U.S. Environmental Protection Agency		

Region	9	

Summary of and Responses to Public Comments on Proposed Tribal Minor		

New Source Review Permit		

Navajo Generating Station – Refined Coal Treatment System Project

Tribal Minor NSR Permit: T‐0004‐NN

Prepared By:		Larry Maurin

Reviewed By:		Gerardo Rios

April 2016

	 	

   
NGS RCTS Project

Response to Comments

Page 2 of 12

1. Introduction – Summary of the Formal Public Participation Process

On February 2nd, 2016, the U.S. Environmental Protection Agency (EPA), Region 9 provided notice of, and

requested public comment on, Region 9’s proposed permit to allow construction of a Refined Coal Treatment

System at the Navajo Generating Station (hereinafter “NGS RCTS Project”). Region 9 also requested public

comment on our finding that the NGS RCTS Project would have no effect on any historic properties or cultural

resources pursuant to Section 106 of the National Historic Preservation Act. The public comment period on

the proposed permit for the FCPP SCR Project began on February 2nd, 2016 and closed on March 7th, 2016.

Region 9 announced the public comment period through public notices published in the Lake Powell Chronicle

on February 3rd, 2016 and the Navajo Times on February 4th, 2016. Region 9 also distributed the public notices

to the necessary parties in accordance with 40 CFR part 49.157, including notices sent by mail and email on

February 2nd, 2016. Parties notified by Region 9 included agencies, organizations, and public members for

whom contact information was obtained through a number of different methods, including requests made

directly to Region 9 through Region 9’s website, contacts provided by the Navajo Nation Environmental

Protection Agency (NNEPA), and other parties known to Region 9 who may have an interest in this action

based on their interest in previous actions within the Navajo Nation.

The administrative record for our proposed permit for the NGS RCTS Project was made available at EPA Region

9’s office. Region 9 also made the proposed permit, the Technical Support Document, and most of the other

supporting documents in the administrative record available through Region 9’s website. Region 9 made the

key documents available at: Page Public Library in Page, AZ, the Navajo Nation Environmental Protection

Agency Operating Permit Program Offices in Fort Defiance, AZ, and at the LeChee Chapter House in LeChee,

AZ.

EPA did not hold a public hearing concerning the proposed permit. Any person had the opportunity to request

a public hearing, however, no requests for a public hearing were received by EPA. During the public comment

period EPA received several comment letters on the draft permit by email. Only one commenter submitted

comments on EPA’s finding that there would be no effect on any historic properties or cultural resources.

Timely comments received equal weight, regardless of the method used to submit them. We provide our

response to the comments we received below.

2. Region 9’s Response to Public Comments

This section excerpts the significant public comments received by EPA during the February‐March 2016 public

comment period. Our responses to all significant comments made during the public comment period are

provided following each comment. This document also includes an explanation of what changes have been

made in the Final Permit as a result of those comments – see additional information in Section 3. In some

instances similar comments are grouped together by topic into one comment summary, and addressed by one

EPA response. The full text of all public comments and many other documents relevant to the permit are

available through a link at our website, https://www.epa.gov/caa‐permitting/tribal‐nsr‐permits‐region‐9, or at

www.regulations.gov (Docket ID EPA‐R09‐OAR‐2016‐0026).
NGS RCTS Project

Response to Comments

Page 3 of 12

Comments on the Proposed Minor New Source Review Permit for the Navajo Generating Station

Refined Coal Treatment System Project

Commenters:

Written commenters on draft permit

 Mary Altmann

 Kenneth Joe Frazier, Salt River Project

 Loriel Golden

 Nathan Miller, National Parks Conservation Association

 Vincent H. Yazzie

 Shawn Dolan, Virtual Technology LLC

 Unidentified Commenter who submitted a comment directly to the docket without identification

Written commenters on EPA’s finding under Section 106 of the National Historic Preservation Act

 Unidentified Commenter who submitted a comment directly to the docket without identification

1.

Exclusion of NGS RCTS Project from 2014 BART FIP

Comment 1:

(Commenter: Nathan Miller, National Parks Conservation Association)

The commenter is concerned that the NGS RCTS Project was not considered as part of the 2014 Best Available

Retrofit Technology (BART) Federal Implementation Plan (FIP) for NOx control at NGS:

It is our understanding that the refined coal treatment system (RCTS) is anticipated to result in reduced

nitrogen oxides (NOx) emissions from NGS. We question why this option was not considered as part of the

recent determination for best available retrofit technologies (BART) for NOx control under the regional haze

program, since it appears that RCTS is not a new control technique. We maintain that selective catalytic

reduction is the appropriate NOx control for these units and should be required through the regional haze

program.  

The commenter finds it problematic that a project which will lead to further NOx reductions is being proposed

so soon after the BART determination:

Although we do not agree that the NOx “cap” set up under the BART determination is an appropriate or legal

alternative to BART, if it is used going forward, we ask EPA to re‐calculate and lower the cap, which was based

on anticipated future NOx emissions from the facility. We note that without this step, NGS will be able to

continue to operate under the NOx “cap” for longer than was previously advertised. For that reason, we find it

problematic that this proposal comes shortly after the final BART determination, and request information

about any other NOx reduction projects at NGS that SRP has submitted applications for.

The commenter also believes that EPA should require NGS to operate the RCTS permanently, even if the

federal tax credit for the operation of the RCTS expires at some point in the future:

The materials in the docket also indicate that SRP does not have plans to permanently operate the RCTS, but

rather anticipates dismantling it when the associated federal tax credit is no longer available. If the RCTS
NGS RCTS Project

Response to Comments

Page 4 of 12

provides an overall benefit to visibility, we ask that EPA require NGS to continue use it as part of the regional

haze program regardless of the availability of the federal tax credit.

Response 1:

In February 2013, EPA published a Notice of Proposed Rulemaking (NPRM) providing our analysis of the

emission limitation for NOx that would represent the Best Available Retrofit Technology (BART) for the 3 coal‐

fired electrical generating units (EGUs) at NGS. The EGUs were “BART‐eligible” and “subject to BART” because

they met the statutory and regulatory criteria in Section 169A of the Clean Air Act and 40 CFR 51.308. Because

the 3 EGUs were BART‐eligible and subject to BART, we conducted a 5‐factor analysis consistent with EPA’s

BART Guidelines. We proposed an emission limitation of 0.055 lb NOx/MMBtu for each of the EGUs operating

at NGS. 78 Fed. Reg. 8274, 8293 (Feb. 5, 2013). The NPRM also set forth a “Better than BART” alternative that

would result in greater overall NOx emission reductions but provided more time for installation of controls. Id.

at 8288‐8291. EPA received an additional suggested alternative for complying with the BART emission limit,

calculated as plant‐wide cap, from the Technical Work Group (TWG) in July 2013.  In October 2013, EPA

published a Supplemental NPRM analyzing the TWG Alternative and proposing regulations that were generally

consistent with that alternative. The requirements put forth in the Supplemental NPRM would achieve greater

NOx emission reductions calculated as a plant‐wide cap than would have been achieved with the NOx BART

emission limit of 0.055 lb/MMBtu at each of the 3 EGUs. 78 Fed. Reg. 62509, 62517‐18 (Oct. 22, 2013). EPA

received substantial comments on our NPRM and Supplemental NPRM, including oral comments received

during 5 public hearings on the reservation lands of the Navajo Nation and Hopi Tribe, and in Arizona. EPA

responded to these comments and published our Notice of Final Rulemaking (NFRM) on August 8, 2014. Our

final rule required NGS to comply with the regulations that were largely consistent with the provisions in

Supplemental NPRM. 79 Fed. Red. 46514 (Aug. 8, 2014).  

EPA disagrees with the comment that EPA should have considered the RCTS during its NOx BART rulemaking,

and that EPA should “re‐calculate” and lower the cap taking into consideration the RCTS.  EPA’s proposed

BART determination for NGS was based on a review of NOx control technologies that were widely available

and rejected technologies that were not achieved in practice. The commenter has not supported the

contention that the RCTS technology was readily available and achieved in practice in 2013 when EPA was

considering BART for NGS.  In addition, the commenter has not provided any information to show that the

NOx BART emission limit for the NGS EGUs could have been lower than 0.055 lb/MMBtu if EPA had considered

the RCTS in 2013.

The commenter also speculates that if EPA does not recalculate a lower 2009‐2044 NOx Cap “NGS will be able

to continue to operate under the NOx ‘cap’ for longer than was previously advertised.” But this statement

ignores the final BART rule that requires: “By December 22, 2044, the owner/operator shall permanently

cease conventional coal‐fired electricity generation by all coal‐fired Units at NGS.”  40 CFR 49.5513(J)(3)(iii).

This requirement is independent of meeting the NOx Cap. NGS must also comply with the specific dates in

each of the Alternatives in addition to meeting the NOx Cap. Therefore, the commenter’s concern that NGS

will be able to continue to operate beyond the timeframe of the NOx cap (i.e., 2044) is unfounded. The final

rule included several alternatives, each of which depended on the final ownership structure of NGS. See 40

CFR 49.5513(J)(2)((vi)(definition of “Departing Participant”) and 49.5513(J)(3)(i)(B) – (D)(Alternatives A1 – B).

All of the Alternatives in the final BART rule require NGS to meet the 2009 – 2044 NOx Cap. Id. at

49.5513(J)(3).  Regarding the commenter’s concern about time periods of operation, we further note that

each of the Alternatives requires specific actions by a date certain. For example, Alternative A1 requires NGS

to cease operation of one EGU by December 31, 2019 and to comply with a NOx emission limit of 0.07
NGS RCTS Project

Response to Comments

Page 5 of 12

lb/MMBtu by December 31, 2030 at the remaining EGUs. Id. at 40 CFR 49.5513(J)(3)(i)(A). The actions specific

to the EGUs are required in addition to the requirement for NGS to meet its plant‐wide “Better than BART”

2009 ‐2044 NOx Cap, and the requirement to cease conventional coal fired operation by December 22, 2044.

The comment further asserts that EPA should require NGS to operate the RCTS permanently.  This permit and

the applicable FIPs establish emission limits that NGS must continue to meet whether or not the RCTS is

operated permanently. Therefore, the commenter has not established that there would be any additional air

emissions even if operation of the RCTS is discontinued at some point in the future.  In summary, EPA

disagrees with the comment suggesting that the permit should be amended or revised to require permanent

operation of the RCTS.

Coal Power and Climate Change

Comment 2:

(Commenters: Mary Altmann, Loriel Golden)

Commenters believe that coal‐burning power plants such as NGS contribute to climate change and

environmental impacts, as excerpted below:

Please observe that the Earth is in climate catastrophe now and cannot take one more coal burning effort,

whether on Indian land or anywhere else. It is high time to respect the true needs of the Earth, and all forms of

life, and stop doing things that destroy Earth’s ability to function. Thank you for taking Life on Earth and your

own children's needs seriously by refusing to build any form of energy use that destroys life.  

Please say "no" to new coal permits. We can see first‐hand the devastating effects to our water, air, and

quality of life.

Response 2:

The EPA appreciates the commenters’ concerns regarding climate change, and would like to point out that

EPA has finalized the Clean Power Plan to address greenhouse gases from existing coal‐fired power plants.

That action is currently stayed by the Supreme Court pending judicial review. However, this permitting action

is related to emissions of particulate matter (PM and PM10). The NGS RCTS Project is not subject to review

under the Tribal NSR program for greenhouse gas emissions, the group of pollutants that contribute to climate

change. The only pollutants subject to the Tribal NSR regulations for the NGS RCTS Project are PM and PM10.

Furthermore, there are no changes in the allowable emissions for any other pollutants due to the RCTS Project

at NGS.

For more information regarding EPA’s actions related to carbon pollution from existing power plants please

visit: http://www2.epa.gov/carbon‐pollution‐standards.

EPA understands that coal combustion can have adverse effects on air and water quality. NGS is an existing

facility that was constructed over 1974‐1976 and this action does not authorize the construction of a new

coal‐fired power plant. The minor NSR permit currently under review for the NGS RCTS Project also does not

authorize any expansion of the existing capacity for NGS to combust coal. The coal consumption rates are not

expected to change as a result of the RCTS Project and NGS must comply with all applicable emission limits in

the current title V permit and PSD Permit AZ 08‐01A. None of the allowable emission limits for existing

equipment are under review for this proposed action.
NGS RCTS Project

Response to Comments

Page 6 of 12

EPA has previously promulgated two Federal Implementation Plans (FIPs) regulating NGS pursuant to other

authority in the CAA. See 40 CFR 49.5513(a) ‐ (i) and 75 FR 10174 for more information. As discussed above, in

2014, EPA finalized another FIP that included regulations requiring reductions in NOx emissions as a “better‐

than‐BART” alternative under the Regional Haze Rule to improve visibility in surrounding federal Class I areas.

See 40 CFR 49.5513(j) and 79 FR 46514 (Aug 8, 2014) In 2012, EPA finalized the Mercury and Air Toxics

Standards Rule (MATS) Rule which placed more stringent mercury emission standards on power plants. In

April 2016, NGS expects to begin operating a Mercury Control System to ensure compliance with the mercury

emissions standards in the MATS rule.

All of these emissions limits remain applicable to NGS.

Effects of Carbon Monoxide Emissions on Human Health

Comment 3:

(Commenters: Vincent H. Yazzie)

One commenter was concerned about the effects of carbon monoxide (CO) emissions from NGS and their

effects on human health around Lake Powell, as excerpted below:

Carbon monoxide emissions from houseboats have created dangerous pockets of carbon monoxide levels near

the water elevation. Any Navajo Generating Station (NGS) carbon monoxide emissions that settle at the lake

elevation will add to the localized house boat emissions under calm conditions.

Any NGS carbon monoxide that descends to the lake level will add to localized house boat carbon monoxide

emissions creating a dangerous condition for people at the surface of the lake.

Carbon monoxide and carbon dioxide air monitoring stations must be setup throughout Lake Powell.

Low NOX burners need to be shut off and SCR installed.

Lake Powell between 1990 and 2009 had 211 CO poisonings.

Navajo Generating Station (NGS) would worsen the carbon monoxide (CO) levels at Lake Powell.

Deny Salt River Project (SRP) permit for NGS due to additional CO that will worsen existing adverse

environmental and human public health conditions.

Response 3:

The EPA appreciates the commenter’s concerns over possible health impacts of high carbon monoxide (CO)

levels on Lake Powell. The NGS RCTS Project is not subject to review under the Tribal NSR program for CO

emissions, so the comments are outside the scope of the proposed permit action. Cement Kiln Dust acts as a

sorbent and has no expected effect on flame temperature or thermal NOx or CO production from combustion

of coal. Therefore, the NGS RCTS Project is not expected to increase emissions of CO at NGS.

Furthermore, PSD Permit AZ 08‐01A, which authorized the installation of Low‐NOx burners on Units 1, 2, and 3

is not currently up for review or public comment under this proposed Tribal Minor NSR permit action. The
NGS RCTS Project

Response to Comments

Page 7 of 12

Low‐NOx burners are outside the scope of this permitting action. NGS must comply with the current CO limits

in Condition IX.B.1 of PSD Permit AZ 08‐01A, as they remain unchanged and in effect, and are protective of

public health.  

Use of Calcium Bromide and Formation of Trihalomethanes (THM)

Comment 4:

(Commenter: Vincent H. Yazzie)

Commenter expressed concerns that the addition of calcium bromide to coal as a result of the NGS RCTS

Project would lead to the formation of trihalomethanes (THM) in the local drinking water supply:

SRP has not adequately studied possible rises in trihalomethanes (THM) in the water when calcium bromide is

used like when Duke Energy stopped used calcium bromide due to increased THM in the water. THM will have

an adverse impact to the local population and minority groups.

Response 4:

Trihalomethanes (THM) are a carcinogenic by‐product that forms when bromide‐containing wastewater is

exposed to drinking water which employs chlorine as a disinfectant. It appears the commenter is concerned

that there is potential for the bromides produced from the combustion of coal treated with calcium bromide

to enter the local drinking water supply. This is unlikely given the configuration at the plant.

Wet scrubbers have a high capacity for capturing acid gases and halogenic compounds in flue gas including

bromides and chlorides. Unlike the Belews Creek Power Station, owned by Duke Energy, in Belews Creek,

North Carolina, NGS employs a Zero Liquid Discharge system for wastewater originating from the cooling

towers and wet scrubbers. The wastewater is distilled on site for reuse within the plant. The solid distillates

from the scrubber wastewater are then landfilled on site along with other coal combustion residuals (CCR)

from the plant.

EPA’s Final Rule for Disposal of Coal Combustion Residuals from Electric Utilities, which became effective on

October 19, 2015, requires more stringent standards for impoundment of CCR to prevent the leakage of

contamination into surface water and groundwater. It also requires groundwater monitoring surrounding CCR

impoundments to detect the presence of hazardous constituents released from these units. Furthermore, the

standards in the final CCR Rule ensure low risk associated with the interception of any groundwater

contamination plume by surface water bodies (See 80 Fed. Reg. 21322). For more information on the Coal

Combustion Residuals Disposal Rule visit: https://www.epa.gov/coalash

Concerns that EPA Methods 9 and 22 are Not Adequate for Opacity Measurements

Comment 5:

(Commenter: Shawn Dolan, Virtual Technology LLC)

Commenter expressed concerns that EPA Test Methods 9 and 22 are not adequate for accurate measurement

of opacity. The commenter expressed that the permit should be revised to require that NGS use Alternative

Method 082 – Digital Camera Opacity Technique (DCOT) to measure visible emissions:

Facility Operation should be amended to support the review of imagery associated with opacity observations

performed in support of all opacity limits with the permit and facility.
NGS RCTS Project

Response to Comments

Page 8 of 12

X‐A.4 and 5 should be changed to include the use of EPA Alternative Method 082 (Digital Camera Opacity

Technique (DCOT)) for the monitoring of visible emission.

A‐B.4 and 5 and 8 should be changed to include the use of EPA Alternative Method 082 (Digital Camera

Opacity Technique (DCOT)) for the monitoring of visible emission.

EPA Alternative Method 082 has been determined in the Ferro Alloy NESHAP final rule as BACT for opacity

measurement, this is a BACT driven permit and thus should include BACT for all monitoring requirements unless

BACT is cost prohibitive. Given the cost to maintain Method 9 certification in Page Arizona the use of EPA

Alternative Method 082 would be less expensive, more reliable and repeatable than Method 9. Further,

imagery from camera used to perform EPA Alternative Method 082 opacity observations could be posted to

public web sites for community relations improvement.

Experience: Being a native of Arizona I have spent a great amount of time boating on Lake Powell. I have notice

coal dust, road dust, and excessive emission from the NGS facility. Given that camera based technology exists,

is certified as BACT for opacity, and is cost effective, I do not believe any permit should be promulgated without

its requirement. Methods, 22 and 9 are very subjective legacy methods and COMS are not representative of the

exit opacity values. I have personal witnessed secondary formations from NGS that significantly exceed the

stack exit opacity (measured beyond the condensed water vapor). I have witnessed coal dust emissions at

opacities greater than 60% hundreds of feet in the air and at water level in the lake Powell main channel just

north of Antelope Point marina.

Response 5:

EPA has determined that Methods 9 and 22 are adequate for monitoring the increases in emissions of

particulate matter from the NGS RCTS Project. The PM and PM10 emission increases which are expected from

the RCTS Project are minor as defined in 40 CFR Part 49.152. Furthermore, EPA Method 9 is currently in use at

NGS for most of the other emission points at the facility that release any amount of particulate matter

including the main stacks, coal handling operations, fly ash and soda ash storage, and lime storage silos. The

opacity limits and method of opacity measurements for these other operations at NGS are not up for review in

this proposed minor NSR permit. For these reasons, EPA does not consider Alternative Method 082 – Digital

Camera Opacity Technique (DCOT) – to be appropriate for implementation at the NGS facility solely for the

particulate matter emission increases due to the RCTS Project.  

With respect to secondary formations from NGS that significantly exceed the stack exit opacity, the stack

opacity limits or the method by which stack exit opacity is measured is not up for review under this minor NSR

permit action. Coal dust emissions from existing coal handling and storage facilities, fly ash and storage, road

sweeping activities, crushers, grinding mills, screening operations, belt conveyors, truck loading or unloading

operations, or railcar unloading stations are also outside the project scope of this minor NSR permit action.

NGS is expected to comply with all opacity limits and control measures in the 2010 source‐specific FIP codified

at 40 CFR 49.5513(d).

Stack Height at NGS

Comment 6:

(Commenter: Vincent H. Yazzie)

Comment below expresses concerns that the height of the stacks at NGS are not adequate to protect human

health of minority populations in LeChee, Arizona:
NGS RCTS Project

Response to Comments

Page 9 of 12

Navajo Generating Station (NGS) is 4,376 feet above mean sea level (MSL). Page, Arizona is at an elevation of

4,337 feet above MSL and 3.83 miles bearing of 286 degrees from NGS. Page, AZ is 39 feet below NGS.

LeChee, Arizona is at an elevation of 4,786 feet high above MSL. LeChee, AZ is 4.87 miles from NGS at a bearing

of 223 degrees from true north. LeChee, Arizona is 410 feet high above NGS.

The flue stack at NGS is 775 high for a flue elevation of 5,151 feet high. The flue stack is 814 feet above Page,

Arizona. The flue stack is 365 feet above LeChee, Arizona.

LeChee, Arizona is a Navajo ghetto in the shadow of the NGS smoke stacks. Navajos are a minority population.

Minority populations are closer to flue stacks than the people of Page, AZ in terms of elevation. The flue stacks

need to be 430 meters high instead of 775 feet.

Response 6:

The EPA appreciates the commenter’s concerns over the stack height at NGS. The NGS RCTS Project will not

impact the National Ambient Air Quality Standards (NAAQS), and the emissions do not exceed the PM10

Significant Impact Limits (SILs) outside the facility fence line (see Technical Support Document for Permit T‐

0004‐NN). SILs indicate the impact level at which emissions of a pollutant from a proposed source or project

are likely to impact ambient air quality. The NAAQS are standards above which any ambient pollutant

concentrations are expected to have significant impacts on human health.  

In our analysis, EPA considered what control technology would be appropriate for the NGS RCTS Project. The

majority of emission increases from the NGS RCTS Project do not pass through the stacks, but rather are

controlled by separate baghouses or dust collectors or originate as fugitive dust emissions from unpaved

roads. The commenter has not demonstrated that raising the stack height at NGS would decrease the

potential impacts from the RCTS Project. Pursuant to 40 CFR 49.154(c)(5), emission limits may not rely on

stack heights above good engineering practice. The stack height at NGS are required to meet good engineering

practice as defined by 40 CFR 51.100, and therefore, the emissions increases due to the RCTS Project must be

evaluated based on control technology. The existing Electrostatic Precipitators (ESPs) remain the most

effective control technology for reducing PM emissions from flue gas. Particulate matter discharge limits and

opacity limits from the main stacks remain in place, pursuant to the 2010 NGS FIP (See 40 CFR 49.5513(d)) and

the Mercury and Air Toxics Standards (MATS) Rule.

Effects of Dust on Lake Powell and Glen Canyon National Recreation Area

Comment 7:

(Commenter: Unidentified Commenter who submitted a comment directly to the docket without

identification)

Commenter expresses concerns on the effects from dust emissions of the NGS RCTS Project on Lake Powell

and Glen Canyon National Recreation Area. The commenter agreed with EPA’s determination that the NGS

RCTS Project would have no effect on historic properties under Section 106 of the National Historic

Preservation Act:

Agree this modification will not affect historical buildings but it will affect the Lake Powell National Park with

dust emission.
NGS RCTS Project

Response to Comments

Page 10 of 12

Response 7:

The EPA understands the commenter’s concerns over the possible impacts of dust emissions on the

surrounding area, most notably on Lake Powell and the Glen Canyon National Recreation Area. The NGS RCTS

Project will not impact the National Ambient Air Quality Standards (NAAQS), and the emissions do not exceed

the PM10 Significant Impact Limits (SILs) outside the facility fence line (see Technical Support Document for

Permit T‐0004‐NN). Under this action EPA is also required to review and receive public comment on the

potential impacts due to emission increases from the RCTS Project on any historic properties or cultural

resources pursuant to Section 106 of the National Historic Preservation Act (NHPA). EPA is aware that historic

properties or cultural resources may exist in and around Lake Powell and Glen Canyon National Recreation

Area. However, as stated in a letter to the Navajo Nation Historic Preservation Department dated October 23,

2015, due to the fact that the emissions increases at NGS do not exceed the SILs for any pollutant, there will

be no effects due to the RCTS Project on any historic properties or cultural resources which may exist outside

the NGS facility footprint.

Fugitive Dust Control on Roadways

Comment 8:

(Commenters: Kenneth Joe Frazier, Salt River Project)

Proposed Permit Condition X.A.4: The dust on the site roadways shall be controlled by applications of water

such that visible fugitive dust emissions do not exceed 20 percent opacity. Roadways shall be swept as needed

between applications of water.

Salt River Project expressed concern that proposed permit condition X.A.4 limits NGS to controlling fugitive

dust emissions from roadways with water applications or sweeping. SRP would like for permit condition X.A.4

to provide additional flexibility for measures which may be used to control fugitive dust emissions from

roadways.

SRP recommends a revision to the draft permit language to provide additional flexibility in the measures that

may be used to control dust on the roadways used to transport treatment chemicals. Permit language is

suggested to be revised as follows: “The dust on the site roadways shall be controlled by the application of

water, dust suppressants, or an alternative control measure such that visible dust emissions do not exceed 20

percent opacity.”

Response 8:

EPA agrees that NGS should be allowed more flexibility to control fugitive dust emissions from roadways as

necessary to meet all applicable emission limits. According to the Dust Control Plan included as an attachment

to the most recently proposed title V permit renewal, NGS uses a variety of methods as standard practice for

control of fugitive dust emissions from roadways including application of water and chemical dust

suppressants, surface graveling, speed reduction, and limits on traffic. There are some periods when

applications of water on roadways for dust control may not be appropriate due to hazardous weather

conditions. It is industry standard to use chemical dust suppressants, such as calcium chloride or magnesium

chloride, as stabilizer to help minimize fugitive dust emissions from unpaved roads. In addition, because it is

not the facility’s practice to sweep unpaved roads, the requirement to sweep roads between applications of

dust suppressant may be removed from Condition X.A.4. The access roads which will be used to deliver
NGS RCTS Project

Response to Comments

Page 11 of 12

calcium bromide and cement kiln dust to the RCTS are unpaved roads, and thus, do not require sweeping. EPA

is revising Permit Condition X.A.4 be revised as follows:

“The dust on the site roadways shall be controlled such that visible emissions of fugitive dust do not exceed 20

percent opacity. The Permittee may use applications of water, chemical dust suppressants, or gravel to control

dust from site roadways.”

The Equipment Description table in the permit has been updated accordingly. We are also revising Condition

X.B.7 so that it contains recordkeeping requirements for any application of chemical dust suppressants or

gravel on unpaved roadways as follows:

“The Permittee shall maintain records of the date and time of any road watering or application of chemical

dust suppressants or gravel performed.”

  

Opacity Limit for NGS RCTS Project Equipment

Comment 9:

(Commenters: Kenneth Joe Frazier, Salt River Project)

Proposed Permit Condition X.B.4: At least once during each calendar week the Permittee shall perform a

visible emissions survey for each PAC Silo (Silos A and B), Dust Collectors DC‐12 and DC‐13, Cement Kiln Dust

Storage Silos (DC‐14 through DC‐16), and Cement Kiln Dust Day Bins (DC‐17 and DC‐18). The survey shall be

performed during daylight hours by an individual trained in EPA Method 22 while the equipment is in

operation. If visible emissions are detected during the survey, the permittee shall take corrective action so

that within 24 hours no visible emissions are detected.

The commenter expresses concern that proposed permit condition X.B.4 implies that the listed emission units

have an opacity limit of zero. The commenter is concerned that a zero percent opacity limit is impractical and

more stringent than the New Source Performance Standards for similar sources:

The current title V operating permit for NGS requires dust emissions from similar coal handling sources to be

maintained below 20 percent opacity as determined by a certified EPA Reference Method 9 observer. SRP

recommends a similar condition be included for the refined coal and PAC systems.

Response 9:

EPA understands the applicant’s concern that Condition X.B.4 implies that the listed emission units have an

opacity limit of zero. Our intent was not to impose a zero opacity limit. Inclusion of an opacity limit is

consistent with other permits issued by EPA under the Tribal NSR program for material handling equipment.

We have revised Condition X.B.4 to include an opacity limit of seven percent for the control equipment

associated with the refined coal and PAC systems. This limit is consistent with the limit imposed on similar

equipment covered by 40 CFR 60 Subpart OOO – Standards of Performance for Nonmetallic Mineral

Processing (see Table 2 of 40 CFR 60 Subpart OOO).

We maintain that EPA Method 22 remains useful as a tool for detection of visible emissions, and can prevent

the need for a Method 9 observation to be conducted at the equipment on a weekly basis. Additionally, five

percent is the lowest opacity measureable by any Method 9 observer. If any emissions are visible from the
NGS RCTS Project

Response to Comments

Page 12 of 12

emissions equipment, the opacity of the emissions should be rated at a minimum of five percent. We are

revising Condition X.B.4 as follows:

“At least once during each calendar week the Permittee shall perform a visible emissions survey for each PAC

Silo (Silos A and B), Dust Collectors DC‐12 and DC‐13, Cement Kiln Dust Storage Silos (DC‐14 through DC‐16),

and Cement Kiln Dust Day Bins (DC‐17 and DC‐18). The survey shall be performed during daylight hours by an

individual trained in EPA Method 22 while the equipment is in operation. If visible emissions are detected

during the survey, the permittee shall perform a 6‐minute EPA Method 9 observation. If visible emissions

during the 6‐minute EPA Method 9 observation exceed 7 percent opacity, the Permittee shall take corrective

action so that within 24 hours no visible emissions are detected.”

3. Final Revised Tribal Minor NSR Permit No. T‐0004‐NN

After careful review of the comments submitted and consideration of the views expressed by the

commenters, the pertinent Federal statutes and regulations, and additional material relevant to the applicant

and contained in our administrative record, Region 9 is issuing a decision pursuant to 40 CFR 49.151‐161 to

issue a final permit to NGS for the RCTS Project. Region 9’s consideration of the comments received during the

February‐March 2016 public comment period resulted in several changes to the Final Permit. For the purpose

of clarity, we have created an unofficial redline/strikeout version of the final permit that shows the changes

made to the permit since proposal. In addition to the changes described in our responses we also made

updates to the permit cover page to correct the procedure under which the Final Permit will be issued and the

effective date of the Final Permit, which can be seen in the unofficial reline/strikeout version.