UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
Technical Note - Guidance for Developing Enhanced Monitoring Plans
INTRODUCTION
On October 1, 2015 EPA substantially revised the Photochemical Assessment Monitoring Stations
(PAMS) requirements in 40 CFR part 58 Appendix D. As part of the revision, EPA required state and local
monitoring agencies ("monitoring agencies") to make PAMS measurements (including hourly averaged
mixing height) at NCore sites in CBSAs with a population of 1,000,000 or more ("required PAMS sites").
The revisions also required state monitoring agencies with Moderate and above 8-hour O3
nonattainment areas and states in the Ozone Transport Region (OTR) to develop and implement an
Enhanced Monitoring Plan (EMP) detailing enhanced O3 and O3 precursor monitoring activities to be
performed to better understand area specific ozone issues. In addition, the rule specifies that the EPA
Regional Administrators have the authority to approve the EMPs (and other aspects of PAMS) for their
respective state.
The purpose of this technical note is to provide guidance to monitoring agencies for developing EMPs.
Note this guidance is not intended to provide additional requirements for state monitoring agencies, but
rather to provide additional information that is intended to provide clarity on the intent of the
requirement and to assist monitoring agencies as they develop their EMPs. Furthermore, the examples
of potential monitoring options provided here are intended to be illustrative and are not limiting.
EMP REQUIREMENT
The EMP requirement is located in 40 CFR part 58, Appendix D, paragraph 5(h) and states -
"(h) States with Moderate and above 8-hour O3 nonattainment areas and states in the Ozone
Transport Region as defined in 40 CFR 51.900 shall develop and implement an Enhanced
Monitoring Plan (EMP) detailing enhanced O3 and O3 precursor monitoring activities to be
performed. The EMP shall be submitted to the EPA Regional Administrator no later than October
1, 2019 or two years following the effective date of a designation to a classification of Moderate
or above O3 nonattainment, whichever is later.1 At a minimum, the EMP shall be reassessed and
approved as part of the 5-year network assessments reguired under 40 CFR 58.10(d). The EMP
will include monitoring activities deemed important to understanding the O3 problems in the
state. Such activities may include, but are not limited to, the following:
,^e0Sr%
1 The EPA previously provided guidance suggesting that all States in the OTR submit EMPs by July 1,
2018. Many States in the OTR have already made these submissions.
https://www3.epa. gov/ttnamtil/files/ambient/pams/PAMS%20Monitoring%20Network%20and%20EMP%20Plan%
20Guidance.pdf.
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(1)	Additional O3 monitors beyond the minimally required under paragraph 4.1 of this
appendix,
(2)	Additional N0X or NOy monitors beyond those required under 4.3 of this appendix,
(3)	Additional speciated VOC measurements including data gathered during different
periods other than required under paragraph 5(g) of this appendix, or locations other
than those required under paragraph 5(a) of this appendix, and
(4)	Enhanced upper air measurements of meteorology or pollution concentrations."
As discussed in the preamble to the final rule (published in the Federal Register on October 26, 2015,
page 65292), the details of what an enhanced monitoring plan needs to include are intentionally limited
to allow monitoring agencies as much flexibility in determining what enhanced ozone monitoring is
needed to understand their specific ozone issues. Examples of what might be included in an EMP are
provided, such as additional O3 monitoring sites beyond the minimally required sites, but the examples
do not restrict additional monitoring options the monitoring agency may desire.
In addition to states in the OTR, the requirement for an EMP is applicable to any state with a moderate
or above O3 non-attainment area under the 1997, 2008, and 2015 8-hour O3 NAAQS. For states with
moderate and above O3 non-attainment areas under the 1997 or 2008 NAAQS and states in the OTR, the
EMPs are due October 1, 2019. At this point, no states have moderate or above O3 non-attainment
areas for the 2015 NAAQS that are not classified as moderate or above under the 1997 or 2008 NAAQS.
If at some point in the future, an area is classified as moderate or above in a state that does not
currently have a moderate or above area, that state will have 2-years from the date of designation to
submit an EMP.
While the regulations specify that states with moderate or above O3 non-attainment areas are required
to develop an EMP, other states and local monitoring agencies may also wish to develop an EMP. The
EPA intends to support additional voluntary EMP monitoring beyond the required states because O3
precursors can and do cross state boundaries. Therefore, it may be important to perform EMP
monitoring in upwind or downwind states. This was expressly acknowledged for the OTR, but areas like
the Lake Michigan shoreline also have significant upwind and downwind impacts that should be
considered. In addition, many areas have had a long history of O3 issues and continued enhanced O3
monitoring may be appropriate to ensure continued progress and to better characterize O3 and
precursor concentrations.
CONSIDERATIONS FOR DEVELOPING AN EMP
The primary objective of EMP monitoring is to collect monitoring data that helps States understand their
ozone issues and to evaluate local control options to address those issues. It is recognized that
monitoring staff may not be the appropriate persons to identify what data is needed to better
understand the ozone issues in their state. As such, monitoring agencies should consider which partners
are needed to successfully develop and implement an EMP.
State monitoring agencies are strongly encouraged to work with their air quality planning staff who may
be more familiar with the state's ozone issues and data needs. Where appropriate, monitoring agencies
are also encouraged to work with neighboring states to coordinate plans to help develop the larger
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picture of ozone formation and transport in the multi-state area. Such coordination is essential in the
OTR states due to the importance of transport in ozone formation in those states.
States with local monitoring jurisdictions are encouraged to work with local agencies to help identify the
most appropriate locations and types of monitoring to include in an EMP. Local monitoring
organizations are not required by the regulation to develop and implement an EMP, however, voluntary
EMPs are encouraged and will be considered in addition to the state's EMP in funding considerations.
EPA Regional staff should be included early in the planning stages and may be available to assist with the
planning and coordination activities. EPA's monitoring and modeling staff in OAQPS and ORD will also
be available to assist with planning. It may also be desirable to seek assistance from multi-state
planning organizations such as NESCAUM, MARAMA, or LADCO. These multistate organizations often
have good insight into the questions needing to be answered to understand the larger ozone issues as
well as being good resources to help facilitate and coordinate EMP planning across the airshed.
States may also want to look for other interested groups who may be able to assist in EMP planning and
implementation. Other Federal agencies, such as NASA and NOAA, have interests in understanding
ozone formation and atmospheric science, and as such may be able to provide resources such as access
to equipment or data. States may also wish to partner with local colleges and universities where
appropriate to assist with EMP development and implementation.
Once the appropriate team is assembled, the team can identify the specific questions needing answers
and the best ways enhanced monitoring can help the state understand and address their ozone issues.
The options included in the final EMP should reflect the degree and nature of the State's ozone issues.
EMPs for States with more serious ozone issues will likely include more measurements and
sophistication than for States with less serious ozone issues. Factors such as size and number of non-
attainment areas, persistence of 03 non-attainment, complex terrain, and multi-state transport should
be considered when developing the scope of an EMP.
EMPs should also reflect the availability of resources (e.g., funding, staff availability). EPA will provide
funding for EMPs through 105 grants. EPA Regional staff can help inform monitoring agencies how
much 105 grant funding is available and how that funding will be distributed. States are also
encouraged to leverage existing resources and monitoring where possible. As discussed above, other
non-State partners may be able to provide resources that can help provide data useful to understand
the State's ozone issues.
EXAMPLES OF MONITORING APPROPRIATE FOR INCLUSION IN AN EMP
The following is a summary of monitoring options that might be appropriate for inclusion in an EMP.
This summary is not intended to be an exhaustive or limiting list, but illustrative of the types of
monitoring appropriate for an EMP. Monitoring to be included in an EMP need not be new, and States
are encouraged to document existing monitoring that is intended to help them understand their ozone
issues as part of their EMP.
Additional O3 and NOx Monitors
The minimum number of required O3 and NOx monitoring sites are provided in 40 CFR part 58 Appendix
D. A monitoring agency may wish to run additional O3 or NOx sites to help understand the extent of O3
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and N0X pollution and for other purposes. It is recognized that many monitoring agencies are currently
running more O3 and NOx monitors than are required under Appendix D. Monitoring agencies are
encouraged to include existing O3 or NOx monitoring beyond the minimum required in their EMPs along
with any new O3 or NOx monitoring arising from EMP planning.
Low cost methods that are not Federal Reference Method or Federal Equivalent Measurement
(FRM/FEM) technologies exist that may also be useful to understanding ozone issues. A number of low
cost "sensors" for the measurement of O3, NOx, and VOCs are available or are becoming available that
may be useful in understanding O3 issues. While sensors generally are not believed to be able to provide
FRM/FEM quality measurements at this time, when operated properly the data collected from sensors
may be useful in evaluating the spatial variability of O3 and O3 precursors at a density not possible using
conventional monitors. Low cost passive sampling methods also exist for the measurement of O3, NOx,
and VOCs that may also provide useful information on the spatial variability of O3 and O3 precursors.
Monitoring agencies are encouraged to consider how sensors and passive sampling can be used to help
them understand the O3 issues in their state especially as sensor technologies and techniques for using
sensor data mature.
Additional or Alternative PAMS Sites
Prior to the 2015 revisions to the PAMS requirements, the PAMS network design featured multiple
"types" of PAMS sites including:
•	Type 1 - Upwind sites
•	Type 2 - Maximum ozone precursor sites
•	Type 3 - Maximum ozone concentration sites, and
•	Type 4 - Downwind sites
The newly required PAMS sites are expected to be at NCore sites which are typically neighborhood scale
sites. Individual NCore sites may not fit into any of the historic PAMS site types. In developing the new
requirements, it was recognized that many states may have existing PAMS sites that may be more
suitable for making the required PAMS measurements. As such, a waiver option was included to allow
monitoring agencies to make PAMS measurements at alternative locations such as existing PAMS sites.
Monitoring agencies should discuss any requested waivers for alternative PAMS sites in their Annual
Network Plans (ANP) and EMPs as well as the status of those waiver requests.
As part of the EMP preparation, monitoring agencies may identify the need to run additional PAMS sites
to better understand ozone formation and transport in their airshed. For example, upwind or
downwind measurements may be important in areas with significant transport issues. Note however,
because these sites are optional, monitoring agencies may elect to monitor a subset of PAMS
measurements and may use alternative methods and sampling frequencies than those identified in the
requirements and PAMS Technical Assistance Document (TAD). For example, a monitoring agency may
wish to use canister sampling at additional PAMS sites to measure speciated VOCs on a 24-hour average
l-in-6 day sampling frequency rather than the hourly frequency for required PAMS sites. Monitoring
agencies are encouraged to document any additional PAMS sites they intend to operate as part of their
ANP and EMP including the measurements that will be made.
Measurements Made out of PAMS Season
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At a minimum, PAMS measurements are to be taken during the PAMS season of June thru August at all
required PAMS sites. Because the primary measurement objective of the PAMS required network is to
create a consistent database of PAMS measurements across the network, no waiver was provided to
allow monitoring agencies to change the required PAMS season. It is recognized that the required PAMS
season of June thru August may not be sufficient to understand local ozone issues. As such, monitoring
agencies may wish to make PAMS measurements during additional periods beyond the required PAMS
season. Similar to additional PAMS sites, any measurements made outside of the PAMS required season
would be optional and as such monitoring agencies may elect to use alternative sampling frequencies.
For example, a monitoring agency may choose to measure carbonyls on a single 24-hour sample on a 1-
in-6 day sampling frequency rather than the three 8-hr average samples on a l-in-3 day sampling
frequency required during the PAMS season. Also, monitoring agencies may wish to run continuous
instruments year around. Those measurements that overlap with NCore (ozone, NOx, various
meteorological measurements) are already required to be made year-round. Monitoring agencies are
encouraged to consider the value of making measurements of mixing height and speciated VOCs year-
round during their EMP planning.
Special Studies
Special studies may be particularly useful to states in understanding their specific ozone issues. Shorter
term (on the order of weeks to years) studies can be designed to help answer area specific questions
regarding ozone formation. Special studies allow monitoring agencies to make more intensive or
expensive measurements for a shorter period of time where the measurements might not be practical
on a continuing basis. For example, states have partnered with the EPA, NASA, NOAA and others to
make intensive special studies of a number of airsheds in recent years. Monitoring agencies are
encouraged to include special studies in their EMPs as appropriate.
Due to the short-term nature of special studies it may be difficult for monitoring agencies to anticipate
what measurements they may make as part of a special study for the purposes of creating a 5-year EMP.
However, where possible monitoring agencies are encouraged to document special studies they are
planning to participate in as part of their EMP. Not including a special study in an EMP does not
preclude the state from using EMP funding for the study in following years.
Advanced Upper Air and Additional Meteorological Measurements
The PAMS regulations require states to measure hourly mixing height at required PAMS sites. It is
expected that most states will use a ceilometer to meet this requirement. Other upper air systems also
exist that may be appropriate for inclusion in an EMP. The following paragraphs discuss some upper air
systems that may be appropriate for use in an EMP. This list is not intended to be exclusive and other
systems may also be appropriate for use.
Prior to the recent PAMS revisions, the requirements called for "upper air measurements" at each PAMS
area. Most states installed and operated Radar Wind Profilers equipped with Radio Acoustic Sounding
Systems (RWP/RASS) to meet this requirement. In addition to obtaining estimates of mixing height from
these systems, RWP also provides wind speed and wind direction measurements in the upper air. While
these systems may be expensive to install and maintain, many states find great value in this information
for understanding ozone formation and transport. As such, continued operation of these systems as
part of an EMP may be appropriate.
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A SODAR is similar to a RWP except that sound waves are used rather than radio waves and both are
capable of measuring wind direction and wind speed versus height in the atmosphere. Also like RWP,
algorithms have been developed to estimate mixing height from SODAR readings.
Several forms of LIDAR exist that are suitable for use in air quality measurements. Ceilometers, as
discussed above, are a form or LIDAR capable of measuring mixing height based on relative fine
particulate concentrations. Other forms include those that can be tuned to measure vertical profiles of
one or more important atmospheric constituents such as ozone and water vapor. While these vertical
profiles are of significant value on their own in understanding atmospheric chemistry, similar to
ceilometers, algorithms have been developed to estimate mixing height based on the abrupt change in
these constituents at the boundary layer. It is unlikely that these systems will find widespread use in the
PAMS program as they are generally considered research grade at this time. However, where
appropriate the addition of these vertical profiles can provide valuable information on the formation
and transport of ozone.
Doppler LIDAR are also available that are capable of providing upper air wind speed and wind direction
data similar to a RWP. A doppler LIDAR has several advantages over a RWP that include higher
resolution data, lower capital cost, a smaller footprint (roughly the size of an office desk), and
portability. Also, because they are light based they are less intrusive than RASS or SODAR systems
making doppler LIDAR more suitable for long term use in urban areas. Doppler LIDARS have a similar
vertical range to RWP of approximately 100 m to 5 km.
A microwave radiometer is a sensitive receiver that detects the microwave emissions of vapor and liquid
water molecules in the atmosphere. These systems can be used to measure vertical gradients of
temperature, relative humidity, and water vapor in the atmosphere. Microwave radiometers are
relatively small (about twice the size of a mailbox) and have low operational costs.
The PANDORA spectrometer is an operational research instrument developed by NASA-Goddard to
make total column measurements of O3, SO2, formaldehyde (HCHO), BrO, NO2 and H2O. NASA and EPA
believe that these total column measurements collocated with the mixing height and other ground
based measurements made at a select number of PAMS/EMP sites would be most valuable in evaluating
current and future satellite air quality measurements. In the interest of supporting a network of
PANDORA sites at these sites, NASA in partnership with the EPA is making a number of these
instruments available to the PAMS/EMP community at no cost. PAMS/EMP sites would only be asked to
host the equipment and provide internet access for the collection of the data by a central data system
operated by NASA or EPA. The PANDORA spectrometer is very small and has low power requirements.
In addition, the equipment runs unattended with minimal operator interaction.
FOR FURTHER INFORMATION
For additional information, please contact Kevin Cavender of the Air Quality Assessment Division,
Ambient Air Monitoring Group, 919-541-2364, cavender.kevin@epa.gov.
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