[Federal Register Volume 69, Number 67 (Wednesday, April 7, 2004)]
[Proposed Rules]
[Pages 18327-18338]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-7775]
-----------------------------------------------------------------------
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 63
[OAR-2003-0189; FRL-7643-8]
RIN 2060-AK73
National Emission Standards for Hazardous Air Pollutants for
Stationary Combustion Turbines
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: The EPA is proposing to amend the list of categories of
sources that was developed pursuant to section 112(c)(1) of the Clean
Air Act (CAA) by deleting four subcategories from the Stationary
Combustion Turbines source category. Final maximum achievable control
technology (MACT) standards creating the following subcategories were
published on March 5, 2004: lean premix gas-fired stationary combustion
turbines, diffusion flame gas-fired stationary combustion turbines,
emergency stationary combustion turbines, and stationary combustion
turbines located on the North Slope of Alaska. This action is being
taken in part to respond to a petition submitted by the Gas Turbine
Association (GTA) and in part upon the EPA Administrator's own motion.
Petitions to remove a source category from the source category list are
permitted under section 112(c)(9) of the CAA. The proposed rule is
based on EPA's evaluation of available information concerning the
potential hazards from exposure to hazardous air pollutants (HAP)
emitted from the four subcategories and includes a detailed rationale
for removing the subcategories from the source category list. We
request comment on the proposed rule.
Although the proposed rule would delete certain subcategories from
the Stationary Combustion Turbines source category, the MACT standards
for the subcategories will take effect upon publication of the
standards. Because the MACT standards require immediate compliance by
new sources, some sources in the subcategories which we are proposing
to delist may need to make immediate expenditures on emission controls
which will not be required if we adopt a final rule to delete the
subcategories. In view of our initial determination that the statutory
criteria for delisting have been met for the subcategories, we consider
it inappropriate and contrary to statutory intent to mandate such
expenditures until after a final determination has been made whether or
not the subcategories should be delisted. Accordingly, we are
publishing elsewhere in this Federal Register a proposal to stay the
effectiveness of the MACT standards for new sources in the
subcategories during the pendency of the rule to delete the
subcategories.
DATES: Comments. Written comments on the proposed rule must be received
by June 7, 2004.
Public Hearing. A public hearing regarding the proposed rule will
be held if requests to speak are received by the EPA on or before April
22, 2004. If requested, a public hearing will be held on May 5, 2004.
ADDRESSES: Comments. Comments may be submitted electronically, by mail,
or through hand delivery/courier. Electronic comments may be submitted
on-line at http://www.epa.gov/edocket/. Written comments sent by U.S.
mail should be submitted (in duplicate if possible) to: Air and
Radiation Docket and Information Center (Mail Code 6102T), Attention
Docket ID Number OAR-2003-0189, Room B108, U.S. EPA, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460. Written comments delivered in person
or by courier should be submitted (in duplicate if possible) to: Air
and Radiation Docket and Information Center (Mail Code 6102T),
Attention Docket ID Number OAR-2003-0189, Room B102, U.S. EPA, 1301
Constitution Avenue, NW., Washington, DC 20460. The EPA requests a
separate copy also be sent to the contact person listed below (see FOR
FURTHER INFORMATION CONTACT).
Public Hearing. If a public hearing is requested by April 22, 2004
the public hearing will be held at the EPA facility complex, T.W.
Alexander Drive, Research Triangle Park, NC May 5, 2004. Persons
interested in presenting oral testimony should contact Ms. Kelly A.
Rimer, Risk and Exposure Assessment Group, Emission Standards Division
(C404-01), U.S. EPA, Research Triangle Park, North Carolina 27711,
telephone number (919) 541-2962. Persons interested in attending the
public hearing should also contact Ms. Rimer to verify the time of the
hearing.
FOR FURTHER INFORMATION CONTACT: Ms. Kelly A. Rimer, Risk and Exposure
Assessment Group, Emission Standards Division (C404-01), U.S. EPA,
Research Triangle Park, NC 27711, telephone number (919) 541-2962,
electronic mail address [email protected].
SUPPLEMENTARY INFORMATION: Regulated Entities. Categories and entities
potentially regulated by this action include:
----------------------------------------------------------------------------------------------------------------
Category SIC NAICS Examples of regulated entities
----------------------------------------------------------------------------------------------------------------
Any industry using a combustion turbine as 4911 2211 Electric power generation,
defined in the regulation. transmission, or stationary
distribution.
4922 486210 Natural gas transmission.
1311 211111 Crude petroleum and natural gas
production.
1321 211112 Natural gas liquids producers.
4931 221 Electric and other services combined.
----------------------------------------------------------------------------------------------------------------
[[Page 18328]]
This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. If you have any questions regarding the applicability of this
action to a particular entity, consult the person listed in the
preceding FOR FURTHER INFORMATION CONTACT section.
Docket. The EPA has established an official public docket for this
action under Docket ID Number OAR-2003-0189. The official public docket
is the collection of materials that is available for public viewing at
the EPA Docket Center (Air Docket), EPA West, Room B-108, 1301
Constitution Avenue, NW., Washington, DC 20004. The Docket Center is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Reading Room is (202) 566-
1744, and the telephone number for the Air Docket is (202) 566-1742.
Electronic Access. An electronic version of the public docket is
available through EPA's electronic public docket and comment system,
EPA Dockets. You may use EPA Dockets at http://www.epa.gov/edocket/ to
submit or view public comments, access the index of the contents of the
official public docket, and access those documents in the public docket
that are available electronically. Once in the system, select
``search'' and key in the appropriate docket identification number.
Certain types of information will not be placed in the EPA dockets.
Information claimed as confidential business information (CBI) and
other information whose disclosure is restricted by statute, which is
not included in the official public docket, will not be available for
public viewing in EPA's electronic public docket. The EPA's policy is
that copyrighted material will not be placed in EPA's electronic public
docket but will be available only in printed, paper form in the
official public docket. Although not all docket materials may be
available electronically, you may still access any of the publicly
available docket materials through the EPA Docket Center.
For public commenters, it is important to note that EPA's policy is
that public comments, whether submitted electronically or in paper,
will be made available for public viewing in EPA's electronic public
docket as EPA receives them and without change unless the comment
contains copyrighted material, CBI, or other information whose
disclosure is restricted by statute. When EPA identifies a comment
containing copyrighted material, EPA will provide a reference to that
material in the version of the comment that is placed in EPA's
electronic public docket. The entire printed comment, including the
copyrighted material, will be available in the public docket.
Public comments submitted on computer disks that are mailed or
delivered to the docket will be transferred to EPA's electronic public
docket. Public comments that are mailed or delivered to the docket will
be scanned and placed in EPA's electronic public docket. Where
practical, physical objects will be photographed, and the photograph
will be placed in EPA's electronic public docket along with a brief
description written by the docket staff.
Comments. You may submit comments electronically, by mail, by
facsimile, or through hand delivery/courier. To ensure proper receipt
by EPA, identify the appropriate docket identification number in the
subject line on the first page of your comment. Please ensure that your
comments are submitted within the specified comment period. Comments
submitted after the close of the comment period will be marked
``late.'' The EPA is not required to consider these late comments.
Electronically. If you submit an electronic comment as prescribed
below, EPA recommends that you include your name, mailing address, and
an e-mail address or other contact information in the body of your
comment. Also include this contact information on the outside of any
disk or CD ROM you submit and in any cover letter accompanying the disk
or CD ROM. This ensures that you can be identified as the submitter of
the comment and allows EPA to contact you in case EPA cannot read your
comment due to technical difficulties or needs further information on
the substance of your comment. The EPA's policy is that EPA will not
edit your comment and any identifying or contact information provided
in the body of a comment will be included as part of the comment that
is placed in the official public docket and made available in EPA's
electronic public docket. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment.
Your use of EPA's electronic public docket to submit comments to
EPA electronically is EPA's preferred method for receiving comments. Go
directly to EPA Dockets at http://www.epa.gov/edocket, and follow the
online instructions for submitting comments. Once in the system, select
``search'' and key in Docket ID No. OAR-2003-0189. The system is an
``anonymous access'' system, which means EPA will not know your
identity, e-mail address, or other contact information unless you
provide it in the body of your comment.
Comments may be sent by electronic mail (e-mail) to [email protected], Attention Docket ID No. OAR-2003-0189. In contrast to
EPA's electronic public docket, EPA's e-mail system is not an
``anonymous access'' system. If you send an e-mail comment directly to
the docket without going through EPA's electronic public docket, EPA's
e-mail system automatically captures your e-mail address. E-mail
addresses that are automatically captured by EPA's e-mail system are
included as part of the comment that is placed in the official public
docket and made available in EPA's electronic public docket.
You may submit comments on a disk or CD ROM that you mail to the
mailing address identified in this document. These electronic
submissions will be accepted in WordPerfect or ASCII file format. Avoid
the use of special characters and any form of encryption.
By Mail. Send your comments (in duplicate, if possible) to: EPA
Docket Center (Air Docket), U.S. EPA West, (MD-6102T), Room B-108, 1200
Pennsylvania Avenue, NW., Washington, DC 20460, Attention Docket ID No.
OAR-2003-0189.
By Hand Delivery or Courier. Deliver your comments (in duplicate,
if possible) to: EPA Docket Center, Room B-108, U.S. EPA West, 1301
Constitution Avenue, NW., Washington, DC 20004, Attention Docket ID No.
OAR-2003-0189. Such deliveries are only accepted during the Docket
Center's normal hours of operation.
By Facsimile. Fax your comments to: (202) 566-1741, Docket ID No.
OAR-2003-0189.
CBI. Do not submit information that you consider to be CBI through
EPA's electronic public docket or by e-mail. Send or deliver
information identified as CBI only to the following address: Kelly
Rimer, c/o Roberto Morales, OAQPS Document Control Officer (C404-02),
U.S. EPA, Research Triangle Park, NC 27709, Attention Docket ID No.
OAR-2003-0189. You may claim information that you submit to EPA as CBI
by marking any part or all of that information as CBI (if you submit
CBI on disk or CD ROM, mark the outside of the disk or CD ROM as CBI
and then identify electronically within the disk or CD ROM the specific
information that is CBI). Information so marked will not be disclosed
except in accordance with procedures set forth in 40 CFR part 2.
In addition to one complete version of the comment that includes
any
[[Page 18329]]
information claimed as CBI, a copy of the comment that does not contain
the information claimed as CBI must be submitted for inclusion in the
public docket and EPA's electronic public docket. If you submit the
copy that does not contain CBI on disk or CD-ROM, mark the outside of
the disk or CD-ROM clearly that it does not contain CBI. Information
not marked as CBI will be included in the public docket and EPA's
electronic public docket without prior notice. If you have any
questions about CBI or the procedures for claiming CBI, please consult
the person identified in the FOR FURTHER INFORMATION CONTACT section.
Worldwide Web (WWW). In addition to being available in the docket,
an electronic copy of today's proposed rule will also be available on
the WWW through the Technology Transfer Network (TTN). Following the
Administrator's signature, a copy of the proposed rule will be placed
on the TTN's policy and guidance page for newly proposed or promulgated
rules at http://www.epa.gov/ttn/oarpg. The TTN provides information and
technology exchange in various areas of air pollution control. If more
information regarding the TTN is needed, call the TTN HELP line at
(919) 541-5384.
Outline. This preamble is organized as follows:
I. Background and Criteria for Delisting
II. Summary of Petitioner's Request and EPA's Initial Delisting
Determination
III. Description of the Four Stationary Combustion Turbine
Subcategories
IV. Analysis of Gas-Fired Subcategories
A. Analytical Approach
B. Planning and Scoping
C. Source Characterization
D. Emissions Characterization
E. Air Dispersion Modeling
F. Human Health Effects of Emitted HAP
G. Human Health Values Used
H. Human Health Risk Results--Air Pathway
I. Multipathway Considerations
J. Effects Due to Acute Exposure
K. Environmental Effects Evaluation
V. Analysis of the Emergency Turbine Subcategory
VI. Analysis of the North Slope Turbine Subcategory
VII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination with
Indian Tribal Governments
G. Executive Order 13045: Protection of Children from
Environmental Health Risks and Safety Risks
H. Executive Order 13211: Actions Concerning Regulations that
Significantly Affect Energy supply, Distribution, or Use
I. National Technology Transfer and Advancement Act
I. Background and Criteria for Delisting
Section 112 of the CAA contains a mandate for EPA to evaluate and
control emissions of HAP from industry sectors called source
categories. Section 112(b)(1) includes a list of 188 specific chemical
compounds and classes of compounds identified as HAP. Section 112(c)
requires the EPA to publish a list of all categories and subcategories
of sources of HAP which will be subject to regulation. Each category or
subcategory which includes major sources of HAP must be listed for
regulation. Under section 112(d), the CAA requires EPA to establish
national emission standards for major source categories based on MACT
for each category or subcategory which is included in the list.
The EPA published the initial source category list in the Federal
Register on July 16, 1992 (57 FR 31576); you can find the most recent
update to the source category list in the February 12, 2002 Federal
Register (67 FR 6521).
Section 112(c)(9) of the CAA provides for the deletion of a source
category from the list of source categories. A source category may be
deleted from the list under section 112(c)(9)(A) if the category no
longer satisfies the criteria for inclusion on the list because of the
deletion of one or more HAP from the HAP list pursuant to section
112(b)(3) or a source category may be deleted from the list under
section 112(c)(9)(B) if certain substantive criteria are satisfied. The
EPA construes these provisions to apply to each listed subcategory as
well. This construction is logical in the context of the general
regulatory scheme established by the statute and is the most reasonable
one because section 112(c)(9)(B)(ii) expressly refers to subcategories.
If EPA takes final action to delete a listed source category or
subcategory, this eliminates any requirement that MACT standards be
promulgated for the category or subcategory in question. If MACT
standards have already been promulgated, EPA will amend or rescind the
standards in question.
A proceeding to delete a listed category or subcategory under
section 112(c)(9)(B) of the CAA may be commenced either in response to
a petition or on the initiative of the EPA Administrator. A source
category delist petition is a formal request to the EPA from an
individual or group to remove a specific source category or subcategory
from the source category list. The Administrator must either grant or
deny a petition within 1 year after receiving a complete petition (64
FR 33453). To grant such a petition, or to commence a proceeding to
delete a category or subcategory on the Administrator's own motion, the
Administrator must make an initial determination that:
(1) In the case of HAP emitted by sources in the category or
subcategory that may result in cancer in humans, a determination that
no source in the category or subcategory emits such HAP in quantities
that may cause a lifetime risk of cancer greater than 1 in 1 million to
the individual in the population who is most exposed to emissions of
such HAP from the source;
(2) In the case of HAP that may result in adverse health effects in
humans other than cancer, a determination that emissions from no source
in the category or subcategory exceed a level which is adequate to
protect public health with an ample margin of safety; and
(3) In the case of HAP that may result in adverse environmental
effects, a determination that no adverse environmental effect will
result from emissions from any source in the category or subcategory.
If the Administrator decides to deny a petition, the Agency
publishes a written explanation of the basis for denial in the Federal
Register. A decision to deny a petition is final Agency action subject
to review. If the Administrator decides to grant a petition, the Agency
publishes a written explanation of the Administrator's decision, along
with a proposed rule to delete the affected source category or
subcategory. After affording an opportunity for notice and comment, the
Administrator will issue a final rule determining whether or not the
affected category or subcategory will be delisted. If the final rule
delists any affected source category or subcategory, the Administrator
will also take all necessary actions to revise the source category list
and to amend or to rescind affected MACT standards.
We do not interpret section 112(c)(9)(B) of the CAA to require
absolute certainty that a source category or subcategory will not cause
adverse effects on human health or the environment before it may be
deleted from the source category list. The use of the words ``may'' and
``adequate'' indicate that the Agency must weigh the potential
uncertainties and their likely significance. Uncertainties concerning
risks of adverse health or environmental effects may be mitigated if we
can determine that projected exposures are sufficiently low to provide
reasonable assurance that such adverse effects will
[[Page 18330]]
not occur. Similarly, uncertainties concerning the magnitude of
projected exposures may be mitigated if we can determine that the
levels which might cause adverse health or environmental effects are
sufficiently high to provide reasonable assurance that exposures will
not reach harmful levels.
II. Summary of Petitioner's Request and EPA's Initial Delisting
Determination
On August 28, 2002, the GTA submitted a petition requesting EPA to
create and then delete two subcategories from the Stationary Combustion
Turbines source category: lean premix stationary combustion turbines
firing natural gas as a primary fuel with limited oil backup
capability, and a low-risk subcategory of stationary combustion
turbines.
Upon receiving a source category or subcategory deletion petition,
EPA must first determine whether there is a match between the source
category or subcategory to which the petition applies and a listed
category or subcategory. When MACT standards have been promulgated for
the category in question, EPA will consult the definitions in those
standards to determine whether or not a petition refers to a listed
category or subcategory.
In this case, neither of the two subcategories to which the
petition refers existed at the time the petition was received, nor do
they coincide with the subcategories which we have recently adopted in
the final MACT standards for stationary combustion turbines. However,
based on the information and the arguments presented in the petition,
we decided to conduct our own analysis on the subcategories as they
were defined in the final MACT standards to determine whether any of
the subcategories meet the criteria of section 112(c)(9)(B) of the CAA.
In the analysis on which our initial determinations are based, we used
the data and analysis presented in the petition in those instances
where we felt it was relevant and technically appropriate to do so, and
we collected additional data and performed further analysis where those
in the petition were considered inadequate.
We construe the issuance of the proposed rule to constitute a
partial grant and a partial denial of the GTA petition. The lean premix
gas-fired turbines subcategory in the final MACT standards is similar
to one of the subcategories that the petitioner proposed: Namely, the
lean premix stationary combustion turbine firing natural gas as a
primary fuel with limited oil use. We have made an initial
determination that the substantive criteria for delisting are satisfied
for this subcategory. However, in the final MACT standards, we did not
create any subcategory coinciding with the low-risk subcategory
proposed by the petitioner. Therefore, we must deny that portion of the
petition. Also, we have made an initial determination that several
additional subcategories included in the final MACT standards satisfy
the substantive criteria for delisting. These additional subcategories
are: diffusion flame gas-fired stationary turbines, emergency
stationary combustion turbines, and stationary combustion turbines
located on the North Slope of Alaska.
III. Description of the Four Stationary Combustion Turbines
Subcategories
The final MACT standards (40 CFR 63.6175) define stationary
combustion turbines as:
All equipment including, but not limited to, the turbine, the
fuel, air, lubrication and exhaust gas systems, control systems
(except emissions control equipment), and any ancillary components
and sub-components comprising any simple cycle stationary combustion
turbine, any regenerative/recuperative cycle stationary combustion
turbine, or the combustion turbine portion of any stationary
combined cycle steam/electric generating system. Stationary means
that the combustion turbine is not self-propelled or intended to be
propelled while performing its function. A stationary combustion
turbine may, however, be mounted on a vehicle for portability or
transportability.
Currently, there are approximately 8,000 stationary combustion turbines
operating in the United States.
For the purposes of the MACT standards, stationary combustion
turbines have been divided into eight subcategories. Four of the
subcategories are the subject of the proposed delisting rule: (1)
Stationary lean premix combustion turbines when firing gas and when
firing oil at sites where all turbines fire oil no more than 1,000
hours annually (also referred to as ``lean premix gas-fired
turbines''); (2) stationary diffusion flame combustion turbines when
firing gas and when firing oil at sites where all turbines fire oil no
more than 1,000 hours annually (also referred to herein as ``diffusion
flame gas-fired turbines''); (3) emergency stationary combustion
turbines; and (4) stationary combustion turbines operated on the North
Slope of Alaska (defined as the area north of the Arctic Circle
(latitude 66.5[deg] North)).
The stationary combustion turbines MACT standards also define the
subcategories. The lean premix gas-fired turbines subcategory includes
those stationary combustion turbines that use lean premix technology
which was introduced in the 1990's and was developed to reduce nitrogen
oxide (NOX) emissions without the use of add-on controls. In
a lean premix combustor, the air and fuel are thoroughly mixed to form
a lean mixture for combustion. Mixing may occur before or in the
combustion chamber. Lean premix combustors emit lower levels of
NOX, carbon monoxide (CO), formaldehyde and other HAP than
diffusion flame combustion turbines.
Diffusion flame gas-fired turbines operate in a different manner
than lean premix units. In a diffusion flame combustor, the fuel and
air are injected at the combustor and are mixed only by diffusion prior
to ignition.
Emergency stationary combustion turbines are stationary combustion
turbines that operate in an emergency situation. Examples include
stationary combustion turbines used to produce power for critical
networks or equipment (including power supplied to portions of a
facility) when electric power from the local utility is interrupted, or
stationary combustion turbines used to pump water in the case of fire
or flood, etc. Emergency stationary combustion turbines do not include
stationary combustion turbines used as peaking units at electric
utilities or stationary combustion turbines at industrial facilities
that typically operate at low capacity factors. Emergency stationary
combustion turbines may be operated for the purpose of maintenance
checks and readiness testing, provided that the tests are required by
the manufacturer, the vendor, or the insurance company associated with
the turbine.
The subcategory stationary combustion turbines located on the North
Slope of Alaska refers to all stationary combustion turbines that are
located north of the Arctic Circle. They have been identified as a
subcategory due to operating limitations and uncertainties regarding
the application of controls to these units.
IV. Analysis of Gas-Fired Subcategories
A. Analytical Approach
In conducting the risk assessment for the four source
subcategories, EPA uses a tiered, iterative process recommended by the
National Research Council (NRC) of the National Academy of Sciences.
This process begins with the use of relatively inexpensive screening
techniques and moves to more resource-intensive levels of data-
gathering, model construction, and model application, as the particular
situation warrants (NRC, 1994). In applying this approach, EPA
[[Page 18331]]
typically conducts the first (and in some cases the only) iteration of
the risk assessment using limited amounts of data and simple, health-
protective assumptions. This results in risk estimates that we expect
will over-predict the actual risk. If the initial estimates of risk
exceed a level of concern, then successive refinements with regard to
data and models may be useful to more accurately characterize the
actual risk. If the initial estimates are below a level of concern,
then a more sophisticated analysis may not be necessary for decision-
making purposes.
The analysis discussed here represents an initial assessment based
on simple, health-protective assumptions. This screening approach has
not sought to modify the assumptions in a way that would yield exposure
estimates that would correspond to an actual individual in the
population who is most exposed. Instead, through the compounding of
health-protective assumptions, we feel this approach yields exposure
estimates that exceed exposures to the most exposed individuals in the
population.
B. Planning and Scoping
The first step in conducting a tiered, iterative risk assessment is
to plan and scope the assessment. The EPA provides guidance for this
step in the Risk Characterization Handbook (EPA, 2000) and in the
Framework for Cumulative Risk Assessment (EPA, 2003). The general
process of planning and scoping includes defining the elements that
will or will not be included in the risk assessment and explaining the
purposes for which the risk assessment information will be used (EPA,
2000).
We have already established the motivation for conducting the risk
assessment. Prompted by a petition submitted by the GTA, we conducted
the assessment under section 112(c)(9)(B) of the CAA to determine
whether regulatory relief for the industry was warranted. The
assessment needed to show whether or not any source in each of the four
subcategories exceeds the human health and ecological criteria
described in the statute. In designing the assessment, we considered
the statutory requirements, the amount and type of available
information on the subcategories to include in the assessment, and the
available methods and models.
Based on the criteria, we designed an assessment to estimate cancer
risks and noncancer hazards from a worst-case exposure scenario which
would likely exceed the exposure to the person most exposed. We began
by conducting a human health risk analysis on stationary lean premix
combustion turbines when firing gas and when firing oil at sites where
all turbines fire oil no more than 1,000 hours annually, and stationary
diffusion flame combustion turbines when firing gas and when firing oil
at sites where all turbines fire oil no more than 1,000 hours annually.
To evaluate the risks, hazards and potential for adverse environmental
effects from the emergency turbines and north slope turbines
subcategories, we used available information on the subcategories and
the results of the assessment on the lean premix and diffusion flame
subcategories.
We designed the assessment to address cancer risks and noncancer
hazards to humans from the air and ingestion pathways and also
evaluated the potential for adverse environmental effects. As we
describe above, we used a tiered, iterative approach to the assessment.
Given that there are thousands of facilities in the four subcategories
and that current information on the facilities is limited, it was not
feasible to identify all turbines and their operating characteristics
on a site-specific basis. Therefore, we used a number of health-
protective assumptions where we lacked data. This is an appropriate
approach to evaluating whether to remove a source category or
subcategory from regulation as the CAA specifies that in order to be
delisted, ``no source in the category'' may exceed the cancer,
noncancer or environmental criteria.
We created a worst-case exposure scenario by using a combination of
actual data and health-protective assumptions. For the air pathway, our
approach was to:
(1) Determine which type of turbine would result in the highest
modeled air concentration of HAP.
(2) Hypothetically ``place'' eleven of the turbines at an actual
facility to create our model plant. (An actual facility is permitted
for eleven turbines, but seven turbines are currently operated there.)
(3) Calculate cancer risks, noncancer hazards and the potential for
adverse environmental effects based on the highest ambient air
concentrations of HAP calculated by the model.
For the multipathway analysis, we developed and evaluated an
exposure scenario for our model plant using meteorologic data from
locations around the country: Allentown, PA; Baton Rouge, LA;
Indianapolis, IN; Kansas City, KS; Los Angeles, CA; Minneapolis, MN;
Seattle, WA; and Tampa, FL. Our goal was to account for the effect of
meteorologic variability on the risks and hazards.
We feel the health-protective assumptions we used, when compounded
in the assessment, lead to very health-protective risk estimates. Given
the combination of data and assumptions used, we conducted an
assessment that adequately addresses the questions posed, that is
responsive to the requirements in section 112(c)(9)(B) of the CAA, that
overestimates actual risks, and that shows the statutory criteria for
deletion are met. See the technical memo located in the docket for the
a more detailed description of the analysis (Combustion Turbines Source
Category Risk Characterization, January 2004).
C. Source Characterization
Stationary combustion turbines can be operated in two basic cycles:
simple cycle and combined cycle. The simple cycle mode consists of the
combustion turbine-generator combination operating and producing
electricity with the turbine exhaust vented through a stack directly to
the atmosphere. In the combined cycle mode, the exhaust from the
turbine is passed through a heat recovery steam generator to generate
steam that is then used to produce additional electricity. The heat
extraction at this step cools the exhaust gas stream resulting in a
lower exhaust temperature (reduced plume buoyancy). Thus, emissions
from a turbine operating in the combined cycle mode will often produce
higher ground level pollutant concentrations. As a health-protective
assumption, our analysis only examined the combined cycle units.
To conduct our analysis, we used information on the physical
characteristics of these turbines that was submitted by the petitioner
after we determined the data were of sufficient quality to do so. The
GTA provided data on a set of typical turbines ranging in power output
from 5 to 253 megawatts (MW) each. These characteristics include
turbine type (i.e., make and model), heat input, stack parameters
(height, diameter, exit velocity, temperature), and building
dimensions.
D. Emissions Characterization
With regard to emissions, we agree with the petitioner that the
following HAP are emitted from turbines when natural gas is used as the
fuel: 1,3-butadiene, acetaldehyde, acrolein, benzene, ethylbenzene,
formaldehyde, naphthalene, polycyclic aromatic hydrocarbons (PAH, which
the EPA classifies as a subset of a larger group of HAP, polycyclic
organic matter (POM)), propylene oxide, toluene, and xylenes (mixed).
We also agree with the petitioner that the following non-
[[Page 18332]]
metallic HAP are emitted from turbines when distillate oil is used as
the fuel: 1,3-butadiene, benzene, formaldehyde, naphthalene, and PAH.
However, the petitioner claimed that metallic HAP are not detectable in
distillate oil and are, thus, not present in turbine emissions; they
subsequently amended this claim to state that only chromium and lead
are emitted. We disagree with these claims and have collected
additional data showing the following HAP metals can be emitted when
turbines burn distillate oil, although the levels can vary by oil type:
arsenic, beryllium, cadmium, chromium VI, lead, manganese, mercury,
nickel and selenium. We used emission factors for the emitted HAP that
are based on the most recent available data. Also, we developed
separate emission factors for large and small turbines based on the
burner design-type (lean premix or diffusion flame) and based on the
differences in heat input between small versus large turbines. To
develop health-protective, yet still realistic emission values, we
calculated emission factors for each HAP by selecting the lesser of (1)
the upper 95 percent confidence interval around the mean of each set of
emission factors reported for the HAP or (2) the maximum emission
factor reported for the HAP. We then developed turbine-specific
emission estimates by multiplying the pollutant-specific emission
factors with the heat input of each unit.
E. Air Dispersion Modeling
The goal of our air dispersion modeling approach was to determine
the maximum annual ambient average concentrations of all emitted HAP
that a person living in the vicinity of a turbine could experience. We
used these maximum annual ambient average concentrations, without
regard to whether a person is actually exposed to these concentrations,
as surrogates for exposure. This is a health-protective approach to
assessing exposure.
We used the SCREEN3 model (Version 96043) to estimate the maximum
annual ambient average concentrations of all emitted pollutants.
SCREEN3 consists of algorithms that tend to overestimate HAP
concentrations in air, along with worst-case meteorologic conditions,
to estimate ambient concentrations of HAP in air. This results in
estimates of HAP concentrations in air that are likely to be an
overestimate of what we expect people to actually breathe. We used this
health-protective modeling approach to evaluate the four subcategories
of stationary combustion turbines because it is not feasible to
identify all turbines and their operating characteristics due to the
large number of facilities. Also, we want to ensure that our assessment
is not underestimating potential exposures and risks. This is an
important consideration when we are evaluating whether to grant a
petition to remove a source category from regulation as the CAA
specifies that in order to be delisted, ``no source in the category''
may exceed the cancer, noncancer or environmental criteria.
Our approach to modeling was to first determine which type of
turbine (of the ten turbine types identified by the petitioner)
produces the highest maximum annual ambient average concentrations
using SCREEN3. We then simulated a facility and ran SCREEN3 for all HAP
emitted from lean premix gas-fired turbines and also for diffusion
flame gas-fired turbines, using regulatory default mode, full
meteorology, building downwash, flat nearby terrain, rural dispersion,
automated receptor arrangement (50-2000 meter), and a conversion factor
of 0.08 to obtain annual average concentrations from maximum 1-hour
concentrations. As stated above, we used turbine characteristics
submitted by the petitioner and developed updated emission factors
ourselves. We used these data as inputs into the SCREEN3 model in order
to obtain the maximum annual average air concentrations from a worst-
case type of turbine. Our dispersion modeling showed that the W501F
turbine resulted in the highest air concentrations.
After establishing that maximum annual ambient average
concentrations are the highest from the W501F turbine, we simulated
another facility. We placed 11 W501F turbines at our simulated facility
because the highest number of large turbines permitted to operate at an
actual facility is 11. After accounting for source separation (see
technical memo for details), we ran SCREEN3 on our simulated facility
for four scenarios: (1) Assuming the 11 turbines are lean premix gas-
fired turbines collectively using 1,000 hours of oil per year; (2)
assuming the 11 turbines are diffusion flame gas-fired turbines
collectively using 1,000 hours of oil per year; (3) assuming the 11
turbines are lean premix and burn only natural gas; and (4) assuming
the 11 turbines are diffusion flame turbines and burn only natural gas.
We conducted the analyses assuming the turbines burn only natural gas,
and assuming the turbines burn natural gas plus 1,000 hours of oil per
year because not all facilities use oil, and because emissions are
different when only natural gas is used as fuel (no metals are emitted
but formaldehyde emissions are higher). The maximum annual ambient
average concentrations for each emitted pollutant for natural gas plus
1,000 hours of oil per year and for natural gas only for the 11 W501F
turbines can be found in Table 4 of the technical memo (see docket).
We consider the maximum annual average concentrations resulting
from our dispersion modeling analysis to be health-protective. That is,
we feel that the resulting air concentrations over- rather than under-
estimate actual exposures to people. This is because our analysis used
health-protective source parameters and atmospheric dispersion modeling
methodology; relied on health-protective emission factors for all HAP;
used the maximum annual ambient average concentrations of the emitted
HAP as a surrogate for exposure; and assumed 70 years, 24 hours a day,
365 days a year of continuous exposure. Even though actual emission
rates, and thus ambient concentrations, of HAP may increase above
annual average levels during certain short-duration transient
operations such as unit startup, the health-protective analysis
approach accounts for such transient increases in the health-protective
estimates of annual average exposures. Thus, the analyses, even though
they do not explicitly incorporate these short term events, reasonably
account for these events and result in health-protective estimates of
risk.
F. Human Health Effects of Emitted HAP
Although numerous HAP may be emitted from combustion turbines, a
few account for essentially all the mass of HAP emissions from
stationary combustion turbines. These HAP are formaldehyde, toluene,
benzene, and acetaldehyde. Other emitted HAP are of potential concern
not so much because of the emitted amounts, but due to their high
potency via the inhalation route. These include arsenic and PAH. Four
of the emitted HAP are of potential concern from the ingestion route:
PAH, which are of concern for cancer; and cadmium, lead and mercury
which are of concern for noncarcinogenic effects.
The HAP emitted in the largest quantity is formaldehyde.
Formaldehyde is a probable human carcinogen and can cause irritation of
the eyes and respiratory tract, coughing, dry throat, tightening of the
chest, headache, and heart palpitations. Acute (short-term) inhalation
has caused bronchitis, pulmonary edema, pneumonitis, pneumonia, and
death due to respiratory failure. Chronic (long-
[[Page 18333]]
term) exposure can cause dermatitis and sensitization of the skin and
respiratory tract.
Other HAP emitted in significant quantities from stationary
combustion turbines include toluene, benzene, and acetaldehyde. The
health effect of primary concern for toluene is dysfunction of the
central nervous system (CNS). Toluene vapor also causes narcosis.
Controlled exposure of human subjects produced mild fatigue, weakness,
confusion, lacrimation, and paresthesia; at higher exposure levels
there were also euphoria, headache, dizziness, dilated pupils, and
nausea. After-effects included nervousness, muscular fatigue, and
insomnia persisting for several days. Acute exposure may cause
irritation of the eyes, respiratory tract, and skin. It may also cause
fatigue, weakness, confusion, headache, and drowsiness. Very high
concentrations may cause unconsciousness and death.
Benzene is a known human carcinogen. The health effects of benzene
include nerve inflammation, CNS depression, and cardiac sensitization.
Acute exposure can cause dizziness, euphoria, giddiness, headache,
nausea, staggering gait, weakness, drowsiness, respiratory irritation,
pulmonary edema, pneumonia, gastrointestinal irritation, convulsions,
and paralysis. Benzene can also cause irritation to the skin, eyes, and
mucous membranes. Chronic exposure to benzene can cause fatigue,
nervousness, irritability, blurred vision, and labored breathing and
has produced anorexia and irreversible injury to the blood-forming
organs; effects include aplastic anemia and leukemia.
Acetaldehyde is a probable human carcinogen. Inhalation exposures
to acetaldehyde can cause irritation of the eyes, mucous membranes,
skin, and upper respiratory tract, and CNS depression in humans. Acute
exposure can cause conjunctivitis, coughing, difficult breathing, and
dermatitis. Chronic exposure may cause heart and kidney damage,
embryotoxicity, and teratogenic effects.
Arsenic, a naturally occurring element, is found throughout the
environment. For most people, food is the major source of exposure to
arsenic. The EPA has classified inorganic arsenic as a human
carcinogen. Acute high-level inhalation exposure to arsenic dust or
fumes has resulted in gastrointestinal effects (nausea, diarrhea,
abdominal pain); central and peripheral nervous system disorders have
occurred in workers acutely exposed to inorganic arsenic. Chronic
inhalation exposure to inorganic arsenic in humans is associated with
irritation of the skin and mucous membranes. Chronic oral exposure has
resulted in gastrointestinal effects, anemia, peripheral neuropathy,
skin lesions, hyperpigmentation, and liver or kidney damage in humans.
Inorganic arsenic exposure in humans, by the inhalation route, has been
shown to be strongly associated with lung cancer, while ingestion of
inorganic arsenic in humans has been linked to a form of skin cancer
and also to bladder, liver, and lung cancer.
Polycyclic aromatic hydrocarbons are a group of compounds that fit
within the POM HAP category. Dermal exposures to mixtures of PAH cause
skin disorders in humans and animals. No information is available on
the reproductive or developmental effects of PAH mixtures in humans,
but animal studies have reported that oral exposure to benzo(a)pyrene
(BaP, a PAH compound) causes reproductive and developmental effects.
Human studies have reported an increase in lung cancer in humans
exposed to PAH-bearing mixtures including coke oven emissions, roofing
tar emissions, and cigarette smoke. Animal studies have reported
respiratory tract tumors from inhalation exposure to BaP and
forestomach tumors, leukemia, and lung tumors from oral exposure to
BaP. The EPA has classified seven PAH compounds: (BaP,
benz(a)anthracene, chrysene, benzo(b)fluoranthene,
benzo(k)fluoranthene, dibenz(a,h)anthracene, and indeno(1,2,3-
cd)pyrene) as Group B2, probable human carcinogens.
The EPA reports in the Integrated Risk and Exposure Assessment
(IRIS) that cadmium has been shown to cause kidney damage via the oral
route. IRIS also reports that there are no positive cancer studies of
orally ingested cadmium suitable for quantification. Consequently, we
evaluated noncancer hazards only for cadmium ingestion. The major
effect from chronic oral exposure to inorganic mercury is also kidney
damage. Animal studies have reported effects such as alterations in
testicular tissue, increased resorption rates, and abnormalities of
development from oral exposure to inorganic mercury. Mercuric chloride
(an inorganic mercury compound) exposure has been shown to result in
forestomach, thyroid, and renal tumors in experimental animals. For
lead, oral exposures can lead to central nervous system effects, as
well as effects on the blood, blood pressure, kidneys and Vitamin D
metabolism. Children are especially sensitive to the chronic effects of
lead, and can exhibit slowed cognitive development and reduced growth.
G. Human Health Values Used
We used the human health values currently used by EPA's air toxics
program and available at: http://www.epa.gov/ttn/atw/toxsource/summary.html. These dose response values come from several sources
including EPA's IRIS, the United States Department of Health and Human
Service's Agency for Toxic Substances Disease Registry, and California
EPA. See Table 5 in our technical memo for a summary of the human
health values we used in our assessment.
For formaldehyde, we do not use the dose-response value reported in
IRIS. The dose-response value in IRIS is based on a 1987 study, and no
longer represents the best available science in the peer-reviewed
literature. Since that time, significant new data and analysis have
become available. We based the dose-response value we used for
formaldehyde on work conducted by the CIIT Centers for Health Research
(CIIT). In 1999, the CIIT published a risk assessment which
incorporated mechanistic and dosimetric information on formaldehyde
that had been accumulated over the past decade. The risk assessment
analyzed carcinogenic risk from inhaled formaldehyde using approaches
that are consistent with EPA's draft guidelines for carcinogenic risk
assessment. The CIIT model is based on computational fluid dynamics
(CFD) models of airflow and formaldehyde delivery to the relevant parts
of the rat and human respiratory tract, which are then coupled to a
biologically-motivated, two-staged clonal growth model that allows for
incorporation of different biological effects. These biological
effects, such as interaction with DNA and cell proliferation, are
processes by which formaldehyde may contribute to development of cancer
at sites exposed at the portal of entry (e.g., respiratory tract). The
two-staged model is a much more advanced approach for examining the
relevance of tumors seen in animal models for human populations. The
CIIT information and other recent information, including recently
published epidemiological studies, are being reviewed and considered in
the reassessment of our formaldehyde unit risk estimate (URE).
We believe that the CIIT modeling effort represents the best
available application of the available mechanistic and dosimetric
science on the dose-response for portal of entry cancers due to
formaldehyde exposures. We note here that other organizations,
including
[[Page 18334]]
Health Canada, have adopted this approach. Accordingly, we have used
risk estimates based on the CIIT airflow model coupled to a two-staged
clonal growth model as the basis for the dose-response values for this
analysis. The formaldehyde risk value obtained by extrapolating with
the CIIT model that we used in our analysis differs slightly from the
values used by the petitioner. The CIIT model incorporates state-of-
the-art analyses for species-specific dosimetry, and encompasses more
of the available biological data than any other currently available
model. As with any model, uncertainties exist, and the CIIT model is
sensitive to the inputs, but we believe it represents the best
available approach for assessing the risk of portal-of-entry cancers
due to formaldehyde exposures.
H. Human Health Risk Results--Air Pathway
We calculated the maximum excess lifetime cancer risk for the Air
pathway that results from the exposure scenario described above. We
estimated risks for both the primary firing of natural gas with 1,000
hours of oil firing per year, per facility, and for the continuous
firing of natural gas. Diffusion flame gas-fired turbines produced the
highest risk. When firing natural gas plus 1,000 hours of oil per year,
the total excess lifetime cancer risk from all the emitted pollutants
from the diffusion flame turbines in our analysis is 7.7 x
10-\7\. The total excess lifetime cancer risk from
continuous burning of natural gas for our modeled scenario is 3.9 x
10-\7\.
In addition to estimating cancer risks, we evaluated noncancer
hazards for each pollutant for which there is a noncancer human health
value. To do this, we used a hazard quotient (HQ) approach and
calculated the ratio of the exposure concentration to the noncancer
human health value (e.g., inhalation reference concentration (RfC)) for
each emitted HAP. This is represented by the formula HQ= (exposure
concentration)/(RfC). The RfC is a peer-reviewed value defined as an
estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily inhalation exposure to the human population (including sensitive
subgroups) that is likely to be without appreciable risk of deleterious
noncancer effects during a lifetime.
We then generated hazard indices (HI) by summing HQ across HAP. We
can generate two types of hazard indices. The first type is generated
by adding HQ for all emitted HAP regardless of their target organ. This
results in an HI that is considered health-protective since the HQ for
all pollutants are added even though some pollutants cause distinctly
different effects. For our modeled scenario, the total HI for the
natural gas plus 1,000 hours of oil scenario is 0.6. The HI for the
natural gas burning scenario is 0.4.
We can also calculate HI by summing HQ from HAP that affect the
same target organ. In this assessment, pollutants that affect the same
target organ are acrolein and formaldehyde; they affect the respiratory
system. These also are the two HAP with the highest individual hazard
quotients. When accounting for the fact that acrolein and formaldehyde
affect the same target organ, we calculate a HI of 0.4. None of the
other HAP affect the same target organ, thus, we calculated a HI for
the respiratory system only. The other HAP had HQ ranging from
10-\6\ (nickel) to 0.1 (manganese).
I. Multipathway Considerations
In order to fully characterize risks and hazards to humans from the
subcategories, we considered exposures from ingestion as well as
inhalation for four of the emitted HAP: cadmium, lead, mercury and PAH.
We chose these HAP because of all the HAP emitted, only these four
appear on lists of chemicals that EPA considers to be persistent,
bioaccumulative, and toxic (PBT) substances under the Pollution
Prevention Program, the Great Waters Program, or the Toxics Release
Inventory. (See the multipathway HAP memo in the docket for more
information.) Therefore, in addressing the potential for the
subcategories to be of concern due to multipathway routes of exposure,
we need to consider emissions of cadmium, lead, mercury and PAH.
Several of the emitted PAH are carcinogenic via the ingestion
pathway and, thus, we evaluated these pollutants in the multipathway
analysis: benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene,
benzo(k)fluoranthene, chrysene, dibenz(a,h)anthracene, and indeno
(1,2,3-cd)pyrene. We evaluated noncancer health effects for cadmium,
lead, mercury and the following noncarcinogenic PAH: Acenaphthene,
fluoranthene, fluorene, and pyrene.
To evaluate the potential for these HAP to cause cancer risk or
noncancer hazard to humans due to ingestion, we conducted a screening
level multipathway analysis. As with the inhalation assessment, we did
not have enough data to evaluate actual exposures across the entire
source category. We did not structure this assessment to reflect actual
exposures, rather we developed a worst-case exposure model scenario
based on limited data and assumptions which, when considered in total,
provide for a health-protective analysis. This approach ensures that we
are not underestimating actual risks and hazards from emissions from
the four subcategories.
We structured this analysis to estimate maximum risks to an
individual exposed via routes other than inhalation (e.g., ingestion of
contaminated food) for HAP emitted from combustion turbines. We used
our modeled facility and evaluated human ingestion of contaminated
food, water and soil. We generally followed the Human Health Risk
Assessment Protocol for Hazardous Waste Combustion Facilities (HHRAP)
(U.S. EPA, 1998) to conduct the multipathway portion of the assessment.
The HHRAP provided the primary source of chemical-specific parameter
values and default environmental parameters. We started with the
HHRAP's parameter values and replaced specific inputs as necessary,
either due to updated science or due to policy choices that we made in
order to be consistent with the mandate to assess risks to the
individual most exposed.
To evaluate a worst-case potential exposure from our modeled
facility, we used a subsistence farmer scenario. This scenario reflects
an adult living on a farm that we hypothetically assumed to be located
close to our modeled facility. We assumed the farmer consumes meat
(pork and beef), dairy, fruit, and vegetables that the farm produces as
a portion of his/her diet. The animals raised on the farm subsist
primarily on feed grown on the farm. We also assumed that the farmer is
a recreational fisher and eats the fish he/she catches. Finally, we
assumed that the farmer drinks treated, local surface water (water
which has gone through minimal municipal treatment).
For several reasons, we consider this approach to multipathway
assessment scenario to be health-protective. We used the maximum
ambient air concentrations from our modeled facility which, as we have
stated above, produces higher ambient air concentrations than we expect
to actually occur anywhere in the U.S. Also, we used a water body size,
flow rate, watershed size and other parameters that were developed for
the health protective analysis scenario analyzed in the Mercury Study
Report to Congress. Further, we applied maximum pollutant deposition
rates to the entire watershed. Thus, we feel our modeled scenario will
over-predict
[[Page 18335]]
actual risks and hazards from ingestion and is, therefore, health-
protective.
We estimated both cancer risk and noncancer hazards from all the
ingestion pathways: water, meats, fruits, vegetables, soil, and fish.
The results of our multipathway analysis show that the cancer risks
from PAH are 0.16 in 1 million (1.6 x 10-\7\). This is below
the statutory cancer risk criterion of 1 in 1 million. When we add
these risks to the lifetime excess cancer risks of 7.7 x
10-\7\ from the inhalation pathway, we get a total cancer
risk of .93 in 1 million, which rounds to 0.9 in 1 million (0.9 x
10-\6\). Such a summation of risks is appropriate only if it
is plausible that the person with the maximum risks from the air
pathway is also the person with the maximum risk from the ingestion
pathway. Inherent in this assumption is that these two maximum
concentrations (therefore, the maximum risk and hazards) occur at the
exact same location. While we calculated risk and hazards for such a
person, we feel it very unlikely that one person would be located at
the point of highest impact from both inhalation and ingestion. If we
had more site-specific data with which to conduct this assessment, we
would likely have found that the maximum impact from inhalation was not
in the same location as the maximum impact from ingestion, and the
risks would be lower. We consider it inappropriate to use this combined
inhalation/ingestion scenario because we consider it to be implausible.
We feel that the actual combined risks, from all pathways, will be
lower than 1 in 1 million and, therefore, the statutory criteria are
met.
We estimated noncancer hazards for cadmium and mercury, combining
hazards from all ingestion pathways. The highest total hazard index for
all ingestion pathways is 0.1. Noncancer hazards are driven by methyl
mercury via ingestion of fish. The HQ for mercury for this route of
exposure is also 0.1; it is clearly the driver for multipathway
noncancer effects.
The EPA uses a slightly different approach in order to assess the
hazard from ingestion exposures to lead. In general, we use a protocol
like that in HHRAP to obtain media concentrations. We use an additional
model called the Integrated Exposure, Uptake and Biokinetic Model
(IEUBK) to estimate blood lead levels. We then calculate an HQ. In this
analysis, the inhalation HQ for lead was so low, 0.000008, that we
found it unnecessary to take the additional step of modeling further
with the IEUBK. Based on previous analyses we have conducted on lead,
we do not feel that an air concentration that leads to an HQ of
0.000008 would translate into an HQ of concern from the ingestion route
of exposure. The ingestion HQ would have to be four to five orders of
magnitude higher than the HQ from the air pathway to even approach a
level of concern. Given the very low inhalation HQ for lead from
exposure to the turbine subcategories, the lead emissions from the four
subcategories do not exceed a level that is adequate to protect the
public health with an ample margin of safety. Therefore, we conclude
that both risks and hazards to humans due to multipathway exposures
from all HAP emitted from the four combustion turbine subcategories
meet the required human health criteria in CAA section 112(c)(9)(B).
Emissions that result in the maximum modeled lifetime excess cancer
risk of 0.9 in 1 million are within the statutory criteria. With regard
to noncancer effects, we consider the emissions resulting in a target
organ-specific HI of 0.4 from the turbine subcategories do not exceed a
level that is adequate to protect the public health with an ample
margin of safety. We consider the actual risks and hazards from the
turbines in the four subcategories to be lower than what we estimated
here due to the health-protective assumptions we included in this
assessment. For example, in characterizing the physical and operational
attributes of the turbines, we assumed all turbines were operating in
combined cycle, used worst-case meteorology, and included the potential
for building downwash. These assumptions lead to exposures which we
feel are higher than what we would find from an actual plant. In
addition, we assumed that individuals are exposed to the maximum
modeled concentrations of HAP in the air continuously for their entire
lives (which we approximated as 70 years), and we used the maximum
annual average concentration as a surrogate for exposure. These
assumptions are also health-protective.
J. Effects Due to Acute Exposure
We determined that emissions from turbines are of concern for long-
term (chronic) exposures and not from short-term (acute) exposures.
Short-term exposures may arise when a facility starts up or shuts down
equipment, which may result in short bursts of high emissions due to
the fact that the unit is not running at peak efficiency during the
time it takes to start up or shut down. For other types of source
categories, this can lead to exposures that result in adverse health
effects. In the case of gas-fired turbines, we have determined that
upon start up, they reach peak efficiency quickly, therefore, limiting
any bursts of emissions. Shut downs take a short amount of time as
well. The HAP emitted from combustion turbines have not been associated
with acute health effects at the concentrations predicted in the
analyses. While the short-duration emissions may slightly increase the
overall cancer risks, this effect would be so small as to be
inconsequential. Therefore, we conclude that the acute exposures to HAP
emissions from stationary combustion turbines are not of concern.
K. Environmental Effects Evaluation
In order to assess whether the emissions from our modeled facility
could lead to adverse environmental effects, we performed a screening-
level ecological risk assessment. We evaluated the inhalation pathway
for terrestrial mammals, the ingestion pathway for terrestrial
wildlife, contact with sediment for benthic species, and contact with
soil for terrestrial plants. We did not evaluate terrestrial plants
exposed via direct contact with the air due to a lack of toxicity data.
We contend that human toxicity values we used in this analysis for
the inhalation route are protective of inhalation exposures that may be
experienced by terrestrial mammals. The human health values were
derived based on human studies and also considered studies on small
laboratory animals, primarily rodents. These values are significantly
less than the level to which an experimental animal was exposed.
Because the maximum cancer risk and noncancer hazards to humans from
inhalation exposure are all below a level of concern, we expect there
to be no significant and widespread adverse effects to terrestrial
mammals from inhalation exposures to HAP emitted from gas-fired
turbines.
In order to assess whether the continuing emissions from our
modeled facility could contribute to adverse environmental effects from
the ingestion pathway, we performed a screening-level ecological risk
assessment. For screening purposes, we intentionally designed the
assessment to be health-protective of ecological receptors. We did not
intend the assessment to be used in predicting specific types of
effects to individuals, species, populations, or communities, or to the
structure and function of the ecosystem. We used the assessment to
identify HAP which may pose potential risk or hazard to ecological
receptors and, therefore, would need to be evaluated in a more refined
level of risk assessment.
[[Page 18336]]
For screening endpoints, we used the structure and function of
generic aquatic and terrestrial populations and communities, including
threatened and endangered species, that might be exposed to HAP
emissions via soil or water. The assessment endpoints are relatively
generic with respect to descriptions of the environmental values that
are to be protected and the characteristics of the ecological entities
and their attributes. We assumed in the assessment that these
ecological receptors were representative of sensitive individuals,
populations, and communities present near these facilities.
The HAP we included in the quantitative ecological assessment are
the same HAP that we evaluated in the multipathway human health
assessment: cadmium, lead, mercury and PAH. We derived estimated media
concentrations for each of these HAP from the media concentrations
estimated in the multipathway exposures assessment. We chose exposure
pathways to reflect the potential routes of exposure through sediment,
soil, water, and air. We selected these environments because they are
considered representative of locations of generic populations and
communities most likely to be exposed to the HAP. Within these
environments, the receptors evaluated consisted of two distinct groups:
terrestrial and aquatic (i.e., including aquatic, benthic, and soil
organisms; terrestrial plants and wildlife; and herbivorous,
piscivorus, and carnivorous wildlife).
The chronic ecological toxicity screening values used in the
assessment were estimates of the maximum concentrations that would not
be expected to affect survival, growth, or reproduction of sensitive
species after long-term (more than 30 days) exposure to HAP. We
screened HAP, pathways, and receptors using the ecological HQ method,
which simply calculates the ratio of the estimated environmental
concentrations to the selected ecological screening values.
The results of our ecological assessment show that for all
pollutants assessed, and for all pathways assessed, the ecological HQ
values are less than 1. Therefore, it is not likely that any of the HAP
emitted would pose an ecological risk to ecosystems near any of these
facilities.
With regard to endangered species, we assumed that the screening
values were protective of sensitive species, including threatened or
endangered species. There are no available ecological toxicity test
data for threatened and endangered species for these HAP. As such, the
actual sensitivities of any threatened or endangered species located in
the vicinity of these facilities is unknown. However, in order to be
health-protective, we selected ecological screening values for the most
sensitive species available for use in the analysis. Also, we are not
familiar with any species that have become threatened or endangered as
a result of emissions of these chemicals from stationary combustion
turbines. Therefore, we feel it is not likely that any threatened and
endangered species, if they exist around these facilities, would be
adversely affected by these HAP emissions.
V. Analysis of the Emergency Turbine Subcategory
Emergency stationary combustion turbines are stationary combustion
turbines that operate in an emergency situation. Examples include
stationary combustion turbines used to produce power for critical
networks or equipment (including power supplied to portions of a
facility) when electric power from the local utility is interrupted, or
stationary combustion turbines used to pump water in the case of fire
or flood, etc. Emergency stationary combustion turbines do not include
stationary combustion turbines used as peaking units at electric
utilities or stationary combustion turbines at industrial facilities
that typically operate at low capacity factors. Emergency stationary
combustion turbines may be operated for the purpose of maintenance
checks and readiness testing, provided that the tests are required by
the manufacturer, the vendor, or the insurance company associated with
the turbine.
Usually one or two emergency turbines are located at a given
facility. These units run mostly on oil and operate approximately 30
hours per year, per turbine. Regular testing of these units (done to
ensure they will be operational during an emergency) may bring the
total operating hours for a turbine up toward 200 hours per year, per
turbine, or approximately 400 hours per facility. Given that these
units burn less oil than allowed under the MACT standards for lean
premix and diffusion flame gas-fired turbines (1,000 hours per
facility), we expect the maximum annual average HAP concentrations in
air to be much less for emergency turbines. Therefore, we expect the
risks and hazards to be less.
VI. Analysis of the North Slope Turbine Subcategory
We have identified 120 stationary combustion turbines that are
located on the North slope of Alaska. Of these, 112 are diffusion flame
gas-fired units, and eight are lean premix gas-fired turbines. The
total number of oil hours used, per year, by any facility we identified
on the North Slope is much less than 1,000 hours. Because we have
determined that facilities burning oil for fewer than 1,000 hours per
year meet the statutory criteria for delisting, we concluded that
stationary combustion turbines located on the North Slope of Alaska
also meet the delisting criteria.
Given the standard EPA risk assessment methods used, and the
health-protective assumptions made in the assessment, we have made an
initial determination that all sources in the four subcategories meet
the human health and environmental criteria in CAA section 112(c)(9)(B)
and should be removed from the source category list.
VII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
Under Executive Order 12866 (58 FR 51735, October 4, 1993), EPA
must determine whether the regulatory action is ``significant'' and,
therefore, subject to Office of Management and Budget (OMB) review and
the requirements of the Executive Order. The Executive Order defines
``significant regulatory action'' as one that is likely to result in a
rule that may:
(1) Have an annual effect on the economy of $100 million or more or
adverse affect in a material way the economy, a sector to the economy,
productivity, competition, jobs, the environment, public health or
safety, or state, local or tribal governments or communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs, or the rights and obligation of recipients
thereof; or
(4) raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
Pursuant to the terms of Executive Order 12866, it has been
determined that the proposed action constitutes a ``significant
regulatory action'' because it may raise novel policy issues and is
therefore subject to OMB review. Changes made in response to OMB
suggestions or recommendations are documented in the public record (see
ADDRESSES section of this preamble).
[[Page 18337]]
B. Paperwork Reduction Act
This action does not impose an information collection burden under
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq.
The proposed action will remove two subcategories from the combustion
turbine source category and, therefore, eliminate the need for
information collection toward regulatory compliance under the CAA.
Burden means the total time, effort, or financial resources expended by
persons to generate, maintain, retain, or disclose or provide
information to or for a Federal agency. This includes the time needed
to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to
comply with any previously applicable instructions and requirements;
train personnel to be able to respond to a collection of information;
search data sources; complete and review the collection of information;
and transmit or otherwise disclose the information. An Agency may not
conduct or sponsor, and a person is not required to respond to a
collection of information unless it displays a currently valid OMB
control number. The OMB control numbers for EPA's regulations are
listed in 40 CFR part 9 and 48 CFR chapter 15.
C. Regulatory Flexibility Act
The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice and comment rulemaking requirements under the Administrative
Procedure Act or any other statute unless the agency certifies that the
rule will not have a significant economic impact on a substantial
number of small entities. Small entities include small business, small
organizations, and small governmental jurisdictions. For the purposes
of assessing the impacts of today's proposed action on small entities,
small entity is defined as: (1) A small business that meets the
definitions for small business based on the Small Business Association
(SBA) size standards which, for this proposed action, can include
manufacturing (NAICS 3999-03) and air transportation (NAICS 4522-98 and
4512-98) operations that employ less than 1,000 people and engineering
services (NAICS 8711-98) operations that earn less than $20 million
annually; (2) a small governmental jurisdiction that is a government of
a city, county, town, school district or special district with a
population of less than 50,000; and (3) a small organization that is
any not-for-profit enterprise which is independently owned and operated
and is not dominant in its field.
After considering the economic impact of today's proposed action on
small entities, I certify that the proposed action will not have a
significant economic impact on a substantial number of small entities.
In determining whether a rule has significant economic impact on a
substantial number of small entities, the impact of concern is any
significant adverse economic impact on small entities, since the
primary purpose of the regulatory flexibility analysis is to identify
and address regulatory alternatives ``which minimize any significant
economic impact of the proposed rule on small entities.'' (5 U.S.C. 603
and 604). Thus, an agency may certify that a rule will not have a
significant economic impact on a substantial number of small entities
if the rule relieves regulatory burden, or otherwise has a positive
economic effect on all of the small entities subject to the rule. The
proposed rule will eliminate the burden of additional controls to be
applied to two subcategories of the combustion turbine source category,
and associated operating, monitoring and reporting requirements. We
have, therefore, concluded that today's proposed rule will relieve
regulatory burden for all small entities. We continue to be interested
in the potential impacts of the proposed rule on small entities and
welcome comments on issues related to such impacts.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 1044, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures to State, local, and tribal governments, in
the aggregate, or to the private sector, of $100 million or more in any
1 year. Before promulgating an EPA rule for which a written statement
is needed, section 205 of the UMRA generally requires EPA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost-effective or least burdensome alternative
that achieves the objectives of the rule. The provisions of section 205
do not apply when they are inconsistent with applicable law. Moreover,
section 205 allows EPA to adopt an alternative other than the least
costly, most cost-effective or least burdensome alternative if the
Administrator publishes with the final rule an explanation why that
alternative was not adopted. Before EPA establishes any regulatory
requirements that may significantly or uniquely affect small
governments, including tribal governments, it must have developed under
section 203 of the UMRA a small government agency plan. The plan must
provide for notifying potentially affected small governments, enabling
officials of affected small governments to have meaningful and timely
input in the development of EPA regulatory proposals with significant
Federal intergovernmental mandates, and informing, educating, and
advising small governments on compliance with the regulatory
requirements.
Today's proposed rule contains no Federal mandates for State,
local, or tribal governments or the private sector. The proposed rule
imposes no enforceable duty on any State, local or tribal governments
or the private sector. In any event, EPA has determined that the
proposed rule does not contain a Federal mandate that may result in
expenditures of $100 million or more for State, local, and tribal
governments, in the aggregate, or the private sector in any 1 year.
Because the proposed rule removes two subcategories from the combustion
turbine source category from regulatory consideration, it actually
reduces the burden established under the CAA. Thus, today's proposed
rule is not subject to the requirements of sections 202 and 205 of the
UMRA.
E. Executive Order 13132: Federalism
Executive Order 13132 (64 FR 43255, August 10, 1999) requires EPA
to develop an accountable process to ensure ``meaningful and timely
input by State and local officials in the development of regulatory
policies that have federalism implications.'' ``Policies that have
federalism implications'' is defined in the Executive Order to include
regulations that have ``substantial direct effects on the States, on
the relationship between the national government and the States, or on
the distribution of power and responsibilities among the various levels
of government.''
The proposed rule does not have federalism implications. It will
not have substantial direct effects on the States, on the relationship
between the national government and the States, or on the distribution
of power and responsibilities among the various levels of government,
as specified in
[[Page 18338]]
Executive Order 13132. Thus, Executive Order 13132 does not apply to
the proposal.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
Executive Order 13175 (65 FR 67249, November 9, 2000) requires EPA
to develop an accountable process to ensure ``meaningful and timely
input by tribal officials in the development of regulatory policies
that have tribal implications.'' The proposed rule does not have tribal
implications, as specified in Executive Order 13175. The proposed
action will eliminate control requirements for two subcategories from
the combustion turbine source category and, therefore, reduces control
costs and reporting requirements for any tribal entity operating a
turbine contained in either of these subcategories. Thus, Executive
Order 13175 does not apply to the proposed rule.
G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any
rule that: (1) Is determined to be ``economically significant'' as
defined under Executive Order 12866, and (2) concerns an environmental
health or safety risk that EPA has reason to believe may have a
disproportionate effect on children. If the regulatory action meets
both criteria, the Agency must evaluate the environmental health or
safety effects of the planned rule on children, and explain why the
planned regulation is preferable to other potentially effective and
reasonably feasible alternatives considered by the Agency.
The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that are based on health or safety risks, such that
the analysis required under section 5-501 of the Executive Order has
the potential to influence the regulation. The proposed rule is not
subject to Executive Order 13045 because it is not economically
significant as defined in Executive Order 12866, and because the Agency
does not have reason to believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children. This determination is based on the fact that the noncancer
human health values we used in this analysis (e.g., RfC) are determined
to be protective of sensitive sub-populations, including children.
Also, while the cancer human health values do not always expressly
account for cancer effects in children, the cancer risks posed by
turbines in these two subcategories are sufficiently low so as not to
be concern for anyone in the population, including children. In
addition, the public is invited to submit or identify peer-reviewed
studies and data, of which the Agency may not be aware, that assesses
results of early life exposure to the HAP emitted by lean premix gas-
fired combustion turbines and diffusion flame gas-fired combustion
turbines.
H. Executive Order 13211, Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
The proposed rule is not subject to Executive Order 13211 (66 FR
28355, May 22, 2001) because it is not a significant regulatory action
under Executive Order 12866.
I. National Technology Transfer and Advancement Act
Section 112(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), (Public Law No. 104-113, section 12(d) 915 U.S.C.
272 note), directs all Federal agencies to use voluntary consensus
standards instead of government-unique standards in their regulatory
activities unless to do so would be inconsistent with applicable law or
otherwise impractical. Voluntary consensus standards are technical
standards (e.g., material specifications, test method, sampling and
analytical procedures, business practices, etc.) that are developed or
adopted by one or more voluntary consensus standards bodies. Examples
of organizations generally regarded as voluntary consensus standards
bodies include the American Society for Testing and Materials, the
National Fire Protection Association A), and the Society of Automotive
Engineers. The NTTAA requires Federal agencies like EPA to provide
Congress, through OMB, with explanations when an agency decides not to
use available and applicable voluntary consensus standards. The
proposed rule does not involve technical standards. Therefore, EPA is
not considering the use of any voluntary consensus standards.
List of Subjects in 40 CFR Part 63
Environmental protection, Air pollution control, Hazardous
substances, Reporting and recordkeeping requirements.
Dated: March 31, 2004.
Michael O. Leavitt,
Administrator.
[FR Doc. 04-7775 Filed 4-6-04; 8:45 am]
BILLING CODE 6560-50-P