greater than 6 feet above
                             ground surface (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 value 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, as well as manmade preferential pathways
such as utility conduits or drainage systems).
    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.
     If the depth to contamination is greater than 10 feet,
do not consider layers or portions of layers within the first 10
feet of the depth to contamination (as assigned in section
<IP_ADDRESS>.2.2).
     If, for the interval between the lowest point of a
regularly occupied structure and the highest point of hazardous
substances in the subsurface, 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 interval identified above. Consider only layers at least
1 foot thick.--Assign a value for individual layers from Table 5-14
using the hydraulic conductivity of the layer, if available. If the
hydraulic conductivity is not available, assign a value based on the
type of material in the selected layer.
--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
                                          Hydraulic          porosity/
         Type of material             conductivity (cm/    permeability
                                            sec)               value
------------------------------------------------------------------------
Gravel; clean sand; highly          Greater than or                    1
 permeable fractured igneous and     equal to 1 x 10-\3\.
 metamorphic rocks; permeable
 basalt; karst limestones and
 dolomites.
Sand; sandy clays; sandy loams;     Less than 1 x 10-\3\               2
 loamy sands; sandy 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;  Less than 1 x 10-\5\               3
 silty clays; 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         Less than 1 x 10-\7\               4
 (compact unfractured till);
 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 value 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                                                Assigned
(atm-m\3\/mol)                                                     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, or if a NAPL is present in the subsurface
below an area of observed exposure or area of subsurface
contamination at a depth less than or equal to 30 feet, assign that
substance a degradation factor value of 1.
     For all other situations, assign a degradation factor
value using Table 5-18. Assign the depth to contamination as
directed in section <IP_ADDRESS>.2.2, except if evidence indicates that
biologically active soil is not present throughout the depth beneath
any regularly occupied structure. In this situation, subtract any
thickness of non-biologically active soil from the estimated depth
to contamination.

                                   Table 5-18--Degradation Factor Value Table
----------------------------------------------------------------------------------------------------------------
                                                                                Half-life
                                                        --------------------------------------------------------
           Depth to contamination (feet) \a\                                   >30 days and
                                                             >100 Days          <=100 days         <=30 days
----------------------------------------------------------------------------------------------------------------
<10....................................................                  1                  1                  1
10 to <=30.............................................                  1                  1                0.1
>30....................................................                  1                0.5                0.1
----------------------------------------------------------------------------------------------------------------
\a\ When determining the depth to contamination do not include layers of non-biologically-active soil, nor
  subsurface intervals with channelized flow (e.g., karst, lava tubes, open fractures, and manmade preferential
  pathways as directed in section <IP_ADDRESS>.2.2).

Calculate the half-life for each hazardous substance that meets
subsurface intrusion observed release criteria as follows:
    The half-life of a substance in the subsurface is defined for
HRS purposes as the time required to reduce the initial
concentration of the substance 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] TR09JA17.072

Where:

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

    If either 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, assign a value of 1.
    <IP_ADDRESS>.1.3 Calculation of toxicity/degradation factor value.
Assign each substance a toxicity/degradation 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 or subunits with a non-zero
structure containment value. Also include all regularly occupied
structures or subunits that have had mitigation systems installed as
part of a removal or other temporary response action. If sufficient
structure-specific concentration data is available and state of the
science shows there is no unacceptable risk of exposure to
populations in a regularly occupied structure or subunit in an area
of subsurface contamination, that structure or subunit is not
included in the hazardous waste quantity evaluation. In estimating
the hazardous waste quantity, use Tables 2-5 and 5-19 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 5-19. 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:
    [ssquf] Calculate the volume of each regularly occupied
structure based on actual data. If unknown, use a ceiling height of
8 feet.
    [ssquf] 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.
    [ssquf] 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.

     For Tier D, area, if volume is unknown, use the area
divisor listed in Tier D of Table 5-19 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) or subunit based on actual footprint area data.
    [ssquf] 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).
    [ssquf] For multi-subunit structures, when calculating Tier D,
calculate area 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 area of all
regularly occupied subunit spaces below the floor with an observed
exposure and one story above, unless evidence indicates otherwise.
    [ssquf] For multi-subunit structures within an area of
subsurface contamination and no observed or inferred exposure,
consider only the area of the regularly occupied subunit spaces on
the lowest story, unless available information indicates otherwise.

          Table 5-19--Hazardous Waste Quantity Evaluation Equations for Subsurface Intrusion Component
----------------------------------------------------------------------------------------------------------------
                                                                                Equation for assigning
           Tier                        Measure                       Units                     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, and if an area of
subsurface contamination exists, assign a factor value as follows:

--Determine the values from Table 2-6 with and without consideration
of the removal action.
--If the value that would be assigned from Table 2-6 without
consideration of the removal action would be 100 or greater, assign
either the value from Table 2-6 with consideration of the removal
action or a value of 100, whichever is greater, as the hazardous
waste quantity factor value for the component.
--If the value that would be assigned from Table 2-6 without
consideration of the removal action would be less than 100, assign a
value of 10 as the hazardous waste quantity factor value for the
component.

     Otherwise, if none of the targets for the subsurface
intrusion component is subject to Level I or Level II concentrations
and there has not been a removal action, assign a value from Table
2-6 or a value of 10, whichever is greater.
    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 with structure containment factors greater than 0.
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 formerly occupied structure 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 or temporary response action has occurred
that has not completely mitigated the release, count the initial
targets as if the removal or temporary response action has not
permanently interrupted target exposure from subsurface intrusion.
Evaluate those targets based on conditions at the time of removal of
temporary response action.

    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. If sufficient structure-specific concentration data
is available and state of the science shows there is no unacceptable
risk of exposure to targets in the lowest level, those targets are
not included in the evaluation.
     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. (The weighting of these targets is specified in
Section <IP_ADDRESS>.2.) If sufficient structure-specific concentration
data is available and state of the science shows there is no
unacceptable risk of exposure to targets in the level above where
the observed exposure has been documented, those targets are not
included in the evaluation.
    <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 5-20 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.

--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 5-20. Evaluate populations
subject to Level I and Level II concentrations as specified in
section 2.5.

   Table 5-20--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 an
eligible structure with a structure containment value greater than
zero, 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 with a structure containment value greater than
zero, 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 factor value subject
to Level II concentrations for this site. 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. If sufficient structure-
specific concentration data is available and state of the science
shows there is no unacceptable risk of exposure to populations in a
regularly occupied structure in an area of subsurface contamination,
those populations are not included in the evaluation. (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 sample media as presented in Table 5-21. Weight the population
in each structure using the appropriate weighting factors in Table
5-21. 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 within an area of subsurface contamination factor value.
Enter this value in line 9c of Table 5-11.

  Table 5-21--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
------------------------------------------------------------------------
            Samples From Within Structures or in Crawl Spaces
------------------------------------------------------------------------
1. Population in a structure with levels of                          0.9
 contamination 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 or
Population within a structure where a mitigation system
 has been installed as part of a removal or other
 temporary response action.
2. Population in a structure where levels of                         0.8
 contaminants meeting observed release criteria are
 inferred based on semi-enclosed or enclosed crawl space
 samples in surrounding structures, and a NAPL is
 present in those samples...............................
3. Population in a structure where levels of                         0.4
 contaminants meeting observed release criteria are
 inferred based on semi-enclosed or enclosed crawl space
 samples in surrounding structures, but no NAPL is
 present................................................
------------------------------------------------------------------------
 Subsurface Samples From Less Than or Equal to 5 Feet From a Foundation
------------------------------------------------------------------------
4. Population in a structure where levels of                         0.8
 contaminants meeting observed release criteria are
 found or inferred based on any sampling media at or
 within five feet horizontally or vertically of the
 structure foundation, and a NAPL is present within that
 depth..................................................
5. Population in a structure where levels of                         0.4
 contaminants meeting observed release criteria are
 found or inferred based on any sampling media at or
 within five feet horizontally or vertically of the
 structure foundation, but no NAPL is present within
 that depth.............................................
------------------------------------------------------------------------
Subsurface Samples From Greater Than 5 Feet But Less Than or Equal to 30
                               Feet Depth
------------------------------------------------------------------------
6. Population in a structure where levels of                         0.4
 contaminants meeting observed release criteria are
 found or inferred based on any underlying non-ground
 water subsurface sample at a depth greater than 5 feet
 but less than or equal to 30 feet from a structure
 foundation and a NAPL is present within that depth.....
7. Population in 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 greater than 5 feet
 but less than or equal to 30 feet, but no NAPL is
 present within that depth..............................
8. Population in a structure where levels of                         0.2
 contaminants meeting observed release criteria are
 found or inferred based on underlying ground water
 samples greater than 5 feet from the structure
 foundation but less than or equal to 30 feet, and a
 NAPL is present in those samples.......................
9. Population in a structure where levels of                         0.1
 contaminants meeting observed release criteria are
 found or inferred based on underlying ground water
 samples greater than 5 feet from the structure
 foundation but less than or equal to 30 feet, but no
 NAPL is present in those samples.......................
------------------------------------------------------------------------
           Subsurface Samples From Greater Than 30 Feet Depth
------------------------------------------------------------------------
10. Population in a structure where levels of                        0.1
 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 within 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 score. 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

* * * * *

                                                                 Table 7-1--HRS Factors Evaluated Differently for Radionuclides
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Subsurface
                                                    Surface water                       Soil exposure                         intrusion
     Ground water pathway          Status \a\          pathway         Status \a\       component of       Status \a\       component of       Status \a\        Air pathway       Status \a\
                                                                                SESSI pathway                       SESSI pathway
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Likelihood of Release.........                    Likelihood of                       Likelihood of                       Likelihood of                       Likelihood of
                                                   Release.                            Exposure.                           Exposure.                           Release.
Observed Release..............  Yes.............  Observed Release  Yes.............  Observed          Yes.............  Observed          Yes.............  Observed Release  Yes.
                                                                                Contamination.                      Exposure.
Potential to Release..........  No..............  Potential to      No..............  Attractiveness/   No..............  Potential for     Yes.............  Gas Potential to  No.
                                                   Release.                            Accessibility                       Exposure.                           Release.
                                                                                to Nearby
                                                                                Residents.
Containment...................  No..............  Overland Flow     No..............  Area of           No..............  Structure         No..............  Gas Containment.  No.
                                                   Containment.                        Contamination.                      Containment.
Net Precipitation.............  No..............  Runoff..........  No..............  Area of Observed  No..............  Depth to          Yes.............  Gas Source Type.  No.
                                                                                Exposure.                           Contamination.
Depth to Aquifer..............  No..............  Distance to       No..............  Area of           No..............  Vertical          No..............  Gas Migration     No.
                                                   Surface water.                      Subsurface                          migration.                          Potential.
                                                                                Contamination.
Travel Time...................  No..............  Flood Frequency.  No..............                                      Vapor Migration   No..............  Particulate       No.
                                                                                Potential.                          Potential to
                                                                                Release.
                                                  Flood             No..............                                                                          Particulate       No.
                                                   Containment.                                                                                Containment.
                                                                                Particulate       No.
                                                                                Source Type.
                                                                                Particulate       No.
                                                                                Migration
                                                                                Potential.
Waste Characteristics.........                    Waste                               Waste                               Waste                               Waste
                                                   Characteristics.                    Characteristics.                    Characteristics.                    Characteristics.
Toxicity......................  Yes.............  Toxicity/         Yes/Yes.........  Toxicity........  Yes.............  Toxicity/         Yes/Yes.........  Toxicity........  Yes.
                                                   Ecotoxicity.                                                            Degradation.
Mobility......................  No..............  Persistence/....  Yes/No..........  Hazardous Waste   Yes.............  Hazardous Waste   Yes.............  Mobility........  No.
                                                  Mobility........                     Quantity.                           Quantity.
Hazardous Waste Quantity......  Yes.............  Bioaccumu-lation  No..............                                                                          Hazardous Waste   Yes.
                                                   Potential.                                                                                Quantity.
                                                  Hazardous Waste   Yes.............
                                                   Quantity.
Targets.......................                    Targets.........                    Targets.........                    Targets.........                    Targets.........
Nearest Well..................  Yes.\b\.........  Nearest Intake..  Yes.\b\.........  Resident          Yes.\b\.........  Exposed.........  Yes.\b\.........  Nearest           Yes.\b\
                                                                                Individual.                        Individual......                     Individual.

Population....................  Yes.\b\.........  Drinking Water    Yes.\b\.........  Resident          Yes.\b\.........  Population......  Yes.\b\.........  Population......  Yes.\b\
                                                   Population.                         Population.
Resources.....................  No..............  Resources.......  No..............  Workers.........  No..............  Resources.......  No..............  Resources.......  No
Wellhead Protection Area......  No..............  Sensitive         Yes.\b\.........  Resources.......  No..............                                      Sensitive         No
                                                   Environments.                                                                                Environments.
                                                  Human Food Chain  Yes.\b\.........  Terrestrial       No..............
                                                   Individual.                         Sensitive
                                                                                Environments.
                                                  Human Food Chain  Yes.\b\.........  Nearby            No..............
                                                   Population.                         Individual.
                                                                                Population        No..............
                                                                                Within 1 Mile.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Factors evaluated differently are denoted by ``yes''; factors not evaluated differently are denoted by ``no''.
\b\ Difference is in the determination of Level I and Level II concentrations.

* * * * *
    * * * 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, soil gas, 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 or observed exposure. 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 component, threat, aquifer, or
watershed, as appropriate), assign the pathway (or component,
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 component, 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.
* * * * *
    7.2.1 Human Toxicity. For radioactive substances, evaluate the
human toxicity factor as specified below, not as specified in
section <IP_ADDRESS>.
    Assign human toxicity factor values to those radionuclides
available to the pathway based on quantitative dose-response
parameters for cancer risks as follows:
     Evaluate radionuclides only on the basis of
carcinogenicity and assign all radionuclides to weight-of-evidence
category A, or weight-of-evidence category ``Carcinogenic to
Humans''.
     Assign a human toxicity factor value from Table 7-2 to
each radionuclide based on its slope factor (also referred to as a
cancer potency factor).

--For each radionuclide, use the higher of the slope factors for
inhalation and ingestion to assign the factor value.
--If only one slope factor is available for the radionuclide use it
to assign the toxicity factor value.
--If no slope factor is available for the radionuclide, assign that
radionuclide a toxicity factor value of 0 and use other
radionuclides for which a slope factor is available to evaluate the
pathway.

     If all radionuclides available to a particular pathway
are assigned a human toxicity factor value of 0 (that is, no slope
factor is available for all the radionuclides), use a default human
toxicity factor value of 1,000 as the human toxicity factor value
for all radionuclides available to the pathway.
    At sites containing mixed radioactive and other hazardous
substances, evaluate the toxicity factor separately for the
radioactive and other hazardous substances and assign each a
separate toxicity factor value. This applies regardless of whether
the radioactive and other hazardous substances are physically
separated, combined chemically, or simply mixed together. Assign
toxicity factor values to the radionuclides as specified above and
to the other hazardous substances as specified in section <IP_ADDRESS>.
    At sites containing mixed radioactive and other hazardous
substances, if all radionuclides available to a particular pathway
are assigned a human toxicity factor value of 0, use a default human
toxicity factor value of 1,000 for all those radionuclides even if
nonradioactive hazardous substances available to the pathway are
assigned human toxicity factor values greater than 0. Similarly, if
all nonradioactive hazardous substances available to the pathway are
assigned a human toxicity factor value of 0, use a default human
toxicity factor value of 100 for all these nonradioactive hazardous
substances even if radionuclides available to the pathway are
assigned human toxicity factor values greater than 0.
* * * * *
    7.2.3 Persistence/Degradation. In determining the surface water
persistence factor for radionuclides, evaluate 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] TR09JA17.073

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] TR09JA17.074

Where:

r=Radioactive half-life.

    If no radioactive half-life information is available for a
radionuclide and the substance is not already assigned a value of 1,
unless information indicates otherwise, assign a value of 1.
    At sites containing mixed radioactive and other hazardous
substances, evaluate the 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 degradation factor value to each radionuclide as specified
in this section and to each nonradioactive hazardous substance as
specified in section <IP_ADDRESS>.1.2. If no radioactive half-life
information is available for a radionuclide and the substance is not
already assigned a value of 1, unless information indicates
otherwise, assign a value of 1. Similarly, if no half-life
information is available for a nonradioactive substance, and the
substance is not already assigned a value of 1, unless information
indicates otherwise, assign a value of 1. 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, areas of observed
exposure or areas 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] TR09JA17.075

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] TR09JA17.076

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 of the soil exposure and
subsurface intrusion pathway, 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 of the soil exposure and
subsurface intrusion pathway, 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 that have a
containment value >0 and that are 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 or areas
of observed exposure, 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 component of 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 a structure in an
area of subsurface contamination is delineated or inferred to be
delineated 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 delineated or inferred to be delineated by gamma
radiation exposure rates meeting observed release criteria with a
depth to contamination of 2 feet or less, assign a weighting factor
of 0.9.

[FR Doc. 2016-30640 Filed 1-6-17; 8:45 am]
 BILLING CODE 6560-50-P