randomly assigned values are based on distributions that vary by
category (e.g., ground water and surface water TOC distributions or
compliance forecast distributions that vary by system size category).
    Once model PWSs are created and assigned baseline and compliance
characteristics, SafeWater MCBC estimates the quantified costs and
benefits of compliance for each model PWS under the proposed rule.
Because of this model PWS approach, SafeWater MCBC does not output any
results at the PWS level. Instead, the outputs are cost and benefit
estimates for 36 PWS categories, or strata. Each PWS category is
defined by system type (CWS and NTNCWS), primary water source (ground
or surface), and size category. Note EPA does not report state specific
strata although state location is utilized in the SafeWater MCBC model
(e.g., current state level regulatory limits on PFAS in drinking
water). The detailed output across these strata can be found in the
Chapter 5 of USEPA (2023j).
    For each PWS category, the model then calculates summary statistics
that describe the costs and benefits associated with the proposed rule
compliance. These summary statistics include total quantified costs of
the proposed regulatory requirement, total quantified benefits of the
proposed regulatory requirement, the variability in PWS-level costs
(e.g., 5th and 95th percentile system costs), and the variability in
household-level costs.

C. Method for Estimating Costs

    This section summarizes the cost elements and estimates total cost
of compliance for the proposed PFAS NPDWR discounted at 3 and 7
percent. EPA estimated the costs associated with

monitoring, administrative requirements, and both treatment and non-
treatment compliance actions associated with the proposed rule (USEPA,
2023j).
1. Public Water System (PWS) Costs
a. PWS Treatment and Non-Treatment Compliance Costs
    EPA estimated costs associated with engineering, installing,
operating, and maintaining PFAS removal treatment technologies,
including treatment media replacement and spent media destruction or
disposal, as well as non-treatment actions that some PWSs may take in
lieu of treatment, such as constructing new wells in an uncontaminated
aquifer or interconnecting with and purchasing water from a neighboring
PWS. EPA used SafeWater MCBC to apply costs for one of the treatment
technologies or non-treatment alternatives at each entry point in a PWS
estimated to be out of compliance with the proposed rule. For each
affected entry point, SafeWater MCBC selected from among the compliance
alternatives using a decision tree procedure, described in more detail
in USEPA (2023g) and (2023h). Next, the model estimated the cost of the
chosen compliance alternative using outputs from EPA's WBS cost
estimating models.
    Specifically, EPA used cost equations generated from the following
models (USEPA, 2023h):
     the GAC WBS model (USEPA, 2021g);
     the PFAS-selective IX WBS model (USEPA, 2021h);
     the centralized RO/NF WBS model (USEPA, 2021i); and
     the non-treatment WBS model (USEPA, 2021j).
    The Technologies and Costs (T&C) document (USEPA, 2023h) provides a
comprehensive discussion of each of the treatment technologies, their
effectiveness, and the WBS cost models as well as the equations used to
calculate treatment costs. In total, there are nearly 3,500 individual
cost equations across the categories of capital and operation and
maintenance (O&M) cost, water source, component level, flow, bed life
(for GAC and IX), residuals management scenarios (for GAC and IX), and
design type (for GAC).
b. Decision Tree for Technology Selection
    For entry points at which baseline PFAS concentrations exceed
regulatory thresholds, the decision tree selects a treatment technology
or non-treatment alternative using a two-step process that both:
     Determines whether to include or exclude each alternative
from consideration given the entry point's characteristics and the
regulatory option selected, and
     Selects from among the alternatives that remain viable
based on percentage distributions derived, in part, from data on recent
PWS actions in response to PFAS contamination.
    Inputs to the decision tree include the following:
     Influent concentrations of individual PFAS contaminants in
ppt;
     Entry point design flow in MGD;
     TOC influent to the new treatment process in mg/L.
    EPA relied on information from the national PFAS occurrence model
to inform influent PFAS concentrations. EPA relied on Geometries and
Characteristics of Public Water Supplies (USEPA, 2000f) and SDWIS
inventory information to derive entry point design flow. SafeWater MCBC
selects influent TOC using the distribution shown below in Table 25.

        Table 25--Frequency Distribution To Estimate Influent TOC
                                [In mg/L]
------------------------------------------------------------------------
            Percentile                Surface water       Ground water
------------------------------------------------------------------------
0.05..............................               0.65               0.35
0.15..............................                1.1               0.48
0.25..............................               1.38                0.5
0.35..............................                1.6                0.5
0.45..............................               1.85               0.58
0.5...............................               1.97               0.69
0.55..............................               2.14               0.75
0.65..............................               2.54                  1
0.75..............................               3.04               1.39
0.85..............................               3.63               2.01
0.95..............................               4.81                3.8
------------------------------------------------------------------------
Source: EPA's analysis of TOC concentrations in the SYR4 ICR database.

    Step 1 of the decision tree uses these inputs to determine whether
to include or exclude each treatment alternative from consideration in
the compliance forecast. For the treatment technologies (GAC, IX, and
RO/NF), this determination is based on estimates of each technology's
performance given available data about influent water quality and the
regulatory option under consideration.
    EPA assumes a small number of PWSs may be able to take non-
treatment actions in lieu of treatment. The viability of non-treatment
actions is likely to depend on the quantity of water being replaced.
Therefore, the decision tree considers non-treatment only for entry
points with design flows less than or equal to 3.536 MGD. EPA's WBS
model for non-treatment does not generate costs for flows greater than
this value, so the decision tree excludes non-treatment actions from
consideration above this flow. EPA estimates approximately 2% of
systems of this size will develop new wells and approximately 6-7% of
systems will elect to interconnect with another system to achieve
compliance.
    Step 2 of the decision tree selects a compliance alternative for
each entry point from among the alternatives that remain in
consideration after Step 1. Table 26 shows the initial compliance
forecast that is the starting point for this step. The percentages in
Table 26 consider data presented in the T&C document (USEPA, 2023h) on
actions PWSs have taken in response to PFAS contamination.
    To date, the majority of PWSs for which data are available have
installed GAC (USEPA, 2023h). The data in USEPA (2023h) suggest that an
increasing share of PWSs have selected IX in response to PFAS since the
first full-scale system treated with PFAS-selective IX in 2017. EPA
expects this trend to continue, so the initial percentages include
adjustments to

account for this expectation. In addition, the performance of GAC is
affected by the presence of TOC, as further described in the cost
chapter of the Economic Analysis (USEPA, 2023j). Accordingly, the table
includes adjusted distributions for systems with higher influent TOC.
    The list of compliance alternatives in Table 26 does not include
POU RO for small systems. At this time, EPA is not including POU RO in
the national cost estimates because the regulatory options under
consideration require treatment to concentrations below 70 ppt PFOA and
PFOS summed, the current certification standard for POU devices.
Therefore, the decision tree excludes POU RO from consideration and
proportionally redistributes the percentages among the other
alternatives.

                                                          Table 26--Initial Compliance Forecast
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Design flow less than  1 MGD   Design flow 1 to less than  10   Design flow greater than  or
                                                         --------------------------------               MGD                       equal to 10 MGD
                                                                                ---------------------------------------------------------------
                 Compliance alternative                   TOC  less than   TOC  greater   TOC  less than   TOC  greater   TOC  less than   TOC  greater
                                                           or  equal to   than  1.5 mg/L   or  equal to   than  1.5 mg/L   or  equal to   than  1.5 mg/L
                                                           1.5 mg/L  (%)        (%)        1.5 mg/L  (%)        (%)        1.5 mg/L  (%)        (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
GAC.....................................................              75              57              77              50              85              50
PFAS-selective IX.......................................              11              29              10              37              10              45
Central RO/NF...........................................               5               5               5               5               5               5
Interconnection.........................................               7               7               6               6               0               0
New Wells...............................................               2               2               2               2               0               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: EPA's analysis of TOC concentrations in the SYR4 ICR database.
Note: EPA is not including POU RO in the national cost estimates for the proposed rule because the regulatory options under consideration require
  treatment to concentrations below 70 ppt PFOA and PFOS summed, the current certification standard for POU devices. Therefore, the decision tree
  excludes POU RO from consideration and proportionally redistributes the percentages among the other alternatives.

    If all the compliance alternatives remain in consideration after
Step 1, the decision tree uses the forecast shown in Table 26 above. If
Step 1 eliminated on one or more of the alternatives, the decision tree
proportionally redistributes the percentages among the remaining
alternatives and uses the redistributed percentages.
    EPA's approach to estimating GAC and IX performance under the
proposed option and all alternatives considered is discussed in detail
within the cost chapter of the Economic Analysis (USEPA, 2023j).
c. Work Breakdown Structure Models
    The WBS models are spreadsheet-based engineering models for
individual treatment technologies, linked to a central database of
component unit costs. EPA developed the WBS model approach as part of
an effort to address recommendations made by the Technology Design
Panel (TDP), which convened in 1997 to review the Agency's methods for
estimating drinking water compliance costs (USEPA, 1997). The TDP
consisted of nationally recognized drinking water experts from EPA,
water treatment consulting companies, public as well as private water
utilities along with suppliers, equipment vendors, and Federal along
with State regulators in addition to cost estimating professionals.
    In general, the WBS approach involves breaking a process down into
discrete components for the purpose of estimating unit costs. The WBS
models represent improvements over past cost estimating methods by
increasing comprehensiveness, flexibility, and transparency. By
adopting a WBS-based approach to identify the components that should be
included in a cost analysis, the models produce a more comprehensive
assessment of the capital and operating requirements for a treatment
system.
    Each WBS model contains the work breakdown for a particular
treatment process and preprogrammed engineering criteria and equations
that estimate equipment requirements for user-specified design
requirements (e.g., system size and influent water quality). Each model
also provides unit and total cost information by component (e.g.,
individual items of capital equipment) and totals the individual
component costs to obtain a direct capital cost. Additionally, the
models estimate add-on costs (e.g., permits and land acquisition),
indirect capital costs, and annual O&M costs, thereby producing a
complete compliance cost estimate.
    Primary inputs common to all the WBS models include design flow and
average daily flow in MGD. Each WBS model has default designs (input
sets) that correspond to specified categories of flow, but the models
can generate designs for many other combinations of flows. To estimate
costs for PFAS compliance, EPA fit cost curves to the WBS estimates
across a range of flow rates, which is described in Chapter 5 of the
Economic Analysis (USEPA, 2023j).
    Another input common to all the WBS models is ``component level''
or ``cost level.'' This input drives the selection of materials for
items of equipment that can be constructed of different materials. For
example, a low-cost system might include fiberglass pressure vessels
and polyvinyl chloride (PVC) piping. A high-cost system might include
stainless steel pressure vessels and stainless-steel piping. The
component level input also drives other model assumptions that can
affect the total cost of the system, such as building quality and
heating and cooling. The component level input has three possible
values: low cost, mid cost, and high cost. The components used in each
of the estimated component/cost levels provide the treatment efficacy
needed to meet the regulatory requirements. Note that the level of
component (e.g., plastic versus resin or stainless-steel piping and
vessels) may impact the capital replacement rate but does not interfere
with treatment efficacy. EPA estimates the three levels of cost because
it has found that the choice of materials associated with the
installation of new treatment equipment often varies across drinking
water systems. These systems may, for example, choose to balance
capital cost with staff familiarity with certain materials and existing
treatment infrastructure. Given this experience, EPA models the
potential variability in treatment cost based on the three component/
cost levels. To estimate costs for PFAS treatment, EPA generated
separate cost equations for each of the

three component levels, thus creating a range of cost estimates for use
in national compliance cost estimates. EPA requests comment on the
range of component levels assumed and the range of estimated PFAS
treatment costs.
    The third input common to all the WBS models is system automation,
which allows the design of treatment systems that are operated manually
or with varying degrees of automation (i.e., with control systems that
reduce the need for operator intervention). Cost equations for system
automation are described in Chapter 5 of the Economic Analysis (USEPA,
2023j).
    The WBS models generate cost estimates that include a consistent
set of capital, add-on, indirect, and O&M costs. Table 27 below
identified these cost elements, which are common to all the WBS models
and included in the cost estimates below. As described below and
summarized in Tables 28-31 the WBS models also include technology-
specific cost elements. The documentation for the WBS models provide
more information on the methods and assumptions in the WBS models to
estimate the costs for both the technology-specific and common cost
elements (USEPA, 2021g; USEPA, 2021h; USEPA, 2021i; and USEPA, 2021j).
WBS model accuracy is described in Chapter 5 of the Economic Analysis
(USEPA, 2023j).

           Table 27--Cost Elements Included in All WBS Models
------------------------------------------------------------------------
         Cost category                     Components included
------------------------------------------------------------------------
Direct Capital Costs..........   Technology-specific equipment
                                 (e.g., vessels, basins, pumps,
                                 treatment media, piping, valves).
                                 Instrumentation and system
                                 controls.
                                 Buildings.
                                 Residuals management equipment.
Add-on Costs..................   Land.
                                 Permits.
                                 Pilot testing.
Indirect Capital Costs........   Mobilization and
                                 demobilization.
                                 Architectural fees for
                                 treatment building.
                                 Equipment delivery,
                                 installation, and contractor's overhead
                                 and profit.
                                 Sitework.
                                 Yard piping.
                                 Geotechnical.
                                 Standby power.
                                 Electrical infrastructure.
                                 Process engineering.
                                 Contingency.
                                 Miscellaneous allowance.
                                 Legal, fiscal, and
                                 administrative.
                                 Sales tax.
                                 Financing during construction.
                                 Construction management.
O&M Costs: Technology-specific   Operator labor for technology-
                                 specific tasks (e.g., managing backwash
                                 and media replacement).
                                 Materials for O&M of technology-
                                 specific equipment.
                                 Technology-specific chemical
                                 usage.
                                 Replacement of technology-
                                 specific equipment that occurs on an
                                 annual basis (e.g., treatment media).
                                 Energy for operation of
                                 technology-specific equipment (e.g.,
                                 mixers).
O&M Costs: Labor..............   Operator labor for O&M of
                                 process equipment.
                                 Operator labor for building
                                 maintenance.
                                 Managerial and clerical labor.
O&M Costs: Materials..........   Materials for maintenance of
                                 booster or influent pumps.
                                 Materials for building
                                 maintenance.
O&M Costs: Energy.............   Energy for operation of booster
                                 or influent pumps.
                                 Energy for lighting,
                                 ventilation, cooling, and heating.
O&M Costs: Residuals..........   Residuals management operator
                                 labor, materials, and energy.
                                 Residuals disposal and
                                 discharge costs.
------------------------------------------------------------------------

    The GAC model can generate costs for two types of design:
     Pressure designs where the GAC bed is contained in
stainless steel, carbon steel, or fiberglass pressure vessel;
     Gravity designs where the GAC bed is contained in open
concrete basins.
    Table 28 shows the technology-specific capital equipment and O&M
requirements included in the GAC model. These items are in addition to
the common WBS cost elements listed in the Cost Elements Included in
All WBS Models table above.

  Table 28--Technology-Specific Cost Elements Included in the GAC Model
------------------------------------------------------------------------
         Cost category                  Major components included
------------------------------------------------------------------------
Direct Capital Costs..........   Booster pumps for influent
                                 water.
                                 Contactors (either pressure
                                 vessels or concrete basins) that
                                 contain the GAC bed.
                                 Tanks and pumps for backwashing
                                 the contactors.
                                 GAC transfer and storage
                                 equipment.
                                 Spent GAC reactivation
                                 facilities (if on-site reactivation is
                                 selected).
                                 Associated piping, valves, and
                                 instrumentation.

O&M Costs: Labor..............   Operator labor for contactor
                                 maintenance (for gravity GAC designs).
                                 Operator labor for managing
                                 backwash events.
                                 Operator labor for backwash
                                 pump maintenance (if backwash occurs
                                 weekly or more frequently).
                                 Operator labor for GAC transfer
                                 and replacement.
O&M Costs: Materials..........   Materials for contactor
                                 maintenance (accounts for vessel
                                 relining in pressure designs, because
                                 GAC can be corrosive, and for concrete
                                 and underdrain maintenance in gravity
                                 designs).
                                 Materials for backwash pump
                                 maintenance (if backwash occurs weekly
                                 or more frequently).
                                 Replacement virgin GAC (loss
                                 replacement only if reactivation is
                                 selected).
O&M Costs: Energy.............   Operating energy for backwash
                                 pumps.
O&M Costs: Residuals..........   Discharge fees for spent
                                 backwash.
                                 Fees for reactivating spent GAC
                                 (if off-site reactivation is selected).
                                 Labor, materials, energy, and
                                 natural gas for regeneration facility
                                 (if on-site reactivation is selected).
                                 Disposal of spent GAC (if
                                 disposal is selected).
------------------------------------------------------------------------

    For small systems (less than 1 MGD) using pressure designs, the GAC
model assumes the use of package treatment systems that are pre-
assembled in a factory, mounted on a skid, and transported to the site.
The model estimates costs for package systems by costing all individual
equipment line items (e.g., vessels, interconnecting piping and valves,
instrumentation, and system controls) in the same manner as custom-
engineered systems. This approach is based on vendor practices of
partially engineering these types of package plants for specific
systems (e.g., selecting vessel size to meet flow and treatment
criteria). The model applies a variant set of design inputs and
assumptions that are intended to simulate the use of a package plant
and that reduce the size and cost of the treatment system. USEPA
(2021g) provides complete details on the variant design assumptions
used for package plants.
    To generate the GAC cost equations, EPA used the following key
inputs in the GAC model:
     For pressure designs, two vessels in series with a minimum
total empty bed contact time (EBCT) of 20 minutes;
     For gravity designs, contactors in parallel with a minimum
total EBCT of 20 minutes; and
     Bed life varying over a range from 5,000 to 150,000 BV.
    EPA generated separate cost equations for two spent GAC management
scenarios:
     Off-site reactivation under current RCRA non-hazardous
waste regulations
     Off-site disposal as a hazardous waste and replacement
with virgin GAC (i.e., single use operation).
    The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
    Table 29 shows the technology-specific capital equipment and O&M
requirements included in the PFAS selective IX model. These items are
in addition to the common WBS cost elements listed in the Cost Elements
Included in All WBS Models table above.

    Table 29--Technology-Specific Cost Elements Included in the PFAS-
                           Selective IX Model
------------------------------------------------------------------------
         Cost category                  Major components included
------------------------------------------------------------------------
Direct Capital Costs..........   Booster pumps for influent
                                 water.
                                 Pre-treatment cartridge
                                 filters.
                                 Pressure vessels that contain
                                 the resin bed.
                                 Tanks and pumps for initial
                                 rinse and (optionally) backwash of the
                                 resin bed.
                                 Tanks (with secondary
                                 containment), pumps and mixers for
                                 delivering sodium hydroxide for use in
                                 post-treatment corrosion control
                                 (optional).
                                 Associated piping, valves, and
                                 instrumentation.
O&M Costs: Labor..............   Operator labor for pre-
                                 treatment filters.
                                 Operator labor for managing
                                 backwash/rinse events.
                                 Operator labor for backwash
                                 pump maintenance (only if backwash
                                 occurs weekly or more frequently).
                                 Operator labor for resin
                                 replacement.
O&M Costs: Materials..........   Replacement cartridges for pre-
                                 treatment filters.
                                 Materials for backwash pump
                                 maintenance (only if backwash occurs
                                 weekly or more frequently).
                                 Chemical usage (if post-
                                 treatment corrosion control is
                                 selected).
                                 Replacement virgin PFAS-
                                 selective resin.
O&M Costs: Energy.............   Operating energy for backwash/
                                 rinse pumps.
O&M Costs: Residuals..........   Disposal of spent cartridge
                                 filters.
                                 Discharge fees for spent
                                 backwash/rinse.
                                 Disposal of spent resin.
------------------------------------------------------------------------

    For small systems (less than 1 MGD), the PFAS-selective IX model
assumes the use of package treatment systems that are pre-assembled in
a factory, mounted on a skid, and transported to the site. The IX model
estimates costs for package systems using an approach similar to that
described for the GAC model, applying a variant set of inputs and
assumptions that reduce the size and cost of the treatment system.
USEPA (2021j) provides complete details on the variant design
assumptions used for IX package plants.
    To generate the IX cost equations, EPA used the following key
inputs in the PFAS-selective IX model:
     Two vessels in series with a minimum total EBCT of 6
minutes.
     Bed life varying over a range from 20,000 to 440,000 BV.

    EPA generated separate cost equations for two spent resin
management scenarios:
     Spent resin managed as non-hazardous and sent off-site for
incineration.
     Spent resin managed as hazardous and sent off-site for
incineration.
    The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
    Table 30 shows the technology-specific capital equipment and O&M
requirements included in the model for RO/NF (USEPA, 2021i). These
items are in addition to the common WBS cost elements listed in listed
in the Cost Elements Included in All WBS Models table above.

 Table 30--Technology-Specific Cost Elements Included in the RO/NF Model
------------------------------------------------------------------------
         Cost category                  Major components included
------------------------------------------------------------------------
Direct Capital Costs..........   High-pressure pumps for
                                 influent water and (optionally)
                                 interstage pressure boost.
                                 Pre-treatment cartridge
                                 filters.
                                 Tanks, pumps, and mixers for
                                 pretreatment chemicals.
                                 Pressure vessels, membrane
                                 elements, piping, connectors, and steel
                                 structure for the membrane racks.
                                 Valves for concentrate control
                                 and (optionally) per-stage throttle.
                                 Tanks, pumps, screens,
                                 cartridge filters, and heaters for
                                 membrane cleaning.
                                 Equipment, including dedicated
                                 concentrate discharge piping, for
                                 managing RO/NF concentrate and spent
                                 cleaning chemicals.
                                 Associated pipes, valves, and
                                 instrumentation.
O&M Costs: Labor..............   Operator labor for pre-
                                 treatment filters.
                                 Operator labor for routine O&M
                                 of membrane units.
                                 Operator labor to maintain
                                 membrane cleaning equipment.
O&M Costs: Materials..........   Replacement cartridges for pre-
                                 treatment filters.
                                 Chemical usage for
                                 pretreatment.
                                 Maintenance materials for pre-
                                 treatment, membrane process, and
                                 cleaning equipment.
                                 Replacement membrane elements.
                                 Chemical usage for cleaning.
O&M Costs: Energy.............   Energy for high-pressure
                                 pumping.
O&M Costs: Residuals..........   Disposal costs for spent
                                 cartridge filters and membrane
                                 elements.
------------------------------------------------------------------------

    The RO/NF model includes three default ground waters and three
default surface waters, ranging from high to low quality (i.e., from
low to high total dissolved solids and scaling potential). To generate
the cost equations, EPA used the model's default high-quality influent
water parameters to reflect the incremental cost of removing PFAS from
otherwise potable water. EPA used the following additional key inputs
and assumptions:
     For systems larger than approximately 0.5 MGD, target
recovery rates of 80 percent for ground water and 85 percent for
surface water.
     Target recovery rates of 70 to 75 percent for smaller
systems.
     Flux rates of 19 gallons per square foot per day (gfd) for
ground water and 15 to 16 gfd for surface water.
     Direct discharge of RO/NF concentrate to a permitted
outfall on a non-potable water body (e.g., ocean or brackish estuary)
via 10,000 feet of buried dedicated piping.
    The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
    USEPA (2021j) provides a complete description of the engineering
design process used by the WBS model for nontreatment actions. The
model can estimate costs for two nontreatment alternatives:
interconnection with another system and drilling new wells to replace a
contaminated source. Table 31 below shows the technology-specific
capital equipment and O&M requirements included in the model for each
alternative.

    Table 31--Technology-Specific Cost Elements Included in the Non-
                             Treatment Model
------------------------------------------------------------------------
                                    Major components    Major components
          Cost category               included for      included for new
                                     interconnection         wells
------------------------------------------------------------------------
Direct Capital Costs.............   Booster     Well
                                    pumps or pressure   casing, screens,
                                    reducing valves     and plugs.
                                    (depending on       Well
                                    pressure at         installation
                                    supply source).     costs including
                                    Concrete    drilling,
                                    vaults (buried)     development,
                                    for booster pumps   gravel pack, and
                                    or pressure         surface seals.
                                    reducing valves.    Well
                                                pumps.
                                    Interconnecting     Piping
                                    piping (buried)     (buried) and
                                    and valves.         valves to
                                                        connect the new
                                                        well to the
                                                        system.
O&M Costs: Labor.................   Operator    Operator
                                    labor for O&M of    labor for
                                    booster pumps or    operating and
                                    pressure reducing   maintaining well
                                    valves (depending   pumps and
                                    on pressure at      valves.
                                    supply source)
                                    and
                                    interconnecting
                                    valves.
O&M Costs: Materials.............   Cost of
                                    purchased water.    Materials for
                                    Materials   maintaining well
                                    for maintaining     pumps.
                                    booster pumps (if
                                    required by
                                    pressure at
                                    supply source).
O&M Costs: Energy................   Energy      Energy
                                    for operating       for operating
                                    booster pumps (if   well pumps.
                                    required by
                                    pressure at
                                    supply source).
------------------------------------------------------------------------

    To generate the cost equations, EPA used the following key inputs
in the non-treatment model for interconnection:
     An interconnection distance of 10,000 feet;

     Minimal differences in pressure between the supplier and
the purchasing system, so that neither booster pumps nor pressure
reducing valves are needed;
     An average cost of purchased water of $3.00 per thousand
gallons in 2020 dollars.
    For new wells, EPA used the following key inputs:
     A maximum well capacity of 500 gallons per minute (gpm),
such that one new well is installed per 500 gpm of water production
capacity required;
     A well depth of 250 feet;
     500 feet of distance between the new wells and the
distribution system.
    The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
d. Incremental Treatment Costs
    EPA has estimated the national level costs of the proposed rule
associated with PFOA, PFOS, and PFHxS. Given the available occurrence
data for the other compounds in the proposed rule (PFNA, HFPO-DA, and
PFBS) and the regulatory thresholds under consideration, EPA did not
model national costs associated with potential HI exceedances as a
direct result of these compounds. To assess the potential impact of
these compounds, EPA conducted an analysis of the additional, or
incremental, system level impact that occurrence of these compounds
would have on treatment costs. To do so, EPA used a model system
approach. For further detail on the assumptions and findings of EPA's
analysis of incremental costs, please see Chapter 5 in USEPA (2023j)
and Appendix N in USEPA (2023i).
e. PWS Implementation Administration Costs
    EPA estimated PWS costs associated with one-time actions to begin
implementation of the rule including reading and understanding the rule
and attending training provided by primacy agencies. EPA assumes that
systems will conduct these activities during years one through three of
the period of analysis. Table 32 lists the data elements and
corresponding values associated with calculating the costs of these
one-time implementation administration actions.

          Table 32--Implementation Administration Startup Costs
                                 [2021$]
------------------------------------------------------------------------
          Data element description                Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........  $35.48 (systems <=3,300).
                                             $37.84 (systems 3,301-
                                              10,000).
                                             $39.94 (systems 10,001-
                                              50,000).
                                             $41.70 (systems 50,001-
                                              100,000).
                                             $48.74 (systems >100,000).
The average hours per system to read and     4 hours per system.
 adopt the rule.
The average hours per system to attend one-  16 hours per system
 time training provided by primacy agencies.  (systems <=3,300).
                                             32 hours per system
                                              (systems >3,300).
------------------------------------------------------------------------

    Estimated national annualized PWS implementation and administration
startup costs for the proposed option are $1.71 million (3% discount
rate) and $3.52 million (7% discount rate). National annualized PWS
cost estimates are further summarized in Table 37.
f. PWS Monitoring Costs
    EPA assumes that the proposed rule will require initial and long-
term monitoring. As Table 33 shows, surface and ground water systems
serving 10,000 or more people will collect one sample each quarter, at
each entry point, during the initial 12-month monitoring period.
Surface water systems serving 10,000 or fewer people are also required
to collect a quarterly sample at each entry point during the initial
12-month period. Ground water systems that serve 10,000 or fewer people
will be required to sample once at each entry point on a semi-annual
basis for the first 12-month monitoring period.
    Long-term monitoring requirements differ based on two factors: (1)
system size, and (2) whether a system can demonstrate during the
initial monitoring period that they are ``reliably and consistently''
below the proposed MCLs for PFAS. EPA has set the PWS size threshold at
systems serving 3,300 or fewer people. The threshold for systems to
demonstrate that they are ``reliably and consistently'' below the
proposed MCLs is set at a trigger level of one-third the MCLs for PFOA
or PFOS (1.3 ppt) or the HI (0.33). For systems below the trigger level
values during the initial 12-month monitoring period and in future
long-term monitoring periods may conduct triennial monitoring. Systems
serving 3,300 or fewer people will collect one triennial sample per
entry point. Systems providing water for more than 3,300 people will
take one sample in two consecutive quarters at each entry point,
totaling two samples in each triennial period. For systems with
concentration values at or above the trigger level regardless of system
size, a quarterly sample must be taken at each entry point.
    For any samples that have a detection, the system will analyze the
field reagent blank samples collected at the same time as the
monitoring sample. Systems that have an MCL exceedance will collect one
additional sample from the relevant entry point to confirm the results.

                   Table 33--Initial and Long-Term Sampling Frequencies per System Entry Point
----------------------------------------------------------------------------------------------------------------
                                                                Long-Term
                                              Long-term      monitoring: \a\     Long-term monitoring: \1\ PFAS
 Initial  monitoring    Initial 12-month     monitoring      PFAS detection      detection >=1.3 ppt  (PFOA or
system size  category  monitoring  period    system size    <1.3 ppt (PFOA or          PFOS) or HI >=0.33
                                              category      PFOS) or HI <0.33
----------------------------------------------------------------------------------------------------------------
<=10,000.............  Surface Water: 1           <=3,300  1 triennial sample  1 sample every quarter.
                        sample every
                        quarter.
                       Ground Water: 1
                        sample every 6-
                        month period.

>10,000..............  Surface Water and           >3,300  2 triennial         1 sample every quarter.
                        Ground Water: 1                     samples (1 sample
                        sample every                        in two
                        quarter.                            consecutive
                                                            quarters).
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ EPA used the following thresholds to distinguish whether PFAS concentrations are reliably and consistently
  below the MCL: PFOA and PFOS--one-third the MCL for each option; PFHxS--one-third the health benchmark of 9
  ppt or 3 ppt.

    For the national cost analysis, EPA assumes that systems with
either UCMR 5 data or monitoring data in the State PFAS Database (see
Section 3.1.4 in USEPA, 2023j) will not need to conduct the initial
year of monitoring. As a simplifying assumption for the cost analysis,
EPA assumes all systems serving a population of greater than 3,300 have
UCMR 5 data and those with 3,300 or less do not. For the State PFAS
Database, EPA relied on the PWSIDs stored in the database and exempted
those systems from the first year of monitoring in the cost analysis.
Note these simplifying assumptions may result in a small underestimate
of initial monitoring costs. Under UCMR 5, individual water systems
would be able to request the full release of data from the labs for use
in determining their compliance monitoring frequency. PWSs may be able
to use these lab analyses to demonstrate a ``below trigger level''
concentration using the UCMR 5 analyses by following up with the lab
for a more detailed results report. EPA requests comment on these
underlying assumptions.
    EPA used system-level distributions, as described in Cadwallader et
al. (2022), to simulate entry point concentrations and estimate PFAS
occurrence relative to the proposed option MCLs and trigger levels.
Based on these occurrence distributions, EPA estimates that the large
majority of water systems subject to the proposed rule (approx. 52,000)
will have EPs with concentrations below the proposed trigger level and
would conduct reduced monitoring on a triennial basis. EPA estimates
that the remainder of water systems subject to the proposed rule
(approx. 14,000) will have at least one or more EPs exceed the proposed
trigger level and therefore would be required to conduct quarterly
monitoring. EPA requests comment on these estimates and the underlying
assumptions.
    EPA assumes that systems with an MCL exceedance will implement
actions to comply with the MCL by the compliance date. EPA assumes a
treatment target, for systems required to treat for PFAS, that includes
a margin of safety so finished water PFAS levels at these systems are
80 percent of the MCL or HI. This target is insufficient to meet the
triennial monitoring threshold. Therefore, systems implementing
treatment will continue with quarterly monitoring. All other systems
that do not have PFAS concentrations at or below the trigger level
threshold will also continue quarterly monitoring.
    For all systems, the activities associated with the sample
collection in the initial 12-month monitoring period are the labor
burden and cost for the sample collection and analysis, as well as a
review of the sample results. Table 34 presents the data elements and
corresponding values associated with calculating sampling costs during
the implementation monitoring period.

                        Table 34--Sampling Costs
                                 [2021$]
------------------------------------------------------------------------
          Data element description                Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........  $35.48 (systems <=3,300).
                                             $37.84 (systems 3,301-
                                              10,000).
                                             $39.94 (systems 10,001-
                                              50,000).
                                             $41.70 (systems 50,001-
                                              100,000).
                                             $48.74 (systems >100,000).
The number of samples per entry point per    2 samples (Ground Water
 monitoring round for the initial             systems <=10,000).
 monitoring in Year 1.                       4 samples (all systems)
                                              \1\.
The number of samples per entry point per    4 samples (all other
 long-term monitoring year for entry points   systems).
 that exceed the triennial monitoring
 threshold.
The number of samples per entry point per    1 sample (systems <=3,300).
 long-term monitoring round for entry        2 samples (systems >3,300).
 points that meet the triennial threshold.
The hours per sample to travel to sampling   1 hour.
 locations, collect samples, record any
 additional information, submit samples to
 a laboratory, and review results.
The laboratory analysis cost per sample for  $376.
 EPA Method 533.
The laboratory analysis cost per sample for  $302.
 EPA Method 537.1.
The laboratory analysis cost per sample for  $327.\2\
 field reagent blank under EPA Method 533.
The laboratory analysis cost per sample for  $266.\ 2\
 the field reagent blank under EPA Method
 537.1.
------------------------------------------------------------------------
Notes:
\1\ Systems greater than 3,300 will rely on UCMR 5 data and a subset of
  other systems will rely on data in the State PFAS Monitoring Database
  discussed in USEPA, 2023j.
\2\ This incremental sample cost applies to all samples that exceed
  MDLs. EPA used the Method 537.1 detection limits to apply this cost
  because Method 533 does not include detection limits.

    Estimated national annualized PWS sampling costs for the proposed
option are $90.32 million (3 discount rate) and $92.97 million (7%
discount rate). National annualized PWS cost estimates are further
summarized in Table 37.

g. Treatment Administration Costs
    Any system with an MCL exceedance adopts either a treatment or non-
treatment alternative to comply with the proposed rule. The majority of
systems are anticipated to install treatment technologies while a
subset of systems will choose alternative methods. EPA assumes that
systems will bear administrative costs associated with these treatment
or non-treatment compliance actions (i.e., permitting costs). EPA
assumes that systems will install treatment in the fourth year of the
period of analysis. Table 35 presents the data elements and
corresponding values associated with calculating treatment
administration costs.

                Table 35--Treatment Administration Costs
                                 [2021$]
------------------------------------------------------------------------
          Data element description                Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........  $35.48 (systems <=3,300).
                                             $37.84 (systems 3,301-
                                              10,000).
                                             $39.94 (systems 10,001-
                                              50,000).
                                             $41.70 (systems 50,001-
                                              100,000).
                                             $48.74 (systems >100,000).
The hours per entry point for a system to    3 hours (systems <=100)
 notify, consult, and submit a permit        5 hours (systems 101-500).
 request for treatment installation \a\.
                                             7 hours (systems 501-
                                              1,000).
                                             12 hours (systems 1,001-
                                              3,300).
                                             22 hours (systems 3,301-
                                              50,000).
                                             42 hours (systems >50,000).
The hours per entry point for a system to    6 hours.
 notify, consult, and submit a permit
 request for source water change or
 alternative method \1\.
------------------------------------------------------------------------
Notes:
\1\ EPA applied the cost per entry point for this economic analysis
  because the notification, consultation, and permitting process occurs
  for individual entry points.

h. Public Notification (PN) Costs
    EPA's cost analysis assumes full compliance with the rule
throughout the period of analysis and, as a result, EPA does not
estimate costs for the PN requirements in the proposed rule for systems
with certain violations. The proposed rule designates MCL violations
for PFAS as Tier 2, which requires systems to provide PN as soon as
practical, but no later than 30 days after the system learns of the
violation. The system must repeat notice every three months if the
violation or situation persists unless the primacy agency determines
otherwise. At a minimum, systems must give repeat notice at least once
per year. The proposed rule also designates monitoring and testing
procedure violations as Tier 3, which requires systems to provide
public notice not later than one year after the system learns of the
violation. The system must repeat the notice annually for as long as
the violation persists. For approximate estimates of the potential
burden associated with Tier 2 and 3 PNs, please see USEPA (2023j).
i. Primacy Agency Costs
    EPA assumes that primacy agencies will have upfront implementation
costs as well as costs associated with system actions related to
sampling and treatment. The activities that primacy agencies are
expected to carry out under the proposed rule include:
     Reading and understanding the rule and adopting regulatory
requirements,
     Providing primacy agency officials training for the rule
implementation,
     Providing systems with training and technical assistance
during the rule implementation,
     Reporting to EPA on an ongoing basis any PFAS-specific
information under 40 CFR 142.15 regarding violations as well as
enforcement actions and general operations of PWS programs,
     Reviewing the sample results during the implementation
monitoring period and the SMF period, and
     Reviewing and consulting with systems on the installation
of treatment technology or alternative methods, including source water
change.
    With the exception of the first four activities listed above, the
primary agency burdens are incurred in response to action taken by
PWSs; for instance, the cost to primacy agencies of reviewing sample
results depends on the number of samples taken at each entry point by
each system under an Agency's jurisdiction. Table 36 presents the data
elements and corresponding values associated with calculating primacy
agency costs.

                     Table 36--Primacy Agency Costs
                                 [2021$]
------------------------------------------------------------------------
          Data element description                Data element value
------------------------------------------------------------------------
The labor rate per hour for primacy          $58.14.
 agencies \1\.
The average hours per primacy Agency to      416 hours per primacy
 read and understand the rule, as well as     Agency.
 adopt regulatory requirements.
The average hours per primacy Agency to      250 hours per primacy
 provide initial training to internal staff.  Agency.
The average hours per primacy Agency to      2,080 hours per primacy
 provide initial training and technical       Agency.
 assistance to systems.
The average hours per primacy Agency to      0.
 report annually to EPA information under
 40 CFR 142.15 regarding violations,
 variances and exemptions, enforcement
 actions and general operations of State
 PWS programs.
The hours per sample for a primacy Agency    1 hour.
 to review sample results.

The hours per entry point for a primacy      3 hours (systems <=100).
 agency to review and consult on             5 hours (systems 101-500).
 installation of a TT \2\.                   7 hours (systems 501-
                                              1,000).
                                             12 hours (systems 1,001-
                                              3,300).
                                             22 hours (systems 3,301-
                                              50,000).
                                             42 hours (systems >50,000).
The hours per entry point for a primacy      4 hours.
 agency to review and consult on a source
 water change \2\.
------------------------------------------------------------------------
Notes:
\1\ In USBLS (2022), State employee wage rate of $33.91 from National
  Occupational Employment and Wage Estimates, United States, BLS SOC
  Code 19-2041, ``State Government, excluding schools and hospitals--
  Environmental Scientists and Specialists, Including Health,'' hourly
  mean wage rate. May 2020 data (published in March 2021): https://www.bls.gov/oes/current/oes192041.htm. Wages are loaded using a factor
  of 62.2 from the Bureau of Labor Statistics (BLS) Employer Costs for
  Employee Compensation report, Table 3, March 2020. Percent of total
  compensation--Wages and Salaries--All Workers--State and Local
  Government Workers (https://www.bls.gov/news.release/archives/ecec_06182020.pdf). See worksheet BLS Table 3. The final loaded wage
  is adjusted for inflation.
\2\ EPA assumes that the proposed PFAS rule will have no discernable
  incremental burden for quarterly or annual reports to SDWIS/Fed.

    Estimated national annualized primacy agency costs for the proposed
option are $7.96 million (3% discount rate) and $8.76 million (7%
discount rate). National annualized cost estimates are further
summarized in Table 37.
    In addition to the costs described above, a primacy agency may also
have to review the certification of any Tier 2 or 3 PNs sent out by
systems. EPA assumes full compliance with the proposed rule and
therefore does not include this cost in national estimated cost totals
but provides a brief discussion of the possible primacy agency burden
associated with this component in USEPA (2023j).
    In Table 37, EPA summarizes the total annualized quantified cost of
the proposed option at both a 3 percent and 7 percent discount rate
expressed in millions of 2021 dollars. The first three rows show the
annualized PWS sampling costs, the annualized PWS implementation and
administrative costs, and the annualized PWS treatment costs. The
fourth row shows the sum of the annualized PWS costs. At a 3 percent
discount rate, the expected annualized PWS costs are $769 million. The
uncertainty range for annualized PWS costs are $699 million to $862
million. Finally, annualized primacy agency implementation and
administrative costs are added to the annualized PWS costs to calculate
the total annualized cost of the proposed option. At a 3 percent
discount rate, the expected total annualized cost of the proposed rule
is $777 million. The uncertainty range for the total annualized costs
of the proposed rule is $706 million to $872 million. At a 7 percent
discount rate, the expected total annualized cost of the proposed
option is $1.211 billion, while the uncertainty range for the total
annualized costs of the proposed option is $1.103 billion to $1.353
billion. Note as described in section j. Data Limitations and
Uncertainties in the Cost Analysis below, given the available
occurrence data for the other compounds in the proposed rule (PFNA,
HFPO-DA, and PFBS) and the regulatory thresholds under consideration,
EPA did not model national costs associated with potential HI
exceedances as a direct result of these compounds; therefore, the
additional treatment cost, from co-occurrence of PFNA, HFPO-DA, PFBS or
other PFAS, at systems already required to treat because of PFOA, PFOS,
or PFHxS MCL and HI exceedances are not quantitatively assessed in the
national cost estimates. Nor are treatment costs for systems that
exceed the HI based on the combined occurrence of PFNA, HFPO-DA, PFBS,
and PFHxS (where PFHxS itself does not exceed 9 ppt) included in the
national monetized cost estimates. These potential additional costs are
described in Section <IP_ADDRESS> of USEPA (2023j) and Appendix N of USEPA
(2023i).
    In these sections of the Economic Analysis, EPA uses a model system
approach to explore the potential costs of treatment at a system that:
(1) has no detections of PFOA, PFOS, or PFHxS (modeled in the national
analysis), but has occurrence of all the other PFAS included in the HI
(HFPO-DA, PFBS, and PFNA), and (2) has occurrence of PFOA, PFOS, and
PFHxS identical to the national model but also has occurrence of all
the other PFAS included in the HI (HFPO-DA, PFBS, and PFNA). The first
type of system represents additional systems that are not currently
captured in the national costs but would incur treatment costs under
the HI. The second type of system illustrates a range of potential
incremental treatment costs for systems that are already treating to
remove PFOA, PFOS, and/or PFHxS in the national cost analysis. EPA
analyzed system costs for GAC, IX, and OR for two scenarios: high
occurrence of the three PFAS not included in the national analysis and
medium occurrence of those PFAS. The model system analysis found for IX
and RO/NF that costs were slightly less or the same as modeled system
treatment costs under a national cost scenario across both types of
systems defined above, the medium and high PFAS scenarios, and across
model system size categories. The assessment of GAC produced more
variability in results. For systems that are not currently captured in
the national costs but would incur treatment costs under the HI, EPA
found under the medium PFAS concentrations cost would be the same or
slightly less than a model system treating for the PFAS included in the
national analysis. The systems representing the potential incremental
treatment costs for systems that are already treating to remove PFOA,
PFOS, and/or PFHxS in the national cost analysis, the model system
analysis under the medium scenario found that costs of treatment would
increase by 1-9 percent, depending on system size and other cost
assumptions associated with bed life changes as a result of TOC
assumptions. Under the high PFAS scenario across both types of systems
GAC treatment costs were found to range from 0 to 77% higher than
treatment of national PFAS values depending on system size and other
costing assumptions like bed life. This high-end cost increase of 77
percent is unlikely to occur at a large number of systems given the
assumed high levels of PFAS and the assumed high levels of

TOC at 2 mg/L. It is also likely that systems facing these GAC
treatment cost will select IX or RO/NF as lower cost alternative
treatments and therefore national cost estimates are unlikely to be
substantially underestimated. EPA requests comment on these estimated
impacts and the assumption that HI exceedances resulting from these
additional compounds will not significantly impact overall compliance
costs.
    The national annualized costs below do not reflect costs of
hazardous waste disposal for GAC and IX media. As a general matter, EPA
notes that such wastes are not currently regulated under Federal law as
a hazardous waste. To address stakeholder concerns, including those
raised during the SBREFA process, EPA conducted a sensitivity analysis
with an assumption of hazardous waste disposal for illustrative
purposes only. As part of this analysis, EPA generated a second full
set of unit cost curves that are identical to the curves used for the
national cost analysis with the exception that spent GAC and spent IX
resin are considered hazardous. EPA acknowledges that if Federal
authorities later determine that PFAS-contaminated wastes require
handling as hazardous wastes, the residuals management costs are
expected to be higher. See Appendix N.2 of USEPA (2023j) for a
sensitivity analysis describing the potential increase in costs
associated with hazardous waste disposal (USEPA, 2023i).

                                                  Table 37--National Annualized Costs, Proposed Option
                                              [PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               3% Discount rate                            7% Discount rate
                                                                 ---------------------------------------------------------------------------------------
                                                                  5th Percentile   Expected        95th       5th Percentile   Expected        95th
                                                                        \1\          value    Percentile \1\        \1\          value    Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs...................................          $76.12      $90.32         $106.95          $78.54      $92.97         $109.19
Annualized PWS Implementation and Administration Costs..........            1.71        1.71            1.71            3.52        3.52            3.52
Annualized PWS Treatment Costs..................................          617.05      676.56          762.05        1,008.88    1,105.66        1,232.92
Total Annualized PWS Costs \2\ \3\ \4\..........................          698.90      768.57          861.78        1,096.29    1,202.09        1,341.19
Primacy Agency Rule Implementation and Administration Cost......            6.86        7.96            9.18            7.67        8.76           10.04
Total Annualized Rule Costs \2\ \3\ \4\.........................          705.85      776.54          871.50        1,102.71    1,210.91        1,352.71
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
  range does not include the uncertainty described in Table 41.
\2\ Total quantified national cost values do not include the incremental treatment costs associated with the co-occurrence of HFPO-DA, PFBS, and PFNA at
  systems required to treat for PFOA, PFOS, and PFHxS. The total quantified national cost values do not include treatment costs for systems that would
  be required to treat based on HI exceedances apart from systems required to treat because of PFHxS occurrence alone. See Appendix N, Section 3 of the
  Economic Analysis (USEPA, 2023i) for additional detail on co-occurrence incremental treatment costs and additional treatment costs at systems with HI
  exceedances.
\3\ PFAS-contaminated wastes are not considered hazardous wastes at this time and therefore total costs reported in this table do not include costs
  associated with hazardous waste disposal of spent filtration materials. To address stakeholder concerns about potential costs for disposing PFAS-
  contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
  waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\4\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
  annualized costs in this table.

    In Table 38, Table 39, and Table 40, EPA summarizes the total
annualized quantified cost of options 1a, 1b, and 1c, respectively.

                                                     Table 38--National Annualized Costs, Option 1a
                                                     [PFOA and PFOS MCLs of 4.0 ppt; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               3% Discount rate                            7% Discount rate
                                                                 ---------------------------------------------------------------------------------------
                                                                  5th Percentile   Expected        95th             5th        Expected        95th
                                                                        \1\          value    Percentile \1\   Percentile\1\     value    Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs...................................          $75.54      $89.45         $105.44          $77.76      $92.10         $108.29
Annualized PWS Implementation and Administration Costs..........            1.71        1.71            1.71            3.52        3.52            3.52
Annualized PWS Treatment Costs..................................          601.03      661.40          745.31          984.54    1,079.05        1,205.22
Total Annualized PWS Costs \2\ \3\..............................          680.76      752.56          848.52        1,066.70    1,174.69        1,314.49
Primacy Agency Rule Implementation and Administration Cost......            6.83        7.89            9.12            7.59        8.69            9.96
Total Annualized Rule Costs \2\ \3\.............................          687.54      760.45          857.04        1,078.01    1,183.41        1,324.41
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
  range does not include the uncertainty described in Table 41.

\2\ PFAS-contaminated wastes are not considered hazardous wastes at this time and therefore total costs reported in this table do not include costs
  associated with hazardous waste disposal of spent filtration materials. To address stakeholder concerns about potential costs for disposing PFAS-
  contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
  waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
  annualized costs in this table.

                                                     Table 39--National Annualized Costs, Option 1b
                                                     [PFOA and PFOS MCLs of 5.0 ppt; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               3% Discount rate                            7% Discount rate
                                                                 ---------------------------------------------------------------------------------------
                                                                  5th Percentile   Expected        95th             5th        Expected        95th
                                                                        \1\          value    Percentile \1\   Percentile\1\     value    Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs...................................          $66.40      $78.38          $93.04          $68.77      $80.92          $95.70
Annualized PWS Implementation and Administration Costs..........            1.71        1.71            1.71            3.52        3.52            3.52
Annualized PWS Treatment Costs..................................          479.50      527.00          597.91          778.40      853.94          960.05
Total Annualized PWS Costs \2\ \3\..............................          549.52      607.08          686.67          854.64      938.38        1,052.52
Primacy Agency Rule Implementation and Administration Cost......            6.03        6.94            8.03            6.74        7.69            8.84
Total Annualized Rule Costs \2\ \3\.............................          555.94      614.03          694.18          860.01      946.07        1,064.56
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
  range does not include the uncertainty described in Table 41.
\2\ PFAS-contaminated wastes are not considered hazardous wastes at this time and therefore total costs reported in this table do not include costs
  associated with hazardous waste disposal of spent filtration materials. To address stakeholder concerns about potential costs for disposing PFAS-
  contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
  waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
  annualized costs in this table.

                                 Table 40--National Annualized Costs, Option 1c
                                 [PFOA and PFOS MCLs of 10.0 ppt; Million $2021]
----------------------------------------------------------------------------------------------------------------
                                                  3% Discount rate                     7% Discount rate
                                       -------------------------------------------------------------------------
                                            5th                     95th         5th                     95th
                                         Percentile   Expected   Percentile   Percentile   Expected   percentile
                                            \1\        value        \1\          \1\        value        \1\
----------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs.........       $46.19     $52.84       $64.34       $48.33     $55.14       $66.82
Annualized PWS Implementation and              1.71       1.71         1.71         3.52       3.52         3.52
 Administration Costs.................
Annualized PWS Treatment Costs........       214.02     233.87       257.12       336.54     367.40       404.42
Total Annualized PWS Costs \2\ \3\....       264.49     288.43       317.66       390.39     426.06       468.83
Primacy Agency Rule Implementation and         4.28       4.76         5.65         4.91       5.40         6.28
 Administration Cost..................
Total Annualized Rule Costs \2\ \3\...       269.11     293.19       323.45       395.35     431.46       474.75
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost
  components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
  XIII.I of this preamble and Table 71. This range does not include the uncertainty described in Table 41.
\2\ PFAS-contaminated wastes are not considered hazardous wastes at this time and therefore total costs reported
  in this table do not include costs associated with hazardous waste disposal of spent filtration materials. To
  address stakeholder concerns about potential costs for disposing PFAS-contaminated wastes as hazardous should
  they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
  waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
  2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs
  would have on the estimated monetized total annualized costs in this table.

j. Data Limitations and Uncertainties in the Cost Analysis
    Table 41 lists data limitations and characterizes the impact on the
quantitative cost analysis. EPA notes that in most cases it is not
possible to judge the extent to which a particular limitation or
uncertainty could affect the cost analysis. EPA provides the potential
direction of the impact on the cost estimates when possible but does
not prioritize the entries with respect to the impact magnitude.

                Table 41--Limitations That Apply to the Cost Analysis for the Proposed PFAS Rule
----------------------------------------------------------------------------------------------------------------
        Uncertainty/assumption          Effect on quantitative analysis                   Notes
----------------------------------------------------------------------------------------------------------------
WBS engineering cost model assumptions  Uncertain......................  The WBS engineering cost models require
 and component costs.                                                     many design and operating assumptions
                                                                          to estimate treatment process
                                                                          equipment and operating needs. Chapter
                                                                          5 of the Economic Analysis (USEPA,
                                                                          2023j) addressed the bed life
                                                                          assumption. The Technologies and Costs
                                                                          document (USEPA, 2023h) and individual
                                                                          WBS models in the rule docket provide
                                                                          additional information. The component-
                                                                          level costs approximate national
                                                                          average costs, which can over- or
                                                                          under-estimate costs at systems
                                                                          affected by the proposed rule.
Compliance forecast...................  Uncertain......................  The forecast probabilities are based on
                                                                          historical full-scale compliance
                                                                          actions. Site-specific water quality
                                                                          conditions, changes in technology, and
                                                                          changes in market conditions can
                                                                          result in future technology selections
                                                                          that differ from the compliance
                                                                          forecast.
TOC concentration.....................  Uncertain......................  The randomly assigned values from the
                                                                          two national distributions are based
                                                                          on a limited dataset. Actual TOC
                                                                          concentrations at systems affected by
                                                                          the proposed rule can be higher or
                                                                          lower than the assigned values.
Insufficient UCMR 3 data for PFBS and   Underestimate..................  The HI in the proposed option would
 PFNA and no UCMR 3 data for HFPO-DA                                      regulate PFBS, PFNA, and HFPO-DA in
 were available to incorporate into                                       addition to the modeled PFAS. In
 the Bayesian hierarchical occurrence                                     instances when concentrations of PFBS,
 model.                                                                   PFNA, and/or HFPO-DA are high enough
                                                                          to cause a HI exceedance, the modeled
                                                                          costs may be underestimated. If these
                                                                          PFAS occur in isolation at levels that
                                                                          affect treatment decisions, or if they
                                                                          occur in sufficient concentration to
                                                                          result in an exceedance when the
                                                                          concentration of PFHxS alone would be
                                                                          below the HI, then costs would be
                                                                          underestimated. Note that EPA has
                                                                          conducted an analysis of the potential
                                                                          changes in system level treatment cost
                                                                          associated with the occurrence of
                                                                          PFBS, PFNA, and HFPO-DA using a model
                                                                          system approach which is discussed in
                                                                          detail in Chapter 5 and Appendix N of
                                                                          the Economic Analysis (USEPA, 2023j;
                                                                          USEPA, 2023i).
POU not included in compliance          Overestimate...................  If POU devices can be certified to meet
 forecast.                                                                concentrations that satisfy the
                                                                          proposed rule, then small systems may
                                                                          be able to reduce costs by using a POU
                                                                          compliance option instead of
                                                                          centralized treatment or source water
                                                                          changes.
Process wastes not classified as        Underestimate..................  The national cost analysis reflects the
 hazardous.                                                               assumption that PFAS-contaminated
                                                                          wastes are not considered hazardous
                                                                          wastes. As a general matter, EPA notes
                                                                          that such wastes are not currently
                                                                          regulated under Federal law as a
                                                                          hazardous waste. To address
                                                                          stakeholder concerns, including those
                                                                          raised during the SBREFA process, EPA
                                                                          conducted a sensitivity analysis with
                                                                          an assumption of hazardous waste
                                                                          disposal for illustrative purposes
                                                                          only. As part of this analysis, EPA
                                                                          generated a second full set of unit
                                                                          cost curves that are identical to the
                                                                          curves used for the national cost
                                                                          analysis with the exception that spent
                                                                          GAC and spent IX resin are considered
                                                                          hazardous. EPA acknowledges that if
                                                                          Federal authorities later determine
                                                                          that PFAS-contaminated wastes require
                                                                          handling as hazardous wastes, the
                                                                          residuals management costs in the WBS
                                                                          treatment cost models are expected to
                                                                          be higher. See Appendix N of the
                                                                          Economic Analysis (USEPA, 2023j;
                                                                          USEPA, 2023i) for a sensitivity
                                                                          analysis describing the potential
                                                                          increase in costs associated with
                                                                          hazardous waste disposal at 100% of
                                                                          systems treating for PFAS. The costs
                                                                          estimated in Appendix N are consistent
                                                                          with EPA OLEM's ``Interim Guidance on
                                                                          the Destruction and Disposal of
                                                                          Perfluoroalkyl and Polyfluoroalkyl
                                                                          Substances and Materials Containing
                                                                          Perfluoroalkyl and Polyfluoroalkyl
                                                                          Substances.'' \1\
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ EPA Office of Land and Emergency Management's Interim Guidance on the Destruction and Disposal of
  Perfluoroalkyl and Polyfluoroalkyl Substances and Materials Containing Perfluoroalkyl and Polyfluoroalkyl
  Substances can be found at https://www.epa.gov/system/files/documents/2021-11/epa-hq-olem-2020-0527-0002_content.pdf.

D. Method for Estimating Benefits

    EPA's quantification of health benefits resulting from reduced PFAS
exposure in drinking water was driven by PFAS occurrence estimates,
pharmacokinetic (PK) model availability, information on exposure-
response relationships, and available information to monetize avoided
cases of illness. In the Economic Analysis, EPA either quantitatively
assesses or qualitatively discusses health endpoints associated with
exposure to PFAS. EPA assesses potential benefits quantitatively if
evidence of exposure and health effects is likely, it is possible to
link the outcome to risk of a health effect, and there is no overlap in
effect with another quantified endpoint in the same outcome group.
Particularly, the most consistent epidemiological associations with
PFOA and PFOS include decreased immune system response, decreased
birthweight, increased serum lipids, and increased liver enzymes
(particularly ALT). The available evidence indicates effects across
immune, developmental, cardiovascular, and hepatic organ systems at the
same or approximately the same level of exposure.
    Table 42 presents an overview of the categories of health benefits
expected to result from the implementation of treatment that reduces
PFAS levels in drinking water. Of the PFAS compounds included in the
proposed rule, EPA quantifies some of the adverse health effects
associated with PFOA and PFOS. EPA also quantifies one adverse health
effect of PFNA in a sensitivity analysis only. These compounds have
likely evidence linking exposure to a particular health endpoint and
have reliable PK models connecting the compound to PFAS blood serum. PK
models describe the distribution of chemicals in the body and
pharmacodynamic relation between blood concentration and clinical
effects. Benefits from avoided adverse health effects of HFPO-DA, PFHxS
and PFBS are discussed qualitatively in this section.
    As Table 42 demonstrates, only a subset of the avoided morbidity
and mortality stemming from reduced PFAS levels in drinking water can
be quantified and monetized. The monetized benefits evaluated in the
Economic Analysis for the proposed rule include changes in human health
risks associated with CVD and infant

birth weight from reduced exposure to PFOA and PFOS in drinking water
and RCC from reduced exposure to PFOA. EPA also quantified benefits
from reducing bladder cancer risk due to the co-removal of non-PFAS
pollutants via the installation of drinking water treatment, discussed
in greater detail in USEPA (2023j).
    EPA was not able to quantify or monetize other benefits, including
those related to other reported health effects including immune, liver,
endocrine, metabolic, reproductive, musculoskeletal, other cancers. EPA
discusses these benefits qualitatively in more detail below, as well as
in Section 6.2 of USEPA (2023j).

                                      Table 42--Overview of Health Benefits Categories Considered in the Analysis of Changes in PFAS Drinking Water Levels
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                           Health outcome                                                          PFAS Compound \1\ \2\ \3\                                       Benefits analysis \4\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Discussed           Discussed
                Category                           Endpoint               PFOA          PFOS          PFNA          PFHxS         PFBS         HFPO-DA      quantitatively       qualitatively
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Lipids..................................  Total cholesterol.........            X             X         \e\ X                                                             X
                                          High-density lipoprotein          \5\ X         \5\ X                                                                           X
                                           cholesterol (HDLC).
                                          Low-density lipoprotein               X             X         \5\ X                                                                                X
                                           cholesterol (LDLC).
CVD.....................................  Blood pressure............                          X                                                                           X
Developmental...........................  Birth weight..............            X             X             X         \5\ X         \5\                   X
                                          Small for gestational age             X                       \5\ X             X                                                           X
                                           (SGA), non-birth weight
                                           developmental.
Endocrine...............................  Thyroid hormone disruption                                                                                X
Hepatic.................................  ALT.......................            X             X         \5\ X             X                                                           X
Immune..................................  Antibody response                     X             X         \5\ X             X                                                           X
                                           (tetanus, diphtheria).
Metabolic...............................  Leptin....................            X                                                                                X
Renal...................................  Organ weight..............                                                                                X
Musculoskeletal.........................  Osteoarthritis, bone                  X                       \5\ X                                                                                X
                                           mineral density.
Hematologic.............................  Vitamin D levels,                                                                                X
                                           hemoglobin levels,
                                           albumin levels.
Cancer..................................  RCC.......................            X                                                                                X
                                          Testicular................            X                                                                                X
                                          Other.....................                                                                        \5\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\1\ Fields marked with ``X'' indicate the PFAS compound for which there is evidence of an association with a given health outcome in epidemiological studies.
\2\ Fields marked with ``'' indicate the PFAS compound for which there is evidence of an association with a given health outcome only in toxicological studies.
\3\ Note that only PFOA and PFOS effects were modeled in the assessment of benefits under the proposed rule. PFNA was modeled only in sensitivity analyses of birth weight benefits (See
  Economic Analysis Appendix K in USEPA (2023i)).
\4\ Outcomes with likely evidence of an association between a PFAS compound and a health outcome are assessed quantitatively unless (1) there is an overlap within the same outcome group (e.g.,
  LDLC overlaps with total cholesterol, and SGA overlaps with low birth weight), or (2) it is not possible to link the outcome to the risk of the health effect (e.g., evidence is inconclusive
  regarding the relationship between PFOS exposure and leptin levels and associated health outcomes). Such health outcomes are discussed qualitatively.
\5\ Evidence of the relationship between the PFAS compound and the health outcome is not conclusive. Note that EPA sought comments from the EPA SAB on the CVD exposure-response approach
  (USEPA, 2023j). The SAB recommended that EPA evaluate how the inclusion of HDLC effects would influence results. EPA evaluated the inclusion of HDLC effects in a sensitivity analysis,
  described in Appendix K.

    EPA developed PK models to evaluate blood serum PFAS levels in
adults resulting from exposure to PFAS via drinking water. To date, EPA
has developed PK models for PFOA and PFOS. EPA used baseline and
regulatory alternative PFOA/PFOS drinking water concentrations as
inputs to its PK model to estimate blood serum PFOA/PFOS concentrations
for adult males and females. For further detail on the PK model and its
application in EPA's benefits analysis, please see EPA's Proposed MCLG
documents (USEPA, 2023b; USEPA, 2023c) and Section 6.3 of USEPA
(2023j).
1. Quantified Developmental Effects
    Research indicates that exposure to PFOA and PFOS is associated
with developmental effects, including infant birth weight (Verner et
al., 2015; USEPA, 2016e; USEPA, 2016f; USEPA, 2023b; USEPA, 2023c;
Negri et al., 2017; ATSDR, 2021; Waterfield et al., 2020). The route
through which the embryo and fetus are exposed prenatally to PFOA and
PFOS is maternal blood serum via the placenta. Most studies of the
association between maternal serum PFOA/PFOS and birth weight report
negative relationships (Verner et al., 2015; Negri et al., 2017;
Dzierlenga et al., 2020). EPA's PK model assumes that mothers were
exposed to PFOA/PFOS from birth to the year in which pregnancy
occurred.
    EPA quantified and valued changes in birth weight-related risks
associated

with reductions in exposure to PFOA and PFOS in drinking water. Entry
point-specific time series of the differences between serum PFOA/PFOS
concentrations under baseline and regulatory alternatives are inputs
into this analysis. For each entry point, evaluation of the changes in
birth weight impacts involves the following key steps:
    1. Estimating the changes in birth weight based on modeled changes
in serum PFOA/PFOS levels and exposure-response functions for the
effect of serum PFOA/PFOS on birth weight;
    2. Estimating the difference in infant mortality probability
between the baseline and regulatory alternatives based on changes in
birth weight under the regulatory alternatives and the association
between birth weight and mortality;
    3. Identifying the infant population affected by reduced exposure
to PFOA/PFOS in drinking water under the regulatory alternatives;
    4. Estimating the changes in the expected number of infant deaths
under the regulatory alternatives based on the difference in infant
mortality rates and the population of surviving infants affected by
increases in birth weight due to reduced PFOA/PFOS exposure; and
    5. Estimating the economic value of reducing infant mortality based
on the Value of a Statistical Life and infant morbidity based on
reductions in medical costs associated with changes in birth weight for
the surviving infants based on the cost of illness.
    EPA also considered the potential benefits from reduced exposure to
PFNA that may be realized as a direct result of the proposed rule. The
Agency explored the birth weight impacts of PFNA in a sensitivity
analysis, using a unit PFNA reduction scenario (i.e., 1.0 ppt change)
and Lu and Bartell (2020) to estimate PFNA blood serum levels resulting
from PFNA exposures in drinking water. To estimate blood serum PFNA
based on its drinking water concentration, EPA used a first-order
single-compartment model whose behavior was previously demonstrated to
be consistent with PFOA PKs in humans (Bartell et al., 2010). In
addition to the PFOA-birth weight and PFOS-birth weight effects
analyzed in the Economic Analysis, EPA examined the effect of inclusion
of PFNA-birth weight effects using estimates from two studies (Lenters
et al., 2016; Valvi et al., 2017). EPA found that inclusion of a 1.0
ppt PFNA reduction could increase annualized birth weight benefits 5.4-
7.7-fold, relative to the scenario that quantifies a 1.0 ppt reduction
in PFOA and a 1.0 ppt reduction in PFOS only. The range of estimated
PFNA-related increases in benefits is driven by the exposure-response,
with smaller estimates produced using the slope factors from Lenters et
al. (2016), followed by Valvi et al. (2017). EPA notes that the PFNA
slope factor estimates are orders of magnitude larger than the slope
factor estimates used to evaluate the impacts of PFOA/PFOS reductions.
EPA also notes that the PFNA slope factor estimates are not precise,
with 95% CIs covering wide ranges that include zero (i.e., serum PFNA
slope factor estimates are not statistically significant at 5% level).
Caution should be exercised in making judgements about the potential
magnitude of change in the national benefits estimates based on the
results of these sensitivity analyses, although conclusions about the
directionality of these effects can be inferred. EPA did not include
PFNA effects in the national benefits estimates for the proposed
rulemaking because of limitations associated with the UCMR 3 PFNA
occurrence data and the slope factor estimates are less precise. For
more information, see Appendix K of USEPA (2023j).
    To estimate changes in birth weight resulting from reduced exposure
to PFOA and PFOS under the regulatory alternatives, EPA relied on the
estimated time series of changes in serum PFOA/PFOS concentrations
specific to women of childbearing age and serum-birth weight exposure-
response functions provided in recently published meta-analyses. For
more detail on the evaluation of the studies used in these meta-
analyses, please see EPA's Proposed Maximum Contaminant Level Goal for
PFOA and PFOS in Drinking Water (USEPA, 2023b; USEPA, 2023c) and
Section 6.4 of USEPA (2023j).
    Changes in serum PFOA and PFOS concentrations are calculated for
each PWS entry point during each year in the analysis period. EPA
assumes that, given long half-lives of PFOS and PFOA, any one-time
measurement during or near pregnancy is reflective of a critical window
and not subject to considerable error. The mean change in birth weight
per increment in long-term PFOA and PFOS exposure is calculated by
multiplying each annual change in PFOA and PFOS serum concentration
(ng/mL serum) by the PFOA and PFOS serum-birth weight exposure-response
slope factors (g birth weight per ng/mL serum) provided in Table 43,
respectively. The mean annual change in birth weight attributable to
changes in both PFOA and PFOS exposure is the sum of the annual PFOA-
and PFOS-birth weight change estimates. Additional detail on the
derivation of the exposure-response functions can be found in Appendix
D in USEPA (2023i). Appendix K in USEPA (2023i) presents an analysis of
birth weight risk reduction considering slope factors specific to the
first trimester.

        Table 43--Serum Exposure-Birth Weight Response Estimates
------------------------------------------------------------------------
                    Compound                     g/ng/mL serum  (95% CI)
------------------------------------------------------------------------
PFOA \1\.......................................      -10.5 (-16.7, -4.4)
PFOS \2\.......................................        -3.0 (-4.9, -1.1)
------------------------------------------------------------------------
Notes:
\1\ The serum-birth weight slope factor for PFOA is based on the main
  random effects estimate from Negri et al. (2017); Steenland et al.
  (2018).
\2b\ The serum-birth weight slope factor for PFOS is based on an EPA
  reanalysis of Dzierlenga et al. (2020).

    EPA places a cap on estimated birth weight changes in excess of 200
g, assuming that such changes in birth weight are unreasonable even as
a result of large changes in PFOA/PFOS serum concentrations. This cap
is based on existing studies that found that changes to environmental
exposures result in relatively modest birth weight changes (Windham and
Fenster, 2008; Klein and Lynch, 2018; Kamai et al., 2019).
    Low birth weight is linked to a number of health effects that may
be a source of economic burden to society in the form of medical costs,
infant mortality, parental and caregiver costs, labor market
productivity loss, and education costs (Chaikind and Corman, 1991;
Behrman and Butler, 2007; Behrman and Rosenzweig, 2004; Joyce et al.,
2012; Kowlessar et al., 2013; Colaizy et al., 2016; Nicoletti et al.,
2018; Klein and Lynch, 2018). Recent literature also linked low birth
weight to educational attainment and required remediation to improve
students' outcomes, childhood disability, and future earnings
(Jelenkovic et al., 2018; Temple et al., 2010; Elder et al., 2020;
Hines et al., 2020 Chatterji et al., 2014; Dobson et al., 2018).
    EPA's analysis focuses on two categories of birth weight impacts
that are amenable to monetization associated with incremental changes
in birth weight: (1) medical costs associated with changes in infant
birth weight and (2) the value of avoiding infant mortality at various
birth weights. The birth weight literature related to other sources of
economic burden to society (e.g., parental and caregiver costs and
productivity losses) is limited in geographic coverage, population
size, and range of birth weights evaluated

and therefore cannot be used in the economic analysis of birth weight
effects from exposure to PFOA/PFOS in drinking water (ICF, 2021).
    Two studies showed statistically significant relationships between
incremental changes in birth weight and infant mortality: Almond et al.
(2005) and Ma and Finch (2010). Ma and Finch (2010) used 2001 National
Center for Health Statistics (NCHS) linked birth/infant death data for
singleton and multiple birth infants among subpopulations defined by
sex and race/ethnicity to estimate a regression model assessing the
associations between 14 key birth outcome measures, including birth
weight, and infant mortality. They found notable variation in the
relationship between birth weight and mortality across race/ethnicity
subpopulations, with odds ratios for best-fit birth weight-mortality
models ranging from 0.8-1 (per 100 g birth weight change). Almond et
al. (2005) used 1989-1991 NCHS linked birth/infant death data for
multiple birth infants to analyze relationships between birth weight
and infant mortality within birth weight increment ranges. For their
preferred model, they reported coefficients in deaths per 1,000 births
per 1 g increase in birth weight that range from -0.420 to -0.002.
However, the data used in these studies (Almond et al., 2005 and Ma,
2010) are outdated (1989-1991 and 2001, respectively). Given the
significant decline in infant mortality over the last 30 years (ICF,
2020) and other maternal and birth characteristics that are likely to
influence infant mortality (e.g., average maternal age and rates of
maternal smoking), the birth weight-mortality relationship estimates
from Almond et al. (2005) and Ma and Fitch (2010) are likely to
overestimate the benefits of birth weight changes.
    Considering the discernible changes in infant mortality over the
last 30 years, EPA developed a regression analysis to estimate the
relationship between birth weight and infant mortality using the most
recently available Period/Cohort Linked Birth-Infant Death Data Files
published by NCHS from the 2017 period/2016 cohort and the 2018 period/
2017 cohort (CDC, 2017, 2018). EPA selected variables of interest for
the regression analysis, including maternal demographic and
socioeconomic characteristics, maternal risk and risk mitigation
factors (e.g., number of prenatal care visits, smoker status), and
infant birth characteristics. EPA included several variables used in Ma
and Fitch (2010) (maternal age, maternal education, marital status, and
others) as well as additional variables to augment the set of
covariates included in the analyses. In addition, EPA developed
separate models for different race/ethnicity categories (non-Hispanic
Black, non-Hispanic White, and Hispanic) and interacted birth weight
with categories of gestational age, similar to Ma and Finch (2010).
Appendix E to USEPA (2023i) provides details on model development and
regression results.
    Table 44 presents the resulting odds ratios and marginal effects
(in terms of deaths per 1,000 births for every 1 g increase in birth
weight) estimated for changes in birth weight among different
gestational age categories in the mortality regression models for non-
Hispanic Black, non-Hispanic White, and Hispanic race/ethnicity
subpopulations. Marginal effects for birth weight among gestational age
categories vary across different race/ethnicity subpopulations. The
marginal effects for birth weight among different gestational age
categories are higher in the non-Hispanic Black model than in the non-
Hispanic White and Hispanic models, particularly for extremely and very
preterm infants, indicating that low birth weight increases the
probability of mortality within the first year more so among non-
Hispanic Black infants than among non-Hispanic White and Hispanic
infants.
    EPA relies on odds ratios estimated using the birth weight-
mortality regression model to assess mortality outcomes of reduced
exposures to PFOA/PFOS in drinking water under the regulatory
alternatives. To obtain odds ratios specific to each race/ethnicity and
100 g birth weight increment considered in the birth weight benefits
model,\6\ EPA averaged the estimated odds ratios for 1 g increase in
birth weight over the gestational age categories using the number of
infants (both singleton and multiple birth) that fall into each
gestational age category as weights. Separate gestational age category
weights were computed for each 100 g birth weight increment and race/
ethnicity subpopulation within the 2017 period/2016 cohort and 2018
period/2017 cohort Linked Birth-Infant Death Data Files. The weighted
birth weight odds ratios are then used in conjunction with the
estimated change in birth weight and baseline infant mortality rates to
determine the probability of infant death under the regulatory
alternatives, as described further in Section 6.4 of USEPA (2023j).
---------------------------------------------------------------------------

    \6\ The birth weight risk reduction model evaluates changes in
birth weight in response to PFOA/PFOS drinking water level
reductions for infants who fall into 100 g birth weight increments
(e.g., birth weight 0-99 g, 100-199 g, 200-299 g. . . 8,000-8,099 g,
8,100-8,165 g).

  Table 44--Race/Ethnicity and Gestational Age-Specific Birth Weight Marginal Effects and Odds Ratios From the
                                         Mortality Regression Models \1\
----------------------------------------------------------------------------------------------------------------
                                           Gestational age        Marginal effect per
                 Race                        category \2\        1,000 births (95% CI)     Odds ratio (95% CI)
----------------------------------------------------------------------------------------------------------------
Non-Hispanic Black...................  Extremely Preterm......  -0.20400 (-0.21910, -    0.99817 (0.99802,
                                                                 0.18890).                0.99832)
                                       Very Preterm...........  -0.04580 (-0.04820, -    0.99816 (0.99804,
                                                                 0.04340).                0.99827)
                                       Moderately Preterm.....  -0.01030 (-0.01080, -    0.99852 (0.99846,
                                                                 0.009850).               0.99857)
                                       Term...................  -0.00453 (-0.00472, -    0.99856 (0.99851,
                                                                 0.00434).                0.9986)
Non-Hispanic White...................  Extremely Preterm......  -0.12160 (-0.13080, -    0.99866 (0.99855,
                                                                 0.11240).                0.99878)
                                       Very Preterm...........  -0.03290 (-0.03430, -    0.9985 (0.99842,
                                                                 0.03140).                0.99858)
                                       Moderately Preterm.....  -0.00677 (-0.00702, -    0.99867 (0.99863,
                                                                 0.00652).                0.99872)
                                       Term...................  -0.00228 (-0.00236, -    0.99865 (0.99861,
                                                                 0.00221).                0.99868)

Hispanic.............................  Extremely Preterm......  -0.15260 (-0.16770, -    0.99835 (0.99817,
                                                                 0.13750).                0.99853)
                                       Very Preterm...........  -0.03290 (-0.03510, -    0.99846 (0.99835,
                                                                 0.03070).                0.99858)
                                       Moderately Preterm.....  -0.00626 (-0.00659, -    0.99856 (0.99849,
                                                                 0.00592).                0.99862)
                                       Term...................  -0.00219 (-0.00229, -    0.99849 (0.99844,
                                                                 0.00208).                0.99855)
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Data based on the 2016/17 and 2017/18 CDC Period Cohort Linked Birth-Infant Death Data Files obtained from
  NCHS/National Vital Statistics System (NVSS). Marginal effects and odds ratios are estimated using a
  regression model that also includes covariates representative of infant birth characteristics in addition to
  birth weight, maternal demographic characteristics, and maternal risk factors. All effects were statistically
  significant at the 5% level. Additional details are included in Appendix E to the Economic Analysis.
\2\ Gestational age categories defined as extremely preterm (<=28 weeks), very preterm (>28 weeks and <=32
  weeks), moderately preterm (>32 weeks and <=37 weeks), and term (>37 weeks).

    EPA weighted the race/ethnicity-specific odds ratios in Table 44 by
the proportions of the infant populations who fell into each
gestational age within a 100 g birth weight increment, based on the
2016/17 and 2017/18 period cohort data, to obtain a weighted odds ratio
estimate for each modeled race/ethnicity subpopulation and 100 g birth
weight increment.
    Based on reduced serum PFOA/PFOS exposures under the regulatory
alternatives and the estimated relationship between birth weight and
infant mortality, EPA estimates the subsequent change in birth weight
for those infants affected by decreases in PFOA/PFOS and changes in the
number of infant deaths. EPA evaluated these changes at each PWS entry
point affected by the regulatory alternatives and the calculations are
performed for each race/ethnicity group, 100 g birth weight category,
and year of the analysis. Additional detail on the calculations EPA
used to estimate changes in birth weight, the affected population size,
and infant deaths avoided, and the number of surviving infants is
provided in Chapter 6 of USEPA (2023j).
    EPA used the Value of a Statistical Life to estimate the benefits
of reducing infant mortality and the cost of illness to estimate the
economic value of increasing birth weight in the population of
surviving infants born to mothers exposed to PFOA and PFOS in drinking
water. EPA's approach to monetizing benefits associated with
incremental increases in birth weight resulting from reductions in
drinking water PFOA/PFOS levels relies on avoided medical costs
associated with various ranges of birth weight. Although the economic
burden of treating infants at various birth weights also includes non-
medical costs, very few studies to date have quantified such costs
(Klein and Lynch, 2018; ICF, 2021). EPA selected the medical cost
function from Klein and Lynch (2018) to monetize benefits associated
with the estimated changes in infant birth weight resulting from
reduced maternal exposure to PFOA/PFOS.\7\
---------------------------------------------------------------------------

    \7\ The Klein and Lynch (2018) report was externally peer
reviewed by three experts with qualifications in economics and
public health sciences. EPA's charge questions to the peer reviewers
sought input on the methodology for developing medical cost
estimates associated with changes in birth weight. The Agency's
charge questions and peer reviewer responses are available in the
docket.
---------------------------------------------------------------------------

    Using the incremental cost changes from Klein and Lynch (2018), EPA
calculates the change in medical costs resulting from changes in birth
weight among infants in the affected population who survived the first
year following birth, provided in Table 45.

                           Table 45--Simulated Cost Changes for Birth Weight Increases
                                                     [$2021]
----------------------------------------------------------------------------------------------------------------
                                                                      Simulated cost changes for birth weight
                                                                      increases, dollars per gram ($2021) \3\
                      Birth weight \1\ \2\                       -----------------------------------------------
                                                                   +0.04 lb (+18   +0.11 lb (+50  +0.22 lb (+100
                                                                        g)              g)              g)
----------------------------------------------------------------------------------------------------------------
2 lb (907 g)....................................................        -$126.53        -$112.87        -$109.39
2.5 lb (1,134 g)................................................         -$94.88         -$84.64         -$82.03
3 lb (1,361 g)..................................................         -$71.15         -$63.47         -$61.51
3.3 lb (1,497 g)................................................         -$59.86         -$53.40         -$51.75
4 lb (1,814 g)..................................................         -$40.00         -$35.69         -$34.59
4.5 lb (2,041 g)................................................         -$30.00         -$26.76         -$25.93
5 lb (2,268 g)..................................................         -$22.49         -$20.07         -$19.45
5.5 lb (2,495 g)................................................          -$0.93          -$0.84          -$0.84
6 lb (2,722 g)..................................................          -$0.91          -$0.83          -$0.83
7 lb (3,175 g)..................................................          -$0.88          -$0.80          -$0.80
8 lb (3,629 g)..................................................          -$0.85          -$0.77          -$0.77
9 lb (4,082 g)..................................................           $3.15           $2.87           $2.89
10 lb (4,536 g).................................................           $3.54           $3.23           $3.26
----------------------------------------------------------------------------------------------------------------
Notes:

\1\ Values for birth weight have been converted from lb to g.
\2\ Note that simulated medical costs increase, rather than decrease, in response to increased birth weight
  changes among high birth weight infants (those greater than 8 lb). Among high birth weight infants, there is a
  higher risk of birth trauma, metabolic issues, and other health problems (Klein and Lynch, 2018).
\3\ Values scaled from $2010 to $2021 using the medical care CPI (Bureau of Labor Statistics, 2021).

    Tables 46 to 49 provide the health effects avoided and valuation
associated with birth weight impacts. EPA estimated that, over the
evaluation period, the proposed rule will result in an average annual
benefit from avoided reductions in birth weight from $139 million
($2021, 7% discount rate) to $178 million ($2021, 3% discount rate).

                            Table 46--National Birth Weight Benefits, Proposed Option
                                  [PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0]
                                                 [Million $2021]
----------------------------------------------------------------------------------------------------------------
                                                  3% Discount rate                     7% Discount rate
                                       -------------------------------------------------------------------------
           Benefits category                5th                     95th         5th                     95th
                                         Percentile   Expected   Percentile   Percentile   Expected   Percentile
                                            \1\       benefits      \1\          \1\       benefits      \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of         114.2      209.3        329.7        114.2      209.3        329.7
 grams)...............................
Number of Birth Weight-Related Deaths         676.8    1,232.7      1,941.0        676.8    1,232.7      1,941.0
 Avoided..............................
Total Annualized Birth Weight Benefits       $97.36    $177.66      $279.49       $74.62    $139.01      $219.43
 (Million $2021) \2\..................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
  XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
  benefits would have on the estimated monetized total annualized benefits in this table.

                               Table 47--National Birth Weight Benefits, Option 1a
                                         [PFOA and PFOS MCLs of 4.0 ppt]
                                                 [Million $2021]
----------------------------------------------------------------------------------------------------------------
                                                  3% Discount rate                     7% Discount rate
                                       -------------------------------------------------------------------------
           Benefits category                5th                     95th         5th                     95th
                                         Percentile   Expected   Percentile   Percentile   Expected   Percentile
                                            \1\       benefits      \1\          \1\       benefits      \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of         111.7      206.3        326.9        111.7      206.3        326.9
 grams)...............................