Chapter 173-476 WAC

AMBIENT AIR QUALITY STANDARDS

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WAC 173-476-010 Purpose. This chapter establishes maximum acceptable levels in the ambient air for particulate matter, lead, sulfur dioxide, nitrogen oxides, ozone, and carbon monoxide.

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WAC 173-476-020 Applicability. (1) The provisions of this chapter apply to all areas of the state of Washington.

(2) All federal regulations referenced in this regulation are

adopted as they exist on August 3, 2013.

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WAC 173-476-030 Definitions. Definitions in chapter 173-400 WAC

apply to this chapter. Definitions specific to this chapter include:

"FEM" or "Federal Equivalent Method" means an EPA designated ambient air quality sampling and analysis method that has been designated as an equivalent method according to 40 C.F.R. Part 53. It does

not include a method for which an equivalent method designation has

been canceled according to 40 C.F.R. 53.11 or 53.16.

"FRM" or "Federal Reference Method" means an EPA designated ambient air quality sampling and analysis method specified in an appendix

to 40 C.F.R. Part 50, or a method that has been designated as a reference method according to 40 C.F.R. Part 53. It does not include a

method for which a reference method designation has been canceled according to 40 C.F.R. 53.11 or 53.16.

"mg/m3" means milligrams per cubic meter.

"Period" means any interval of the specified time.

"PM" means particulate matter.

"ppbv" means parts per billion by volume.

"ppmv" means parts per million by volume.

"μg/m3" means micrograms per cubic meter.

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WAC 173-476-100 Ambient air quality standard for PM-10. (1)

Standard for PM-10. The twenty-four-hour average concentration of

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PM-10 in the ambient air must not exceed 150 μg/m3 more than one time

per year, on a three-year average.

(2) Measurement method. The levels of PM-10 in the ambient air

must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix J and designated

according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40

C.F.R. Part 50, Appendix K must be used.

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WAC 173-476-110 Ambient air quality standards for PM-2.5. (1)

Standards for PM-2.5.

(a) The three-year average of the annual arithmetic mean concentration of PM-2.5 must not exceed 12.0 μg/m3.

(b) The three-year average of the ninety-eighth percentile twenty-four-hour average concentration of PM-2.5 must not exceed 35 μg/m3.

(2) Measurement method. The levels of PM-2.5 in the ambient air

must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix L and designated

according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40

C.F.R. Part 50, Appendix N must be used.

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WAC 173-476-120 Ambient air quality standard for lead (Pb). (1)

Standard for lead. The three-month rolling average concentration of

lead and its compounds in the ambient air must not exceed 0.15 μg/m3.

(2) Measurement method. The levels of lead in the ambient air

must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix G and designated

according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40

C.F.R. Part 50, Appendix R must be used.

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WAC 173-476-130 Ambient air quality standards for sulfur oxides

(sulfur dioxide). (1) Standard for sulfur oxides (measured as sulfur

dioxide).

(a) Annual. The annual average concentration for sulfur oxides in

the ambient air must not exceed 0.02 ppmv in a calendar year.

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(b) Twenty-four-hour. The twenty-four-hour average concentration

for sulfur oxides in the ambient air must not exceed 0.14 ppmv more

than once per calendar year. The twenty-four-hour averages must be determined from successive nonoverlapping twenty-four-hour blocks starting at midnight each calendar day.

(c) Three-hour. The three-hour average concentration for sulfur

oxides in the ambient air must not exceed 0.5 ppmv more than once per

calendar year. The three-hour averages must be determined from successive nonoverlapping three-hour blocks starting at midnight each calendar day.

(d) One-hour. The three-year average of the annual ninety-ninth

percentile of the daily maximum one-hour average concentrations for

sulfur oxides in the ambient air must not exceed 75 ppbv.

(2) Measurement method. The levels of sulfur oxides must be measured as sulfur dioxide by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix A-1 or A-2; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation methods.

(a) The annual arithmetic mean is based on the average of hourly

data. To be used in calculating the annual average, the hourly data

must be at least seventy-five percent complete in each calendar quarter of the year.

(b) The interpretation method for the twenty-four-hour average

found in 40 C.F.R. Part 50.4(d) must be followed.

(c) The interpretation method for the three-hour average found in

40 C.F.R. Part 50.5(c) must be followed.

(d) The interpretation method for the one-hour average found in

40 C.F.R. Part 50, Appendix T must be followed.

(4) Rounding of values.

(a) The annual arithmetic mean and twenty-four-hour averages must

be rounded to two decimal places. Fractional parts equal to or greater

than 0.005 ppmv must be rounded up.

(b) The three-hour standard averages must be rounded to one decimal place. Fractional parts equal to or greater than 0.05 ppmv must be

rounded up.

(5) Sunset provision. The ambient standards in WAC 173-476-130

(1)(a) and (b) are no longer applicable in a specific area one year

after the effective date of the EPA's designation of attainment status

of that area for the standard in WAC 173-476-130 (1)(d) and 40 C.F.R.

50.17.

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WAC 173-476-140 Ambient air quality standards for nitrogen oxides (nitrogen dioxide). (1) Standards for nitrogen oxides (measured

as nitrogen dioxide).

(a) The annual average concentration for nitrogen oxides in ambient air must not exceed 53 ppbv (100 μg/m3) measured in the ambient

air as nitrogen dioxide.

(b) The three-year average of the ninety-eighth percentile of the

daily maximum one-hour average concentration of nitrogen oxides must

not exceed 100 ppbv, as measured in the ambient air as nitrogen dioxide.

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(2) Measurement method. The levels of nitrogen oxides must be

measured as nitrogen dioxide by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix F; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40

C.F.R. Part 50, Appendix S must be followed.

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WAC 173-476-150 Ambient air quality standard for ozone. (1)

Standard for ozone. The three-year average of the annual fourth highest daily maximum eight-hour average concentration of ozone in the ambient air must not exceed 0.075 ppmv. 

(2) Measurement method. The levels of ozone in the ambient air

must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix D and designated

according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40

C.F.R. Part 50, Appendix P must be followed.

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WAC 173-476-160 Ambient air quality standards for carbon monoxide. (1) Standards for carbon monoxide.

(a) The eight-hour average concentration of carbon monoxide in

the ambient air must not exceed 9 ppmv (10 milligrams per cubic meter)

more than once per year.

(b) The one-hour average concentration of carbon monoxide in the

ambient air must not exceed 35 ppmv (40 milligrams per cubic meter)

more than once per year.

(2) Measurement method. The levels of carbon monoxide in the ambient air must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix C and designated

according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. An eight-hour average must be considered valid if at least seventy-five percent of the hourly averages for

the eight-hour period are available. In the event that only six (or

seven) hourly averages are available, the eight-hour average must be

computed on the basis of the hours available using six (or seven) as

the divisor.

(4) Rounding of values. When summarizing data for comparison with

the standards, averages must be stated to one decimal place. Comparison of the data with the levels of the standards in ppmv must be made

in terms of integers with fractional parts of 0.5 or greater rounding

up.

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WAC 173-476-170 Monitor siting criteria. Ambient monitors must

be sited as required in 40 C.F.R. Part 58.

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WAC 173-476-180 Reference conditions. (1) All measurements of

air quality that are expressed as mass per unit volume μg/m3 must be

corrected to:

(a) A reference temperature of 25°C; and

(b) A reference pressure of 760 millimeters of mercury (1,013.2

millibars (hectopascals)).

(2) Exception for measurements of PM-2.5 and lead. Measurements

of PM-2.5 and lead must be reported based on the actual ambient air

volume measured at the actual ambient temperature and pressure at the

monitoring site during the measurement period.

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WAC 173-476-900 Table of standards.

Disclaimer: This table is provided as an overview. See complete rule

for more detail.

Pollutant Averaging Time Level Remarks

Measurement

Method

Interpretation

Method

Particle Pollution PM-10 24-hour 150 μg/m3 Not to be exceeded

more than once per

year averaged over

3 years

40 C.F.R. Part 50,

Appendix J

40 C.F.R. Part 50,

Appendix K

PM-2.5 Annual 12.0 μg/m3 Annual mean,

averaged over 3

years

40 C.F.R. Part 50,

Appendix L

40 C.F.R. Part 50,

Appendix N

24-hour 35 μg/m3 98th percentile,

averaged over 3

years

Lead Rolling 3-month

average

0.15 μg/m3 Not to be exceeded 40 C.F.R. Part 50,

Appendix G

40 C.F.R. Part 50,

Appendix R

Sulfur Dioxide Annual 0.02 ppmv Not to be exceeded

in a calendar year

40 C.F.R. Part 50,

Appendix A-1 or

A-2

WAC

173-476-130(3)

24-hour 0.14 ppmv Not to be exceeded

more than once per

year

3-hour 0.5 ppmv Not to be exceeded

more than once per

year

1-hour 75 ppbv 99th percentile of

1-hour daily

maximum

concentrations,

averaged over 3

years

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Pollutant Averaging Time Level Remarks

Measurement

Method

Interpretation

Method

Nitrogen Dioxide Annual 53 ppbv Annual Mean 40 C.F.R. Part 50,

Appendix F

40 C.F.R. Part 50,

Appendix S 1-hour 100 ppbv 98th percentile of

1-hour daily

maximum

concentrations,

averaged over 3

years

Ozone 8-hour 0.075 ppmv Annual fourthhighest daily

maximum 8-hr

concentration,

averaged over 3

years

40 C.F.R. Part 50,

Appendix D

40 C.F.R. Part 50,

Appendix P

Carbon Monoxide 8-hour 9 ppmv Not to be exceeded

more than once per

year

40 C.F.R. Part 50,

Appendix C

WAC

173-476-160(3) 1-hour 35 ppmv

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