UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, D.C. 20460

OFFICE OF


AIR AND RADIATION 

The Honorable Kevin McCarthy 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman McCarthy: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Administrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional event" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf 

We recognize the importance of this issue for California and its local air districts and the progress you 

have made in protecting your citizens from the harmful effects of air pollution. We have been working 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (APCD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory problems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution can have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires the EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect human health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, volcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the control of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of these eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lack of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decisions, the 

EPA believes that some drought-related exceedances and violations may be considered for exclusion 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule." For 

example, the EPA believes that an air agency can submit evidence showing that a severe drought 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation, etc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be considered 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which would need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate specific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http://www.epa.gov 


Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
Again, thank you for your letter. If you have further questions, please contact me or your staff may 

contact Josh Lewis in the EPA's Office of Congressional and Intergovernmental Relations at 

lewis.joshepa.gov or (202) 564-2095.

Sincerely, 

_,_l*	

.q-i-' 

Janet G. McCabe 

Acting Assistant Administrator
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 


WASHINGTON, D.C. 20460

OFFICE OF


AIR AND RDIATION 

The Honorable Devin Nunes 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman Nunes: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Admiiiiistrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional evnt" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf. 

We recognize the importance of this issue for California and its local air districts and the progress you 

have made in protecting your citizens from the harmful effects of air pollution. We have been orking 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (A?CD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory piioblems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution cart have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires th EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect humai health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, volcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the control of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of these eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lack of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decisions, the 

EPA believes that some drought-related exceedances and violations may be considered for exclusion 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule." 1'or 

example, the EPA believes that an air agency can submit evidence showing that a severe droug1t 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation, tc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be considered 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which woild need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate spcific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http:I/www.epa.gov 


Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
Again, thank you for your letter. If you have further questions, please contact me or your staff may 

contact Josh Lewis in the EPA's Office of Congressional and Intergovernmental Relations at 

lewis.joshepa.gov or (202) 564-2095.

Janet G. McCabe 

Acting Assistant Administrator
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, D.C. 20460

OFFIC OF


AIR AND RDIATION 

The Honorable Jeff Denham 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman Denham: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Administrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional event" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf 

We recognize the importance of this issue for California and its local air districts and the progress you 

have made in protecting your citizens from the harmful effects of air pollution. We have been 4'orking 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (APCD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory problems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution can have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires th EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect human health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, volcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the coiitrol of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of these eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lack of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decisins, the 

EPA believes that some drought-related exceedances and violations may be considered for excl.ision 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule." or 

example, the EPA believes that an air. agency can submit evidence showing that a severe drouglt 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation, etc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be considered 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which wuld need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate spcific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http://www.epa.gov 


Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
Again, thank you for your letter. If you have further questions, please contact me or your staff mafr 

contact Josh Lewis in the EPA' s Office of Congressional and Intergovernmental Relations at 

1ewis.joshepa.gov or (202) 564-2095.

Sincerely, 

Janet G. McCabe 

Acting Assistant Administrator
OFFIC OF


AIR AND R4DIATION 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, D.C. 20460

The Honorable David G. Valadao 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman Valadao: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Admiitiistrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional evnt" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf. 

We recognize the importance of this issue for California and its local air districts and the progress you 

have made in protecting your citizens from the harmful effects of air pollution. We have been orking 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (A?CD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory pioblems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution can have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires the EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect humai health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, vçilcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the conjtrol of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of these eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lack of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decisions, the 

EPA believes that some drought-related exceedances and violations may be considered for excii4sion 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule." ifor 

example, the EPA believes that an air agency can submit evidence showing that a severe drought 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation, tc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be considred 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which wo4ild need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate spcific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http:/Iwww.epagov


Recycled/Recyclable I Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
Again, thank you for your letter. If you have further questions, please contact me or your staff my 

contact Josh Lewis in the EPA's Office of Congressional and Intergovernmental Relations at 

lewis.josh@epa.gov or (202) 564-2095.

Janet G. McCabe 

Acting Assistant Administrator
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, DC. 20460

OFFIC OF


AIR AND RADIATION 

The Honorable Jim Costa 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman Costa: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Admi*istrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional evnt" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf. 

We recognize the importance of this issue for California and its local air districts and the progres you 

have made in protecting your citizens from the harmful effects of air pollution. We have been wrking 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (ACD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory problems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution cai have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires th EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect humai health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, volcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the control of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of these eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lacl< of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decisiois, the 

EPA believes that some drought-related exceedances and violations may be considered for exchsion 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule." Ij'or 

example, the EPA believes that an air agency can submit evidence showing that a severe droughf 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation, eltc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be considred 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which woild need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate spcific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http://wwwepa.gov


Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 00% Postconsumer, Process Chlorine Free Recycled Paper,
Again, thank you for your letter. If you have further questions, please contact me or your staff my 

contact Josh Lewis in the EPA' s Office of Congressional and Intergovernmental Relations at 

1ewis.joshepa.gov or (202) 564-2095.

Janet G. McCabe 

Acting Assistant Administrator
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, D.C. 20460

OFFIC OF


AIR AND RADIATION 

The Honorable Jerry McNerney 

U.S. House of Representatives 

Washington, D.C. 20515 

Dear Congressman McNerney: 

Thank you for your letter dated June 10, 2014, to U.S. Environmental Protection Agency Administrator 

Gina McCarthy, regarding the California drought and whether it qualifies as an "exceptional event" 

under the Clean Air Act (CAA). The Administrator has asked that I respond on her behalf. 

We recognize the importance of this issue for California and its local air districts and the progrss you 

have made in protecting your citizens from the harmful effects of air pollution. We have been vorking 

and will continue to work closely with the San Joaquin Valley Air Pollution Control District (iPCD) 

and other APCDs to resolve exceptional event requests and implementation issues. 

As you know, air pollution can have damaging effects on human health, including respiratory problems, 

hospitalization for heart or lung disease, and even premature death. In addition, air pollution can have 

effects on aquatic life, vegetation, and animals. For these reasons, the Clean Air Act requires tlje EPA to 

set National Ambient Air Quality Standards (NAAQS) for certain air pollutants to protect human health 

and the environment. That said, sometimes "exceptional events" - e.g., high wind dust events, Volcanic 

eruptions, and wildfires - may cause high pollutant concentrations for reasons outside of the control of 

states and regulated sources. In those circumstances, the Clean Air Act allows exclusion of thee eventinfluenced concentrations for regulatory purposes. 

While the CAA specifically defines a "meteorological event involving high temperatures or lak of 

precipitation" as not an exceptional event allowing the exclusion of data from regulatory decis4ons, the 

EPA believes that some drought-related exceedances and violations may be considered for exclusion 

under the provisions of the "Treatment of Data Influenced by Exceptional Events; Final Rule.'l For 

example, the EPA believes that an air agency can submit evidence showing that a severe drouht 

resulted in arid conditions (e.g., lower than typical soil moisture content, decreased vegetation etc.), 

which, when combined with another event (e.g., a high wind event or wildfire), could be consiJered 

eligible for exclusion. In this scenario, the EPA would consider the subsequent event, which ould need 

to meet the provisions of the rule, as the exceptional event. It is in this spirit that we evaluate specific 

state requests for an Exceptional Events finding. 

Internet Address (URL) • http://www.epagov


Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper
Again, thank you for your letter. If you have further questions, please contact me or your staff nay 

contact Josh Lewis in the EPA' s Office of Congressional and Intergovernmental Relations at 

lewis.joshepa.gov or (202) 564-2095.

Janet G. McCabe 

Acting Assistant Administrator