eagle river pm10 limited maintenance plan · 2019-03-03 · iii.b.1-1 final draft 11/05/09 section...

Eagle River

PM10 Limited Maintenance Plan

Proposed Revision to the State of Alaska Air Quality Control Plan

Prepared by the Municipality of Anchorage

Department of Health and Human Services

for submission to the Alaska Department of Environmental Conservation

for inclusion in the State Implementation Plan for Air Quality

November 5, 2009

This page left intentionally blank for two-sided copying.

A note on the format and organization of this document.

This document is organized and formatted to be consistent with the State of Alaska Air Quality Control Plan. This document is intended to replace Section III.D Volume II of the plan and is organized accordingly.

III.B.1-1 Final Draft 11/05/09

SECTION III.D.2

EAGLE RIVER PM10 LIMITED MAINTENANCE PLAN

III.D.2.1. Introduction Between 1985 and 1987 Eagle River frequently violated the national ambient air quality standard (NAAQS) for particulate matter air pollution with an aerodynamic diameter less than or equal to 10 µm in size. This particulate air pollution is known as PM10. As a consequence, in 1991 the Environmental Protection Agency (EPA) designated a nine square kilometer area in Eagle River as a moderate nonattainment area for PM10 and required the submission of an air quality attainment plan to bring the area into compliance with the NAAQS.*

In 1991, the Municipality of Anchorage (MOA) and the Alaska Department of Environmental Conservation (ADEC) prepared a State Implementation Plan (SIP) to address the PM10 problem in Eagle River. This plan was entitled the Eagle River PM10 Control Plan. The plan identified the main source of PM10 as unpaved roads and outlined an ambitious road paving program to reduce emissions from this source. The EPA approved the plan as an amendment to the SIP on August 13, 1993 (58 FR 43084).

Air quality monitoring data now show that Eagle River has attained the standard. However, in order for EPA to formally re-designate Eagle River to an attainment area, the Clean Air Act (CAA) requires the State to submit a maintenance plan to EPA that demonstrates that the air quality control measures in place in Eagle River are sufficient to ensure continued maintenance of the PM10 NAAQS. Once approved by EPA, this section of the state’s Air Quality Control Plan, the Eagle River PM10 Limited Maintenance Plan, will replace the earlier Eagle River PM10 Control Plan in the Alaska SIP.

The State has delegated the responsibility for air quality planning in Anchorage and Eagle River to the MOA. The MOA has worked with ADEC to prepare this new plan using the Limited Maintenance Plan (LMP) option provided under EPA guidance. It demonstrates that Eagle River is now in attainment with the federal air quality standard for PM10 as a result of the road paving program and that continued maintenance of the standard is expected for a minimum of ten years. The plan also demonstrates that Eagle River qualifies for the LMP option and meets the SIP planning requirements stipulated in the Clean Air Act.

The plan includes a request to the EPA Administrator to redesignate the Eagle River PM10 nonattainment area to attainment.

It should be noted that this plan is predicated on the presumption that EPA will approve an exceptional event waiver for a PM-10 exceedance that occurred due to high winds on December 2, 2007.

III.D.2.2. Local Planning Process This plan was prepared in accordance with the provisions of sections 110 and 174 of the CAA which require the consultation and participation of local political subdivisions and

* Under the Clean Air Act, states are ultimately responsible for the submission of air quality plans. These plans are known as SIPs or State Implementation Plans.


local elected officials. Under Section 174 (42 U.S.C. 7504), the revised plan submitted to EPA as a formal SIP amendment must be prepared by "an organization certified by the State, in consultation with elected officials of local governments." Such an organization is required to include local elected officials and representatives of the state air quality planning agency (i.e., ADEC), the state transportation planning agency (i.e., Alaska Department of Transportation & Public Facilities (ADOT/PF), and the metropolitan planning organization (MPO) responsible for the transportation planning process for the affected area.

In 1976, the governor designated the MOA as the MPO for the Anchorage urbanized area which includes Eagle River. In Anchorage, the MPO is known as Anchorage Metropolitan Area Transportation Solutions or AMATS. Consequently, the MOA conducts the transportation planning process required under federal regulation, in cooperation with ADEC and ADOT/PF, through the AMATS organization. In 1978, the governor designated MOA as the lead air quality planning agency in Anchorage. Based on this designation, MOA has continued its role as the lead planning agency in the Anchorage area and prepared this plan. The air quality planning process is outlined in the AMATS Intergovernmental Operating Agreement for Transportation and Air Quality Planning. This agreement was last revised in August 2002 and became effective January 1, 2003. This operating agreement establishes the roles and relationships between governmental entities involved in the Anchorage air quality planning process.

The AMATS Policy Committee provides guidance and control over studies and recommendations developed by support staff. Voting members of the Policy Committee are listed below.

• MOA Mayor; • ADOT/PF Central Regional Director; • MOA Assembly representative; • MOA Assembly representative; and • ADEC Commissioner or designee.

The AMATS Technical Advisory Committee (TAC) and member support staff analyze transportation and land use issues and develop draft recommendations for the Policy Committee. Voting members include the following:

• MOA Traffic Director; • MOA Project Management and Engineering Director; • MOA Planning Director; • MOA Public Transportation Director; • MOA Department of Health & Human Services representative; • MOA Port of Anchorage Director; • ADOT/PF Chief of Planning & Administration; • ADOT/PF Regional Pre-Construction Engineer; • ADEC representative; • Alaska Railroad representative; and • AMATS Air Quality Advisory Committee representative.

In addition, to help provide public input into the current air quality planning process by interested local groups and individual citizens, a third AMATS committee, the Air Quality Advisory Committee was appointed by the Policy Committee. The Air Quality Advisory


Committee is comprised of nine members. Committee membership has generally included at least one physician or health professional, a representative of the I/M industry, a representative of the environmental community, and a representative from the Municipal Planning and Zoning Commission. Public Participation Process

Section 110(a) of the CAAA (42 U.S.C. 7410(a)) requires that a state provide reasonable notice and public hearings of SIP revisions prior to their adoption and submission to EPA. To ensure that the public had adequate opportunity to comment on revisions to the Anchorage air quality attainment and maintenance plans, a multi-phase public involvement process, utilizing AMATS and the Anchorage Assembly was used.

AMATS Air Quality Advisory Committee – The AMATS Air Quality Advisory Committee held a public meeting on the limited maintenance plan on October 21, 2009. During this meeting they recommended that the AMATS Technical and Policy Committees adopt the plan as submitted.

AMATS Technical and Policy Committees – The AMATS Technical Advisory Committee released the limited maintenance plan for 30-day public review on September 2009; no comments were received. After reviewing the recommendation of the AMATS Citizen Air Quality Advisory Committee, on [date TBD], the AMATS Technical Committee recommended that the AMATS Policy Committee adopt the plan. Subsequent to this recommendation, the AMATS Policy Committee met on [date TBD] to review and adopt the the plan.

Anchorage Assembly – The Anchorage Assembly adopted the plan during its regular public meeting held on[date TBD]. A copy of Assembly Resolution AR 200X-XXX is included in the Appendix to Section III.D.2.2.

ADEC hearings – The final opportunity for public involvement occurs at the state administrative level. Prior to regulatory adoption of SIP revisions, ADEC holds public hearings on the revisions in the affected communities. ADEC held a public hearing on the Anchorage maintenance plan on [date TBD]. This provided another forum for the public to comment on the air quality plan prior to state adoption and submission to EPA.

III.D.2.2-1 Final Draft 11/05/09

III.D.2.3. Boundary of the Eagle River Maintenance Area Eagle River is a community of about 30,000 located roughly 10 miles northeast of downtown Anchorage and is part of the Municipality of Anchorage. It is located at the end of a glacial river valley bounded on the west by Cook Inlet and on the south by the Eagle River and the Chugach Mountains on the northeast. Eagle River is a bedroom community to Anchorage and land use in the area is largely suburban and rural residential with some commercial development. When the Eagle River PM10 Control Plan was prepared in 1991, it identified a nine square kilometer nonattainment area that encompassed all of the central business district and most of the more densely populated suburban sections of the community. This maintenance plan retains this same boundary. It will become the maintenance area boundary effective upon approval of this plan.

A description of the maintenance area boundary follows.

Beginning from the point where the centerline of the southbound section of the Glenn Highway crosses Eagle River, thence

Northward three kilometers to point approximately 200 meters west of the Glenn Highway along the westward extension of Mercy Street, thence,

Eastward along the alignment of Mercy Street two kilometers to an undeveloped point, thence,

Southward two kilometers to a point approximately 150 meters west of Eagle River Loop Road and approximately 70 meters southwest of the intersection of Kantishna and Iditarod Streets (near the point where the Loop road crosses Meadow Creek); thence,

Eastward three kilometers to an undeveloped point; thence,

Southward one kilometer to a point approximately 100 meters southeast of the intersection Eagle River Road and Greenhouse Street, thence,

Westward five kilometers approximately 70 meters south of the alignment of Eagle River ending at the centerline of the southbound section of the Glenn Highway which is the point of the beginning.


Figure III.D.2-1 Eagle River PM10 Limited Maintenance Area Boundary

with Parkgate PM10 Monitoring Site


III.D.2.4. Demonstration that Eagle River has Attained the PM10 NAAQS The EPA designated Eagle River as a “moderate” nonattainment for PM10 on November 6, 1990 pursuant to Clean Air Act Section 107(d)(4)(B). The nonattainment designation was based on data collected at the Parkgate site in Eagle River. The primary and secondary national ambient air quality standard (NAAQS) for PM10 is set at 150 micrograms per cubic meter (µg/m3). The NAAQS used to also include an annual average standard but that standard was recently revoked by the EPA (71FR 61144; October 17, 2006).

Monitoring has been performed in the nonattainment area at the Parkgate monitoring site since 1985. The Parkgate site is located on the east side of a commercial strip that runs along the Old Glenn Highway. The land use to the north, west and east of the site is generally commercial while the land to the east is primarily residential. Prior to 1988, this site was bounded on two sides by gravel roads. The location of the site is identified in Figure III.D.2-1, presented earlier in this section.

Figure III.D.2- 2

Looking North from the Parkgate Site in Eagle River (2006)

In 1987 there were over 22 miles of unpaved gravel roads in the nonattainment area. The Eagle River PM10 Control Plan called for paving or surfacing about one-third of the


unpaved roads in the area. By 2007, all roads in the area had been paved or surfaced with recycled asphalt. As illustrated in Figure III.D.2-3, data suggest that paving has successfully lowered PM10 concentrations. Exclusive of natural events, the highest PM10 concentrations measured since 1988 have been roughly half the 24-hour standard.

Figure III.D.2-3 First and Second Highest 24-Hour Average PM10 Concentrations

Parkgate Site, Eagle River (1985-2007)

0

100

200

300

400

500

600

1985 1990 1995 2000 2005Year

PM10

(ug/

m3 ) 1st Max

2nd Max

Street clean-up, paving program starts (1988)

Mt. Spurr eruption (1992)

exceptional events due to strong wind

24-hr standard (150 ug/m3)

Mt. Redoubt eruption

(1989-90)

PM10 concentrations measured in the Eagle River non-attainment area have been well below the NAAQS for over 15 years. The only incidents that have approached or exceeded the 24-hour NAAQS since 1988 were due to ash from volcanic eruptions or wind/dust storms.

Starting December 1989, Mt. Redoubt, about 100 miles southwest of Eagle River, erupted intermittently for six months. On April 12, 1990, the 24-hour average PM10 concentration reached 143 μg/m3. However polarized light microscopic (PLM) analysis of PM10 filters deployed on April 7, 9, and 11 showed that volcanic ash comprised 40-50% of the total PM10 assemblage (Microlab Northwest Laboratory Report No. 1062-94, October 17, 1994).

The eruption of Mt. Spurr (approximately 80 miles west of Eagle River) on August 18, 1992 also raised PM10 concentrations in both Anchorage and Eagle River for an extended period following the eruption. PLM analysis indicated that the ash content of the PM10 was 87-95% of total assemblage immediately after the eruption (August 19 and 20) and remained as a major component (20-38%) of the PM10 for several years. On September 16, 1992 concentrations reached 165µg/m3 at the Parkgate site in Eagle River, an exceedance of the 24-hour standard. Similarly high concentrations were observed at other PM10 monitors in the Anchorage bowl. This event was attributed to re-entrained volcanic ash.


The Eagle River PM10 Control Plan identified fall “freeze-up” and spring “break-up” as the two periods when the highest PM10 concentrations occur and it focused on controlling emissions during those times. Figure III.D.2-4 compares PM10 concentrations before paving (1985-87) with concentrations over the past ten years (1998-2007) after the completion of the paving program. The largest declines in Eagle River PM10 have been observed in the fall period. The data show that the 95th percentile PM10 concentration during fall freeze-up has dropped by about 75% while the concentration during spring break-up has fallen 5% to 20%. These declines are roughly consistent with those predicted in 1991 when the Control Plan was drafted. In the late-80’s and early-90’s, high fall season PM10 concentrations were a greater concern than spring. The highest PM10 concentrations in Eagle River now typically occur in spring break-up rather than the fall freeze-up period.

Figure III.D.2-4

95th Percentile PM10 Concentrations Before and After Implementation of Road Paving Program in Eagle River

0

50

100

150

200

250

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

PM10

Con

cent

ratio

n (u

g/m

3 )

Before Paving (1985-1987)

After Paving (1998-2007)

The highest, second highest and number of days exceeding the NAAQS are tabulated in Table III.D.2-1 for the period 1998-2007. The table provides clear evidence that Eagle River is in attainment with the NAAQS.


Table III.D. 2-1 Maximum, 2nd Maximum and Number of Exceedances at

Parkgate Site, Eagle River 1998-2007

Year 24-hour Max

(µg/m3)

2nd Highest 24-hour (µg/m3)

Number of Days Exceeding NAAQS

1998 59 55 0 1999 90 66 0 2000 64 53 0 2001 69 66 0 2002 46 40 0 2003# 92 90 0 2004 70 43 0 2005 90 65 0 2006 65 60 0 2007# 48 46 0

# Note: This table does not include wind-related exceptional events that occurred in 2003 and 2007. The 24-hour PM10 concentration was 590 µg/m3 on March 12, 2003 and 223 µg/m3 on December 2, 2007.

III.D.2.5. Demonstration that Eagle River Qualifies for the LMP Option On August 9, 2001 EPA issued guidance on streamlined maintenance plan provisions for certain PM10 nonattainment areas seeking redesignation to attainment (Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas, Wegman 2001). The EPA observed that areas meeting certain statistical criteria have a high degree of probability of continued compliance with the NAAQS. Based on this analysis, they developed specific criteria to qualify for the LMP option. Elements of these criteria follow:

LMP Qualification Criteria

1. The area should be attaining the PM10 NAAQS;

2. The average 24-hour PM10 design value (DV) for the area, based on the most recent five years of air quality data at all monitors in the area, should be at or below 98 ug/m3 with no violations at any monitor in the nonattainment area;* and

3. The area should expect only limited growth in on-road motor vehicle PM10 emissions (including fugitive dust) and should have passed a motor vehicle regional emissions analysis test.

* EPA also established a procedure for determining an alternate, site-specific criteria (called the Critical Design Value) that allows area with design values with little inter-annual variability to qualify for the LMP option if their DV is above 98 µg/m3.


The next three sub-sections will demonstrate that Eagle River meets these three criteria.

1. Eagle River is attaining the PM10 NAAQS

Section II.D.2-4 provided a demonstration that Eagle River has been in attainment with the NAAQS for over 15 years. Except for uncontrollable natural events such as volcanic eruptions and wind/dust storms, Eagle River last exceeded the NAAQS in 1987. 2. The average DV for the Eagle River area is below 98 ug/m3

Computational methods for determining the 24-hour DV are outlined in the PM10 SIP Development Guideline (EPA-450/2-86-001, June 1987). The empirical frequency distribution approach (see Section 6.3.3. of the guideline) was used to determine the DV which is defined as the site-specific PM10 concentration that would be expected to be exceeded at a frequency of once every 365 days. Table III.D.2-2 shows that Eagle River has a computed DV for the last 5 years that is below the LMP criteria of 98 µg/m3 (details of this computation can be found in the Appendix to III.D.2.5.). The table also demonstrates that there is no increasing trend over the last decade. Exceedances of the NAAQS were recorded on March 12, 2003 and December 2, 2007. Both incidents, however, have been flagged as exceptional events due to blowing dust from high winds. These incidents were therefore not considered when determining attainment or included in the DV computation.

Table III.D. 2-2

DV Computed from Empirical Data Distribution Parkgate Site, Eagle River 1998-2007

Three-year Period Used to Compute DV

DV (computed from empirical

data distribution of 3 years data)

(µg/m3) 1998-2000 84.5 1999-2001 95.5 2000-2002 89.7 2001-2003 108.0 2002-2004 94.1 2003-2005 102.7 2004-2006 88.2 2005-2007 86.0

Average DV for the last 5 years (2003-2007) 92.3

LMP criteria 98.0


3. Eagle River Passes Motor Vehicle Regional Emissions Analysis Test

Increases in emissions from on-road mobile sources must be taken into account over the next 10 years to help ensure that PM10 concentrations will remain below the NAAQS.* The EPA LMP guidance recommends the use of the following equation to assess the impact of future emission increases from motor vehicle travel:

Projected DV in 2020 = DV2007 + (VMTpi x DVmv) ≤ MOS

Where:

DV = the area’s average DV in µg/m3 for the period used to demonstrate attainment (base year 2007).

VMTpi = the projected % increase in vehicle miles traveled (VMT) between 2007 and 2020.

DVmv = Portion of DV for the attainment year (2007) inventory in µg/m3 that is derived from on-road emissions

MOS = margin of safety for the relevant PM10 standard in μg/m3 for a given area. This can be = 98 µg/m3 or a site-specific value computed from data collected at the site of interest using methods outlined in Attachment A of the LMP guidelines. For the Parkgate site in Eagle River this value was computed to be 116.6 μg/m3

. (See Appendix to III.D.2.5 for details of this computation.)

In the preceding sub-section, the average DV was computed to be 92.3 µg/m3.

VMTpi was estimated using VMT estimates made for the air quality conformity analysis for the Chugiak/Eagle River Long Range Transportation Plan (CE/LRTP). The analysis included VMT estimates for analysis years 2007, 2017, and 2027. for the Eagle River PM10 non-attainment area. Total VMT in 2007 was 165,934. VMT for year 2020 was estimated by interpolating between 2017 and 2027 VMT. By 2020, VMT is projected to grow by 36.3% to 226,221. Thus the projected increase in VMT (VMTpi) is 0.363.

As will be shown in the PM10 emission inventory presented later in Section III.D.2.6, the proportion of total PM10 from on-road mobile emissions varies with season in the Eagle River maintenance area. In the base year 2007 emission inventory, on-road mobile emissions, including fugitive dust emissions, were responsible for 50.6% of total daily emissions in spring and 44.4% in the fall (see Table III.D.2-3 for details). For the purposes of the Motor Vehicle Regional Emissions Analysis Test, the higher spring season proportion was assumed. The portion of 2007 DV that is attributed to on-road mobile sources (DVmv) can be readily calculated as follows:

DVmv = DV x 0.506 = 92.3 µg/m3 x 0.506 = 46.7 µg/m3

Knowing the values of the four variables, the projected DV in 2020 can be readily computed:

* This emissions analysis demonstration assumes that EPA will re-designate Eagle River a maintenance area in 2010. The year 2020 was selected because it is ten years hence.


Projected DV in 2020 = DV2007 + (VMTpi x DVmv) = 93.6 µg/m3 + (0.363 x 47.4 µg/m3)

Projected DV in 2020 = 109 µg/m3 < MOS The projected DV in 2020 is less than the 116.6 µg/m3 margin of safety value or MOS, demonstrating that the Eagle River Maintenance Area meets the Motor Vehicle Regional Emissions Analysis Test.

III.D.2.6. Attainment Year Emission Inventory for Eagle River The base year attainment inventory for this LMP was selected to be 2007. An emission inventory was also prepared for 2020, the final year of a ten-year maintenance period.* As noted in Section III.D.2.4, over the past ten years the highest PM10 concentrations have typically occurred during spring break-up and fall freeze-up. For this reason, the emission inventories reflect conditions and activity levels (e.g., amount of silt loading on roads, residential wood heating rates) that commonly occur during these two times of year. The assumptions, methods and computations used to generate the 2007 and 2020 emission inventories are described in detail in the Appendix to III.D.2.6.

Five sources of PM10 emissions were identified and inventoried. These include (1) dust from paved roads; (2) wind-generated dust from roads, parking lots and un-vegetated areas; (3) fireplaces and woodstoves, (4) natural gas combustion; and (5) exhaust, tire and brake wear emissions from motor vehicles.

The emission inventory prepared for the Eagle River PM10 Control Plan (base year 1987) also included emission estimates for unpaved roads. However, as noted earlier in this document, all roads in the maintenance area have been paved since that plan was prepared. Thus, unpaved road emissions are not included in the 2007 or 2020 inventories.

The EPA publication, AP-42, Compilation of Air Pollutant Emission Factors, outlines recommended assumptions and methods for estimating emission factors for various sources.† AP-42 methods were used to estimate emission factors for four of the five sources inventoried. Instead of AP-42, the EPA mobile source emission factor model, MOBILE6.2 was used to estimate the emission factor for motor vehicle exhaust, tire and brake wear emissions. Methods, assumptions and computations are described in detail in the Appendix to III.D.2.6.

The results of the inventory are presented in Table III.D.2-3. Paved road dust, wind blown dust and fireplace and wood stove emissions are the main sources of PM10 in the Eagle River maintenance area.

* Again, this assumes that EPA will approve this maintenance plan in 2010. † An emission factor is a representative value that attempts to relate the quantity of a pollutant release to the atmosphere with an activity associated with the release of that pollutant.


Table III.D. 2-3

Eagle River Limited Maintenance Area PM10 Emissions Inventory (All Emissions in tons/day with % of Total)

Spring Break-up (March, April)

Fall Freeze-up (October, November)

Source Category 2007 2020 2007 2020

Paved Roads 2.88

(50.6%) 3.97

(57.8%) 0.83

(44.4%) 1.13

(50.8%) Wind blown Dust from Paved Roads, Parking Lots and Un-Vegetated Areas

2.47 43.5%

2.53 (36.8%)

0.70 (37.6%)

0.72 (32.5%)

Fireplaces and Wood Stoves 0.32

(5.7%) 0.36

(5.2%) 0.32

(17.3%) 0.36

(16.1%)

Natural Gas Combustion 0.008

(0.1%) 0.009

(0.1%) 0.008

(0.4%) 0.009

(0.4%) Exhaust, Tire and Brake Wear Emissions from Motor Vehicles

0.005 (0.1%)

0.006 (0.1%)

0.005 (0.3%)

0.006 (0.3%)

TOTAL 5.69

(100%) 6.87

(100%) 1.87

(100%) 2.22

(100%)

III.D.2.7. Section 110 and Part D Requirements Before the EPA administrator can re-designate an area to attainment the CAA requires that a state containing a nonattainment area meet all applicable requirements including those in Section 110 and Part D of the Act. Section 110 of the Act outlines requirement for SIPs and Part D contains general requirements applicable to all designated nonattainment areas. Subpart 4 of Part D includes specific provisions for particulate matter nonattainment areas. Section 110

EPA designated Eagle River as a “moderate” nonattainment for PM10 on November 6, 1990 pursuant to Clean Air Act Section 107(d)(4)(B). EPA required nonattainment areas like Eagle River to prepare plans to attain the standard. The approval of the Eagle River nonattainment plan by EPA in 1993 is evidence that applicable requirements of Section 110 have been satisfied. EPA approved the Eagle River PM10 attainment plan (58 FR 43084) as an amendment to the Alaska SIP for air quality on August 13, 1993.

Part D Requirements

There are a number of requirements in Part D that are pertinent to the approval of the Eagle River LMP. These include requirements for air quality monitoring, contingency measures, and transportation conformity. These are addressed later in this document.

The Part D NSR rules for PM10 nonattainment areas in Alaska were approved by EPA. In Eagle River, NSR requirements will be replaced by the Prevention of Significant Deterioration (PSD) program in the maintenance area NSR program upon effective date of redesignation. The federal PSD regulations found in 40 CFR 52.21 are the PSD rules


in effect for Alaska. These regulations will apply after Eagle River is redesignated as a maintenance area.

Subpart 4 of Part D established an attainment date of December 31, 1994 for Eagle River. Eagle River met this deadline. In addition, a milestone report demonstrating that Eagle River met the milestone requirements was submitted by MOA and approved by EPA in 1995 as required.

III.D.2.8. Maintenance Demonstration EPA guidance on the LMP option (Wegman, 2001) states that if an area qualifies for the LMP option “demonstration of maintenance is presumed to be satisfied.” Section III.D.2.4 of this document shows that monitored PM10 concentrations in Eagle River are low and “stable” enough to qualify for the LMP option. Thus, Eagle River has satisfied the maintenance demonstration requirement.

III.D.2.9. Demonstration of Permanent and Enforceable Emission Reductions As noted earlier in Section III.D.2.4, a large decline in PM10 concentrations has been observed in Eagle River and this decline is attributed primarily to the paving of local gravel roads in the area. In 1987, almost one-half of all the roads in the area (22 miles) were unpaved. By 2007 all of these roads were paved either with traditional hot asphalt paving or surfaced with RAP. The MOA is committed to the maintenance of these roads. In particular, all RAP-surfaced roads in the maintenance area have now been chip-sealed to improve their durability. The effective lifetime of these chip-sealed roads is estimated to be 10 to 15 years. When these roads have reached the end of their lifetime a new lift of chip seal (a mix of crushed aggregate or “chips” and asphalt emulsion) is applied which serves as a new wearing course for the road.

The MOA and the Alaska Department of Transportation and Public Facilities (ADOT&PF) have also implemented permanent changes in street maintenance practices on paved roads. Both the MOA and ADOT&PF have set new winter traction sand specifications that limit the amount fines or silt allowed in the material that is applied to roads within the MOA. In addition, the MOA is continuing to explore new and more efficient ways to improve road traction during snow and ice conditions without compromising air quality. New methods for controlling PM10 during the spring break-up period are being investigated. These include the use of chemical dust palliatives and the use of new technology “waterless” sweepers which offer promise of more thorough clean-up of roadways.

Eagle River has not violated the NAAQS since 1988; this is clear evidence that the controls implemented have provided permanent and enforceable emission reductions. The Anchorage Assembly recently adopted a revised land use code that requires paving of all streets except those in low density residential areas zoned R-6, R-7, R-8 or R-9.* * R-6, R-7, R-8 and R-9 are residential zoning designations defined in Title 21 of the Anchorage Municipal Code. R-7 zoning allows between one and two dwelling units per acre. The maximum dwelling unit density allowed in R-6, R-8 and R-9 varies from one per acre (R-6) to one per four acres (R-9).


Although most of the Eagle River maintenance area is “built out” and few new roads are likely to be constructed, the requirements stipulated in Anchorage Municipal Code 21.08.050 will help ensure that new streets constructed in the Municipality, including Eagle River, will not cause new PM10 problems.

The MOA is committed to continued maintenance of existing RAP/chip-sealed roads in the maintenance area and the MOA and ADOT&PF are committed to maintaining traction sand specifications that allow no more than 2% fines or silt. All controls that were relied on to demonstrate attainment will remain in place

III.D.2.10. Compliance with Air Quality Monitoring Requirements and Verification of Continued Attainment

According to CAA Section 110(a)(2), once an area is redesignated, the State must continue to operate an appropriate air monitoring network in accord with 40 CFR Part 58 to verify the attainment status of the area. The ADEC has delegated responsibility for air quality monitoring to the MOA. The MOA is committed to the continued operation of at least one EPA-approved PM10 monitoring site in the Eagle River maintenance area through the end of the maintenance planning period (2020). Monitoring will be conducted in accordance with 40 CFR Part 58.

Monitoring will be used to verify continued maintenance of the standard through the maintenance plan period. The MOA will annually recalculate the design value using the most recent five years of monitor data in order to verify the area continues to qualify for the LMP option. The result will be reported to the EPA.

In the event the area does not continue to qualify for the LMP option a full maintenance plan will be prepared as required by the LMP policy.

III.D.2.11. Natural Events Action Plan The MOA prepared a Natural Events Action Plan (NEAP) entitled A Natural Events Action Plan for Windblown Dust Events in Anchorage Alaska in September 2002. This plan was submitted to ADEC in response to a wind blown dust-related exceedance that occurred in Anchorage on March 18, 2001. ADEC forwarded the NEAP to EPA; EPA approved it on May 5, 2003. A copy of the NEAP is included in the Appendix to III.D.2.11.

One of the most important features of the NEAP is that it outlines procedures for issuing health advisories to help reduce PM10 exposure to the public during the events. However the issuance of health advisories for the Eagle River area have been impeded by a lack of “real time” PM10 monitoring data. Up until 2008, all PM10 data in Eagle River was collected using federal reference method (FRM) monitors. Because FRM monitoring requires that PM10 filter samples be retrieved after the required 24-hour sampling period, the data necessary to declare a health advisory are not available until the event is over. Although a health advisory was declared for the March 12, 2003 exceptional event in Eagle River, no such advisory was declared for the December 2, 2007 wind-blown dust


episode.* The MOA has now installed “real time,” continuous PM10 monitoring equipment in Eagle River that should remedy this shortcoming.

III.D.2.12. Contingency Provisions Section 175A of the CAA requires that a maintenance plan include contingency measures in order to promptly correct any violation of the standard that occurs after the redesignation of the area to attainment.† Normally, the implementation of contingency measures is triggered by a violation of the NAAQS. Contingency measures do not have to be fully adopted at the time of redesignation, but they must be readily adopted if they are triggered.

This section identifies a process and a timeline to identify and evaluate appropriate contingency measures in the event of a violation of the PM10 NAAQS.

Contingency Measures Assessment

Within 30 days following a violation of the PM10 NAAQS, the MOA will convene an assessment team to identify control measures that appropriately address the source(s) and circumstances causing the violation.

Within 120 days of the violation, the assessment team will prepare a report that identifies the cause or causes of the violation and recommends appropriate measures for mitigating future violations. The report shall be presented to the AMATS Policy Committee for review and adoption and then forwarded to the ADEC for approval.

The report should include an analysis of the PM10 monitoring data before and after the violation and a discussion of how the PM10 source or sources leading to the violation were determined. Other possible contributing factors such as weather conditions should be discussed. The effectiveness of existing controls, particularly those included in this maintenance plan, should be discussed and any lapses in the implementation of such controls should be identified.

The assessment team shall review the list of possible contingency measures offered in this Plan and recommend the implementation of one or more for them to address the

* A health advisory was issued during the March 12, 2003 episode because data from “real time” monitors in Anchorage indicated very high PM10 levels. Although data in Eagle River, 10 miles north were not available, PM10 concentrations were presumed to be high there also. However, on December 2, 2007 real time data from Anchorage suggested that PM10 concentrations were not likely to exceed the NAAQS. Without specific data for Eagle River, it was assumed that an exceedance was also unlikely there and no health advisory was declared. † The Eagle River PM10 Control Plan drafted in 1991 included two contingency measures. The first contingency measure called for the surfacing of two additional miles of gravel roadway in the nonattainment area with RAP. The second called for “sweetening” existing RAP roads with asphalt emulsion to improve their PM10 reduction effectiveness. Even though these measures were never triggered by a violation of NAAQS, all roads in the nonattainment area have now been surfaced with RAP or paved. In addition, all RAP roads have been enhanced with a chip-seal coating to improve their effectiveness at reducing dust and to increase their durability.


source or sources of the PM10 violation. The team has the option of recommending alternative measures not included on this list if circumstances warrant.

Local actions resulting from the assessment team recommendations will be at the discretion the Municipal Mayor and Assembly. Several of the possible contingency measures would require changes to local ordinance by the Anchorage Assembly before they could be implemented.

List of Potential Contingency Measures

The attainment inventory suggests that the primary sources of PM10 in Eagle River are traffic-related paved road dust emissions, wind blown dust emissions from roadways, parking lots and cleared areas, and fireplace and wood stove emissions. As such, if a future violation were to occur, a combination of one or more of these sources is most likely to be the cause. A list of potential contingency measures for each of these three sources follows: Traffic-Related Paved Road Dust

1. Apply chemical dust palliatives to high volume roadways upon prediction of high PM10.

The highest emissions typically occur along major roads during the spring break-up period when they are heavily laden with a winter’s worth of accumulated traction sand and other road sediment. Road sediment accumulates primarily in gutters, shoulders, medians and in the dividing strip between turn lanes and through lanes of high volume roadways. During the spring break-up period of 2008 the MOA performed a field study of the dust palliative magnesium chloride brine (MgCl2).* The study concluded that absent significant precipitation, an application of MgCl2 substantially reduced dust emissions for at least a week after application. This suggests that MgCl2 could be used to mitigate roadway PM10 emissions when concentrations are predicted to approach or exceed the NAAQS.

2. Sweep major roadways prior to spring break-up and other periods when elevated PM10 is anticipated.

Although sweeping has been included here as a potential contingency measure, it should be noted that its effectiveness and practicality as a control measure during the spring break-up period is questionable. Many studies have shown that without extensive back-flushing, traditional mechanical sweeping methods do not effectively reduce PM10 emissions. In late March and early April when PM10 is often highest, subfreezing temperatures make the use of water back-flushing impractical. Moreover, ice and snow on roadway shoulders prevent effective sweeping where the road is most heavily laden with sediment. The MOA is experimenting with alternatives to “traditional” sweeping such as post-sweep application of a dust palliative and/or “double-pass” waterless sweeping. The MOA plans to continue to

* A draft report, entitled Field Evaluation of Suitability of Magnesium Chloride Brine for PM10 Control on Paved Roads in Anchorage was completed by the MOA Department of Health and Human Services in September 2008.


experiment with alternative sweeping procedures and one or more may prove viable as a contingency measure in the future.

Wind-blown Dust from Roadways, Parking Lots and Cleared Areas

1. Implement one or more of the traffic-related paved road dust measures discussed above.

Paved roadways comprise over 75% of the cleared area in the Eagle River PM10 maintenance area. Thus, the same measures suggested for controlling traffic-related PM10 emissions are suitable for reducing wind blown dust. For example, the application of MgCl2 brine would also be expected to reduce wind-generated dust from roads.

2. Require application of dust palliatives to paved parking areas.

Parking lots, playgrounds and other similar paved areas comprise about 20% of the cleared area in the maintenance area. The application of dust palliatives to these areas would be expected to reduce emissions.

3. Establish required specifications for traction sand materials applied to parking lots.

Currently there are no requirements placed on the quality or quantity of traction sand materials applied to parking lots. New MOA regulations could be established that would limit the amount of fines or silt allowed in the traction sand applied to contiguous parking lots and paved areas greater than five acres in size, for example.

Fireplaces and Wood Stoves

1. Curtail fireplace and wood stove use when high PM10 is predicted.

Although fireplace and wood stove emissions currently make up a relatively small part of total PM10 emissions, it is possible that future increases in natural gas heating costs could drive more households to heat with wood. If this is the case, emissions of PM10 would increase over time. Presumably air quality monitoring data would provide evidence if such a trend were occurring. An increase in wood heating would likely jeopardize attainment of the PM2.5 (fine particulate) NAAQS before PM10. Nevertheless, in some circumstances it may be appropriate to consider regulating fire place and wood stove use as means to addressing PM10 violations.

III.D.2.13. Air Quality Conformity for LMP Areas The transportation conformity rule and general conformity rule apply to nonattainment and maintenance areas. Under either rule, an acceptable method of demonstrating that a federal action conforms to the applicable SIP is to demonstrate that expected emissions from the planned action are consistent with emissions budget for the area.

Although EPA policy does not exempt LMP areas from the need to demonstrate conformity, it allows the area to do so without submitting an emissions budget, because data demonstrates no violation of the NAAQS will occur due to reasonable growth


projections. For transportation purposes, the emissions in a qualifying LMP area need not be capped for the maintenance period and thus no regional emissions analysis is required. Regional transportation conformity is presumed due to the limited potential for emission growth in the area during the LMP period. A regional emissions analysis and associated regional conformity requirements (40 CFR 93.118 and 93.119) are no longer necessary. Similarly, federal actions subject to the general conformity rule would automatically satisfy the “budget test’ specified in Section 93.158(a)(5)(i)(A) for the same reasons.

When Eagle River is designated by EPA as a LMP, transportation conformity determinations will still be required for transportation plans, programs (TIPs) and projects. The conformity determination for the plan and TIP should state that a regional emission analysis is not required because the area has an approved LMP. The Plan and the TIP must still be made available for public review. The portions of the conformity rule that still apply are found in 40 CFR 93.112 and 93.113 and the consultation requirements as specified under state regulation, 18 AAC 50 .715 and 50.720.

In addition transportation projects would still need to meet the criteria for PM10 hot spots (40 CFR 93.116 and 93.123) and for PM10 control measures (40 CFR 93.117). The MOA will work with ADEC and interested parties to develop an evaluation criteria and process to meet these transportation conformity requirements.

III.D.2.14. Redesignation Request The MOA and ADEC believe this document contains all necessary information and adequately demonstrates that Eagle River should be reclassified to attainment under the LMP option. Therefore, ADEC, on behalf of the MOA, requests that EPA find this plan complete and approve the redesignation of the Eagle River nonattainment area to attainment under the LMP option.

Appendices to the

Eagle River

PM10 Limited Maintenance Plan

Appendix to III.D.2.5 Eagle River PM10 Limited Maintenance Plan Final Draft 11/05/09

Appendix to III.D.2.5

PM10 design values for Eagle River and qualification for Limited Maintenance Plan

Computation of 24-hr Design Value Computational methods for determining the 24-hour design value (DV) are outlined in the PM10 SIP Development Guideline (EPA-450/2-86-001, June 1987). The empirical frequency distribution approach (see Section 6.3.3. of the guideline) was used to determine the site-specific PM10 concentration that would be expected to be exceeded at a frequency of once every 365 days.

To do so, we first ranked all observations by PM10 concentration for each 3-yr block during the 1998 – 2007 period in descending order. Because PM10 concentrations were monitored generally on a one-in-six-days basis, each 3-yr block had approximately 180 observations (thus the lowest concentration measured in each 3-yr block had a rank order ≈ 180).

Next, for a concentration ranked (i), the proportion of PM10 observations that exceed that concentration is calculated as:

i / total number of observations

The empirical frequency distribution for each 3-yr block was then graphed by plotting the proportion of occurrence against PM10 concentrations (an example of 2004-2006 period is shown in Figure 1, Line a). Because by definition the DV is a concentration that corresponds to an exceedance frequency of 1/365 (Line b), the DV was graphically determined as the intersecting point of Lines a and b in the Figure 1.

Figure 1 Example - Determination of 24-hr DV for 2004-2006.

y = 1.2831e-0.0697x

R2 = 0.9823

0.001

0.010

0.100

1.000

10.000

0 20 40 60 80 100 120

PM10 concentration (μg m-3)

Prop

rotio

n of

occ

urra

nce

exce

edin

g th

e co

nc.

a

b DV frequency (1/365 = 0.0027)

88.2

Line a = the empirical frequency distribution for all the observations during the 2004-2006 period. Line b = DV frequency by definition (1/365). Total number of observations = 181. For this particular period, DV was determined to be 88.2 μg/m3.


Table 1 below shows calculated DV’s for the last decade, all eight 3-yr blocks, to demonstrate that there is no increasing trend in DV’s over this period. The average DV during the last 5-yr period (2003-2007) was 92.3 µg/m3. This is under 98 µg/m3 and therefore meets the qualification for the LMP option.

Table 1

Computation of Average DV for Parkgate Site in Eagle River

3-yr Period

Equation of Line Describing Empirical Frequency Distribution

++ R2

DV (computed from previous

3 years data using empirical frequency distribution)

(µg/m3) 1998-2000 y = 1.4749e-0.0744x 0.960 84.5 1999-2001 y = 1.28522e-0.0643x 0.962 95.5 2000-2002 y = 1.41446e-0.0697x 0.984 89.7 2001-2003 y = 1.1840e-0.0562x 0.944 108.0 2002-2004 y = 1.3124e-0.0656x 0.968 94.1 2003-2005 y = 1.1248e-0.0586x 0.969 102.7 2004-2006 y = 1.2831e-0.0697x 0.982 88.2 2005-2007 y = 1.3049e-0.0717x 0.979 86.0

Average DV 2003-2007 = 92.3 µg/m3

LMP Qualification Criteria < 98 µg/m3 ++ In this equation y is the proportions of concentrations exceeding a particular PM10 concentration and x is the concentration of interest. If y is set = 1/365 = 0.0027, the equation can be used to solve for x, the concentration that would be expected to be exceeded once per year.


Computation of a Site-Specific Design Value Attachment A of the Limited Maintenance Plan guidance (Wegman memo, EPA, August 9, 2001) outlines a procedure for computing a site-specific value (called a critical design value or CDV) that may serve as alternative to the 98 µg/m3 value used to determine whether an area qualifies for the LMP option or meets the Motor Vehicle Regional Emissions Analysis Test. The computation is described below:

CDV = NAAQS/(1+tcCV)

Where:

CDV = the critical design value

CV = the coefficient of variation of the annual design values (the ratio of standard deviation divided by the mean design value in the past)

tc = the critical one-tail t-value corresponding to a given probability of exceeding the NAAQS in the future and the degree of freedom in the estimate for the CV.

EPA Region 10 staff has recommended that a probability of 5% be assumed to determine the appropriate critical one-tail t value (tc) in the computation.

Table 2 24-hour CDV (µg/m3) for Eagle River.

Parameter 24hr-CDV

(µg/m3)Average DV 92.3

SD 9.1CV 0.098

n 3df 2

tc (5%, one-tail) 2.920CDV 116.6

The computed CDV for Eagle River is 116.6 µg/m3. This means that, based on the magnitude of the eight annual DV’s computed for Eagle River between 2000 and 2007 and their year-to-year variability, there is only an expected 5% probability that the average DV would be higher than 116.6 µg/m3

at the Parkgate site. The site-specific criterion is considerably higher than the “default” value of 98 µg/m3. This higher site-specific value was used as a margin of safety (MOS) value in the Motor Vehicle Regional Emissions Analysis Test.

Appendix to III.D.2-6 of Eagle River Limited Maintenance Plan Final Draft 11/05/09

Appendix to III.D.2.6 2007 and 2020 PM10 Emission Inventories for the Eagle River Limited Maintenance Area

Overview This document describes the assumptions and methods used to develop the 2007 base year PM10 attainment inventory and the projected inventory for year 2020. The 1987 inventory is also shown for illustrative purposes. Emissions from significant sources within the 9 km2 area were estimated using standard methodologies outlined in AP-42 for fugitive PM10 sources. MOBILE6.2 was used to estimate the contribution of motor vehicle exhaust, tire and brake wear emissions to PM10. As will be shown in the inventory, the large majority of PM10 emitted in the maintenance area is of “crustal” or geological origin. The emission inventory will show that the two most significant sources of this crustal material are the “dust” stirred up by vehicle traffic travelling on paved roadways and wind-lofted dust from roads, parking lots and un-vegetated areas within the maintenance area. This finding is consistent with past source apportionment studies that have consistently shown that the vast majority of PM10 in Eagle River and Anchorage consists of crustal material.*

In 1991, when the attainment plan for Eagle River was prepared, the most important source of PM10 was unpaved roads. Since that time, however, all of the roads in the area have been paved so unpaved road emissions are no longer included in the inventory. For this maintenance plan, the five PM10 source categories were identified and inventoried within the Eagle River maintenance area. These include (1) dust from paved roads; (2) wind-generated dust from roads, parking lots and un-vegetated areas; (3) fireplaces and woodstoves; (4) natural gas combustion; and (5) exhaust, tire and brake wear emissions from motor vehicles.

AP-42, “Compilation of Air Pollution Emissions Factors,” is an EPA publication that provides guidance on the estimation of emissions on a large variety of air pollution emission sources. AP-42 was used to estimate emissions for all of the above sources except exhaust, tire and brake wear emissions. These emissions were estimated using the EPA MOBILE6.2 emission factor model. The methods and assumptions used to estimate emissions from each of these sources is described in the next five sections.

* Four studies have been performed to characterize the sources of particulate and Anchorage and Eagle River. These include two chemical mass balance/source apportionment studies (Pritchett & Cooper, 1985, Cooper & Vodovinos, 1988) and two studies that used microscopy (Crutcher, 1994, R.J. Lee, Inc., 1995) to identify and quantify the types (and probable sources) of particulate.


(1) Dust from Paved Roads Dust from paved roads is a major source of PM10 in Eagle River and Anchorage. Roads are often laden with large amounts of “sediment” and other fine-grained minerals left over from winter sanding operations, material abraded from the road surface itself by traffic (especially from vehicles equipped with studded tires), and spillage from hauling activities. Roads tend to be dirtiest during the spring break-up period which generally occurs between mid-March and the end of April. Although the grain size of most of the sediment on the roads is too large to be PM10, some of this material has been pulverized to a grain size less than 10 microns. When these very fine grained particles are re-entrained into the air by turbulence from traffic travelling on the road, they become PM10.

Section 13.2.1 of AP-42 outlines procedures for estimating PM10 emissions from paved roads. According to AP-42, emissions from a paved road are a function of how much fine-grained sediment or silt is on the road and the weight of vehicles using the road. * Paved road emissions increase in direct proportion to the amount of traffic or vehicle miles travelled (VMT) on the roads. Higher traffic volumes result in greater emissions.

VMT Estimation

The air quality conformity analysis for the 2007 Chugiak-Eagle River Long Range Transportation Plan (CE/LRTP) included VMT estimates for analysis years 2007, 2017, and 2027. These VMT estimates served as the basis for the 2007 and 2020 inventories presented here. The CE/LRTP VMT estimates for 2007 in the 2007 base year attainment inventory and 2020 was estimated by interpolating between CE/LRTP projections for analysis years 2017 and 2027.

In the conformity analysis for the CE/LRTP, the FHWA-approved Anchorage Transportation Model was used to estimate VMT on arterials and freeways in the Eagle River Maintenance area. The model did not provide VMT estimates for local roads, however. VMT on local roads was estimated by assuming that each household within the maintenance area makes seven home-based trips per day, each involving 0.62 miles of travel on local roads.† Each household was assumed to generate 4.34 miles (7 trips x 0.62 m) of local road VMT each day.

Table 1 shows VMT estimates by roadway type.

* Silt is defined as the finer-grained soil particles that pass a #200 mesh sieve; these are particles nominally 75 microns and smaller. † For example, a trip from home to the local grocery store and back would count as two home-based trips.


Table 1.

Estimated and Projected VMT in Eagle River PM10 Maintenance Area Base Year 2007 and End of 10-Year Maintenance Planning Period 2020

Local Road VMT

(based on housing Stock)

Arterial and Freeway VMT (Anchorage Transportation

Model estimates)

Housing

Stock

LocalUnpaved

VMT

Paved (RAP)±

VMT

Paved (SP/CG)**

VMT

Arterials Glenn Hwy

2007 4,548 0 7,659 12,079 68,664 77,532

2017 4,908 0 8,264 13,034 83,370 107,640

2020 5,015 0 8,446 13,321 87,782 116,672

2027 5,267 0 8,870 13,989 98,076 137,748

± RAP = recycled asphalt pavement ** SP/CG = strip paved or curb and gutter

Paved Road Emission Factor

Section 13.2.1 of AP-42 (updated November 2006) outlines recommended procedures for estimating PM10 emissions from paved roads. The paved road emission factor, the amount of PM10 generated in pounds per vehicle mile travelled (VMT), is a function of the “silt loading” on the road and the average weight of the vehicles travelling on the road.

The AP-42 paved road emission factor equation is:

E = k(sL/2)0.65 x (W/3)1.5 –C where

E = PM10 emissions in lbs/VMT k = 0.016 (AP-42 specified particle size multiplier for PM10) sL = road surface silt loading (varies by roadway type) W = mean vehicle weight in tons (assumed to be 2 tons) C = vehicle exhaust, tire and brake wear emissions (AP-42 recommendation = 0.00047 lbs/VMT)

Data collected in Anchorage in 1996 (Montgomery-Watson, 1996) showed that silt loading varied by roadway type. (For this inventory Eagle River was assumed to have silt loadings identical to Anchorage.)

The Municipality of Anchorage maintains a detailed inventory of the surface treatment of roads in the Chugiak – Eagle River area. While the majority of the roads in the area are paved with “traditional” hot asphalt paving (HAP) about one-third of the local roads in the maintenance area are constructed with recycled asphalt paving or RAP. Although air quality monitoring data suggest RAP treatment has proven to be an effective means in reducing PM10 from gravel roads in Eagle River, the surface of these roads is less durable and more erodible than those constructed using HAP. Because roadway abrasion is a significant source of silt on roads, it seems reasonable to assume that the silt loadings on


RAP roads are higher than those surfaced with HAP.* For the purpose of this inventory, RAP-constructed roads were assumed to have silt loadings twice those constructed with HAP.

Table 2 shows average silt loading measurements and the computed AP-42 PM10 emission factor for each roadway type for the spring and fall PM10 seasons.

Table 2 Typical Silt Loadings and PM10 Emission Factors by Season for Paved Roads in Eagle River

Spring Break-up Period Fall Freeze-up Period

Silt loading (g/ m2)

Spring PM10 Emission Factor

(lbs/VMT)

Silt loading (g/ m2)

Fall PM10 Emission Factor

(lbs/VMT)Arterial Paved Roads 6.7 0.0207 1.1 0.0061Freeways (Glenn Hwy) 20.4 0.0433 2.6 0.0110Local Paved Roads (hot asphalt paving) 18.4 0.0404 4.7 0.0164Local Paved Roads (recycled asphalt) 36.8# 0.0637 9.4# 0.0260

# Silt loading estimated to be double those of local roads constructed with hot asphalt paving.

Using AP-42 Emission Factors and VMT Estimates to Compute Paved Road PM10 Emissions

Paved road PM10 emissions can be readily computed from the emission factor and VMT on each roadway type. Table 3 shows estimated emissions for the spring and fall periods for base year 2007 and for the end of the maintenance period in 2020.

Table 3

Estimated PM10 Emissions from Paved Roads in the Eagle River Maintenance Area 2007 and 2020

2007 2020

Roadway Type VMT

SpringEmissions(tons/day)

FallEmissions(tons/day)

VMT

Spring Emissions (tons/day)

FallEmissions(tons/day)

Arterial Paved Roads 68,664 0.71 0.21 87,782 0.91 0.27 Freeways (Glenn Hwy) 77,532 1.68 0.43 116,672 2.52 0.64 Local Roads (hot asphalt paving) 12,111 0.24 0.10 13,356 0.27 0.11 Local Roads (recycled asphalt) 7,627 0.24 0.10 8,411 0.27 0.11

TOTAL 165,934 2.88 0.83

226,221 3.97 1.13

* The Municipality of Anchorage recently completed a study that suggests that roadway abrasion is the source of about 25% of the “dirt” on the road surface during spring break-up.


(2) Wind Generated Dust from Roads, Parking Lots and Un-Vegetated Areas Although EPA guidance allows the flagging of PM10 exceedances that occur as a result of extreme wind events such as those that occurred on March 12, 2003 and December 2, 2007 in Eagle River, PM10 observations resulting from commonly occurring, less energetic wind-related events are considered valid data and are not excluded when determining the design value for an area or determining whether the area is in compliance with the NAAQS. Monitoring data suggest that wind-generated dust frequently contributes to elevated PM10 concentrations in Eagle River.

Estimating the Amount of Area Covered by Roads, Parking Lots and Un-vegetated Areas

Wind-generated dust generally originates from paved surfaces laden with dirt and silt. These paved surfaces include roadways and parking lots in the maintenance area. There are also some cleared, un-vegetated areas that are unpaved.

Estimates of the amount of area available for the generation of windblown dust are shown in Table 4. The area amount of roadway was estimated by the length of each type of roadway and the average width of that type of roadway. For example, there are 6.2 miles of arterial roadway in the maintenance area and arterial roadways have an average paved width of approximately 60 feet.

The surface area of the arterial roadways in the maintenance area is therefore:

(6.2 miles length)(5,280 ft/mi)(60 ft width) = 1,964,160 ft2

1,964,160 ft2 / 43,560 ft2/acre = 45.1 acres

The amount of acreage covered by parking lots, paved school playgrounds, and similar areas was estimated by inspecting Google satellite photos of the maintenance area. The acreage of un-vegetated, cleared areas was estimated in like manner. The Google map utility includes a distance key that allows the dimensions and acreage of a particular surface feature to be estimated. For example, a parking lot with dimensions of 250 feet by 500 feet is approximately 3 acres in size. Because parking areas, particularly those serving retail establishments serve the local population, we assumed that the total area covered by parking lots and the like would increase in direct proportion with housing stock. Housing stock is projected to increase by 10.3% between 2007 and 2020; paved parking areas were assumed to increase by a like proportion.

The total amount of paved or cleared area in the maintenance area in base year 2007 was estimated to be 289 acres. This constitutes about 12.5% of the land surface in the maintenance area.


Table 4 Estimated Surface Area Coverage of Roads, Parking Lots and Un-vegetated Areas in

Eagle River PM10 Maintenance Area

2007 2020

RoadwayLength(miles)

Estimated Area

(acres)

RoadwayLength(miles)

Estimated Area

(acres)

Glenn Highway 1.1 13 1.1 13 Arterials 6.2 45 6.2 45

Local Roads 45.6 165 45.6 165 Parking Lots ---- 55 ---- 62

Un-vegetated Areas ---- 10 ---- 10 TOTAL 289 296

Note: To compute the total paved area of roadways, a paved width of 100 feet was assumed for the Glenn Highway, 60 feet for arterials, and 30 feet for local roads.

Wind Blown Dust Emission Factor Estimation

AP-42 does not provide an emission factor methodology specific to estimating PM10 emission from roads, parking lots and un-vegetated areas. However, it does outline a methodology (see AP-42 Section 13.2.5.1) for estimating emissions from aggregate storage piles and open areas within an industrial facility. After examining other alternatives, the methodology recommended for estimating wind-generated PM10 emissions from open areas in industrial facilities seemed to offer the best fit available for estimating wind-generated PM10 in Eagle River.

The AP-42 Section 13.2.5.1 outlines a step-by-step procedure for estimating wind generated PM10 emission factor for open areas in industrial facilities. This methodology was applied to the estimation of emissions from open areas in Eagle River.

AP-42 provides the following equation for estimating PM10 emissions from wind blown dust:

Equation 1

EFwind = 0.5(58(u* - ut*)2 + 25 (u* - ut

*)) where:

u* = friction velocity (m/s) ut

* = threshold friction velocity (m/s)

The next two sub-sections will describe how the variables ut* and u* were determined.


Determining ut*

AP-42 outlines a field procedure and lab test (sieve analysis) for estimating the threshold friction velocity (ut

*). The mode of the aggregate size distribution is determined and can be related empirically (see AP-42 Table 13.2.5-1) to ut

*. In order to estimate ut

* for the

aggregate material in the Eagle River maintenance area, existing sieve analysis data from street sediment collected in Anchorage was used.* Over 300 street sediment samples were collected and sieved. Although the sieves used in this analysis did not correspond exactly to those prescribed in Table 13.2.5-1, they were similar enough so that a reasonable estimate of ut

* could be made.† The mode size was determined from the

average of all 300+ sieve analysis results. On average, 24.9% of the total street sediment was “captured” between sieves #40 (0.42 mm) and #100 (0.149 mm). The midpoint size between these two sieves is 0.285 mm (See Figure 1).

Figure 1 Sieve Analysis Results for Anchorage Street Sediment Data

4.8

13.8 13.9 14.1

24.9

7.6

0.0

5.0

10.0

15.0

20.0

25.0

30.0

4.76 - 9.5(7.13)

2.00 - 4.76(3.38)

0.84 - 2.00(1.42)

0.42 - 0.84(0.63)

0.149 - 0.42(0.285)

0.105 - 0.149(0.127)

Size range, (mid-point)(values in mm)

% in

siz

e ra

nge

mode of aggregate size distribution

Table 13.2.5-1 recommends a value for ut* = 0.43 m/s for a midpoint size range of 0.375

mm. Again, because different sieves were used to characterize the size distribution of Anchorage road sediment than prescribed by AP-42, our midpoint value is slightly different. Nevertheless the data suggest that 0.43 m/s is a reasonable assumption of ut

* for Eagle River road sediment.

* These data were collected in spring of 1996 by Montgomery-Watson, Inc. for the MOA Watershed Management Section as part of an analysis of street sediment impacts on streams and lakes in Anchorage. † The sieves used in the Anchorage street sediment testing were #4, #9, #20, and #100. The method recommends using sieves #5, #9, #16, #32, and #60.


Determining u*

The friction wind velocity (u*) is the estimated wind velocity at the ground surface where street sediment and other fine materials lay available for re-entrainment by the wind. Wind speed measurements are taken at 10 meters above the ground (u10

+), however. The actual wind speed at the ground surface is significantly lower. AP-42 recommends the following equation to estimate u*:

u* = 0.053 u10+ (expressed in m/sec)

In order to estimate the contribution of wind blown dust to PM10, we identified the five highest PM10 days during spring break-up (March, April) and fall freeze-up (October, November) over the 10-year period 1998-2007. We excluded the two designated exceptional events that resulted from wind/dust storms occurred on March 12, 2003 and December 2, 2007.* We examined local climatological data and determined the maximum wind speed (maximum 2-minute observations) that occurred on each of those days.† The friction velocity was selected from the spring and fall days with the highest wind speed.

Results of this analysis are shown in Table 5.

Table 5 Equivalent Friction Wind Velocities on High PM10 Days During Spring Break-up and Fall Freeze-up (1998-2007)

Date PM10

(µg/m3)

Max 2-min

Wind Spd u10

+ (mph)

Equivalent Friction Wind

Velocity u*

(m/s) Date PM10

(µg/m3)

Max 2-min

Wind Spd u10

+ (mph)

Equivalent Friction Wind

Velocity u*

(m/s) 3/10/2003 92 23 0.55 11/13/2006 65 16 0.38 3/17/2005 90 15 0.36 11/7/1998 55 7 0.17 3/4/2003 82 23 0.55 10/21/2000 52 20 0.47 4/15/2004 70 8 0.19 10/31/2005 51 14 0.33 3/14/2001 69 13 0.31 11/7/2006 48 20 0.47

Selected value for u* = 0.55 Selected value for u* = 0.47

* The highest two-minute wind speed measured on March 12, 2003 was 52 mph and on December 2, 2007 two-minute winds reached 48 mph. † Because there are no comprehensive wind data available for Eagle River, local climatological data from the Ted Stevens Anchorage International Airport were used.


Computing the Wind Blown Dust Emission Factor from Equation (1)

Now that the threshold friction velocity ut* and equivalent wind friction velocity u* have

been determined for the spring and fall PM10 seasons, we can use Equation 1 to compute the PM10 emission factor for wind blown dust.

(Equation 1) EFwind = 0.5(58(u* - ut*)2 + 25 (u* - ut

*)) Substituting values for ut

*= 0.43 m/sec and u* = 0.55 m/s (spring) and 0.47 m/s (fall), the resultant spring and fall wind blown dust PM10 emission factor are:

Spring Windblown Dust PM10 Emission Factor = 1.9 g/m2/day = 17 lbs/acre/day

Fall Windblown Dust PM10 Emission Factor = 0.5 g/m2/day =5 lbs/acre/day

Estimated Wind blown PM10 Emissions for 2007 and 2020

Now that the emission factor and the amount of cleared acreage in the Eagle PM10 maintenance area have been estimated, PM10 emissions can be readily calculated. Computed emissions are shown in Table 6.

Table 6

Estimated Windblown Dust PM10 Emissions

Spring Break-up Fall Freeze-up

Year

Cleared Areas:

Roadways, Parking Lots, Miscellaneous (total acres)

Wind blown Dust

PM10 Emission

Factor (lbs/acre)

Total PM10 Emissions (tons/day)

Wind blown Dust PM10 Emission

Factor (lbs/acre)

Total PM10 Emissions (tons/day)

2007 289 17 2.47 5 0.70 2020 296 17 2.53 5 0.72

(3) Fireplaces and Woodstoves Basic assumptions regarding fireplace and wood stove were obtained from a telephone survey conducted by ASK Marketing and Research in 1990. This survey asked Anchorage residents how many hours per week they burned wood in their fireplace or wood stove. Because the AP-42 emission factors for fireplaces and wood stoves (See AP-42, Sections 1.9 and 1.10) are based on the amount of wood (dry weight) burned, hourly usage rates from the survey had to be converted into consumption rates. Based on discussions between MOA and several reliable sources (OMNI Environmental Services, Virginia Polytechnic Institute, Colorado Department of Health), average burning rates (in wet weight) of 11 pounds per hour for fireplaces and 3.5 pounds per hour for wood stoves were assumed.

Residential wood burning assumptions are detailed in Table 7.*

* Assumptions regarding wood burning activity levels (i.e. the number of households engaging in wood burning on a winter season design day) were corroborated by a more recent telephone survey conducted by


Table 7

Estimation of Residential Wood Burning PM10 Emission Factors for Eagle River

Device

Average use per weekday (hours per household per day)

Average dry weight of wood

consumed (lbs per hour)*

Average amount of

wood burned per household (dry lbs / day)

AP-42 Emission Factor for PM10 (g/dry lb wood

burned)

Estimated PM10 emissions per

household (g/day)

Fireplaces 1.04 7.15 lbs/hr 7.44 7.9 58.8

Wood Stoves 0.85 2.275 lbs/hr 1.94 5.4** 10.5 TOTAL Fireplaces + wood stoves 1.89 ------ 9.38 ------ 69.3

* The moisture content of wood burned was assumed to be 35%. Thus, dry burning rates were 65% of wet

rates.

** The wood stove emission factor was determined by assuming that the wood stove population in Eagle River is comprised of equal proportions of conventional, catalyst, and non-catalyst stoves. The emission factor above was calculated as the weighted average of the AP-42 emission factors for each stove type. AP-42, 5th Edition (Oct 1996)

PM10 emissions from residential wood burning can be estimated from the emission factor computed above and the estimated number of households. Table 8 shows estimated PM10 emissions from residential wood burning for base year 2007 and for year 2020. Wood burning rates per household were assumed to be the same in 2007 and 2020.

Table 8 Estimated PM10 Emissions from Residential Wood Burning in Eagle River Maintenance Area

2007 and 2020

Year Housing Stock in Inventory Area

AP-42 PM10 Wood Burning Emission Factor for

Eagle River (g/household/day)

Estimated PM10 Emissions from

Fireplaces and Woodstoves (tons/day)

2007 4,548 64.5 0.32

2020 5,015 64.5 0.36

In 2003 Ivan Moore Research (IMR) asked approximately 600 Anchorage residents whether they had used their fireplace or woodstove during the preceding day. The survey was conducted when the preceding day had a minimum temperature between 5 and 15 ºF. Although the IMR survey did not provide as detailed information as the ASK survey, its results were roughly consistent with the assumptions used in this inventory.


(4) Natural Gas Combustion Natural gas is the main fuel source for space heating in the Municipality of Anchorage, including Eagle River. Survey information suggests that the vast majority of households use natural gas as their primary source of heat. Average household natural gas consumption during a peak heating day in the winter in the Anchorage area has been estimated to be 658 ft3/day.* We, however, were interested in estimating natural gas consumption (and consequent PM10 emissions) during spring break-up and fall freeze-up when temperatures are warmer. Estimates of peak household natural gas consumption were estimated for a day when the average ambient temperature was approximately -10 ºF while the typical average daily temperature during the spring and fall PM10 seasons is approximately +30 ºF. Natural gas consumption for a +30 ºF day can be estimated from consumption on a -10 ºF day by assuming that consumption is proportional to heating degrees.† The computation is as follows.

Peak-day natural gas consumption per household = 658 ft3/day

Ambient temperature on day of peak natural gas consumption = -10 ºF, heating degrees = 75

Ambient temperature on typical fall or spring day in PM10 season = +30 ºF, heating degrees = 35

Assume natural gas consumption is proportional to heating degree days, then

Natural gas consumption during fall or spring PM10 day = 658 ft3/day x (35/75) = 307 ft3/day

The Eagle River maintenance area is predominantly residential. While there are some commercial natural gas users, there is little if any industrial or utility usage. Because “non-residential use” is relatively small within the maintenance area, it seemed reasonable to assume that combined commercial and industrial use would be no more than 50% of residential. Thus, for the purpose of this inventory, total natural gas use was assumed to be 150% of estimated residential use.

The emission factor for “total” particulate matter (see AP-42 Section 1.4, July 1998) is estimated to be 7.6 lbs per 106 ft3 of natural gas consumed. PM10 emissions from natural gas combustion in the Eagle River maintenance area can be readily computed from the amount of gas consumed and this emission factor. Table 9 shows the results of this computation.

* For details see “Anchorage 2007 CO Emission Inventory and 2007-2023 Projections,” Municipality of Anchorage, January 2008. † Heating degrees are computed as the difference between 65 ºF and the average ambient temperature. For example, if the average temperature is 30 ºF, heating degrees = 65 -30 = 35.


Table 9 Estimation of PM10 Emissions from Natural Gas Combustion in Eagle River Maintenance Area

Natural Gas Consumption

per Household

(ft3) Housing

Stock

Total Residential Natural Gas

Consumption (ft3)

Estimated Commercial

and Industrial


(ft3)

Combined Residential, Commercial

and Industrial


(ft3)

AP-42 PM10

Emission Factor (lbs per 106 ft3)

Estimated PM10

Emissions (tons/day)

2007 307 4,548 1.39 x 106 0.7 x 106 2.08 x 106 7.6 0.008 2020 307 5,015 1.54 x 106 0.7 x 106 2.31 x 106 7.6 0.009

(5) Exhaust, Tire and Brake Wear Emissions from Motor Vehicles In addition to the PM10 that vehicles stir-up as they travel along dirty roadways, motor vehicles are also responsible for some “direct” PM10 emissions. These include tail pipe exhaust emissions, and the emissions that result from tire and break wear. These emissions can be estimated by using the EPA mobile source emission factor model called MOBILE6.2. MOBILE6.2 allows the vehicle fleet characteristics of a particular area such as the proportion of diesels in the fleet, age distribution of the fleet and the stringency of the vehicle inspection and maintenance program to taken into account when estimating emissions. Fuel characteristics such as gasoline and diesel fuel sulfur content are also accounted for in the modeling process.

MOBILE6.2 was used to estimate the PM10 emission factors for exhaust, tire and brake wear emissions for the Anchorage fleet in base year 2007 and in 2020, the end of the maintenance planning period. The model produces emission factor estimates in grams per VMT. Thus, if VMT is known, emissions can be readily computed as the product of the emission factor and VMT estimate. Table 10 shows the results of the MOBLE6.2 emission factor modeling and consequent estimates of PM10 emissions. As can be seen in the Table, exhaust, tire and break wear emissions are small. For example, road dust emissions are more than 100 times greater than the combined contribution of exhaust, tire and brake wear emissions.

Table 10

Estimated PM10 Emissions from Motor Vehicle Exhaust, Tire Wear and Brake Wear in Eagle River Maintenance Area - 2007 and 2020

2007 2020

MOBILE6.2 Emission

Factor (g/mi) VMT

PM10 Emissions(tons/day)

MOBILE6.2Emission

Factor(g/mi) VMT

PM10 Emissions(tons/day)

Tail Pipe Exhaust 0.0046 165,934 0.0008

0.0037 226,221 0.0009

Brake Wear 0.0125 165,934 0.0023 0.0125 226,221 0.0031 Tire Wear 0.0085 165,934 0.0016 0.0085 226,221 0.0021 TOTAL COMBINED

0.0047

0.0061


Eagle River PM10 Emissions Inventory Summary The Eagle River PM10 emissions inventories for 2007 and 2020 are summarized in Table 11. Separate inventories are provided for the two peak PM10 periods, fall freeze-up and spring break-up.

As can be seen in the Table, the most significant sources of PM10 in the Eagle River maintenance area are paved roads, wind blown dust, and fireplaces and wood stoves.

Table 11

Eagle River Limited Maintenance Area PM10 Emissions Inventory All Emissions in tons/day with % of Total

Spring Break-up (March, April)

Fall Freeze-up (October, November)

Source Category 2007 2020 2007 2020

Paved Roads 2.88

(50.6%) 3.97

(57.8%) 0.83

(44.4%) 1.13

(50.8%) Wind blown Dust from Paved Roads, Parking Lots and Un-Vegetated Areas

2.47 (43.5%)

2.53 (36.8%)

0.70 (37.6%)

0.72 (32.5%)

Fireplaces and Wood Stoves 0.32

(5.7%) 0.36

(5.2%) 0.32

(17.3%) 0.36

(16.1%)

Natural Gas Combustion 0.008

(0.1%) 0.009

(0.1%) 0.008

(0.4%) 0.009

(0.4%) Exhaust, Tire and Brake Wear Emissions from Motor Vehicles

0.005 (0.1%)

0.006 (0.1%)

0.005 (0.3%)

0.006 (0.3%)

TOTAL 5.69

(100%) 6.87

(100%) 1.87

(100%) 2.22

(100%)


Appendix to III.D.2.11

Natural Events Action Plan Note: The Natural Events Action Plan included here is subject to periodic updates. Therefore this appendix may not include the latest version.

Natural Events Action Plan for

Windblown Dust Events in Anchorage, Alaska

Municipality of Anchorage

Department of Health and Human Services

Environmental Services Division

Environmental Quality Section

September 2002

Natural Events Action Plan for Windblown Dust Events in Anchorage, Alaska

Introduction On March 18, 2001 the 24-hour average PM-10 concentration measured at the Muldoon monitoring station in east Anchorage was 180 μg/m3

(micrograms per cubic meter), exceeding the national ambient air quality standard of 150 μg/m3 . These elevated levels of PM-10 were attributed to blowing dust generated by high winds. Sustained winds of 30 to 35 miles per hour, and peak gusts of up to 60 miles per hour were recorded at National Weather Service monitoring stations in Anchorage. The Municipality of Anchorage (MOA) has requested the Environmental Protection Agency (EPA) exclude the data from this event because the high PM-10 concentrations measured have been attributed to an uncontrollable natural event as defined in the EPA Natural Events Policy1. The Natural Events Policy allows EPA to exercise its discretion under Section 107(d)(3) of the Clean Air Act not to designate area as nonattainment if the State develops and implements a plan to respond to the health impacts of natural events. The Municipality of Anchorage Department of Health and Human Services (DHHS) is submitting this Natural Events Action Plan to the EPA through the Alaska Department of Environmental Conservation in conformance with this policy.

Required Elements of a Natural Events Action Plan In addition to documenting the validity of an exceedance as a natural event, the EPA natural events policy requires a natural events plan include commitments to: 1. Establish public notification and education programs. 2. Minimize public exposure to high concentrations of PM-10 due to future natural

events. 3. Abate or minimize appropriate contributing controllable sources of PM-10. 4. Identify, study and implement practical mitigating measures as necessary. 5. Periodically reevaluate: (a) the conditions causing violations of a PM-10 NAAQS

in the area, (b) the status of implementation of the NEAP, and (c) the adequacy of the actions being implemented.

This plan will document the validity of the March 18, 2001 exceedance as a natural event and address the five required elements listed above.

Documentation of March 18, 2001 Exceedance as a Natural Event The 24-hour average PM-10 concentration measured on March 18, 2001 at the Muldoon station (AIRS Code 02-020-043) in east Anchorage was 180 μg/m3, exceeding the national ambient air quality standard for PM-10. The Tudor monitoring station was also in operation on that day. It recorded elevated PM-10 concentrations

but did not exceed the NAAQS.xxi The locations of the Muldoon and Tudor sites are shown in Figure 1. Figure 1. Location of Muldoon and Tudor PM-10 Monitoring Stations

xxi The 24-hour PM-10 concentration measured at the Tudor Road site (AIRS 02-020-0044) on March 18, 2001 was 150 μg/m3. The EPA considers a value of 155 μg/m3 or higher an exceedance.

Local Climatological Data from Point Campbell in West Anchorage indicate that strong, northerly winds began late on March 17 and persisted through March 18 and most of the day of March 19. The 24-hour average windspeed recorded at Point Campbell was 16 mph (miles per hour) with a peak gust of 33 mph. Weather observations also note blowing dust on March 18 and 19. Data from other stations to the east of Point Campbell suggest that winds were stronger on the eastside of town. In a report prepared specifically for this event, the National Weather Service noted sustained winds ranging from 30 to 35 mph and peak gusts ranging from 40 to 60 mph. The winds recorded on March 18, 2001 meet the definition of a high wind event as defined in EPA’s July 1986 exceptional events guidance.2 This guidance defines a wind-caused exceptional event as one with “an hourly wind speed of greater than or equal to 30 mph or gusts equal to or greater than 40 mph…” Hourly beta attenuation monitor data available from the Tudor site indicate that elevated PM-10 was directly associated with this wind event. Figure 2 shows that the PM-10 concentration increased dramatically at approximately 11 AM, March 18 and remained elevated into March 19. Although BAM data are not available from the Muldoon site, the pattern there is assumed to have been similar. Figure 2. Hourly PM-10 Concentrations at the Tudor Station March 17, 18, and 19, 2001

It should also be noted that the exceedance measured on March 18, 2001 was the first ever recorded in seven years of monitoring at the Muldoon station. The highest value previously measured at the Muldoon site was 125 μg/m3. This value was measured on March 17, 1997 and it was also associated with high winds.

Additional documentation supporting the March 18, 2001 exceedance as a natural event is included in Appendix A.

Public Notification and Education Program The Anchorage Municipal Code (AMC 15.30.060) and the Alaska State Implementation Plan require that the director of the DHHS declare an air pollution episode when 24-hour average PM-10 concentrations reach or are predicted to reach 150 μg/m3. The director is also required to publish an air pollution episode plan that describes the curtailment actions, communication and public notification procedures employed during episodes. A copy of stadnard operating procedures employed by DHHS along with the episode plan, published in 1993, is included in Appendix B. These procedures will continue to be followed when air pollution episodes occur. No distinction is made between natural events and “man-caused” episodes. The public notification procedures outlined in the episode plan were followed during the windblown dust event of March 18, 2001. Even though this event occurred on a Sunday, when municipal personnel were not at work, an air quality advisory was declared and local media were notified. The advisory was declared at approximately 2 PM in the afternoon after staff reviewed BAM data and determined that an exceedance of the 24-hour PM-10 NAAQS was possible if windy conditions persisted.xxii At the time the advisory was declared, the most recent 24-hour average PM-10 concentration had not yet exceeded the NAAQS. In accordance with existing standard procedure, staff consulted with the DHHS medical officer prior to issuing the advisory. DHHS immediately reported the advisory to local television and print media and updated the telephone message line to report the air quality index and information regarding the health advisory.xxiii The Sunday evening newscast and Monday morning newspaper contained information regarding the air quality advisory. A copy of the newspaper article from the March 19, 2001 Anchorage Daily News is included in Appendix C.

xxii In addition to conducting PM-10 sampling with reference method samplers, the DHHS operates two Graseby-Anderson beta attenuation monitors (BAMs) to collect

hourly PM-10 information. These are operated in order to obtain timely information on PM-10 concentrations not available from reference method samplers. DHHS utilizes

the information from the BAMs to report timely air quality index information to the public and to assess whether a health advisory should be declared during a PM-10

episode. The usefulness of the BAMs has been proven in past experience with volcanic eruptions, forest fires, and other wind blown dust events. xxiii DHHS maintains a telephone message line to report the air quality index and other pertinent air quality information. The telephone number for the air quality index

(AQI) report is advertised in the municipal section of the local Anchorage phone directory under “frequently called numbers.” Information is updated at least once daily on

normal workdays and, if conditions warrant, it is updated on weekends and holidays. The phone line is utilized by the general public and the news media for updates on air

quality. It has been in use for over 15 years and is routinely used to issue air quality health advisories.

Minimizing Public Exposure to Elevated PM-10 Concentrations during Natural Events The EPA natural events policy states that a natural events action plan should (a) identify the people most at risk, (b) notify the at-risk population that a natural event is imminent or currently taking place, (c) suggest actions to be taken by the public to minimize their exposure to high concentrations of PM-10, and (d) suggest precautions to take if exposure cannot be avoided. Local epidemiological studies have been conducted by the DHHS in collaboration with other researchers that help identify the people most at risk from PM-10 exposure.3,4 This research suggests that elevated PM-10 concentrations are associated with an increased incidence of bronchitis, upper respiratory illness, and in one study, asthma. This is generally consistent with information contained in the EPA criteria document for particulate matter.5 It is also consistent with the Air Quality Index guideline for reporting air quality that identifies people with respiratory disease among those at most risk.6 Health advisories issued by DHHS in response to PM-10 events advise those with respiratory diseases such as asthma and emphysema to avoid areas where PM-10 levels are likely to be the highest. Those with severe lung disease are advised to remain indoors if possible. In some events, DHHS is able to identify the particular areas that are likely to have the highest PM-10 levels. Monitoring data have shown that areas near major roadways often have the highest PM-10 concentrations during most PM-10 episodes. If information regarding the areas likely to have the highest concentrations is available, it is contained in the health advisory. A sample health advisory is included in Appendix D. As stated earlier, the DHHS medical officer is consulted prior to the issuance of a health advisory. The specific language included in the advisory is dependent on the nature of the event.

Abatement or Minimization of Contributing Controllable Sources of PM-10 In order for an exceedance to be flagged as a high wind-caused natural event, the EPA natural events policy requires that (1) the dust originated from nonanthropogenic sources, or (2) the dust originated from anthropogenic sources controlled with best available control measures (BACM). Based on observations made during this event and other similar high wind events in Anchorage, some portion of the PM-10 is assumed to be anthropogenic or “man-caused.” PM-10 concentrations in Anchorage typically peak in the late March and early April.7 Relatively warm daytime temperatures melt ice and snow from roadsides and gutters. As melting occurs, large amounts of dirt and silt from five or six months of winter road sanding and roadway abrasion become exposed along roadway margins. This material, previously locked under ice and snow now becomes available for re-entrainment into the air by passing vehicle traffic or by high winds. This process is illustrated in the two photographs below, taken six days apart on March 16th and March 22nd of 2000.

Figure 3(a). Minnesota Drive, March 16, 2000. Ice covers most of roadway margin.

Figure 3(b). Minnesota Drive, March 22, 2000. Receding ice reveals accumulated silt along roadway margin.

The photographs show conditions typical for the late winter. (These photos were taken about the same time of the year as the Muldoon PM-10 exceedance but one-year earlier.) Unless there has been a recent snowfall, the majority of the road surface is bare pavement with margins covered in ice. While the traveled portion of the road is relatively clean, large quantities of sand and silt can be found along roadway margins. This material becomes available for re-entrainment as the ice recedes and the exposed silt and dirt dry out. A number of source apportionment studies have been conducted in Anchorage in an effort to distinguish natural sources like windblown glacial silt and volcanic ash from anthropogenic sources like applied winter traction sand and roadway aggregate.8, 9,10 Because the natural and anthropogenic sources of PM-10 are chemically and morphologically similar, these studies have not been very successful in quantifying their relative contribution in past exceedances. For this reason, filter analysis was not performed for the March 18, 2001 event. Nevertheless, given the amount of road silt available for re-entrainment prior to the exceedance, it seems likely that this anthropogenic source was contributory to the exceedance.xxiv As such, the natural events policy states that this source must be controlled by BACM. The EPA has not defined BACM for this source, however. In this case, because BACM is undefined, the natural events policy requires that “practical mitigating measures” be identified, studied and implemented. The next section of this plan discusses the identification, study and implementation of measures designed to control PM-10 emissions from accumulated silt along major roadways in Anchorage.

Identification, Study and Implementation of Practical Mitigating Measures The time sequence of the two photographs in Figure 3(a) and (b) illustrates the difficulty Anchorage faces in developing effective and economical strategies to control PM-10 during the late-winter and early spring “break-up” period. These two figures show that large amounts of roadway silt, previously covered by ice and snow, can be made available for re-entrainment into the air as PM-10 in a matter of a few days through daily melting. Under high winds and/or very dry, low humidity conditions, re-entrainment of this material can result in exceedances of the PM-10 standard. The challenge is to develop strategies that can remove or stabilize this material promptly after it is exposed so that it cannot be re-entrained. As noted in the previous section, Anchorage experiences its highest PM-10 concentrations during this three or four-week break-up period, typically occurring in late-March and early-April. Although high winds sometimes contribute to the elevated PM-10 concentrations during this break-up period, high PM-10 is more commonly associated with calm and dry conditions when fast moving vehicular traffic along major roadways stirs up accumulated silt on roadway margins. In late 1995 the Municipality of Anchorage, the Alaska Department of Environmental Conservation and Department of Transportation and Public Facilities (ADOT&PF) entered into a Memorandum of Understanding (MOU) to cooperatively address the xxiv Other potential anthropogenic sources like wind blown dust from unvegetated vacant lots and gravel pits were excluded as significant contributors because they were covered in snow during the exceedance. According to observations at the NWS Station at Point Campbell, two inches of snow were on the ground during the exceedance.

PM-10 problem in Anchorage.11 Prior to the MOU, Anchorage had experienced a number of exceedances of the PM-10 NAAQS. In the MOU the municipality agreed to evaluate potential PM-10 control measures. Over the past six years, DHHS has worked with municipal and state street maintenance and private consultants in an effort to identify and study appropriate control measures. Although this effort has focused on controlling PM-10 generated by vehicular traffic, study results are likely applicable in high wind events like that of March 18, 2002. Over the past six years, efforts have focused on the evaluation of three potential PM-10 control strategies. These three strategies are:

1. Street sweeping; 2. Changes to winter sanding specifications and application methods; 3. Use of chemical deicing compounds as dust palliatives to reduce re-

entrainment of roadway silt material. A brief discussion of each of these strategies follows. Street Sweeping In the “lower-48,” street sweeping is probably the most commonly adopted control strategy for controlling PM-10 emissions from paved roads. Many communities adopt winter-long sweeping programs to prevent the accumulation of the roadway silt as a source of PM-10. Because of its proximity to Cook Inlet, Anchorage experiences relatively mild winter temperatures, similar to many of the colder “snow belt” communities in the lower-48. However, despite similar or colder temperatures, these lower-48 communities, because of their lower latitude, receive ten to fifteen times more solar energy per day than Anchorage. Figure 4. Solar Insolation in Anchorage, Winnipeg and Denver in December

In lower-48 communities, because of the relatively higher intensity of the solar radiation received, wintertime sunny periods result in significant melting. During these melting periods, accumulated silt is washed off the roadway, reducing the overall silt loading. Moreover, the ice and snow along roadway shoulders and margins are largely eliminated, allowing the roadway to be completely swept. Mid-winter melt–off periods are rare in Anchorage. Sunny days result in little or no melting. Ice and snow remain on roadway shoulders and margins making effective sweeping difficult. Large amounts of traction sand and silt accumulate in the ice along the roadway margins throughout the winter until March, when solar intensity is sufficient to generate melting.xxv When this occurs, large amounts of material are made available in a very short time for PM-10 generation. Sub-freezing temperatures make sweeping in winter very difficult.xxvi Most sweeping equipment requires pre-wetting of the road surface to minimize the amount of dust created during the sweeping operation. Moreover, water flushing of the road surface is necessary after sweeping to eliminate residual fines leftover from the sweep. Without flushing, sweeping may actually increase PM-10 emissions in the short term because material located in roadway margins is redistributed to the traveled portion of the road.12 Water flushing in sub-freezing temperatures is inadvisable. Despite obstacles to sweeping created by sub-arctic winter climate, sweeping is performed in the downtown Anchorage central business district (CBD). Winter sweeping in the CBD is viable because of the intensive use of roadway deicers that prevent the buildup of ice and snow in gutters that would otherwise prevent effective sweeping. Moreover, in order to perform sweeping in winter months, municipal road crews wet sweep using potassium acetate brine to prevent freezing. Extending this sweeping program to all roads in Anchorage would be cost prohibitive, however.

In 1997 the ADOT&PF purchased an EnviroWhirl™ sweeper with baghouse technology that allows sweeping without the pre-wetting required with most other sweeping technologies. Although this sweeper has been successfully operated in the middle of winter, its effectiveness as a PM-10 control strategy in Anchorage is limited because most of the accumulated silt on the road cannot be removed by sweeping because it is locked within a thick layer of ice along the roadway margins. The ADOT&PF recently decommissioned the EnviroWhirl because they found it to be inefficient and resulted in high operating costs. Despite the practical limitations alluded to above, the Municipality of Anchorage and the ADOT&PF have begun work on an agreement that would expedite street sweeping on major roadways in the early spring. Early sweeping of major roadways could be effective means of reducing the severity of PM-10 episodes during the peak of the spring break-up in April. If some sweeping of major roadways can be accomplished in February and March through the use of deicing compounds, it may also be possible to reduce the magnitude of PM-10 episodes resulting from late-winter windstorms like the one that occurred on March 18, 2000.

xxv In Anchorage, the amount of solar insolation increases by a factor of 20 between December and March. xxvi In March, the average daily maximum temperature is 33 °F; the minimum is 18 °F.

Changes to Winter Sanding Specifications and Application Methods In response to commitments in the MOU with the EPA, the Municipality of Anchorage and the ADOT&PF made significant changes to winter sanding specifications and application methods. The amount of fines or silt (amount passing 200 sieve) allowed in traction sand dropped from about 5% to 1% or less. Municipal and state street maintenance departments also made changes to reduce the amount of sand applied during the winter. Work crews apply traction sand together with a magnesium chloride brine to help the traction sand melt into the ice or snow pack and reduce its tendency to be thrown off the road by passing traffic. This reduces the need for reapplication and presumably reduces the amount of material accumulated along roadway margins. Supervisors have also discouraged the excessive use of sand by work crews. PM-10 concentrations dropped significantly after these changes were implemented. Whether this was the effect of the sanding specifications or other factors cannot be definitively determined. Nevertheless, the municipality and ADOT&PF are committed to retaining the new, cleaner sanding specifications and will continue with the judicious application of sand. As stated earlier, in the downtown or CBD, the municipality is using potassium acetate deicers in lieu of traction sand throughout the winter. In 1998, DHHS worked with the ADOT&PF to evaluate whether a similar deicing program on state roads would provide a PM-10 reduction benefit. The hope was that by applying deicing compounds instead of sand, spring break-up silt loadings and hence PM-10, would be reduced. However, when ambient PM-10 concentrations near roads where deicing compounds were used were compared to roads where traction sand was applied, no differences were observed. 13 The testing of magnesium chloride was continued to see whether its use instead of traction sand would decrease the accumulation of roadway silt. Curiously, the study indicated that there was no significant difference in silt loadings between roads that received deicing compounds versus roads where traction sand was applied. While the testing did not show a decrease in silt accumulation on deicer treated roads, laboratory evaluation suggested that the silt material left on the deicer treated road was less prone to re-entrainment, presumably due to the palliative effect of applying hygroscopic magnesium chloride on the accumulated silt. Dustiness tests showed that the material along the treated roads was 75% less dusty than the untreated roads.14 These studies suggest that the value of deicing compounds lies more in their dust palliative effect than in reducing the amount of traction sand applied to the road. The next section discusses the DHHS effort to evaluate the use of deicers as dust palliatives to control the emission of dust from accumulated silt on paved roadways. Use of Chemical Deicing Compounds as Dust Palliatives to Reduce PM-10 Emissions on Paved Roads Over the past few years, DHHS has focused efforts on the use of deicing compounds like magnesium chloride and potassium acetate as dust palliatives during PM-10 episodes. Local studies have suggested that it may be possible to chemically stabilize accumulated roadway silt by applying deicing compounds. Magnesium chloride and potassium acetate are both hygroscopic meaning they tend to bind with

moisture. A local study conducted by DHHS in April 1999 suggested that a single application of magnesium chloride brine reduced ambient PM-10 concentrations near the roadway for approximately three days.15 DHHS is continuing its testing of dust palliatives. While initial test results look promising, a number of important questions remain unanswered. The effectiveness of dust palliatives in a high wind event is unknown. DHHS observations suggest that when dust palliatives are applied to dry silt along a paved roadway, the liquid brine penetration is superficial, perhaps just a few millimeters. Significant mechanical disturbance from a high wind may be sufficient to overwhelm the thin stabilized outside layer of the silt pile. Once the surface layer is eroded, the remainder of the material is untreated and prone to re-entrainment. Investigation into the use of hygroscopic chemicals as dust suppressants is ongoing. A section of parking lot with accumulated traction sand has been cordoned off, divided into three sections, and the pavement cleaned between the sections. Magnesium chloride will be applied to one section, potassium acetate to another, and the third will be treated with water as a control. A leaf blower will be used to simulate a high wind/blowing dust event on the dried control section and observers will compare the dust raised there to the sections where the deicing compounds have been applied. This testing has been hampered so far by rain this spring and is expected to be completed by November 10, 2002, when cold dry weather mimics spring conditions. The intent of the test is to determine whether the application of magnesium chloride or potassium acetate on accumulated silt in the gutters and roadway margins will suppress dust from that source until the streets are free of ice and can be effectively swept. Other researchers have questioned the safety of applying deicing compounds to dry pavement. Under low humidity conditions, application can create a slippery condition that could compromise traffic safety.16 Indeed, in the April 1999 test of magnesium chloride, DHHS received reports of a “greasy” condition on the road. A motorcyclist was reported to have had a near miss when attempting a stop at a treated intersection. The slippery conditions may have arisen because of over-application of the magnesium chloride brine. The brine was reportedly applied at three times the recommended rate. It was also applied across the entire roadway rather than just the roadway margins where the silt had accumulated. Whether these potential problems are real and/or can be overcome by special deicer application methods (e.g. applying deicers only to the roadway margins) is yet to be determined. Further investigation is required before the municipality can commit to the use of chemical palliatives as a PM-10 control measure on paved roads.

Periodic Reevaluation of the Natural Events Action Plan The EPA natural events policy requires periodic reevaluation of the conditions causing violations of the PM-10 NAAQS, the implementation status of the NEAP, and the adequacy of the actions being implemented. Upon completion of the control measure evaluation discussed in the preceding section, DHHS in cooperation with ADEC, will update this plan to reflect the results of the evaluation. Subsequently, this plan will be reviewed every five years or as-required to reflect new information and new understanding regarding the nature of the PM-10 problem and the effectiveness of the strategies used for control.

References 1 Memorandum from Mary Nicholls, Assistant Administrator for Air and Radiation, regarding “Areas Affected by PM-10 Natural Events,” May 30, 1996 2 “Guideline on the Identification and Use of Air Quality Data Affected by Exceptional Events,” EPA-450/4-86-007, July 1986 3 Gordian, Ozkaynak, Xue, Morris, Spengler, “Particulate Air Pollution and Respiratory Disease in Anchorage, Alaska,” Environmental Health Perspectives, 104(3), 290 (March 1996) 4 Choudhury, Gordian, Morris, “Associations between Respiratory Illness and PM-10 Air Pollution,” Archives of Environmental Health, 52 (2),113 (March/April 1997) 5 Air Quality Criteria for Particulate Matter, EPA/600/P-95-001, April 1996 6 Guideline for Public Reporting of Daily Air Quality, EPA-454/R-99-009, July 1999 7 “Air Quality in Anchorage – A Summary of Air Monitoring Data and Trends (1980 – 1999),” Air Quality Program, Department of Health and Human Services, Municipality of Anchorage, May 2000 8 L.C. Pritchett, J.A. Cooper, Aerosol Characterization Study of Anchorage, Alaska, Final Report to the Municipality of Anchorage by NEA, Inc., Beaverton, OR, February 7, 1985. 9 J.A. Cooper, L. Valdovinos, J. Sherman, Source Apportionment by Chemical Mass Balance Technique of PM10 in Eagle River and Juneau, Alaska, Final Report to the Alaska Department of Environmental Conservation by NEA, Inc. Beaverton, OR, May 23, 1988 10 E.R. Crutcher, Source of Particles on PM10 Filters, Report #1062-94 to the Anchorage Air Pollution Control Agency by Microlab Northwest, Redmond, WA, October 17, 1994 11 Memorandum of Understanding between the United States Environmental Protection Agency, the Alaska Department of Environmental Conservation, the Alaska Department of Transportation and Public Facilities, and the Municipality of Anchorage, “A Cooperative Approach Toward Reducing PM-10 in Anchorage,” November 1995 12 “Compilation of Air Pollutant Emission Factors,” Section 13.2.1, Paved Roads, United States Environmental Protection Agency, October 1997 13 “Evaluation of Liquid Magnesium Chloride for Paved Roadway Control in Anchorage,” Air Quality Program, Department of Health and Human Services, Municipality of Anchorage, October 1999 14 “Evaluation of Magnesium Chloride Brine for Paved Roadway PM-10 Control in Anchorage, Final Report,” prepared by Midwest Research Institute for the Municipality of Anchorage, February 15, 2001 15 “Evaluation of Liquid Magnesium Chloride for Paved Roadway Control in Anchorage,” Air Quality Program, Department of Health and Human Services, Municipality of Anchorage, October 1999 16 “The Effect of Magnesium Chloride as an Anti-icing Agent on Tire/Road Friction Coefficient,” Timothy S. Leggett, Eric Brewer, March 24, 1999

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