Document ID: EPA-HQ-OAR-2021-0299-0001
Agency: epa
Document Type: Notice
Title: Request for Approval of Alternative Means of Emission Limitation
Posted Date: 2021-10-13T04:00Z

[Federal Register Volume 86, Number 195 (Wednesday, October 13, 2021)]
[Notices]
[Pages 56934-56949]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[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:
     Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
     Email: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2021-0299 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2021-0299.
     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.
     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 https://www.regulations.gov/, 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 https://www.regulations.gov/ 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 
https://www.epa.gov/dockets.

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: [email protected].

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 [email protected]. 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 https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair.
    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 https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair or contact the public 
hearing team at (888) 372-8699 or by email at 
[email protected]. 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: https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair.
    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]]

[email protected]. 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 https://www.epa.gov/stationary-sources-air-pollution/alternative-means-emission-limitation-leak-detection-and-repair. 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 [email protected] 
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 
[email protected] 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 Regulations.gov. 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 
Regulations.gov.
    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 https://www.regulations.gov/, 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 https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ 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 
https://www.regulations.gov/, 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 https://www.epa.gov/dockets.
    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 https://www.regulations.gov/. For further information and updates on EPA Docket 
Center services, please visit us online at https://www.epa.gov/dockets.
    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 https://www.regulations.gov/ 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.
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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.
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    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:
     Meta-Xylene process unit at FHR West Refinery: eDTA = 
11,250 ppm; DTU = 18,000 ppm;
     Mid-Crude process unit at FHR West Refinery: eDTA = 12,500 
ppm; DTU = 18,000 ppm; and
     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:
     One or more leaks >=3,000 ppm is found and repaired;
     Three or more leaks <3,000 ppm are found and repaired;
     Malfunction, startup, or shutdown activity or other 
authorized emissions are identified and documented;
     Components on delay of repair have been repaired and 
monitored to verify repair;
     A leak source has not been identified and the PSL has not 
updated within 14 days or more; or
     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: https://www.epa.gov/sites/production/files/2020-09/documents/protocol_for_equipment_leak_emission_estimates.pdf
    \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:
     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.
     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.
     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\
---------------------------------------------------------------------------

    \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:
     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.
     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.
     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: 
http://doi.org/10.1525/elementa.369
---------------------------------------------------------------------------

    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 FloorSensor n = Calculated detection floor of 
sensor n (ppbe)
SDLocal n = 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 ResponseSensor n = 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) (https://cdx.epa.gov) 
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 [email protected]. 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