1

Draft Technical Support Document

Hawaii

Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act (CAA), the U.S. Environmental Protection 

Agency (EPA, or the Agency) must designate areas as either “unclassifiable,” “attainment,” or 

“nonattainment” for the 2010 one-hour sulfur dioxide (SO2) primary national ambient air quality 

standard (NAAQS). The CAA defines a nonattainment area as one that does not meet the 

NAAQS or that contributes to a violation in a nearby area. An attainment area is defined as any 

area other than a nonattainment area that meets the NAAQS. Unclassifiable areas are defined as 

those that cannot be classified on the basis of available information as meeting or not meeting the 

NAAQS.

Hawaii submitted a designations recommendation on May 19, 2011, ahead of a July 2, 2016, 

deadline for the EPA to designate certain areas established by the U.S. District Court for the 

Northern District of California. On February 4, 2016, the EPA concurred on Hawaii’s 2012-2014 

exceptional events package for volcanic emissions affecting four monitors in Hawaii County. 

With this concurrence, further described below and included in the docket for this designation, 

monitors in Hawaii County show no violations of the 2010 SO2 NAAQS for calendar years 

2012-2014.

The July 2, 2016 deadline is the first of three deadlines established by the court for the EPA to 

complete area designations for the 2010 SO2 NAAQS. Table 1 below lists Hawaii’s

recommendations and identifies the counties or portions of counties in Hawaii that the EPA 

intends to designate by July 2, 2016 based on an assessment and characterization of air quality 

through ambient air quality data, air dispersion modeling, other evidence and supporting 

information, or a combination of the above. 

Table 1. State Recommendation and EPA’s Intended Designation

Area Hawaii’s 

Recommended 

Area Definition

Hawaii’s 

Recommended 

Designation

EPA’s Intended 

Area Definition

EPA’s Intended 

Designation 

Hawaii County, 

Hawaii

Hawaii County Unclassifiable Same as State’s 

Recommendation

Unclassifiable/ 

Attainment

Background

On June 3, 2010, the EPA revised the primary (health based) SO2 NAAQS by establishing a new 

one-hour standard at a level of 75 parts per billion (ppb) which is attained when the three-year 

average of the 99th percentile of one-hour daily maximum concentrations does not exceed 75 

ppb. This NAAQS was published in the Federal Register on June 22, 2010 (75 FR 35520) and is 
2

codified at 40 CFR 50.17. The EPA determined this is the level necessary to protect public health 

with an adequate margin of safety, especially for children, the elderly and those with asthma. 

These groups are particularly susceptible to the health effects associated with breathing SO2. The 

two prior primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an 

entire year, codified at 40 CFR 50.4, remain applicable.

1 However, the EPA is not currently 

designating areas on the basis of either of these two primary standards. Similarly, the secondary 

standard for SO2, set at 500 ppb evaluated over 3 hours has not been revised, and the EPA is also 

not currently designating areas on the basis of the secondary standard.

General Approach and Schedule

Section 107(d) of the Clean Air Act requires that not later than one year after promulgation of a 

new or revised NAAQS, state governors must submit their recommendations for designations 

and boundaries to the EPA. Section 107(d) also requires the EPA to provide notification to states 

no less than 120 days prior to promulgating an initial area designation that is a modification of a 

state’s recommendation. If a state does not submit designation recommendations, the EPA will 

promulgate the designations that it deems appropriate. If a state or tribe disagrees with the EPA’s 

intended designations, they are given an opportunity within the 120 day period to demonstrate 

why any proposed modification is inappropriate.

On August 5, 2013, the EPA published a final rule establishing air quality designations for 29

areas in the United States for the 2010 SO2 NAAQS, based on recorded air quality monitoring 

data from 2009 - 2011 showing violations of the NAAQS (78 FR 47191). In that rulemaking, the 

EPA committed to address, in separate future actions, the designations for all other areas for 

which the Agency was not yet prepared to issue designations.

Following the initial August 5, 2013 designations, three lawsuits were filed against the EPA in 

different U.S. District Courts, alleging the Agency had failed to perform a nondiscretionary duty 

under the CAA by not designating all portions of the country by the June 2013 deadline. In an 

effort intended to resolve the litigation in one of those cases, plaintiffs Sierra Club and the 

Natural Resources Defense Council and the EPA filed a proposed consent decree with the U.S. 

District Court for the Northern District of California. On March 2, 2015, the court entered the 

consent decree and issued an enforceable order for the EPA to complete the area designations 

according to the court-ordered schedule.

According to the court-ordered schedule, the EPA must complete the remaining designations by 

three specific deadlines. By no later than July 2, 2016 (16 months from the court’s order), the 

EPA must designate two groups of areas: (1) areas that have newly monitored violations of the 

2010 SO2 NAAQS and (2) areas that contain any stationary sources that had not been announced 

as of March 2, 2015 for retirement and that according to the EPA’s Air Markets Database 

emitted in 2012 either (i) more than 16,000 tons of SO2 or (ii) more than 2,600 tons of SO2 with

 1 40 CFR 50.4(e) provides that the two prior primary NAAQS will no longer apply to an area one year after its 

designation under the 2010 NAAQS, except that for areas designated nonattainment under the prior NAAQS as of 

August 22, 2010, and areas not meeting the requirements of a SIP Call under the prior NAAQS, the prior NAAQS 

will apply until that area submits and the EPA approves a SIP providing for attainment of the 2010 NAAQS. These 

situations do not apply to the County of Hawaii.
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an annual average emission rate of at least 0.45 pounds of SO2 per one million British thermal 

units (lbs SO2/mmBTU). Specifically, a stationary source with a coal-fired unit that as of January 

1, 2010 had a capacity of over 5 megawatts and otherwise meets the emissions criteria, is 

excluded from the July 2, 2016 deadline if it had announced through a company public 

announcement, public utilities commission filing, consent decree, public legal settlement, final 

state or federal permit filing, or other similar means of communication, by March 2, 2015, that it 

will cease burning coal at that unit. 

The last two deadlines for completing remaining designations are December 31, 2017, and 

December 31, 2020. The EPA has separately promulgated requirements for states and other air 

agencies to provide additional monitoring or modeling information on a timetable consistent with 

these designation deadlines. We expect this information to become available in time to help 

inform these subsequent designations. These requirements were promulgated on August 21, 2015 

(80 FR 51052), in a rule known as the SO2 Data Requirements Rule (DRR). 

 

Updated designations guidance was issued by the EPA through a March 20, 2015 memorandum 

from Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air 

Division Directors, U.S. EPA Regions I-X. This memorandum supersedes earlier designation 

guidance for the 2010 SO2 NAAQS, issued on March 24, 2011, and it identifies factors that the 

EPA intends to evaluate in determining whether areas are in violation of the 2010 SO2 NAAQS. 

The guidance also contains the factors the EPA intends to evaluate in determining the boundaries 

for all remaining areas in the country, consistent with the court’s order and schedule. These 

factors include: 1) Air quality characterization via ambient monitoring or dispersion modeling 

results; 2) Emissions-related data; 3) Meteorology; 4) Geography and topography; and 5) 

Jurisdictional boundaries. This guidance was supplemented by two technical assistance 

documents intended to assist states and other interested parties in their efforts to characterize air 

quality through air dispersion modeling or ambient air quality monitoring for sources that emit 

SO2. Notably, the EPA released its most recent versions of documents titled, “SO2 NAAQS 

Designations Modeling Technical Assistance Document” (Modeling TAD) and “SO2 NAAQS 

Designations Source-Oriented Monitoring Technical Assistance Document” (Monitoring TAD) 

in December 2013.

On March 22, 2007, the EPA adopted a final rule, Treatment of Data Influenced by Exceptional 

Events (EER), to govern the review and handling of certain air quality monitoring data for which 

the normal planning and regulatory processes are not appropriate.2 Under the rule, the EPA may 

exclude monitored data from use in determinations of NAAQS exceedances and violations if a 

state demonstrates that an “exceptional event” caused the monitored exceedances. Before the 

EPA can exclude monitored data from these regulatory determinations, the state must flag the 

data in the EPA’s Air Quality System (AQS) database and, after notice and opportunity for 

public comment, submit a demonstration to justify the exclusion. After considering the weight of 

evidence provided in the demonstration, the EPA decides whether or not to concur with each 

flag. 

 2 72 FR 13560, March 22, 2007. On November 20, 2015, the EPA proposed revisions to the 2007 EER; the public 

comment period for this proposal closed February 3, 2016 (80 FR 224, November 20, 2015). The review in this 

document is based on the 2007 EER requirements and current EPA guidance.
4

On December 17, 2015, Hawaii Department of Health (HDOH) submitted documentation to the 

EPA to demonstrate that exceedances of the 2010 1-hour SO2 NAAQS that were recorded in 

2012-2014 at the Hilo (AQS ID: 15-001-1006), Mountain View (AQS ID: 15-001-2023), Ocean 

View (AQS ID: 15-001-2020), and Pahala (AQS ID: 15-001-2016) air monitoring stations 

located on the island of Hawaii resulted from volcanic-related exceptional events 

(“Documentation for Natural Events Excluded Data: Hilo Air Monitoring Station, AQS ID 15-

001-1006, Mountain View Air Monitoring Station, AQS ID 15-001-2023, Ocean View Air 

Monitoring Station, AQS ID 15-001-2020, Pahala Air Monitoring Station, AQS ID 15-001-2016, 

2012-2014 Sulfur Dioxide (SO2) Exceedances,” hereafter referred to as Hawaii’s 2012-2014 SO2

Exceptional Events package).3 The EPA’s February 4, 2016 technical support document, 

included in the docket for this designation, sets forth the basis for the EPA’s concurrence with 

HDOH’s claim that the exceedances summarized in Table 1 and listed in Hawaii’s 2012-2014 

SO2 Exceptional Events package, Appendix D4, were the result of volcano-related exceptional 

events.

Table 1. Number of Days and Hours for EPA Exceptional Events Concurrence by Monitor

2012 2013 2014

Totals, 

2012-2014

# days # hrs # days # hrs # days # hrs

# 

days # hrs

Hilo 

(AQS ID: 15-001-1006)

 

20 

 

57 

 

14 

 

42 

 

10 

 

35 

 

44 

 

134 

Mountain View 

(AQS ID: 15-001-2023)

 

20 

 

78 

 

17

 

42 

 

27 

 

65 

 

64

 

185 

Ocean View 

(AQS ID: 15-001-2020)

 

177 

 

484 

 

116 

 

280 

 

93 

 

232 

 

386 

 

996 

Pahala 

(AQS ID: 15-001-2016)

 

293 

 

1,725 

 

214 

 

906 

 

174 

 

600 

 

681 

 

3,231 

Totals, All Monitors:

 

510 

 

2,344 

 

361

 

1,270

 

304 

 

932 

 

1,175

 

4,546 

Based on monitored ambient air quality data collected between 2012 and 2014 and the EPA’s 

February 4, 2016 concurrence on Hawaii’s 2012-2014 SO2 exceptional events submittal based on 

volcanic emissions, no violations of the 2010 SO2 NAAQS have been recorded at a monitor in 

any undesignated part of the state for calendar years 2012-2014. Because monitors in the county 

of Hawaii (consisting of the Big Island of Hawaii) were recording violations of the standard prior 

to the recent exceptional events concurrence, the EPA is including the area in this round of 

designations. In this draft technical support document, the EPA discusses its review and 

technical analysis of Hawaii’s recommendation for the area that we are addressing. 

 3 “Documentation for Natural Events Excluded Data Hilo Air Monitoring Station, AQS ID 15-001-1006, Mountain 

View Air Monitoring Station, AQS ID 15-001-2023, Ocean View Air Monitoring Station, AQS ID 15-001-2020, 

Pahala Air Monitoring Station, AQS ID 15-001-2016, 2012-2014 Sulfur Dioxide (SO2) Exceedances, Final Report, 

January 2016” (“Hawaii’s 2012-2014 SO2 Exceptional Events package”). 4 Several pages were inadvertently omitted from Appendix D and are included in an email attachment from Lisa 

Young, HDOH, to Randall Chang, EPA, dated January 13, 2016, and included in the docket for this designation. 

Here forward “Appendix D” refers to Hawaii’s 2012-2014 SO2 Exceptional Events package and the email 

attachment.
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The following are definitions of important terms used in this document: 

1) 2010 SO2 NAAQS – The primary NAAQS for SO2 promulgated in 2010. This NAAQS is 

75 ppb, based on the three year average of the 99th percentile of the annual distribution 

of daily maximum one-hour average concentrations. See 40 CFR 50.17. 

2) Design Value - a statistic computed according to the data handling procedures of the 

NAAQS (in 40 CFR part 50 Appendix T) that, by comparison to the level of the NAAQS, 

indicates whether the area is violating the NAAQS.

3) Designated nonattainment area – an area which the EPA has determined has violated the 

2010 SO2 NAAQS or contributed to a violation in a nearby area. A nonattainment 

designation reflects considerations of state recommendations and all of the information 

discussed in this document. The EPA’s decision is based on all available information 

including the most recent 3 years of air quality monitoring data, available modeling 

analysis, and any other relevant information. 

4) Designated unclassifiable area – an area which the EPA cannot determine based on all 

available information whether or not it meets the 2010 SO2 NAAQS. 

5) Designated unclassifiable/attainment area – an area which the EPA has determined to 

have sufficient evidence to find either is attaining or is likely to be attaining the NAAQS.

The EPA’s decision is based on all available information including the most recent 3 

years of air quality monitoring data, available modeling analysis, and any other relevant 

information. 

6) Modeled violation – a violation based on air dispersion modeling.

7) Recommended attainment area – an area a state or tribe has recommended that the EPA 

designate as attainment. 

8) Recommended nonattainment area – an area a state or tribe has recommended that the 

EPA designate as nonattainment. 

9) Recommended unclassifiable area – an area a state or tribe has recommended that the 

EPA designate as unclassifiable.

10) Recommended unclassifiable/attainment area – an area a state or tribe has recommended 

that the EPA designate as unclassifiable/attainment.

11) Violating monitor – an ambient air monitor meeting all methods, quality assurance and 

siting criteria and requirements whose valid design value exceeds 75 ppb, based on data 

analysis conducted in accordance with Appendix T of 40 CFR part 50. 
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Technical Analysis for the Hawaii County, Hawaii Area

Introduction

In its May 2011 recommendation, the state recommended that all counties in the State of Hawaii

be designated as unclassifiable for the 2010 SO2 NAAQS, based on monitored air quality from 

2008-2010. After careful review of the state’s assessment, supporting documentation, and all 

available data including the EPA’s concurrence with an Exceptional Events package described in 

this document and included in the docket for this designation, the EPA intends to designate 

Hawaii County, Hawaii as unclassifiable/attainment for the 2010 SO2 NAAQS based upon data 

collected between 2012 and 2014. Our intended boundaries are consistent with the state’s 

recommended boundaries with respect to Hawaii County, consisting of the island of Hawaii. 

EPA is not designating other portions of the State of Hawaii in this round of designations.

As discussed in the EPA’s February 4, 2016 concurrence letter and accompanying technical 

support document, on December 17, 2015 HDOH submitted an exceptional events package

(“Hawaii’s 2012-2014 SO2 Exceptional Events package”). Hawaii’s 2012-2014 SO2 Exceptional 

Events package addresses 2012-2014 monitored exceedances of the 2010 SO2 NAAQS attributed 

to volcanic emissions on the Big Island of Hawaii (i.e. Hawaii County). The EPA concurred on 

the exceptional events requests; consequently, the monitored air quality data do not indicate any 

violation of the 2010 SO2 NAAQS in Hawaii County in calendar years 2012-2014. The 

documents related to Hawaii’s exceptional events request are included in the docket for this 

designations action. 

The figure below shows the EPA’s intended unclassifiable/attainment area boundary.
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Figure 1. The EPA’s intended unclassifiable/attainment area: Hawaii County, Hawaii 

Detailed Assessment

Air Quality Data

This factor considers the SO2 air quality monitoring data in Hawaii County. The table below 

shows information related to the regulatory monitors located in the County. 
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Table 2: Available Air Quality Data for Hawaii County

County State 

Recommendation

Air Quality 

Systems 

(AQS) 

Monitor ID

Site name Monitor Location 2012 – 2014 

SO2 Design 

Value (DV) 

in ppb*

Hawaii Unclassifiable 15-001-1006 Hilo 1099 Waianuenue 

Ave., Hilo

70

Hawaii Unclassifiable 15-001-2023 Mountain View 18-1235 Volcano 

Rd

72

Hawaii Unclassifiable 15-001-2020 Ocean View Orchid Parkway, 

Hawaiian Ocean 

View Estates

75

Hawaii Unclassifiable 15-001-2016 Pahala 96-3150 Pikake St. 75

Hawaii Unclassifiable 15-001-1012 Kona 81-1043 

Konawaena School 

Rd

47

Monitors in bold have the highest valid 2012 – 2014 design values in the county.

2014 design values from AQS Design Value Report pulled February 5, 2016.

*The 2012-2014 DV for Hilo, Mountain View, Ocean View, and Pahala were derived from data that excluded the 

exceptional events days and hours discussed above. Had those exceptional events not been excluded, the 2012-2014 

DV for these monitors would have been 180 ppb, 279 ppb, 533 ppb, and 712 ppb respectively.

The monitors listed in Table 2 are operated by HDOH in accordance with the EPA’s monitoring 

regulations in 40 CFR part 50, 40 CFR part 58, and associated appendices, and are regulatory 

monitors.

In addition, there are two non-regulatory monitors located at Hawaii Volcanoes National Park,

close to the summit of Kilauea Volcano (Visitor Center monitor, AQS ID: 15-001-0005; 

Observatory monitor, AQS ID: 15-001-0007). The Visitor Center and Observatory monitors had

2014 design values of 1,196 and 1,403 parts per billion (ppb), respectively, and are operated by 

the National Park Service (NPS). Exceptional events due to impacts from the volcano were not 

submitted for these monitors, as they are non-regulatory monitors and their design values are not 

appropriate for comparison to the NAAQS for regulatory purposes. An additional monitor, Puna 

E (AQS ID: 15-001-2010), which is not considered for regulatory use due to not meeting siting 

requirements of 40 CFR part 58 Appendix E, is located at 13-763 Leilani Avenue and had a 2014 

design value of 19 ppb.
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Based on available monitored ambient air quality data collected between 2012 and 2014 and 

consideration of exceptional events, the regulatory monitors in the Hawaii County do not 

indicate a violation of the 2010 SO2 NAAQS in calendar years 2012-2014. 

Emissions and Emissions-Related Data

As part of Hawaii’s 2012-2014 SO2 Exceptional Events package, Hawaii included the annual 

emissions for all SO2 point sources in Hawaii County, which are included below for 

informational purposes. As explained in Section 4.6.1 of Hawaii’s 2012-2014 SO2 Exceptional 

Events package, Hawaii obtained the data for these sources and their emissions from the yearly 

facility reports submitted to the state, permit requirements, or a mass balance calculation based 

on the fuel consumption and fuel sulfur content. These emissions data are summarized below. 

Table 3: SO2 Emissions at or above 100 tons per year (tpy) in Hawaii County

Facility Name City Facility Subject to 

the Emissions 

Criteria of the 

March 2, 2015 

consent decree?

Facility Total SO2 Emissions 

(Data source and tons per 

year)

HELCO Keahole Generating Station

(Keahole)

Kona No 2014 State Data – 100 tpy

HELCO Puna Generating Station

(Puna)

Hilo No 2014 State Data – 524 tpy

HELCO Kanoelehua Hill Generating 

Station (Hill)

Hilo No 2014 State Data - 1,852 tpy

Hawaii’s 2012-2014 SO2 Exceptional Events package (page 15) includes the figure shown below 

as Figure 2. Note that the figure shows the location of the non-regulatory Puna E monitor 

(operated by HDOH, listed as “DOH” in the figure) and the two non-regulatory NPS monitors, in 

addition to the five regulatory monitors listed in Table 2 and Figure 1 above. The figure depicts 

the power plants on the island, both those listed in Table 3, and those with emissions less than 

100 tpy in 2014: HELCO Shipman on the east side of the island, with 0 tpy; and HELCO 

Waimea on the north side of the island, with 0.01 tpy. Finally, it lists 2014 emissions from the 

Kilauea volcano: over two million tons of SO2 emissions from the Halema’uma’u summit vent, 

and approximately 135,000 tons from the Pu’u O’o eastern rift vent.
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Figure 2. Hawaii County: Monitors and SO2 Point Sources

Emissions Controls

Hawaii’s 2012-2014 SO2 Exceptional Events package provides information on controls required 

for anthropogenic sources on the island. The majority of anthropogenic SO2 emissions in Hawaii 

County are from three power plants: HELCO Kanoelehua Hill and HELCO Puna on the Hilo 

side of the island, and HELCO Keahole on the Kona side of the island. Regulations that apply to 

these sources and limit their SO2 emissions include Hawaii Administrative Rules (HAR), 
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Prevention of Significant Deterioration/Best Available Control Technology (PSD/BACT), New 

Source Performance Standards (NSPS), and National Emission Standards for Hazardous Air 

Pollutants (NESHAP). These regulations are further described in Hawaii’s 2012-2014 SO2

Exceptional Events package (Table 4-1, pages 85-86; Tables 4-20 and 4-22, pages 104, 106-

108).

Hawaii’s 2012-2014 SO2 Exceptional Events package also lists the existing control measures for 

limiting SO2 from these sources in Table 4-21 (page 105) and Table 4-23 (pages 108-109). These 

measures consist of limits on the maximum sulfur content of fuels utilized at the various units at 

the plants, as shown in Table 4.

Table 4: Control Measures for Largest Anthropogenic SO2 Sources in Hawaii County

Facility Unit Control Measure 

HELCO Puna 

Generating Station

15.5 megawatt (MW) 

boiler

maximum fuel sulfur content of 2% 

600 kilowatt (kW) 

diesel electric 

generator 

maximum fuel sulfur content of 0.5% 

20 MW combustion 

turbine

maximum fuel sulfur content of 0.4%

HELCO Kanoelehua

Hill Generating 

Station 

14.1 and 23 MW 

boilers

maximum fuel sulfur content of 2%

11.6 MW combustion 

turbine

maximum fuel sulfur content of 0.4%

One 2.0 and three 2.5 

MW diesel electric 

generators

maximum fuel sulfur content of 0.0015% 

(ultra-low-sulfur diesel)

HELCO Keahole 

Generating Station

One 500 kW Black 

Start diesel electric 

generators

maximum fuel sulfur content of 0.0015% 

(ultra-low-sulfur diesel)

Three 2.5 MW diesel 

electric generators

maximum fuel sulfur content of 0.0015% 

(ultra-low-sulfur diesel)

One 18 MW and two 

20 MW combustion 

turbines

maximum fuel sulfur content of 0.4%
12

The EPA has not received any additional information on emissions reductions resulting from 

controls put into place after the date of the emissions inventory data provided in Table 3 above. 

Future controls are discussed in the “Other Relevant Information” section of this document.

Meteorology (Weather & Transport Patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2 

concentrations in the surrounding area is another important factor in determining the appropriate 

extent of the EPA’s intended designated area. 

The island of Hawaii’s complex weather and transport patterns are influenced by its location in 

the Pacific Ocean as well as its topography. The northeasterly trade winds are the dominant wind 

regime for the island. In the summer, an area of high pressure called the Pacific High is at its 

northern-most position. This results in strong trade winds from the northeast dominating the 

wind regime from May to September. These trade winds flow from the northeast to the 

southwest of the island, and through the valley between Mauna Kea and Mauna Loa. While the 

trade wind regime still exists in winter months, it diminishes somewhat as the Pacific High 

moves south during winter months. Also during winter months, subtropical cyclones, called 

Kona storms, occur more frequently, bringing winds from the south. Often referred to as Kona 

winds, these winds travel from the southern side of the island, over Kilauea and northward 

toward the eastern coast. 

Figure 3, provided as part of Hawaii’s 2012-2014 SO2 Exceptional Events package, shows these 

wind patterns, peaks, and cities on the Big Island of Hawaii.

Figure 3: Hawaii County Wind Patterns
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Average rainfall varies drastically from the Kona side of the island to the Hilo side of the island. 

According to Hawaii’s 2012-2014 SO2 Exceptional Events package (page 12), the average 

rainfall on the Kona side was 9 inches from 2000 to 2011, while the Hilo side received 114 

inches of rain on average over the same time period. The lower flanks of Mauna Loa and Mauna 

Kea also receive higher amounts of rainfall.

Geography and Topography (Mountain Ranges or Other Air Basin Boundaries)

The island of Hawaii has complex terrain as well as complex meteorology, as shown above in 

Figure 3. The two largest peaks on the island are Mauna Loa and Mauna Kea. Both are over 

4,000 meters above sea level. The Kilauea volcano, located to the southeast of Mauna Loa, is 

1,247 meters in elevation. The relatively flat eastern portion of the island where Hilo is located 

contains the majority of the island’s population.

Jurisdictional Boundaries

Once the above factors were examined, existing jurisdictional boundaries were considered for 

the purpose of informing our intended unclassifiable/attainment area, specifically with respect to 

clearly defined legal boundaries.

There are no previously designated nonattainment areas within Hawaii County for the 2010 SO2

NAAQS. The area recommended by the State is comprised of clearly defined boundaries: the 

county of Hawaii, which consists of the island of Hawaii. The EPA finds these boundaries to be 

comprised of clearly defined legal boundaries, and to be a suitably clear basis for defining our 

intended unclassifiable/attainment area.

Other Relevant Information

Hawaii County’s SO2 situation is unique. In 2014, the volcano emitted a total of 2,140,187 tons 

of SO2 from the Halema’uma’u and Pu’u O’o vents, while all anthropogenic emissions together 

accounted for just 0.1% of total emissions released on the island.5 In response to health concerns 

associated with the levels of volcanic emissions, HDOH’s extensive network of SO2 monitors on 

the island and Hawaii’s short-term SO2 advisory webpage (developed with the EPA to provide 

Air Quality Index-type information for Hawaii County - available at http://hiso2index.info/ ) 

continuously provide alerts and health information to the public. The University of Hawaii also 

developed a model to forecast next-day concentrations downwind of the volcano (see 

http://mkwc.ifa.hawaii.edu/vmap/hysplit/ ).

The “Emissions Controls” section of this document describes controls in place when HDOH 

submitted Hawaii’s 2012-2014 SO2 Exceptional Events package. Additionally, under a Regional

Haze Federal Implementation Plan issued by the EPA, the boilers at Hill, Shipman and Puna 

power plants will be subject to a collective emissions cap of 3,550 tpy SO2 per year beginning in 

2018 (see 40 CFR 52.633(d)). Finally, the State of Hawaii is on an aggressive schedule to 

generate 100 percent of its electricity sales from renewable energy resources by 2045. In August 

2014, the Hawaiian Electric Companies submitted plans to the Hawaii Public Utilities 

 5 Hawaii’s 2012-2014 SO2 Exceptional Events package, pg 102-103.
14

Commission describing how electric utility services will be offered to meet customer needs and 

produce higher levels of renewable energy. Of the three power plants in/near Hilo (HELCO 

Shipman Power Plant, HELCO Puna Generating Station, and HELCO Hill Generating Station), 

Shipman is already deactivated and is anticipated for decommissioning. According to the August 

2014 Hawaii Electric Light Power Supply Improvement Plan6, the Puna facility will be 

deactivated in 2018 and decommissioned in 2020, while Hill 5 will be deactivated in 2018 and

decommissioned in 2022 and Hill 6 will be deactivated in 2022 and decommissioned in 2024. In 

total, emissions from power plants near Hilo are projected to decrease to a total of 1,852 tpy by 

2018, 1,148 tpy by 2020, and 0.2 tpy SO2 by 2022.7 In comparison, Hawaii Electric Company’s 

previous Integrated Resource Plan, finalized in 2008 prior to newer requirements and 

regulations, projected 2018 emissions from power plants near Hilo to be 4,996 tpy.8

While it is not possible for HDOH to site monitors such that they would not be affected by 

volcanic emissions, Hawaii’s 2012-2014 SO2 Exceptional Events package includes an analysis to 

evaluate the maximum SO2 concentration measurement resulting from emissions from the Hilo 

power plants. Figure 4 shows the sources and monitors near Hilo, Hawaii. Hawaii’s 2012-2014 

SO2 Exceptional Events package also includes distances between emission sources and the Hilo 

and Mountain View regulatory monitors. This information is provided in Table 5. The sources 

are 6.5 – 6.6 kilometers from the closest monitor.

 6 Available at http://files.hawaii.gov/puc/2_Dkt%202012-0212%202014-08-26%20HELCO%20PSIP%20Report.pdf 7 Hawaii’s 2012-2014 SO2 Exceptional Events package, pg 88. 8 “Technical Support Document for the Propose Action on the Federal Implementation Plan for the Regional Haze 

Program in the State of Hawaii”, U.S. EPA Region 9 Air Division. May 14, 2012, pg 57-58.
15

Figure 4. Sources and monitors near Hilo, Hawaii.9

Table 5. Distances from SO2 Sources to Regulatory Monitors, Hilo Area.

To Hilo monitor (AQS ID: 15-

001-1006) - in kilometers (km)

To Mountain View monitor (AQS ID: 

15-001-2023) - in kilometers (km)

HELCO Shipman Power 

Plant 4.6 km 16.3 km

HELCO Kanoelehua Hill 

Generating Station 6.5 km 13.5 km

HELCO Puna Generating 

Station 14.6 km 6.6 km

Halema'uma'u Vent 38.6 km 27.8 km

 9 Hawaii’s 2012-2014 SO2 Exceptional Events package, pg 35.
16

Section 3.2.5 of Hawaii’s 2012-2014 SO2 Exceptional Events package includes an analysis to 

evaluate the maximum SO2 concentration measurement consistent with emissions from the Hilo 

power plants. A detailed analysis for 2012-2014 that considers variables such as daily wind 

direction, daily average power generation data for the power plants, and monitored 

concentrations, found that the maximum concentration at Hilo resulting from non-summit 

volcanic emissions was 15.8 ppb, and 12.3 ppb at Mountain View. While Hawaii’s analysis 

excludes impacts from emissions coming directly from the summit of the volcano, the analysis 

was unable to separate potential impacts from power plant emissions and those from volcanic 

eastern rift emissions, or emissions from volcanic summit emissions that had been recirculated. It 

is therefore conservative to assume that anthropogenic sources alone would result in these 

maximum concentrations. As a result, the EPA finds it unlikely that the anthropogenic sources in 

the Hilo area caused or contributed to a monitored violation of the NAAQS within Hawaii 

County in calendar years 2012-2014. 

While not explicitly quantified in Hawaii’s exceptional events package, the EPA also finds it 

unlikely that emissions from HELCO Keahole Generating Station in Kona caused or contributed

to a monitored violation of the NAAQS in 2012-2014. As previously discussed, the 2012 – 2014 

design value at the Kona monitor (AQS ID: 15-001-1012) was 47 ppb. Given that 2014 

emissions from the Keahole Generating Station (100 tpy) were significantly less than those from 

either of the facilities in the Hilo area (524 and 1,852 tpy for Puna and Hill and respectively), the 

geographic location of the monitors and sources, and the previously discussed weather and 

transport patterns, the EPA does not believe that emissions from Keahole Generating Station 

caused or contributed to a monitored violation of the NAAQS at the Pahala, Ocean View, 

Mountain View, or Hilo monitors within Hawaii County in 2012-2014. 

The information presented above as produced by HDOH provides useful insight into the 

contribution to ambient concentrations from anthropogenic sources in Hawaii County. Hawaii 

County has a unique mix of complex meteorology, topography, and volcanic emissions that are 

levels of magnitude greater than all of the anthropogenic source emissions on the island 

combined. Consequently, although the EPA’s policy is to not generally rely exclusively on nonviolating monitored data to support an unclassifiable/attainment designation under the 2010 SO2

NAAQS (where there are significant sources of SO2 in the area), absent additional support in the 

form of either a demonstration that the relevant monitors are located in expected sites of 

maximum ambient concentrations or a confirming dispersion modeling analysis, the unique facts 

presented by Hawaii’s situation discussed above justify a state-specific departure from this 

general policy.

Conclusion

After carefully considering the factors described above, the EPA intends to designate Hawaii 

County, Hawaii as an unclassifiable/attainment area for the 2010 SO2 NAAQS. The boundaries 

for this area consist of the Big Island of Hawaii. We believe that these boundaries encompass the 

appropriate area based on the available information. 

At this time, our intended designations for the state only apply to this area. Consistent with the 

conditions in the March 2, 2015 court-ordered schedule, the EPA will evaluate and designate all 

remaining undesignated areas in Hawaii by either December 31, 2017, or December 31, 2020.