AECOM 978.589.3000 tel 

2 Technology Park Drive 978.589.3100 fax 

Westford, MA 01886-3140 

Memorandum 

To enhance and sustain the world’s built, natural and social environments 

To: Scott Bohning Page 1 

cc: Shirley Rivera, Sara Head 

Subject: Response to EPA Additional Comments on AECOM 1-hour NO2 NAAQS 

Analysis for Palmdale Hybrid Power Project 

From: 

Richard Hamel 

Date: December 14, 2010 

I. Background 

On April 1, 2009, AECOM, on behalf of the City of Palmdale, submitted a Prevention of Significant 

Deterioration (PSD) permit application to EPA Region 9 for the Palmdale Hybrid Power Project 

(PHPP). A conference call between EPA and PHPP representatives was held in March 2010, during 

which supplemental information was requested by EPA on several items, including the PM2.5, 

visibility, BACT and other analyses, as well as the analysis with respect to the 1-hour NO2 National 

Ambient Air Quality Standard (NAAQS) that became effective in April 2010. On July 21, 2010, 

AECOM submitted the "Palmdale Hybrid Power Project (PHPP) - Supplemental Information for the 

Application for PSD Permit" in response to that conference call. 

On August 26, 2010, EPA (Scott Bohning) provided comments via email on the supplemental 

analyses, focusing on the supplemental 1-hour NO2 NAAQS analysis. In response, AECOM provided 

a memo on October 7, 2010 and then discussed these responses with Mr. Bohning on October 25, 

2010. Subsequently, Mr. Bohning participated in a conference call on October 27, 2010 with EPA’s 

Office of Air Quality Planning and Standards (OAQPS) regarding the 1-hour NO2 NAAQS analysis for 

PHPP and other PSD projects under review by EPA. Mr. Bohning then provided additional comments 

via email on October 28, 2010 which incorporated the OAQPS guidance for the various 1-hour NO2

modeling issues, as well as recommendations specific to the PHPP. 

This memo addresses most of EPA’s outstanding comments regarding the PHPP 1-hour NO2

cumulative modeling analysis (provided via Mr. Bohning’s email on October 28, 2010), resolution on 

each is desired before revised modeling can be submitted. For organizational purposes, each EPA 

comment contains Mr. Bohning’s paraphrasing of the OAQPS guidance followed by EPA’s PHPPspecific recommendation (as provided in EPA’s email). The Applicant’s response follows each EPA 

comment. To facilitate EPA’s review, figures and modeling files which support the responses to the 

various comments are attached. 
AECOM 2

II. Responses to October 28, 2010 Comments 

Following are responses to five of EPA’s 6 comments in the October 28th email. The 6th comment is 

related to the application of the hourly time matched NO2 background values. As shown in the 

response to comment #2 (Table 2), there is not a strong seasonal relationship to the background 

concentrations, and the diurnal distribution is strongly tied to the commute/train schedule. Other than 

the commute hours, the background concentrations are the lowest in the Summer, which would be the 

main time of the year that the PHPP will operate, as this is the time with peak power demand. 

However, since the power plant could operate during any month, AECOM investigated other 

approaches but was unable to discern an obvious alternative on which to base a different averaging 

technique that could be easily applied. Use of maximum monthly or seasonal values, which were still 

dominated by the highly traffic influenced monitor concentrations during commute hours, did not 

provide any benefit to this analysis. Therefore, we request further feedback from EPA on what 

approaches would be acceptable and reasonable for this Project. 

Upon further direction and/or resolution of these issues, AECOM will provide a revised modeling 

analysis. 

1. IN-STACK NO2/NOX RATIOS 

EPA Comment: Should not just cite conversation with equipment vendor on ratios; provide 

information and/or data that the ratio conclusion is based on. 

Should not just cite line of a table provided by e.g. a local District; provide documentation of 

data it is based on, argument for similarity of tested source equipment to project being 

modeled. 

Note that the importance of the in-stack ratio varies by situation. For a short stack having 

peak NO2 impact at fence line at night, with limited mixing and low O3, there will be limited NO 

to NO2 conversion beyond what is in the stack, so the in-stack ratio will be crucial, and can 

determine the overall answer; stronger justification needed for a low ratio. For a taller stack 

with good mixing and higher O3, ratio is less important (and conversely, for PVMRM the 

equilibrium ratio will be more important). Applicant should assess where a particular project 

lies between these two extremes, consider how this will affect the argument for the ratio's 

adequacy. 

PALMDALE RECOMMENDATION: Please supply any available documentation, such as stack 

test data, substantiating the in-stack ratios from vendor GE. Given characteristics of the 

source and the conditions under which high impacts occur, as mentioned above, assess how 

this affects the adequacy of the ratio used. 

Applicant Response: In response to EPA’s August 26, 2010 comments, AECOM asked GE to 

provide stack test data or other information regarding GE’s input that the in-stack ratio for GE turbines 

with SCR installed would be expected to be well under 10%. After an initial response that was 

reported in our October 7th memo, GE (Mr. Andrew Dicke) provided a more formal response on 

October 10, 2010 (a few days after our October 7th submittal) which we have provided below: 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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Richard, 

In response to your enquiry regarding the ratio of NO2 to total NOx contained in gas turbine 

exhaust GE provides the following guidance. This guidance is based on a review of available NO2

emission data for 7FA gas turbine firing natural gas fuel. 

GE's recommended guidance is to assume that a 7FA Gas Turbine firing natural gas will emit less 

than 9 ppm total NOx and NO2 will constitute 10 to 15% of the total NOx emissions. 

If an SCR is installed downstream of the gas turbine, the anticipated NO2 emission values will 

constitute a very small ratio of the remaining NOx, GE recommends assuming NO2 is less than 5% 

of total NOx. The NOx ratio is expected to be below this percentage; however, GE recommends 

5% due to measurement capability and variability in stack measurement results. 

If a CO catalyst is installed upstream of the SCR, the results can be influenced by the catalyst 

configuration, however the NO2 ratio is consistent with the 5% value. 

I trust this guidance addresses your requirements. Should you have any further questions or 

comments please do not hesitate to contact me. 

Regards, 

Andy 

Andrew Dicke 

GE Power and Water 

HDGT Environmental Product Marketing Manager 

T 518-385-0761 

D *235-0761 

C 518-698-9807 

In light of EPA’s October 28, 2010 comments, AECOM has attempted to contact Mr. Dicke (via 

several emails and phone messages over the last few weeks) but has so far been unsuccessful in 

obtaining further information from him. 

As noted in the OAQPS discussion, EPA allows that the situation in which the data are applied can 

affect the importance placed on the in-stack ratio. The area where the proposed PHPP will be built is 

classified non-attainment for the 8-hour ozone standard. As such, the ambient background 

concentrations of ozone monitored at the Lancaster Division Street monitor are generally high. In 

situations with a high background concentration of ozone, the in-stack ratio of NOX to NO2 is of limited 

importance because of the large amount of ozone available for post-stack conversion. Therefore, the 

choice of in-stack ratio for the combustion turbines at PHPP is expected to not be a factor in the PHPP 

1-hour NO2 NAAQS modeling demonstration. 

Given that the in-stack ratio is not critical in this situation and since GE indicates the actual ratio with 

an SCR should be well less than 10%, AECOM feels that a ratio of 10% or less is justified in this 

application.

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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2. NO2 AND O3 BACKGROUND MONITORS 

EPA Comment: OK to show NO2 conservativeness based on monitor proximity to roadways, 

and monitor inclusion of some impacts from nearby sources. Should be quantitative where 

possible, e.g. compare monitor and project site on their distances from nearby point sources, 

roadways, amount of vehicle traffic. 

In general, choice of background cannot be determined in isolation; it depends on how it is 

added to model, and on what conditions that background represents. (What background 

sources does it capture under various conditions?) Consider what is upwind of monitor and of 

project. 

Background concentration can vary by direction (and by meteorological condition...) 

Project and monitor similar distance to urban area may add to argument for 

representativeness. 

PALMDALE RECOMMENDATION: The documentation supplied about the 

representativeness/conservativeness of the Lancaster Division Street NO2 monitor is very 

useful, but it should be supplemented with a comparison to the features of the project site, 

such as distance to nearby point sources, roadways and the amount of traffic on them. 

Applicant Response: Our response provides additional detail related to point, line and area sources 

near the PHPP and the monitor. To aid the discussion, wind roses from the Palmdale Regional 

Airport/USAF Plant 42 are provided in Attachment A for the years 2000 – 2006. As can be seen in the 

wind roses, “downwind” will typically reflect sources in the southwest quadrant. 

The primary non-Project point sources contributing to the background at the PHPP site are the 

Lockheed-Martin and Northrop-Grumman facilities located on U.S. Air Force (USAF) Plant 42 property 

adjacent to the PHPP. Emissions from sources at these two facilities were included in the cumulative 

NO2 modeling. Since these sources are located about 4 km from the Lancaster monitoring station, 

they will also contribute to the ambient background, hence when using a background value that is not 

matched to the meteorological conditions will lead to some “double counting”. There are no other 

major point sources of NO2 near (within 6 miles [10 km]) the PHPP (or the monitor) beyond those that 

are explicitly included in the modeling (see response to comment #5). 

The primary line sources in the area, as described in the supplemental 1-hour NO2 submittal of 

October 7th, are the Metrolink rail line, the Sierra Highway, the Antelope Valley Freeway (SR-14), and 

commute related traffic on Division Street. The locations of these line sources with respect to PHPP 

and the monitor are shown in Figure 1. Table 1 shows the distance between these line sources and 

the Project as compared to the monitor. 

The maximum modeled impacts for normal operations, as well as startup / shutdown, occur on the 

eastern fence line of the PHPP. The distance from the line sources to the location of the maximum 

impacts would thus be slightly higher than the “Distance from PHPP” in Table 1 below. As can be 

seen in the table, the monitor is much closer to all of the local line sources of NO2 emissions than the 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
AECOM 5

Project and location of the maximum impacts. More importantly, these sources are generally northsouth roadways and rail line that would be upwind of both the monitor and PHPP (at different points 

along the line) during the meteorological conditions that lead to the maximum impact, so the distance 

is particularly relevant. 

The east-west streets present near PHPP also have significantly less traffic than those near the 

monitor. East Avenue M, an east-west road that defines the northern boundary of the PHPP site, 

experiences traffic volumes of around 18,500 vehicles / day in the vicinity of the Project according to 

the City of Lancaster Traffic Engineering Division1

. Due to the extensive area covered by USAF Plant 

42, there are no east-west streets within 4 km south (upwind) of the PHPP power block that would 

have substantial traffic volumes (the closest is Avenue P/Rancho Vista Blvd.) The traffic volumes of 

the east-west streets near the monitor however are significantly higher: Avenue K experiences traffic 

volumes of approximately 25,000 vehicles / day to the east of the monitor, and over 30,000 vehicles / 

day to the west. Avenue L experiences daily volumes well in excess of 30,000 vehicles / day to the 

southwest of the monitor, directly upwind of the monitor in the predominant wind direction. There are 

also other streets (Avenue K6 and K8) that run east-west near and downwind of the monitor. 

Table 1: Distance from Project Power Block and Lancaster Monitor From Local Sources of NO2

Emission Source Distance From 

Monitor

Distance From 

PHPP

Daily Volume 

(vehicles/day) 

Sierra Highway 110 meters ~2 km 20,000+ 

Southern Pacific Rail 80 meters ~2 km 24 trains / weekday 

6-12 trains on weekends 

Antelope Valley Freeway1 Just over 2 km Just over 4 km ~80,000 at Ave. L exit 

Division Street2 50 meters About 3 km ~18,000 near the monitor 

Avenue K 0.6 km ~4.0 km 30,000 / 25,000 to the 

west / east of monitor 

Avenue L ~1.0 – 1.5 km ~3.5 km 30,000+ west of monitor 

Avenue M ~2.5 – 3.0 km 0.5 km 18,500 in vicinity of PHPP 

1. http://www.laalmanac.com/transport/tr26b.htm#14

2. This portion of Division Street ends at E Avenue L and starts again in Palmdale west of Sierra Highway 

Additionally, the monitor is significantly affected by commute traffic idling at the intersection in front of 

the building where the monitor is cited, as described by Mr. Chris Anderson in the October 7th

submittal. This scenario is borne out in reviewing the distribution of the background data by hour and 

season, as shown in Table 2 below. As seen in the table, the 8 hours with the highest maximum 

recorded background combination occur from 5 am to 9 am, and 5 pm to 8 pm, corresponding closely 

to the daily commute, and the time at which the Metrolink commuter trains begin running from 

Lancaster to Los Angeles each morning (commencing at 3:58 am, then 4 more trains between 5 am 

 

1

 http://www.cityoflancasterca.org/Modules/ShowDocument.aspx?documentid=4370 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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and 7 am)2. Because this congestion does not occur at the Project site, the background values 

recorded during these hours, which constitute 33% of the total background data collected, significantly 

overstate the ambient background concentration at the Project location. 

Because of the much closer proximity of the vehicle and rail traffic sources to the monitor during the 

wind conditions that produced the highest modeled impacts, it can be assumed that the background 

concentrations during these periods are conservative compared to those occurring near the Project 

site during the worst case modeling scenario. 

Table 2: Maximum Ambient Concentration by Hour and Season (ppb) 

Time Winter Spring Summer Fall Overall 

0:00 41 45 27 43 45 

1:00 41 38 24 39 41 

2:00 40 41 24 35 41 

3:00 39 43 42 40 43 

4:00 40 47 49 49 49 

5:00 44 61 65 62 65 

6:00 50 56 61 64 64 

7:00 51 55 49 60 60 

8:00 56 50 34 56 56 

9:00 50 46 24 50 50 

10:00 40 20 18 39 40 

11:00 40 16 10 28 40 

12:00 25 18 18 24 25 

13:00 25 18 13 23 25 

14:00 25 18 13 25 25 

15:00 38 18 15 35 38 

16:00 40 20 14 40 40 

17:00 50 30 15 62 62 

18:00 48 49 17 56 56 

19:00 52 43 24 50 52 

20:00 48 58 33 49 58 

21:00 45 47 30 47 47 

22:00 51 45 40 43 51 

23:001 29 4 ND ND 29 

1. Most of the data from the hour beginning at 23:00 is missing from 

the dataset as the monitor is recalibrated nightly at that time. 

 

2

 http://www.metrolinktrains.com/schedules/pdf.php?id=1041

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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The only potentially significant area source of NO2 emissions closer to the Project site than the 

monitor is air traffic at the Palmdale Regional Airport/USAF Plant 42. The airport is operated by Los 

Angeles World Airports (LAWA), but air traffic at the airport is minimal since no commercial airlines 

currently operate there. In a 1989 agreement with the Air Force, commercial traffic is currently 

allowed up to 50 operations per day, with an operation being either a landing or a takeoff3

. Eight 

airlines have attempted to establish a viable business at Palmdale Regional Airport since 1971, all of 

which have failed. In 2009, including military operations, there were an annual total of 26,905 landing 

or take-off operations, an average of 73.7 operations per day4

. In 2007 and 2008, the average 

operations per day were 92.4 and 80.2. Because the runways are located to the south and southeast 

of the PHPP, these emissions should not impact the receptors showing the maximum modeled 

impacts at the same time as PHPP sources, which occur when the winds are blowing from the west. 

Any long term contributions to the ambient background concentration should be picked up by the 

Lancaster Division Street monitor, less than 4 kilometers away. No other significant sources of NO2

exist upwind of the highest modeled impacts that would contribute significantly to the modeled 

concentrations. 

No other monitors that collect NO2 data in the region were found that could be expected to be a better 

fit than the location selected. The nearest monitor other than the Lancaster Division Street monitor is 

located in Santa Clarita, nearly 50 kilometers from the Project site, and located in a mountain setting 

dissimilar to that of Lancaster / Palmdale. 

Based on the discussion above along with the detailed information about the sources local to the 

monitor given in the 1-hour NO2 cumulative analysis, AECOM believes the Lancaster Division Street 

Monitor conservatively reflects the ambient background in the vicinity of the PHPP because: 

• Close proximity of the monitor to the Project site (4 km) 

• Closer proximity to the monitor of the Antelope Valley Freeway, Sierra Highway, Metrolink 

rail line, and major streets which are located upwind of the monitor and PHPP when the 

highest modeled impacts occur. 

• The fact that the emissions from Lockheed Martin and Northrop Grumman are included in 

the modeling inventory, as well as contribute to the ambient background concentration, 

and are thus double counted in the modeled impacts. 

• Background values for commute hours are likely overstated for the Project location by 30-

50%. 

3. MISSING O3 DATA PROCEDURE 

EPA Comment: Not appropriate to use an annual average to fill in missing hourly ozone 

values: misses high values that can occur during the day. 

Using the higher of the missing interval endpoints is more conservative than interpolation, but 

for longer intervals may miss an ozone peak. Even if it is OK for a particular data set, it's not a 

good general rule to approve. Better to start with an approach guaranteed to be conservative, 

 

3

 http://www.jpbroker.com/pairport.html

4

 http://www.city-data.com/airports/Palmdale-Regional-Usaf-Plant-42-Airport-Palmdale-California.html#PMD

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
AECOM 8

then make special case arguments for problematic hours. (Instead of starting with a usuallyconservative approach and then arguing that it's probably OK.) 

Example approach: for each of the 24 hours of the day, use maximum value that occurs for 

that hour (24 separate default values); or do this for each month (288 separate default values). 

 Requires a bunch of post-processing. 

PALMDALE RECOMMENDATION: It would be preferable to start with a conservative approach, 

such as substitution of a value from the corresponding seasonal or monthly high hour (as 

mentioned in the example). Professional judgment could then be applied to problematic 

hours, using an alternative approach that continues to insure that no underprediction bias is 

introduced. However, the approach proposed during our 10/25 phone call, using interval 

endpoint highs for intervals longer than 3 hours would still be acceptable for this particular 

data set, if it is one part of an overall substitution procedure, and is accompanied by a 

documented assessment of the reasonableness of substitutions of 3 or more consecutive 

daytime hours in comparison with neighboring days.

Applicant Response: AECOM proposes the following ozone filling strategy, which incorporates the 

EPA recommendation above: 

• Where there is 1 or 2 hours missing, the higher of the two endpoints will be persisted across 

the missing hours. 

• Where 3 or more hours are missing, the higher of the following will be persisted across all 

hours in the missing period: 

o The higher of the two endpoints, or; 

o The highest value from any hour in the missing period from the day before or after the 

day where the missing hours occurred. 

4. USE OF 3 YEARS RATHER THAN 5 YEARS OF METEOROLOGICAL DATA 

EPA Comment: As discussed in the "Applicability of Appendix W Modeling Guidance for the 1-

hour NO2 NAAQS", memorandum from Tyler Fox, 2010-06-28, as well as in Guideline on Air 

Quality Models §8.3.1.2, five years of representative meteorological data (or one year of on-site 

data), are required in air quality impact analyses. However, the modeling supplied for NO2 as 

well as for the other pollutants evaluated used only three years of data. While three years of 

data may have been accepted for past applications by other permitting authorities, or even by 

EPA in particular circumstances, we do not believe that is a sufficient rationale for using less 

than the 5 years specified in EPA's regulatory guidance. Additional justification would be 

required for using a shorter data set. 

Applicant Response: The Application for Prevention of Significant Deterioration Permit for the 

Palmdale Hybrid Power Project was submitted on April 1, 2009. Prior to that application, the “Class II 

Area Dispersion Modeling Protocol for the Proposed Palmdale Hybrid Power Project” was submitted 

to EPA on August 6th, 2008. The modeling protocol fully described the process by which the 

meteorological data to be used in the modeling were selected and processed for use in the analysis, 

which includes 3 years of data from 2002-2004. Since that time, a total of 4 modeling analyses, 

between the original modeling and supplemental modeling submitted in response to EPA Region 9 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
AECOM 9

comments, have been presented to EPA region 9, with no comments whatsoever about the use of 3 

years of data for the PSD permitting of this Project. 

EPA Region 9 has had many opportunities to comment on the appropriateness of the meteorological 

data for almost four years and related to two projects5

, one of which was fully approved, and has 

never indicated that there was any issue with regard to the selection of meteorological data for PHPP. 

It was our understanding that these data were acceptable, not only due to the lack of comments to the 

contrary, but because the data used for PHPP can be considered to be “on-site” data, in which case 

only one year is required. 

For the PHPP modeling analysis, the meteorological data chosen was collected at the Palmdale 

Regional Airport, which is located on the property of United States Air Force Plant 42. The relative 

locations of the PHPP power block and the meteorological tower is shown in Figure 2. The tower is 

located less than 2.5 kilometers from the power block and meets the description outlined for “Site 

Specific” as defined in section 8.3.3 of the EPA Guideline on Air Quality Models (GAQM; as 

incorporated in Appendix W of 40 CFR Part 51; EPA, 2005). Both the PHPP stack locations and the 

meteorological tower are very close to the Palmdale Regional Airport runways and are physically 

located in wide open space. The tower is in direct line of sight with the PHPP stacks, and due to its 

location on USAF Plant 42 property, will experience nearly identical meteorological conditions in terms 

of wind speed/direction, temperatures, humidity, pressure, precipitation, etc., at all times. 

As an additional step towards confirming that the met tower should be considered site specific, the 

land use characteristics of both the PHPP power block and the tower were calculated with the 

AERSURFACE pre-processor for AERMOD and compared. The source parameters used for both 

runs were identical to those described in the “Class II Area Dispersion Modeling Protocol for the 

Proposed Palmdale Hybrid Power Project”, except that to make an equivalent comparison between 

the two sites, twelve 30 degree sectors were used for both: 

• Twelve 30 degree land-use sectors 

• Annual results by sector were compared 

• 1 kilometer radius 

• At airport = ‘Y”, Arid location = “Y”, One month of snow cover = “N”. 

• Seasons defined as follows: 

o Jan, Feb: Late autumn after frost and harvest, or winter with no snow. 

o Mar, Apr, Nov, Dec: Autumn with unharvested cropland. 

o May, Jun, Jul, Aug, Sep, Oct: Midsummer with lush vegetation 

 

5 The Application for PSD Permit for the Victorville 2 (VV2) Hybrid Power Project, a virtual clone of PHPP proposed for 

construction in the same region as PHPP (less than 50 miles away), was done in a similar fashion. The Class II 

modeling protocol was submitted to EPA Region 9 on January 17, 2007, followed by the PSD application on May 3rd, 

2007. The modeling analyses for that project also used 3 years of data from 2002-2004 from a nearby met tower. 

Over the course of that project there were numerous submittals to EPA Region 9. On March 11th, 2010, EPA Region 9 

granted the PSD Permit for VV2. At no time during the permitting process did EPA Region 9 ever question the use of 3 

years of meteorological data in the PSD modeling, though at one point the agency did ask for further information on 

how the missing data was filled, so the meteorological data were reviewed by EPA.

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
AECOM 10

The results of the AERSURFACE runs are shown in Table 3. The table shows that the surface 

characteristics of the two locations are virtually identical from every wind direction, with a maximum 

difference in surface roughness of 0.03 m (3 centimeters) and an average difference of less than one 

centimeter. With such small differences, the surface roughness at the tower and the Project site are 

effectively identical. The AERSURFACE modeling files are attached to this memo in zipped format. 

Table 3: Comparison of Surface Roughness at PHPP Stack Locations and Palmdale Regional 

Airport Meteorological Tower (m) 

Sector Airport PHPP Difference

1 0.128 0.133 ‐0.005

2 0.122 0.125 ‐0.003

3 0.131 0.126 0.005

4 0.127 0.123 0.004

5 0.123 0.129 ‐0.006

6 0.121 0.138 ‐0.017

7 0.113 0.144 ‐0.031

8 0.123 0.144 ‐0.021

9 0.137 0.137 0.000

10 0.132 0.139 ‐0.007

11 0.127 0.140 ‐0.013

12 0.120 0.139 ‐0.019

Average 0.125 0.135 ‐0.009

Therefore, because of the close proximity of the tower to the Project, the nearly identical 

characteristics of the tower and Project emissions source locations, and the fact that the tower and 

Project site within direct line of sight of each other, the tower qualifies as site specific per Appendix W. 

Such has been the determination in similar situations, one of which is the Baldwin Power Plant study6

which was used as an evaluation database for AERMOD. In that case, the tower was located off 

property, 2.2 kilometers from the power plant stacks and was still considered “site-specific” for 

purposes of meteorological data requirements. In the case of PHPP and the Palmdale Regional 

Airport, the land-use at the tower and that at the Project site are, in fact, much more similar than was 

the case in the Baldwin Power Plant study. 

The reason that the years 2002 – 2004 were selected is that there was too much missing upper air 

data (collected at Mercury, NV) in the later years. If 5 years of data were to be required, the dataset 

would need to be 2000 – 2004. Wind roses for the selected three year period, as well as the two years 

before and the two years after, are provided in Attachment A. Review of these wind roses shows that 

there is very little year to year variation at this site. Therefore, a requirement to redo all of the 

modeling (not just the 1-hour NO2 NAAQS analysis) and other analyses for PHPP would be 

 

6

 http://www.epa.gov/ttn/scram/7thconf/aermod/baldwin.zip

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
AECOM 11

burdensome and unjustified at this stage given that the conclusions from the modeling results are 

unlikely to change. 

Because the meteorological data from Palmdale Regional Airport meets the criteria to be considered 

site specific data, only one year of meteorological data is required for this analysis, in which case the 

use of three years of data meets and exceeds the meteorological data requirements for this modeling 

analysis. 

5. CRITERIA FOR CUMULATIVE SOURCE INVENTORY SELECTION

EPA Comment: The October 7th AECOM memo cites Chris Anderson of the Antelope Valley 

Air Quality Management District (AVAQMD) as the source of information about nearby sources 

to use in a cumulative modeling assessment. However, there should be documentation of the 

selection criteria were used, and whether they meet the requirements in the Guideline on Air 

Quality Models §8.2.3 on background concentrations in multi-source areas. 

Applicant Response: Mr. Chris Anderson, Air Quality Engineer, and Mr. Alan De Salvio, Supervisor 

of Air Quality Engineering, of AVAQMD provided the following response to our request for the criteria 

used for cumulative source inventory selection: 

Selection Criteria for Nearby Sources 

The AVAQMD selected, based upon conformance with the Guideline on Air Quality 

Models, Lockheed Martin Corporation-Palmdale and Northrop Grumman CorporationPalmdale to be included as “nearby sources”. Both are major sources of ozone precursors 

and are in very close proximity to the site. One would expect that based on these criteria 

both these facilities could be expected to cause a significant concentration gradient in the 

vicinity (6 mile radius) of the PHPP. Minor facilities located within the 6 mile radius are 

expected to be included in the background monitored at the AVAQMD air monitoring 

station which is located in close proximity (approximately within 2 miles) of the PHPP 

site. 

Please feel free to call Rich Hamel at 978-589-3275 or Sara Head at 805-388-3775 if you have any 

questions or comments regarding this information. 

 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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Figure 1: Relative Location of the PHPP Power Block, Lancaster Monitor, and 

Significant Background Sources 

Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 
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Response to EPA Comments on AECOM 1-hour NO2 NAAQS Analysis for PHPP 

13

Figure 2: Relative Location of the PHPP Stacks and Meteorological Tower 
Attachment A: 

2000-2006 Wind Roses for Palmdale Regional Airport,

Palmdale, California 
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 3-year 2002-2004 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 10.31%

TOTAL COUNT:

25924 hrs.

CALM WINDS:

10.31%

DATA PERIOD:

2004 2002 2003 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.24 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 5 year (2000-2004) Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 10.78%

TOTAL COUNT:

41611 hrs.

CALM WINDS:

10.78%

DATA PERIOD:

2001 2000 2002 2003 2004 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.37 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 7 year (2000-2006) Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 12.45%

TOTAL COUNT:

58530 hrs.

CALM WINDS:

12.45%

DATA PERIOD:

2001 2005 2006 2000 2002 

2003 2004 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.26 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2000 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

12/13/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 13.11%

TOTAL COUNT:

8192 hrs.

CALM WINDS:

13.11%

DATA PERIOD:

2000 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.61 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2001 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

12/13/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 9.86%

TOTAL COUNT:

7495 hrs.

CALM WINDS:

9.86%

DATA PERIOD:

2001 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.54 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2002 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

12/13/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 8.57%

TOTAL COUNT:

8628 hrs.

CALM WINDS:

8.57%

DATA PERIOD:

2002 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.56 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2003 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 12.24%

TOTAL COUNT:

8643 hrs.

CALM WINDS:

12.24%

DATA PERIOD:

2003 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

7.90 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2004 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 10.12%

TOTAL COUNT:

8653 hrs.

CALM WINDS:

10.12%

DATA PERIOD:

2004 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.26 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2005 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 17.07%

TOTAL COUNT:

8545 hrs.

CALM WINDS:

17.07%

DATA PERIOD:

2005 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

7.64 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)
WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Palmdale Regional Airport 2006 Wind Rose

Palmdale, CA

COMMENTS: COMPANY NAME:

MODELER:

DATE:

11/17/2010

PROJECT NO.:

NORTH

SOUTH

WEST EAST

4%

8%

12%

16%

20%

WIND SPEED 

(Knots)

 >= 22

 17 - 21

 11 - 17

 7 - 11

 4 - 7

 1 - 4

Calms: 16.03%

TOTAL COUNT:

8374 hrs.

CALM WINDS:

16.03%

DATA PERIOD:

2006 

Jan 1 - Dec 31

00:00 - 23:00

AVG. WIND SPEED:

8.34 Knots

DISPLAY:

 Wind Speed

Direction (blowing from)