August 15, 2013

Mr. Gerardo Rios

Chief, Permits Office

U.S. EPA Region 9

75 Hawthorne Street

San Francisco, CA 94105

Subject: Pio Pico Energy Center PSD Permit Application, PM BACT Determination

Dear Mr. Rios:

On August 2, 2013, EPA’s Environmental Appeals Board (EAB) completed its review of 

petitions concerning the Pio Pico Energy Center (PPEC) PSD permit application. In its 

response to the petitions, the EAB affirmed virtually all of Region 9’s decisions and 

analyses in support of the permit, but issued a narrow remand to Region 9 to “prepare a 

revised PM BACT analysis and reopen the public comment period to provide the public 

with an opportunity to comment on it.” 

Specifically, in its instructions to Region 9, the EAB sought additional documentation 

regarding the PM BACT determination:

The record does not reflect the Region’s considered judgment in 

selecting the BACT emission limits for PM. The Region, in conducting 

its PM BACT analysis, failed to adequately consider significant 

information in the record regarding two simple-cycle plants [Panoche 

Energy Center and CPV Sentinel] that use the same turbine model as 

proposed for the Facility. Neither the “Fact Sheet and the Ambient Air 

Quality Impact Report” nor the response to comments document 

analyzed this information in detail nor explain how it affects the 

Region’s PM BACT determination. In addition, the Region’s 

explanation for its selection of 80 percent load as the defining criterion 

for applying two different emission limits and the selection of 5.5 pounds 

per hour (‘lb/hr’) as BACT for loads under 80 percent are not 

adequately explained in the record.

sierra

research

1801 J Street

Sacramento, A 95811

Tel: (916) 444-6666

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Tel: (734) 761-6666

Fax: (734) 761-6755
Gerardo Rios -2- August 15, 2013

The “significant information” referred to by the EAB regarding Panoche is the test data 

provided by the Applicant in its January 5, 2012 letter.1 The Panoche data were provided 

by the Applicant, at EPA’s request, because it was a major factor in Applicant’s 

determination that it could meet a permit limit of 5.5 lb PM/hour at all times over the 

lifetime of the project, even though the vendor would not guarantee that level of 

emissions.

There is already information in the record to satisfy the EAB’s instructions on remand 

promptly and without delay. Specifically, the EAB’s directive to address the 

relevance of the Panoche data to the BACT analysis can be satisfied by considering 

information provided by the Applicant, which is already in the record, in EPA’s 

analysis.

The Panoche Energy Center source test data are summarized in Table 3. 

Please note that these few source tests are not sufficient to demonstrate that 

the measured emission rates are achievable under all conditions and for the 

lifetime of the turbines. Furthermore, the test method used to measure PM is 

not very accurate at the low levels being measured; there is considerable 

variability in the results. For these reasons, the applicant has proposed a 

compliance level that takes into account (a) the vendor guarantee; (b) the 

emission levels demonstrated in the source tests; (c) reasonable variability in 

performance that can be expected over the lifetime of a well-maintained unit; 

and (d) the variability inherent in the source test methodology.

Taking all of the above into account, test results provide sufficient support for 

the Applicant to determine that it can comply with a 5.5 lb/hr emission limit, 

which is equivalent to 0.0065 lb/MMBtu measured at or near peak turbine 

load.2

The “significant information” referred to by the EAB regarding CPV Sentinel is that it 

was alleged to have a vendor guarantee of 5 lb/hr.3

 The EAB explained that “[t]he 

existence of a similar facility with a lower emissions limit creates an obligation for the 

permit applicant and permit issuer to consider and document whether the same emission 

level can be achieved at the proposed facility”4 [emphasis in original].

EPA, in its response to this comment, explained that the vendor guarantee was 5 lb/hour, 

and an emission limit of 5 lb/hr is the same value as a permit limit of 5.5 lb/hr, due to 

1 Letter from Steve Hill to Gerardo Rios, Pio Pico Energy Center PSD Permit Application, Modeling 

Questions (January 5, 2012), p. 12-13 2 Letter from Steve Hill to Gerardo Rios, Pio Pico Energy Center PSD Permit Application, Modeling 

Questions (January 5, 2012), p. 12 3 Email from Johannes Epke to Roger Kohn (July 24, 2012), p. 6: “For the CPV sentinel Project which 

utilizes the LM‐100 turbine GE has provided vendor guarantees that LM‐100 can achieve a 5 pound per 

hour limit. GE revised the PM10 emissions from the CTG to 5 lb/hr instead of 6 lb/hr, see guarantee e‐mail 

dated 10/21/09.5 The 5 pound per hour limit represents BACT for the LM‐100 for PM‐10 emissions.” 4 In Re Pio Pico Energy Center, PSD Appeal Nos. 12-04 through 12-06, Order Remanding in Part and 

Denying Review In Part (August 2, 2013), (“Pio Pico Slip Op.”) p. 96

 
Gerardo Rios -3- August 15, 2013

conventions for rounding.5 EPA thus directly confronted and disposed of the claim that 

Sentinel has a lower emissions limit than that proposed for PPEC. Sentinel’s actual PM 

emission limit (11 lb PM/hour) was not a part of the record.6

Despite this record, the EAB found that “none of the documents that form the basis of the 

Region’s BACT analysis discuss [the Panoche emission data] or explain why this 

information is not part of the BACT analysis.”7

 Similarly, the EAB found that EPA did 

not investigate the CPV Sentinel emission data or explain why such investigation was not 

necessary for the BACT determination. As explained here, there already is sufficient 

information in the record for EPA to promptly respond to the EAB’s direction and make 

any appropriate amendments to its analysis in a prompt and timely fashion.

New Test Information Is Now Available

Compliance source tests have recently been performed on LMS-100 turbines at CPV 

Sentinel and Walnut Creek Energy Park. Source test reports for these facilities were 

previously submitted to EPA by the facility owners; copies are included on the CD 

accompanying this letter. The Panoche data and source tests were previously provided to 

EPA.8

 The data are summarized and discussed below. 

CPV Sentinel – Compliance source tests were conducted in January and February of 

2013. PM2.5 measurements are shown in Table 1. There are eight identical LMS-100 

turbines at CPV Sentinel. Tests were performed at three load levels (nominally 100%, 

75%, and 50%). 

Walnut Creek Energy Park – Test results from Walnut Creek are summarized in Table 2. 

There are five identical LMS-100 turbines at Walnut Creek. Tests were performed at one 

load level (nominally 100%). 

Panoche – Test results from Panoche are summarized in Table 3. There are four identical 

LMS-100 turbines at Panoche. Tests were performed at one load level (nominally 

100%).

5 EPA, Responses to Public Comments on the Proposed Prevention of Significant Deterioration Permit for 

the Pio Pico Energy Center (November 2012), p. 51. 6 EPA incorrectly characterized the 5 lb/hr emission rate as an “emission limit” for CPV Sentinel. In fact, 

the only PM mass emission limit for CPV Sentinel is 11 lb/hr (SCAQMD Facility Permit 152707, 

Section H). 7 Pio Pico Slip Op., p. 94 8 Letter from Steve Hill to Gerardo Rios, Pio Pico Energy Center PSD Permit Application, Modeling 

Questions (January 5, 2012)

 
Gerardo Rios -4- August 15, 2013

Table 1

PM2.5 Emission Tests Results

Walnut Creek Energy Park Units 1-5

5 x 100 MW GE Model LMS100 combustion turbines

Date Unit Run #

Unit Load, 

% of 

capacity

Fuel 

Flow, 

hscfm

Mass 

Emission, 

lb/hr

Emission 

rate, 

lb/MMscf

Emission 

rate, 

lb/MMBtu

1/19/2013 1 W-1/STK-2.5-100-1 99.6% 8,039 1.86 2.32 0.0023

1/20/2013 1 W-1/STK-2.5-100-2 99.6% 8,039 1.07 1.34 0.0013

1/21/2013 1 W-1/STK-2.5-100-3 100.0% 8,073 1.47 1.8 0.0017

1/29/2013 2 W-2/STK-2.5-100-1 98.8% 7,975 0.369 0.463 0.0004

1/30/2013 2 W-2/STK-2.5-100-2 98.3% 7,935 0.576 0.726 0.0007

1/30/2013 2 W-2/STK-2.5-100-3 97.3% 7,858 1.162 1.478 0.0014

2/21/2013 3 W-3/STK-2.5-100-2 98.8% 7,975 1.2 1.51 0.0015

2/23/2013 3 W-3/STK-2.5-100-5 99.9% 8,062 1.1 1.36 0.0013

2/24/2013 3 W-3/STK-2.5-100-6 97.8% 7,892 0.73 0.92 0.0009

2/27/2013 4 W-4/STK-2.5-100-1 95.7% 7,724 0.68 0.88 0.0009

2/28/2013 4 W-4/STK-2.5-100-2 96.6% 7,798 0.86 1.1 0.0011

2/28/2013 4 W-4/STK-2.5-100-3 96.3% 7,774 0.75 0.96 0.0009

3/25/2013 5 W-5/STK-2.5-100-1 90.4% 7,295 1.81 2.48 0.0024

3/27/2013 5 W-5/STK-2.5-100-2 90.1% 7,276 1.71 2.35 0.0023

3/27/2013 5 W-5/STK-2.5-100-3 90.4% 7,300 2.11 2.88 0.0028
Gerardo Rios -5- August 15, 2013

Table 2

PM Emission Tests Results

CPV Sentinel Units 1-8

8 x 100 MW GE Model LMS100 combustion turbines

Date Unit Run #

Unit Load, % 

of capacity

Fuel 

Flow, 

hscfm

Mass 

Emission, 

lb/hr

Emission rate, 

lb/MMscf

Emission rate, 

lb/MMBtu

2/2/2013 3 1-PM-100 97.4% 8,901 4.99 5.61 0.0054

2/13/2013 3 2-PM-100 100.0% 9,138 0.71 0.77 0.0007

2/4/2013 3 S-3STK-PM-75-1 77.0% 7,038 0.64 0.91 0.0009

2/4/2013 3 S-3STK-PM-50-1 58.0% 5,298 0.59 1.12 0.0011

1/15/2013 1 1-PM-100 94.2% 8,609 0.91 1.06 0.0010

1/15/2013 1 2-PM-100 98.2% 8,977 0.81 0.91 0.0009

1/17/2013 1 6/PM-75 76.9% 7,026 0.78 1.11 0.0011

1/17/2013 1 7-PM-75 77.0% 7,032 0.28 0.4 0.0004

1/16/2013 1 3-PM-50 58.6% 5,354 0.81 1.51 0.0015

1/16/2013 1 4-PM-50 58.4% 5,339 0.72 1.34 0.0013

2/11/2013 4 S-4/STK-PM-100-1 96.8% 8,845 4.38 4.96 0.0048

2/11/2013 4 S-4/STK-PM-75-1 76.3% 6,974 1.12 1.6 0.0016

2/12/2013 4 S-4/STK-PM-50-1 58.6% 5,354 1.42 2.65 0.0026

3/23/2013 7 S-7/STK-PM-100-1 91.8% 8,390 0.76 0.9 0.0009

3/24/2013 7 S-7/STK-PM-75-1 76.3% 6,972 0.75 1.07 0.0010

3/24/2013 7 S-7/STK-PM-50-1 58.9% 5,381 0.71 1.32 0.0013

1/30/2013 2 S-2/STK-PM-100-1 92.6% 8,459 1.02 1.21 0.0012

1/30/2013 2 S-2/STK-PM-100-2 90.2% 8,239 0.54 0.66 0.0006

1/31/2013 2 S-2/STK-PM-100-3 90.4% 8,260 0.67 0.82 0.0008

2/1/2013 2 S-2/STK-PM-75-1 75.8% 6,923 0.49 0.71 0.0007

2/1/2013 2 S-2/STK-PM-50-1 58.8% 5,373 0.42 0.78 0.0008

2/27/2013 6 S-6/STK-PM-100-1 95.9% 8,764 1.87 2.14 0.0021

2/27/2013 6 S-6/STK-PM-75-1 76.2% 6,960 1.02 1.47 0.0014

2/28/2013 6 S-6/STK-PM-50-1 59.4% 5,431 1.03 1.89 0.0018

2/25/2013 5 S-6/STK-PM-100-1 95.7% 8,747 0.85 0.97 0.0009

2/25/2013 5 S-6/STK-PM-75-1 77.3% 7,063 0.84 1.19 0.0012

2/26/2013 5 S-6/STK-PM-50-1 59.0% 5,392 1.02 1.9 0.0018

4/5/2013 8 S-8/STK-PM-100-1 99.8% 9,122 2.37 2.6 0.0025

2/25/2013 8 S-8/STK-PM-75-1 76.0% 6,946 0.9 1.3 0.0013

2/26/2013 8 S-8/STK-PM-50-1 58.2% 5,316 1.02 1.91 0.0019
Gerardo Rios -6- August 15, 2013

Table 3. PM Emission Tests Results, lb/MMBtu

Panoche Energy Center

4 x 100 MW GE Model LMS100 combustion turbines

Date 5/13/2011 5/12/2011 5/11/2011 5/10/2011 5/11/2010 5/12/2010 5/18/2010 5/19/2010

4/30/09 -

5/1/09 4/27/2009 4/23/2009 4/24/2009

Unit 1 2 3 4 1 2 3 4 1 2 3 4

Unit Load 100% 100% 100% 100%

Run 1 0.00298 0.00402 0.00314 0.00184 0.00279 0.00141 0.00168 0.00249 0.002 0.005 0.012 0.002

Run 2 0.00261 0.00192 0.00420 0.00182 0.00213 0.00107 0.00176 0.00198 0.002 0.003 0.002 0.007

Run 3 0.00167 0.00169 0.00605 0.00185 0.00169 0.00155 0.00149 0.00310 0.004 0.001 0.002 0.006

Average 0.00242 0.00254 0.00446 0.00184 0.00220 0.00134 0.00164 0.00252 0.003 0.003 0.005 0.005

Lb/hr 2.388 2.649 4.557 1.834 2.24 1.375 1.724 2.559 2.53 2.69 4.98 4.63
Gerardo Rios -7- August 15, 2013

Discussion

These data demonstrate the extreme variability (and hence uncertainty) in measuring 

PM emissions from gas fired turbines. These are 17 LMS100 gas turbines, tested 

under very similar conditions. Some of the variability could be due to individual 

differences between ostensibly identical units; however, replicate tests on the same 

unit at the same conditions result in measurements that differ by as much as a factor 

of seven.9

The BACT limit for PPEC must take this measurement uncertainty into account. If 

the design and performance of these units are to form the basis of a BACT 

determination for PPEC, the emission limit proposed must be set at a level with 

which these units, and these measurements, would be in compliance. Furthermore, the 

fact that these test results are for new units must be taken into account. The 

compliance limit must be set at a level for which continuous compliance can 

reasonably be assured based on the test methods required to demonstrate compliance.

Table 4 shows some of the key statistics for the combined test data.

Table 4

Statistics for Combined PM Source Test Data

Combined (run avgs)

lb/hr Overall

Maximum 4.98

Average 1.74395

Std Deviation 1.22441

Relative Std 

Deviation 70%

Mean plus 2 S.D 4.1928

lb/MMBtu Overall

Maximum 0.00533

Average 0.00204

Std Deviation 0.00119

Relative Std 

Deviation 59%

Mean plus 2 S.D 0.0044

Sample size: 38

Table 4 shows that the mean PM measurement was 1.74 lb/hr, with a standard 

deviation of 1.22 lb/hr. The value of the mean plus 2 standard deviations is 

4.19 lb/hr. If the distribution of measurement values is normal, 98% of all 

measurements would be expected to be below this level. Reliance on two standard 

deviations is necessary to ensure that these units can meet the BACT emission 

9 See test results for Sentinel Unit 3, Table 2, 100% load.

 
Gerardo Rios -8- August 15,2013 

limitation at all times. To account for the fact that these data are for new units, which 

will inevitably suffer diminished performance over time, it is necessary to apply an 

additional 20% margin so that the BACT emission limitation can be met over the 

units' entire useful lifetime .. Such a safety factor is necessary because no data exist 

for LMS-l 00 units nearing the end of their useful life. 10 If a 20% margin is applied to 

this value (to account for the fact that these data are for new units, whereas the 

facility must comply with a BACT list over its lifetime, and no data exist for 

LMSlOOs nearing the end oftheir useful life), the resulting value is 5.0 lblhr. 

Applying the same logic to the Ibs/MMbtu values, a value of 0.0053 IbslMMbtu 

would be calculated. 

Table 4 shows that the highest measured PM emission rate was just under 5.0 lblhr. 

This was not an isolated result: there were two other high measurements (4.56 and 

4.38 Iblhr). As discussed above, any proposed BACT emission limit based on these 

data must allow all of the measurements to be complying values. 

For the reasons presented above, the lowest emission limit that can be derived from 

available source test data, with margins to ensure that compliance can be maintained 

for the life of the facility based on required test methods is, 5.0 lb PMIhr. This 

emission limit would be lower than the emission limit for Sentinel (11 lblhr) , Walnut 

Creek (11 lblhr) , or Panoche (6.00 lblhr). 

PPEC is willing to accept a permit limit of 5.0 lblhr and 0.0053 IblMW-hrnet, 

applicable at all times, under all allowable operating loads, to be enforced based on 

the test methods specified in the proposed PSD permit at Condition IX.G.1.c. 

Sincerely, 

Gmy~ .. ~ . 

End (CD) 

ccw/o end: 

David Jenkins, Apex Power Group 

Jim Wedeking, Sidley Austin 

10 The EAB has frequently allowed the necessary. use of such safety factors due to uncertainties surrounding 

future unit performance. See Prairie State Generating, 13 E.A.D. 1, 75-76 (EAB 2006) (''Variability in the 

observed performance of a control technology is an appropriate circumstance for the permitting authority to 

use a safety factor in setting the permit's BACT limit."); Russell City Energy Center, 15 E.A.D. (EAB 

2010), Slip Op. at 77 (citing cases authorizing use of safety factors). A 20% safety factor is in line with 

those previously approved by the EAB. See, e.g., id. at 74-75 (safety factor of between 22% and 42%); In 

re Cardinal FG CO'l- 12 E.A.D. 153, 169-70 (EAB 2005) (upholding 21 % safety factor for nitrogen oxide 

BACT emission limit).