor category values reflects
the probability of exposure occurring: Likelihood of releases reflects
the probability of exposure actually occurring, waste characteristics
reflects the probable quantity and duration of the exposure, and
targets reflect the probable number of receptors at risk. Thus, since
each factor category value reflects a probability in a series of
events, the overall probability associated with the series is the
product of the individual probabilities. For example, if any factor
category value is zero, such as when there are no targets exposed or
potentially exposed to subsurface intrusion, the component score is
zero, consistent with there being no risk due to subsurface intrusion.
b. Incorporation of the SsI Component Score Into the Soil Exposure and
Subsurface Intrusion Pathway Score--See Section 5.3 of the Proposed HRS
Addition
    The score for this restructured pathway is proposed to be a
combination of two component scores. The subsurface intrusion component
score is added to the soil exposure component score (subject to a
maximum value) to determine the pathway score. The two component scores
are proposed to be additive because the populations may be subjected to
exposures separately via both routes: The soil exposure component
reflects exposures to people when outside a structure and focuses on
ingestion, while the subsurface intrusion component reflects exposures
to people when inside a structure and focuses on inhalation. Hence, the
addition of the two component scores reflects the cumulative potential
risk and is not double counting the relative risk.
    In addition, a pathway score can be assigned without scoring both
the soil exposure and subsurface intrusion components using this
approach. It is possible for a site to have only one component
evaluated and still reach the same pathway score as under the current
HRS. It should be observed that because the scoring of the soil
exposure component is not being altered, the soil exposure component
would contribute the same score to the overall site score as it would
if the subsurface intrusion component is not added.
c. Incorporation of the Soil Exposure and Subsurface Intrusion Pathway
Score Into a Site Score--See Section 2.1.1 of the Proposed HRS Addition
    EPA is not proposing any changes to the methodology used to assign
an overall site score due to the addition of the subsurface intrusion
component to the soil exposure pathway and renaming that pathway the
soil exposure and subsurface intrusion pathway. The overall site score
remains a function of four pathway scores and the same weighting is
given to each pathway score as in the current HRS. See section 2.2 of
the 1988 Revised HRS TSD for supplemental information on why the
existing methodology was chosen.
7. Example Site Scoring Scenarios
    To evaluate the proposed subsurface intrusion component and factor
category weighting, EPA developed three conceptual site scenarios: One
that would not qualify for the NPL (score below 28.50); one that would
qualify marginally for the NPL (score of about 28.50); and one that
should clearly qualify for the NPL (site score considerably above
28.50).
    The first scenario consists of a ground water plume contaminated
with a hazardous substance with moderate toxicity that underlies
approximately 3 acres of a residential neighborhood comprised of
single-family detached homes. Indoor air samples have been collected
from inside two homes and have reported hazardous substance
concentrations above background, but below the applicable benchmarks.
Additionally, several other occupied structures were sampled for indoor
air and subslab contaminant concentrations; however, no other
detections of hazardous substances were observed. This site would not
qualify for the NPL based on available information (i.e., score below
28.50).
    The second scenario also consists of a ground water plume
contaminated with a hazardous substance with moderate toxicity as in
the first scenario, but it has a considerably larger plume and more
targets. The ground water plume underlies approximately 20 acres of a
residential neighborhood and commercial area comprised of single-family
detached homes, a daycare facility, and a single-story office building.
Indoor air samples collected inside 19 homes, the daycare facility, and
office building have hazardous substance concentrations above the
applicable benchmark. Indoor air samples in 5 homes, the daycare
facility with approximately 25 children enrolled and 6 full-time and 2
part-time workers, and the office building with 18 full-time workers
have hazardous substance concentrations above background, but below the
applicable benchmark. The homes and daycare facility were checked for
indoor sources of hazardous substances prior to sampling and such
sources were removed if found. This site would likely qualify for the
NPL based on available information (i.e., score of about 28.50).
    The third scenario consists of a ground water plume contaminated
with a highly toxic hazardous substance and a larger number of targets
than the second scenario. The plume underlies approximately 25 acres of
a residential neighborhood and hazardous substance concentrations above
a benchmark were detected in indoor air samples from 25 homes and one
daycare with approximately 25 children enrolled and 5 full-time
workers. Hazardous substance concentrations above background but below
benchmarks were

detected within 15 homes. The homes and daycare facility were checked
for indoor sources of hazardous substances prior to sampling and such
sources were removed if found. Based on available information, this
site would qualify for the NPL and would likely achieve the maximum HRS
score for a single component and pathway (i.e., 50.00).
    Further evaluation of the varying factor values and resulting HRS
site scores, along with further discussion of these three scenarios is
presented in section 8.1.c of the Proposal TSD.

VII. Summary of Proposed Updates to the HRS (Sections 2, 5, 6, and 7)

A. Addition of an SsI Component to the HRS (Sections 2, 5, and 7)

1. Chapter 5
    The proposed addition of a subsurface intrusion component is
proposed to be added to the existing Soil Exposure pathway as section
5.2 in Chapter 5 to the current HRS. The new pathway name is proposed
as the Soil Exposure and Subsurface Intrusion Pathway. The existing
method for evaluating the soil exposure threat will remain unchanged.
2. Chapter 2
    Evaluations Common to All Pathways is proposed to be updated to
reflect the addition of the subsurface intrusion component to the
existing soil exposure pathway. The evaluations for the current four
pathways remain unchanged and a comparable evaluation will be added for
the subsurface intrusion component.
3. Chapter 7
    Sites Containing Radioactive Substances currently reflects how
radioactive substances are evaluated in the context of the four current
HRS pathways. Updates will be made to reflect how radioactive
substances are evaluated using the proposed subsurface intrusion
component.

B. Terminology Updates Affecting Specific Sections of the HRS (Sections
2, 5 and 6)

    During the development of this proposed addition to the HRS, the
agency determined that the following terms should be updated to reflect
current terminology and procedures used by EPA in performing risk
assessments.
1. Ambient Water Quality Criteria
    Ambient Water Quality Criteria (AWQC) are now identified also as
National Recommended Water Quality Criteria (NRWQC). In addition, the
acute AWQC are now identified as the Criterion Maximum Concentration
(CMC) and the chronic criteria are referred to as the Criterion
Continuous Concentration (CCC). (See section 1.1 of the proposed HRS
addition.) These criteria are used to determine the level of threat to
environmental targets.
2. Reference Concentrations
    For inhalation exposures, EPA is adopting the use of Reference
Concentrations (RfCs) instead of Reference Doses (RfDs) when
determining non-cancer related risk levels. RfCs are used in
determining the level of threat to human targets due to possible
inhalation and when determining the toxicity of the substances.
3. Cancer Unit Risk
    For inhalation exposures, EPA is adopting the use of Inhalation
Unit Risk (IUR) instead of cancer slope factors in determining cancer-
related risk levels. IURs are used in determining the level of threat
to human targets due to possible inhalation and when determining the
toxicity of the substances.
4. Weight-of-Evidence Groupings
    The 2005 EPA weight-of-evidence groupings supporting the
designation of a substance as a human carcinogen have been incorporated
into the HRS algorithm for determining the toxicity factor value. (The
former EPA weight-of-evidence categories included as part of the 1990
HRS have been retained as EPA has not yet completed assigning all
substances to the revised categories and are doing so at the time the
EPA substance literature reviews are updated.)

VIII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders
can be found at http://www2.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB) for review. This action
may raise novel legal or policy issues arising out of legal mandates,
the President's priorities, or the principles set forth in the EO. Any
changes made in response to OMB recommendations have been documented in
the docket.
    EPA prepared an analysis of the potential costs and benefits
associated with this action. This analysis, Addition of a Subsurface
Intrusion (SsI) Component to the Hazard Ranking System (HRS):
Regulatory Impact Analysis is available in the docket for this action.

B. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden
under the PRA. OMB has previously approved the information collection
activities contained in the existing regulations and has assigned OMB
control number 2050-0095.
    This proposed regulatory change will only affect how EPA and
organizations performing work on behalf of EPA (state or tribal
partners) conduct site assessments and HRS scoring at sites where
certain environmental conditions exist. This proposed regulatory change
will result in data collection at these types of sites to allow
evaluation under the HRS. EPA expects that the total number of site
assessments performed and the number of sites added to the NPL per year
will not increase, but rather expects that there will be a realignment
and reprioritization of its internal resources and state cooperative
agreement funding.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. This
action will not impose any requirements on 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. This addition to the HRS would
not impose direct impacts on any other entities. For additional
discussion on this subject see section 4.9 of the Regulatory Impact
Analysis (see the docket for this action).

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect
small governments. The action imposes no enforceable duty on any state,
local, or tribal governments or the private sector.

E. 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.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This action does not have tribal implications, as specified in
Executive Order 13175. EPA's evaluation of a site using the HRS does
not impose any costs on a tribe (except those already in a cooperative
agreement relationship with EPA). Thus, Executive Order 13175 does not
apply to this action.
    Although Executive Order 13175 does not apply to this action, EPA
consulted with tribal officials through meetings and 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 (76 FR 5370), and
public listening sessions regarding the decision to proceed with the
development of this action. All tribal comments indicated support for
this action.
    EPA specifically solicits additional comment on this proposed
action from tribal officials.

G. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that EPA has reason to believe may disproportionately affect children,
per the definition of ``covered regulatory action'' in section 2-202 of
the Executive Order. This action is not subject to Executive Order
13045 because it does not concern an environmental health risk or
safety risk.

H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use

    This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution, or use of energy. The site assessment activities affected
by this rule are limited in scope and number and rely on existing
energy distribution systems. Further, we have concluded that this
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, that would significantly affect
energy supply, distribution, or usage. Thus, Executive Order 13211 does
not apply to this action.

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    EPA believes the human health or environmental risk addressed by
this action will not have potential disproportionately high and adverse
human health or environmental effects on minority, low-income or
indigenous populations. The results of this evaluation are contained in
section III.C.4 of this preamble and section 4.3 (and all subsections)
and Appendix C of the Regulatory Impact Analysis for this proposed
rulemaking. A copy of the Addition of a Subsurface Intrusion (SsI)
Component to the Hazard Ranking System (HRS): Regulatory Impact
Analysis is available in the docket for this action.

K. Executive Order 12580: Superfund Implementation

    Executive Order 12580, section 1(d), states that revisions to the
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 (FEMA) and the Nuclear Regulatory Commission (NRC) 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 to the extent
that it is related to the addition of a new component to the HRS,
through consultation with members of the NRT.

List of Subjects in 40 CFR Part 300

    Environmental protection, Air pollution control, Chemicals,
Hazardous substances, Hazardous waste, Intergovernmental relations,
Natural resources, Oil pollution, Penalties, Reporting and
recordkeeping requirements, Superfund, Water pollution control, Water
supply.

    Dated: February 3, 2016.
Gina McCarthy,
Administrator.
    For the reasons set out in the preamble, Title 40, Chapter 1 of the
Code of Federal Regulations is proposed to be amended as follows:

PART 300--NATIONAL OIL AND HAZARDOUS SUBSTANCES POLLUTION
CONTINGENCY PLAN

0
1. The authority citation for part 300 continues to read as follows:

    Authority:  33 U.S.C. 1251 et seq.

0
2. Amend Appendix A to Part 300:
0
a. In section 1.1 by:
0
i. Amending by removing the definition heading ``Ambient Water Quality
Criteria (AWQC) and adding ``Ambient Water Quality Criteria (AWQC)/
National Recommended Water Quality Criteria'', in its place; and
removing the text ``maximum acute or chronic toxicity'' and adding
``maximum acute (Criteria Maximum Concentration or CMC) or chronic
(Criterion Continuous Concentration or CCC) toxicity.'' in its place;
0
ii. Adding in alphabetical order the definitions ``Channelized flow''
and ``Crawl space'';
0
iii. Revising the definitions ``Distance weight'' and ``Half-life'';
0
iv. Amending the definition ``HRS pathway'' by removing the word
``soil,'' and adding ``soil exposure and subsurface intrusion,'' in its
place;
0
v. Adding in alphabetical order the definitions ``Indoor air'',
``Inhalation Unit Risk (IUR)'', ``Occupied structures'', ``Preferential
subsurface intrusion pathways''; and ``Reference concentration (RfC)'';
0
vi. Revising the definition ``Reference dose (RfD)''; ``Screening
concentration'', and ``Slope factor (also referred to as cancer potency
factor)'';
0
vii. Adding in alphabetical order the definitions ``Soil gas'', ``Soil
porosity''; ``Subslab'', ``Subsurface Intrusion'', ``Surficial ground
water'', ``Unit Risk'', and ``Unsaturated Zone''; and
0
viii. Revising the introductory text of the definition ``Weight-of-
evidence''.
0
b. Revising section 2.0 to include sections 2.0 through 2.5.2;
0
c. Revising section 5.0 to include sections 5.0 through 5.3;
0
d. In section 6.0 by revising Table 6-14, entitled ``Health-Based
Benchmarks for Hazardous Substances in Air''; and
0
e. In section 7.0 by:
0
i. Revising the table entitled ``Table 7-1. HRS Factors Evaluated
Differently For Radionuclides'';
0
ii. Under Table 7-1, the second undesignated paragraph, revising the
third sentence ;
0
iii. Revising sections 7.1, 7.1.1, and 7.1.2; 7.2.3; 7.2.4; <IP_ADDRESS>,
<IP_ADDRESS>.1 through <IP_ADDRESS>.3; <IP_ADDRESS>; <IP_ADDRESS>; 7.3, 7.3.1, and 7.3.2;
and
0
iv. Adding section 7.3.3.
    The revisions and additions read as follows:

Appendix A of Part 300--Hazard Ranking System

* * * * *

1.1 Definitions

* * * * *
    Channelized flow: Natural geological or manmade features such as
karst, fractures, lava tubes, and utility conduits (e.g., sewer lines),
which allow ground water and/or soil gas to move through the subsurface
environment more easily.
* * * * *
    Crawl space: The enclosed or semi-enclosed area between a regularly
occupied structure's foundation (e.g., pier and beam construction) and
the ground surface. Crawl space samples are collected to determine the
concentration of hazardous substances in the air beneath a regularly
occupied structure.
* * * * *
    Distance weight: Parameter in the HRS air migration pathway, ground
water migration pathway, and the soil exposure component of the soil
exposure and subsurface intrusion pathway that reduces the point value
assigned to targets as their distance increases from the site.
[unitless].
* * * * *
    Half-life: Length of time required for an initial concentration of
a substance to be halved as a result of loss through decay. The HRS
considers five decay processes for determining surface water
persistence: Biodegradation, hydrolysis, photolysis, radioactive decay,
and volatilization. The HRS considers two decay processes for
determining subsurface intrusion degradation: Biodegradation and
hydrolysis.
* * * * *
    Indoor air: The air present within a structure.
    Inhalation Unit Risk (IUR): The upper-bound excess lifetime cancer
risk estimated to result from continuous exposure to an agent (i.e.,
hazardous substance) at a concentration of 1[micro]g/m3 in air.
* * * * *
    Occupied structures: Structures with enclosed air space, either
where people are present on a regular basis or that were previously
occupied but vacated due to a site-related hazardous substance(s).
* * * * *
    Preferential subsurface intrusion pathways: Subsurface features
such as animal burrows, cracks in walls, spaces around utility lines or
drains through which a hazardous substance moves more easily into a
regularly occupied structure.
* * * * *
    Reference concentration (RfC): An estimate of a continuous
inhalation exposure to the human population that is likely to be
without an appreciable risk of deleterious effects during a lifetime.
    Reference dose (RfD): An estimate of a daily oral exposure to the
human population that is likely to be without an appreciable risk of
deleterious effects during a lifetime.
* * * * *
    Screening concentration: Media-specific benchmark concentration for
a hazardous substance that is used in the HRS for comparison with the
concentration of that hazardous substance in a sample from that media.
The screening concentration for a specific hazardous substance
corresponds to its reference concentration for inhalation exposures or
reference dose for oral exposures, as appropriate, and, if the
substance is a human carcinogen with either a weight-of-evidence
classification of A, B, or C, or a weight-of-evidence classification of
carcinogenic to humans, likely to be carcinogenic to humans or
suggestive evidence of carcinogenic potential, to that concentration
that corresponds to its 10 -\6\ individual lifetime excess
cancer risk for inhalation exposures or for oral exposures, as
appropriate.
* * * * *
    Slope factor (also referred to as cancer potency factor): Estimate
of the probability of response (for example, cancer) per unit intake of
a substance over a lifetime. The slope factor is typically used to
estimate upper-bound probability of an individual developing cancer as
a result of exposure to a particular level of a human carcinogen with
either a weight-of-evidence classification of A, B, or C, or a weight-
of-evidence classification of carcinogenic to humans, likely to be
carcinogenic to humans or having suggestive evidence of carcinogenic
potential. [(mg/kg-day) -\1\ for non-radioactive substances
and (pCi) -\1\ for radioactive substances].
    Soil gas: The gaseous elements and compounds in the small spaces
between particles of soil.
    Soil porosity: The degree to which the total volume of soil is
permeated with pores or cavities through which fluids (including air or
gas) can move. It is typically calculated as the ratio of the pore
spaces within the soil to the overall volume of the soil.
* * * * *
    Subslab: The area immediately beneath a regularly occupied
structure with a basement foundation or a slab-on-grade foundation.
Subslab samples are collected to determine the concentration of
hazardous substances in the soil gas beneath a home or building.
    Subsurface Intrusion: The migration of hazardous substances from
the unsaturated zone and/or the surficial ground water into overlying
structures.
    Surficial ground water: The uppermost saturated zone, typically
unconfined.
* * * * *
    Unit Risk: The upper-bound excess lifetime cancer risk estimated to
result from continuous exposure to an agent (i.e., hazardous substance)
at a concentration of 1 [micro]g/L in water, or 1 [micro]g/m\3\ in air.
    Unsaturated Zone: The portion of subsurface between the land
surface and the zone of saturation. It extends from the ground surface
to the surficial water table (excluding localized or perched water).
* * * * *
    Weight-of-evidence: EPA classification system for characterizing
the evidence supporting the designation of a substance as a human
carcinogen. The EPA weight-of-evidence groupings, depending on the date
EPA updated the profile, include either:
* * * * *

2.0 Evaluations Common to Multiple Pathways

    2.1 Overview. The HRS site score (S) is the result of an evaluation
of four pathways:
     Ground Water Migration (Sgw).
     Surface Water Migration (Ssw).
     Soil Exposure and Subsurface Intrusion
(Ssessi).
     Air Migration (Sa).

The ground water and air migration pathways use single threat
evaluations, while the surface water migration and soil exposure and
subsurface intrusion pathways use multiple threat evaluations. Three
threats are evaluated for the surface water migration pathway: Drinking
water, human food chain, and environmental. These threats are evaluated
for two separate migration components--overland/flood migration and
ground water to surface water migration. Two components are evaluated
for the soil exposure and subsurface intrusion pathway: Soil exposure
and subsurface intrusion. The soil exposure component evaluates two
threats: Resident population and nearby population, and the subsurface

intrusion component is a single threat evaluation.
    The HRS is structured to provide a parallel evaluation for each of
these pathways, components and threats. This section focuses on these
parallel evaluations, starting with the calculation of the HRS site
score and the individual pathway scores.
    2.1.1 Calculation of HRS site score. Scores are first calculated
for the individual pathways as specified in sections 2 through 7 and
then are combined for the site using the following root-mean-square
equation to determine the overall HRS site score, which ranges from 0
to 100:
[GRAPHIC] [TIFF OMITTED] TP29FE16.029

    2.1.2 Calculation of pathway score. Table 2-1, which is based on
the air migration pathway, illustrates the basic parameters used to
calculate a pathway score. As Table 2-1 shows, each pathway (component
or threat) score is the product of three ``factor categories'':
Likelihood of release, waste characteristics, and targets. (The soil
exposure and subsurface intrusion pathway uses likelihood of exposure
rather than likelihood of release.) Each of the three factor categories
contains a set of factors that are assigned numerical values and
combined as specified in sections 2 through 7. The factor values are
rounded to the nearest integer, except where otherwise noted.
    2.1.3 Common evaluations. Evaluations common to all four HRS
pathways include:
     Characterizing sources.

-- Identifying sources (and, for the soil exposure and subsurface
intrusion pathway, areas of observed contamination, areas of observed
exposure and/or areas of subsurface contamination (see sections 5.1.0
and 5.2.0)).
-- Identifying hazardous substances associated with each source (or
area of observed contamination, or observed exposure, or subsurface
contamination).
-- Identifying hazardous substances available to a pathway.

                  Table 2-1--Sample Pathway Scoresheet
------------------------------------------------------------------------
          Factor category             Maximum value      Value assigned
------------------------------------------------------------------------
                          Likelihood of Release
------------------------------------------------------------------------
1. Observed Release...............                550
2. Potential to Release...........                500
3. Likelihood of Release (higher                  550
 of lines 1 and 2)................
------------------------------------------------------------------------
                          Waste Characteristics
------------------------------------------------------------------------
4. Toxicity/Mobility..............              (\a\)
5. Hazardous Waste Quantity.......              (\a\)
6. Waste Characteristics..........                100
------------------------------------------------------------------------
                                 Targets
------------------------------------------------------------------------
7. Nearest Individual:              .................
    7a. Level I...................                 50
    7b. Level II..................                 45
    7c. Potential Contamination...                 20
    7d. Nearest Individual (higher                 50
     of lines 7a, 7b, or 7c)......
8. Population.....................              (\b\)
    8a. Level I...................              (\b\)
    8b. Level II..................              (\b\)
    8c. Potential Contamination...              (\b\)
    8d. Total Population (lines
     8a+8b+8c).
9. Resources......................                  5
10. Sensitive Environments........              (\b\)
    10a. Actual Contamination.....              (\b\)
    10b. Potential Environments...              (\b\)
    10c. Sensitive Environments                 (\b\)
     (lines 10a+10b)..............
11. Targets (lines 7d+8d+9+10c)...              (\b\)
12. Pathway Score is the product
 of Likelihood of Release, Waste
 Characteristics, and Targets,
 divided by 82,500. Pathway scores
 are limited to a maximum of 100
 points...........................
------------------------------------------------------------------------
\a\ Maximum value applies to waste characteristics category. The product
  of lines 4 and 5 is used in Table 2-7 to derive the value for the
  waste characteristics factor category.
\b\ There is no limit to the human population or sensitive environments
  factor values. However, the pathway score based solely on sensitive
  environments is limited to a maximum of 60 points.

 Scoring likelihood of release (or likelihood of exposure)
factor category.
    --Scoring observed release (or observed exposure or observed
contamination).
    --Scoring potential to release when there is no observed release.
 Scoring waste characteristics factor category.
    --Evaluating toxicity.
    [ssquf] Combining toxicity with mobility, persistence, degradation
and/or bioaccumulation (or ecosystem bioaccumulation) potential, as
appropriate to the pathway (component or threat).
    [ssquf] Evaluating hazardous waste quantity.
    --Combining hazardous waste quantity with the other waste
characteristics factors.
    [ssquf] Determining waste characteristics factor category value.
 Scoring targets factor category.

--Determining level of contamination for targets.

    These evaluations are essentially identical for the three migration
pathways (ground water, surface water, and air). However, the
evaluations differ in certain respects for the soil exposure and
subsurface intrusion pathway.
    Section 7 specifies modifications that apply to each pathway when
evaluating sites containing radioactive substances.
    Section 2 focuses on evaluations common at the pathway, component
and threat levels. Note that for the ground water and surface water
migration pathways, separate scores are calculated for each aquifer
(see section 3.0) and each watershed (see sections <IP_ADDRESS> and <IP_ADDRESS>)
when determining the pathway scores for a site. Although the
evaluations in section 2 do not vary when different aquifers or
watersheds are scored at a site, the specific factor values (for
example, observed release, hazardous waste quantity, toxicity/mobility)
that result from these evaluations can vary by aquifer and by watershed
at the site. This can occur through differences both in the specific
sources and targets eligible to be evaluated for each aquifer and
watershed and in whether observed releases can be established for each
aquifer and watershed. Such differences in scoring at the aquifer and
watershed level are addressed in sections 3 and 4, not section 2.
    2.2 Characterize sources. Source characterization includes
identification of the following:
     Sources (and areas of observed contamination, areas of
observed exposure or areas of subsurface contamination) at the site.
     Hazardous substances associated with these sources (or
areas of observed contamination, areas of observed exposure or areas of
subsurface contamination).
     Pathways potentially threatened by these hazardous
substances.
    Table 2-2 presents a sample worksheet for source characterization.
    2.2.1 Identify sources. For the three migration pathways, identify
the sources at the site that contain hazardous substances. Identify the
migration pathway(s) to which each source applies. For the soil
exposure and subsurface intrusion pathway, identify areas of observed
contamination, areas of observed exposure, and/or areas of subsurface
contamination at the site (see sections 5.1.0 and 5.2.0).

Table 2-2--Sample Source Characterization Worksheet

Source:__
A. Source dimensions and hazardous waste quantity.
Hazardous constituent quantity:__
Hazardous wastestream quantity:__
Volume:__
Area:__
Area of observed contamination:__
Area of observed exposure:__
Area of subsurface contamination:__
B. Hazardous substances associated with the source.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Available to pathway
                                                          --------------------------------------------------------------------------------------------------------------------------------------
                                                                        Air                                 Surface water (SW)               Soil exposure/subsurface intrusion (SESSI)
                                                          -------------------------------              -----------------------------------------------------------------------------------------
                   Hazardous substance                                                                                Soil exposure              Subsurface intrusion
                                                                                Ground water                             -------------------------------------------------------------
                                                                Gas        Particulate        (GW)        Overland/     GW to SW                                   Area of
                                                                                flood                     Resident       Nearby       observed    Area of subsurface
                                                                                exposure       contamination
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           ............  ...............  ............  ............  ............  ............  ............  ............  ..................
                                                           ............  ...............  ............  ............  ............  ............  ............  ............  ..................
                                                           ............  ...............  ............  ............  ............  ............  ............  ............  ..................
                                                           ............  ...............  ............  ............  ............  ............  ............  ............  ..................
                                                           ............  ...............  ............  ............  ............  ............  ............  ............  ..................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    2.2.2 Identify hazardous substances associated with a source. For
each of the three migration pathways, consider those hazardous
substances documented in a source (for example, by sampling, labels,
manifests, oral or written statements) to be associated with that
source when evaluating each pathway. In some instances, a hazardous
substance can be documented as being present at a site (for example, by
labels, manifests, oral or written statements), but the specific
source(s) containing that hazardous substance cannot be documented. For
the three migration pathways, in those instances when the specific
source(s) cannot be documented for a hazardous substance, consider the
hazardous substance to be present in each source at the site, except
sources for which definitive information indicates that the hazardous
substance was not or could not be present.
    For an area of observed contamination in the soil exposure
component of the soil exposure and subsurface intrusion pathway,
consider only those hazardous substances that meet the criteria for
observed contamination for that area (see section 5.1.0) to be
associated with that area when evaluating the pathway.
    For an area of observed exposure or area of subsurface
contamination (see section 5.2.0) in the subsurface intrusion component
of the soil exposure and subsurface intrusion pathway, consider only
those hazardous substances that:
     Meet the criteria for observed exposure, or
     Meet the criteria for observed release in an area of
subsurface contamination and has a vapor pressure greater than or equal
to one torr or a Henry's constant greater than or equal to
10-\5\ atm-m\3\/mol, or
     Meet the criteria for an observed release in a structure
within, or in a sample from below, an area of observed exposure and has
a vapor pressure greater than or equal to one torr or a Henry's
constant greater than or equal to 10-\5\ atm-m\3\/mol.
    2.2.3 Identify hazardous substances available to a pathway. In
evaluating each migration pathway, consider the following hazardous
substances available to migrate from the sources at the site to the
pathway:
     Ground water migration.

-- Hazardous substances that meet the criteria for an observed release
(see section 2.3) to ground water.
-- All hazardous substances associated with a source with a ground
water containment factor value greater than 0 (see section <IP_ADDRESS>).

     Surface water migration--overland/flood component.

-- Hazardous substances that meet the criteria for an observed release
to surface water in the watershed being evaluated.
-- All hazardous substances associated with a source with a surface
water containment factor value greater than 0 for the watershed (see
sections <IP_ADDRESS>.2.1.1 and <IP_ADDRESS>.2.2.1).

     Surface water migration--ground water to surface water
component.

-- Hazardous substances that meet the criteria for an observed release
to ground water.
-- All hazardous substances associated with a source with a ground
water containment factor value greater than 0 (see sections <IP_ADDRESS>.2
and <IP_ADDRESS>).

     Air migration.

-- Hazardous substances that meet the criteria for an observed release
to the atmosphere.
-- All gaseous hazardous substances associated with a source with a gas
containment factor value greater than 0 (see section <IP_ADDRESS>.1).
-- All particulate hazardous substances associated with a source with a
particulate containment factor value greater than 0 (see section
<IP_ADDRESS>.1).

     For each migration pathway, in those instances when the
specific source(s) containing the hazardous substance cannot be
documented, consider that hazardous substance to be available to
migrate to the pathway when it can be associated (see section 2.2.2)
with at least one source having a containment factor value greater than
0 for that pathway.
    In evaluating the soil exposure and subsurface intrusion pathway,
consider the following hazardous substances available to the pathway:
     Soil exposure component--resident population threat.

-- All hazardous substances that meet the criteria for observed
contamination at the site (see section 5.1.0).

     Soil exposure component--nearby population threat.

-- All hazardous substances that meet the criteria for observed
contamination at areas with an attractiveness/accessibility factor
value greater than 0 (see section <IP_ADDRESS>.1).

     Subsurface intrusion component.

-- All hazardous substances that meet the criteria for observed
exposure at the site (see section 5.2.0).
--All hazardous substances with a vapor pressure greater than or equal
to one torr or a Henry's constant greater than or equal to
10-5 atm-m\3\/mol that meet the criteria for an observed
release in an area of subsurface contamination (see section 5.2.0).
--All hazardous substances that meet the criteria for an observed
release in a structure within, or in a sample from below, an area of
observed exposure (see section 5.2.0).

    2.3 Likelihood of release. Likelihood of release is a measure of
the likelihood that a waste has been or will be released to the
environment. The likelihood of release factor category is assigned the
maximum value of 550 for a migration pathway whenever the criteria for
an observed release are met for that pathway. If the criteria for an
observed release are met, do not evaluate potential to release for that
pathway. When the criteria for an observed release are not met,
evaluate potential to release for that pathway, with a maximum value of
500. The evaluation of potential to release varies by migration pathway
(see sections 3, 4 and 6).
    Establish an observed release either by direct observation of the
release of a hazardous substance into the media being evaluated (for
example, surface water) or by chemical analysis of samples appropriate
to the pathway being evaluated (see sections 3, 4 and 6). The minimum
standard to establish an observed release by chemical analysis is
analytical evidence of a hazardous substance in the media significantly
above the background level. Further, some portion of the release must
be attributable to the site. Use the criteria in Table 2-3 as the
standard for determining analytical significance. (The criteria in
Table 2-3 are also used in establishing observed contamination for the
soil exposure component and for establishing areas of observed exposure
and areas of subsurface contamination in the subsurface intrusion
component of the soil exposure and subsurface intrusion pathway, see
section 5.1.0 and section 5.2.0). Separate criteria apply to
radionuclides (see section 7.1.1).

       Table 2-3--Observed Release Criteria for Chemical Analysis
------------------------------------------------------------------------

-------------------------------------------------------------------------
Sample Measurement < Sample Quantitation Limit.\a\
No observed release is established.

Sample Measurement >= Sample Quantitation Limit.\a\
An observed release is established as follows:
     If the background concentration is not detected (or is less
     than the detection limit), an observed release is established when
     the sample measurement equals or exceeds the sample quantitation
     limit.\a\
     If the background concentration equals or exceeds the
     detection limit, an observed release is established when the sample
     measurement is 3 times or more above the background concentration.
\a\ If the sample quantitation limit (SQL) cannot be established,
 determine if there is an observed release as follows:
If the sample analysis was performed under the EPA Contract Laboratory
 Program, use the EPA contract-required quantitation limit (CRQL) in
 place of the SQL.
If the sample analysis is not performed under the EPA Contract
 Laboratory Program, use the detection limit (DL) in place of the SQL.
------------------------------------------------------------------------

    2.4 Waste characteristics. The waste characteristics factor
category includes the following factors: Hazardous waste quantity,
toxicity, and as appropriate to the pathway or threat being evaluated,
mobility, persistence, degradation, and/or bioaccumulation (or
ecosystem bioaccumulation) potential.
    2.4.1 Selection of substance potentially posing greatest hazard.
For all pathways (components and threats), select the hazardous
substance potentially posing the greatest hazard for the pathway
(component or threat) and use that substance in evaluating the waste
characteristics category of the pathway (component or threat). For the
three migration pathways (and threats), base the selection of this
hazardous substance on the toxicity factor value for the substance,
combined with its mobility, persistence, and/or bioaccumulation (or
ecosystem bioaccumulation) potential factor values, as applicable to
the migration pathway (or threat). For the soil exposure component of
the soil exposure and subsurface intrusion pathway, base the selection
on the toxicity factor alone. For the subsurface intrusion component of
the soil exposure and subsurface intrusion pathway, base the selection
on the toxicity factor value for the substance, combined with its
degradation factor value. Evaluation of the toxicity factor is
specified in section <IP_ADDRESS>. Use and evaluation of the mobility,
persistence, degradation, and/or bioaccumulation (or ecosystem
bioaccumulation) potential factors vary by pathway (component or
threat) and are specified under the appropriate pathway (component or
threat) section. Section <IP_ADDRESS> identifies the specific factors that
are combined with toxicity in evaluating each pathway (component or
threat).
    <IP_ADDRESS> Toxicity factor. Evaluate toxicity for those hazardous
substances at the site that are available to the pathway being scored.
For all pathways and threats, except the surface water environmental
threat, evaluate human toxicity as specified below. For the surface
water environmental threat, evaluate ecosystem toxicity as specified in
section <IP_ADDRESS>.1.1.
    Establish human toxicity factor values based on quantitative dose-
response parameters for the following three types of toxicity:
     Cancer--Use slope factors (also referred to as cancer
potency factors) combined with weight-of-evidence ratings for
carcinogenicity for all exposure routes except inhalation. Use
inhalation unit risk (IUR) for inhalation exposure. If an inhalation
unit risk or a slope factor is not available for a substance, use its
ED10 value to estimate a slope factor as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.030

     Noncancer toxicological responses of chronic exposure--use
reference dose (RfD) or reference concentration (RfC) values as
applicable.
     Noncancer toxicological responses of acute exposure--use
acute toxicity parameters, such as the LD50.
    Assign human toxicity factor values to a hazardous substance using
Table 2-4, as follows:
     If RfD/RfC and slope factor/inhalation unit risk values
are available for the hazardous substance, assign the substance a value
from Table 2-4 for each. Select the higher of the two values assigned
and use it as the overall toxicity factor value for the hazardous
substance.
     If either an RfD/RfC or slope factor/inhalation unit risk
value is available, but not both, assign the hazardous substance an
overall toxicity factor value from Table 2-4 based solely on the
available value (RfD/RfC or slope factor/inhalation unit risk).
     If neither an RfD/RfC nor slope factor/inhalation unit
risk value is available, assign the hazardous substance an overall
toxicity factor value from Table 2-4 based solely on acute toxicity.
That is, consider acute toxicity in Table 2-4 only when both RfD/RfC
and slope factor/IUR values are not available.
     If neither an RfD/RfC, nor slope factor/inhalation unit
risk, nor acute toxicity value is available, assign the hazardous
substance an overall toxicity factor value of 0 and use other hazardous
substances for which information is available in evaluating the
pathway.

                  Table 2-4--Toxicity Factor Evaluation
------------------------------------------------------------------------
                                                               Assigned
                                                                value
------------------------------------------------------------------------
                        Chronic toxicity (Human)
------------------------------------------------------------------------
Reference dose (RfD) (mg/kg-day):
    RfD < 0.0005...........................................       10,000
    0.0005 <= RfD < 0.005..................................        1,000
    0.005 <= RfD < 0.05....................................          100
    0.05 <= RfD < 0.5......................................           10
    0.5 <= RfD.............................................            1
    RfD not available......................................            0
Reference concentration (RfC) (mg/m\3\):
    RfC < 0.0001...........................................       10,000
    0.0001 <= RfC < 0.006..................................        1,000
    0.006 <= RfC < 0.2.....................................          100
    0.2 <= RfC < 2.0.......................................           10
    2.0 <= RfC.............................................            1
    RfC not available......................................            0
------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
                                             Carcinogenicity (Human)
-----------------------------------------------------------------------------------------------------------------
                                             B or Likely to be       C or Suggestive evidence
      A or Carcinogenic to humans          carcinogenic to humans   of carcinogenic potential    Assigned value
----------------------------------------------------------------------------------------------------------------
                                 Weight-of-evidence a/Slope factor (mg/kg-day)-1
----------------------------------------------------------------------------------------------------------------
0.5 <= SF \b\..........................  5 <= SF..................  50 <= SF.................             10,000

0.05 <= SF < 0.5.......................  0.5 <= SF < 5............  5 <= SF < 50.............              1,000
SF < 0.05..............................  0.05 <= SF < 0.5.........  0.5 <= SF < 5............                100
 --                                      SF < 0.05................  SF < 0.5.................                 10
Slope factor not available.............  Slope factor not           Slope factor not                           0
                                          available.                 available.
----------------------------------------------------------------------------------------------------------------
                              Weight-of-evidence a/Inhalation unit risk ([mu]g/m3)
----------------------------------------------------------------------------------------------------------------
0.00004 <= IUR \c\.....................  0.0004 <= IUR............  0.004 <= IUR.............             10,000
0.00001 <= IUR < 0.00004...............  0.0001 <= IUR < 0.0004...  0.001 <= IUR < 0.004.....              1,000
IUR < 0.00001..........................  0.00001 <= IUR < 0.0001..  0.0001 <= IUR < 0.001....                100
 --                                      < 0.00001................  IUR < 0.0001.............                 10
Inhalation unit risk not available.....  Inhalation unit risk not   Inhalation unit risk not                   0
                                          available.                 available.
----------------------------------------------------------------------------------------------------------------
\a\ A, B, and C, as well as Carcinogenic to humans, Likely to be carcinogenic to humans, and Suggestive evidence
  of carcinogenic potential refer to weight-of-evidence categories. Assign substances with a weight-of-evidence
  category of D (inadequate evidence of carcinogenicity) or E (evidence of lack of carcinogenicity), as well as
  inadequate information to assess carcinogenic potential and not likely to be carcinogenic to humans a value of
  0 for carcinogenicity.
\b\ SF = Slope factor.
\c\ IUR = Inhalation Unit Risk.

----------------------------------------------------------------------------------------------------------------
                                             Acute Toxicity (Human)
-----------------------------------------------------------------------------------------------------------------
                                                        Dust or mist LC50   Gas or vapor LC50
        Oral LD50 (mg/kg)         Dermal LD50 (mg/kg)        (mg/l)               (ppm)          Assigned value
----------------------------------------------------------------------------------------------------------------
LD50 < 5........................  LD50 < 2...........  LC50 < 0.2........  LC50 < 20.........              1,000
5 <= LD50 < 50..................  2 <= LD50 < 20.....  0.2 <= LC50 < 2...  20 <= LC50 <200...                100
50 <= LD50 < 500................  20 <= LD50 < 200...  2 <= LC50 <20.....  200 <= LC50 <2,000                 10
500 <= LD50.....................  200 <= LD50........  20 <= LC50........  2,000 <= LC50.....                  1
LD50 not available..............  LD50 not available.  LD50 not available  LD50 not available                  0
----------------------------------------------------------------------------------------------------------------

    If a toxicity factor value of 0 is assigned to all hazardous
substances available to a particular pathway (that is, insufficient
toxicity data are available for evaluating all the substances), use a
default value of 100 as the overall human toxicity factor value for all
hazardous substances available to the pathway. For hazardous substances
having usable toxicity data for multiple exposure routes (for example,
inhalation and ingestion), consider all exposure routes and use the
highest assigned value, regardless of exposure route, as the toxicity
factor value.
    For HRS purposes, assign both asbestos and lead (and its compounds)
a human toxicity factor value of 10,000.
    Separate criteria apply for assigning factor values for human
toxicity and ecosystem toxicity for radionuclides (see sections 7.2.1
and 7.2.2).
    <IP_ADDRESS> Hazardous substance selection. For each hazardous substance
evaluated for a migration pathway (or threat), combine the human
toxicity factor value (or ecosystem toxicity factor value) for the
hazardous substance with a mobility, persistence, and/or
bioaccumulation (or ecosystem bioaccumulation) potential factor value
as follows:
     Ground water migration.

--Determine a combined human toxicity/mobility factor value for the
hazardous substance (see section 3.2.1).

     Surface water migration--overland/flood migration
component.

--Determine a combined human toxicity/persistence factor value for the
hazardous substance for the drinking water threat (see section
<IP_ADDRESS>.1).

--Determine a combined human toxicity/persistence/bioaccumulation
factor value for the hazardous substance for the human food chain
threat (see section <IP_ADDRESS>.1).
--Determine a combined ecosystem toxicity/persistence/bioaccumulation
factor value for the hazardous substance for the environmental threat
(see section <IP_ADDRESS>.1).

     Surface water migration--ground water to surface water
migration component.

--Determine a combined human toxicity/mobility/persistence factor value
for the hazardous substance for the drinking water threat (see section
<IP_ADDRESS>.1).
--Determine a combined human toxicity/mobility/persistence/
bioaccumulation factor value for the hazardous substance for the human
food chain threat (see section <IP_ADDRESS>.1).
--Determine a combined ecosystem toxicity/mobility/persistence/
bioaccumulation factor value for the hazardous substance for the
environmental threat (see section <IP_ADDRESS>.1).
     Air migration.

     Determine a combined human toxicity/mobility factor value
for the hazardous substance (see section 6.2.1).

    Determine each combined factor value for a hazardous substance by
multiplying the individual factor values appropriate to the pathway (or
threat). For each migration pathway (or threat) being evaluated, select
the hazardous substance with the highest combined factor value and use
that substance in evaluating the waste characteristics factor category
of the pathway (or threat).
    For the soil exposure and subsurface intrusion pathway, determine
toxicity and toxicity/degradation factor values as follows:

 Soil exposure and subsurface intrusion--soil exposure
component.

     Select the hazardous substance with the highest human
toxicity factor value from among the substances that meet the criteria
for observed contamination for the threat evaluated and use that
substance in evaluating the waste characteristics factor category (see
section

<IP_ADDRESS>.1).

 Soil exposure and subsurface intrusion--subsurface intrusion
component.

     Determine a combined human toxicity/degradation factor
value for each hazardous substance being evaluated that:
    [ssquf] Meets the criteria for observed exposure, or
    [ssquf] Meets the criteria for observed release in an area of
subsurface contamination and has a vapor pressure greater than or equal
to one torr or a Henry's constant greater than or equal to
10-5 atm-m\3\/mol, or
    [ssquf] Meets the criteria for an observed release in a structure
within, or in a sample from below, an area of observed exposure and has
a vapor pressure greater than or equal to one torr or a Henry's
constant greater than or equal to 10-5 atm-m\3\/mol.
     Select the hazardous substance with the highest combined
factor value and use that substance in evaluating the waste
characteristics factor category (see sections <IP_ADDRESS>.1 and <IP_ADDRESS>).

    2.4.2 Hazardous waste quantity. Evaluate the hazardous waste
quantity factor by first assigning each source (or area of observed
contamination, area of observed exposure or area of subsurface
contamination) a source hazardous waste quantity value as specified
below. Sum these values to obtain the hazardous waste quantity factor
value for the pathway being evaluated.
    In evaluating the hazardous waste quantity factor for the three
migration pathways, allocate hazardous substances and hazardous
wastestreams to specific sources in the manner specified in section
2.2.2, except: Consider hazardous substances and hazardous wastestreams
that cannot be allocated to any specific source to constitute a
separate ``unallocated source'' for purposes of evaluating only this
factor for the three migration pathways. Do not, however, include a
hazardous substance or hazardous wastestream in the unallocated source
for a migration pathway if there is definitive information indicating
that the substance or wastestream could only have been placed in
sources with a containment factor value of 0 for that migration
pathway.
    In evaluating the hazardous waste quantity factor for the soil
exposure component of the soil exposure and subsurface intrusion
pathway, allocate to each area of observed contamination only those
hazardous substances that meet the criteria for observed contamination,
for that area of observed contamination and only those hazardous
wastestreams that contain hazardous substances that meet the criteria
for observed contamination for that area of observed contamination. Do
not consider other hazardous substances or hazardous wastestreams at
the site in evaluating this factor for the soil exposure component of
the soil exposure and subsurface intrusion pathway.
    In evaluating the hazardous waste quantity factor for the
subsurface intrusion component of the soil exposure and subsurface
intrusion pathway, allocate to each area of observed exposure or area
of subsurface contamination only those hazardous substances and
hazardous wastestreams that contain hazardous substances that:
     Meet the criteria for observed exposure, or
     Meet the criteria for observed release in an area of
subsurface contamination and has a vapor pressure greater than or equal
to one torr or a Henry's constant greater than or equal to
10-5 atm-m\3\/mol, or
     Meet the criteria for an observed release in a structure
within, or in a sample from below, an area of observed exposure and has
a vapor pressure greater than or equal to one torr or a Henry's
constant greater than or equal to 10-5 atm-m\3\/mol.
    Do not consider other hazardous substances or hazardous
wastestreams at the site in evaluating this factor for the subsurface
intrusion component of the soil exposure and subsurface intrusion
pathway. When determining the hazardous waste quantity for multi-
subunit structures, use the procedures identified in section <IP_ADDRESS>.2.
    <IP_ADDRESS> Source hazardous waste quantity. For each of the three
migration pathways, assign a source hazardous waste quantity value to
each source (including the unallocated source) having a containment
factor value greater than 0 for the pathway being evaluated. Consider
the unallocated source to have a containment factor value greater than
0 for each migration pathway.
    For the soil exposure component of the soil exposure and subsurface
intrusion pathway, assign a source hazardous waste quantity value to
each area of observed contamination, as applicable to the threat being
evaluated.
    For the subsurface intrusion component of the soil exposure and
subsurface intrusion pathway, assign a source hazardous waste quantity
value to each regularly occupied structure within an area of observed
exposure or an area of subsurface contamination that has a structure
containment factor value greater than 0.
    For determining all hazardous waste quantity calculations except
for an unallocated source or an area of subsurface contamination,
evaluate using the following four measures in the following hierarchy:
     Hazardous constituent quantity.
     Hazardous wastestream quantity.
     Volume.
     Area.
    For the unallocated source, use only the first two measures. For an
area of subsurface contamination, evaluate non-radioactive hazardous
substances using only the last two measures and evaluate radioactive
hazardous substances using hazardous wastestream quantity only. See
also section 7.0 regarding the evaluation of radioactive substances.
    Separate criteria apply for assigning a source hazardous waste
quantity value for radionuclides (see section 7.2.5).
    <IP_ADDRESS>.1 Hazardous constituent quantity. Evaluate hazardous
constituent quantity for the source (or area of observed contamination)
based solely on the mass of CERCLA hazardous substances (as defined in
CERCLA section 101(14), as amended) allocated to the source (or area of
observed contamination), except:
     For a hazardous waste listed pursuant to section 3001 of
the Solid Waste Disposal Act, as amended by the Resource Conservation
and Recovery Act of 1976 (RCRA), 42 U.S.C. 6901 et seq., determine its
mass for the evaluation of this measure as follows:

--If the hazardous waste is listed solely for Hazard Code T (toxic
waste), include only the mass of constituents in the hazardous waste
that are CERCLA hazardous substances and not the mass of the entire
hazardous waste.
-- If the hazardous waste is listed for any other Hazard Code
(including T plus any other Hazard Code), include the mass of the
entire hazardous waste.

     For a RCRA hazardous waste that exhibits the
characteristics identified under section 3001 of RCRA, as amended,
determine its mass for the evaluation of this measure as follows:

--If the hazardous waste exhibits only the characteristic of toxicity
(or only the characteristic of EP toxicity), include only the mass of
constituents in the hazardous waste that are CERCLA hazardous
substances and not the mass of the entire hazardous waste.
--If the hazardous waste exhibits any other characteristic identified
under

section 3001 (including any other characteristic plus the
characteristic of toxicity [or the characteristic of EP toxicity]),
include the mass of the entire hazardous waste.

    Based on this mass, designated as C, assign a value for hazardous
constituent quantity as follows:
     For the migration pathways, assign the source a value for
hazardous constituent quantity using the Tier A equation of Table 2-5.
     For the soil exposure and subsurface intrusion pathway--
soil exposure component, assign the area of observed contamination a
value using the Tier A equation of Table 5-2 (section <IP_ADDRESS>.2).
     For the soil exposure and subsurface intrusion pathway--
subsurface intrusion component, assign the area of observed exposure a
value using the Tier A equation of Table 5-18 (section <IP_ADDRESS>.2).
    If the hazardous constituent quantity for the source (or area of
observed contamination or area of observed exposure) is adequately
determined (that is, the total mass of all CERCLA hazardous substances
in the source and releases from the source [or in the area of observed
contamination or area of observed exposure] is known or is estimated
with reasonable confidence), do not evaluate the other three measures
discussed below. Instead assign these other three measures a value of 0
for the source (or area of observed contamination or area of observed
exposure) and proceed to section <IP_ADDRESS>.5.
    If the hazardous constituent quantity is not adequately determined,
assign the source (or area of observed contamination or area of
observed exposure) a value for hazardous constituent quantity based on
the available data and proceed to section <IP_ADDRESS>.2.

        Table 2-5--Hazardous Waste Quantity Evaluation Equations
------------------------------------------------------------------------
                                                          Equation for
     Tier              Measure              Units       assigning value
                                                              \a\
------------------------------------------------------------------------
A.............  Hazardous constituent  lb............  C
                 quantity (C).
B \b\.........  Hazardous wastestream  lb............  W/5,000
                 quantity (W).
C \b\.........  Volume (V)...........
                Landfill.............  yd\3\.........  V/2,500
                Surface impoundment..  yd\3\.........  V/2.5
                Surface impoundment    yd\3\.........  V/2.5
                 (buried/backfilled).
                Drums \c\............  gallon........  V/2.5
                Tanks and containers   yd\3\.........  V/2.5
                 other than drums.
                Contaminated soil....  yd\3\.........  V/2,500
                Pile.................  yd\3\.........  V/2.5
                Other................  yd\3\.........  V/2.5
D \b\.........  Area (A).............
                Landfill.............  ft\2\.........  A/3,400
                Surface impoundment..  ft\2\.........  A/13
                Surface impoundment    ft\2\.........  A/13
                 (buried/backfilled).
                Land treatment.......  ft\2\.........  A/270
                Pile \d\.............  ft\2\.........  A/13
                Contaminated soil....  ft\2\.........  A/34,000
------------------------------------------------------------------------
\a\ Do not round to nearest integer.
\b\ Convert volume to mass when necessary: 1 ton = 2,000 pounds = 1
  cubic yard = 4 drums = 200 gallons.
\c\ If actual volume of drums is unavailable, assume 1 drum = 50
  gallons.
\d\ Use land surface area under pile, not surface area of pile.

    <IP_ADDRESS>.2 Hazardous wastestream quantity. Evaluate hazardous
wastestream quantity for the source (or area of observed contamination
or area of observed exposure) based on the mass of hazardous
wastestreams plus the mass of any additional CERCLA pollutants and
contaminants (as defined in CERCLA section 101[33], as amended) that
are allocated to the source (or area of observed contamination or area
of observed exposure). For a wastestream that consists solely of a
hazardous waste listed pursuant to section 3001 of RCRA, as amended or
that consists solely of a RCRA hazardous waste that exhibits the
characteristics identified under section 3001 of RCRA, as amended,
include the mass of that entire hazardous waste in the evaluation of
this measure.
    Based on this mass, designated as W, assign a value for hazardous
wastestream quantity as follows:
     For the migration pathways, assign the source a value for
hazardous wastestream quantity using the Tier B equation of Table 2-5.
     For the soil exposure and subsurface intrusion pathway--
soil exposure component, assign the area of observed contamination a
value using the Tier B equation of Table 5-2 (section <IP_ADDRESS>.2).
     For the soil exposure and subsurface intrusion pathway--
subsurface intrusion component, assign the area of observed exposure a
value using the Tier B equation of Table 5-18 (section <IP_ADDRESS>.2).
    Do not evaluate the volume and area measures described below if the
source is the unallocated source or if the following condition applies:
     The hazardous wastestream quantity for the source (or area
of observed contamination) is adequately determined--that is, total
mass of all hazardous wastestreams and CERCLA pollutants and
contaminants for the source and releases from the source (or for the
area of observed contamination) is known or is estimated with
reasonable confidence.
    If the source is the unallocated source or if this condition
applies, assign the volume and area measures a value of 0 for the
source (or area of observed contamination) and proceed to section
<IP_ADDRESS>.5. Otherwise, assign the source (or area of observed
contamination) a value for Hazardous wastestream quantity based on the
available data and proceed to section <IP_ADDRESS>.3.

    <IP_ADDRESS>.3 Volume. Evaluate the volume measure using the volume of
the source (or the volume of the area of observed contamination, area
of observed exposure, or area of subsurface contamination). For the
soil exposure and subsurface intrusion pathway, restrict the use of the
volume measure to those areas of observed contamination, areas of
observed exposure, or areas of subsurface contamination as specified in
sections <IP_ADDRESS>.2 and <IP_ADDRESS>.2.
    Based on the volume, designated as V, assign a value to the volume
measure as follows:
     For the migration pathways, assign the source a value for
volume using the appropriate Tier C equation of Table 2-5.
     For the soil exposure and subsurface intrusion pathway--
soil exposure component, assign the area of observed contamination a
value for volume using the appropriate Tier C equation of Table 5-2
(section <IP_ADDRESS>.2).
     For the soil exposure and subsurface intrusion pathway--
subsurface intrusion component, assign the value based on the volume of
the regularly occupied structures within the area of observed exposure
or area of subsurface contamination using the Tier C equation of Table
5-18 (section <IP_ADDRESS>.2).
    If the volume of the source (or volume of the area of observed
contamination, area of observed exposure, or area of subsurface
contamination, if applicable) can be determined, do not evaluate the
area measure. Instead, assign the area measure a value of 0 and proceed
to section <IP_ADDRESS>.5. If the volume cannot be determined (or is not
applicable for the soil exposure and subsurface intrusion pathway),
assign the source (or area of observed contamination, area of observed
exposure, or area of subsurface contamination) a value of 0 for the
volume measure and proceed to section <IP_ADDRESS>.4.
    <IP_ADDRESS>.4 Area. Evaluate the area measure using the area of the
source (or the area of the area of observed contamination, area of
observed exposure, or area of subsurface contamination). Based on this
area, designated as A, assign a value to the area measure as follows:
     For the migration pathways, assign the source a value for
area using the appropriate Tier D equation of Table 2-5.
     For the soil exposure and subsurface intrusion pathway--
soil exposure component, assign the area of observed contamination a
value for area using the appropriate Tier D equation of Table 5-2
(section <IP_ADDRESS>.2).
     For the soil exposure and subsurface intrusion pathway--
subsurface intrusion component, assign a value based on the area of
regularly occupied structures within the area of observed exposure or
area of subsurface contamination using the Tier D equation of Table 5-
18 (section <IP_ADDRESS>.2).
    <IP_ADDRESS>.5 Calculation of source hazardous waste quantity value.
Select the highest of the values assigned to the source (or areas of
observed contamination, areas of observed exposure, or areas of
subsurface contamination) for the hazardous constituent quantity,
hazardous wastestream quantity, volume, and area measures. Assign this
value as the source hazardous waste quantity value. Do not round to the
nearest integer.
    <IP_ADDRESS> Calculation of hazardous waste quantity factor value. Sum
the source hazardous waste quantity values assigned to all sources
(including the unallocated source) or areas of observed contamination,
areas of observed exposure, or areas of subsurface contamination for
the pathway being evaluated and round this sum to the nearest integer,
except: If the sum is greater than 0, but less than 1, round it to 1.
Based on this value, select a hazardous waste quantity factor value for
the pathway from Table 2-6.

            Table 2-6--Hazardous Waste Quantity Factor Values
------------------------------------------------------------------------
                                                               Assigned
               Hazardous waste quantity value                   value
------------------------------------------------------------------------
0..........................................................            0
1 \a\ to 100...............................................        \b\ 1
Greater than 100 to 10,000.................................          100
Greater than 10,000 to 1,000,000...........................       10,000
Greater than 1,000,000.....................................    1,000,000
------------------------------------------------------------------------
\a\ If the hazardous waste quantity value is greater than 0, but less
  than 1, round it to 1 as specified in text.
\b\ For the pathway, if hazardous constituent quantity is not adequately
  determined, assign a value as specified in the text; do not assign the
  value of 1.

    For a migration pathway, if the hazardous constituent quantity is
adequately determined (see section <IP_ADDRESS>.1) for all sources (or all
portions of sources and releases remaining after a removal action),
assign the value from Table 2-6 as the hazardous waste quantity factor
value for the pathway. If the hazardous constituent quantity is not
adequately determined for one or more sources (or one or more portions
of sources or releases remaining after a removal action) assign a
factor value as follows:
     If any target for that migration pathway is subject to
Level I or Level II concentrations (see section 2.5), assign either the
value from Table 2-6 or a value of 100, whichever is greater, as the
hazardous waste quantity factor value for that pathway.
     If none of the targets for that pathway is subject to
Level I or Level II concentrations, assign a factor value as follows:

--If there has been no removal action, assign either the value from
Table 2-6 or a value of 10, whichever is greater, as the hazardous
waste quantity factor value for that pathway.
--If there has been a removal action:
    [ssquf] Determine values from Table 2-6 with and without
consideration of the removal action.
    [ssquf] If the value that would be assigned from Table 2-6 without
consideration of the removal action would be 100 or greater, assign
either the value from Table 2-6 with consideration of the removal
action or a value of 100, whichever is greater, as the hazardous waste
quantity factor value for the pathway.
    [ssquf] If the value that would be assigned from Table 2-6 without
consideration of the removal action would be less than 100, assign a
value of 10 as the hazardous waste quantity factor value for the
pathway.

    For the soil exposure component of the soil exposure and subsurface
intrusion pathway, if the hazardous constituent quantity is adequately
determined for all areas of observed contamination, assign the value
from Table 2-6 as the hazardous waste quantity factor value. If the
hazardous constituent quantity is not adequately determined for one or
more areas of observed contamination, assign either the value from
Table 2-6 or a value of 10, whichever is greater, as the hazardous
waste quantity factor value.
    For the subsurface intrusion component of the soil exposure and
subsurface intrusion pathway, if the hazardous constituent quantity is
adequately determined for all areas of observed exposure, assign the
value from Table 2-6 as the hazardous waste quantity factor value. If
the hazardous constituent quantity is not adequately determined for one
or more areas of observed exposure, assign either the value from Table
2-6 or assign a factor value as follows:

     If any target for the subsurface intrusion component is
subject to Level I or Level II concentrations (see section 2.5), assign
either the value from Table 2-6 or a value of 100, whichever is

greater, as the hazardous waste quantity factor value for this
component.
     If none of the targets for the subsurface intrusion
component is subject to Level I or Level II concentrations and if there
has been a removal action, assign a factor value as follows:
--Determine the values from Table 2-6 with and without consideration of
the removal action.
--If the value that would be assigned from Table 2-6 without
consideration of the removal action would be 100 or greater, assign
either the value from Table 2-6 with consideration of the removal
action or a value of 100, whichever is greater, as the hazardous waste
quantity factor value for the component.
--If the value that would be assigned from Table 2-6 without
consideration of the removal action would be less than 100, assign a
value of 10 as the hazardous waste quantity factor value for the
component.

     Otherwise, if none of the targets for the subsurface
intrusion component is subject to Level I or Level II concentrations
and there has not been a removal action, assign a value from Table 2-6
or a value of 10, whichever is greater.
    2.4.3 Waste characteristics factor category value. Determine the
waste characteristics factor category value as specified in section
<IP_ADDRESS> for all pathways and threats, except the surface water-human
food chain threat and the surface water-environmental threat. Determine
the waste characteristics factor category value for these latter two
threats as specified in section <IP_ADDRESS>.
    <IP_ADDRESS> Factor category value. For the pathway (component or
threat) being evaluated, multiply the toxicity or combined factor
value, as appropriate, from section <IP_ADDRESS> and the hazardous waste
quantity factor value from section <IP_ADDRESS>, subject to a maximum
product of 1x10\8\. Based on this waste characteristics product, assign
a waste characteristics factor category value to the pathway (component
or threat) from Table 2-7.

         Table 2-7--Waste Characteristics Factor Category Values
------------------------------------------------------------------------
                                                               Assigned
               Waste characteristics product                    value
------------------------------------------------------------------------
0..........................................................            0
Greater than 0 to less than 10.............................            1
10 to less than 1x10\2\....................................            2
1x10\2\ to less than 1x10\3\...............................            3
1x10\3\ to less than 1x10\4\...............................            6
1x10\4\ to less than 1x10\5\...............................           10
1x10\5\ to less than 1x10\6\...............................           18
1x10\6\ to less than 1x10\7\...............................           32
1x10\7\ to less than 1x10\8\...............................           56
1x10\8\ to less than 1x10\9\...............................          100
1x10\9\ to less than 1x10\10\..............................          180
1x10\10\ to less than 1x10\11\.............................          320
1x10\11\ to less than 1x10\12\.............................          560
1x10\12\...................................................        1,000
------------------------------------------------------------------------

    <IP_ADDRESS> Factor category value, considering bioaccumulation
potential. For the surface water-human food chain threat and the
surface water-environmental threat, multiply the toxicity or combined
factor value, as appropriate, from section <IP_ADDRESS> and the hazardous
waste quantity factor value from section <IP_ADDRESS>, subject to:
     A maximum product of 1x10\12\, and
     A maximum product exclusive of the bioaccumulation (or
ecosystem bioaccumulation) potential factor of 1x 10\8\.
    Based on the total waste characteristics product, assign a waste
characteristics factor category value to these threats from Table 2-7.
    2.5 Targets. The types of targets evaluated include the following:
     Individual (factor name varies by pathway, component, and
threat).
     Human population.
     Resources (these vary by pathway, component, and threat).
     Sensitive environments (included for the surface water
migration pathway, air migration pathway, and soil exposure component
of the soil exposure and subsurface intrusion pathway).
    The factor values that may be assigned to each type of target have
the same range for each pathway for which that type of target is
evaluated. The factor value for most types of targets depends on
whether the target is subject to actual or potential contamination for
the pathway and whether the actual contamination is Level I or Level
II:
     Actual contamination: Target is associated either with a
sampling location that meets the criteria for an observed release (or
observed contamination or observed exposure) for the pathway or with an
observed release based on direct observation for the pathway
(additional criteria apply for establishing actual contamination for
the human food chain threat in the surface water migration pathway, see
sections <IP_ADDRESS> and <IP_ADDRESS>). Sections 3 through 6 specify how to
determine the targets associated with a sampling location or with an
observed release based on direct observation. Determine whether the
actual contamination is Level I or Level II as follows:

--Level I:
    [ssquf] Media-specific concentrations for the target meet the
criteria for an observed release (or observed contamination or observed
exposure) for the pathway and are at or above media-specific benchmark
values. These benchmark values (see section 2.5.2) include both
screening concentrations and concentrations specified in regulatory
limits (such as Maximum Contaminant Level (MCL) values), or
    [ssquf] For the human food chain threat in the surface water
migration pathway, concentrations in tissue samples from aquatic human
food chain organisms are at or above benchmark values. Such tissue
samples may be used in addition to media-specific concentrations only
as specified in sections <IP_ADDRESS> and <IP_ADDRESS>.

--Level II:
    [ssquf] Media-specific concentrations for the target meet the
criteria for an observed release (or observed contamination or observed
exposure) for the pathway, but are less than media-specific benchmarks.
If none of the hazardous substances eligible to be evaluated for the
sampling location has an applicable benchmark, assign Level II to the
actual contamination at the sampling location, or
    [ssquf] For observed releases or observed exposures based on direct
observation, assign Level II to targets as specified in sections 3, 4,
5, and 6, or
    [ssquf] For the human food chain threat in the surface water
migration pathway, concentrations in tissue samples from aquatic human
food chain organisms, when applicable, are below benchmark values.
--If a target is subject to both Level I and Level II concentrations
for a pathway (or threat), evaluate the target using Level I
concentrations for that pathway (or threat).

     Potential contamination: Target is subject to a potential
release (that is, target is not associated with actual contamination
for that pathway or threat).
    Assign a factor value for individual risk as follows (select the
highest value that applies to the pathway or threat):
     50 points if any individual is exposed to Level I
concentrations.
     45 points if any individual is exposed to Level II
concentrations.

     Maximum of 20 points if any individual is subject to
potential contamination. The value assigned is 20 unless reduced by a
distance or dilution weight appropriate to the pathway.
    Assign factor values for population and sensitive environments as
follows:
     Sum Level I targets and multiply by 10. (Level I is not
used for sensitive environments in the soil exposure component of the
soil exposure and subsurface intrusion and air migration pathways.)
     Sum Level II targets.
     Multiply potential targets in all but the soil exposure
and subsurface intrusion pathway by distance or dilution weights
appropriate to the pathway, sum, and divide by 10. Distance or dilution
weighting accounts for diminishing exposure with increasing distance or
dilution within the different pathways. For targets within an area of
subsurface contamination in the subsurface intrusion component of the
soil exposure and subsurface intrusion pathway, multiply by a weighting
factor as directed in section <IP_ADDRESS>.2.3.
     Sum the values for the three levels.
    In addition, resource value points are assigned within all pathways
for welfare-related impacts (for example, impacts to agricultural
land), but do not depend on whether there is actual or potential
contamination.
    2.5.1 Determination of level of actual contamination at a sampling
location. Determine whether Level I concentrations or Level II
concentrations apply at a sampling location (and thus to the associated
targets) as follows:
     Select the benchmarks applicable to the pathway (component
or threat) being evaluated.
     Compare the concentrations of hazardous substances in the
sample (or comparable samples) to their benchmark concentrations for
the pathway (component or threat), as specified in section 2.5.2.
     Determine which level applies based on this comparison.
     If none of the hazardous substances eligible to be
evaluated for the sampling location has an applicable benchmark, assign
Level II to the actual contamination at that sampling location for the
pathway (component or threat).
    In making the comparison, consider only those samples, and only
those hazardous substances in the sample, that meet the criteria for an
observed release (or observed contamination or observed exposure) for
the pathway, except: Tissue samples from aquatic human food chain
organisms may also be used as specified in sections <IP_ADDRESS> and <IP_ADDRESS>
of the surface water-human food chain threat. If any hazardous
substance is present in more than one comparable sample for the
sampling location, use the highest concentration of that hazardous
substance from any of the comparable samples in making the comparisons.
    Treat sets of samples that are not comparable separately and make a
separate comparison for each such set.
    2.5.2 Comparison to benchmarks. Use the following media-specific
benchmarks for making the comparisons for the indicated pathway (or
threat):
     Maximum Contaminant Level Goals (MCLGs)--ground water
migration pathway and drinking water threat in surface water migration
pathway. Use only MCLG values greater than 0.
     Maximum Contaminant Levels (MCLs)--ground water migration
pathway and drinking water threat in surface water migration pathway.
     Food and Drug Administration Action Level (FDAAL) for fish
or shellfish--human food chain threat in surface water migration
pathway.
     EPA Ambient Water Quality Criteria (AWQC/National
Recommended Water Quality Criteria) for protection of aquatic life--
environmental threat in surface water migration pathway.
     EPA Ambient Aquatic Life Advisory Concentrations (AALAC)--
environmental threat in surface water migration pathway.
     National Ambient Air Quality Standards (NAAQS)--air
migration pathway.
     National Emission Standards for Hazardous Air Pollutants
(NESHAPs)--air migration pathway. Use only those NESHAPs promulgated in
ambient concentration units.
     Screening concentration for cancer corresponding to that
concentration that corresponds to the 10-\6\ individual
cancer risk for inhalation exposures (air migration pathway or
subsurface intrusion component of the soil exposure and subsurface
intrusion pathway) or for oral exposures (ground water migration
pathway; drinking water and human food chain threats in surface water
migration pathway; and soil exposure and subsurface intrusion pathway).
     Screening concentration for noncancer toxicological
responses corresponding to the RfC for inhalation exposures (air
migration pathway and subsurface intrusion component of the soil
exposure and subsurface intrusion pathway) or RfD for oral exposures
(ground water migration pathway; drinking water and human food chain
threats in surface water migration pathway; and soil exposure and
subsurface intrusion pathway).
    Select the benchmark(s) applicable to the pathway (component or
threat) being evaluated as specified in sections 3 through 6. Compare
the concentration of each hazardous substance from the sampling
location to its benchmark concentration(s) for that pathway (component
or threat). Use only those samples and only those hazardous substances
in the sample that meet the criteria for an observed release (or
observed contamination or observed exposure) for the pathway, except:
Tissue samples from aquatic human food chain organisms may be used as
specified in sections <IP_ADDRESS> and <IP_ADDRESS>. If the concentration of any
applicable hazardous substance from any sample equals or exceeds its
benchmark concentration, consider the sampling location to be subject
to Level I concentrations for that pathway (or threat). If more than
one benchmark applies to the hazardous substance, assign Level I if the
concentration of the hazardous substance equals or exceeds the lowest
applicable benchmark concentration.
    If no hazardous substance individually equals or exceeds its
benchmark concentration, but more than one hazardous substance either
meets the criteria for an observed release (or observed contamination
or observed exposure) for the sample (or comparable samples) or is
eligible to be evaluated for a tissue sample (see sections <IP_ADDRESS> and
<IP_ADDRESS>), calculate the indices I and J specified below based on these
hazardous substances.
    For those hazardous substances that are carcinogens (that is, those
having either a carcinogen weight-of-evidence classification of A, B,
or C or a weight-of-evidence classification of carcinogenic to humans,
likely to be carcinogenic to humans, or suggestive evidence of
carcinogenic potential), calculate an index I for the sample location
as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.031

Where:

Ci = Concentration of hazardous substance i in sample (or
highest concentration of hazardous substance i from among comparable
samples).
SCi = Screening concentration for cancer corresponding to
that concentration that corresponds to its 10-6
individual cancer risk for applicable exposure (inhalation or oral)
for hazardous substance i.
n = Number of applicable hazardous substances in sample (or
comparable

samples) that are carcinogens and for which an SCi is
available.

    For those hazardous substances for which an RfD or RfC is
available, calculate an index J for the sample location as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.032

Where:

Cj = Concentration of hazardous substance j in sample (or
highest concentration of hazardous substance j from among comparable
samples).
CRj = Screening concentration for noncancer toxicological
responses corresponding to RfD or RfC for applicable exposure
(inhalation or oral) for hazardous substance j.
m = Number of applicable hazardous substances in sample (or
comparable samples) for which a CRj is available.

    If either I or J equals or exceeds 1, consider the sampling
location to be subject to Level I concentrations for that pathway
(component or threat). If both I and J are less than 1, consider the
sampling location to be subject to Level II concentrations for that
pathway (component or threat). If, for the sampling location, there are
sets of samples that are not comparable, calculate I and J separately
for each such set, and use the highest calculated values of I and J to
assign Level I and Level II.
    See sections 7.3.1 and 7.3.2 for criteria for determining the level
of contamination for radioactive substances.
* * * * *

5.0 Soil Exposure and Subsurface Intrusion Pathway

    5.0. Exposure components. Evaluate the soil exposure and subsurface
intrusion pathway based on two exposure components:
     Soil exposure component (see section 5.1).
     Subsurface intrusion component (see section 5.2).
    Score one or both components considering their relative importance.
If only one component is scored, assign its score as the soil exposure
and subsurface intrusion pathway score. If both components are scored,
sum the two scores and assign it as the soil exposure and subsurface
intrusion pathway score, subject to a maximum of 100.

[GRAPHIC] [TIFF OMITTED] TP29FE16.033

    5.1 Soil exposure component. Evaluate the soil exposure component
based on two threats: Resident population threat and nearby population
threat. Evaluate both threats based on three factor categories:

Likelihood of exposure, waste characteristics, and targets. Figure 5-1
indicates the factors included within each factor category for each
type of threat.
    Determine the soil exposure component score (Sse) in
terms of the factor category values as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.034

Where:

LEi = Likelihood of exposure factor category value for
threat i (that is, resident population threat or nearby population
threat).
WCi = Waste characteristics factor category value for
threat i.
Ti = Targets factor category value for threat i.
SF = Scaling factor.

    Table 5-1 outlines the specific calculation procedure.

              Table 5-1--Soil Exposure Component Scoresheet
------------------------------------------------------------------------
                                                               Value
      Factor categories and factors       Maximum  value     assigned
------------------------------------------------------------------------
                       Resident Population Threat
------------------------------------------------------------------------
Likelihood of Exposure
    1. Likelihood of Exposure...........             550  ..............
Waste Characteristics
    2. Toxicity.........................           (\a\)  ..............
    3. Hazardous Waste Quantity.........           (\a\)  ..............
    4. Waste Characteristics............             100  ..............
Targets
    5. Resident Individual..............              50  ..............
    6. Resident Population:
    6a. Level I Concentrations                     (\b\)  ..............
    6b. Level II Concentrations                    (\b\)  ..............
    6c. Resident Population (lines 6a +            (\b\)  ..............
     6b)
    7. Workers..........................              15  ..............
    8. Resources........................               5  ..............
    9. Terrestrial Sensitive                         (c)  ..............
     Environments.......................
    10. Targets (lines 5 + 6c + 7 + 8 +            (\b\)  ..............
     9).................................
Resident Population Threat Score
    11. Resident Population Threat                 (\b\)  ..............
     (lines 1x4x10).....................
------------------------------------------------------------------------
                        Nearby Population Threat
------------------------------------------------------------------------
Likelihood of Exposure
    12. Attractiveness/Accessibility....             100  ..............
    13. Area of Contamination...........             100  ..............
    14. Likelihood of Exposure..........             500  ..............
Waste Characteristics
    15. Toxicity........................           (\a\)  ..............
    16. Hazardous Waste Quantity........           (\a\)  ..............
    17. Waste Characteristics...........             100  ..............
Targets
    18. Nearby Individual...............               1  ..............
    19. Population Within 1 Mile........           (\b\)  ..............
    20. Targets (lines 18 + 19).........           (\b\)  ..............
Nearby Population Threat Score
    21. Nearby Population Threat (lines            (\b\)  ..............
     14x17x20)..........................
Soil Exposure Component Score
    22. Soil Exposure Component Score                100  ..............
     \d\ (Sse), (lines [11+21]/82,500,
     subject to a maximum of 100).......
------------------------------------------------------------------------
\a\ Maximum value applies to waste characteristics category.
\b\ Maximum value not applicable.
\c\ No specific maximum value applies to factor. However, pathway score
  based solely on terrestrial sensitive environments is limited to
  maximum of 60.
\d\ Do not round to nearest integer.

    5.1.0  General considerations. Evaluate the soil exposure component
based on areas of observed contamination:
     Consider observed contamination to be present at sampling
locations where analytic evidence indicates that:

--A hazardous substance attributable to the site is present at a
concentration significantly above background levels for the site (see
Table 2-3 in section 2.3 for the criteria for determining analytical
significance), and
--This hazardous substance, if not present at the surface, is covered
by 2 feet or less of cover material (for example, soil).

     Establish areas of observed contamination based on
sampling locations at which there is observed contamination as follows:

--For all sources except contaminated soil, if observed contamination
from the site is present at any sampling location within the source,
consider that entire source to be an area of observed contamination.
-- For contaminated soil, consider both the sampling location(s) with
observed contamination from the site and the area lying between such
locations to be an area of observed contamination, unless available
information indicates otherwise.

     If an area of observed contamination (or portion of such
an area) is covered by a permanent, or otherwise maintained,
essentially

impenetrable material (for example, asphalt) that is not more than 2
feet thick, exclude that area (or portion of the area) in evaluating
the soil exposure component.
     For an area of observed contamination, consider only those
hazardous substances that meet the criteria for observed contamination
for that area to be associated with that area in evaluating the soil
exposure component (see section 2.2.2).
    If there is observed contamination, assign scores for the resident
population threat and the nearby population threat, as specified in
sections 5.1.1 and 5.1.2. If there is no observed contamination, assign
the soil exposure component of the soil exposure and subsurface
intrusion pathway a score of 0.
    5.1.1  Resident population threat. Evaluate the resident population
threat only if there is an area of observed contamination in one or
more of the following locations:
     Within the property boundary of a residence, school, or
day care center and within 200 feet of the respective residence,
school, or day care center, or
     Within a workplace property boundary and within 200 feet
of a workplace area, or
     Within the boundaries of a resource specified in section
<IP_ADDRESS>.4, or
     Within the boundaries of a terrestrial sensitive
environment specified in section <IP_ADDRESS>.5.
    If not, assign the resident population threat a value of 0, enter
this value in Table 5-1, and proceed to the nearby population threat
(section 5.1.2).
    <IP_ADDRESS> Likelihood of exposure. Assign a value of 550 to the
likelihood of exposure factor category for the resident population
threat if there is an area of observed contamination in one or more
locations listed in section 5.1.1. Enter this value in Table 5-1.
    <IP_ADDRESS> Waste characteristics. Evaluate waste characteristics based
on two factors: Toxicity and hazardous waste quantity. Evaluate only
those hazardous substances that meet the criteria for observed
contamination at the site (see section 5.1.0).
    <IP_ADDRESS>.1 Toxicity. Assign a toxicity factor value to each
hazardous substance as specified in section <IP_ADDRESS>. Use the hazardous
substance with the highest toxicity factor value to assign the value to
the toxicity factor for the resident population threat. Enter this
value in Table 5-1.
    <IP_ADDRESS>.2 Hazardous waste quantity. Assign a hazardous waste
quantity factor value as specified in section 2.4.2. In estimating the
hazardous waste quantity, use Table 5-2 and:
     Consider only the first 2 feet of depth of an area of
observed contamination, except as specified for the volume measure.
     Use the volume measure (see section <IP_ADDRESS>.3) only for
those types of areas of observed contamination listed in Tier C of
Table 5-2. In evaluating the volume measure for these listed areas of
observed contamination, use the full volume, not just the volume within
the top 2 feet.
     Use the area measure (see section <IP_ADDRESS>.4), not the
volume measure, for all other types of areas of observed contamination,
even if their volume is known.
    Enter the value assigned in Table 5-1.

    Table 5-2--Hazardous Waste Quantity Evaluation Equations for Soil
                           Exposure Component
------------------------------------------------------------------------
                                                         Equation for
     Tier              Measure             Units        assigning value
                                                              \a\
------------------------------------------------------------------------
A.............  Hazardous Constituent  lb...........  C
                 Quantity (C).
B \b\.........  Hazardous Wastestream  lb...........  W/5,000
                 Quantity (W).
C \b\.........  Volume (V)...........
                Surface Impoundment    yd \3\.......  V/2.5
                 \c\.
                Drums \d\............  gallon.......  V/500
                Tanks and Containers   yd \3\.......  V/2.5
                 Other Than Drums.
D \b\.........  Area (A).............
                Landfill.............  ft \2\.......  A/34,000
                Surface Impoundment..  ft \2\.......  A/13
                Surface Impoundment    ft \2\.......  A/13
                 (Buried/backfilled).
                Land treatment.......  ft \2\.......  A/270
                Pile \e\.............  ft \2\.......  A/34
                Contaminated Soil....  ft \2\.......  A/34,000
------------------------------------------------------------------------
\a\ Do not round nearest integer.
\b\ Convert volume to mass when necessary: 1 ton = 2,000 pounds = 1
  cubic yard = 4 drums = 200 gallons.
\c\ Use volume measure only for surface impoundments containing
  hazardous substances present as liquids. Use area measures in Tier D
  for dry surface impoundments and for buried/backfilled surface
  impoundments.
\d\ If actual volume of drums is unavailable, assume 1 drum = 50
  gallons.
\e\ Use land surface area under pile, not surface area of pile.

    <IP_ADDRESS>.3  Calculation of waste characteristics factor category
value. Multiply the toxicity and hazardous waste quantity factor
values, subject to a maximum product of 1 x 10\8\. Based on this
product, assign a value from Table 2-7 (section <IP_ADDRESS>) to the waste
characteristics factor category. Enter this value in Table 5-1.
    <IP_ADDRESS>  Targets. Evaluate the targets factor category for the
resident population threat based on five factors: Resident individual,
resident population, workers, resources, and terrestrial sensitive
environments.
    In evaluating the targets factor category for the resident
population threat, count only the following as targets:
     Resident individual--a person living or attending school
or day care on a property with an area of observed contamination and
whose residence, school, or day care center, respectively, is on or
within 200 feet of the area of observed contamination.
     Worker--a person working on a property with an area of
observed contamination and whose workplace area is on or within 200
feet of the area of observed contamination.
     Resources located on an area of observed contamination, as
specified in section 5.1.1.
     Terrestrial sensitive environments located on an area of
observed contamination, as specified in section 5.1.1.
    <IP_ADDRESS>.1  Resident individual. Evaluate this factor based on
whether

there is a resident individual, as specified in section <IP_ADDRESS>, who is
subject to Level I or Level II concentrations.
    First, determine those areas of observed contamination subject to
Level I concentrations and those subject to Level II concentrations as
specified in sections 2.5.1 and 2.5.2. Use the health-based benchmarks
from Table 5-3 in determining the level of contamination. Then assign a
value to the resident individual factor as follows:
     Assign a value of 50 if there is at least one resident
individual for one or more areas subject to Level I concentrations.
     Assign a value of 45 if there is no such resident
individuals, but there is at least one resident individual for one or
more areas subject to Level II concentrations.
     Assign a value of 0 if there is no resident individual.
    Enter the value assigned in Table 5-1.
    <IP_ADDRESS>.2 Resident population. Evaluate resident population based
on two factors: Level I concentrations and Level II concentrations.
Determine which factor applies as specified in sections 2.5.1 and
2.5.2, using the health-based benchmarks from Table 5-3. Evaluate
populations subject to Level I concentrations as specified in section
<IP_ADDRESS>.2.1 and populations subject to Level II concentrations as
specified in section <IP_ADDRESS>.2.2.

  Table 5-3--Health-Based Benchmarks for Hazardous Substances in Soils
------------------------------------------------------------------------

-------------------------------------------------------------------------
Screening concentration for cancer corresponding to that concentration
 that corresponds to the 10-\6\ individual cancer risk for oral
 exposures.
Screening concentration for noncancer toxicological responses
 corresponding to the Reference Dose (RfD) for oral exposures.
------------------------------------------------------------------------

    Count only those persons meeting the criteria for resident
individual as specified in section <IP_ADDRESS>. In estimating the number of
people living on property with an area of observed contamination, when
the estimate is based on the number of residences, multiply each
residence by the average number of persons per residence for the county
in which the residence is located.
    <IP_ADDRESS>.2.1 Level I concentrations. Sum the number of resident
individuals subject to Level I concentrations and multiply this sum by
10. Assign the resulting product as the value for this factor. Enter
this value in Table 5-1.
    <IP_ADDRESS>.2.2 Level II concentrations. Sum the number of resident
individuals subject to Level II concentrations. Do not include those
people already counted under the Level I concentrations factor. Assign
this sum as the value for this factor. Enter this value in Table 5-1.
    <IP_ADDRESS>.2.3 Calculation of resident population factor value. Sum
the factor values for Level I concentrations and Level II
concentrations. Assign this sum as the resident population factor
value. Enter this value in Table 5-1.
    <IP_ADDRESS>.3 Workers. Evaluate this factor based on the number of
workers that meet the section <IP_ADDRESS> criteria. Assign a value for
these workers using Table 5-4. Enter this value in Table 5-1.

                  Table 5-4--Factor Values for Workers
------------------------------------------------------------------------
                                                               Assigned