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Notice2021-22233

Notice of Request for Approval of Alternative Means of Emission Limitation

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Published

October 13, 2021

Issuing agencies

Environmental Protection Agency

Abstract

On April 21, 2020, Flint Hills Resources (FHR) requested an alternative means of emission limitation (AMEL) under the Clean Air Act (CAA) in order to utilize a leak detection sensor network (LDSN) with a detection response framework (DRF) at its West and East Refineries located in Corpus Christi, Texas. In this document, the EPA is soliciting comment on all aspects of the AMEL request and resulting alternative leak detection and repair (LDAR) requirements that are necessary to achieve a reduction in emissions of volatile organic compounds (VOC) and hazardous air pollutants (HAPs) at least equivalent to the reduction in emissions required by the applicable LDAR standards. This document also presents and solicits comment on all aspects of a framework for future LDSN-DRF AMEL requests, which would afford the EPA the ability to evaluate those requests in a more efficient and streamlined manner.

Full Text

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<title>Federal Register, Volume 86 Issue 195 (Wednesday, October 13, 2021)</title>
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[Federal Register Volume 86, Number 195 (Wednesday, October 13, 2021)]
[Notices]
[Pages 56934-56949]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2021-22233]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OAR-2021-0299; FRL-8193-02-OAR]

Notice of Request for Approval of Alternative Means of Emission
Limitation

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice and request for comments.

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SUMMARY: On April 21, 2020, Flint Hills Resources (FHR) requested an
alternative means of emission limitation (AMEL) under the Clean Air Act
(CAA) in order to utilize a leak detection sensor network (LDSN) with a
detection response framework (DRF) at its West and East Refineries
located in Corpus Christi, Texas. In this document, the EPA is
soliciting comment on all aspects of the AMEL request and resulting
alternative leak detection and repair (LDAR) requirements that are
necessary to achieve a reduction in emissions of volatile organic
compounds (VOC) and hazardous air pollutants (HAPs) at least equivalent
to the reduction in emissions required by the applicable LDAR
standards. This document also presents and solicits comment on all
aspects of a framework for future LDSN-DRF AMEL requests, which would
afford the EPA the ability to evaluate those requests in a more
efficient and streamlined manner.

DATES: Comments. Comments must be received on or before November 29,
2021.
Public hearing: If anyone contacts us requesting a public hearing
on or before October 18, 2021, the EPA will hold a virtual public
hearing on October 28, 2021. Please refer to the SUPPLEMENTARY
INFORMATION section for additional information on the public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2021-0299, by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
(our preferred method). Follow the online instructions for submitting
comments.
<bullet> Email: <a href="/cdn-cgi/l/email-protection#70115d111e145d025d141f131b1504301500115e171f06">[email&#160;protected]</a>. Include Docket ID No. EPA-
HQ-OAR-2021-0299 in the subject line of the message.
<bullet> Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2021-0299.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2021-0299, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
<bullet> Hand Delivery or Courier (by scheduled appointment only):
EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution
Avenue NW, Washington, DC 20004. The Docket Center's hours of operation
are 8:30 a.m.-4:30 p.m., Monday - Friday (except Federal holidays).
Instructions. All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the SUPPLEMENTARY
INFORMATION section of this document. Out of an abundance of caution
for members of the public and our staff, the EPA Docket Center and
Reading Room are closed to the public, with limited exceptions, to
reduce the risk of transmitting COVID-19. Our Docket Center staff will
continue to provide remote customer service via email, phone, and
webform. We encourage the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email, as there may be a delay in processing
mail and faxes. Hand deliveries and couriers may be received by
scheduled appointment only. For further information on EPA Docket
Center services and the current status, please visit us online at
<a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.

FOR FURTHER INFORMATION CONTACT: For questions about this action,
contact Ms. Karen Marsh, Sector Policies and Programs Division (E143-
05), Office of Air Quality Planning and Standards (OAQPS), U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; telephone number: (919) 541-1065; fax number: (919) 541-0516;
and email address: <a href="/cdn-cgi/l/email-protection#2e434f5c5d4600454f5c4b406e4b5e4f00494158">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION: Participation in virtual public hearing.
Please note that the EPA is deviating from its typical approach for
public hearings because the President has declared a national
emergency. Due to the current Centers for Disease Control and
Prevention (CDC) recommendations, as well as state and local orders for
social distancing to limit the spread of COVID-19, the EPA cannot hold
in-person public meetings at this time.
To request a virtual public hearing, contact the public hearing
team at (888) 372-8699 or by email at <a href="/cdn-cgi/l/email-protection#b2e1e2e2f6c2c7d0dedbd1dad7d3c0dbdcd5f2d7c2d39cd5ddc4">[email&#160;protected]</a>. If
requested, the virtual hearing will be held on October 28, 2021. The
hearing will convene at 9:00 a.m. Eastern Time (ET) and will conclude
at 3:00 p.m. ET. The EPA may close a session 15 minutes after the last
pre-registered speaker has testified if there are no additional
speakers. The EPA will announce further details at <a href="https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair">https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair</a>.
If a public hearing is requested, the EPA will begin pre-
registering speakers for the hearing upon publication of this document
in the Federal Register. To register to speak at the virtual hearing,
please use the online registration form available at <a href="https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair">https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair</a> or contact the public
hearing team at (888) 372-8699 or by email at
<a href="/cdn-cgi/l/email-protection#92c1c2c2d6e2e7f0fefbf1faf7f3e0fbfcf5d2f7e2f3bcf5fde4">[email&#160;protected]</a>. The last day to pre-register to speak at the
hearing will be October 25, 2021. Prior to the hearing, the EPA will
post a general agenda that will list pre-registered speakers in
approximate order at: <a href="https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair">https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair</a>.
The EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearing to run either ahead of schedule or behind schedule.
Each commenter will have 5 minutes to provide oral testimony. The
EPA encourages commenters to provide the EPA with a copy of their oral
testimony electronically (via email) by emailing it to Karen Marsh,
email address:

[[Page 56935]]

<a href="/cdn-cgi/l/email-protection#670a0615140f490c061502092702170649000811">[email&#160;protected]</a>. The EPA also recommends submitting the text of
your oral testimony as written comments to the rulemaking docket.
The EPA may ask clarifying questions during the oral presentations
but will not respond to the presentations at that time. Written
statements and supporting information submitted during the comment
period will be considered with the same weight as oral testimony and
supporting information presented at the public hearing.
Please note that any updates made to any aspect of the hearing will
be posted online at <a href="https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair">https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair</a>. While the EPA expects the hearing to go forward as set forth
above, if requested, please monitor our website or contact the public
hearing team at (888) 372-8699 or by email at <a href="/cdn-cgi/l/email-protection#5a090a0a1e2a2f38363339323f3b2833343d1a3f2a3b743d352c">[email&#160;protected]</a>
to determine if there are any updates. The EPA does not intend to
publish a document in the Federal Register announcing updates.
If you require the services of a translator or a special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team at (888) 372-8699 or by email at
<a href="/cdn-cgi/l/email-protection#47141717033732252b2e242f2226352e29200722372669202831">[email&#160;protected]</a> and describe your needs by October 20, 2021.
The EPA may not be able to arrange accommodations without advance
notice.
Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2021-0299. All documents in the docket are
listed in <a href="http://Regulations.gov">Regulations.gov</a>. Although listed, some information is not
publicly available, e.g., Confidential Business Information (CBI) or
other information whose disclosure is restricted by statute. Certain
other material, such as copyrighted material, is not placed on the
internet and will be publicly available only in hard copy. Publicly
available docket materials are available electronically in
<a href="http://Regulations.gov">Regulations.gov</a>.
Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2021-0299. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit electronically any information you consider to
be CBI or other information whose disclosure is restricted by statue.
This type of information should be submitted by mail as discussed
below.
The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
The <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
<a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA is temporarily suspending its Docket Center and Reading
Room for public visitors to reduce the risk of transmitting COVID-19.
Written comments submitted by mail are temporarily suspended and no
hand deliveries will be accepted. Our Docket Center staff will continue
to provide remote customer service via email, phone, and webform. We
encourage the public to submit comments via <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>. For further information and updates on EPA Docket
Center services, please visit us online at <a href="https://www.epa.gov/dockets">https://www.epa.gov/dockets</a>.
The EPA continues to carefully and continuously monitor information
from the CDC, local area health departments, and our Federal partners
so that we can respond rapidly as conditions change regarding COVID-19.
Submitting CBI. Do not submit information containing CBI to the EPA
through <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
any digital storage media that you mail to the EPA, mark the outside of
the digital storage media as CBI and then identify electronically
within the digital storage media the specific information that is
claimed as CBI. In addition to one complete version of the comments
that includes information claimed as CBI, you must submit a copy of the
comments that does not contain the information claimed as CBI directly
to the public docket through the procedures outlined in Instructions
section above. If you submit any digital storage media that does not
contain CBI, mark the outside of the digital storage media clearly that
it does not contain CBI. Information not marked as CBI will be included
in the public docket and the EPA's electronic public docket without
prior notice. Information marked as CBI will not be disclosed except in
accordance with procedures set forth in 40 Code of Federal Regulations
(CFR) part 2. Send or deliver information identified as CBI only to the
following address: OAQPS Document Control Officer (C404-02), OAQPS,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2021-0299. Note that
written comments containing CBI and submitted by mail may be delayed
and no hand deliveries will be accepted.
Acronyms and abbreviations. We use multiple acronyms and terms in
this document. While this list may not be exhaustive, to ease the
reading of this document and for reference purposes, the EPA defines
the following terms and acronyms here:

AMEL alternative means of emission limitation
AVO audio, visual, or olfactory
AWP Alternative Work Practice
CAA Clean Air Act
CBI Confidential Business Information
CDC Center for Disease Control and Prevention
CDX Central Data Exchange
CFR Code of Federal Regulations
DRF detection response framework
DT detection threshold
DTA average DT value
DTU upper limit of the detection threshold band
eDTA DTA for equivalency
EPA Environmental Protection Agency
EST eastern standard time
FHR Flint Hills Resources
FID flame ionization detector

[[Page 56936]]

HAPs hazardous air pollutants
HC hydrocarbon
LDAR leak detection and repair
LDSN leak detection sensor network
LDSN-DRF leak detection sensor network-detection response framework
OAQPS Office of Air Quality Planning and Standards
OGI optical gas imaging
PID photoionization detector
ppb parts per billion
ppm parts per million
ppmv parts per million by volume
PSL potential source location
QA/QC quality assurance/quality control
VOC volatile organic compounds

Organization of this document. The information in this document is
organized as follows:

I. Statutory and Regulatory Background
A. LDAR Requirements
B. AMEL
II. Request for AMEL
A. FHR West Refinery and East Refinery LDSN-DRF
B. EPA's Analysis of FHR's AMEL Request
III. EPA Framework for Streamlining Evaluation of Future LDSN-DRF
AMEL Requests
IV. AMEL for the Mid-Crude and Meta-Xylene Process Units at the FHR
West Refinery
V. Request for Comments

I. Statutory and Regulatory Background

A. LDAR Requirements

Numerous EPA air pollutant control standards require specific work
practices for LDAR. These work practices require the periodic
inspection of designated components for leaks. The work practice
currently employed requires the use of an instrument which meets the
requirements specified in Method 21 of appendix A-7 of 40 CFR part 60
(hereafter referred to as EPA Method 21). The portable instrument is
used to detect leaks of VOC (including organic HAPs) at the leak
interface of individual components. The work practice requires periodic
monitoring of each component. A ``leak'' is generally defined as an
exceedance of a specified concentration in parts per million (ppm), as
measured with EPA Method 21.\1\
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\1\ As an alternative to this standard work practice, the
Alternative Work Practice (AWP) located at in 40 CFR 60.18 and 40
CFR 63.11 may be used. The AWP employs the use of optical gas
imaging (OGI) for most leak detection surveys, with one annual EPA
Method 21 survey. When using OGI, a ``leak'' is defined as any
emissions imaged by the OGI instrument.
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In their request, FHR cites various LDAR requirements in 40 CFR
parts 60, 61, and 63, which apply to the Mid-Crude and Meta-Xylene
process units at the FHR West Refinery in Corpus Christi, Texas. These
requirements are included in Table 1.\2\
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\2\ EPA prepared Table 1 using information provided in the
request, corrected as appropriate based on its own review of the
regulations. However, the EPA has not independently verified whether
Table 1 includes all of the regulatory requirements with which these
process units must comply.

Table 1--Summary of Applicable LDAR Rules That May Apply to the Process
Units at the FHR Corpus Christi West Refinery
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Emission reduction
Applicable rules with LDAR required and rule Provisions for
requirements citation AMEL
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40 CFR part 60, subpart VV 60.482-2, 60.482-3, 60.484.
(New Source Performance 60.482-7, 60.482-8,
Standards (NSPS VV)). and 60.482-10.
40 CFR part 60, subpart VVa 60.482-2a, 60.482-3a, 60.484a.
(NSPS VVa). 60.482-7a, 60.482-8a,
and 60.482-10a.
40 CFR part 60, subpart GGG 60.482-2, 60.482-3, 60.484.
(NSPS GGG). 60.482-7, 60.482-8,
and 60.482-10, by
reference from 60.592.
40 CFR part 60, subpart GGGa 60.482-2a, 60.482-3a, 60.484a.
(NSPS GGGa). 60.482-7a, 60.482-8a,
and 60.482-10a, by
reference from
60.592a.
40 CFR part 60, subpart QQQ 60.692-2 and 60.692-5. 60.694.
(NSPS QQQ).
40 CFR part 61, subpart FF 61.343, 61.344, 61.353(a); also
(Benzene Waste Operations 61.345, 61,346, see 61.12(d).
NESHAP (BWON)). 61.347, and 61.349.
40 CFR part 63, subpart F 63.102................ 63.162(b) by
(Hazardous Organic NESHAP reference.
(HON)).
40 CFR part 63, subpart H 63.163, 63.164, 63.162(b);
(HON). 63.168, 63.172, 63.177.
63.173, 63.174,
63.175, and 63.178.
40 CFR part 63, subpart CC * FHR notes that the process units are
(Refinery Maximum Achievable complying with the requirements in NSPS
Control Technology (MACT)). VV and VVa, where appropriate to comply
with Refinery MACT.
------------------------------------------------------------------------

The applicable rules shown in Table 1 require periodic monitoring
of each regulated component (e.g., pump, valve, connector, closed vent
system, etc.) with an EPA Method 21 instrument. The frequency of such
monitoring may vary from monthly to every four years depending on the
subpart and the component being monitored. If a leak is found on a
component, the component is tagged and repaired within a specified
time.
The current LDAR work practice involves placing an EPA Method 21
instrument probe at the leak interface (seal) of a component and
registering a VOC concentration (which includes the concentration of
organic HAP).\3\ The EPA has established concentration thresholds which
define a leak. The EPA's leak definition varies from 500 ppm to 10,000
ppm depending on the type of component and the specific subpart. If the
concentration registered by the EPA Method 21 instrument exceeds the
applicable leak definition, then the component must be repaired or
replaced.\4\ For some component types (e.g., components in heavy liquid
service), sensory monitoring or audio, visual, or olfactory (AVO)
monitoring is required. A leak identified with AVO must also be
repaired or replaced within a specified time.
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\3\ See section 8.3.1 of Method 21 of appendix A-7 of 40 CFR
part 60.
\4\ Replacement may include the use of low-emissions valves or
valve packing, where commercially available.
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B. AMEL

The LDAR requirements in each of the subparts listed in Table 1
were established as work practice standards pursuant to CAA sections
111(h)(1) or 112(h)(1). For standards established according to these
provisions, CAA sections 111(h)(3) and 112(h)(3) allow the EPA to
permit the use of an AMEL by a source if, after notice and opportunity
for comment,\5\ it is established to the Administrator's satisfaction
that such an AMEL will

[[Page 56937]]

achieve emissions reductions at least equivalent to the reductions
required under the applicable CAA section 111(h)(1) or 112(h)(1)
standards. As noted in Table 1 of this document, many of the identified
NSPS and NESHAP also include specific regulatory provisions allowing
sources to request an AMEL.
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\5\ CAA section 111(h)(3) requires that the EPA provide an
opportunity for a hearing.
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II. Request for AMEL

A. FHR West Refinery and East Refinery LDSN-DRF

In this section, the EPA is providing a summary of the AMEL request
submitted by FHR. The AMEL that the EPA is proposing is described in
section IV of this preamble. As described in section II.B of this
preamble, the proposed AMEL contains specific changes to the AMEL
request submitted by FHR.
The LDSN-DRF proposed by FHR consists of a continuously operated
LDSN and specialized facility practices and procedures defined in a
DRF. Leak detection sensor nodes are installed to provide coverage of
all LDAR applicable components in the process unit. The short-term
excursion of an individual sensor's output above its baseline level is
called a ``peak'', which represents a potential emission detection. A
web-based analytics platform automatically acquires and analyzes the
real-time data from the sensor nodes, along with wind and facility
information, to issue a potential source location (PSL) notice for this
``peak''. The PSL identifies a location of interest where there is a
possible leak. The size of the PSL can vary depending on the data
collected by the system. The facility then deploys a team to locate and
repair the emission source within the PSL (DRF). Implementation of the
requested LDSN-DRF is intended to replace the periodic monitoring of
all components in a process unit. The LDSN-DRF focuses on the timely
detection of significant emissions and the facility's ability to more
rapidly mitigate leaks. Therefore, FHR seeks an alternative means of
complying with the EPA Method 21 and AVO requirements in the subparts
summarized in Table 1.
In its April 21, 2020, request, FHR indicates that it plans to
install and operate a LDSN in process units subject to LDAR
requirements at its West and East Refineries located in Corpus Christi,
Texas. FHR has the requested LDSN installed in the FHR West Refinery
Mid-Crude and Meta-Xylene process units currently. Those installations
were part of a multi-year Cooperative Research and Development
Agreement (CRADA) between FHR, Molex, and the EPA Office of Research
and Development (ORD) Center for Environmental Measurement and
Modeling.\6\ FHR has requested broad approval of the AMEL for the LDSN-
DRF system for all process units at the FHR West and East Refineries
through this application. FHR states that if broad approval is
provided, they would use a phased approach to install a LDSN in
additional process units across the FHR West and East Refineries. While
FHR is requesting to generally utilize the LDSN-DRF in place of the
required EPA Method 21 and AVO monitoring, FHR does state there may be
process units, or portions of process units, where the current work
practice would continue. According to FHR, these situations could be
based on the following examples: Phased deployment/installation
schedules for sensors, longer distance between LDAR components,
unfavorable cost-benefit analysis, chemical detectability, equipment
location remoteness, or other considerations. FHR's request states that
records will be maintained to clearly demonstrate which portions of the
individual process unit(s) are complying with EPA Method 21, the AWP,
and the LDSN-DRF AMEL.
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\6\ During the CRADA, FHR remained subject to the LDAR
requirements in the applicable subparts, including the EPA Method 21
and AVO monitoring.
---------------------------------------------------------------------------

1. LDSN
As previously discussed, the LDSN consists of leak detection sensor
nodes that are positioned within a facility process unit and
continuously monitor for leaks. The sensors record data approximately
once every second. Any short-term excursion of an individual sensor's
output above its baseline (i.e., peak) represents a potential emission
detection. FHR states in their request that the most critical elements
for demonstrating equivalency with the EPA Method 21 work practice
include sensor selection and sensor node placement.
Sensor selection is based on the responsivity of the sensor to the
chemicals of interest. According to FHR's request, the sensors used in
the FHR LDSN will have response factors of less than or equal to 10 for
the targeted LDAR applicable process streams. The response factor is
the ratio of the known concentration of a compound to the measured
reading of an appropriately calibrated sensor. The higher the response
factor, the lower the sensitivity of the sensor to the chemical.\7\
Following the same response factor threshold required by EPA Method 21,
FHR suggests LDAR applicable process streams and their components with
average response factors greater than 10 for the selected sensor are
not eligible for the LDSN alternative and must instead continue to
comply with the applicable LDAR requirements.
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\7\ If the process stream is a mixture, the response factor is
calculated for the average composition of the process stream.
Average stream compositions may be based on sample data, feed or
product specifications, or process knowledge. Response factors may
be based on published data, test results, or generally accepted
calculation methodologies.
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FHR further states sensor node placement will affect the detection
threshold (DT) of an individual sensor, as in general, leaks that are
closer to a sensor can be detected at smaller emission rates than leaks
that are farther away from the source. The DT is a translation of
concentration measurements from EPA Method 21 to the ability of the
sensor to detect the leak. FHR's request states that sensor node
placement will follow a site assessment, design, optimization, and
installation process such that all components within the LDSN
boundaries that are subject to EPA Method 21 monitoring in the
applicable subparts would have sensor coverage. This also includes
sensor coverage for elevated components and those located on multi-
level structures.
As described in the CRADA report,\8\ the team conducted a series of
tests to establish procedures aimed at optimizing sensor node placement
so that any leak within the LDSN perimeter would be detected by one or
more sensors. Instead of assigning a single method detection limit like
most analytical test methods, the LDSN sensors have a range of
detection thresholds (``DT band'') that can be represented with EPA
Method 21-type ppm values across the sensor coverage radius. As
explained in the CRADA report, the DT band was derived from the
measurement with EPA Method 21 of known mass rate releases of
isobutylene and an array of sensors at different distances and heights.
The DT of an individual sensor is dependent on several factors,
including the size of leak, the distance a leak is from the sensor, the
sensitivity of the detector, the responsiveness of the chemicals of
interest, and the wind conditions. For each sensor, there is a DT band
across the sensor coverage radius. The controlled-release trials
conducted through the CRADA indicate that an isobutylene leak of 1.42
g/hr or greater should be detectable within a 50-foot radius of the
sensor node.\9\
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\8\ See Docket ID No. EPA-HQ-OAR-2021-0299.
\9\ See section 3 of CRADA report located at Docket ID No. EPA-
HQ-OAR-2021-0299.

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[[Page 56938]]

For purposes of modeling the effectiveness of the LDSN-DRF system
compared to the EPA Method 21 program, Molex utilized different
estimates of the center point of the DT band, referred to as average DT
values (DTA), and accounted for distance from the sensor to the leak.
This allowed FHR to determine which DTA is necessary, and at what
distance between sensors, for equivalence to be achieved through the
model. The models for the Meta-Xylene process unit were shown to be
equivalent or better than the EPA Method 21 work practice for all
modeled scenarios, with significant emissions reductions observed when
distance effects were incorporated into the simulations. The Mid-Crude
process unit also demonstrated equivalency for two of the three
emission control scenarios modeled. Through the results of these
simulations, FHR is requesting to use a DTA for equivalency (eDTA) of
11,250 ppm in the Meta-Xylene process unit and 12,500 ppm in the Mid-
Crude process unit at the FHR West Refinery because these values
resulted in equivalent emission reductions from the LDSN-DRF system as
the EPA Method 21 program.\10\ More details of the results of the
simulations can be found in section 4 of the CRADA report.\11\
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\10\ See Table B-3 of the CRADA report located at Docket ID No.
EPA-HQ-OAR-2021-0299. EPA Method 21 monitoring schedule used for
modeling was annual for connectors, monthly for pumps, and quarterly
for valves and other components.
\11\ See section 4 of CRADA report located at Docket ID No. EPA-
HQ-OAR-2021-0299.
---------------------------------------------------------------------------

In addition to the eDTA, FHR's request includes the upper limit of
the detection threshold (DTU), which is the DT value that represents
the smallest leak that could be detected by the sensor network at the
furthest distance away from the sensor. The DTU was not used directly
in the simulations discussed above. Instead, the DTU was calculated
from the eDTA using the following equation: DTA = (DTU+DTL)/2, where
DTL represents the lower value of the DT band. Because the DTL can be
very small, particularly when a sensor is right next to the leak, FHR
and Molex used a conservative estimate of 1.5 times the DTA to
calculate the DTU required to achieve equivalency in total emissions
reductions. FHR indicated this DTU is useful for establishing the
design criteria for the number and placement of sensors and can provide
verification of performance through EPA Method 21 sampling of
components via spot checks.
According to FHR's request, a DTU of 18,000 ppm was used in Molex's
simulations as the DTU required for equivalency and would indicate that
all leaks greater than or equal to 18,000 ppm would trigger a PSL
notification to facility personnel. In addition to the leaks above the
DTU, additional leaks within the DT band would trigger a PSL
notification depending on the distance from a sensor node and
meteorological conditions. As described below, FHR defines sensor
coverage by the overall system eDTA and DTU values listed below, with
individual sensor nodes having a 50-foot radius.
In summary, FHR requests the following eDTA and DTU values for the
FHR West and East Refineries:
<bullet> Meta-Xylene process unit at FHR West Refinery: eDTA =
11,250 ppm; DTU = 18,000 ppm;
<bullet> Mid-Crude process unit at FHR West Refinery: eDTA = 12,500
ppm; DTU = 18,000 ppm; and
<bullet> All other process units at FHR West and East Refineries:
eDTA = 12,000 ppm; DTU = 18,000 ppm.
Changes to process equipment are common within process units. These
may include installation of new equipment, modifications to existing
equipment, or changes in service. These types of changes go through a
change management process that includes an environmental review to
determine potential changes to regulatory applicability and
requirements. FHR states that they will use their existing management
of change processes to review future changes to process equipment and
systems in the process units. This review will include determining if
sensor selection and placement remains adequate, or if updates or
additional sensors are necessary to ensure coverage by the system
maintains the eDTA and DTU values requested. FHR states that this
management of change process is a basic foundational process that is
used throughout the refining, petrochemical, and chemical industries.
2. LDSN Quality Assurance/Quality Control (QA/QC)
In addition to sensor selection and sensor placement, FHR's request
outlines several QA/QC measures specific to the requested LDSN. The
following paragraphs describe these measures as outlined in FHR's
request.
Initial Calibration and Set-up. Prior to deployment, FHR's request
states that each sensor will be calibrated by the manufacturer. Once
installed, each sensor will be tested for responsivity and wireless
communication by challenging it with a standard isobutylene gas or
other appropriate standard. The test results from this initial
calibration are maintained in the software package that FHR plans to
use for the LDSN-DRF system, called mSyte.
Periodic Responsivity Test. In their request, FHR states the
sensitivity of each installed sensor will be measured and recorded at
least quarterly by conducting a ``bump test'' using an isobutylene
standard. According to FHR, a successful bump test is a response of the
sensor that exceeds 50 percent of the nominal value of the standard.
Continuous Sensor Check. FHR proposes to continuously monitor each
sensor for power outage, loss of data transmission, and sensor baseline
levels. The mSyte system will contain the current status of each
sensor, as well as historical data. The mSyte system will send a
notification to facility personnel when any failure or significant
deviation from preset threshold values occurs. FHR states that failed
sensors will be reset, repaired, or replaced.
Meteorological Data. The FHR West and East Refineries have an
existing wind sensor that FHR states will be checked at the same
frequency as the bump tests of the LDSN sensor nodes to ensure the wind
sensor is properly oriented to the north. Wind data collected from this
wind sensor will be compared to data from the meteorological station
located at the FHR refineries at least once per calendar year. The
status of the meteorological station is monitored continuously through
mSyte system for possible loss of communication.
System Operational Availability. As proposed by FHR, the LDSN is a
continuous monitoring system, with each sensor recording approximately
one reading per second. FHR states that these high data collection
rates help optimize the LDSN's detection capability, thus providing
more targeted PSLs and more efficient leak identification during the
DRF inspection process. Further, FHR notes that system maintenance,
sensor checks, sensor failures, or other technical reasons may result
in partial downtime of the LDSN system. FHR's request states the
average operational downtime of the LDSN system will not exceed 10
percent. When issues arise, FHR intends to make repairs to the LDSN
system as soon as practicable.\12\
---------------------------------------------------------------------------

\12\ FHR's request does not specify a clear deadline by when
repairs would be made.
---------------------------------------------------------------------------

Sensor Data. FHR proposes a compliance assurance method that the
EPA or state inspectors could use to verify operation effectiveness of
the LDSN system using random EPA Method 21 sampling. FHR's proposed
random sampling would indicate a

[[Page 56939]]

compliance issue if a statistically significant number of EPA Method 21
readings are greater than 1.2 times the DTU on LDAR applicable
components within the LDSN boundary where active PSL leak
investigations are not pending or ongoing. FHR suggests the factor of
1.2 times the DTU represents the variability that occurs in the EPA
Method 21 measurement process.
3. DRF
The LDSN system automatically detects, categorizes, and
approximates the location of emissions in the monitored process unit
based on sensor location, sensor output and meteorological
measurements. The LDSN notifies selected facility personnel of detected
emission anomalies so that appropriate action can be taken under the
DRF. This section describes FHR's requested DRF.
The DRF includes the work practices that are employed to identify
the specific source of emissions and to make appropriate repairs. For
every notification from the LDSN, a PSL with a discrete serialized
identification number is provided to facility operators. This PSL is a
visual representation of the area in which there is high probability
that fugitive emissions are present, thus providing a targeted area for
leak investigation.
The purpose of the PSL investigation is to identify the source of
emissions needing repairs. Investigations are initiated within three
days of a PSL notification. FHR intends to utilize various emissions
screening methods in order to locate the emissions source(s). This may
include handheld portable equipment such as VOC analyzers, optical gas
imaging (OGI), or other appropriate detectors for the chemicals of
interest. Once identified, EPA Method 21 is performed on the emissions
source to document the maximum concentration reading, and repairs
begin. Each component identified with a maximum concentration reading
greater than the leak definitions specified in Table 2 is considered a
leak needing repair. The leak definitions in the table follow those
defined in the applicable LDAR regulations for the process units at the
FHR West and East Refineries. It is important to note that FHR's
request does not include conducting EPA Method 21 on every LDAR-
applicable component in the PSL during the investigation. Instead, FHR
proposes that when at least one component has been identified with a
maximum concentration greater than or equal to 3,000 ppm, this
component is presumed to be the emissions source and no further
investigation is required. In this case, once the leak has been
successfully repaired, the PSL is closed.
In addition, some PSL notifications are triggered by multiple
smaller leaks that are close together. To account for this potential
leak cluster effect, FHR proposes that when at least three components
have been identified with a maximum concentration less than 3,000 ppm
but greater than the applicable leak definition as specified in Table
2, that collection of components is presumed to be the emissions source
and no further investigation is required. Once those smaller leaks are
successfully repaired, the PSL is closed. This threshold of 3,000 ppm
was chosen by FHR based on EPA ORD's model that took into consideration
the occurrence of small leaks in a cluster generating a PSL. In EPA
ORD's model, a single leak greater than or equal to 3,000 ppm or three
leaks with concentrations less than 3,000 ppm was found equivalent in
95 percent of the model simulations, and thus equivalent to the current
work practice.
Where the emission source is not identified after 30 minutes of
active searching during the initial PSL investigation, FHR proposes to
stop the investigation for seven days. During these seven days, the
LDSN will continue to collect data for analysis, which helps refine the
PSL. Within seven days of the initial investigation, a second
investigation will be conducted. If this second investigation does not
identify the emission source, and the PSL detection level increases to
twice the initial level, a PSL update notification is sent using the
increased detection level, and a new investigation is started within
three days. This step is repeated each time the leak is not located.
FHR further proposes that if the emission source has not been
identified and the PSL has not updated within 14 days or more, the PSL
is automatically closed. Finally, if after 90 days the emission source
is not identified and the PSL has not updated, FHR states that one
final screening will be conducted and the PSL will be closed with an
indication that no leak source was found.
In summary, FHR proposes that a PSL is closed when one of the
following criteria is met:
<bullet> One or more leaks >=3,000 ppm is found and repaired;
<bullet> Three or more leaks <3,000 ppm are found and repaired;
<bullet> Malfunction, startup, or shutdown activity or other
authorized emissions are identified and documented;
<bullet> Components on delay of repair have been repaired and
monitored to verify repair;
<bullet> A leak source has not been identified and the PSL has not
updated within 14 days or more; or
<bullet> A leak source has not been identified after multiple
investigations and it has been 90 days without the unidentified
potential leak source worsening (i.e., PSL detection level increasing
to twice the previous detection level).
After a PSL is closed, FHR's request states that if the LSDN shows
new positive detections above the threshold, a new PSL is generated and
notification is issued. This starts a new DRF investigation process.
FHR's request states that the applicable leak repair requirements
in 40 CFR part 60, subparts VV, VVa, GGG, GGGa, and QQQ, 40 CFR part
61, subpart FF, and 40 CFR part 63, subparts H and CC would remain in
effect for components subject to LDAR (i.e., pumps, valves, connectors,
and agitators). These requirements include an initial repair attempt
within five days of leak confirmation with EPA Method 21 maximum
concentration reading above the applicable leak definition, and final
successful repair within 15 days of leak detection. Additionally, delay
of repair, as allowed in the applicable subparts, would still apply to
leaks detected with the LDSN-DRF system.
Table 2 summarizes the applicable leak definitions for various
component types, including non-LDAR components that are identified as
leaking by the LDSN-DRF system.

Table 2--Applicable Leak Definitions for Components in the LDSN-DRF System
--------------------------------------------------------------------------------------------------------------------------------------------------------
Leak source Initial repair Final effective
LDSN leak source classification component class LDSN leak definition attempt repair Final repair confirmation
--------------------------------------------------------------------------------------------------------------------------------------------------------
LDAR Component Leak--``LDAR''... Agitator--FF....... 500 ppm................. 5 days............. 15 days............ <500 ppm.

[[Page 56940]]

LDAR Component Leak--``LDAR''... Agitator--VV....... 2,000 ppm............... 5 days............. 15 days............ <2,000 ppm.
LDAR Component Leak--``LDAR''... Agitator--HON...... 10,000 ppm.............. 5 days............. 15 days............ <10,000 ppm.
LDAR Component Leak--``LDAR''... Compressor--HON.... 500 ppm................. 5 days............. 15 days............ <500 ppm.
LDAR Component Leak--``LDAR''... Compressor--non HON 2,000 ppm............... 5 days............. 15 days............ <2,000 ppm.
LDAR Component Leak--``LDAR''... Compressor in AVO..................... 5 days............. 15 days............ No AVO indication.
Hydrogen Service.
LDAR Component Leak--``LDAR''... Connector.......... 500 ppm................. 5 days............. 15 days............ <500 ppm.
LDAR Component Leak--``LDAR''... Pump--with permit 500 ppm................. 5 days............. 15 days............ <500 ppm.
specifying 500 ppm.
LDAR Component Leak--``LDAR''... Pump--HON.......... 1,000 ppm............... 5 days............. 15 days............ <1,000 ppm.
LDAR Component Leak--``LDAR''... Pump--VV........... 2,000 ppm............... 5 days............. 15 days............ <2,000 ppm.
LDAR Component Leak--``LDAR''... Valve.............. 500 ppm................. 5 days............. 15 days............ <500 ppm.
Non-LDAR Component Leak-- Agitator--Hydrocarb 10,000 ppm.............. Follow emission event reporting and <10,000 ppm.
``Emission Event''. on (HC) but non repair guidelines
LDAR.
Non-LDAR Component Leak-- Compressor--HC but 2,000 ppm............... Follow emission event reporting and <2,000 ppm.
``Emission Event''. non LDAR. repair guidelines
Non-LDAR Component Leak-- Connector--HC but 500 ppm................. Follow emission event reporting and <500 ppm.
``Emission Event''. non LDAR. repair guidelines
Non-LDAR Component Leak-- Pump--HC but non 2,000 ppm............... Follow emission event reporting and <2,000 ppm.
``Emission Event''. LDAR. repair guidelines
Non-LDAR Component Leak-- Relief Device--HC 500 ppm................. Follow emission event reporting and <500 ppm.
``Emission Event''. but non LDAR. repair guidelines
Non-LDAR Component Leak-- Valve--HC but non 500 ppm................. Follow emission event reporting and <500 ppm.
``Emission Event''. LDAR. repair guidelines
Non-LDAR Component Leak-- Other.............. 500 ppm................. Follow emission event reporting and <500 ppm.
``Emission Event''. repair guidelines
``Authorized Emission'' \1\..... Authorized Emission N/A..................... N/A................ N/A................ N/A.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Authorized emissions may include emissions from a stack or otherwise allowed. These emissions are not considered equipment leaks for purposes of
this AMEL.

B. EPA's Analysis of FHR's AMEL Request

This section addresses specific aspects of FHR's request.
1. Equivalence Demonstration
FHR submitted both a pilot study and an analysis of the LDSN system
requirements that would achieve equivalent emissions reductions to
compliance with the currently required leak detection program at the
two process units in question.\13\ This submission includes (1)
simulation modeling that was used to determine the level of performance
of the LDSN that is necessary to achieve equivalent emission reductions
and (2) results from a pilot study conducted in the specific process
units for which this AMEL is requested. Based on the EPA's analysis of
the simulation modeling results, and the pilot study results, plus the
EPA's comparison of the proposed work practice standards for the AMEL
in section IV applied to the data collected in the pilot study, the EPA
finds that this proposed AMEL would achieve at least equivalent
emission reductions as the EPA Method 21 requirements to which these
process units are subject. Our analysis of the submission is discussed
below.
---------------------------------------------------------------------------

\13\ As part of EPA's review of this modeling, we considered the
closure of the Consent Order for the Corpus Christi Refinery and
reviewed records of the LDAR program during the 2019 calendar year
and did not identify issues with the program that would affect the
basis for the equivalency.
---------------------------------------------------------------------------

a. Modeling demonstration. Molex and EPA ORD \14\ used historical
leak data and a Monte-Carlo simulation method to generate a profile of
leak events, and then calculated mass emissions under two scenarios:
(1) The applicable EPA Method 21 requirements and (2) the LDSN with
certain assumptions about its performance. The Monte-Carlo analysis
indicates that the LDSN, when operated with specified performance
criteria, is at least equivalent to the current EPA Method 21 work
practice. However, there are several assumptions that could affect this
conclusion. For example, the simulation method did not account for
variability in the LDSN with respect to certain data quality allowances
such as downtime. However, as discussed further in section II.B.3 of
this preamble, the EPA did analyze the effects of downtime on the
equivalence modeling.
---------------------------------------------------------------------------

\14\ See section 4 of the CRADA report located at Docket ID No.
EPA-HQ-OAR-2021-0299.
---------------------------------------------------------------------------

As stated in the CRADA report, the equivalency modeling was limited
to the process units included in the CRADA pilot study (Meta-Xylene and
Mid-Crude) and was not designed to provide conclusions about other
potential LDSN installations. Overall, the modeling demonstrates that
the LDSN-DRF system may take time to reach a level of steady-state
control, though this is also common for a LDAR program based on EPA
Method 21. Therefore, the EPA generally accepts the analysis as valid
but solicits comments on this approach.
b. Pilot study results. FHR conducted multi-month pilot studies of
the LDSN-DRF in the Mid-Crude and Meta-Xylene process units. The pilot
study started in

[[Page 56941]]

May 2019 for the Meta-Xylene unit and in July 2019 for the Mid-Crude
unit. The pilot studies ended in November 2019 for both units. FHR
deployed fixed-place networks of 10.6 electron volt photoionization
detectors for the pilot studies; the network consisted of 38 sensor
nodes for the Mid-Crude unit and 10 sensor nodes for the Meta-Xylene
unit. During the pilot studies, LDAR inspections with EPA Method 21
continued to be conducted at the required frequency.
To evaluate the results of the pilot study, the EPA examined
inspection information extracted from FHR's leak database to compare
leaks identified with the LDSN-DRF and those identified with the
required EPA Method 21 monitoring. First, we removed components outside
the area of the LDSN, as well as components that will remain under the
standard work practice, as these components are not relevant for
demonstrating the efficacy of the LDSN-DRF in practice. A summary of
the EPA's results of this comparison is included in Table 3.

Table 3--Comparison of EPA Method 21 and LDSN-DRF Results
----------------------------------------------------------------------------------------------------------------
Mid-Crude Meta-Xylene
---------------------------------------------------------------
EPA Method 21 LDSN-DRF EPA Method 21 LDSN-DRF
----------------------------------------------------------------------------------------------------------------
Number of leaks................................. 23 33 58 64
Smallest leak, ppm.............................. 540 582 500 564
Largest leak, ppm............................... 81,568 100,000 100,000 100,000
Mean of leaks, ppm.............................. 13,036 21,904 4,415 14,052
----------------------------------------------------------------------------------------------------------------

For the Mid-Crude process unit, of the 33 leaks found by LDSN-DRF,
11 were for components that are subject to AVO inspection, two were
components added to the leak database, and six were due for an
inspection, as the unit had been down prior to installation of the
LDSN. For the remaining 14 components, the LDSN found leaks an average
of 240 days sooner than the next scheduled inspection, with a range of
14 to 359 days. For the Meta-Xylene process unit, of the 64 leaks found
by LDSN, 10 were for components that are either subject to AVO
inspection, one was a component added to the leak database, one was on
delay of repair, and one was due for an inspection. Additionally, five
of the PSLs generated at the Meta-Xylene process unit were for new
leaks on components where leaks were previously discovered and fixed
because of the LDSN-DRF. Because both leaks occurred prior to when the
next scheduled EPA Method 21 inspection would have occurred, the
analysis only considered the original leak found by the LDSN. For the
remaining 46 components, the LDSN-DRF found leaks an average of 127
days sooner than the next required EPA Method 21 inspection, with a
range of 13 to 360 days.
To estimate the emissions from component leaks not captured by the
LDSN-DRF, we assumed that the component had been leaking for half of
the time from the previously passed EPA Method 21 inspection, unless
that timeframe exceeded the start date of the pilot study; in that
case, the component was assumed to be leaking from the time the pilot
study started until the leak was found. The emissions were then
calculated using the correlation equations in EPA's Protocol for
Equipment Leak Emission Estimates.\15\ Petroleum industry equations
were used for the Mid-Crude process unit and Synthetic Organic Chemical
Manufacturing Industry (SOCMI) equations were used for the Meta-Xylene
process unit.\16\ The emissions from the leaks not found by the LDSN
totaled 338 kg for the Meta-Xylene process unit and 39 kg for the Mid-
Crude process unit.\17\ To estimate the emissions reductions achieved
by the LDSN-DRF, we calculated the number of days from when the
component was fixed to the next required EPA Method 21 inspection. We
then calculated the emissions using the correlation equations mentioned
above. The estimated emissions reductions totaled 1,977 kg for the
Meta-Xylene process unit and 43 kg for the Mid-Crude process unit.
Additional emissions reductions would likely be achieved by finding and
fixing leaks from the components listed as AVO. However, because these
components are not surveyed on a regular frequency, it is difficult to
quantify how long the leak might have occurred without the LDSN.
---------------------------------------------------------------------------

\15\ Available at: <a href="https://www.epa.gov/sites/production/files/2020-09/documents/protocol_for_equipment_leak_emission_estimates.pdf">https://www.epa.gov/sites/production/files/2020-09/documents/protocol_for_equipment_leak_emission_estimates.pdf</a>
\16\ Pegged emission rate leak factors were used for leaks at
and above 100,000 ppm.
\17\ Three components in the EPA Method 21 inspection set were
leaking at the time the pilot study began. These may not have been
picked up by the LDSN because the system may have already marked
them as known leakers. However, we have included them in the
emissions summary to be conservative.
---------------------------------------------------------------------------

In addition to this direct comparison of LDAR components, the LDSN
found two leaks in the Meta-Xylene process unit and 20 leaks in the
Mid-Crude process unit that were outside of the designated covered area
or outside of the LDAR program. Because many of these leaks were not
from traditional LDAR components, it is difficult to quantify the
emissions reductions from the LDSN-DRF. However, 11 of the leaks found
at the Mid-Crude process unit were for traditional LDAR components that
will not be covered by the LDSN-DRF. For these 11 components alone, we
estimated an emissions reduction of 278 kg.
During the pilot studies, several leaks above 18,000 ppm (the DTU)
were identified with EPA Method 21 monitoring that were not identified
with the LDSN-DRF (six leaks at the Mid-Crude process unit and three
leaks at the Meta-Xylene process unit). Based on these results, FHR
determined that six new sensors were needed in the Mid-Crude process
unit in order to achieve the level of performance required for
equivalence. For the Meta-Xylene process unit, FHR states they believe
that the three leaks above the DTU identified with EPA Method 21
monitoring were included within active PSLs with investigations that
were not yet completed. They used this information to improve their PSL
tracking mechanism. It is not clear to the EPA that additional sensors
are not warranted in the process unit. However, the compliance
assurance measures that we are proposing in the AMEL should address any
continued issues with the design of the LDSN-DRF system for these
process units. Further, FHR will conduct an analysis to ensure the
system meets the DTU requirements in Section IV.A.
2. Scope of AMEL Approval
Process units covered by AMEL. FHR has requested approval for the
use of the LDSN-DRF in all process units located

[[Page 56942]]

at the FHR West and East Refineries in Corpus Christi, Texas. However,
the data provided for the equivalency demonstration is limited to the
Mid-Crude and Meta-Xylene process units at the FHR West Refinery. As a
result, the EPA is unable to evaluate the appropriate DTA and DTU
values for other process units located at these refineries through this
request. Therefore, the evaluation of the AMEL and subsequent proposed
approval is limited to the implementation of the LDSN-DRF in the Mid-
Crude and Meta-Xylene process units at the FHR West Refinery.
Standards covered by AMEL. As summarized in Table 1, FHR has
requested approval to implement the LDSN-DRF as an alternative to EPA
Method 21 monitoring, AVO monitoring, and monitoring to demonstrate
that closed vent systems and equipment designated with no detectable
emissions are not leaking. However, FHR also notes that the equivalency
simulations do not include leaks identified through AVO monitoring. It
is not possible to determine if the LDSN-DRF will result in emission
reductions at least equivalent to the AVO monitoring requirements of
the applicable subparts. Therefore, the AMEL specified in Section III
does not allow the use of the LDSN-DRF as an alternative to the
required AVO monitoring.
In the applicable subparts, annual monitoring of closed vent
systems with EPA Method 21 is required. These vent systems are closed
because they are used to route emissions to control devices. Closed
vent systems are subject to a leak definition of 500 ppm with EPA
Method 21. Similarly, some components are designated for no detectable
emissions, which is demonstrated by an EPA Method 21 instrument reading
of less than 500 ppm. These are emissions standards for both types of
equipment and leaks are not supposed to occur. Emissions standards are
not eligible for AMEL. Therefore, the AMEL specified in Section IV does
not allow the use of the LDSN-DRF as an alternative to the EPA Method
21 monitoring requirements for closed vent systems and components
designated for no detectable emissions, including pressure relief
devices.
3. LDSN Specifications
Operational Downtime. As noted in FHR's AMEL application, high data
collection rates are necessary to meet the DTU design criteria.
Nevertheless, system maintenance, sensor checks, sensor failures, or
other technical reasons may result in partial downtime of the LDSN
system. FHR's request included an average operational downtime of the
LDSN system of no more than 10 percent. FHR further proposed an average
operational downtime for each sensor of no more than 30 percent. This
large amount of downtime for individual sensors was due in part to how
FHR defined operational downtime, which included periods of data deemed
invalid. FHR proposed that half of the time between a failed bump test
and the previously passed bump test would be considered invalid data.
We agree that a high data collection rate of all sensors is necessary
for the LDSN to operate in a manner that provides equivalent emissions
reductions. While we recognize that some downtime of the sensors is
inevitable, a downtime of 30% for each sensor does not provide a high
data collection rate. Our understanding is that during the downtime of
an individual sensor, adjacent sensors will be able to detect larger
mass leaks but will not detect leaks at the detection level. Taking
into consideration that a detection is based on a 72-hour period and
that the sensors work together to determine where leaks may be
occuring, adverse effects from short duration downtime periods of one
sensor are not anticipated. Therefore, the AMEL specified in section IV
of this preamble applies a narrower definition for sensor operation
downtime and limits the downtime of each individual sensor to no more
than 10 percent on a rolling annual basis, determined each month. The
AMEL defines operational downtime as periods when a sensor does not
provide data or is out of control.
As part of our review of the AMEL request, the EPA performed
modeling to determine the effect of downtime on the equivalence of the
LDSN-DRF system. For this analysis, the EPA used the model that was
developed by EPA ORD and modeled a scenario in which the detection of
any leaks was delayed over random periods of time by up to 36 days per
year. This is equivalent to a 10 percent network-wide downtime, where
all sensors are down at the same time continuously for 10 percent of
the year, which is the worst-case scenario for the downtime allowed by
the AMEL specified in Section IV. The EPA ORD model was modified in the
following ways:
<bullet> For each of the 1,000 Monte Carlo Simulations, a random
36-day period of downtime was generated for each of the three years
covered in the model.
<bullet> For each simulation, if a leak detection would have been
made by the LDSN during the downtime period, the date of detection was
changed to the day after the downtime ended.
<bullet> New total emissions were calculated for each detection
method and simulation.
Table 4 summarizes the results of the model with and without
downtime. The numbers represent the percentage of Monte Carlo
simulations where emissions were lower based on the various sensor
network detection scenarios as compared to two different Method 21
scenarios. ``DTA'' represents the detection threshold average scenario,
``DT_'' represents the detection threshold scenario, and ``DTC''
represents the detection threshold cluster scenario. The assumptions
for these scenarios are described in Appendix E of the CRADA report
located at Docket ID No. EPA-HQ-OAR-2021-0299. For purposes of Table 4,
``M21'' represents running EPA Method 21 on all components, including
connectors, while ``C21'' represents excluding connectors. Including
downtime reduced the percentage of scenarios where the sensor network
outperformed EPA Method 21 by at most 2 percent.\18\
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\18\ See Docket ID No. EPA-HQ-OAR-2021-0299 for additional
information on the modeling performed by the EPA.

Table 4--Results of LDSN Downtime Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------------
Standard model
Model with downtime
--------------------------------------------------------------------------------------------------------------------------------------------------------
Detection....................... DTA............... DT_............... DTC............... DTA............... DT_............... DTC
M21............................. 20.5.............. 72.9.............. 94.3.............. 19.4.............. 71.2.............. 92
C21............................. 94.4.............. 99.9.............. 100............... 93.2.............. 99.6.............. 100
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 56943]]

Sensor Detection Criteria. The requested AMEL did not specify a
detection criterion for the individual sensors. The proposed AMEL
specified in Section IV of this notice requires the sensors in the LDSN
to be capable of maintaining a detection floor of less than 10 part per
billion (ppb) by volume isobutylene equivalent (ppbe) on a rolling 10-
minute average. The detection floor is defined as three times the local
standard deviation. To determine the detection floor, the previous 10
minutes of data is used, excluding data when transient peaks above the
noise baseline indicate emission detections. The detection floor must
be adjusted for the system response to the most recent bump test.
Signals above the detection floor are considered emission detections.
Section IV.A(a)(2) includes an equation for determining the detection
floor.
Response Factor. FHR requested a response factor threshold of 10 or
less for process streams covered by the AMEL. This request was based on
the threshold required by EPA Method 21. However, there is no data that
supports that the system would perform adequately if the process
streams had a response factor of 10. The CRADA report discusses the
importance of response factor and notes that ethylene, which has a
response factor of approximately 10 for these sensors, has a weak
response and is difficult to detect.\19\ According the FHR's
application, the streams in the Meta-Xylene process unit have an
average response factor of 0.8. The streams in the Mid-Crude process
unit have response factors that range from 0.7-3.0. The pilot study and
equivalence modeling were conducted using these response factors.
Therefore, the AMEL in Section IV of this notice limits the process
streams covered by the LDSN to a response factor of three.
---------------------------------------------------------------------------

\19\ See section 3.2 of the CRADA report located at Docket ID
No. EPA-HQ-OAR-2021-0299.
---------------------------------------------------------------------------

4. DRF Specifications
Screening method. The proposed AMEL does not specify an individual
screening method (e.g., OGI) that must be used during the PSL
investigations. The intent of these investigations is to quickly
identify the potential emissions source(s) that triggered the PSL. FHR
has requested discretion to use a screening method that best reflects
their knowledge of the emission sources within the PSL. In supporting
information, FHR provides the following examples of screening
technologies that will be utilized for the PSL investigations:
<bullet> Photoionization detector (PID): A portable VOC gas
detector capable of detecting most VOC gases. This device must have a
digital readout with a resolution of 10 ppb or higher, and a response
time T90 <30 seconds. It must be certified for use in hazardous
locations. This portable instrument is used for fast scanning the area
to narrow down the search.
<bullet> Flame ionization detector (FID) or PID: An FID or PID
compliant with EPA Method 21. This tool is employed in the DRF to
pinpoint the leak source and record the leak concentration before and
after repair.
<bullet> OGI: This tool is used to identify large leaks.
FHR utilized these technologies during the pilot study to identify
potential emission sources. The EPA agrees that discretion should be
afforded when choosing a screening technology, provided the
technologies are capable of identifying VOC gases, and we find these
three screening technologies are appropriate for use.
Initial screening investigations. FHR has requested that the
initial screening investigations be conducted for 30 minutes; if after
30 minutes no potential leak sources are identified, FHR requests to
stop the investigation and wait seven days before conducting another
screening investigation. During the pilot study, FHR noted that most
leak sources were identified within this 30-minute screening window,
and the EPA agrees that this is a sufficient amount of time to identify
most leaks that would trigger a PSL. Further, the LDSN continues to
collect information, which allows the system to better identify the
area where the emissions are located, thus making subsequent screening
investigations more likely to result in leak source identification. To
ensure the efficacy of the initial screening investigations, the EPA is
proposing a requirement to maintain a record of the latitude and
longitude coordinates in decimal degrees to an accuracy and precision
of five decimals of a degree using the North American Datum of 1983 for
the path taken during the screening investigation, when no leak sources
are identified during the 30-minute screening investigation.
Additionally, the record would include the date and time stamp of the
start and end of the investigation. While the EPA expects that leak
sources will be easily identified during the screening investigation,
this record will provide valuable information to the EPA that screening
was conducted in a manner to maximize identification of the leak
source.
Closure of a PSL after 90 days. FHR states that a PSL can be closed
if a leak source has not been identified after multiple investigations
and it has been 90 days without the unidentified potential leak source
worsening (i.e., PSL detection level increasing to twice the previous
detection level). FHR further states that one final screening would
occur before closing the PSL. If a leak is present and not addressed
before closing the PSL, a new PSL notification would be generated by
the LDSN. While it is expected that this is a rare occurrence, and FHR
did not experience such a situation during the pilot study period, the
EPA is concerned about leaks that would go unrepaired. In the LDAR
requirements of the applicable subparts, all LDAR-applicable components
are monitored on average (1) monthly for pumps, (2) quarterly for
valves, and (3) annually for other components types. Noting these
frequencies, the EPA finds that it is important to monitor all LDAR
components in a PSL with EPA Method 21 if no emission source has been
identified within 90 days of the initial notification. All components
with instrument readings above the applicable leak definitions
specified in Table 2 must be repaired before closing the PSL.
Repair of non-LDAR applicable components. FHR's request states that
one advantage to the LDSN-DRF is that leaks from components that are
not traditionally subject to LDAR can be detected and repaired.
However, FHR does not propose a specific repair deadline by which
repairs will be completed for these non-LDAR applicable components.
Given that the purpose of LDAR is to both detect and repair leaks, the
EPA finds that setting a deadline by which repairs must be made is
necessary to reap the benefit of reducing emissions in a timely manner
and ensure the LSDN is not confounded by these leaks. Additionally,
sources have a general duty to operate equipment in a manner to
minimize emissions. Therefore, we are including a requirement that
leaks identified on non-LDAR applicable components must be completed
and verified within 30 days of identification of the leak.
5. Additional Annual Compliance Demonstration
In their request, FHR stated that random EPA Method 21 sampling
could be utilized to verify the effectiveness of the LDSN, including
verification that the system is operating with a DTU of 18,000 ppm.
This verification would be demonstrated, according to FHR, by the lack
of a statistically significant number

[[Page 56944]]

of EPA Method 21 readings greater than 1.2 times the DTU on applicable
LDAR components within the boundary of the LDSN, with the factor of 1.2
representing the variability that occurs with the implementation of EPA
Method 21.
The EPA agrees this approach would provide an additional backstop
to verifying the efficacy of the LDSN, and as such, has incorporated an
additional annual compliance demonstration into the proposed AMEL in
section IV.E. The EPA has determined that it is appropriate for FHR to
demonstrate the LDSN is operating as expected through this additional
annual demonstration because the pilot study had identified missed
leaks that were above the DTU, resulting in the need for additional
sensor nodes. However, we are also confident that there will be a point
where the LDSN is operating as required in this proposed AMEL such that
this additional requirement can sunset.
Specifically, the EPA is proposing to require annual EPA Method 21
on all pumps located in the Meta-Xylene and Mid-Crude process units
subject to this AMEL. Additionally, the EPA is proposing to require
annual EPA Method 21 on a random sample of valves within the
verification zone (defined as the zone that is 40 to 50 feet from an
individual sensor node) such that at least 20 percent of the total
population of valves in the process unit are monitored. If any leaks
are identified above 18,000 ppm, except those in an active PSL, the
LDSN would be considered out of compliance with the AMEL and corrective
actions, including submission of a plan to get back into compliance,
would be required. The EPA does propose to sunset this requirement
after FHR demonstrates for two consecutive calendar years that no leaks
are identified above 18,000 ppm with this annual EPA Method 21
demonstration. Further details are specified in section IV.E of the
proposed AMEL.

III. EPA Framework for Streamlining Evaluation of Future LDSN-DRF AMEL
Requests

The EPA is also soliciting comment on a general framework sources
may use in the future to submit an AMEL request to the EPA for the use
of a LDSN-DRF to comply with the LDAR requirements under 40 CFR parts
60, 61, and 63. A similar framework approach was outlined for
multipoint ground flares once we started receiving multiple AMEL
requests.\20\ In recent years, various stakeholder groups \21\ have
worked to identify general frameworks to aid in an evaluation of
equivalency for future alternatives for fugitive emissions detection.
---------------------------------------------------------------------------

\20\ 81 FR 23480 (April 21, 2016), pp. 23487-88.
\21\ Fox, T.A., Ravikumar, A.P., Hugenholtz, C.H., Zimmerle, D.,
Barchyn, T.E., Johnson, M.R., Lyon, D. and Taylor, T., 2019. A
methane emissions reduction equivalence framework for alternative
leak detection and repair programs. Elem Sci Anth, 7(1), p.30. DOI:
<a href="http://doi.org/10.1525/elementa.369">http://doi.org/10.1525/elementa.369</a>
---------------------------------------------------------------------------

The EPA is proposing the following framework that applicants may
use to streamline requests and our review of those requests. This
proposed framework will ensure the application provides the information
necessary for the EPA to review the request and determine if an
equivalent means of emissions limitation is demonstrated by the
alternative requested. Determination of equivalence to the applicable
LDAR requirements will be evaluated by the following guidelines. The
applicant must provide information that is sufficient for demonstrating
the AMEL achieves emission reductions that are at least equivalent to
the emission reductions that would be achieved by complying with the
relevant standards. At a minimum, the application must include the
following information:
(1) Site-specific information related to all process unit(s)
included in the alternative request.
(a) Site name and location and applicable process units.
(b) Detailed list or table of applicable regulatory subparts for
each included process unit, the citations within each subpart that will
be replaced or changed by the AMEL and, if changed, how it will be
changed, and the authority that allows for use of an AMEL.
(c) Details of the specific equipment or components that will be
inspected and repaired as part of the AMEL and whether any equipment
within the process unit will not be covered by the AMEL.
(d) A diagram showing the location of each sensor in the process
unit and the minimum spacing that achieves equivalence (i.e., the
furthest distance a component can be located from a sensor while
demonstrating equivalence), taking into consideration multi-level and
elevated components.
(e) Information on how management of change (MOC) will be
addressed. At a minimum, the MOC must include a determination of
whether the changes are within the LDSN coverage area (i.e., within the
specified radius of coverage for each individual sensor, including
coverage based on elevation) or if changes will result in components
added to an applicable EPA Method 21 work practice where the LDSN would
not provide coverage. The MOC must also address updates to the diagrams
of each sensor or the list of equipment identification numbers, as
applicable.
(2) Identification of monitoring techniques used for both the LSDN
and DRF.
(a) Identification of the sensors that will be used to detect and
locate leaks, including the sensor measurement principle, type, and
manufacturer.
(b) Data recording frequency, the minimum data availability for the
system and for each sensor, and the process for dealing with periods
where data is not available.
(c) Initial and ongoing QA/QC measures and the timeframes for
conducting such measures.
(d) Restrictions on where the sensors cannot be used.
(e) How meteorological data will be collected, the specific data
that will be collected, and how it will be paired with the sensor data.
(3) Defined work practice.
(a) Description of what triggers action, description of the
action(s) that is triggered, and the timeline for performing the
action(s).
(b) Definition for when a leak requires repair.
(c) Identification of repair deadlines, including verification of
repair.
(d) Description for how repairs will be verified.
(e) Actions that will be taken if an alert is issued by the system,
but a leak cannot be found.
(f) Initial and continuous compliance procedures, including
recordkeeping and reporting, if the compliance procedures are different
than those specified in the applicable subpart(s).
(g) Compliance assurance procedures to ensure the LSDN is operating
as designed and corrective actions (including timeframes) in response
to findings.
(4) Demonstration of Equivalency
(a) Demonstration of the emission reduction achieved by the
alternative work practice including restrictions and downtime.
Restrictions should include any conditions which are not demonstrated
as equivalent in the request, such as replacement of AVO monitoring or
no detectable emissions standards.
(b) Determination of equivalency between the standard work practice
and the alternative requested, which may include modeling results.
(c) Results of the pilot study conducted for each unit.
(i) For each PSL generated, the date for each notice, the
identified emission source, the date the associated emission

[[Page 56945]]

source was found for each PSL, the date the emission source was
repaired, the EPA Method 21 reading associated with the emission
source, and the date of the last required and next required EPA Method
21 inspection for the emission source (or identification of the source
as not subject to inspection).
(ii) For each leak found with an EPA Method 21 inspection that was
not found by the LDSN-DRF during the pilot study, the date the leak was
found, the EPA Method 21 reading for the leak, the date the leak was
repaired, and the inspection frequency of the component.
(iii) The results of all EPA Method 21 inspections for the unit
during the pilot study.
The EPA solicits comment on all aspects of this framework. We
anticipate this framework would enable the Agency to evaluate future
AMEL requests for LDSN-DRF installations in a more expeditious
timeframe because we anticipate that the information required by the
framework would provide us with sufficient information to evaluate
future AMEL requests on a case-by-case basis. We note that all aspects
of future AMEL requests will still be subject to the notice and comment
process.

IV. AMEL for the Mid-Crude and Meta-Xylene Process Units at the FHR
West Refinery

Based on the EPA's review of the AMEL request from FHR, we are
seeking the public's input on the alternative LDAR work practice
proposed for the LDSN-DRF system for the Mid-Crude and Meta-Xylene
process units located at FHR's West Refinery in Corpus Christi, Texas.
Information provided in the AMEL request, and our evaluation of such
information, indicate that the following work practice requirements are
necessary for the proposed LDSN-DRF system to achieve emissions
reductions at least equivalent to the emissions reductions achieved by
the portion of the current LDAR work practice specified in Table 5. If
approved, this AMEL would replace the portions of the work practice
standards outlined in Table 5. Should the work practice standards be
revised, this AMEL would need to be reviewed to determine if it is
still equivalent. If in the future the work practice standard is
replaced by an emissions standard, an AMEL could not be used in place
of the emissions standard.

Table 5--Summary of LDAR Requirements To Be Replaced With the Proposed LDSN-DRF System
----------------------------------------------------------------------------------------------------------------
Applicable rules with LDAR requirements Citation Requirement replaced with LDSN-DRF system
----------------------------------------------------------------------------------------------------------------
NSPS VV................................. 60.482-2(a)(1)........ EPA Method 21 monitoring of pumps in light
liquid service.
60.482-7(a) and (c)... EPA Method 21 monitoring of valves in gas/
vapor service and in light liquid service.
60.482-7(h)(3)........ EPA Method 21 monitoring at a reduced
frequency for valves in gas/vapor service and
in light liquid service that are designated
as difficult-to-monitor.
60.486(g)............. Schedule of monitoring and leak percentage for
valves utilizing skip periods.
NSPS VVa................................ 60.482-2a(a)(1)....... EPA Method 21 monitoring of pumps in light
liquid service.
60.482-7a(a) and (c).. EPA Method 21 monitoring of valves in gas/
vapor service and in light liquid service.
60.482-7a(h)(3)....... EPA Method 21 monitoring at a reduced
frequency for valves in gas/vapor service and
in light liquid service that are designated
as difficult-to-monitor.
60.482-11a(a), (b), EPA Method 21 monitoring of connectors in gas/
(b)(1), (b)(3), vapor service and in light liquid service.
(b)(3)(i)-(iv), and
(c).
60.486a(g)............ Schedule of monitoring and leak percentage for
valves utilizing skip periods.
HON..................................... 63.163(b)(1).......... EPA Method 21 monitoring of pumps in light
liquid service.
63.168(b)-(d)......... EPA Method 21 monitoring of valves in gas/
vapor service and in light liquid service.
63.168(f)(3).......... EPA Method 21 monitoring following successful
repair of valves in gas/vapor service and in
light liquid service.
63.173(a)(1).......... EPA Method 21 monitoring of agitators in gas/
vapor service and in light liquid service.
63.173(h)............. EPA Method 21 monitoring at a reduced
frequency for agitators in gas/vapor service
and in light liquid service that are
designated as difficult-to-monitor.
63.174(a)-(c)......... EPA Method 21 monitoring of connectors in gas/
vapor service and in light liquid service.
63.175(c)(3), (d)(1), Quality improvement program for valves where
and (d)(4)(ii). the leak rate is equal to or exceeds 2%.
63.178(c)(1)-(3)...... EPA Method 21 monitoring of components using
the alternative means of emission limitation
for batch processes.
63.181(b)(1)(ii)...... Schedule by process unit for connector
monitoring.
63.181(b)(7)(i) and Identification, explanation, and monitoring
(ii). schedule of difficult-to-monitor components.
63.181(d)(7).......... Listing of connectors subject to EPA Method 21
monitoring.
63.181(d)(8).......... EPA Method 21 monitoring for batch processes.
----------------------------------------------------------------------------------------------------------------

In order to achieve emission reductions at least equivalent to
those achieved in the requirements listed in Table 5, the proposed
LDSN-DRF must meet the following requirements.

A. LDSN Specifications

(a) Sensor selection. A sensor meeting the following specifications
is required:
(1) The sensor must respond to the compounds being processed. The
average response factor of each process stream must be less than or
equal to three. If the average response factor of a process stream is
greater than three, the components in that service are not covered by
this AMEL.
(2) The sensor must be capable of maintaining a detection floor of
less than 10 ppbe on a rolling 10-minute average, when adjusted for the
system response to the most recent successful bump test conducted in
accordance with IV.A(e)(2). The detection floor is determined at three
times the standard deviation of the previous 10 minutes of data
excluding excursions related to emissions peaks.

[[Page 56946]]

[GRAPHIC] [TIFF OMITTED] TN13OC21.002

Detection Floor<INF>Sensor n</INF> = Calculated detection floor of
sensor n (ppbe)
SD<INF>Local n</INF> = Local (previous ten minutes) standard
deviation of measurements excluding transient spikes (sensor raw
output typically mV)
Bump Test Gas Conc = Concentration of the isobutylene bump test gas
per manufacturer (ppb)
Bump Test Response<INF>Sensor n</INF> = the peak of the sensor
response over the baseline to the most recent bump test (sensor raw
output typically mV)

(3) The sensor must record data at a rate of once per second.
(4) Records of sensor selection must be maintained as specified in
IV.C(c) and records of detection floor must be maintained as specified
in IV.C(g).
(b) Sensor placement. The sensor placement must meet the following
specifications:
(1) The Mid-Crude process unit must have a minimum of 44 sensors
and the Meta-Xylene process unit must have a minimum of 10 sensors. All
components covered by the LDSN-DRF must be no further than 50 feet from
a sensor node in the horizontal plane, and sensor nodes must be placed
at least every 20 feet vertically. Sensor nodes must be placed and must
remain in accordance with the single level and multi-level records
required in IV.C(d).
(2) As part of the management of change procedure, FHR must
identify if the changes to process equipment are within the 50-foot
radius and 20-foot elevation of any single sensor within the process
unit or whether new process streams exist within the LDSN. FHR must
identify any LDAR-applicable components associated with the changes to
the process equipment that are outside of the 50-foot radius and 20-
foot elevation requirements for the LDSN or that contain process
streams with a response factor of greater than three and comply with
the standard EPA Method 21 LDAR requirements for those components as
required in the applicable subpart(s). FHR must maintain the management
of change records in IV.C(e). review the placement of sensors and the
need for additional sensors when there are changes to process equipment
and systems that are expected to affect the DTU as part of the
management of change procedures.
(c) PSL notifications. The system must perform a 72-hour lookback a
minimum of once per day that includes the previous 24-hour period to
determine the percent of time positive detections were registered.
Positive detections are defined as peak excursions above the detection
floor. If positive detections are registered for at least 5 percent of
the time during the rolling 72-hour lookback, a PSL notification must
be issued. Records of raw sensor readings and PSL notifications must be
maintained in accordance with IV.C(g) and (i), respectively.
(d) Meteorological Data. FHR must continuously collect wind speed
and wind direction data in each process unit at least once every 15
minutes. FHR must maintain records in accordance with IV.C(h).
(e) QA/QC. The following QA/QC must be employed for the sensors in
the network:
(1) Sensors must be calibrated by the manufacturer prior to
deployment. Once installed, each sensor must be tested for responsivity
and wireless communication by challenging it with isobutylene gas or
another appropriate standard. FHR must maintain records in accordance
with IV.C(f).
(2) FHR must conduct a bump test on each sensor quarterly. At a
minimum, quarterly bump tests must be conducted no more than 100 days
apart.
(i) The bump test must be conducted with isobutylene gas or another
appropriate standard and include a mechanism to provide nominally
ambient level moisture to the gas.
(ii) The bump test is successful if the response of the sensor
exceeds 50 percent of the nominal value of the standard and the
adjusted detection floor does not exceed 10 ppbe. The bump test may be
repeated up to two additional times if the first bump test is
unsuccessful.
(iii) If the bump test is unsuccessful after the third try, the
sensor must be recalibrated or replaced with a calibrated sensor within
24 hours of the third unsuccessful try. After recalibration, a new bump
test must be conducted following the procedure outlined above.
(iv) FHR must maintain records of the bump test in accordance with
IV.C(f) and records of the detection floor must be maintained in
accordance with IV.C(g).
(3) The health of each sensor must be confirmed for power and data
transmission at least once every 15 minutes. Data transmission, which
includes data recorded by the sensor every second as noted in
IV.A(a)(3), must occur at least once every 15 minutes. The rolling 10-
minute average detection floor data collected in accordance with
IV.A(a)(2) must be updated with each new minute of data every 15
minutes. Sensors that fail to collect data in accordance with
IV.A(a)(2) and (3) and transmit data in accordance with this paragraph
must be reset, repaired, or replaced. Following a sensor reset or
repair, FHR must test the responsivity and wireless communication of
the sensor through a bump test according to the procedure specified in
IV.A(e)(2). FHR must maintain records of sensor health in accordance
with IV.C(f).
(4) At least once each calendar quarter, conduct a check for wind
direction to ensure the wind sensor is properly oriented to the north.
If the wind sensor is not within 15 degrees of true north, it must be
adjusted to point to true north. At a minimum, quarterly wind direction
checks must be conducted no more than 100 days apart. The results of
the quarterly check for wind direction must be kept in accordance with
IV.C(h).
(f) Downtime. The sensor network must continuously collect data as
specified in paragraph IV.A(e)(3), except as specified in this
paragraph:
(1) The rolling 12-month average operational downtime of each
individual sensor must be less than or equal to 10 percent.
(2) Operational downtime is defined as a period of time for which
the sensor fails to collect or transmit data as specified in IV.A(e)(3)
or the sensor is out of control as specified in IV.A(f)(3).
(3) A sensor is out of control if it fails a bump test or if the
sensor output is outside of range. The beginning of the out of control
period for a failed bump test is defined as the time of the failure of
a bump test. The end of the out-of-control period is defined as the
time when either the sensor is recalibrated and passes a bump test, or
a new sensor is installed and passes the responsivity and communication
challenge. The out-of-control period for a sensor outside of range
starts at the time when the sensor first reads outside of range and
ends when the sensor reads within range again.
(4) The downtime for each sensor must be calculated each calendar
month. Once 12 months of data are available, at the end of each
calendar month, FHR must calculate the 12-month average by averaging
that month with the previous 11 calendar months. FHR must determine the
rolling 12-

[[Page 56947]]

month average by recalculating the 12-month average at the end of each
month.
(5) FHR must maintain records of the downtime for each sensor in
accordance with IV.C(m).

B. DRF Specifications

When a new PSL notification is received, the following actions
apply:
(a) An initial screening investigation must begin within three
calendar days of receiving a new PSL notification.
(1) The initial screening investigation must utilize technology
that can detect hydrocarbons or that is capable of responding to the
compounds or mixture of compounds in the process streams at levels
appropriate for locating leaks. This technology must be maintained per
manufacturer recommendations. Technologies that the EPA finds
appropriate for use are PIDs, FIDs, and OGI cameras.
(2) Each potential leak source identified in the initial screening
investigation must be monitored by EPA Method 21 as specified in
section 60.485a(b) of 40 CFR part 60, subpart VVa.
(3) If an instrument reading equal to or greater than the
concentrations listed in Table 2 is measured, a leak is detected. The
maximum instrument reading must be recorded for each leak identified. A
weatherproof and readily visible identification shall be attached to
the leaking equipment. The identification may be removed once the
component has been repaired, with the repair confirmed through follow
up EPA Method 21 monitoring.
(4) When a leak is detected, it shall be repaired as specified in
the applicable subpart(s), except as specified in this paragraph. If
the leak source is not applicable to LDAR, repairs must be completed
and verified within 30 calendar days of identification. If the leak
source is determined to be associated with authorized emissions (e.g.,
regulated emissions from a stack or process equipment that are not
fugitive emissions), the facility must document this information for
the record, and the PSL can be closed.
(5) If a single leak is detected at 3,000 ppm or greater by EPA
Method 21, the investigation is complete, and the PSL can be closed
once the leak has been repaired in accordance with the applicable
subpart(s).
(6) If a total of three leaks are detected below 3,000 ppm but
above the leak definitions specified in Table 2 by EPA Method 21, the
investigation is complete, and the PSL can be closed once the leaks
have been repaired in accordance with the applicable subpart(s).
(7) For each initial screening investigation in which a potential
leak source is not identified after 30 minutes of active screening
within the PSL, record the latitude and longitude coordinates in
decimal degrees to an accuracy and precision of five decimals of a
degree using the North American Datum of 1983 for the path taken during
the screening investigation. Include the date and time stamp of the
start and end of the investigation. The PSL must remain open, but the
initial screening investigation may stop.
(b) A second screening investigation must be conducted within seven
calendar days of stopping the initial screening investigation as
described in IV.B(a)(7). The conditions specified in IV.B(a)(1) through
(6) apply to this second screening investigation.
(c) If no potential leak sources are identified during the second
screening investigation, and the PSL detection level increases by two
times the initial detection level, a PSL update notification must be
sent to facility personnel based on the higher detection level. A new
screening investigation must occur within three calendar days of
receiving the PSL update notification with the higher detection level,
following the conditions specified in paragraphs IV.B(a)(1) through
(6). This step must be repeated every time the PSL notification is
sent, and a leak source is not found on the second screening. The PSL
must remain open until the conditions in IV.B(b)(5) or (6) are met.
(d) If no potential leak source has been identified following the
screening investigations in IV.B(b) and (c) and 90 days have passed
since the original PSL notification, all sensors used to create the PSL
must be bump tested in accordance with IV.A(e)(2) and a full survey of
the LDAR-applicable components within the PSL must be conducted with
EPA Method 21 within 10 calendar days. A leak is defined by the
applicable subpart(s). All leaks identified during this survey must be
repaired and verified after which the PSL will be closed. If no leaks
are identified in this final screening, ``no leak source found'' must
be recorded and the PSL will be closed.
(e) FHR must maintain the records in accordance with IV.C(i)-(l).

C. Recordkeeping

The following records related to the LDSN-DRF must be maintained in
addition to the records from the relevant subparts, except as noted in
Table 5.
(a) Fugitive Emission Management Plan (FEMP) detailing the
boundaries of the Meta-Xylene and Mid-Crude process units which are
complying with this AMEL. The plan must include the records for the
LDSN specified in paragraph IV.C(d), a list of identification numbers
for equipment subject to the EPA Method 21, no detectable emissions, or
AVO work practice requirements of the applicable subparts, and a map
clearly depicting which areas in each process unit are covered by the
LDSN-DRF and which are covered by the EPA Method 21, no detectable
emissions, or AVO work practices.
(b) Records of the sensor response factors for the applicable
process streams.
(c) Manufacturer, measurement principle, response factors, and
detection level for each sensor.
(d) Records of sensor placement, including geographic information
system (GIS) coordinates and elevation of the sensor from the ground,
and diagrams showing the location of each sensor and the detection
radius of each sensor. One diagram must show all sensors, with an
indication of the level each sensor is located on. Additional diagrams
showing sensor layout must be provided for each level of the process
unit.
(e) Records of each MOC. For each MOC, records of the determination
that either IV.C(e)(1) or (e)(2) applies. The MOC must also address
updates to the diagrams in the FEMP of each sensor or the list of
equipment identification numbers, as applicable:
(1) The changes are within the LDSN coverage area (i.e., within 50-
foot radius and 20-foot elevation of coverage for each individual
sensor) and the response factor of any new process streams is less than
or equal to three; or
(2) The components will be added to an applicable EPA Method 21, no
detectable emissions, or AVO work practice where the LDSN would not
provide coverage.
(f) Records of initial and subsequent calibrations, bump tests for
responsivity and wireless communication initially and upon sensor
repair or reset, quarterly bump tests, bump tests prior to PSL closure
where leaks have not been found within 90 days, and bump tests
following out of control periods, including dates and results of each
calibration and bump test, as well as a description of any required
corrective action and the date the corrective action was performed.
Records of calibration gases used for the bump tests, the ambient
moisture level during the bump tests, and the mechanism for providing
nominally ambient level moisture to the gas during the bump tests.
Records of sensor health related to power and data transmission.

[[Page 56948]]

(g) Raw sensor readings. Additionally, for each sensor, the percent
of time positive detections were registered during the 72-hour lookback
must be recorded each day and the minimum, average, and maximum
detection floor.
(h) Network meteorological data, including wind direction and wind
speed. Record the results of each quarterly check of the wind sensor
orientation. Record the latitude and longitude coordinates of the
original location of the wind sensor. The wind sensor must remain
within 300 feet of the original location. Record each movement of the
wind sensor, the latitude and longitude coordinates for the new
location, and the distance in feet between the new location and the
original location.
(i) PSL documentation. For each PSL, the record must include the
notification date, investigation start date, investigation results
including the date each leak was found, leaking component location
description, EPA Method 21 reading, repair action taken, date of
repair, and EPA Method 21 reading after repair.
(j) PSL documentation where PSL is not closed out after the initial
investigation. For each PSL that cannot be closed out after the initial
investigation, a record must include the initial screening performed,
including the latitude and longitude coordinates indicating the path
taken during the screening investigation, the start and end date and
times of the investigation, any OGI video taken during the
investigation, and any Method 21 readings observed during the
investigation.
(k) If a PSL is caused by an authorized emission source, the
documentation must include the notification date, investigation start
date, investigation results, emission source identification, and
description of ``authorized emissions''.
(l) Records of PSLs closed out where no cause of the PSL was
determined.
(m) For each sensor, the date and time of the beginning and end of
each period of operational downtime.
(n) For each additional annual compliance demonstration conducted
under the compliance assurance provisions of IV.E below, the
documentation must include the date of survey, the plot plan showing
the verification zone of each sensor, the list of valves in the
verification zones, the total population of valves in the process unit,
the EPA Method 21 reading for each valve and pump monitored, and the
corrective action taken if the LDSN is found to be in violation of the
sensor placement requirements.
(o) Records of deviations where a deviation means FHR fails to meet
any requirement or obligation established in this AMEL or fails to meet
any term or condition that is adopted to implement an applicable
requirement or obligation in this AMEL and that is included in the
operating permit for the Mid-Crude or Meta-Xylene process units at FHR.

D. Reporting

Semiannual reports must be submitted via the Compliance and
Emissions Reporting Data Interface (CEDRI), which can be accessed
through the EPA's Central Data Exchange (CDX) (<a href="https://cdx.epa.gov">https://cdx.epa.gov</a>)
following the requirements in section 63.9(k). Unless the report is
submitted by electronic media, via mail it must be addressed to the
attention of the Group Leader of the Refining and Chemicals Group.
Semiannual reports must include the following information:
(a) All of the information required in the relevant subparts.
(b) For each PSL, the notification date, investigation start date,
investigation results including the date each leak was found, type of
component, EPA Method 21 reading, and date of repair.
(c) The number of PSLs that were closed out where no cause of the
PSL was determined.
(d) The operational downtime percentage for each sensor determined
each month.
(e) For each sensor that fails a bump test, identification of the
sensor, date of failed bump test, and corrective action taken.
(f) Any changes to the sensor network, including those resulting
from the compliance assurance actions in IV.E.
(g) The date of each EPA Method 21 survey for the additional annual
compliance demonstration in IV.E, number of valves and pumps monitored,
number of leaks identified, number of leaks identified above 18,000
ppm, corrective action taken if leaks are identified above 18,000 ppm
and the date the corrective action was taken or is planned to be taken.
(h) Once the criteria in IV.E(b) is met, a statement that FHR has
met the criteria and additional annual compliance demonstration are no
longer required.
(i) Reports of deviations recorded under IV.C(o) which occurred in
the semi-annual reporting period, including the date, start time,
duration, description of the deviation, and corrective active.

E. Additional Annual Compliance Demonstration

In addition to continuous compliance with the LDSN-DRF as required
by the sections IV.A-D, the following annual compliance demonstration
actions are required for the LDSN-DRF system located in the Meta-Xylene
and Mid-Crude process units:
(a) Method 21 of appendix A-7 of part 60 must be conducted in each
process unit equipped with the LDSN-DRF according to the following
requirements:
(1) The first survey must be conducted within 12 calendar months of
approval of the AMEL. Subsequent surveys must be conducted no sooner
than 10 calendar months and no later than 12 calendar months after the
preceding survey.
(2) Identify each verification zone on a plot plan. The
verification zone is the area between the radii that are 45 and 50 feet
from each individual sensor. Monitor the valves located in these
verification zones as described in IV.E(a)(2)(i) through (v) using EPA
Method 21 as specified in section 60.485a(b) of 40 CFR part 60, subpart
VVa, with the exception that the high scale calibration gas must be
approximately 20,000 ppm.
(i) Determine the total number of valves located in the individual
process unit. The minimum number of valves monitored must equal 20
percent of the total population of valves in the process unit.
(ii) Determine the total number of valves that occur in only one
sensor verification zone (i.e., verification zones that have no overlap
with other verification zones). If the number of valves that occur in
only one sensor verification zone is greater than the minimum number of
valves that must be monitored, monitor a random selection of these
valves according to IV.E(a)(2)(v).
(iii) If the number of valves that occur in only one sensor
verification zone is less than the minimum number of valves that must
be monitored, determine the total number of valves that occur in all
verification zones, including those that overlap. If the total number
of valves in all verification zones is greater than the minimum number
of valves that must be monitored, monitor all the valves that occur in
only one sensor verification zone. Additionally, monitor a random
selection of valves, chosen in accordance with IV.E(a)(2)(v), that
appear in verification zones that overlap until the 20 percent minimum
is achieved.
(iv) If the number of valves in all verification zones is less than
20 percent

[[Page 56949]]

of the total population, then monitor all of the valves in all
verification zones. Additionally, monitor a random sample of additional
valves within the LDSN but outside of the verification zones, chosen in
accordance with IV.E (a)(2)(v), until the 20 percent minimum is
achieved.
(v) Random sampling of valves. To determine the random selection of
valves to monitor, determine the population of valves that must be
randomly sampled as determined in IV.E(a)(2)(ii), (iii), or (iv) (i.e.,
20 percent of the total valve population or 20 percent of the total
valve population minus the number of valves in the verification zones).
Divide the population of valves by the number of valves that must be
sampled and round to the nearest integer to establish the sampling
interval. Using the valve IDs sequentially, monitor valves at this
sequential interval (e.g., every 5 valves). Alternatively, use the
valve IDs and a random number generator to determine the valves to
monitor. Each survey conducted under IV.E(a)(1) must start on a
different valve ID such that the same population of valves is not
monitored in each survey.
(3) Monitor each pump located in the process unit using EPA Method
21 as specified in section 60.485a(b) of 40 CFR part 60, subpart VVa.
(4) For purposes of this monitoring, a leak is identified as an
instrument reading above the leak definitions in Table 2 of this AMEL.
All identified leaks must be repaired within 15 calendar days of
detection, with a first attempt completed within five calendar days of
detection.
(5) If any components are identified with EPA Method 21 screening
values above 18,000 ppm, the LDSN is not in compliance with the
approved AMEL, except components under current investigations in an
active PSL with screening values above 18,000 ppm may be excluded
provided the PSL has been open for less than 14 days or the components
have been identified and placed on delay of repair. The period of
noncompliance with the AMEL extends until the actions in IV.E(5)(i)-
(ii) are completed and the actions in IV.E(5)(iii) result in all
components identified with EPA Method 21 to have screening values less
than or equal to 18,000 ppm.
(i) Within 30 days of the survey conducted in IV.E(a)(4), which
identifies components with EPA Method 21 screening values above 18,000
ppm, FHR must submit a plan to revise the sensor network to <a href="/cdn-cgi/l/email-protection#e6a5a5a1cba7b1b6a6839687c8818990">[email&#160;protected]</a>. Revisions to the sensor network must include the addition
of new sensors to reduce the detection radius of each sensor, location
changes of any previously deployed sensors, and/or the deployment of a
different sensor type. The plan must also include the location of the
controlled release specified in IV.E(a)(5)(ii) to verify the
performance of the revised network.
(ii) Within 30 days of completing the approved sensor network
changes, FHR must conduct a controlled release of 1.4 g/hr isobutylene
to determine the performance of the network.
(iii) Within 60 days of completing the approved sensor network
changes, FHR must repeat the actions in IV.E(a)(2) through (a)(4). If
any components are identified with EPA Method 21 screening values above
18,000 ppm, FHR remains in noncompliance with the approved AMEL, and
FHR must repeat the actions required in IV.E(a)(5)(i) and (ii).
(b) FHR may stop conducting the additional annual compliance
demonstration required in IV.E(a) if no leaks above 18,000 ppm are
identified with Method 21 of appendix A-7 of part 60 over a period of 2
consecutive calendar years.

V. Request for Comments

The EPA solicits comment on all aspects of this AMEL request. We
specifically seek comment regarding whether the proposed alternative
LDAR requirements listed in Section IV of this preamble would be
adequate for ensuring the LDSN-DRF will achieve detection and location
of component-level leaks. Additionally, we seek comment regarding
whether the proposed alternative will achieve emissions reductions at
least equivalent to the emissions reductions that would be achieved
through compliance with the applicable LDAR requirements in 40 CFR 60
Subparts VV, VVa, GGG, GGGa; 63 Subparts H and CC. Finally, as noted in
Section III, we also solicit comment on the EPA's proposed framework
for evaluation of future LDSN-DRF AMEL requests. Commenters should
include data or specific examples in support of their comments.

Panagiotis Tsirigotis,
Director, Office of Air Quality Planning and Standards.
[FR Doc. 2021-22233 Filed 10-12-21; 8:45 am]
BILLING CODE 6560-50-P

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