Swansea Ambient Air Monitoring Station (SAMS) 1st Quarter PY2018 Air Quality Data Report

Transcription

1 Swansea Ambient Air Monitoring Station (SAMS) 1st Quarter PY2018 Air Quality Data Report Prepared for the Colorado Department of Transportation and the City and County of Denver, Department of Environmental Health Airtech/Montrose Project No Report ID: 6203-Q January 11, 2018

2 Report ID: 6203-Q Table of Contents PROJECT OVERVIEW... 1 Background... 1 Objectives... 1 Operational Staff and Contacts... 2 SAMS Site Description... 3 Picture 1 Location of SAMS in the Swansea Elementary School Parking Lot... 3 Picture 2 Interior of SAMS... 3 SAMS Equipment... 4 Discussion of Results and Professional Judgment... 4 POLLUTANT DATA COLLECTED... 7 Figure 1a Monthly PM 10 Data... 7 Figure 1b Monthly PM 10 Data... 8 Figure 1c Monthly PM 10 Data... 9 Figure 2a Monthly PM 2.5 Data Figure 2b Monthly PM 2.5 Data Figure 2c Monthly PM 2.5 Data Figure 3a Monthly NO 2 Data Figure 3b Monthly NO 2 Data Figure 3c Monthly NO 2 Data Figure 4a Monthly CO Data Figure 4b Monthly CO Data Figure 4c Monthly CO Data Figure 5a Monthly Black Carbon Data Figure 5b Monthly Black Carbon Data Figure 5c Monthly Black Carbon Data Table 1a Monthly Summary of VOC Data Table 1b Monthly Summary of VOC Data Table 1c Monthly Summary of VOC Data Table 2 Reporting and Quantification Limits for Selected VOC Compounds DATA QUALITY ASSURANCE/QUALITY CONTROL Quality Assurance/Quality Control NOX and CO Analyzers - Span Test NOX and CO Analyzers - Precision Test PM2.5 / PM10 Analyzer Aethalometer Wind Speed and Wind Direction Gas Chromatograph SIGNATURE PAGE APPENDIX Quality Assurance Logs Calibration Certification Sheets Primary Flow Standard Certification Sheet

3 Report ID: 6203-Q Page 1 Project Overview Background Colorado Department of Transportation (CDOT) and Denver Environmental Health (DEH) entered into an agreement 1 to monitor air quality at Swansea Elementary School in three phases. Phase I will monitor air quality for one year prior to startup of a CDOT construction project on Interstate 70 (I-70). Phase II will monitor air quality for three (3) years during the I-70 expansion project; construction may last more than three years. Phase III will monitor air quality for one year after I-70 construction and ground disturbance activities are completed. The monitoring aspect of Phase I began on April 1, The monitoring project scope of work, which is an attachment to the agreement, defined the first quarter of a year as beginning on September 1. Therefore, monitoring began in the third quarter of the 2017 project year (Q3 PY2017). Objectives Airtech Environmental Services Inc. (a Montrose Air Quality Services, LLC Company) was contracted by the City and County of Denver to start up and operate the Swansea Air Monitoring Station (SAMS). The SAMS is located at the Swansea Elementary School; faculty parking lot; South East Corner; at 4650 Columbine Street, Denver, Colorado. This report represents the first quarterly report for Phase I. The station monitored the following parameters during Q1 PY2018: C6 (6-Carbon) through C12 (12-Carbon) Volatile Organic Compounds (VOC) Black Carbon Carbon Monoxide (CO) Particulate Matter less than 10 Microns (PM10) Particulate Matter less than 2.5 Microns (PM2.5) Meteorological Measurements Nitrogen Oxides (NOx) The monitoring is being performed to meet the requirements of the agreement between CDOT and DEH. Additionally, the regulations and specifications set forth by the Colorado Department of Public Health and Environment (CDPHE) and the United States Environmental Protection Agency (USEPA), are being followed as applicable. 1 The agreement between CDOT and DEH became effective on August 12, 2016 and can be obtained from CDOT by referencing routing number 17-HTD-ZH

4 Report ID: 6203-Q Page 2 Operational Staff and Contacts The contact information for each of the principal parties is summarized in the table below: Rebecca White Colorado Department of Transportation 5640 E. Atlantic Place 200 W 14th Ave Denver, CO Denver, CO Michael Ogletree City and County of Denver Phone: (303) Phone: (720) rebecca.white@state.co.us Michael.Ogletree@denvergov.org

5 Report ID: 6203-Q Page 3 SAMS Site Description Region: Denver AQS ID: Latitude: Longitude: Picture 1 Location of SAMS in the Swansea Elementary School Parking Lot Picture 2 Interior of SAMS

6 Report ID: 6203-Q Page 4 SAMS Equipment The list of primary equipment used in this project is shown in the table below. Airtech/Montrose has supplied and installed the following: Glass lined sample probe Glass sampling manifold Sample blower, fittings, and tubing Instrument rack Cylinder mounts, calibration gases and regulators Security camera Pollutant/Parameter Sampling Period Manufacturer Model Nitrogen Oxides Minute Teledyne T200U Carbon Monoxide Minute Thermo Scientific 48i-TLE Trace Level CO Dynamic Dilution Calibrator Periodic Teledyne T700U PM 2.5 / PM 10 Minute GRIMM 180 EDM Technologies Inc. Meteorological measurements Minute GRIMM 180 EDM (temperature, pressure, relative humidity) Technologies Inc. Meteorological measurements Minute RM Young 05305V (wind speed and wind direction) C 6 through C 12 VOCs 30 Minutes Chromatotec Airmo C6-C12 (Model A27022) Black Carbon 5 Minutes Magee Scientific Aethalometer Data Logger (with remote accessibility) Multiple Agilaire 8872 Discussion of Results and Professional Judgment The reported data is for the first quarter PY2018 which is considered, September, October and November. The RM Young meteorological station was installed on 8/15/17, but due to a wind direction calibration issue no valid data has been collected, the station is currently being re-calibrated by the manufacturer. On 11/3/17 a grounding issue was resolved on the RM Young but after an audit was conducted an 8 degree error in the wind direction was found, invalidating the data collected during November.

7 Report ID: 6203-Q Page 5 The results of NO2, CO, PM2.5, PM10, black carbon and VOC monitoring data can be found in Figures 1 through 5 and Table 1 on Pages 7 through 24. The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. The graphs shown indicate the readings for each month relative the NAAQS Standard (if applicable). Electronic records of all data and calibrations have been uploaded to the Dropbox data room maintained by DEH. At 10:35 am on 9/24/17 the power went out at the SAMS and was not restored until 08:29 am on 9/25/17. During this approximately 22 hour outage no data was collected. This report only used the hours of data collected on those days to calculate 24 hour averages for those days. The PM hour standard of 35 ug/m 3 was exceeded on 9/4/17 and 11/10/17. The 9/4/17 PM hour standard exceedance of 51.2 ug/ m 3 was attributed to very dense smoke plumes from wild fires in western Montana, Northern Idaho, Washington, and Northern California. The elevated levels in PM2.5 in the days before and after 9/4/17 are also due to the wild fires in the Northeast. The 11/10/17 PM hour standard exceedance of 38.3 ug/ m 3 was due to a very strong surface temperature inversion. This causes stagnant air, trapped by the temperature inversion, to sit over Denver all day. Winds around the SAMS were remained below 6 mph all day, also pointing to local stagnation. Without other contradictory data, this spike in PM2.5 was local Denver emissions trapped by stagnate meteorology. PM2.5 was elevated at most (but not at Chatfield and National Jewish) of the Denver area PM2.5 stations for most of the middle of the day. No other pollutant standards were exceeded during Q1 PY2018. An exceptional event is any unusual or naturally occurring event that can affect air quality but cannot not be reasonably controlled using techniques that agencies may implement in order to attain and maintain the NAAQS. All exceptional events are documented by CDPHE. As of 1/11/18 CDPHE has not declared the above events on 9/4/17 and 11/10/17 as exceptional events. The aethalometer, GRIMM, and all meteorological equipment was calibrated weekly with no unusual results or maintenance issues this quarter. The Chromatotec Gas Chromatograph (GC) for C6 through C12 was calibrated daily by running a permeation benzene tube and zero air checks with no unusual results this quarter while the GC was in operation. The CO and NOX analyzers were calibrated daily by diluting an EPA Protocol 1 calibration. No maintenance issues were observed during the sampling period. Unusual calibration results were observed as follows: The CO monitor was regularly exceeding

8 Report ID: 6203-Q Page 6 the 10% precision requirement when analyzing the one (1) ppm calibration mixture. These exceedances fell between an 11 to 15% error. Considering the ambient levels of CO were found to be well below the 1-hour and 8-hour standards we consider the ramifications for the exceedances to be negligible. The CO analyzer precision level calibration mixture was increased to 1.5 ppm on 1/3/18 to increase the acceptable range of error, which should increase the passing rate of the precision level calibration. The NO2 monitor was regularly exceeding the 10% precision requirement when analyzing the seventy (70) ppb calibration mixture. These exceedances fell between an 11 to 18% error. The Gas Phase Titration (GPT) used to produce the NO2 gas by mixing O3 and NO gas is created with the Dynamic Gas Dilution Calibrator. The Gas Phase Titration Pre-Set (GPTPS) is run to calibrate the ozone generator to improve the accuracy of the O3 concentration. A GPTPS will be run weekly beginning 1/5/18. This should increase the passing rate of the precision level calibration.

9 Report ID: 6203-Q Page 7 Pollutant Data Collected Figure 1a Monthly PM10 Data The graph below is shown for September and is the plot of the 24 hour averages. The orange line represents the 150 micrograms per cubic meter (ug/m 3 ) 24 hour ambient PM10 standard.

10 Report ID: 6203-Q Page 8 Figure 1b Monthly PM10 Data The graph below is shown for October and is the plot of the 24 hour averages. The orange line represents the 150 ug/m 3 24 hour ambient PM10 standard.

11 Report ID: 6203-Q Page 9 Figure 1c Monthly PM10 Data The graph below is shown for November and is the plot of the 24 hour averages. The orange line represents the 150 ug/m 3 24 hour ambient PM10 standard.

12 Report ID: 6203-Q Page 10 Figure 2a Monthly PM2.5 Data The graph below is shown for September and is a plot of the 24 hour averages. The orange line represents the 35 ug/m 3 24 hour ambient PM2.5 standard and the yellow line represents the 12 ug/m 3 one (1) year mean ambient PM2.5 standard. Please note that the 24 hour average values cannot be directly compared to the annual mean standard.

13 Report ID: 6203-Q Page 11 Figure 2b Monthly PM2.5 Data The graph below is shown for October and is a plot of the 24 hour averages. The orange line represents the 35 ug/m 3 24 hour ambient PM2.5 standard and the yellow line represents the 12 ug/m 3 one (1) year mean ambient PM2.5 standard. Please note that the 24 hour average values cannot be directly compared to the annual mean standard.

14 Report ID: 6203-Q Page 12 Figure 2c Monthly PM2.5 Data The graph below is shown for November and is a plot of the 24 hour averages. The orange line represents the 35 ug/m 3 24 hour ambient PM2.5 standard and the yellow line represents the 12 ug/m 3 one (1) year mean ambient PM2.5 standard. Please note that the 24 hour average values cannot be directly compared to the annual mean standard.

15 Report ID: 6203-Q Page 13 Figure 3a Monthly NO2 Data The graph below is shown for September is a plot of the one (1) hour averages. The orange line represents the 100 parts per billion (ppb) one (1) hour ambient NO2 standard and the yellow line represents the 53 ppb one (1) year mean ambient NO2 standard. Please note that the one (1) hour average values cannot be directly compared to the annual mean standard.

16 Report ID: 6203-Q Page 14 Figure 3b Monthly NO2 Data The graph below is shown for October is a plot of the one (1) hour averages. The orange line represents the 100 ppb one (1) hour ambient NO2 standard and the yellow line represents the 53 ppb one (1) year mean ambient NO2 standard. Please note that the one (1) hour average values cannot be directly compared to the annual mean standard.

17 Report ID: 6203-Q Page 15 Figure 3c Monthly NO2 Data The graph below is shown for November is a plot of the one (1) hour averages. The orange line represents the 100 ppb one (1) hour ambient NO2 standard and the yellow line represents the 53 ppb one (1) year mean ambient NO2 standard. Please note that the one (1) hour average values cannot be directly compared to the annual mean standard.

18 Report ID: 6203-Q Page 16 Figure 4a Monthly CO Data The graph below is shown for September and is a plot of the one (1) hour averages. The orange line represents the nine (9) ppm eight (8) hour ambient CO standard and the yellow line represents the 35 ppm one (1) hour ambient CO standard.

19 Report ID: 6203-Q Page 17 Figure 4b Monthly CO Data The graph below is shown for October and is a plot of the one (1) hour averages. The orange line represents the nine (9) ppm eight (8) hour ambient CO standard and the yellow line represents the 35 ppm one (1) hour ambient CO standard.

20 Report ID: 6203-Q Page 18 Figure 4c Monthly CO Data The graph below is shown for November and is a plot of the one (1) hour averages. The orange line represents the nine (9) ppm eight (8) hour ambient CO standard and the yellow line represents the 35 ppm one (1) hour ambient CO standard.

21 Report ID: 6203-Q Page 19 Figure 5a Monthly Black Carbon Data The graph below is shown for September and plots the 24 hour averages. Black Carbon does not have a NAAQS Standard.

22 Report ID: 6203-Q Page 20 Figure 5b Monthly Black Carbon Data The graph below is shown for October and plots the 24 hour averages. Black Carbon does not have a NAAQS Standard.

23 Report ID: 6203-Q Page 21 Figure 5c Monthly Black Carbon Data The graph below is shown for November and plots the 24 hour averages. Black Carbon does not have a NAAQS Standard.

24 Report ID: 6203-Q Page 22 The results of the selected VOC compounds are shown in the table below. Electronic records of all VOC compounds have been uploaded to the Dropbox data room maintained by DEH. When calculating the average, the following rules were applied: If an individual result was above the reporting limit (RL), the result was used in calculating the average If an individual result was below the RL or not detected, one half the RL was used in calculating the average. Table 1a Monthly Summary of VOC Data The table below is shown for September and averages 30 minute runs. None of the compounds reported have a NAAQS Standard. Compound Average Result for September (ppb) Total Number of Data Points Number Above QL 2 Number Between RL and QL Number Below RL N-Hexane N-Heptane N-Octane Benzene Toluene Ethylbenzene m,p-xylene o-xylene Quantification Limit (QL)

25 Report ID: 6203-Q Page 23 Table 1b Monthly Summary of VOC Data The table below is shown for October and averages 30 minute runs. None of the compounds reported have a NAAQS Standard. Compound Average Result for October (ppb) Total Number of Data Points Number Above QL 3 Number Between RL and QL Number Below RL N-Hexane N-Heptane N-Octane Benzene Toluene Ethylbenzene m,p-xylene o-xylene Quantification Limit (QL)

26 Report ID: 6203-Q Page 24 Table 1c Monthly Summary of VOC Data The table below is shown for November and averages 30 minute runs. None of the compounds reported have a NAAQS Standard. Compound Average Result for November (ppb) Total Number of Data Points Number Above QL 4 Number Between RL and QL Number Below RL N-Hexane N-Heptane N-Octane Benzene Toluene Ethylbenzene m,p-xylene o-xylene Table 2 Reporting and Quantification Limits for Selected VOC Compounds The RLs and QLs for the selected compounds is shown in the table below: Reporting Compound Limit (ppb) Quantification Limit (ppb) N-Hexane N-Heptane N-Octane Benzene Toluene Ethylbenzene m,p-xylene o-xylene Quantification Limit (QL)

27 Report ID: 6203-Q Page 25 Data Quality Assurance/Quality Control Quality Assurance/Quality Control Quality assurance is a general term for the procedures used to ensure that a particular measurement meets the quality requirements for its intended use. Quality control of continuous analyzers consists of precision and span checks or flow verifications. Quality objectives were assessed via laboratory and site system audits. All work being done on this project follows the operating procedures described in the Swansea Air Monitoring Station Quality Assurance Project Plan (QAPP) dated 7/1/17. The QAPP can be provided by Michael Ogletree upon request. Mr. Ogletree s contact information can be found in the Operational Staff and Contacts section of this report. To ensure the collection of high quality data, the following Quality Assurance/Quality Control procedures were implemented: NOX and CO Analyzers - Span Test A span test was conducted every other day. The NOX span test started at 21:46 and lasted for approximately 50 minutes. The CO span test started at 22:46 and lasted for approximately 20 minutes. A CO span test was conducted by first analyzing a span gas of CO which was introduced to the sampling manifold at the back of the analyzer. After a stable reading was reached and recorded, a zero gas was introduced to the sampling manifold at the back of the analyzer. The CO gas was generated by diluting an EPA Protocol 1 calibration gas using the Teledyne Dynamic Dilution Calibrator. An NO/NO2 span test was conducted by first analyzing a zero gas that was introduced to the sampling manifold at the back of the analyzer. After a stable reading was reached and recorded, a span gas of NO was introduced to the sampling manifold at the back of the analyzer. The NO gas was also generated by diluting an EPA Protocol 1 calibration gas using the Teledyne Dynamic Dilution Calibrator. After a stable reading was reached and recorded, a span gas of NO2 was generated by diluting an EPA Protocol 1 calibration gas and combing the diluted gas with a known quantity of ozone (O3) using the Teledyne Dynamic Dilution Calibrator. After a stable reading was reached and recorded, a zero gas was introduced to the sampling manifold at the back of the analyzer. Each calibration gas was certified according to EPA Protocol 1 procedures. The generated gases were approximately, five (5) ppm of CO, 400 ppb of NO and 300 ppb of NO2. In all cases the measured responses were then compared to the generated gas value to determine the analyzer drift. The EPA requirement for span is 10 percent. The span check results are summarized in the table below:

28 Report ID: 6203-Q Page 26 Parameter Span Count 5 Span Passed Span Percentage Nitrogen Oxide Nitrogen Dioxide Carbon Monoxide NOX and CO Analyzers - Precision Test A precision test was conducted every other day. The NOX precision test started at 21:46 and lasted for approximately 50 minutes. The CO precision test started at 22:46 and lasted for approximately 20 minutes. A CO precision test was conducted by first analyzing a precision gas of CO which was introduced to the sampling manifold at the back of the analyzer. After a stable reading was reached and recorded, a zero gas was introduced to the sampling manifold at the back of the analyzer. The CO gas was generated by diluting an EPA Protocol 1 calibration gas using the Teledyne Dynamic Dilution Calibrator. An NO/NO2 precision test was conducted by first analyzing a zero gas that was introduced to the sampling manifold at the back of the analyzer. After a stable reading was reached and recorded, a precision gas of NO was introduced to the sampling manifold at the back of the analyzer. The NO gas was also generated by diluting an EPA Protocol 1 calibration gas using the Teledyne Dynamic Dilution Calibrator. After a stable reading was reached and recorded, a precision gas of NO2 was generated by diluting an EPA Protocol 1 calibration gas and combining the diluted gas with a known quantity of ozone (O3) using the Teledyne Dynamic Dilution Calibrator. After a stable reading was reached and recorded, a zero gas was introduced to the sampling manifold at the back of the analyzer. Each calibration gas was certified according to EPA Protocol 1 procedures. The generated gases were approximately, one (1) ppm of CO, 100 ppb of NO and 70 ppb of NO2. In all cases the measured responses were then compared to the generated gas value to determine the analyzer drift. The EPA requirement for span is 10 percent. The span check results are summarized in the table below: Parameter Precision Count Precision Passed Span Percentage Nitrogen Oxide Nitrogen Dioxide Carbon Monoxide Due to a power outage from the morning of 9/24/17 to the morning of 9/25/17 a Span Test was inadvertently skipped

29 Report ID: 6203-Q Page 27 PM2.5 / PM10 Analyzer A zero check was conducted on the GRIMM analyzer every two (2) weeks. The zero check was conducted by placing a particulate filter inline and observing the response of the analyzer. If anything other than a zero reading was observed, corrective action was taken. Additionally, a flow check was conducted on the analyzer by using a NIST traceable standard to measure the flow rate through the GRIMM. The NIST standard was a MesaLabs DCL-MH DryCal flowmeter. The calibration certification can be found in the Appendix of this report. The flow test was considered acceptable if the flow rate was between 1.15 and 1.25 liters per minute (lpm). On a weekly basis the met station ambient temperature, relative humidity, and pressure was checked by comparing the measured values to that of a reference standard. The results were considered acceptable if the temperature, relative humidity, and pressure was within 2 o C, 5%, and 10 mmhg, respectively. A summary of the weekly and biweekly checks is summarized below. Test Count 6 Passed Percentage Zero Check % Flow Check % Temperature Check % Pressure Check % Aethalometer On a monthly basis the aethalometer cyclone was cleaned and inspected. A flow check was conducted using a NIST traceable standard to measure the flow rate through the aethalometer. The NIST standard was a MesaLabs DCL-MH DryCal flowmeter. The calibration certification can be found in the Appendix of this report. The flow test was considered acceptable if the flow rate was within seven (7) percent of the measured value. Additionally, a leak check was conducted by capping the sample probe and observing the measured flow through the instrument. The leak check was considered valid if the measured flow rate was less than 2.5 liters per minute (lpm). A summary of the monthly checks and is summarized below: Test Count Passed Percentage Flow Check % Leak Check % 6 Temperature and Pressure check on 11/20/17 was not completed due to the unavailability of a technician

30 Report ID: 6203-Q Page 28 Wind Speed and Wind Direction The wind speed is calibrated via an anemometer drive that provides a convenient and accurate way to rotate the anemometer shaft at a known rate. The known rate that the drive rotates can then be compared to the wind speed reading on the data logger. The wind direction is calibrated with a vane angle bench stand. The monitor is placed on the stand which has a base with markings of 0 to 360 degrees. The tail of the monitor is stabilized so that as the monitor is rotated the wind direction readings are stable on the data logger. Because the RM Young sensor was not collecting valid data during Q1 PY2018 no QA/QC was performed. Gas Chromatograph The GC was calibrated prior to installation using a gas standard containing a known concentration of the Photochemical Assessment Monitoring Station (PAMS) list of compounds. A copy of the calibration certification can be found in the Appendix of this report. Two (2) additional concentrations were prepared and analyzed by diluting the cylinder gases using zero air and a Thermo Model 146i Multi-Gas Calibrator. A multipoint calibration of the GC was conducted before monitoring commenced. The calibration also identifies 35 compounds (or pairs of compounds that coelute). An example of the calibration for one of these compounds, benzene, is shown in the following figure. This calibration spans the concentration range from about 1 to 17 ppb. Similar calibrations were done for the other PAMS compounds identified by the GC.

31 Report ID: 6203-Q Page 29 The PAMS calibration data collected on 9/28/2017 was prior to recalibration of the mass flow controller used for dilution of the PAMS gas mixture. This lead to an inaccurate calibration. Additional PAMS calibration data was collected on 10/31/2017, after recalibration of the flow controller. Four repeated samples were collected at a single concentration with a measured response of about 93% of actual. No BTEX gas runs were sampled during Q1 PY2018. The detection limit for the GC technique was determined from data collected during repeated measurements of a low concentration PAMS standard mixture. The detection limit is three (3) times the standard deviation of low concentration measurements for the individual compounds. Because some peaks are close together, there is a greater uncertainty for partially overlapping peaks and small retention time shifts. We have chosen to use a reporting limit, as the smallest concentration where we have confidence that the compound is present. The smallest reporting limit has been set at 0.1 ppb and is greater than or equal to three times the standard deviation for each of the compounds. Compounds present at concentrations equal to the detection limit (or reporting limit, in this case) are believed to be present, but concentrations near this limit are highly

32 Report ID: 6203-Q Page 30 uncertain. Data to be used quantitatively should exceed the quantitation limit. This limit is used to identify when the concentration that was measured for the compound is known with a reasonable degree of confidence. The quantitation limit is normally defined as 10 times the standard deviation of low concentration measurements for individual compounds. Concentrations below the quantitation limit and above the reporting limit really indicates that the compound was present, but the concentration is too uncertain to be of value. The GC technique used in this work uses a sorbent tube to collect C6 through C12 hydrocarbons, then thermally desorbs these compounds onto the GC column for separation. The larger compounds are not completely desorbed under the conditions used in this analysis, so that can place additional limitations on the quantitative determination of the concentrations of some of these compounds, since some of the compound collected during one time period will not be desorbed until the following sample is analyzed. This carryover of sample to a subsequent period was estimated by looking at data for a zero sample following a PAMS calibration sample. This data allows one to estimate the percent carryover of compounds to a subsequent period. The data for both undecane and dodecane suggests that the carryover is more than 50% so concentrations will not be reported for these compounds. The following table shows the reporting limits, quantitation limits and estimated percent carryover for each of the compounds identified in this work.

33 Report ID: 6203-Q Page 31 Reportable Compounds Reporting Quantitation Approximate # Name Limit Limit % carryover ppbv ppbv 1 2,2-Dimethylbutane <5% 2 n-hexane <5% 3 Methylcyclopentane & 2, <5% dimethylpentane 7 4 Benzene <5% 5 Cyclohexane <5% 6 2-Methylhexane & 2,3-dimethylpentane <5% 7 3-Methylhexane <5% 8 2,2,4-Trimethylpentane <5% 9 n-heptane <5% 10 Methylcyclohexane <5% 11 2,3,4-Trimethylpentane <5% 12 Toluene <5% 13 2-Methylheptane <5% 14 3-Methylheptane <5% 15 n-octane % 16 Ethylbenzene % 17 m & p-xylene % 18 Styrene % 19 o-xylene % 20 n-nonane % 21 Isopropylbenzene % 22 a-pinene nd 23 n-propylbenzene % 24 m-ethyltoluene % 25 p-ethyltoluene % 26 1,3,5-Trimethylbenzene % 27 o-ethyltoluene % 28 1,2,4-trimethybenzene % 29 n-decane % 30 1,2,3-Trimethylbenzene % 31 m-diethylbenzene % 32 p-diethylbenzene % 33 n-undecane 45% 7 Due to Methylcyclopentane & 2,4-dimethylpentane co-eluting the concentrations of the individual compounds became unavailable, therefore the compound concentrations must be reported as a sum of both compounds

34 Report ID: 6203-Q Page n-dodecane 45% To verify the stability of the GC, a span check was normally done at a 25-hour interval. The span check used a benzene permeation tube that emits benzene at a rate of 101 nanograms per minute, and was diluted to generate a gas concentration of approximately 55 ppb. The span check was followed by a zero check to minimize carryover of the high benzene concentration of benzene from the span check to the next ambient sample and to verify the desorption efficiency and check for contamination of the GC. If the results of the span check varied by more than ±15% from the average response that has been observed previously for more than two (2) consecutive days, a system retention time and response test was scheduled as soon as possible. Appropriate remedial action was taken if a problem was observed. A control chart showing the results of the span check for September, October, and November 2017 is shown below. The calculated concentration of benzene from the permeation tube was initially about 39 ppbv (through 10/25/17). The flow of dilution gas was reduced, increasing the benzene concentration to about 62 ppbv (from 10/26/17-11/10/17). A new permeation tube was installed, emitting benzene at a lower rate, having a benzene concentration about 24 ppbv (beginning on 11/10/17). For the zero checks, the benzene carryover from a preceding calibration or span check should be less than 1% of the concentration of the benzene in the span gas. If this zero check limit was exceeded on more than two (2) consecutive days, a system retention time and response test was scheduled as soon as possible. Appropriate remedial action was taken if a problem was observed. A control chart showing the results of the zero check for September, October, and November 2017 is shown as follows.

35 Report ID: 6203-Q Page 33 The zero and span checks are summarized below: Test Count Passed Percentage Span Check % Zero Check %

36 Report ID: 6203-Q Page 34 Signature Page Prepared and reviewed by: Patrick Clark, PE Montrose Air Quality Services, LLC Austin Heitmann Montrose Air Quality Services, LLC Additionally reviewed by: Michael Ogletree City and County of Denver

37 Appendix Quality Assurance Logs

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43 Calibration Certification Sheets

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48 Primary Flow Standard Certification Sheet

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