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Swansea Ambient Air Monitoring Station (SAMS)
Phase II 4th Quarter CY2018 Air Quality Data Report
Prepared for the Colorado Department of Transportation
and the City and County of Denver,
Department of Environmental Health
Montrose Project No. 043AS-122317
Report ID: 043AS-122317-Q4 2018
Test Dates: October 1-December 31 2018
January 31, 2018
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018
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 .......................................................................................................... 6
Figure 1a – Monthly PM10 Data .................................................................................................................. 6 Figure 1b – Monthly PM10 Data .................................................................................................................. 7 Figure 1c – Monthly PM10 Data .................................................................................................................. 8 Figure 2a – Monthly PM2.5 Data ................................................................................................................. 9 Figure 2b – Monthly PM2.5 Data ............................................................................................................... 10 Figure 2c – Monthly PM2.5 Data ............................................................................................................... 11 Figure 3a – Monthly NO2 Data ................................................................................................................. 12 Figure 3b – Monthly NO2 Data ................................................................................................................. 13 Figure 3c – Monthly NO2 Data ................................................................................................................. 14 Figure 4a – Monthly CO Data .................................................................................................................. 15 Figure 4b – Monthly CO Data .................................................................................................................. 16 Figure 4c – Monthly CO Data ................................................................................................................... 17 Figure 5a – Monthly Black Carbon Data .................................................................................................. 18 Figure 5b – Monthly Black Carbon Data .................................................................................................. 19 Figure 5c – Monthly Black Carbon Data .................................................................................................. 20 Table 1a – Monthly Summary of VOC Data .............................................................................................. 21 Table 1b – Monthly Summary of VOC Data .............................................................................................. 22 Table 1c – Monthly Summary of VOC Data .............................................................................................. 23 Table 2 – Reporting and Quantification Limits for Selected VOC Compounds ........................................ 23
DATA QUALITY ASSURANCE/QUALITY CONTROL ....................................................................... 24
Quality Assurance/Quality Control ........................................................................................................... 24 NOX and CO Analyzers - Span Test ....................................................................................................................... 24 NOX and CO Analyzers - Precision Test ................................................................................................................ 25 PM2.5 / PM10 Analyzer ............................................................................................................................................ 26 Aethalometer .......................................................................................................................................................... 26 Wind Speed and Wind Direction ........................................................................................................................... 26 Gas Chromatograph ............................................................................................................................................... 27
SIGNATURE PAGE ................................................................................................................................... 33
APPENDIX
Quality Assurance Logs Calibration Certification Sheets Primary Flow Standard Certification Sheet
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 1
Project Overview
Background
Colorado Department of Transportation (CDOT) and Denver Department of Public
Health and Environment (DDPHE) entered into an agreement1 to monitor air quality at
Swansea Elementary School in three phases. Phase I monitored 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, 2017. 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). Beginning in June 2018 the quarter system changed to reflect
common calendar quarters to prevent confusion about what time period a report is
covering. This Q4 2018 report was created to present the data collected during Phase II.
Objectives
Montrose Air Quality Services, LLC (Montrose) was contracted by the City and County
of Denver to start up and operate the SAMS. The SAMS is located at the Swansea
Elementary School; between the faculty parking lot and the playground; South East
Corner; at 4650 Columbine Street, Denver, Colorado. This report represents Q4 2018.
The station monitored the following parameters during Q4 2018:
• 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 DDPHE. 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 DDPHE became effective on August 12, 2016 and can be obtained
from CDOT by referencing routing number 17-HTD-ZH-00167.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 2
Operational Staff and Contacts
The contact information for each of the principal parties is summarized in the table
below:
Tim Buntrock Michael Ogletree
Colorado Department of Transportation City and County of Denver
3543 East 46th Avenue 200 W 14th Ave
Denver, CO 80216 Denver, CO 80204
Phone: (720) 920-4692 Phone: (720) 865-2891
E-mail: [email protected] E-mail: [email protected]
Patrick Clark, PE, QSTI Dr. Larry Anderson
Montrose Air Quality Services, LLC University of Colorado Denver
990 W. 43rd Ave. 7120 Routt Street
Denver, CO 80211 Arvada, CO 80004
Phone: (303) 670-0530 Phone: (303) 664-0757
E-mail: [email protected] E-mail: [email protected]
Austin Heitmann
Montrose Air Quality Services, LLC
990 W. 43rd Ave.
Denver, CO 80211
Phone: (303) 670-0530
E-mail: [email protected]
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 3
SAMS Site Description
Region: Denver
AQS ID: 080310023
Latitude: 39.78101
Longitude: -104.95545
Picture 1 – Location of SAMS in the Swansea Elementary School Parking Lot
Picture 2 – Interior of SAMS
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 4
SAMS Equipment
The list of primary equipment used in this project is shown in the table below. 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
PM2.5 / PM10 Minute GRIMM
Technologies Inc.
180 EDM
Meteorological measurements
(temperature, pressure, relative
humidity)
Minute GRIMM
Technologies Inc.
180 EDM
Meteorological measurements
(wind speed and wind
direction)
Minute RM Young 05305V
C6 through C12 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 Phase II Q4 CY2018 which is considered, October, November
and December.
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
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 5
of all data and calibrations have been uploaded to the Dropbox data room maintained by
DDPHE.
No pollutant NAAQS was exceeded during Q4 PY2018. Additionally, there were no
exceptional events, weather or otherwise, during the sampling period. 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.
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. On 10/14/18 the CO analyzer failed the daily calibration due to the internal
background of the instrument reaching its maximum allowed value and needing to be
reset. The CO data was considered invalid, and not included in this report, until the issue
was resolved on 10/24/18. On 11/11/18 the NO2 calibrations on the NOx analyzer began
drifting out of calibration, invalidating the data during the time the issue persisted. The
issue was attempted to be corrected multiple times in the field with manual calibrations
but the daily drift became too large to adjust for. The manufacturer was contacted on
11/28/18 to determine how to resolve the issue. Since the instrument is still under
warranty the manufacturer supplied replacement parts for the instrument that arrived
during Q1 2019.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 6
Pollutant Data Collected
Figure 1a – 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 micrograms per cubic meter (ug/m3) 24 hour ambient PM10
NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 7
Figure 1b – 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/m3 24 hour ambient PM10 NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 8
Figure 1c – Monthly PM10 Data
The graph below is shown for December and is the plot of the 24 hour averages. The
orange line represents the 150 ug/m3 24 hour ambient PM10 NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 9
Figure 2a – 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/m3 24 hour ambient PM2.5 NAAQS and the yellow line
represents the 12 ug/m3 one (1) year mean ambient PM2.5 NAAQS. Please note that the
24 hour average values cannot be directly compared to the annual mean NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 10
Figure 2b – 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/m3 24 hour ambient PM2.5 NAAQS and the yellow line
represents the 12 ug/m3 one (1) year mean ambient PM2.5 NAAQS. Please note that the
24 hour average values cannot be directly compared to the annual mean NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 11
Figure 2c – Monthly PM2.5 Data
The graph below is shown for December and is a plot of the 24 hour averages. The
orange line represents the 35 ug/m3 24 hour ambient PM2.5 NAAQS and the yellow line
represents the 12 ug/m3 one (1) year mean ambient PM2.5 NAAQS. Please note that the
24 hour average values cannot be directly compared to the annual mean NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 12
Figure 3a – 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 parts per billion (ppb) one (1) hour ambient NO2 NAAQS and the
yellow line represents the 53 ppb one (1) year mean ambient NO2 NAAQS. Please note
that the one (1) hour average values cannot be directly compared to the annual mean
NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 13
Figure 3b – 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 NAAQS and the yellow line
represents the 53 ppb one (1) year mean ambient NO2 NAAQS. Please note that the one
(1) hour average values cannot be directly compared to the annual mean NAAQS. No
valid NO2 data was collected from 11/11/18 through the end of the month for the reasons
described on page 5.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 14
Figure 3c – Monthly NO2 Data
The graph below is shown for December is a plot of the one (1) hour averages. The
orange line represents the 100 ppb one (1) hour ambient NO2 NAAQS and the yellow line
represents the 53 ppb one (1) year mean ambient NO2 NAAQS. Please note that the one
(1) hour average values cannot be directly compared to the annual mean NAAQS. No
valid NO2 data was collected during December 2018 for the reasons described on page 5.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 15
Figure 4a – 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 NAAQS and the
yellow line represents the 35 ppm one (1) hour ambient CO NAAQS. No valid CO data
was collected from 10/14/18 through 10/24/18 for the reasons described on page 5.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 16
Figure 4b – 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 NAAQS and the
yellow line represents the 35 ppm one (1) hour ambient CO NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 17
Figure 4c – Monthly CO Data
The graph below is shown for December and is a plot of the one (1) hour averages. The
orange line represents the nine (9) ppm eight (8) hour ambient CO NAAQS and the
yellow line represents the 35 ppm one (1) hour ambient CO NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 18
Figure 5a – Monthly Black Carbon Data
The graph below is shown for October and plots the 24 hour averages. Black Carbon
does not have a NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 19
Figure 5b – Monthly Black Carbon Data
The graph below is shown for November and plots the 24 hour averages. Black Carbon
does not have a NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 20
Figure 5c – Monthly Black Carbon Data
The graph below is shown for December and plots the 24 hour averages. Black Carbon
does not have a NAAQS.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 21
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 DDPHE. 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 October and averages 30 minute runs. None of the
compounds reported have a NAAQS.
Compound
Average
Result for
October
(ppb)
Total
Number
of Data
Points
Number
Above
QL2
Number
Between
RL and
QL
Number
Below RL
N-Hexane 0.407 1428 893 309 226
N-Heptane 0.129 1428 298 225 905
N-Octane 0.0919 1428 136 189 1103
Benzene 0.193 1428 431 305 692
Toluene 0.640 1428 912 274 242
Ethylbenzene 0.102 1428 134 275 1019
m,p-Xylene 0.298 1428 398 392 638
o-Xylene 0.132 1428 68 131 1229
2 Quantification Limit (QL)
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 22
Table 1b – 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.
Compound
Average
Result for
November
(ppb)
Total
Number
of Data
Points
Number
Above
QL3
Number
Between
RL and
QL
Number
Below RL
N-Hexane 0.449 1382 871 281 230
N-Heptane 0.157 1382 345 269 768
N-Octane 0.101 1382 154 222 1006
Benzene 0.250 1382 529 332 521
Toluene 0.721 1382 956 187 239
Ethylbenzene 0.122 1382 155 299 928
m,p-Xylene 0.368 1382 441 397 544
o-Xylene 0.147 1382 79 147 1156
3 Quantification Limit (QL)
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 23
Table 1c – Monthly Summary of VOC Data
The table below is shown for December and averages 30 minute runs. None of the
compounds reported have a NAAQS.
Compound
Average
Result for
December
(ppb)
Total
Number
of Data
Points
Number
Above
QL4
Number
Between
RL and
QL
Number
Below RL
N-Hexane 0.517 1398 1008 269 121
N-Heptane 0.177 1398 347 304 747
N-Octane 0.140 1398 185 251 962
Benzene 0.287 1398 639 324 435
Toluene 0.803 1398 1021 157 220
Ethylbenzene 0.131 1398 191 341 866
m,p-Xylene 0.413 1398 534 392 472
o-Xylene 0.156 1398 109 163 1126
Table 2 – Reporting and Quantification Limits for Selected VOC Compounds
The RLs and QLs for the selected compounds is shown in the table below:
Compound
Reporting
Limit
(ppb)
Quantification
Limit (ppb)
N-Hexane 0.1 0.2
N-Heptane 0.1 0.2
N-Octane 0.1 0.2
Benzene 0.1 0.2
Toluene 0.1 0.2
Ethylbenzene 0.1 0.25
m,p-Xylene 0.15 0.35
o-Xylene 0.2 0.35
4 Quantification Limit (QL)
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 24
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:
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 25
Parameter Span Count Span Passed Span Percentage
Nitrogen Oxide 46 46 100
Nitrogen Dioxide 46 15 32.6
Carbon Monoxide 46 43 93.5
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, 1.5 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
Precision
Percentage
Nitrogen Oxide 46 46 100
Nitrogen Dioxide 46 13 28.3
Carbon Monoxide 46 32 69.6
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 26
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 2oC, 5%, and 10 mmHg,
respectively. A summary of the weekly and biweekly checks is summarized below.
Test Count Passed Percentage
Zero Check 5 5 100%
Flow Check 5 5 100%
Temperature Check 7 7 100%
Pressure Check 7 7 100%
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 3 3 100%
Leak Check 3 3 100%
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.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 27
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.
Test Count Passed Percentage
Wind Speed Check 3 3 100%
Wind Direction Check 3 3 100%
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 PAMS 5-point calibration of the GC was conducted on December 6, 2018. All
collected raw data was then post-processed to provide valid data in this report to. 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.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 28
Due to the lack of availability of a PAMS calibration mixture the PAMS calibration had
to be delayed until 12-6-18. Since the instrument was shut down and moved since the
previous calibrations, it was decided to wait until a new PAMS calibration could be
performed to process this data set. The new PAMS gas mixture provided sufficient
justification to change response factors for some of the compounds identified, including
benzene and toluene. The Base Sensitivity used in these analyses was selected to balance
results from both the PAMS calibrations, and the daily PERM calibration checks. The
regression results from this PAMS calibration are similar to previous results with the
measured benzene being about 89% of the PAMS calibration. The measured benzene
from the daily PERM measurements are about 120% of those expected from the
calculated benzene in the permeation samples.
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.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 29
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
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.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 30
Reportable Compounds
Reporting Quantitation Approximate
# Name Limit Limit % carryover ppbv ppbv
1 2,2-Dimethylbutane 0.1 0.2 <5%
2 n-Hexane 0.1 0.2 <5%
3 Methylcyclopentane & 2,4-
dimethylpentane5
0.1 0.25 <5%
4 Benzene 0.1 0.2 <5%
5 Cyclohexane 0.25 0.75 <5%
6 2-Methylhexane & 2,3-dimethylpentane 0.2 0.5 <5%
7 3-Methylhexane 0.1 0.2 <5%
8 2,2,4-Trimethylpentane 0.1 0.2 <5%
9 n-Heptane 0.1 0.2 <5%
10 Methylcyclohexane 0.1 0.2 <5%
11 2,3,4-Trimethylpentane 0.1 0.2 <5%
12 Toluene 0.1 0.2 <5%
13 2-Methylheptane 0.1 0.2 <5%
14 3-Methylheptane 0.1 0.2 <5%
15 n-Octane 0.1 0.2 5%
16 Ethylbenzene 0.1 0.25 10%
17 m & p-Xylene 0.15 0.35 10%
18 Styrene 0.2 0.5 15%
19 o-Xylene 0.2 0.35 10%
20 n-Nonane 0.1 0.2 10%
21 Isopropylbenzene 0.1 0.2 10%
22 a-Pinene 0.2 0.4 nd
23 n-Propylbenzene 0.15 0.35 15%
24 m-Ethyltoluene 0.3 1 15%
25 p-Ethyltoluene 0.2 0.65 15%
26 1,3,5-Trimethylbenzene 0.2 0.5 15%
27 o-Ethyltoluene 0.2 0.5 15%
28 1,2,4-trimethybenzene 0.25 0.75 20%
29 n-Decane 0.3 0.85 20%
30 1,2,3-Trimethylbenzene 0.3 0.85 20%
31 m-Diethylbenzene 0.3 0.9 20%
32 p-Diethylbenzene 0.4 1.3 25%
33 n-Undecane
45%
34 n-Dodecane
45%
5 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
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 31
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
35 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 Q4 2018 is shown below.
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 Q4 2018 is shown as follows.
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 32
The zero and span checks are summarized below:
Test Count Passed Percentage
Span Check 88 88 100%
Zero Check 88 88 100%
City and County of Denver
Report ID: 043AS-122317-Phase II Q4 2018 Page 33
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
Appendix
Quality Assurance Logs
Calibration Certification Sheets
Primary Flow Standard Certification Sheet