Number of workers                          value
------------------------------------------------------------------------
0...........................................................           0
1 to 100....................................................           5
101 to 1,000................................................          10
Greater than 1,000..........................................          15
------------------------------------------------------------------------

    <IP_ADDRESS>.4 Resources. Evaluate the resources factor as follows:
     Assign a value of 5 to the resources factor if one or more
of the following is present on an area of observed contamination at the
site:

--Commercial agriculture.
--Commercial silviculture.
--Commercial livestock production or commercial livestock grazing.
     Assign a value of 0 if none of the above are present.
    Enter the value assigned in Table 5-1.
    <IP_ADDRESS>.5 Terrestrial sensitive environments. Assign value(s) from
Table 5-5 to each terrestrial sensitive environment that meets the
eligibility criteria of section <IP_ADDRESS>.
    Calculate a value (ES) for terrestrial sensitive environments as
follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.035

where:
Si=Value(s) assigned from Table 5-5 to terrestrial
sensitive environment i.
n=Number of terrestrial sensitive environments meeting section
<IP_ADDRESS> criteria.

    Because the pathway score based solely on terrestrial sensitive
environments is limited to a maximum of 60, determine the value for the
terrestrial sensitive environments factor as follows:

       Table 5-5--Terrestrial Sensitive Environments Rating Values
------------------------------------------------------------------------
          Terrestrial sensitive environments             Assigned value
------------------------------------------------------------------------
Terrestrial critical habitat \a\ for Federal                         100
 designated endangered or threatened species.........
 National Park
 Designated Federal Wilderness Area
 National Monument
Terrestrial habitat known to be used by Federal                       75
 designated or proposed threatened or endangered
 species.............................................
 National Preserve (terrestrial)
 National or State Terrestrial Wildlife Refuge
 Federal land designated for protection of natural
 ecosystems
 Administratively proposed Federal Wilderness Area
 Terrestrial areas utilized for breeding by large or
 dense aggregations of animals \b\
Terrestrial habitat known to be used by State                         50
 designated endangered or threatened species.........
 Terrestrial habitat known to be used by species
 under review as to its Federal designated endangered
 or threatened status
State lands designated for wildlife or game                           25
 management..........................................
 State designated Natural Areas
 Particular areas, relatively small in size,
 important to maintenance of unique biotic
 communities
------------------------------------------------------------------------
\a\ Critical habitat as defined in 50 CFR 424.02.

\b\ Limit to vertebrate species.

     Multiply the values assigned to the resident population
threat for likelihood of exposure (LE), waste characteristics (WC), and
ES. Divide the product by 82,500.

--If the result is 60 or less, assign the value ES as the terrestrial
sensitive environments factor value.
--If the result exceeds 60, calculate a value EC as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.036

    Assign the value EC as the terrestrial sensitive environments
factor value. Do not round this value to the nearest integer.
    Enter the value assigned for the terrestrial sensitive environments
factor in Table 5-1.
    <IP_ADDRESS>.6 Calculation of resident population targets factor
category value. Sum the values for the resident individual, resident
population, workers, resources, and terrestrial sensitive environments
factors. Do not round to the nearest integer. Assign this sum as the
targets factor category value for the resident population threat. Enter
this value in Table 5-1.
    <IP_ADDRESS> Calculation of resident population threat score. Multiply
the values for likelihood of exposure, waste characteristics, and
targets for the resident population threat, and round the product to
the nearest integer. Assign this product as the resident population
threat score. Enter this score in Table 5-1.
    5.1.2 Nearby population threat. Include in the nearby population
only those individuals who live or attend school within a 1-mile travel
distance of an area of observed contamination at the site and who do
not meet the criteria for resident individual as specified in section
<IP_ADDRESS>.
    Do not consider areas of observed contamination that have an
attractiveness/accessibility factor value of 0 (see section <IP_ADDRESS>.1)
in evaluating the nearby population threat.
    <IP_ADDRESS> Likelihood of exposure. Evaluate two factors for the
likelihood of exposure factor category for the nearby population
threat: Attractiveness/accessibility and area of contamination.
    <IP_ADDRESS>.1 Attractiveness/accessibility. Assign a value for
attractiveness/accessibility from Table 5-6 to each area of observed
contamination, excluding any land used for residences. Select the
highest value assigned to the areas evaluated and use it as the value
for the attractiveness/accessibility factor. Enter this value in Table
5-1.
    <IP_ADDRESS>.2 Area of contamination. Evaluate area of contamination
based on the total area of the areas of observed contamination at the
site. Count only the area(s) that meet the criteria in section 5.1.0
and that receive an attractiveness/accessibility value greater than 0.
Assign a value to this factor from Table 5-7. Enter this value in Table
5-1.

             Table 5-6--Attractiveness/Accessibility Values
------------------------------------------------------------------------
             Area of observed contamination               Assigned value
------------------------------------------------------------------------
Designated recreational area............................             100
Regularly used for public recreation (for example,                    75
 fishing, hiking, softball).............................
Accessible and unique recreational area (for example,                 75
 vacant lots in urban area).............................
Moderately accessible (may have some access                           50
 improvements, for example, gravel road), with some
 public recreation use..................................
Slightly accessible (for example, extremely rural area                25
 with no road improvement), with some public recreation
 use....................................................
Accessible, with no public recreation use...............              10
Surrounded by maintained fence or combination of                       5
 maintained fence and natural barriers..................
Physically inaccessible to public, with no evidence of                 0
 public recreation use..................................
------------------------------------------------------------------------

             Table 5-7--Area of Contamination Factor Values
------------------------------------------------------------------------
    Total area of the areas of observed contamination
                      (square feet)                       Assigned value
------------------------------------------------------------------------
Less than or equal to 5,000.............................               5
Greater than 5,000 to 125,000...........................              20
Greater than 125,000 to 250,000.........................              40
Greater than 250,000 to 375,000.........................              60
Greater than 375,000 to 500,000.........................              80
Greater than 500,000....................................             100
------------------------------------------------------------------------

    <IP_ADDRESS>.3 Likelihood of exposure factor category value. Assign a
value from Table 5-8 to the likelihood of exposure factor category,
based on the values assigned to the attractiveness/accessibility and
area of contamination factors. Enter this value in Table 5-1.

                                            Table 5-8--Nearby Population Likelihood of Exposure Factor Values
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Attractiveness/accessibility factor value
   Area of contamination factor value    ---------------------------------------------------------------------------------------------------------------
                                                100             75              50              25              10               5               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
100.....................................             500             500             375             250             125              50               0
80......................................             500             375             250             125              50              25               0
60......................................             375             250             125              50              25               5               0
40......................................             250             125              50              25               5               5               0

20......................................             125              50              25               5               5               5               0
5.......................................              50              25               5               5               5               5               0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    <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 (see section 5.1.0) at areas that can be assigned an
attractiveness/accessibility factor value greater than 0.
    <IP_ADDRESS>.1 Toxicity. Assign a toxicity factor value as specified in
section <IP_ADDRESS> to each hazardous substance meeting the criteria in
section <IP_ADDRESS>. Use the hazardous substance with the highest toxicity
factor value to assign the value to the toxicity factor for the nearby
population threat. Enter this value in Table 5-1.
    <IP_ADDRESS>.2 Hazardous waste quantity. Assign a value to the hazardous
waste quantity factor as specified in section <IP_ADDRESS>.2, except:
Consider only those areas of observed contamination that can be
assigned an attractiveness/accessibility factor value greater than 0.
Enter the value assigned in Table 5-1.
    <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 factory category for the
nearby population threat based on two factors: Nearby individual and
population within a 1-mile travel distance from the site.
    <IP_ADDRESS>.1 Nearby individual. If one or more persons meet the
section <IP_ADDRESS> criteria for a resident individual, assign this factor
a value of 0. Enter this value in Table 5-1.
    If no person meets the criteria for a resident individual,
determine the shortest travel distance from the site to any residence
or school. In determining the travel distance, measure the shortest
overland distance an individual would travel from a residence or school
to the nearest area of observed contamination for the site with an
attractiveness/accessibility factor value greater than 0. If there are
no natural barriers to travel, measure the travel distance as the
shortest straight-line distance from the residence or school to the
area of observed contamination. If natural barriers exist (for example,
a river), measure the travel distance as the shortest straight-line
distance from the residence or school to the nearest crossing point and
from there as the shortest straight-line distance to the area of
observed contamination. Based on the shortest travel distance, assign a
value from Table 5-9 to the nearest individual factor. Enter this value
in Table 5-1.

               Table 5-9--Nearby Individual Factor Values
------------------------------------------------------------------------
   Travel distance for nearby  individual
                  (miles)                           Assigned value
------------------------------------------------------------------------
Greater than 0 to \1/4\....................  \a\1
Greater than \1/4\ to 1....................  0
------------------------------------------------------------------------
\a\ Assign a value of 0 if one or more persons meet the section <IP_ADDRESS>
  criteria for resident individual.

    <IP_ADDRESS>.2 Population within 1 mile. Determine the population within
each travel distance category of Table 5-10. Count residents and
students who attend school within this travel distance. Do not include
those people already counted in the resident population threat.
Determine travel distances as specified in section <IP_ADDRESS>.1.
    In estimating residential population, 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.
    Based on the number of people included within a travel distance
category, assign a distance-weighted population value for that travel
distance from Table 5-10.
    Calculate the value for the population within 1 mile factor (PN) as
follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.037

Where:

Wi = Distance-weighted population value from Table 5-10
for travel distance category i.

    If PN is less than 1, do not round it to the nearest integer; if PN
is 1 or more, round to the nearest integer. Enter this value in Table
5-1.
    <IP_ADDRESS>.3 Calculation of nearby population targets factor category
value. Sum the values for the nearby individual factor and the
population within 1 mile factor. Do not round this sum to the nearest
integer. Assign this sum as the targets factor category value for the
nearby population threat. Enter this value in Table 5-1.

                                                         Table 5-10--Distance Weighted Population Values for Nearby Population Threat a
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Number of people within the travel distance category
                                     -----------------------------------------------------------------------------------------------------------------------------------------------------------
  Travel distance category  (miles)                                                                       301 to      1,001 to     3,001 to    10,001 to    30,001 to    100,001 to   300,001 to
                                           0         1 to 10      11 to 30    31 to 100    101 to 300     1,000        3,000        10,000       30,000      100,000      300,000     1,000,000
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Greater than 0 to \1/4\.............            0          0.1          0.4          1.0            4           13           41          130          408        1,303        4,081       13,034
Greater than \1/4\ to \1/2\.........            0         0.05          0.2          0.7            2            7           20           65          204          652        2,041        6,517
Greater than \1/2\ to 1.............            0         0.02          0.1          0.3            1            3           10           33          102          326        1,020        3,258
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Round the number of people present within a travel distance category to nearest integer. Do not round the assigned distance-weighted population value to nearest integer.

    <IP_ADDRESS> Calculation of nearby population threat score. Multiply the
values for likelihood of exposure, waste characteristics, and targets
for the nearby population threat, and round the product to the nearest
integer. Assign this product as the nearby population threat score.
Enter this score in Table 5-1.
    5.1.3 Calculation of soil exposure component score. Sum the
resident population threat score and the nearby population threat
score, and divide the sum by 82,500. Assign the resulting value,
subject to a maximum of 100, as the soil exposure component score
(Sse). Enter this score in Table 5-1.
    5.2 Subsurface intrusion component. Evaluate the subsurface
intrusion component based on three factor categories: Likelihood of
exposure, waste characteristics, and targets. Figure 5-1 indicates the
factors included within each factor category for the subsurface
intrusion component.
    Determine the component score (Sssi) in terms of the
factor category values as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.038

Where:
LE = Likelihood of exposure factor category value.
WC = Waste characteristics factor category value.
T = Targets factor category value.
SF = Scaling factor.

    Table 5-11 outlines the specific calculation procedure.

          Table 5-11--Subsurface Intrusion Component Scoresheet
------------------------------------------------------------------------
      Factor categories and factors        Maximum value  Value assigned
------------------------------------------------------------------------
                     Subsurface Intrusion Component
------------------------------------------------------------------------
Likelihood of Exposure:
    1. Observed Exposure                             550
    2. Potential for Exposure:
        2a. Structure Containment.......              10
        2b. Depth to contamination......              10
        2c. Vertical Migration..........              15
        2d. Vapor Migration Potential...              25
    3. Potential for Exposure (lines 2a              500
     * (2b + 2c + 2d), subject to a
     maximum of 500)....................
    4. Likelihood of Exposure (higher of             550
     lines 1 or 3)......................
Waste Characteristics:
    5. Toxicity/Degradation.............           \(a)\
    6. Hazardous Waste Quantity.........           \(a)\
    7. Waste Characteristics (subject to             100
     a maximum of 100)..................
Targets:
    8. Exposed Individual...............              50
    9. Population:......................
        9a. Level I Concentrations......           \(b)\
        9b. Level II Concentrations.....           \(b)\
        9c. Population within an Area of           \(b)\
         Subsurface Contamination.......
        9d. Total Population (lines 9a +           \(b)\
         9b + 9c).......................
    10. Resources.......................               5
    11. Targets (lines 8 + 9d + 10).....           \(b)\
Subsurface Intrusion Component Score:
    12. Subsurface Intrusion Component               100
     (lines 4 x 7 x 11)/82,500 \c\
     (subject to a maximum of 100)......
Soil Exposure and Subsurface Intrusion
 Pathway Score:
    13. Soil Exposure Component +                    100
     Subsurface Intrusion Component
     (subject to a maximum of 100)......
------------------------------------------------------------------------
\a\ Maximum value applies to waste characteristics category.
\b\ Maximum value not applicable.
\c\ Do not round to the nearest integer.

    5.2.0--General considerations. The subsurface intrusion component
evaluates the threats from hazardous substances that have or could
intrude into regularly occupied structures via surficial ground water
or the unsaturated zone. Evaluate the subsurface intrusion component
based on the actual or potential intrusion of hazardous substances into
a regularly occupied structures that has structure containment value
greater than zero; or actual or potential intrusion of hazardous
substances exists in the unsaturated zone or the surficial ground water
below the regularly occupied structures. These structures may or may
not have subunits. Subunits are partitioned areas within a structure
with separate heating, ventilating, and air conditioning (HVAC) systems
or distinctly different air exchange rates. Subunits include regularly
occupied partitioned tenant spaces such as office suites, apartments,
condos, common or shared areas, and portions of residential, commercial
or industrial structures with separate heating, ventilating, and air
conditioning (HVAC) systems.
    In evaluating the subsurface intrusion component, consider the
following:
     Area(s) of observed exposure: An area of observed exposure
is delineated by regularly occupied structures with documented
contamination meeting observed exposure criteria; an area of observed
exposure includes regularly occupied structures with samples meeting
observed exposure criteria or inferred to be within an area of observed
exposure based on samples meeting observed exposure criteria (see
section <IP_ADDRESS>.1 Observed Exposure). Establish areas of observed
exposure as follows:

--For regularly occupied structures that have no subunits, consider
both the regularly occupied structures containing sampling location(s)
meeting observed exposure criteria for the site and the regularly
occupied structure(s) in the area lying between such locations to be an
area of observed exposure (i.e., inferred to be in an area of observed
exposure), unless available information indicates otherwise.

--In multi-story, multi-subunit, regularly occupied structures,
consider all subunits on a level with sampling locations meeting
observed exposure criteria from the site and all levels below, if any,
to be within an area of observed exposure, unless available information
indicates otherwise.
--In multi-tenant structures, that do not have a documented observed
exposure, but are located in an area lying between locations where
observed exposures have been documented, consider only those regularly
occupied subunits, if any, on the lowest level of the structure, to be
within an area of observed exposure (i.e., inferred to be in an area of
observed exposure, unless available information indicates otherwise.

     Area(s) of subsurface contamination: An area of subsurface
contamination is delineated by sampling locations meeting observed
release criteria for subsurface intrusion, excluding areas of observed
exposure (see Table 2-3 in section 2.3). The area within an area of
subsurface contamination includes potentially exposed populations. If
the significant increase in hazardous substance levels cannot be
attributed at least in part to the site and cannot be attributed to
other sites, attribution can be established based on the presence of
hazardous substances in the area of subsurface contamination. Establish
areas of subsurface contamination as follows:

-- Exclude those areas that contain structures meeting the criteria
defined as an area of observed exposure.
-- Consider both the sampling location(s) with subsurface contamination
meeting observed release criteria from the site and the area lying
between such locations to be an area of subsurface contamination (i.e.,
inferred to be in an area of subsurface contamination), unless
available information indicates otherwise.
-- Evaluate an area of subsurface contamination based on hazardous
substances that:

[ssquf] Meet the criteria for observed exposure, or
[ssquf] Meet the criteria for observed release in an area of subsurface
contamination and have 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] 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.

    See Section 7.0 for establishing an area of subsurface
contamination based on the presence of radioactive hazardous
substances.

-- Evaluate all structures with no subunits to be in an area of
subsurface contamination if they are lying between locations of
subsurface intrusion samples meeting observed release criteria.
-- Evaluate multi-subunit structures as follows:

[ssquf] If an observed exposure has been documented based on a gaseous
indoor air sample, consider all regularly occupied subunit(s), if any,
on the level immediately above the level where an observed exposure has
been documented (or has been inferred to be within an area of observed
exposure), to be within an area of subsurface contamination, unless
available information indicates otherwise.
[ssquf] If observed release criteria have been met based on a gaseous
indoor air sample collected from a level not regularly occupied,
consider all regularly occupied subunit(s), if any, on the level
immediately above the level where the observed release criteria has
been documented, to be within an area of subsurface contamination,
unless available information indicates otherwise.
[ssquf] If an observed exposure has been documented based on an
intruded liquid or particulate sample, do not consider any regularly
occupied subunit(s) above the level where an observed exposure has been
documented to be within an area of subsurface contamination, unless
available information indicates otherwise.
[ssquf] If any regularly occupied multi-subunit structure is inferred
to be in an area of subsurface contamination, consider only those
regularly occupied subunit(s), if any, on the lowest level, to be
within an area of subsurface contamination, unless available
information indicates otherwise.

    If there is no area of observed exposure and no area of subsurface
contamination, assign a score of 0 for the subsurface intrusion
component.
    5.2.1 Subsurface intrusion component. Evaluate this component only
if there is an area of observed exposure or area of subsurface
contamination:
     Within or underlying a residence, school, day care center,
workplace, or
     Within or underlying a resource specified in section
<IP_ADDRESS>.3.
    <IP_ADDRESS> Likelihood of exposure. Assign a value of 550 to the
likelihood of exposure factor category for the subsurface intrusion
component if there is an area of observed exposure in one or more
locations listed in section 5.2.1. Enter this value in Table 5-11.
    <IP_ADDRESS>.1 Observed exposure. Establish observed exposure in a
regularly occupied structure by demonstrating that a hazardous
substance has been released into a regularly occupied structure via the
subsurface. Base this demonstration on either of the following
criterion:
     Direct observation:

-- A solid, liquid or gaseous material that contains one or more
hazardous substances attributable to the site has been observed
entering a regularly occupied structure through migration via the
subsurface or is known to have entered a regularly occupied structure
via the subsurface, or
-- When evidence supports the inference of subsurface intrusion of a
material that contains one or more hazardous substances associated with
the site into a regularly occupied structure, demonstrated adverse
effects associated with that release may be used to establish observed
exposure.

     Chemical analysis:

-- Analysis of indoor samples indicates that the concentration of
hazardous substance(s) has increased significantly above the background
concentration for the site for that type of sample (see section 2.3).
-- Some portion of the significant increase must be attributable to the
site to establish the observed exposure. Documentation of this
attribution should account for possible concentrations of the hazardous
substance(s) in outdoor air or from materials found in the regularly
occupied structure, and should provide a rationale for the increase
being from subsurface intrusion.

    If observed exposure can be established in a regularly occupied
structure, assign an observed exposure factor value of 550, enter this
value in Table 5-11, and proceed to section <IP_ADDRESS>.3. If no observed
exposure can be established, assign an observed exposure factor value
of 0, enter this value in Table 5-11, and proceed to section <IP_ADDRESS>.2.
    <IP_ADDRESS>.2 Potential for exposure. Evaluate potential for exposure
only if an observed exposure cannot be

established, but an area of subsurface contamination has been
delineated. Evaluate potential for exposure based only on the presence
of 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. Evaluate potential for exposure for each area of subsurface
contamination based on four factors: structure containment (see section
<IP_ADDRESS>.2.1), depth to contamination (see section <IP_ADDRESS>.2.2),
vertical migration (see section <IP_ADDRESS>.2.3) and vapor migration
potential (see section <IP_ADDRESS>.2.4). For each area of subsurface
contamination, assign the highest value for each factor. If information
is insufficient to calculate any single factor value used to calculate
the potential for exposure factor values at an identified area of
subsurface contamination, information collected for another area of
subsurface contamination at the site may be used when evaluating
potential for exposure. Calculate the potential for exposure value for
the site as specified in section <IP_ADDRESS>.2.5.
    <IP_ADDRESS>.2.1 Structure containment. Calculate containment for
eligible hazardous substances within this component as directed in
Table 5-12 and enter this value into Table 5-11. Assign each regularly
occupied structure within an area of subsurface contamination the
highest appropriate structure containment value from Table 5-12 and use
the regularly occupied structure at the site with the highest structure
containment value in performing the potential for exposure calculation.
Assign a structure containment factor value of 10 to any regularly
occupied structure located within an area of observed exposure that is
established based on documented surficial ground water intrusion,
unless available information indicates otherwise.

                    Table 5-12--Structure Containment
------------------------------------------------------------------------
                                Evidence of structure
            No.                      containment          Assigned value
------------------------------------------------------------------------
1.........................  Regularly occupied structure              10
                             with evidence of subsurface
                             intrusion, including
                             documented observed
                             exposure or sampling of bio
                             or inert gases, such as
                             methane and radon.
2.........................  Regularly occupied structure              10
                             with open preferential
                             pathways from the
                             subsurface (e.g., sumps,
                             foundation cracks, unsealed
                             utility lines).
3.........................  Regularly occupied structure               7
                             with an engineered vapor
                             migration barrier system
                             that does not address all
                             preferential pathways.
4.........................  Regularly occupied structure               6
                             with an engineered passive
                             vapor mitigation system
                             without documented
                             institutional controls
                             (e.g., deed restrictions)
                             or evidence of regular
                             maintenance and inspection.
5.........................  Regularly occupied structure               4
                             with no visible open
                             preferential pathways from
                             the subsurface (e.g.,
                             sumps, foundation cracks,
                             unsealed utility lines).
6.........................  Regularly occupied structure               3
                             with an engineered passive
                             vapor mitigation system
                             (e.g., passive venting)
                             with documented
                             institutional controls
                             (e.g., deed restrictions)
                             or evidence of regular
                             maintenance and inspection.
7.........................  Regularly occupied structure               2
                             with an engineered, active
                             vapor mitigation system
                             (e.g., active venting)
                             without documented
                             institutional controls
                             (e.g., deed restrictions)
                             and funding in place for on-
                             going operation, inspection
                             and maintenance.
8.........................  Regularly occupied structure               2
                             with unknown containment
                             features.
9.........................  Regularly occupied structure               0
                             with a permanent
                             engineered, active vapor
                             mitigation system (e.g.,
                             active venting) with
                             documented institutional
                             controls (e.g., deed
                             restrictions) and funding
                             in place for on-going
                             operation, inspection and
                             maintenance. This does not
                             include mitigation systems
                             installed as part of a
                             removal or other temporary
                             response by federal, state
                             or tribal authorities.
10........................  Regularly occupied structure               0
                             with a foundation raised
                             greater than 6 feet (e.g.,
                             structure on stilts) or
                             structure that has been
                             built, and maintained, in a
                             manner to prevent
                             subsurface intrusion.
------------------------------------------------------------------------

    <IP_ADDRESS>.2.2 Depth to contamination. Assign each area of subsurface
contamination a depth to contamination based on the least depth to
either contaminated crawl space or subsurface media underlying a
regularly occupied structure. Measure this depth to contamination based
on the distance between the lowest point of a regularly occupied
structure to the highest known point of hazardous substances eligible
to be evaluated. Use any regularly occupied structure within an area of
subsurface contamination with a structure containment factor greater
than zero. Subtract from the depth to contamination the thickness of
any subsurface layer composed of features that would allow channelized
flow (e.g., karst, lava tubes, open fractures).
    Based on this calculated depth, assign a factor value from Table 5-
13. If the necessary information is available at multiple locations,
calculate the depth to contamination at each location. Use the location
having the least depth to contamination to assign the factor value.
Enter this value in Table 5-11.

                   Table 5-13--Depth to Contamination
------------------------------------------------------------------------
                                                             Depth to
                     Depth range 1 2                       contamination
                                                          assigned value
------------------------------------------------------------------------
0 to 10 ft.(Including subslab and semi-enclosed or                    10
 enclosed crawl space contamination)....................
>10 to 20 ft............................................               8
>20 to 50 ft............................................               6
>50 to 100 ft...........................................               4
>100 to 150 ft..........................................               2
>150 ft.................................................               0
------------------------------------------------------------------------
\1\ If any part of the subsurface profile has channelized flow features,
  assign that portion of the subsurface profile a depth of 0.
\2\ Measure elevation below any regularly occupied structure within an
  area of subsurface contamination at a site. Select the regularly
  occupied structure with the least depth to contamination below a
  structure.

    <IP_ADDRESS>.2.3 Vertical migration. Evaluate the vertical migration
factor for each area of subsurface contamination based on the geologic
materials in the interval between the lowest point of a regularly
occupied structure and the highest known point of hazardous substances
in the subsurface. Use any regularly occupied structure either within
an area of subsurface contamination or overlying subsurface soil gas or
ground water contamination. Assign a value to the vertical migration
factor as follows:
     If the depth to contamination (see section <IP_ADDRESS>.2.2) is
10 feet or less, assign a value of 15.

     Do not consider layers or portions of layers within the
first 10 feet of the depth to contamination.
     If, for the interval identified above, all layers that
underlie a portion of a regularly occupied structure at the site are
karst or otherwise allow channelized flow, assign a value of 15.
     Otherwise:

--Select the lowest effective porosity/permeability layer(s) from
within the above interval. Consider only layers at least 1 foot thick.
(If site-specific data is not available, use the layer with the highest
value assigned in Table 5-14.)
--Assign a value for individual layers from Table 5-14.
--If more than one layer has the same assigned porosity/permeability
value, include all such layers and sum their thicknesses. Assign a
thickness of 0 feet to a layer with channelized flow features found
within any area of subsurface contamination at the site.
--Assign a value from Table 5-15 to the vertical migration factor,
based on the thickness and assigned porosity/permeability value of the
lowest effective porosity/permeability layer(s).

    Determine vertical migration only at locations within an area of
subsurface contamination at the site. If the necessary subsurface
geologic information is available at multiple locations, evaluate the
vertical migration factor at each location. Use the location having the
highest vertical migration factor value to assign the factor value.
Enter this value in Table 5-11.

    Table 5-14--Effective Porosity/Permeability of Geologic Materials
------------------------------------------------------------------------
                                                             Assigned
                                                             porosity/
                    Type of material                       permeability
                                                               value
------------------------------------------------------------------------
Gravel; highly permeable fractured igneous and                         1
 metamorphic rocks; permeable basalt; karst limestones
 and dolomites..........................................
Sand; sandy clays; sandy loams; loamy sands; sandy                     2
 silts; sediments that are predominantly sand; highly
 permeable till (coarse-grained, unconsolidated or
 compact and highly fractured); peat; moderately
 permeable limestones and dolomites (no karst);
 moderately permeable sandstone; moderately permeable
 fractured igneous and metamorphic rocks................
Silt; loams; silty loams; loesses; silty clays;                        3
 sediments that are predominantly silts; moderately
 permeable till (fine-grained, unconsolidated till, or
 compact till with some fractures); low permeability
 limestones and dolomites (no karst); low permeability
 sandstone; low permeability fractured igneous and
 metamorphic rocks......................................
Clay; low permeability till (compact unfractured till);                4
 shale; unfractured metamorphic and igneous rocks.......
------------------------------------------------------------------------

                                                      Table 5-15 Vertical Migration Factor Values a
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Thickness of lowest porosity layer(s) \b\ (feet)
                                                         -----------------------------------------------------------------------------------------------
          Assigned porosity/ permeability value                           Greater than 5   Greater than    Greater than    Greater than    Greater than
                                                              0 to 5           to 10         10 to 20        20 to 50        50 to 100      100 to 150
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................................              15              15              14              11               8               6
2.......................................................              15              14              12               9               6               4
3.......................................................              15              13              10               7               5               2
4.......................................................              15              12               9               6               3               1
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ If depth to contamination is 10 feet or less or if, for the interval being evaluated, all layers that underlie a portion of the structure at the
  site are karst or have other channelized flow features, assign a value of 15.
\b\ Consider only layers at least 1 foot thick.

    <IP_ADDRESS>.2.4 Vapor migration potential. Evaluate this factor for
each area of subsurface contamination as follows:
     If the depth to contamination (see section <IP_ADDRESS>.2.2) is
10 feet or less, assign a value of 25.
     Assign a value for vapor migration potential to each of
the gaseous hazardous substances associated with the area of subsurface
contamination (see section 2.2.2) as follows:

--Assign values from Table 5-16 for both vapor pressure and Henry's
constant to each hazardous substance. If Henry's constant cannot be
determined for a hazardous substance, assign that hazardous substance a
value of 2 for the Henry's constant component.
--Sum the two values assigned to each hazardous substance.
--Based on this sum, assign each hazardous substance a value from Table
5-17 for vapor migration potential.

     Assign a value for vapor migration potential to each area
of subsurface contamination as follows:

--Select the hazardous substance associated with the area of subsurface
contamination with the highest vapor migration potential value and
assign this value as the vapor migration potential factor for the area
of subsurface contamination.

    Enter this value in Table 5-11.

       Table 5-16--Values for Vapor Pressure and Henry's Constant
------------------------------------------------------------------------
                  Vapor pressure (Torr)                   Assigned value
------------------------------------------------------------------------
Greater than 10.........................................               3
1 to 10.................................................               2
Less than 1.............................................               0
------------------------------------------------------------------------
             Henry's constant (atm-m\3\/mol)              Assigned value
------------------------------------------------------------------------
Greater than 10-\3\.....................................               3
Greater than 10-\4\ to 10-\3\...........................               2
10-\5\ to 10-\4\........................................               1
Less than 10-\5\........................................               0
------------------------------------------------------------------------

   Table 5-17--Vapor Migration Potential Factor Values for a Hazardous
                                Substance
------------------------------------------------------------------------
  Sum of values for vapor pressure and Henry's constant   Assigned value
------------------------------------------------------------------------
0.......................................................               0
1 or 2..................................................               5
3 or 4..................................................              15
5 or 6..................................................              25
------------------------------------------------------------------------

    <IP_ADDRESS>.2.5 Calculation of potential for exposure factor value. For
each identified area of subsurface contamination, sum the factor values
for depth to contamination, vertical migration and vapor migration
potential, and multiply this sum by the factor value for structure
containment. Select the highest product for any area of subsurface
contamination and assign this value as the potential for exposure
factor value for the component. Enter this value in Table 5-11.
    <IP_ADDRESS>.3 Calculation of likelihood of exposure factor category
value. If observed exposure is established for the site, assign the
observed exposure factor value of 550 as the likelihood of exposure
factor category value for the site. Otherwise, assign the potential for
exposure factor value for the component as the likelihood of exposure
value. Enter the value assigned in Table 5-11.
    <IP_ADDRESS> Waste characteristics. Evaluate waste characteristics based
on two factors: Toxicity/degradation and hazardous waste quantity.
    <IP_ADDRESS>.1 Toxicity/degradation. For each hazardous substance,
assign a toxicity factor value, a degradation factor value and a
combined toxicity/degradation factor value as specified in sections
2.2.3, <IP_ADDRESS> and <IP_ADDRESS>.1.1 through <IP_ADDRESS>.1.3.
    <IP_ADDRESS>.1.1 Toxicity. Assign a toxicity factor value to each
hazardous substance as specified in sections 2.2.2 and <IP_ADDRESS>.
    <IP_ADDRESS>.1.2 Degradation. Assign a degradation factor value to each
hazardous substance as follows:
     For any hazardous substance that meets the criteria for an
observed exposure, assign that substance a degradation factor value of
1.
     For all hazardous substances at the site that meet
subsurface intrusion observed release criteria but not observed
exposure criteria, assign a degradation factor value of 1 if the depth
to contamination below an area of subsurface contamination or area of
observed exposure is less than 10 feet or if available evidence
suggests that there is less than 10 feet of biologically active soil in
the subsurface anywhere underneath a regularly occupied structure
within an area of subsurface contamination or area of observed
exposure.
    For all other situations first calculate the half-life for each
hazardous substance that meets subsurface intrusion observed release
criteria as follows:
    The half-life or a substance in the subsurface is defined for HRS
purposes as the time required to reduce the initial concentration in
the subsurface by one-half as a result of the combined decay processes
of two components: biodegradation and hydrolysis.
    Estimate the half-life (t1/2) of a hazardous substance
as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.039

Where:

h=Hydrolysis half-life.
b=Biodegradation half-life.

    If one of these component half-lives cannot be estimated for the
hazardous substance from available data, delete that component half-
life from the above equation.
    If no half-life information is available for a hazardous substance
and the substance is not already assigned a value of 1, unless
information indicates otherwise, all straight-chain and simple-ring
structure substances will be considered to have a half-life less than
30 days if not the hazardous substance will be assigned a half-life of
greater than 100 days.
    Based on the hazardous substance's assigned half-life the
degradation factor is assigned as follows:
     For all hazardous substances at the site that meet
subsurface intrusion observed release criteria but not observed
exposure criteria, assign a degradation factor value of 0.1, if:

--The depth to contamination at the site is greater than or equal to 10
feet, but not if available evidence suggests that at least 10 feet of
biologically active soil is not present in the subsurface anywhere
underneath a structure within an area of subsurface contamination or
area of observed exposure, and
--The hazardous substance has a half-life of 30 days or less.

     For all hazardous substances at the site that meet
subsurface intrusion observed release criteria but not observed
exposure criteria, assign a degradation factor value of 0.5, if:

--The depth to contamination at the site is greater than 30 feet, but
not if available evidence suggests that at least 30 feet of
biologically active soil is not present in the subsurface anywhere
underneath a structure within an area of subsurface contamination or
area of observed exposure, and
--The hazardous substance has a half-life equal to or less than 100
days.

     For all other situations assign a degradation factor of 1
for all hazardous substances at the site that meet subsurface intrusion
observed release criteria.
    In addition, for hazardous substances that meet observed release
criteria, have a parent-daughter degradation relationship, and the
daughter substance is found only in samples with a depth greater than
10 feet, assign the daughter substance degradation factor value as
follows:
    1. Identify the shallowest subsurface sample that contains the
daughter substance.
    2. Determine if the selected sample or another sample from the same
relative position in the media of concern, or in a shallower sample,
contains the parent substance.
    3. If the parent substance is not present in the identified
samples, assign the degradation factor value for the daughter substance
based on the half-life for the daughter substance.
    4. If the parent substance is present in a sample from the same
relative position in the subsurface or in a shallower sample, compare
the half-life-based degradation factor value for the daughter substance
to the degradation factor value assigned to the parent substance.
Assign the greater of the two values as the degradation factor value
for the daughter substance.
    <IP_ADDRESS>.1.3 Calculation of toxicity/degradation factor value.
Assign each substance a toxicity/biodegradation value by multiplying
the toxicity factor value by the degradation factor value. Use the
hazardous substance with the highest combined toxicity/degradation
value to assign the factor value to the toxicity/degradation factor for
the subsurface intrusion threat. Enter this value in Table 5-11.
    <IP_ADDRESS>.2 Hazardous waste quantity. Assign a hazardous waste
quantity factor value as specified in section 2.4.2. Consider only
those regularly occupied structures with a non-zero structure
containment value. In estimating the hazardous waste quantity, use
Tables 2-5 and 5-18 and:
     For Tier A, hazardous constituent quantity, use the mass
of constituents found in the regularly occupied structure(s) where the
observed exposure has been identified.

--For multi-subunit structures, when calculating Tier A, use the mass
of

constituents found in the regularly occupied subunit space(s) where the
observed exposure has been identified.

     For Tier B, hazardous wastestream quantity, use the flow-
through volume of the regularly occupied structures where the observed
exposure has been identified.

--For multi-subunit structures, when calculating Tier B, use the flow-
through volume of the regularly occupied subunit spaces where the
observed exposure has been identified.

     For Tier C, volume, use the volume divisor listed in Tier
C of Table 5-18. Volume is calculated for those regularly occupied
structures located within areas of observed exposure with observed or
inferred intrusion and within areas of subsurface contamination.

--In evaluating the volume measure for these listed areas of observed
exposure and areas of subsurface contamination based on a gaseous/vapor
intrusion or the potential for gaseous/vapor intrusion, consider the
following:

     Calculate the volume of each regularly occupied structure
based on actual data. If unknown, use a ceiling height of 8 feet.
     For multi-subunit structures, when calculating Tier C,
calculate volume for those subunit spaces with observed or inferred
exposure and all other regularly occupied subunit spaces on that level,
unless available information indicates otherwise. If the structure has
multiple stories, also include the volume of all regularly occupied
subunit spaces below the floor with an observed exposure and one story
above, unless evidence indicates otherwise.
     For multi-subunit structures within an area of subsurface
contamination and no observed or inferred exposure, consider only the
volume of the regularly occupied subunit spaces on the lowest story,
unless available information indicates otherwise.

--In evaluating the volume measure for these listed areas of observed
exposure and areas of subsurface contamination where intrusion of
contaminated ground water has occurred, do not calculate the volume of
each regularly occupied structure. Instead, consider only the volume of
contaminated ground water known to have intruded into a regularly
occupied structure.

     For Tier D, area, if volume is unknown, use the area
divisor listed in Tier D of Table 5-18 for those regularly occupied
structures within areas of observed exposure with observed or inferred
intrusion and within areas of subsurface contamination. In evaluating
the area measure for these listed areas of observed exposure and areas
of subsurface contamination, calculate the area of each regularly
occupied structure (including multi-subunit structures) based on actual
footprint area data. If the actual footprint area of the structure(s)
is unknown, use an area of 1,740 square feet for each structure (or
subunit space).

Table 5-18--Hazardous Waste Quantity Evaluation Equations for Subsurface
                           Intrusion 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 c        Volume (V).
------------------------------------------------------------------------
             Regularly occupied       yd \3\.........  V/2.5.
              structure(s) in areas
              of observed exposure
              or subsurface
              contamination.
------------------------------------------------------------------------
D b d        Area (A).
------------------------------------------------------------------------
             Regularly occupied       ft \2\.........  A/13.
              structure(s) in areas
              of observed exposure
              or subsurface
              contamination.
------------------------------------------------------------------------
\a\ Do not round to the nearest integer.
\b\ Convert volume to mass when necessary: 1 ton = 2,000 pounds = 1
  cubic yard = 4 drums = 200 gallons.
\c\ Calculate volume of each regularly occupied structure or subunit
  space in areas of observed exposure and areas of subsurface
  contamination--Assume 8-foot ceiling height unless actual value is
  known.
\d\ Calculate area of the footprint of each regularly occupied structure
  in areas of observed exposure and areas of subsurface contamination.
  If the footprint area of a regularly occupied structure is unknown,
  use 1,740 square feet as the footprint area of the structure or
  subunit space.

    For the subsurface intrusion component, 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 or if
one or more areas of subsurface contamination are present, 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 that does not permanently interrupt target
exposure from subsurface intrusion, 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 minimum value of 10.
    Enter the value assigned in Table 5-11.

    <IP_ADDRESS>.3 Calculation of waste characteristics factor category
value. Multiply the toxicity/degradation 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 5-11.
    <IP_ADDRESS> Targets. Evaluate the targets factor category for the
subsurface intrusion threat based on three factors: Exposed individual,
population, and resources in regularly occupied structures. Evaluate
only those targets within areas of observed exposure and areas of
subsurface contamination (see section 5.2.0).
    In evaluating the targets factor category for the subsurface
intrusion threat, count only the following as targets:
     Exposed individual--a person living, attending school or
day care, or working in a regularly occupied structure with observed
exposure or in a structure within an area of observed exposure or
within an area of subsurface contamination.
     Population--exposed individuals in a regularly occupied
structure within an area of observed exposure or within an area of
subsurface contamination.
     Resources--located within an area of observed exposure or
within an area of subsurface contamination as specified in section
<IP_ADDRESS>.3.
    If a former structure that has been vacated due to subsurface
intrusion attributable to the site, count the initial targets as if
they were still residing in the structure. In addition, if a removal
action has occurred that has not completely mitigated the release,
count the initial targets as if the removal action has not permanently
interrupted target exposure from subsurface intrusion.
    For populations residing in or working in a multi-subunit structure
with multiple stories in an area of observed exposure or area of
subsurface contamination, count these targets as follows:
     If there is no observed exposure within the structure,
include in the evaluation only those targets, if any, in the lowest
occupied level, unless available information indicates otherwise.
     If there is an observed exposure in any level, include in
the evaluation those targets in that level, the level above and all
levels below, unless available information indicates otherwise. (The
weighting of these targets is specified in Section <IP_ADDRESS>.2.)
    <IP_ADDRESS>.1 Exposed individual. Evaluate this factor based on whether
there is an exposed individual, as specified in sections 2.5.1, 2.5.2
and <IP_ADDRESS>, who is subject to Level I or Level II concentrations.
    First, determine those regularly occupied structures or partitioned
subunit(s) within structures in an area of observed exposure subject to
Level I concentrations and those subject to Level II concentrations as
specified as follows (see section 5.2.0):
     Level I Concentrations: For contamination resulting from
subsurface intrusion, compare the hazardous substance concentrations in
any sample meeting the observed exposure by chemical analysis criteria
to the appropriate benchmark. Use the health-based benchmarks from
Table 5-19 to determine the level of contamination.

--If the sample is from a structure with no subunits and the
concentration equals or exceeds the appropriate benchmark, assign Level
I concentrations to the entire structure.
--If the sample is from a subunit within a structure and the
concentration from that subunit equals or exceeds the appropriate
benchmark, assign Level I concentrations to that subunit.

     Level II Concentrations: Structures, or subunits within
structures, with one or more samples that meet observed exposure by
chemical analysis criteria but do not equal or exceed the appropriate
benchmark; structures, or subunits, that have an observed exposure by
direct observation; and structures inferred to be in an area of
observed exposure based on samples meeting observed exposure, are
assigned Level II concentrations.
    [cir] For all regularly occupied structures, or subunits in such
structures, in an area of observed exposure that are not assigned Level
I concentrations, assign Level II concentrations.
    Then assign a value to the exposed individual factor as follows:
     Assign a value of 50 if there is at least one exposed
individual in one or more regularly occupied structures subject to
Level I concentrations.
     Assign a value of 45 if there are no Level I exposed
individuals, but there is at least one exposed individual in one or
more regularly occupied structures subject to Level II concentrations.
     Assign a value of 20 if there is no Level I or Level II
exposed individual but there is at least one individual in a regularly
occupied structure within an area of subsurface contamination.
    Enter the value assigned in Table 5-11.
    <IP_ADDRESS>.2 Population. Evaluate population based on three factors:
Level I concentrations, Level II concentrations, and population within
an area of subsurface contamination. Determine which factors apply as
specified in section <IP_ADDRESS>.1, using the health-based benchmarks from
Table 5-19. Evaluate populations subject to Level I and Level II
concentrations as specified in section 2.5.

   Table 5-19--Health-Based Benchmarks for Hazardous Substances in the
                     Subsurface Intrusion Component
------------------------------------------------------------------------

------------------------------------------------------------------------
Screening concentration for cancer corresponding to that
 concentration that corresponds to the 10-\6\ individual cancer risk
 using the inhalation unit risk. For oral exposures use the oral
 cancer slope factor................................................
Screening concentration for noncancer toxicological responses
 corresponding to the reference dose (RfD) for oral exposure and the
 reference concentration (RfC) for inhalation exposures.............
------------------------------------------------------------------------

    Count only those persons meeting the criteria for population as
specified in section <IP_ADDRESS>. In estimating the number of individuals
in structures in an area of observed exposure or area of subsurface
contamination if the actual number of residents is not known, 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. Assign the population subject
to Level I concentrations as follows:
    1. Identify all exposed individuals regularly present in a
structure, or if the structure has subunits, identify those regularly
present in each subunit, located in an area of observed exposure
subject to Level I concentrations as described in sections 5.2.0 and
<IP_ADDRESS>.1. Identify only once per structure those exposed individuals
that are using more than one eligible subunit of the same structure
(e.g., using a common or shared area and other parts of the same
structure).
    2. For each structure or subunit count the number of individuals
residing in or

attending school or day care in the structure or subunit.
    3. Count the number of full-time and part-time workers in the
structure or subunit(s) subject to Level I concentrations. If
information is unavailable to classify a worker as full- or part-time,
evaluate that worker as being full-time. Divide the number of full-time
workers by 3 and the number of part-time workers by 6, and then sum
these products with the number of other individuals for each structure
or subunit.
    4. Sum this combined value for all structures, or subunits, within
areas of observed exposure and multiply this sum by 10.
    Assign the resulting product as the combined population factor
value subject to Level I concentrations for the site. Enter this value
in line 9a of Table 5-11.
    <IP_ADDRESS>.2.2 Level II concentrations. Assign the population subject
to Level II concentrations as follows:
    1. Identify all exposed individuals regularly present in an
eligible structure, or if the structure has subunits, identify those
regularly present in each subunit, located in an area of observed
exposure subject to Level II concentrations as described in sections
5.2.0 and <IP_ADDRESS>.1. Identify only once per structure those exposed
individuals that are using more than one eligible subunit of the same
structure (e.g., using a common or shared area and other parts of the
same structure).
    2. Do not include exposed individuals already counted under the
Level I concentrations factor.
    3. For each structure or subunit(s), count the number of
individuals residing in or attending school or day care in the
structure, or subunit, subject to Level II concentrations.
    4. Count the number of full-time and part-time workers in the
structure or subunit(s) subject to Level II concentrations. If
information is unavailable to classify a worker as full- or part-time,
evaluate that worker as being full-time. Divide the number of full-time
workers by 3 and the number of part-time workers by 6, and then sum
these products with the number of other individuals for each structure
or subunit.
    5. Sum the combined population value for all structures within the
areas of observed exposure for the site.
    Assign this sum as the combined population value subject to Level
II contamination for this factor. Enter this value in line 9b of Table
5-11.
    <IP_ADDRESS>.2.3 Population within area(s) of subsurface contamination.
Assign the population in area(s) of subsurface contamination factor
value as follows, unless available information indicates otherwise (see
sections 5.2.0 and <IP_ADDRESS>.1):
    1. Identify the regularly occupied structures with a structure
containment value greater than zero and the eligible population
associated with the structures or portions of structures in each area
of subsurface contamination:
     For each regularly occupied structure or portion of a
structure in an area of subsurface contamination, sum the number of all
individuals residing in or attending school or day care, in the
structure or portion of the structure in the area of subsurface
contamination.
     Count the number of full-time and part-time workers
regularly present in each structure or portion of a structure in an
area of subsurface contamination. If information is unavailable to
classify a worker as full- or part-time, evaluate that worker as being
full-time. Divide the number of full-time workers by 3 and the number
of part-time workers by 6. Sum these products with the number of
individuals residing in or attending school or day care in the
structure.
     Use this sum as the population for the structure.
    2. Estimate the depth or distance to contamination at each
regularly occupied structure within an area of subsurface contamination
based on available sampling data, and categorize each eligible
structure based on the depth or distance to contamination and sampling
media as presented in Table 5-20. Weight the population in each
structure using the appropriate weighting factors in Table 5-20. If
samples from multiple media are available, use the sample that results
in the highest weighting factor.
    3. Sum the weighted population in all structures within the area(s)
of subsurface contamination and assign this sum as the population
subject subsurface contamination factor value. Enter this value in line
9c of Table 5-11.

  Table 5-20--Weighting Factor Values for Populations Within an Area of
                        Subsurface Contamination
------------------------------------------------------------------------
                                                            Population
  Eligible populations \a\ in structures \b\ within an       weighting
            area of subsurface contamination                  factor
------------------------------------------------------------------------
Population in a structure with levels of contamination               0.9
 in a semi-enclosed or enclosed crawl space sample
 meeting observed release criteria
or......................................................
Population in a subunit of a multi-story structure
 within an area of subsurface contamination located
 directly above a level in an area of observed exposure
 or a gaseous indoor air sample meeting observed release
 criteria...............................................
Population in a structure where levels of contaminants               0.4
 meeting observed release criteria are found in any
 sampling media at or within five feet horizontally or
 vertically of the structure foundation.................
Population occupying a structure where levels of                     0.2
 contaminants meeting observed release criteria are
 found or inferred based on any underlying non-ground
 water subsurface sample at a depth less than or equal
 to 30 feet
or......................................................
Population in a structure within an area of subsurface
 contamination where levels of contaminants meeting
 observed release criteria are inferred based on semi-
 enclosed or enclosed crawl space samples in surrounding
 structures.............................................
Population in a structure where levels of contaminants               0.1
 meeting observed release criteria are found or inferred
 based on underlying ground water samples greater than
 five feet from the structure foundation
or......................................................
Population in a structure where levels of contaminants
 meeting observed release criteria are found or inferred
 based on any underlying sample at depths greater than
 30 feet................................................
------------------------------------------------------------------------
\a\ Eligible populations include residents (including individuals living
  in, or attending school or day care in the structure), and workers in
  regularly occupied structures (see HRS Section <IP_ADDRESS>).
\b\ Eligible structures may include single- or multi-tenant structures
  where eligible populations reside, attend school or day care, or work.
  These structures may also be mixed use structures.

    <IP_ADDRESS>.2.4 Calculation of population factor value. Sum the factor
values for Level I concentrations, Level II concentrations, and
population in the area(s) of subsurface contamination. Assign this sum
as the population factor value. Enter this value in line 9d of Table 5-
11.
    <IP_ADDRESS>.3 Resources. Evaluate the resources factor as follows:
     Assign a value of 5 if a resource structure (e.g.,
library, church, tribal facility) is present and regularly occupied
within either an area of observed exposure or area of subsurface
contamination.
     Assign a value of 0 if there is no resource structure
within an area of observed exposure or area of subsurface
contamination.
    Enter the value assigned in Table 5-11.
    <IP_ADDRESS>.4 Calculation of targets factor category value. Sum the
values for the exposed individual, population, and resources factors.
Do not round to the nearest integer. Assign this sum as the targets
factor category value for the subsurface intrusion component. Enter
this value in Table 5-11.
    5.2.2 Calculation of subsurface intrusion component score. Multiply
the factor category values for likelihood of exposure, waste
characteristics and targets and round the product to the nearest
integer. Divide the product by 82,500. Assign the resulting value,
subject to a maximum of 100, as the subsurface intrusion component
score and enter this score in Table 5-11.
    5.3 Calculation of the soil exposure and subsurface intrusion
pathway score: Sum the soil exposure component score and subsurface
intrusion component. Assign the resulting value, subject to a maximum
of 100, as the soil exposure and subsurface intrusion pathway score
(Ssessi). Enter this score in Table 5-11.

6.0 Air Migration Pathway

* * * * *

   Table 6-14--Health-Based Benchmarks for Hazardous Substances in Air
------------------------------------------------------------------------

-------------------------------------------------------------------------
 Concentration corresponding to National Ambient Air Quality
 Standard (NAAQS).
 Concentration corresponding to National Emission Standards for
 Hazardous Air Pollutants (NESHAPs).
 Screening concentration for cancer corresponding to that
 concentration that corresponds to the 10-6 individual cancer risk for
 inhalation exposures.
 Screening concentration for noncancer toxicological responses
 corresponding to the Reference Concentration (RfC) for inhalation
 exposures.
------------------------------------------------------------------------

* * * * *

7.0 Sites Containing Radioactive Substances

* * * * *

[GRAPHIC] [TIFF OMITTED] TP29FE16.040

[GRAPHIC] [TIFF OMITTED] TP29FE16.041

* * * * *
    * * * These differences apply largely to the soil exposure and
subsurface intrusion pathway and to sites containing mixed radioactive
and other hazardous substances. * * *
    7.1 Likelihood of release/likelihood of exposure. Evaluate
likelihood of release for the three migration pathways and likelihood
of exposure for the soil exposure and subsurface intrusion pathway as
specified in sections 2 through 6, except: Establish an observed
release, observed contamination, and/or observed exposure as specified
in section 7.1.1. When an observed release or exposure cannot be
established for a migration pathway or the subsurface intrusion
component of the soil exposure and subsurface intrusion pathway,
evaluate potential to release as specified in section 7.1.2. When
observed contamination cannot be established, do not evaluate the soil
exposure component of the soil exposure and subsurface intrusion
pathway.
    7.1.1 Observed release/observed contamination/observed exposure.
For radioactive substances, establish an observed release for each
migration pathway by demonstrating that the site has released a
radioactive substance to the pathway (or watershed or aquifer, as
appropriate); establish observed contamination or observed exposure for
the soil exposure and subsurface intrusion pathway as indicated below.
Base these demonstrations on one or more of the following, as
appropriate to the pathway being evaluated:
     Direct observation:

--For each migration pathway, a material that contains one or more
radionuclides has been seen entering the atmosphere, surface water, or
ground water, as appropriate, or is known to have entered ground water
or surface water through direct deposition, or
--For the surface water migration pathway, a source area containing
radioactive substances has been flooded at a time that radioactive
substances were present and one or more radioactive substances were in
contact with the flood waters.
--For the subsurface intrusion component of the soil exposure and
subsurface intrusion pathway, a material that contains one or more
radionuclides has been observed entering a regularly occupied structure
via the subsurface or is known to have entered a regularly occupied
structure via the subsurface. Also, when evidence supports the
inference of subsurface intrusion of a material that contains one or
more radionuclides by the site into a regularly occupied structure,
demonstrated adverse effects associated with that release may also be
used to establish observed exposure by direct observation.

     Analysis of radionuclide concentrations in samples
appropriate to the pathway (that is, ground water, soil, air, indoor
air, surface water, benthic, or sediment samples):

--For radionuclides that occur naturally and for radionuclides that are
ubiquitous in the environment:

    [ssquf] Measured concentration (in units of activity, for example,
pCi per kilogram [pCi/kg], pCi per liter [pCi/L], pCi per cubic meter
[pCi/m3]) of a given radionuclide in the sample are at a level that:
    [cir] Equals or exceeds a value 2 standard deviations above the
mean site-specific background concentration for that radionuclide in
that type of sample, or
    [cir] Exceeds the upper-limit value of the range of regional
background concentration values for that specific radionuclide in that
type of sample.
    [ssquf] Some portion of the increase must be attributable to the
site to establish the observed release (or observed contamination or
observed exposure), and
    [ssquf] For the soil exposure component of the soil exposure and
subsurface intrusion pathway only, the radionuclide must also be
present at the surface or covered by 2 feet or less of cover material
(for example, soil) to establish observed contamination.

--For man-made radionuclides without ubiquitous background
concentrations in the environment:

    [ssquf] Measured concentration (in units of activity) of a given
radionuclide in a sample equals or exceeds the sample quantitation
limit for that specific radionuclide in that type of media and is
attributable to the site.
    [ssquf] However, if the radionuclide concentration equals or
exceeds its sample quantitation limit, but its release can also be
attributed to one or more neighboring sites, then the measured
concentration of that radionuclide must also equal or exceed a value
either 2 standard deviations above the mean concentration of that
radionuclide contributed by those neighboring sites or 3 times its
background concentration, whichever is lower.
    [ssquf] If the sample quantitation limit cannot be established:
    [cir] If the sample analysis was performed under the EPA Contract
Laboratory Program, use the EPA contract-required quantitation limit
(CRQL) in place of the sample quantitation limit in establishing an
observed release (or observed contamination or observed exposure).
    [cir] If the sample analysis is not performed under the EPA
Contract Laboratory Program, use the detection limit in place of the
sample quantitation limit.

    [ssquf] For the soil exposure component of the soil exposure and
subsurface intrusion pathway only, the radionuclide must also be
present at the surface or covered by 2 feet or less of cover material
(for example, soil) to establish observed contamination.
     Gamma radiation measurements (applies only to observed
contamination or observed exposure in the soil exposure and subsurface
intrusion pathway):

--The gamma radiation exposure rate, as measured in microroentgens per
hour ([mu]R/hr) using a survey instrument held 1 meter above the ground
surface or floor or walls of a structure (or 1 meter away from an
aboveground source for the soil exposure component), equals or exceeds
2 times the site-specific background gamma radiation exposure rate.
--Some portion of the increase must be attributable to the site to
establish observed contamination. The gamma-emitting radionuclides do
not have to be within 2 feet of the surface of the source.

    For the three migration pathways and for the subsurface intrusion
component of the soil exposure and subsurface intrusion pathway, if an
observed release or observed exposure can be established for the
pathway (or threat, aquifer, or watershed, as appropriate), assign the
pathway (or threat, aquifer, or watershed) an observed release or
observed exposure factor value of 550 and proceed to section 7.2. If an
observed release or observed exposure cannot be established, assign an
observed release or observed exposure factor value of 0 and proceed to
section 7.1.2.
    For the soil exposure component of the soil exposure and subsurface
intrusion pathway, if observed contamination can be established, assign
the likelihood of exposure factor for resident population a value of
550 if there is an area of observed contamination in one or more
locations listed in section 5.1.1; evaluate the likelihood of exposure
factor for nearby population as specified in section <IP_ADDRESS>; and
proceed to section 7.2. If observed contamination cannot be
established, do not evaluate the soil exposure component of the soil
exposure and subsurface intrusion pathway.
    At sites containing mixed radioactive and other hazardous
substances, evaluate observed release (or observed contamination or
observed exposure) separately for radionuclides as described in this
section and for other hazardous substances as described in sections 2
through 6.
    For the three migration pathways and the subsurface intrusion
component of the soil exposure and subsurface intrusion pathway, if an
observed release or observed exposure can be established based on
either radionuclides or other hazardous substances, or both, assign the
pathway (or threat, aquifer, or watershed) an observed release or
observed exposure factor value of 550 and proceed to section 7.2. If an
observed release or observed exposure cannot be established based on
either radionuclides or other hazardous substances, assign an observed
release or observed exposure factor value of 0 and proceed to section
7.1.2.
    For the soil exposure component of the soil exposure and subsurface
intrusion pathway, if observed contamination can be established based
on either radionuclides or other hazardous substances, or both, assign
the likelihood of exposure factor for resident population a value of
550 if there is an area of observed contamination in one or more
locations listed in section 5.1.1; evaluate the likelihood of exposure
factor for nearby population as specified in section <IP_ADDRESS>; and
proceed to section 7.2. If observed contamination cannot be established
based on either radionuclides or other hazardous substances, do not
evaluate the soil exposure component of the soil exposure and
subsurface intrusion pathway.
    7.1.2 Potential to release/potential for exposure. For the three
migration pathways and the subsurface intrusion component of the soil
exposure and subsurface intrusion pathway, evaluate potential to
release or potential for exposure for sites containing radionuclides in
the same manner as specified for sites containing other hazardous
substances. Base the evaluation on the physical and chemical properties
of the radionuclides, not on their level of radioactivity. For the
subsurface intrusion component of the soil exposure and subsurface
intrusion pathway, if the potential for exposure is based on the
presence of gamma emitting radioactive substances, assign a potential
for exposure factor value of 500 only if the contamination is found
within 2 feet beneath a regularly occupied structure, otherwise assign
a potential for exposure factor value of 0.
    For sites containing mixed radioactive and other hazardous
substances, evaluate potential to release or potential for exposure
considering radionuclides and other hazardous substances together.
Evaluate potential to release for each migration pathway and the
potential for exposure for the subsurface intrusion component of the
soil exposure and subsurface intrusion pathway as specified in sections
3 through 6, as appropriate.
* * * * *
    7.2.3  Persistence/Degradation. In determining the surface water
persistence factor for radionuclides, evaluate the surface water
persistence this factor based solely on half-life; do not include
sorption to sediments in the evaluation as is done for nonradioactive
hazardous substances. Assign a persistence factor value from Table 4-10
(section <IP_ADDRESS>.1.2) to each radionuclide based on half-life (t
1/2) calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.042

Where:

r = Radioactive half-life.
v = Volatilization half-life.

    If the volatilization half-life cannot be estimated for a
radionuclide from available data, delete it from the equation. Select
the portion of Table 4-10 to use in assigning the persistence factor
value as specified in section <IP_ADDRESS>.1.2.
    At sites containing mixed radioactive and other hazardous
substances, evaluate the persistence factor separately for each
radionuclide and for each nonradioactive hazardous substance, even if
the available data indicate that they are combined chemically. Assign a
persistence factor value to each radionuclide as specified in this
section and to each nonradioactive hazardous substance as specified in
section <IP_ADDRESS>.1.2. When combined chemically, assign a single
persistence factor value based on the higher of the two values assigned
(individually) to the radioactive and nonradioactive components.
    In determining the subsurface intrusion degradation factor for
radionuclides, when evaluating this factor based solely on half-life.
Assign a degradation factor value from section <IP_ADDRESS>.1.2 to each
radionuclide based on half-life (t1/2) calculated as
follows:
[GRAPHIC] [TIFF OMITTED] TP29FE16.043

Where:

r = Radioactive half-life.

    At sites containing mixed radioactive and other hazardous
substances,

evaluate the persistence or degradation factor separately for each
radionuclide and for each nonradioactive hazardous substance, even if
the available data indicate that they are combined chemically. Assign a
persistence or degradation factor value to each radionuclide as
specified in this section and to each nonradioactive hazardous
substance as specified in sections <IP_ADDRESS>.1.2 and <IP_ADDRESS>.1.2. When
combined chemically, assign a single persistence or degradation factor
value based on the higher of the two values assigned (individually) to
the radioactive and nonradioactive components.
    7.2.4 Selection of substance potentially posing greatest hazard.
For the subsurface intrusion component of the soil exposure and
subsurface intrusion pathway and each migration pathway (or threat,
aquifer, or watershed, as appropriate), select the radioactive
substance or nonradioactive hazardous substance that potentially poses
the greatest hazard based on its toxicity factor value, combined with
the applicable mobility, persistence, degradation and/or
bioaccumulation (or ecosystem bioaccumulation) potential factor values.
Combine these factor values as specified in sections 2 through 6. For
the soil exposure component of the soil exposure and subsurface
intrusion pathway, base the selection on the toxicity factor alone (see
sections 2 and 5).
* * * * *
    <IP_ADDRESS> Source hazardous waste quantity for radionuclides For each
migration pathway, assign a source hazardous waste quantity value to
each source having a containment factor value greater than 0 for the
pathway being evaluated. 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, assign a source hazardous waste quantity value to each
regularly occupied structure located within areas of observed exposure
or areas of subsurface contamination. Allocate hazardous substances and
hazardous wastestreams to specific sources (or areas of observed
contamination, area of observed exposure or area of subsurface
contamination) as specified in sections 2.4.2 and 5.2.0.
    <IP_ADDRESS>.1 Radionuclide constituent quantity (Tier A). Evaluate
radionuclide constituent quantity for each source (or area of observed
contamination or area of observed exposure) based on the activity
content of the radionuclides allocated to the source (or area of
observed contamination or area of observed exposure) as follows:

 Estimate the net activity content (in curies) for the source
(or area of observed contamination or area of observed exposure) based
on:

    --Manifests, or
    --Either of the following equations, as applicable:
    [GRAPHIC] [TIFF OMITTED] TP29FE16.044

Where:

N = Estimated net activity content (in curies) for the source (or
area of observed contamination or area of observed exposure).
V = Total volume of material (in cubic yards) in a source (or area
of observed contamination or area of observed exposure) containing
radionuclides.
ACi = Activity concentration above the respective
background concentration (in pCi/g) for each radionuclide i
allocated to the source (or area of observed contamination or area
of observed exposure).
n = Number of radionuclides allocated to the source (or area of
observed contamination or area of observed exposure) above the
respective background concentrations.

    or,
    [GRAPHIC] [TIFF OMITTED] TP29FE16.045

Where:

N = Estimated net activity content (in curies) for the source (or
area of observed contamination or area of observed exposure).
V = Total volume of material (in gallons) in a source (or area of
observed contamination or area of observed exposure) containing
radionuclides.
ACi = Activity concentration above the respective
background concentration (in pCi/1) for each radionuclide i
allocated to the source (or area of observed contamination or area
of observed exposure).
n = Number of radionuclides allocated to the source (or area of
observed contamination or area of observed exposure) above the
respective background concentrations.

     Estimate volume for the source (or volume for the area of
observed contamination or area of observed exposure) based on records
or measurements.
     For the soil exposure component, in estimating the volume
for areas of observed contamination, do not include more than the first
2 feet of depth, except: For those types of areas of observed
contamination listed in Tier C of Table 5-2 (section <IP_ADDRESS>.2),
include the entire depth, not just that within 2 feet of the surface.
     For the subsurface intrusion component, in estimating the
volume for areas of observed exposure, only use the volume of air in
the regularly occupied structures where observed exposure has been
documented.
     Convert from curies of radionuclides to equivalent pounds
of nonradioactive hazardous substances by multiplying the activity
estimate for the source (or area of observed contamination or area of
observed exposure) by 1,000.
     Assign this resulting product as the radionuclide
constituent quantity value for the source (or area of observed
contamination or area of observed exposure).
    If the radionuclide constituent quantity for the source (or area of
observed contamination or area of observed exposure) is adequately
determined (that is, the total activity of all radionuclides 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 radionuclide
wastestream quantity measure in section <IP_ADDRESS>.2. Instead, assign
radionuclide wastestream quantity a value of 0 and proceed to section
<IP_ADDRESS>.3. If the radionuclide constituent quantity is not adequately
determined, assign the source (or area of observed contamination or
area of observed exposure) a value for radionuclide constituent
quantity based on the available data and proceed to section <IP_ADDRESS>.2.
    <IP_ADDRESS>.2 Radionuclide wastestream quantity (Tier B). Evaluate
radionuclide wastestream quantity for the source (or area of observed
contamination, area of observed exposure, or area of subsurface
contamination) based on the activity content of radionuclide
wastestreams allocated to the source (or area of observed
contamination, area of observed exposure, or area of subsurface
contamination) as follows:
     Estimate the total volume (in cubic yards or in gallons)
of wastestreams containing radionuclides allocated to the source (or
area of observed contamination, area of observed exposure, or area of
subsurface contamination).
     Divide the volume in cubic yards by 0.55 (or the volume in
gallons by 110) to convert to the activity content expressed in terms
of equivalent pounds of nonradioactive hazardous substances.

     Assign the resulting value as the radionuclide wastestream
quantity value for the source (or area of observed contamination, area
of observed exposure, or area of subsurface contamination).
     For the subsurface intrusion component of the soil
exposure and subsurface intrusion pathway, estimate the total
wastestream volume for all regularly occupied structures located within
areas of observed exposure with observed or inferred intrusion and
within areas of subsurface contamination. Calculate the volume of each
regularly occupied structure based on actual data. If unknown, use a
ceiling height of 8 feet.
    <IP_ADDRESS>.3 Calculation of source hazardous waste quantity value for
radionuclides. Select the higher of the values assigned to the source
(or area of observed contamination, area of observed exposure, and/or
area of subsurface contamination) for radionuclide constituent quantity
and radionuclide wastestream quantity. Assign this value as the source
hazardous waste quantity value for the source (or area of observed
contamination, area of observed exposure, or area of subsurface
contamination). Do not round to the nearest integer.
    <IP_ADDRESS> Calculation of hazardous waste quantity factor value for
radionuclides. Sum the source hazardous waste quantity values assigned
to all sources (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 this pathway from
Table 2-6 (section <IP_ADDRESS>).
    For a migration pathway, if the radionuclide 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 radionuclide 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 7.3), 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 radionuclide 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 radionuclide 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 radionuclide 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 radionuclide constituent quantity is not adequately determined for
one or more areas of observed exposure, assign either the value from
Table 2-6 or a value of 10, whichever is greater, as the hazardous
waste quantity factor value.
    <IP_ADDRESS> Calculation of hazardous waste quantity factor value for
sites containing mixed radioactive and other hazardous substances. For
each source (or area of observed contamination, area of observed
exposure, or area of subsurface contamination) containing mixed
radioactive and other hazardous substances, calculate two source
hazardous waste quantity values--one based on radionuclides as
specified in sections <IP_ADDRESS> through <IP_ADDRESS>.3 and the other based on
the nonradioactive hazardous substances as specified in sections
<IP_ADDRESS> through <IP_ADDRESS>.5, and sections <IP_ADDRESS>.2, <IP_ADDRESS>.2 and
<IP_ADDRESS>.2 (that is, determine each value as if the other type of
substance was not present). Sum the two values to determine a combined
source hazardous waste quantity value for the source (or area of
observed contamination, area of observed exposure, or area of
subsurface contamination). Do not round this value to the nearest
integer.
    Use this combined source hazardous waste quantity value to
calculate the hazardous waste quantity factor value for the pathway as
specified in section <IP_ADDRESS>, except: If either the hazardous
constituent quantity or the radionuclide constituent quantity, or both,
are not adequately determined for one or more sources (or one or more
portions of sources or releases remaining after a removal action) or
for one or more areas of observed contamination, areas of observed
exposure, or areas of subsurface contamination, as applicable, assign
the value from Table 2-6 or the default value applicable for the
pathway, whichever is greater, as the hazardous waste quantity factor
value for the pathway.
    7.3 Targets. For radioactive substances, evaluate the targets
factor category as specified in section 2.5 and sections 3 through 6,
except: Establish Level I and Level II concentrations at sampling
locations as specified in sections 7.3.1 and 7.3.2 and establish
weighting factors for populations associated with an area of subsurface
contamination in the subsurface intrusion component of the soil
exposure and subsurface intrusion pathway as specified in section
7.3.3.
    For all pathways (components and threats), use the same target
distance limits for sites containing radioactive substances as is
specified in sections 3 through 6 for sites containing nonradioactive
hazardous substances. At sites containing mixed radioactive and other
hazardous substances, include all sources (or areas of observed
contamination, areas of observed exposure, or areas of subsurface
contamination) at the site in identifying the applicable targets for
the pathway.
    7.3.1 Level of contamination at a sampling location. Determine
whether Level I or Level II concentrations apply at a sampling location
(and thus to the associated targets) as follows:

     Select the benchmarks from section 7.3.2 applicable to the
pathway (or component or threat) being evaluated.
     Compare the concentrations of radionuclides in the sample
(or comparable samples) to their benchmark concentrations for the
pathway (or component or threat) as specified in section 7.3.2. Treat
comparable samples as specified in section 2.5.1.
     Determine which level applies based on this comparison.
     If none of the radionuclides eligible to be evaluated for
the sampling location have an applicable benchmark, assign Level II to
the actual contamination at that sampling location for the pathway (or
component or threat).
     In making the comparison, consider only those samples, and
only those radionuclides 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 for the human food chain threat of the
surface water pathway as specified in sections <IP_ADDRESS> and <IP_ADDRESS>.
    7.3.2  Comparison to benchmarks. Use the following media specific
benchmarks (expressed in activity units, for example, pCi/l for water,
pCi/kg for soil and for aquatic human food chain organisms, and pCi/m3
for air) for making the comparisons for the indicated pathway (or
threat):
     Maximum Contaminant Levels (MCLs)--ground water migration
pathway and drinking water threat in surface water migration pathway.
     Uranium Mill Tailings Radiation Control Act (UMTRCA)
standards--soil exposure component of the soil exposure and subsurface
intrusion pathway only.
     Screening concentration for cancer corresponding to that
concentration that corresponds to the 10-\6\ individual
cancer risk for inhalation exposures (air migration pathway and
subsurface intrusion component of the soil exposure and subsurface
intrusion pathway) or for oral exposures (ground water migration
pathway; drinking water or human food chain threats in surface water
migration pathway; and soil exposure and subsurface intrusion pathway).

--For the soil exposure and subsurface intrusion pathway, include two
screening concentrations for cancer--one for ingestion of surface
materials and one for external radiation exposures from gamma-emitting
radionuclides in surface materials.

    Select the benchmark(s) applicable to the pathway (component or
threat) being evaluated. Compare the concentration of each radionuclide
from the sampling location to its benchmark concentration(s) for that
pathway (component or threat). Use only those samples and only those
radionuclides 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 radionuclide from any sample equals or
exceeds its benchmark concentration, consider the sampling location to
be subject to Level I concentrations for that pathway (component or
threat). If more than one benchmark applies to the radionuclide, assign
Level I if the radionuclide concentration equals or exceeds the lowest
applicable benchmark concentration. In addition, for the soil exposure
and subsurface intrusion pathway, assign Level I concentrations at the
sampling location if measured gamma radiation exposure rates equal or
exceed 2 times the background level (see section 7.1.1).
    If no radionuclide individually equals or exceeds its benchmark
concentration, but more than one radionuclide either meets the criteria
for an observed release (or observed contamination or observed
exposure) for the sample or is eligible to be evaluated for a tissue
sample (see sections <IP_ADDRESS> and <IP_ADDRESS>), calculate a value for index
I for these radionuclides as specified in section 2.5.2. If I equals or
exceeds 1, assign Level I to the sampling location. If I is less than
1, assign Level II.
    At sites containing mixed radioactive and other hazardous
substances, establish the level of contamination for each sampling
location considering radioactive substances and nonradioactive
hazardous substances separately. Compare the concentration of each
radionuclide and each nonradioactive hazardous substance from the
sampling location to its respective benchmark concentration(s). Use
only those samples and only those 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 one or more applicable
radionuclides or other hazardous substances from any sample equals or
exceeds its benchmark concentration, consider the sampling location to
be subject to Level I concentrations. If more than one benchmark
applies to a radionuclide or other hazardous substance, assign Level I
if the concentration of the radionuclide or other hazardous substance
equals or exceeds its lowest applicable benchmark concentration.
    If no radionuclide or other hazardous substance individually exceed
a benchmark concentration, but more than one radionuclide or other
hazardous substance either meets the criteria for an observed release
(or observed contamination or observed exposure) for the sample or is
eligible to be evaluated for a tissue sample, calculate an index I for
both types of substances as specified in section 2.5.2. Sum the index I
values for the two types of substances. If the value, individually or
combined, equals or exceeds 1, assign Level I to the sample location.
If it is less than 1, calculate an index J for the nonradioactive
hazardous substances as specified in section 2.5.2. If J equals or
exceeds 1, assign Level I to the sampling location. If J is less than
1, assign Level II.
    7.3.3 Weighting of targets within an area of subsurface
contamination. For the subsurface intrusion component of the soil
exposure and subsurface intrusion pathway, assign a weighting factor as
specified in section <IP_ADDRESS>.2.3 except when an area of subsurface
contamination is bound by gamma radiation exposure rates meeting
observed release criteria with a depth to contamination of 2 feet or
less. For those populations residing, working, or attending school or
day care in a structure, assign a weighting factor of 0.9.

[FR Doc. 2016-02749 Filed 2-26-16; 8:45 am]
 BILLING CODE 6560-50-P