Attachment	B TSRIA Petition	for	Reconsideration Page B - 1

*Analysis	by	Bison	Engineering,	Inc. **ATTACHMENT B**  ***** **COBURN ROAD DATA QUALITY ISSUES** The Coburn Road sulfur dioxide (SO 2 ) monitoring station was initially established to monitor compliance with the NAAQS of 500 ppb, and other short - term averaging periods in effect at that time . More recently , SO 2 data from Coburn Road was used to determine compliance with the new 75 ppb standard, promulgated b y EPA in June 2010 . EPA reviewed data collected at Coburn Road between 2009 and 2011, and ultimately designated a small portion of the Billings area nonattainment for SO 2 based on that dataset . Bison Engineering, on behalf of TSRIA and the Billings Laurel Air Quality Technical Committee (BLAQTC ) , conducted its own independent evaluation of the Coburn Road data from that period to determine whether that designation is defensible . This document i dentifie s data quality issues that cast doubt on the accuracy of the Coburn Road data used for that calculation . (See Attachment A, detailing more recent Coburn Road data that indicates the area is in compliance with th e 75 ppb standard). The data quality issues are related to the failure to consistently operate the Coburn Road site in accordance with requirements specified by the Montana Department of Environmental Quality ( MDEQ ), federal guidance documents and codified regulations . More specifically , many of the high hourl y SO 2 values used to calculate the 2009

– 2011 Design Value must be considered suspect, because the quality assurance activ ities associated with those data were either 1) not performed as required, or 2) produced unacceptable results and were not followed by specified corrective actions . Those issues are presented in this document an d are outlined below as follows :  Section 1 identifies the applicable MDEQ and federal guidance documents, and federal regulations governing quality assurance requirements for ambient SO 2 monitoring programs – with an emphasis on requirements that were in effect at the time the 2009 - 2011 data were collected ,  Section 2 discusses specific data quality assurance requirements in each applicable document, and summarizes them with respect to three critical quality assurance activities,  Section 3 presents general data quality issues found with the 2009 - 201 1 dataset as a whole, and  Section 4 identifies specific data quality issues (when applicable) associated with each daily maximum hourly

SO 2 concentration of 75 ppb or higher, particularl y during 2010 (which year’s data is **solely** responsible for the SO 2 non attainment designation) , since both 2009 and 2011 (and the 2 years since ) had 99 th

- percentile SO 2 maxima below the 75 ppb standard.Attachment	B TSRIA Petition	for	Reconsideration Page B - 2



### 1. **A PPLICABLE**  

### G **UIDANCE** 

### D **OCUMENTS AND** 

### R**EGULATIONS** Data quality is an essential consideration for any ambient air monitoring program . To facilitate the collection of high - quality ambient monitoring data (both for SO 2 and other parameters) , state and federal guidance documents and regulations have been issued addressing the collection of ambient monitoring data, and specifically SO 2 . The purpose of this section is to outline documents and regulations that govern quantitative measures of data quality, and arrive at a sy nthesized compilation of data quality requirements that should be applied to the Coburn Road dataset. In the case of conflicting requirements , particularly state versus federal , state requirements must , as a rule, be **at least as stringent** as federal requirements . However, s tates are free to mandate **stricter** requirements than those identified at the federal level . **1.1 MDEQ Requirements**  1.1.1 MDEQ QAPP MDEQ formall y issued an update to a Quality Assurance Project Plan (QAPP) for the Montana Ambient Air Monitoring Program in 1996 . The 1996 QAPP incorporated new State and Federal air monitoring requirements . Draft updates were prepared in 2005 and 2009, but neither was ever finalized and issued as a formal document . Conceptually , both were similar to the 1996 QAPP but included expanded detail . A formal QAPP update was issued in 2013, after the close of public comments for the 2010 SO 2 designation .

1.1.2 MDEQ Quality

Assurance Form Requirements To facilitate MDEQ QAPP requirements, MDEQ has also developed a number of QA - related data forms used b y station operators and auditors . In most cases, these forms also show acc eptance criteria for each ty pe of QA check performed and appear to be consistent with the 1996 QAPP . Insome cases th e data form criteria are actually stricter than those found in the 1996 QAPP . While the forms themselves do not constitute “regulations” pe r se, these stricter criteria appear to have been listed in response to evolving federal requirements . The criteria on these forms should be applied to the Coburn Road data under the general principle that MDEQ requirements must be at least as strict as fe deral requirements . **1.2 EPA Guidance Document Requirements**  Data quality requirements are also specified in various EPA guidance documents, the most important being the Quality Assurance Handbook for Air Pollution Measurement Sy stems : Volume II, Ambient Air Monitoring Program . That document was originally issued in the late 1970s and has also been updated periodically . The most recent update for purposes of the 2009 - 2011 data was issued in December 2008 (EPA - 454/B - 08 - 003) . This is referred to as “EPA 2008 ” throughout this documentAttachment	B TSRIA Petition	for	Reconsideration Page B - 3

As will be shown later in this document, there is considerable variance between the 1996 MDEQ QAPP requirements and the 2008 EPA requirements .Attachment	B TSRIA Petition	for	Reconsideration Page B - 4

**2 .**  

### Q **UALITY** 

### A **SSURANCE** 

### R**EQUIREMENTS IN** 

### R**EGULATORY** 

### D **OCUMENTS** The 2009

– 2011 Coburn Road data ( and particularly the station’s quality assurance records) were examined to determine compliance with the applicable regulations and guidance documents discussed in Section 1 . Three types of station records were examined for this data quality evaluation . While this review was b y no means exhaustive, it did address the three types of quantitative quality

assurance checks most critical to data integrity :  Zero/span/precision checks,  Calibrations, and  Performance audits Each activity

is described in Section 2.1 . InSection 2.2, state and federal quality requirements are outlined, along with some di scussion of their differences . That section also identifies quality assurance requirements that were applicable to the Coburn Road site during the 2009 - 20 11 period EPA chose to use for design value calculations (mostly from the 1996 QAPP, with a few exceptions) . **2.1 Definition of Quality Assurance Activities**  2.1.1 Manual Zero/Span/Precision (ZSP) Checks Manual ZSP checks are conducted on a frequent basis to demonstrate that an SO 2 analy zer is correctly measuring three known gas concentrations . The guidance documents often differentiate between zero/span checks and precision checks (which are sometimes referred to as QC checks) . In practice, they

are typicall y conducted as a single activity, and include the following:  The zero check is performed to show that the analy zer responds accuratel y to a pollutant - free sample (hence the term “zero”) . Itis accomplished by introducing zero air to the anal yz er, recording its response, and comparing the result to applicable evaluation criteria ;  The span check is performed to show that the analy zer responds accuratel y to a gas concentration that is between 80% and 90% of the anal yz er’s operating range . For example, an anal yz er designed to measure ambient concentrations of up to 500 ppb would be checked at a concentration of 400 - 450 ppb . The corresponding concentration for an analyzer operating at a 0 - 1,000 ppb range would be checked at 800

– 900 ppb.  A precision chec k is performed to show that the analyzer responds accurately to a lower gas concentration that is more representative of expected ambient concentrations (ty

pically below 100 ppb).Attachment	B TSRIA Petition	for	Reconsideration Page B - 5

If the ZSP check produces acceptable results, no adjustments are made to the anal yz er . If any of the check results exceed applicable limits (termed warning limits and control limits, and defined in Table 1 of this Attachment) , the operator proceeds to a calibration as described in Section 2.1.2. 2.1.2 Calibrations A calibration is performed to ensure that an SO 2 analyzer produces accurate responses to known gas concentrations over its entire operating range, and at concentrations relevant to existing ambient standards . The basic sequence is that: 1. Zero air is introduced to the analy zer, and the analyzer’s “zero” is adjusted so that its response is very

close to 0 ppb. 2. Span gas is introduced to the anal yz er, and the analy zer’s span response is adjusted so that its response is very

close to the known span gas concentration. 3. Steps 1 and 2 are repeated as necessary until both the zero and span responses are very close to the known values. 4. Finally , at least 3 additional non - zero gas concentrations in specified ranges are introduced to the anal yz er , and its responses are recorded . As w ith ZSP checks, calibration results must meet acceptance criteria for the associated data to be considered valid . The calibrations also must be performed at specified frequencies.

2.1.3 Audits A performance audit is an independent check of an instrument by a person not involved in its routine operation, using separate standards from those used to operate or calibrate the instrument . The sequence is similar to that for a calibration, except that no adjustments are made b y the auditor . As with calibrations, a udits of an anal yz er are conducted using gas concentrations in specified ranges. **2.2 Specific Quality Assurance Requirements in Regulatory Documents**  In general the applicable regulatory documents discussed in Section 1 provide specific requirements for each of the quality assurance activities discussed in Section 2.1 . They are summarized in Sections 2.2.1 through 2.2.3 .

2.2.1 Zero/Span/Precision (ZSP) Checks As mentioned above, zero/span checks and precision checks are usually performed as a single activity . In some cases precision checks are referred to as single -point quality control (QC checks) . Guidance on ZSP checks is summarized in Table 1.Attachment	B TSRIA Petition	for	Reconsideration Page B - 6

Based on a review of the Coburn Road QA records, MDEQ has clearl y used the 1996 QAPP requirements as its goal , with one exception: Starting in 2010, MDEQ appears to have adopted the EPA 2008 “Critical Criteria” span and precision point error limits of ± 10%, which are in effect control limits as defined in Table 1 . EPA 2008 does not give corresponding warning lim its for those parameters, but MDEQ quite logically adopted a warning limit of ± 7%

– since the purpose of a warning limit is to alert the operator to the need for adjustments before an out - ofcontrol condition occurs . Therefore, the 2009 Coburn Road span and precision check data were evaluated with respect to the MDEQ 1996 warning and control limits of ± 9% and ± 12% . The 2010

– 2011 Coburn Road span and precision data were evaluated with respect to the more stringent limits of ± 7% and ± 10% adopted in 201 0. **TABLE 1 –**  **REQUIREMENTS FOR ZERO/SPAN/PRECISION CHECKS Check Type**  **1996 MDEQ QAPP 2008 EPA Volume II**  **Zero Check** Frequency Once every 2 weeks Once every 2 weeks Concentration Range Zero ppb Zero ppb Warning Limit 1 ± 0.67% of full scale 3 None specified Control Limit2 ± 1% of full scale 4 ± 3% of full scale **Span Check** Frequency Once every 2 weeks Once every 2 weeks Concentration Range 400

– 450 ppb 5 800

– 900 ppb 6 Not explicitly stated Defined as >120% of applicable NAAQS and >99% of data. Warning Limit ± 9% error None specified Control Limit ± 12% error ± 10% error **Precision Check** Frequency Once every 2 weeks Once every 2 weeks Concentration Range 80

– 100 ppb 10

– 100 ppb Warning Limit ± 9% error None specifiedAttachment	B TSRIA Petition	for	Reconsideration Page B - 7

Control Limit ± 12% error ± 10% error 1 Denotes limit that, if exceeded, requires recalibration of the analyzer. 2 Denotes limit that, if exceeded, requires recalibration of the analyzer and invalidation of associated data 3 Equal to 6.7 ppb for analyzer operated at 0

– 1,000 ppb range, 3.4 ppb for 0

– 500 ppb range. 4 Equal to 10 ppb for analyzer operated at 0

– 1,000 ppb range, 5 ppb for 0

– 500 ppb range. 5 Applies to analyzer operated at 0

– 500 ppb range 6Applies to analyzer operated at 0

– 1,000 ppb range

2.2.2 Calibrations Guidance on calibrations is summarized in Table 2, and differs markedl y between the 1996 MDEQ QAPP and EPA 2008 . In general MDEQ applied the 1996 QAPP criteria except, as noted in Table 2, the more stringent calibration acceptance criteria proposed in the 2005 and 2009 Draft QAPPs had been adopted by 2009 (as evidenced by

MDEQ’s own calibration forms). Therefore, MDEQ’s calibration results have been evaluated with respect to those more stringent criteria, with one exception: MDEQ has increased its use of a very low calibration concentration (e.g. ~5 - 10 ppb)

– apparently in response to EPA’s recent emphasis on accuratel y measuring low ambient concentrations.

**TABLE 2 –**  **REQUIREMENTS FOR CALIBRATIONS Parameter**  **1996 MDEQ QAPP 2008 EPA Volume II**  Frequency Every 90 day s at a minimum Once per six months 1 Once per year2 Number of concentrations Total of five (Four non - zero points, plus zero) Total of five (Four non - zero points, plus zero) Concentration ranges 3 800

– 900 ppb 400

– 450 ppb 150

– 200 ppb 30

– 80 ppb Four “upscale” (non - zero points) Evenly spaced over operating range Concentration ranges 4 400

– 450 ppb 250

– 350 ppb 150

– 200 ppb 30

– 80 ppb Four “upscale” (non - zero points) Evenly space over operating rangeAttachment	B TSRIA Petition	for	Reconsideration Page B - 8

Acceptance limits None specified 5 ± 2% for span point 6 ± 5% for other non - zero points 6 ± 0.5% of full scale for zero All points within 2% of full scale of best - fit straight line 7

1 Frequency applies if manual zero/spans are performed every 2 weeks 2 Frequency applies if continuous zero/spans are performed daily 3 For instrument operated at 0

– 1,000 ppb range 4 For instrument operated at 0

– 500 ppb range 5 1996 MDEQ QAPP only requires confirmation of points in error by > ± 2% 6 Limits in 2005 and 2009 Draft MDEQ QAPPs, and on MDEQ calibration form 7 This equates to ±10 ppb for an analyzer operated at 0 - 500 ppb range, and ±20 ppb for an analyzer operated at 0

– 1,000 ppb scale.

2.2.3 Audits Guidance on performance audits is summarized in Table 3. Based on a review of the Coburn Road QA data, MDEQ used the 1996 QAPP requirements as its goals in 2009 and 2010. However, in 2011 MDEQ began using significantly lower audit concentrations. This appears to have been done in response to the EPA 2008 guidance document recommendations. Those recommendations identified several “audit levels” quite different from historical practice. Therefore, the 2009 and 2010 audit data are evaluated based on the 1996 MDEQ QAPP requirements, while the 2011 data are evaluated based on EPA 2008 . Another nuance of this evaluation concerns the audit criteria for very low known gas concentrations. EPA 2008 set an audit performance criterion of ± 15%, regardless of gas concentration. However, it was soon recognized that this criterion was virtually impossible to meet at very

low c oncentrations. EPA officiall y modified the criterion in 2013 so that the acceptable error for very

low audit points was ± 1.5 ppb. Therefore, that more lenient criterion was used to evaluate the Coburn Road data where applicable, since that was ultimately the EPA standard. **TABLE 3 –**  **REQUIREMENTS FOR AUDITS Parameter**  **1996 MDEQ QAPP 2008 EPA Volume II**  Frequency Each site 1/year 25% of sites 1/quarter Each site 1/year 25% of sites 1/quarter Concentration ranges 1 800

– 900 ppb 3 consecutive auditAttachment	B TSRIA Petition	for	Reconsideration Page B - 9 350

– 450 ppb 150

– 200 ppb 30

– 80 ppb concentrations not including zero 2 Concentration ranges 3 350

– 450 ppb 150

– 200 ppb 30

– 80 ppb 3 consecutive audit concentrations not including zero 2 Acceptance limits ± 15% at each point ± 3% of full scale for zero Plus linear regression criteria4 ± 15% of reading at each point 5 ± 1.5 ppb at lowest audit levels 6

1 For instrument operated at 0

– 1,000 ppb range 2 Refers to audit levels described in more detail in EPA 2008 3 For instrument operated at 0

– 500 ppb range 4Audit results also evaluated on basis of linear regression results. In most cases the limit of ± 15% at each point is the most restrictive. 5 This limit was set before the widespread use of very low audit gas concentrations 6 This limit appears in EPA’s 20 13 modification (see section 2.2.3 above), and recognizes the difficulty of meeting the ± 15% criterion at very low audit gas concentrations.Attachment	B TSRIA Petition	for	Reconsideration Page B - 10

**3.** 

### G**ENERAL** 

### C **OBURN** 

### R**OAD** 

### D **ATA** 

### Q **UALITY** 

### I **SSUES** The 2009

– 2011 Coburn Road data records were evaluated with respect to the acceptance criteria presented in Tables 1, 2 , and 3 . The types of data quality issues identified are discussed below.  **Zero/Span/Precision (ZSP)**  **check results exceeding warning limits and control limits were often**  **not followed by appropriate corrective actions**  . Paragraph 6 of QAPP Section 9.8.4 states that “ If the analyzer's response exceeds either the upper or lower control limits for either the zero or span it shall be deemed "out of control" and shall be recalibrated immediately (within o ne working day) .” Paragraph 7 of QAPP Section 9.8.4 states that “ If the analyzer's response exceeds either the upper or lower warning limits for either zero or span, the point shall be repeated immediately (same working day) . If the analyzer's response to the second point also exceeds the warning limits, the analyzer shall be deemed "out of control" and recalibrated immediately (within one working day). If the response does not exceed the warning limits, the analyzer shall be deemed "in control" and no adjustments are necessary .” Finally , Part B of QAPP Section 15.1 shows warning and control limits for precision point checks of 9.0% and 12.0%, respectivel y (identical to those for span checks) . Over the 2009 - 2011 period, there were 9 occasions where one or more unsatisfactory Z SP result was not followed up b y corrective action. Eight of these events involved the precision point

—the concentration most relevant to the 75 ppb standard.

 **Calibrations were often not performed at the prescribed 90 -** **day intervals** . The 1996 QAPP in Section 9.8.7, Item 5 states that “Each continuous gas analyzer shall receive a multi-

point calibration at least every 90 days. ( **This is a minimum requirement** .) ” [Emphasis added] . The interval between successive calibrations associated wi th the 2009

– 2011 data exceeded 90 days five times . These excessive intervals ranged from 99 day s, to as many as 162 day s .  **Calibrations were sometimes performed using an insufficient number of “upscale” (non**   ** zero) gas concentrations** . Both EPA 2008 and the 1996 MDEQ QAPP clearly require a zero concentration, plus **four** upscale points . In three instances, only three non - zero concentrations were used; and in those instances, no concentrations in the vicinity of 75 ppb were checked. The nearest higher concentration in those instances was 197 ppb, while the nearest lower concentration was 23 ppb.

 **Calibration results were**  **outside of**  **acceptance limits** This occurred on one occasion , when the calibration error at the high (“span”) point exceeded the prescribed limit .Attachment	B TSRIA Petition	for	Reconsideration Page B - 11

 **Specified gas concentration ranges were not used for several**  **performance audits .**  The 1996 QAPP clearl y i dentifies required concentration ranges for performance audits, which were not adhered to for s even audits .  **In one instance, an u nacceptable**  **audit result w as**  **not followed by specified corrective action.** 

 **Expired gas cylinders were occasionally used**  **for both**  **audits and routine site operations .**  Part B of QAPP Section 9.8.7 clearl y states that “ If cylinders are used in the calibration, they must have been certified within the time frame specified in Table 9.8B [i.e. 24 months] . Check the certification date on the cylinder's label or tag to verify the certification is current. ” An expired gas cylinder was used for one performance audit , and for on e multipoint calibration. Additionally, calibration records strongly indicate that an expired gas cylinder was used for ZSP checks conducted from May 25, 2009 through at least July

21, 2009 (since the same gas standard is ty picall y used for both ZSP check s and calibrations). An exhaustive review and evaluation of each of the more than 25,000 hours of Coburn Road data collected between 2009 and 2011 is beyond the scope of this document . However, a very small fraction of those hourly

readings (<0.01%) were entirely responsible for the SO 2 nonattainment designation, and data quality issues associated with each reading are discussed in Section 4 of this document.Attachment	B TSRIA Petition	for	Reconsideration Page B - 12

**4 .**  

### D **ATA** 

### Q **UALITY** 

### I **SSUES** 

### A **SSOCIATED WITH** 

### H **IGH** 

### SO **2** 

### R**EADINGS** The fifteen high (at or above 75 ppb) SO 2 readings between 2009 and 2011 each had one or more associated data quality

issue , and each issue listed in Section 3 was found for at least one of the high SO 2 readings. Table 4 lists each of the high (at or above 75 ppb) SO 2 readings observed between 2009 and 2011, along with their associated data quality issues . Table 4 illustrates that the fifteen high readings being used to justify the SO 2 nonattainment designation were not collected in strict accordance with the 1996 MDEQ QAPP and other EPA guidance documents . Additionally , the SO 2 analyzer itself has inherent accuracy limitations . MDEQ records indicate that the Coburn Road site employed an API Model 100A SO 2 analy zer during the 2009

– 2011 monitoring period . A review of the manufacturer’s data sheet for this anal yzer [1] reveals a linearity specification of 1% of full scale , which has important consequences for data precision . The 4 ppb difference between the Coburn Road site design value and the 75 ppb standard represents only

0.4% of the instrument’s full - scale range when operated at a 0 - 1,000 ppb range . This difference increases to 0.8% when the instrument is operated on a 0 - 500 ppb range . The Coburn Road instrument was operated on the higher scale during 2009 and most of 2010; it was re - scale d in later 2010 to 500 ppb. The concept of linearity i s best illustrated with an example: consider an analy zer operated at a 0 - 1,000 ppb full scale range . If the instrument actually read 1,000 ppb at a known gas concentration of 1,000 ppb, and zero ppb at a known concentration of zero ppb, perfect linearity would exist if, at a known concentration of 75 ppb the instrument read 75 ppb . The 1% of full scale linearity

specification indicates that at any known gas concentration **between** 0 and 1,000 ppb, the ins trument response could differ from the expected value b y up to 10 ppb (even if the instrument were in perfect calibration at 0 and 1,000 ppb) . Thus, the instrument response to a known concentration of 75 ppb could range between 65 and 85 ppb, and still satisfy the instrument’s linearity

specification . Even for an instrument operated at a 0 - 500 ppb range, the response could range from 70 to 80 ppb. Both potential linearity errors are greater than the 4 ppb difference between the Coburn Road site monitor’s 79 ppb design value and the 75 ppb standard, and call into question whether it is known with certainty that the measured 79 ppb design value is in fact greater than 75 ppb .

[1] Instruction Manual Teledyne API Model 100A Sulfur Dioxide Analyzer – Rev. H. Teledyne Advanced Pollution Instrumentation, 24 February 2006.Attachment	B TSRIA Petition	for	Reconsideration Page B - 13 **TABLE 4 QUALITY ISSUES FOR HIGH SO**  **2 READINGS AT COBURN ROAD**  **DATE SO**  **2**

**(ppb) REMARKS**  2009 Feb 5 83  Interval between preceding (9/10/2008) and following (2/19/2009)

anal yz er calibration was 16 2 days  The audit gas concentration ranges specified in (MDEQ 1996) were not adhered to in the preceding (12/12/2008) and following (2/25/2009) audits Sep 22 Sep 25 107

83  Interval between preceding (9/17/2009) and following (1/11/2010)

anal yz er calibration was 116 day s  The audit gas concentration ranges specified in (MDEQ 1996) were not adhered to in the preceding (8/12/2009) audit 2010 Feb 10 91  The audit gas concentration ranges specified in (MDEQ 1996) were not

adhered to in the following (3/23/2010) audit  The preceding precision point check (2/9/2010) error of - 7.2% exceeded the warning limit, but no corrective action was taken. Jul 8 Jul 9 111

92  The audit gas concentration ranges specified in (MDEQ 1996) were not

adhered to in the preceding (6/22/2010) audit  The error for the lowest audit point (+48.8% / +3.9 ppb) exceeded the acceptance criterion, but no corrective action was taken.  Interval between preceding (4/15/2010) and following (8/23/2010) anal yz er calibration was 130 day s  The following calibration (8/23/2010) was performed using onl y 3 upscale points, rather than the four specified in (MDEQ 1996) . None of the calibration points were in the vicinity of 75 ppb.  The preceding zero check (6/28/2010) error of +0.7% of full scale exceeded the warning limit, but no corrective action was taken. Sep 26 Sep 28 Oct 2 Oct 3 78

83 75 87  The audit gas concentration ranges specified in (MDEQ 1996) were not

adhered to in the following (12/1/2010) audit  The preceding (8/23/2010) and following (11/5/2010) calibrations were performed using onl y 3 upscale points, rather than the four specified in (MDEQ 1996) . None of the calibration points were in the vicinity of 75 ppb. /Attachment	B TSRIA Petition	for	Reconsideration Page B - 14 **TABLE 4 –**  **Continued QUALITY ISSUES FOR HIGH SO**  **2 READINGS AT COBURN ROAD**  **DATE SO**  **2**

**(ppb) REMARKS**  2010 Oct 22 89  The preceding (8/23/2010) and following (11/5/2010) calibrations were performed using only 3 upscale points, rather than the four specified in (MDEQ 1996). None of the calibration points were in the vicinity of 75 ppb.  The interval between the preceding (10/4/2010) and following (10/25/2010) ZSP checks exceeded two weeks  The audit gas concentratio n ranges specified in (MDEQ 1996) were not adhered to in the following (12/1/2010) audit Dec 24 101  The audit gas concentration ranges specified in (MDEQ 1996) were not

adhered to in the preceding (12/1/2010) audit  The preceding (11/5/2010) and following (1/5/2011) calibrations were performed using onl y 3 upscale points, rather than the four specified in (MDEQ 1996). None of the calibration points were in the vicinity of 75 ppb. 2011 Sep 5 Sep 11 142

113  An expired gas cylinder standard was used for the following (12/7/2011)

performance audit Oct 30 85  An expired gas cylinder standard was used for the following (12/7/2011)

performance audit  The following (11/17/2011) anal yz er calibration had a span error of

- 3.47%.