List of Figures

Figure 1 Satellite image from Google Earth of the Soldotna site

Figure 2 Soldotna monitoring site

Figure 3 Population estimates for Soldotna

Figure 4 Daily PM₁₀ (µg/m³ ) from 2012-2014

Figure 5 Daily PM_2.5 (µg/m³ ) from 2011-2014

Figure 6 Satellite image of 2014 Funny River Fire from May 20, 2014

List of Tables

Table 1 PM monitoring method codes, type, and instruments

Table 2 First and second maximum PM₁₀ (µg/m³ ) values

Table 3 List of all days that exceeded the 24-hour PM_2.5 NAAQS in Soldotna

Table 4 PM_2.5 (µg/m³ ) design values

Table 5 First and second maximum PM_2.5 (µg/m³ ) values

Acronyms

AQS Air Quality System

BAM Beta Attenuation Monitor

CIRIAMS Cook Inlet Regional Integrated Air Monitoring System

DEC Alaska Department of Environmental Conservation

EPA U.S. Environmental Protection Agency

FEM Federal Equivalent Method

µg/m³ micrograms per cubic meter

Mat-Su Valley Matanuska-Susitna Valley

NAAQS National Ambient Air Quality Standard

PM_2.5 Particulate matter less than 2.5 microns

PM₁₀ Particulate matter less than 10 microns

POC parameter occurrence code

QA quality assurance

SPM Special purpose monitoring

VSCC very sharp cut cyclone

Executive Summary

The State of Alaska Department of Environmental Conservation (DEC), in an effort to protect the public health and the environment, has been mandated by the legislature to evaluate, assess, and mediate environmental issues that may affect the health and welfare of residents within the state. To further these objectives, DEC has established a statewide air monitoring network. The network currently consists of sites in Juneau, Anchorage, Fairbanks, and the Matanuska-Susitna Valley (Mat-Su Valley). This report provides information about air monitoring in Soldotna, Alaska from 2011 to 2014.

Between 2011 and 2014, DEC monitored particulate matter at the Soldotna monitoring site. Two sizes of particulate matter, particulate matter with an aerodynamic diameter of 10 micrometers or smaller (PM₁₀), and particulate matter with an aerodynamic diameter of 2.5 micrometers or smaller (PM_2.5) were monitored at the site. The U.S. Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for each of these pollutants.

The Soldotna monitoring site was established as part of the Cook Inlet Regional Integrated Air Monitoring System (CIRIAMS) monitoring network to provide real-time data to the public and help DEC issue more timely air quality advisories. Due to budget issues the site was discontinued in July 2014. No regulatory grade monitoring currently occurs on the Kenai Peninsula, but DEC currently maintains a low-cost community sensor in Soldotna and several other nearby communities on the Kenai Peninsula. Continuous hourly data for these sensors can be found on the DEC real-time air monitoring website¹.

Only two exceedances of the NAAQS occurred between 2011-2014 at the Soldotna site. In total, zero days exceeded the 24-hour PM₁₀ NAAQS of 150 µg/m³ . A total of two days exceeded the 24-hour PM_2.5 NAAQS of 35 µg/m³ during the Funny River Fire on the Kenai Peninsula in May 2014. Due to incomplete data capture design values could not be calculated for the site except in 2014 when the exceptional events were included the 24-hour design value was 46 µg/m³ . However, the 24-hour design value for that year, excluding exceptional events, was 15 µg/m³ but was not considered valid due to data not meeting completeness criteria with the exclusion of wildfire impacted days.

Introduction

The State of Alaska Department of Environmental Conservation (DEC) is mandated by the Alaska State Legislature to “conserve, improve, and protect its natural resources and environment and control water, land, and air pollution, in order to enhance the health, safety, and welfare of the people of the state and their overall economic and social well-being” under Alaska Statue 46.03.010. The DEC Division of Air Quality operates a statewide air monitoring network with permanent regulatory monitoring sites in Juneau, Anchorage/Matanuska-Susitna Valley (Mat-Su Valley), and Fairbanks, as well as additional special purpose or temporary sites. This report provides information about air monitoring conducted in Soldotna between 2011 and 2014 on the Kenai Peninsula.

Site Description

The Soldotna monitoring site was established in 2011 at 144 N Binkley Street, Soldotna, Alaska 99669 (Figure 1). The Soldotna site was in an urban and residential area of the Kenai Peninsula Borough located between Park Avenue to the north, Shady Lane to the south, North Binkley Street to the west, and Barbara Erickson Street to the east. The site is less than 1 mile away from the Kenai Spur Highway to the east and the Sterling Highway to the south. The monitoring site was a fenced in trailer that sat to the east of the back parking lot of the Kenai Peninsula Borough office building (Figure 2).

Over the time that the site was operating (2011-2014) the population of Soldotna was around 4,300 residents, with 4,284 residents in 2011, 4,299 in 2012, 4,284 again in 2013, and 4,311 residents in 2014 (Figure 3)^2,3,4,5. Over that time, the average population size was 4,295 residents and the median number of residents was 4,292 residents.

Soldotna climate typically has average winter lows of 10˚F in January and summer highs of 64˚F in July. Wind tends to flow in a weak east-west direction. Wildfires are common on the Kenai Peninsula between May and September.

Results

Particulate matter monitoring at the Soldotna monitoring site was intended as an SPM site under the CIRIAMS monitoring network to provide real-time air quality data to the public and decision-makers. The site utilized regulatory grade federal equivalent method (FEM) instruments to continuously measure PM_2.5 and PM₁₀ (Table 1). DEC utilized beta attenuation monitors (BAMs) for measuring particulate matter. BAM particulate matter monitoring uses a glass-fiber filter tape that lasts several weeks. This sampling method involves drawing ambient air through a size-selective inlet over an hour period, depositing particulate on the filter tape. The sampler measures the amount of beta radiation that passes through the tape before and after the sample is collected and uses that data to calculate the particulate matter concentration in micrograms per cubic meter (µg/m³ ). Flow rate, flow duration, ambient temperature, and ambient barometric pressure are then used to calculate concentration.

FEM data undergo quality assurance (QA) checks by DEC before it is uploaded to the EPA’s national database of ambient air quality data, the Air Quality System (AQS). This data is available for the public at https://www.epa.gov/outdoor-air-quality-data. DEC and EPA use this data to determine whether the air quality of a locality meets the NAAQS set by the EPA. A standard is a maximum allowable concentration that must not be exceeded over a set averaging time, against which a pollutant is compared or measured. Most standards set an upper bound to a pollutant. EPA has two methods for determining compliance, or attainment, with ambient air quality standards: deterministic and probabilistic.

A deterministic method allows a certain (low) number of exceedances over a set time and a specific number of valid samples. EPA uses this method to determine compliance with the 24-hour PM₁₀ NAAQS of 150 µg/m³ under standard conditions of temperature and pressure. An area complies with this NAAQS if the sum of its valid samples does not exceed the standard more than once per year on average over a 3-year period with a data capture rate of at least 75%.

A probabilistic method allows for multiple exceedances if the distribution of sampled values is such that a set statistic is less than the NAAQS. This method makes compliance with the NAAQS less sensitive to extreme conditions that may not be typical of the local area. EPA uses this method to determine compliance with the PM_2.5 24-hour NAAQS of 65 µg/m³ (1997-2006) or 35 µg/m³ (2006-present) and with the annual NAAQS if the 3-year weighted annual mean is less than 15 µg/m³ (1997-2006), 12 µg/m³ (2006-2024), or 9 µg/m³ (2024-present)⁶. The NAAQS for PM_2.5 became stricter over the years due to research on the negative health impacts of fine particulate and the desire to be more protective of human health.

EPA’s probabilistic methods employ a statistic called the “design value”. Design values can be calculated from the sample data, using modeling results, or be a count of the number of exceedances of a NAAQS. Design values change from year to year depending on meteorological conditions, pollutant levels, and unusual events.

The EPA does have a process by which data arising from unusual or “exceptional” events can be excluded from the data set used to determine compliance with a standard. EPA introduced an exceptional events policy in 2007 where ambient air monitoring agencies can request exceptional event waivers to exclude these events from calculations of design values. DEC commonly requests exceptional event waiver requests for Fairbanks North Star Borough monitoring site data due to the frequency of wildfires in the summer months in the area.

If an area cannot meet an air quality standard, the EPA through the powers outlined in the Clean Air Act, may designate it as a “non-attainment” area. This designation triggers a five-year window during which the state must gather additional data, must submit a State Implementation Plan to the EPA, must institute control measures, and must meet the standard at the end of that time. EPA can levy sanctions against a designated non-attainment area that may result in legal obligations or sanctions including the loss of federal highway funding and of economic development opportunities.

PM₁₀ Monitoring

PM₁₀ monitoring in Soldotna started in January 2012 and stopped in May 2014. There was a brief gap in monitoring from August 2013 to December 2013. During the three years of PM₁₀ monitoring in Soldotna, zero exceedances of the 150 µg/m³ PM₁₀ NAAQS were recorded (Table 2 and Figure 4).

1st Max	Date of 1st Max	2nd Max	Date of 2nd Max	POC
131	2012-12-07	108	2012-04-10	3
84	2013-06-26	68	2013-04-15	3
96	2014-05-22	90	2014-03-31	3

PM_2.5 Monitoring

PM_2.5 monitoring in Soldotna began in October 2011 and ended in June 2014. Monitoring was continuous from October 2011 until July 2013 when there was a brief pause in monitoring efforts until February 2014. Monitoring was then discontinued altogether in June 2014. Generally, PM_2.5 was well below the PM_2.5 NAAQS during this period (Figure 5).

Only two exceedances of the 24-hour PM_2.5 NAAQS of 35 µg/m³ were recorded at the site between 2011-2014 (Table 3). These exceedances on May 24 and May 26, 2014, were during the Funny River Fire and were flagged as wildfire affected days. The fire started on May 19, 2024, at approximately 7 p.m., burning more than 43,000 acres by May 21, 2014. The Funny River Fire lasted until June 7, 2014, and burned nearly 200,000 acres⁷. The only data from the Soldotna monitoring site between 2011-2014 annotated with wildfire flags was collected on May 24 and May 26, 2014. DEC can request that wildfire days be excluded from calculations of design values with exceptional event waiver requests but typically it has only done so for the Fairbanks North Star Borough which is in non-attainment of the 24-hour and Annual PM_2.5 NAAQS. Exceptional event waivers are intended to exclude wildfire smoke impacted data from design value calculations, as wildfires are a naturally occurring event that cannot be regulated. Excluding wildfire smoke impacted days from design value calculations results in a value that is more in line with human contributions made to PM_2.5 pollution.

Date	PM2.5 (µg/m3)	Qualifier
2014-05-24	121.4	RT – Wildfire U.S.
2014-05-26	114.5	RT – Wildfire U.S.

As monitoring only occurred between October 2011 and June 2014, with disruptions in monitoring efforts from July 2013 to February 2014 a valid annual design value could not be calculated for the site and the 2014 24-hour design value was only valid when exceptional events (the Funny River Fire impacted days) were included in the calculation (Table 4).

Year	98th percentile	98th percentile (exceptional events excluded)	Weighted mean	Weighted mean (exceptional events excluded)	24-hour design value	24-hour design value (exceptional events excluded	Annual design value	Annual design value (exceptional events excluded
2011	8.2*	8.2*	2.9*	2.9*	8*	8*	2.9*	2.9*
2012	7.4	7.4	1.0	1.0	8*	8*	1.9*	1.9*
2013	8.3*	8.3*	0.9*	0.9*	8*	8*	1.6*	1.6*
2014	121.4	29.7*	10.8*	8.3*	46	15*	4.2*	3.4*

*value does not meet completeness criteria

Conclusions

Between 2011 and 2014, DEC monitored ambient concentrations of particulate matter (PM₁₀ and PM_2.5) in Soldotna. The site was closed in 2014 due to budget issues. While the site was open only two exceedances of the PM_2.5 24-hour NAAQS of 35 µg/m³ were recorded. These exceedances occurred on May 24 and 26, 2014 during the Funny River Fire and both days were qualified as wildfire affected days. Due to incomplete data capture between 2011-2014 valid design values could not be calculated for the site except in 2014 the 24-hour design value with exceptional events included (Funny River Fire impacted days) was 46 µg/m³ , however, the 24-hour design value for that year excluding exceptional events was 15 µg/m³ , but was not considered valid due to data not meeting completeness criteria with the exclusion of wildfire impacted days.

Appendix

Note: Some years have multiple values listed as the first maximum when exceptional events with and without EPA concurrence were excluded or included in the calculation. Notes on the how the values were calculated are made in the “Notes” column. Years with only one value either had no exceptional events or the first maximum was the same regardless of the inclusion or exclusion of exceptional events and no note is included in the “Notes” column in those cases.