EPA-600/R-05/042 

April 2005 

Evaluation of a Former 

Landfill Site in Fort 

Collins, Colorado Using 

Ground-Based Optical 

Remote Sensing 

Technology 

EPA-600/R-05/042 

April 2005 

Evaluation of a Former Landfill Site in

Fort Collins, Colorado Using

Ground-Based Optical Remote

Sensing Technology

by

Mark Modrak

Ram A. Hashmonay

Ravi Varma

Robert Kagann

ARCADIS G&M, Inc.

4915 Prospectus Dr., Suite F

Durham, NC 27713

Contract Number: 68-C99-201

Work Assignment Number: 0-25

EPA Project Officer: Susan Thorneloe

U.S. Environmental Protection Agency

Air Pollution Prevention and Control Division

Research Triangle Park, NC 27711

U.S. Environmental Protection Agency

Office of Research and Development

Washingtion, DC 20460
Abstract 

A former landfill site in Fort Collins, Colorado is being assessed for landfill gas emissions as 

part of an effort under the city’s Brownfields program to support reuse options for the property. 

Before initiating any additional development at the property, the city requested assistance from 

the EPA Region 8 Office, and the Office of Superfund Remediation and Technology 

Innovation, Technology Integration and Information Branch to perform a site assessment to 

search for the presence of any fugitive gas emissions from the former landfill site. This 

assessment was necessary due to the potential adverse health effects associated with exposure 

to landfill gas. 

The focus of this study was to evaluate fugitive emissions of methane and VOCs at the site, in 

support of the reuse objectives, using a scanning open-path Fourier transform infrared 

spectrometer, open-path tunable diode laser absorption spectroscopy, and an ultra-violet 

differential optical absorption spectrometer. The study involved a technique developed through 

research funded by the EPA National Risk Management Research Laboratory that uses 

ground-based optical remote sensing technology, known as optical remote sensing-radial plume 

mapping. The horizontal radial plume mapping method was used to map surface concentrations, 

and the vertical radial plume mapping (VRPM) method was used to measure emissions fluxes 

downwind of the site. 

The study did not detect the presence of any surface methane hot spots at the site. The highest 

methane concentrations detected at the site were only slightly above ambient background levels. 

However, the survey detected the presence of a gasoline hot spot (average concentration over 

81 ppb, with a maximum concentration of about 100 ppb) located in the vicinity of a 

recreational building at the site. The VRPM survey of the site detected methane, ammonia, and 

gasoline along a downwind configuration at the site. The average calculated gasoline flux from 

the VRPM survey was 0.87 g/s. The measured methane and ammonia concentrations were 

well-correlated, indicating that the measured concentrations probably came from the same 

source. Wind data collected indicated that the source of the methane and ammonia detected is 

located across a river adjacent to the site. 

ii 
Foreword 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting 

the Nation’s land, air, and water resources. Under a mandate of national environmental laws, 

the Agency strives to formulate and implement actions leading to a compatible balance 

between human activities and the ability of natural systems to support and nurture life. To meet 

this mandate, EPA’s research program is providing data and technical support for solving 

environmental problems today and building a science knowledge base necessary to manage 

our ecological resources wisely, understand how pollutants affect our health, and prevent or 

reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for 

investigation of technological and management approaches for preventing and reducing risks 

from pollution that threaten human health and the environment. The focus of the Laboratory’s 

research program is on methods and their cost-effectiveness for prevention and control of 

pollution to air, land, water, and subsurface resources; protection of water quality in public 

water systems; remediation of contaminated sites, sediments and ground water; prevention 

and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with 

both public and private sector partners to foster technologies that reduce the cost of 

compliance and to anticipate emerging problems. NRMRL’s research provides solutions to 

environmental problems by: developing and promoting technologies that protect and improve 

the environment; advancing scientific and engineering information to support regulatory and 

policy decisions; and providing the technical support and information transfer to ensure 

implementation of environmental regulations and strategies at the national, state, and 

community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research 

plan. It is published and made available by EPA’s Office of Research and Development to 

assist the user community and to link researchers with their clients. 

Sally Gutierrez, Acting Director 

National Risk Management Research Laboratory 

iii 
EPA Review Notice 

This report has been peer and administratively reviewed by the U.S. Environmental 

Protection Agency and approved for publication. Mention of trade names or commercial 

products does not constitute endorsement or recommendation for use. 

This document is available to the public through the National Technical Information 

Service, Springfield, Virginia 22161. 

iv 
Contents 

Section Page 

Abstract ................................................................. ii

List of Tables ........................................................... vii

List of Figures .......................................................... viii

Acknowledgements ....................................................... ix

Executive Summary ....................................................... x

1 Project Description and Objectives ...................................... 1-1

1.1 Background .................................................... 1-1

1.2 Project Description/Purpose ....................................... 1-3

1.2.1 Horizontal RPM ............................................ 1-4

1.2.2 Vertical RPM .............................................. 1-5

1.3 Quality Objectives and Criteria ..................................... 1-5

1.4 Project Schedule ................................................ 1-7

2 Test Procedures ...................................................... 2-1

2.1 Area A ........................................................ 2-2

2.2 Area B ........................................................ 2-2

2.3 Area C ........................................................ 2-2

2.4 Area D ........................................................ 2-3

2.5 VRPM Measurements ............................................ 2-3

2.6 OP-TDLAS Measurements ........................................ 2-3

2.7 UV-DOAS Measurements ......................................... 2-4

3 Results and Discussion ................................................ 3-1

3.1 Area A ........................................................ 3-1

3.1.1 HRPM Results ............................................. 3-1

3.1.2 VRPM Results ............................................. 3-3

3.1.3 UV-DOAS Results .......................................... 3-5

3.1.4 Summary of Results from Area A .............................. 3-5

3.2 Areas B, C, and D ............................................... 3-5

3.3 OP-TDLAS Measurements ........................................ 3-6

4 Conclusion ......................................................... 4-1

5 QA/QC ............................................................ 5-1

5.1 Equipment Calibration ............................................ 5-1

5.2 Assessment of DQI Goals ......................................... 5-1

5.2.1 DQI Check for Analyte PIC Measurement ........................ 5-1

5.2.2 DQI Checks for Ambient Wind Speed and Wind Direction

Measurements .............................................. 5-2

v 
Contents (continued) 

Section Page 

5.2.3 DQI Check for Precision and Accuracy of Theodolite

Measurements ............................................. 5-3

5.3 QC Checks of OP-FTIR Instrument Performance ...................... 5-3

5.4 Validation of Concentration Data Collected with the OP-FTIR ............ 5-4

5.5 Internal Audit of Data Input Files ................................... 5-4

5.6 OP-TDLAS Instrument ........................................... 5-5

5.7 UV-DOAS Instrument ........................................... 5-5

6 References ......................................................... 6-1

Appendix A: OP-FTIR Mirror Coordinates ................................... A-1

Appendix B: OP-TDLAS Configuration Path Length Distances .................. B-1

Appendix C: Methane Concentrations ....................................... C-1

vi 
List of Tables

Table Page 

1-1 Summary Information on the ORS Instrumentation Used in the Study ......... 1-4

1-2 Detection Limits for Target Compounds ................................. 1-6

1-3 Schedule of Work Performed at the Site ................................. 1-7

3-1 Average Methane Concentrations Measured During the HRPM Survey of

Area A ........................................................... 3-1

3-2 Average Concentration of BTX Compounds Measured by the UV-DOAS

Instrument ........................................................ 3-5

3-3 Average Methane Concentrations Found during the HRPM Surveys of

Areas B, C, and D .................................................. 3-7

3-4 Comparison of Methane Concentrations Measured with the OP-TDLAS

and OP-FTIR Instruments ............................................ 3-8

5-1 Instrumentation Calibration Frequency and Description ..................... 5-1

5-2 DQI Goals for Instrumentation ........................................ 5-2

A-1 Standard Distance and Horizontal Coordinates of Mirrors Used in the

HRPM Survey of Area A ............................................. A-1

A-2 Standard Distance and Horizontal Coordinates of Mirrors Used in the

HRPM Survey of Area B ............................................. A-1

A-3 Standard Distance and Horizontal Coordinates of Mirrors Used in the

HRPM Survey of Area C ............................................. A-1

A-4 Standard Distance, and Horizontal Coordinates of Mirrors Used in the

HRPM Survey of Area D ............................................. A-1

A-5 Standard Distance, and Horizontal and Vertical Coordinates of Mirrors

Used in the VRPM Survey ........................................... A-2

B-1 Standard Distance of Path Lengths Used in OP-TDLAS Configurations ........ B-1

C-1 Methane Concentrations Found during the Area A HRPM Survey ............ C-1

C-2 Methane Concentrations Found during the Area B HRPM Survey ............ C-2

C-3 Methane Concentrations Found during the Area C HRPM Survey ............ C-2

C-4 Methane Concentrations Found during the Area D HRPM Survey ............ C-3

C-5 Methane Concentrations Found during the Downwind VRPM Survey Run 1 .... C-4

C-6. Methane Concentrations Found during the Downwind VRPM Survey Run 2 .... C-5

vii 
List of Figures 

Figure Page 

E-1 Map of the Ft. Collins Site Detailing the Location of the HRPM Survey Areas .... xi

E-2 Map of the Ft. Collins Site Detailing the Location of the VRPM Configurations. . . xi

1-1 Map of the Ft. Collins Site Detailing the Location of the HRPM Survey Areas . . 1-2

1-2 Map of the Ft. Collins Site Detailing the Location of the VRPM Configurations . 1-2

1-3 Example of a HRPM Configuration .................................... 1-5

1-4 Example of a VRPM Configuration .................................... 1-5

2-1 Schematic of the HRPM Configuration Used in Area A .................... 2-2

2-2 Partial Picture of the HRPM Configuration Used in Area A ................. 2-2

2-3 Partial Picture of the HRPM Configuration Used in Area B ................. 2-3

2-4 Partial Picture of the HRPM Configuration Used in Area C ................. 2-3

2-5 Partial Picture of the HRPM Configuration Used in Area D ................. 2-3

2-6 Partial Picture of the VRPM Configuration Used at the Site ................. 2-4

2-7 OP-TDLAS System ................................................ 2-4

2-8 UV-DOAS Instrument .............................................. 2-4

3-1 Reconstructed Gasoline Surface Concentrations in Area A .................. 3-2

3-2 Time Series of Wind Direction and Concentrations of Methane and Ammonia

Concentrations Measured on Beam Path #5 of the VRPM Downwind Survey . . . 3-3

3-3 Reconstructed Gasoline Plume Map from the Downwind VRPM Survey ....... 3-4

3-4 Gasoline, Methane, and Ammonia Fluxes Measured During the Downwind

VRPM Survey ..................................................... 3-4

3-5 Time Series of Path-Averaged Concentrations of Benzene, Toluene, and p-Xylene

Measured with the UV-DOAS Instrument and Gasoline Measured with the 

OP-FTIR in Area A ................................................. 3-5

3-6 Results Summary Map from Area A Measurements ....................... 3-6

3-7 Time Series of Methanol Concentrations Measured along Beam Path #3 of the

Area B HRPM Survey .............................................. 3-7

5-1 Comparison of a Spectrum Measured at the Site (Green Trace) to Reference

Spectra of Gasoline (Red Trace) ....................................... 5-4

5-2 Comparison of a Spectrum Measured at the Site (Blue Trace) to Reference

Spectra of Ammonia (Red Trace) ...................................... 5-4

5-3 Post-Fort Collins Comparison of Methane Concentrations Measured with the

OP-TDLAS and OP FTIR Instruments .................................. 5-5

viii 
Acknowledgments 

This study was jointly sponsored by the United States Environmental Protection Agency (EPA) 

Region 8 Office, and the Office of Superfund Remediation and Technology Innovation, 

Technology Integration and Information Branch under its Monitoring and Measurement for the 

21st Century (21M2) initiative. The 21M2 initiative is intended to provide EPA staff with 

resources to apply new approaches to real site problems. 

ix 
Executive Summary 

Background and Site Information

A former landfill site in Fort Collins, Colorado is being assessed for landfill gas emissions as 

part of an effort under the city’s Brownfields program to support reuse options for the property. 

The city of Fort Collins is interested in developing a larger recreation facility on this property, 

which is already being used primarily for recreational purposes. Before initiating any additional 

development at the property, the city requested assistance from EPA to perform a site 

assessment to search for the presence of any fugitive gas emissions from the former landfill site. 

This assessment was necessary due to the potential adverse health effects associated with 

exposure to landfill gas. The EPA Region 8 Office requested assistance with this study through 

the Monitoring and Measurement for the 21st Century program to utilize innovative approaches 

for performing an assessment at the site. 

The focus of this study was to evaluate emissions of fugitive gases and VOCs at the site, in 

support of the reuse objectives, using an open-path Fourier transform infrared (OP-FTIR) 

spectrometer, open-path tunable diode laser absorption spectroscopy (OP-TDLAS), and an 

ultra-violet differential optical absorption spectrometer (UV-DOAS). The OP-FTIR instrument 

provided the critical measurements in the current study, and the OP-TDLAS and UV-DOAS 

provided noncritical, supplemental data. The study involved a technique developed through 

research funded by the EPA National Risk Management Research Laboratory (NRMRL) that 

uses ground-based optical remote sensing technology, known as optical remote sensing-radial 

plume mapping (ORS-RPM) (Hashmonay and Yost, 1999; Hashmonay et al., 1999; Wu et al., 

1999; Hashmonay et al., 2001; Hashmonay et al., 2002). 

The study consisted of one field campaign performed during September 2003 by ARCADIS and 

EPA personnel. Figure E-1 presents the overall layout of the site, detailing the geographic 

location of each horizontal radial plume mapping (HRPM) survey area. Figure E-2 shows the 

location of the vertical radial plume mapping (VRPM) configurations, which were used to 

collect data for emission flux calculations. 

Testing Procedures

HRPM surveys were done in Areas A, B, C, and D to search for surface emissions hot spots. 

A VRPM survey was done in Area A to measure emissions of fugitive gases and VOCs upwind 

and downwind of the area. The OP-TDLAS instrument was deployed in each area of the site 

to provide additional information on methane concentrations at the site. The UV-DOAS 

instrument was deployed in Area A to provide information on concentrations of benzene, 

toluene, and xylenes (BTX) at the site. 

x 
Figure E-1. Map of the Ft. Collins Site Detailing the 

Location of the HRPM Survey Areas. 

Figure E-2. Map of the Ft. Collins Site Detailing the 

Location of the VRPM Configurations. 

xi 
Results and Discussion 

Area A 

HRPM and VRPM Results 

The HRPM survey of Area A did not detect the presence of any methane hot spots. However, 

the survey detected the presence of a gasoline hot spot (average concentration over 81 ppb, with 

a maximum concentration of about 100 ppb) located in the southern corner of Area A. 

The VRPM survey of the site detected methane, ammonia, and gasoline on the downwind 

VRPM configuration (see Figure E-2). The average calculated gasoline flux from the VRPM 

survey was 0.87 g/s. The measured methane and ammonia concentrations were well-correlated, 

indicating that the measured concentrations probably came from the same source. Wind data 

collected indicate that the source of the methane and ammonia detected is located outside of 

Area A, across the river adjacent to the site. This is supported by the fact that methane and 

ammonia were not detected during the HRPM survey of Area A. 

UV-DOAS Results 

The UV-DOAS instrument was set up along the surface, approximately parallel to the 

downwind VRPM configuration in Area A. The UV-DOAS instrument found average 

concentrations of 2.6 ppb for benzene, 21 ppb for toluene, and 4.9 ppb for p-xylene. The toluene 

concentrations measured with the UV-DOAS correlated well with the gasoline concentrations 

measured with the OP-FTIR, indicating that the detected gasoline plume contained BTX 

compounds. 

Areas B, C, and D 

HRPM surveys did not detect any methane hot spots in Areas B, C, and D. The average surface 

methane concentrations in these areas were close to ambient background levels. The HRPM 

survey of Area B detected a small methanol hot spot. The average methanol concentration 

measured in this area was 20.9 ppb, with a range of 0 to 127 ppb. 

OP-TDLAS Measurements 

The OP-TDLAS measured methane concentrations in Areas A, B, C, and D. The configurations 

used by the OP-TDLAS in these areas were often similar to the configurations used with the 

OP-FTIR instruments. The methane concentrations measured by the OP-TDLAS were only 

slightly above ambient background levels, reinforcing the findings of the HRPM surveys. The 

methane concentrations measured with the OP-TDLAS were almost always slightly higher than 

concentrations measured with the OP-FTIR along similar optical paths. 

xii 
Chapter 1

Project Description and Objectives

1.1 Background

As part of its Brownfields redevelopment effort, the 

city of Ft. Collins, Colorado, with assistance from the 

United States Environmental Protection Agency 

(EPA) Region 8 Office, is assessing a former landfill 

site for gas emissions. The property, which is approximately 19 acres in size, is composed of a commercial 

area, a park, playgrounds, soccer fields, and bike 

paths. The site is bounded on the northeast by the 

Cache La Poudre River. The City of Fort Collins is 

interested in developing a larger recreation facility at 

the site and is receiving assistance from EPA Region 

8 under the Targeted Brownfields Assessment program to perform an assessment at the site. As part of 

the 21M2 (Monitoring and Measurement Technologies for the 21st Century) initiative, the EPA Office 

of Superfund Remediation and Technology Innovation provided support to EPA Region 8 for this study. 

The site encompasses a landfill approximately 5 acres 

in size. Little information is known about the contents of the landfill, or when the landfill opened. The 

landfill was operated by the City of Fort Collins and 

was closed in the early 1960s. After the landfill was 

closed, the site was covered with a clay cap, ranging 

in depth from one to three feet. A manufactured gas 

plant operated adjacent to the site for approximately 

30 years. The plant operated until around 1930, and 

produced gas from coal and, possibly, oil. 

The focus of this study was to evaluate emissions of 

fugitive gases and VOCs at the site using an openpath Fourier transform infrared (OP-FTIR) spectrometer, open-path tunable diode laser absorption spectroscopy (OP-TDLAS), and an ultra-violet differential optical absorption spectrometer (UV-DOAS). The 

OP-FTIR instrument provided the critical measurements in the current study. The OP-TDLAS and 

UV-DOAS provided noncritical, supplemental data. 

The study involved a technique developed through 

research funded by EPA’s National Risk Management Research Laboratory (NRMRL) that uses 

ground-based optical remote sensing technology, 

known as optical remote sensing-radial plume mapping (ORS-RPM) (Hashmonay and Yost, 1999; 

Hashmonay et al., 1999; Wu et al., 1999; Hashmonay 

et al., 2001; Hashmonay et al., 2002). The effort 

identified emission hot spots (areas of relatively 

higher emissions), investigated source homogeneity, 

and calculated an emission flux rate for each compound detected at the site. Concentration maps in the 

horizontal and downwind vertical planes were generated using the horizontal radial plume mapping 

(HRPM), and vertical plume mapping (VRPM) 

methods, respectively. 

The study consisted of one field campaign performed 

during September 2003 by ARCADIS and EPA 

personnel. The Fort Collins site was divided into four 

survey areas. Figure 1-1 presents the overall layout of 

the site, detailing the geographic location of each 

HRPM survey area. The red dots denote the location 

of the OP-FTIR used in each configuration. Figure 

1-2 shows the location of the VRPM configurations 

that were used to collect data for emission flux 

calculations. The red square indicates the location of 

the scissors jack (vertical structure) used in each 

VRPM configuration. 

1-1
Evaluation of Fugitive Emissions at a 

Figure 1-1. Map of the Ft. Collins Site Detailing the 

Location of the HRPM Survey Areas. 

Figure 1-2. Map of the Ft. Collins Site Detailing the 

Location of the VRPM Configurations. 

1-2
Brownfield Landfill in Ft. Collins, Colorado 

1.2 Project Description/Purpose

The objectives of the study were to 

• Collect OP-FTIR data in order to identify 

major emissions hot spots at the Ft. Collins, 

CO landfill by generating surface concentration maps in the horizontal plane, 

• Measure emission fluxes of detectable compounds downwind from major hot spots, and 

• Demonstrate the operation and function of the 

various ORS technologies 

The ORS techniques used in this study were designed 

to characterize the emissions of fugitive gases from 

area sources. Detailed spatial information is obtained 

from path-integrated ORS measurements by the use 

of iterative algorithms. The HRPM method involves 

the use of a configuration of nonoverlapping radial 

beam geometry to map the concentration distributions 

in a horizontal plane. This method can also be applied 

to a vertical plane downwind from an area emission 

source to map the crosswind and vertical profiles of 

a plume. By incorporating wind information, the flux 

through the plane can be calculated, which leads to 

the emission rate of the upwind area source. An 

OP-FTIR sensor was chosen as the primary instrument for the study because of its capability of accurately measuring a large number of chemical species 

that might occur in a plume. 

The OP-FTIR Spectrometer combined with the 

ORS-RPM method is designed for both fence-line 

monitoring applications, and real-time, on-site, 

remediation monitoring and source characterization. 

An infrared light beam, modulated by a Michelson 

interferometer is transmitted from a single telescope 

to a retroreflector (mirror) target that is usually 100 to 

500 meters from the telescope. The returned light 

signal is received by the single telescope and directed 

to a detector. Some of the light is absorbed by the 

molecules in the beam path as the light propagates to 

the mirror, and more is absorbed as the light is 

reflected back to the analyzer. Thus, the round-trip 

path of the light doubles the chemical absorption 

signal. One advantage of OP-FTIR monitoring is that 

the concentrations of a multitude of infrared absorbing gaseous chemicals can be detected and measured 

simultaneously, with high temporal resolution. 

The OP-TDLAS system (Unisearch Associates, Inc.) 

is a fast, interference-free technique for making 

continuous concentration measurements of many 

gases. The OP-TDLAS used in the current study is 

capable of measuring concentrations of gases such as 

carbon monoxide (CO), carbon dioxide (CO2), 

ammonia (NH3), and methane (CH4) in the range of 

tens of parts per billion over an open path up to 1 km. 

The laser emits radiation at a particular wavelength 

when an electrical current is passed through it. The 

light wavelength depends on the current and therefore 

allows scanning over an absorption feature and 

analyzing the target gas concentration using Beer’s 

law. The OP-TDLAS used in this study is a multiple 

channel TDL instrument that allows fast scanning 

electronically (few seconds) among many beam-paths 

(presently 8 beams). The OP-TDLAS utilizes a small 

4-inch telescope, which directs the laser beam to a 

mirror. The laser beam is returned by the mirror to 

the telescope, which is connected with fiber optics to 

a control box that houses the laser and a multiple 

channel detection device. For this particular field 

campaign, data from the OP-TDLAS were used to 

provide additional information on methane concentrations at the site. At the time of the field campaign, the 

OP-TDLAS system had only recently been acquired 

by EPA. Consequently, standard operating and 

calibration procedures were still being developed. 

The UV-DOAS AR500 instrument (OPSIS, Inc.) has 

proven to be particularly useful for determining the 

concentration of unstable species like free radicals or 

nitrous acid. Additionally, many of the aromatic 

species can be determined at high sensitivity (Platt, 

1994). For the current field campaign, the UV-DOAS 

instrument was deployed in a bistatic configuration 

(the UV source and detector on opposite ends of the 

optical path). This project is the first time the UVDOAS instrument has been deployed by this group 

for data collection. For this particular field campaign, 

data from the UV-DOAS instrument were used to 

provide additional information on benzene, toluene, 

1-3
Table 1-1. Summary Information on the ORS Instrumentation Used in the Study. 

Property OP-FTIR OP-TDLAS UV-DOAS 

Wavelength Range Infrared (2-20 μm) Near Infrared (approx. 1.5 Ultraviolet (245-380 

μm) nm) 

Target Analytes Methane, ammonia, gasoline, 

VOCs 

Methane Benzene, toluene, xylene 

Detection Limits Parts per billion Parts per billion Parts per billion 

Limiting Weather Heavy rain Heavy rain, fog Heavy rain, fog 

Conditions 

Interfering Species Carbon dioxide, water None Oxygen, ozone 

Evaluation of Fugitive Emissions at a 

and xylenes (BTX) concentrations. The UV-DOAS 

instrument was used for BTX measurements because 

it has a much lower minimum detection limit (MDL) 

than the OP-FTIR for these compounds. Although the 

strong, structured UV absorption features of monocyclic aromatic hydrocarbons (i.e., BTX) have been 

known for a long time, it only recently became 

possible to use these properties for the reliable, sensitive, and selective measurement of these compounds 

by UV-DOAS. UV-DOAS measurements of BTX 

and trace gases can be an extremely valuable complement to more traditional techniques like OP-FTIR. 

Table 1-1 presents summary information on the ORS 

instrumentation used in this study. The table lists the 

analytes measured by each instrument during the 

current study and instrument limitations such as 

weather and interfering species. 

Meteorological and survey measurements were also 

made during the field campaign. A theodolite was 

used to make the survey measurement of the azimuth 

and elevation angles and the radial distances to the 

mirrors, relative to the OP-FTIR sensor. 

1.2.1 Horizontal RPM 

The HRPM approach provides spatial information to 

path-integrated measurements acquired in a horizontal plane by an ORS system. This technique yields 

information on the two-dimensional distribution of 

the concentrations in the form of chemical concentration contour maps. This form of output readily 

identifies chemical “hot spots,” the locations of high 

emissions. This method can be of great benefit for 

performing site surveys before, during, and after site 

remediation activities. 

HRPM scanning is usually performed with the ORS 

beams located as close to the ground as is practical. 

This enhances the ability to detect minor constituents 

emitted from the ground, since the emitted plumes 

dilute significantly at higher elevations. The survey 

area is typically divided into a Cartesian grid of n

times m rectangular cells. In some unique cases, the 

survey area may not be rectangular due to obstructions, and the shape of the cells may be slightly 

altered accordingly. A mirror is located in each of 

these cells, and the ORS sensor scans to each of these 

mirrors, dwelling on each for a set measurement time 

(30 seconds in the present study). The system scans 

to the mirrors in the order of either increasing or 

decreasing azimuth angle. The path-integrated concentrations measured at each mirror are averaged 

over several scanning cycles to produce maps of 

time-averaged concentrations. Meteorological measurements are made concurrent to the scanning 

measurements. 

Figure 1-3 represents a typical HRPM configuration. 

In this particular case, n = m = 3. The solid lines 

represent the nine optical paths, each terminating at 

a mirror. 

1-4
Brownfield Landfill in Ft. Collins, Colorado 

One OP-FTIR instrument (manufactured by Unisearch Associates) was used to collect Horizontal 

RPM data during the field campaign. 

Figure 1-3. Example of a HRPM Configuration. 

1.2.2 Vertical RPM 

The VRPM method maps the concentrations in the 

vertical plane by scanning the ORS system in a 

vertical plane downwind from an area source. One 

can obtain the plane-integrated concentration from 

the reconstructed concentration maps. The flux is 

calculated by multiplying the plane-integrated concentration by the wind speed component perpendicular to the vertical plane. Thus, the VRPM method 

leads to a direct measurement-based determination of 

the upwind source emission rate (Hashmonay et al., 

1998; Hashmonay and Yost, 1999, Hashmonay et al., 

2001). 

Figure 1-4 shows a schematic of the experimental 

setup used for vertical scanning. Several mirrors are 

placed in various locations on a vertical plane in-line 

with the scanning OP FTIR. A vertical platform 

(scissors jack) is used to place two of the mirrors at a 

predetermined height above the surface. The location 

of the vertical plane is selected so that it intersects the 

mean wind direction as close to perpendicular as 

practical. 

Figure 1-4. Example of a VRPM Configuration. 

Two OP-FTIR instruments (manufactured by Unisearch Associates and IMACC, Inc.) were used to 

create two vertical planes, one upwind and one 

downwind of the source area. This configuration 

made it possible to calculate an upwind emission flux 

from the upwind vertical plane measurements, and a 

downwind emission flux from the downwind vertical 

plane measurements. More information on the configurations used in this study can be found in Section 2 

of this report. 

1.3 Quality Objectives and Criteria

Data quality objectives (DQOs) are qualitative and 

quantitative statements developed using EPA’s DQO 

Process (EPA 2000) that clarify study objectives, 

define the appropriate type of data, and specify 

tolerable levels of potential decision errors that will 

be used as the basis for establishing the quality and 

quantity of data needed to support decisions. DQOs 

1-5
Table 1-2. Detection Limits for Target Compounds. 

OP-FTIR Estimated Detection AP-42 Value ratioed to an 

Limit for Path Length = 100m, Compound 1 min Average 

average methane concentration of 50 ppma 

(ppmv) (ppmv) 

1,4-Dichlorobenzene 0.012 0.000021 

2-Propanol 0.0060 0.0050 

Acetone 0.024 0.00070 

Acrylonitrile 0.010 0.00063 

Butane 0.0060 0.00050 

Chlorobenzene 0.040 0.000025 

Chloroform 0.012 0.0000030 

Chloromethane 0.012 0.00010 

Dichlorodifluoromethane 0.0040 0.0016 

Dimethyl sulfide 0.018 0.00078 

Ethane 0.010 0.089 

Ethanol 0.0060 0.0027 

Ethyl benzene 0.060 0.00046 

Ethyl chloride 0.0040 0.00013 

Evaluation of Fugitive Emissions at a 

define the performance criteria that limit the probabilities of making decision errors by considering the 

purpose of collecting the data, defining the appropriate type of data needed, and specifying tolerable 

probabilities of making decision errors. 

Quantitative objectives are established for critical 

measurements using the data quality indicators of 

accuracy, precision, and completeness. The acceptance criteria for these data quality indicators (DQIs) 

are summarized later in Table 5-2 of Section 5 of this 

report. Accuracy of measurement parameters is 

determined by comparing a measured value to a 

known standard, assessed in terms of percent bias. 

Values must be within the listed tolerance to be 

considered acceptable. 

Precision is evaluated by making replicate measurements of the same parameter and by assessing the 

variations of the results. Precision is assessed in 

terms of relative percent difference (RPD), or relative 

standard deviation (RSD). Replicate measurements 

are expected to fall within the tolerances shown in 

Table 5-2 of Section 5. Completeness is expressed as 

a percentage of the number of valid measurements 

compared to the total number of measurements taken. 

Estimated minimum detection limits (MDL) of the 

OP-FTIR instrument, by compound, are given in 

Table 1-2. It is important to note that the values listed 

in Table 1-2 should be considered first step approximations, as the MDL is highly variable, and depends 

on many factors including atmospheric conditions. 

Actual MDL are calculated in the quantification 

software for all measurements taken. MDL for each 

absorbance spectrum are determined by calculating 

the root mean square (RMS) absorbance noise in the 

spectral region of the target absorption feature. The 

MDL is the absorbance signal (of the target compound) that is five times the RMS noise level, using 

a reference spectrum acquired for a known concentration of the target compound. 

continued 

1-6
Table 1-2. Detection Limits for Target Compounds (concluded). 

OP-FTIR Estimated Detection AP-42 Value ratioed to an 

Limit for Path Length = 100m, average methane concentra- Compound 1 min Average tion of 50 ppma 

(ppmv) (ppmv) 

Ethylene dibromide 0.0060 0.00000010 

Ethylene dichloride 0.030 0.000041 

Fluorotrichloromethane 0.0040 0.000076 

Hexane 0.0060 0.00066 

Hydrogen sulfide 6.0 0.0036 

Methane 0.024 N/Ab 

Methanol 0.0015 N/A 

Methyl ethyl ketone 0.030 0.00071 

Methyl isobutyl ketone 0.040 0.00019 

Methyl mercaptan 0.060 0.00025 

Methylene chloride 0.014 0.0014 

Octane 0.0025 N/A 

Pentane 0.0080 0.00033 

Propane 0.0080 0.0011 

Propylene dichloride 0.014 0.000018 

Tetrachloroethene 0.0040 0.00037 

Trichlorethylene 0.0040 0.00028 

Vinyl chloride 0.010 0.00073 

Vinylidene chloride 0.014 0.000020 

Xylenes 0.030 0.0012 

a 

b 

The AP-42 values represent an average concentration of different pollutants in the raw landfill gas. This is not comparable 

to the detection limits for the OP-FTIR which is an average value for a path length of 100 meters across the surface of the 

area source being evaluated. However, it does provide an indication of the types of pollutants and range of concentrations 

associated with landfill gas emissions in comparison to the detection limits of the OP-FTIR. 

N/A = not available. 

Table 1-3. Schedule of Work Performed at the Site. 

Day Detail of Work Performed 

Thursday, September 4 to Saturday, September 6 Travel to site 

Sunday, September 7 AM-Set-up 

PM-HRPM Survey of Areas C and D 

Brownfield Landfill in Ft. Collins, Colorado 

1.4 Project Schedule during September 2003. Table 1-3 provides the 

One field campaign was completed for this study schedule of ORS work that was performed. 

continued 

1-7 
Table 1-3. Schedule of Work Performed at the Site (concluded). 

Day Detail of Work Performed 

Monday, September 8 AM-HRPM Survey of Area B 

PM-VRPM Survey 

Tuesday, September 9 AM-HRPM Survey of Area A 

PM-VRPM Survey 

Wednesday, September 10 Travel from site 

Evaluation of Fugitive Emissions at a 

1-8
Brownfield Landfill in Ft. Collins, Colorado 

Chapter 2

Test Procedures

The following subsections describe the test procedures used at each of the four survey areas, which are 

designated as Area A through Area D. Refer to Figure 

1-1 for the geographical orientation of each area. The 

survey areas were chosen to ensure that the study 

investigated the maximum amount of surface area at 

the site. Another factor in selecting the survey areas 

was the location of key areas of interest at the site, 

including playgrounds and soccer fields. The boundaries of each survey area were determined based on 

the location of physical barriers such as buildings and 

trees. HRPM was performed in each area to produce 

surface concentration maps and to locate any surface 

hot spots. In addition, VRPM was performed in Area 

A to obtain an emission flux rate of methane, ammonia, and gasoline from the site. Refer to Figure 1-2 for 

the geographical orientation of the VRPM configurations. VRPM was not performed in the other areas 

due to limitations in the size of the areas, and the 

presence of physical barriers. Each section includes a 

figure that details the position of the mirrors used in 

the HRPM surveys. The coordinates of the mirrors 

used in each configuration are presented in Appendix 

A of this report. 

OP-FTIR data were collected as interferograms. All 

data were archived to CD-ROMs. After archiving, 

interferograms were transferred to ARCADIS personnel who performed the transformations to absorbance 

spectra and then calculated concentrations using 

Non-Lin (Spectrosoft) quantification software. This 

analysis was done after completion of the field 

campaign. Concentration data were then matched with 

the appropriate mirror locations, wind speed, and 

wind direction. The ARCADIS RPM software was 

used to process the data into horizontal plane concentration maps or vertical plane plume visualizations, 

as appropriate. 

Meteorological data including wind direction, wind 

speed, temperature, relative humidity, and barometric 

pressure were continuously collected during the 

measurement campaign with a Climatronics model 

101990-G1 instrument. The Climatronics instrument 

is automated. It collects real-time data from its 

sensors and records time-stamped data as one-minute 

averages to the computer used for data collection. 

Wind direction and speed-sensing heads were used to 

collect data at the surface during the HRPM surveys, 

and at heights of 2 and 10 meters during the VRPM 

survey. The 10 meter sensor was placed on top of the 

scissors jack. The sensing heads for wind direction 

incorporate an auto-north function (automatically 

adjusts to magnetic north) that eliminates the errors 

associated with subjective field alignment to a 

compass heading. After collection, a linear interpolation between the two sets of data is done to estimate 

wind velocity as a function of height. 

Once the concentrations maps and wind information 

are processed, the concentration values are integrated 

incorporating the wind speed component normal to 

the plane at each height level to compute the flux 

through the vertical plane. In this stage, the concentration values are converted from parts per million by 

volume to grams per cubic meter considering the 

molecular weight of the target gas and ambient 

temperature. This enables the direct calculation of 

the flux in grams per second using wind speed data 

in meters per second. 

In reporting the average calculated flux, a moving 

2-1
Evaluation of Fugitive Emissions at a 

average is used in the calculation of the average flux 

values to show temporal variability in the measurements. A moving average involves averaging flux 

values calculated from several different consecutive 

cycles, which are defined as data collected when 

scanning one time through all the mirrors in the 

configuration. For example, a data set taken from 5 

cycles may be reported using a moving average of 4, 

where values from cycles 1 to 4, and 2 to 5 are averaged together to show any variability in the flux 

values. 

Section 3 of the report contains a figure depicting the 

reconstructed gasoline plume map and calculated 

gasoline flux generated from the collected data using 

the VRPM method. It should be noted that the shape 

of the plume maps generated by this method is used to 

give information on the homogeneity of the plume 

and do not affect the calculated flux values. The shape 

of the maps generated represents the best fit of the 

limited data to a symmetric Gaussian function, and 

this fit may drive the plume shape outside of the 

configuration. 

2.1 Area A 

Area A was located in the northwestern section of the 

site. The area was bounded on the north by the Cache 

La Poudre River, on the west by a set of railroad 

tracks, and on the south by a recreational building at 

the site. Figure 2-1 shows a schematic of the HRPM 

configuration used in Area A, and Figure 2-2 shows 

a partial picture of the configuration. The area was 

divided into nine cells, and the OP-FTIR/scanner was 

placed in the southwestern corner of the area. 

2.2 Area B 

Area B was located in a central location at the site. 

The area consisted primarily of a large playground 

and land directly adjacent to the playground. The area 

was bounded on the west by a large parking lot and 

recreation building and on the east by another parking 

lot. Figure 2-3 shows a partial picture of the HRPM 

configuration used in the area. The area was divided 

into eight cells, and the OP-FTIR/scanner was placed 

along the southern boundary of the area. 

Figure 2-1. Schematic of the HRPM 

Configuration Used in Area A. 

Figure 2-2. Partial Picture of the HRPM 

Configuration Used in Area A. 

2.3 Area C 

Area C was located in a central location at the site. 

The area was bounded on the west by the large 

playground in Area B, on the east by the United Way 

building at the site, and on the north by the Cache La 

Poudre River. A small ravine running north to south 

bisected the area. Figure 2-4 shows a partial picture 

of the HRPM configuration used in the area. The 

area was divided into eight cells, and the OP-FTIR/ 

scanner was located along the southern boundary of 

2-2
Brownfield Landfill in Ft. Collins, Colorado 

Figure 2-3. Partial Picture of the HRPM 

Configuration Used in Area B. 

Figure 2-5. Partial Picture of the HRPM 

Configuration Used in Area D. 

Figure 2-4. Partial Picture of the HRPM 

Configuration Used in Area C. 

the area. 

2.4 Area D 

Area D was located in the southeastern corner of the 

site. The area was bounded on the east by the Cache 

La Poudre River, on the west by an industrial area, 

and on the north by a playground on the southern side 

of the United Way Building. Figure 2-5 shows a 

partial picture of the HRPM configuration used in the 

area. The area was divided into eight cells, and the 

OP-FTIR/scanner was set up along the southwestern 

boundary of the area. 

2.5 VRPM Measurements 

The VRPM survey was conducted in Area A using 

two monostatic OP-FTIR instruments and two 

scissors jacks. The configuration formed two vertical 

planes, one upwind and one downwind. The upwind 

plane was located near the eastern boundary of Area 

A, and the downwind plane was located along the 

western boundary of the site (Figure 1-2). Each plane 

consisted of three mirrors placed along the surface 

and two mirrors placed on the scissors jack. Figure 

2-6 shows a partial picture of the VRPM configuration used in the study. 

2.6 OP-TDLAS Measurements 

The OP-TDLAS system was deployed during each 

day of the field campaign to provide additional 

information on methane concentrations at the site. 

The OP-TDLAS is a more cost-effective instrument 

for collecting measurements of specific target compounds, such as methane. The methane measurements from the OP-TDLAS served as a validation of 

methane measurements taken with the OP-FTIR. 

Figure 2 7 shows a picture of the OP-TDLAS system. 

The OP-TDLAS collected data along the surface in 

Areas C and D on September 7 and in Areas A and B 

on September 8. On September 9, the instrument was 

2-3
Evaluation of Fugitive Emissions at a 

Figure 2-6. Partial Picture of the VRPM 

Configuration Used at the Site. 

Figure 2-8. UV-DOAS Instrument. 

Figure 2-7. OP-TDLAS System. 

set up in Area A and collected data using surface and 

vertical beam paths. In most cases, the optical configurations used with the OP-TDLAS were very similar 

to the configurations used with the OP-FTIR instrument. The distance of the path lengths used in each 

OP-TDLAS configuration are presented in Appendix 

B of this report. 

2.7 UV-DOAS Measurements 

The UV-DOAS instrument was deployed at the site 

by a representative of OPSIS, Inc. to provide supplemental data on BTX concentrations at the site. The 

instrument collects continuous measurements and 

reports one-minute, path-averaged concentrations. 

Figure 2-8 shows a picture of the UV-DOAS instrument. 

On September 9, the instrument was set up along the 

western boundary of Area A. The UV-DOAS configuration in Area A was approximately parallel to the 

path of mirror 3 from the VRPM survey done in this 

area with the OP-FTIR instrument. The UV-DOAS 

instrument collected data on this day for approximately three hours. 

2-4
Table 3-1. Average Methane Concentrations Measured During the HRPM Survey of Area A. 

Methane Concentrations

Loop (ppm)

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 Mirror 9 

1 1.81 1.83 1.81 1.81 1.81 1.81 1.86 1.83 1.83 

2 1.81 1.83 1.81 1.81 1.82 1.80 1.84 1.81 1.82 

3 1.80 1.82 1.78 1.79 1.80 1.79 1.83 1.80 1.79 

4 1.79 1.82 1.80 1.80 1.80 1.78 1.83 1.80 1.80 

5 1.79 1.81 1.78 1.79 1.79 1.78 1.83 1.79 1.78 

6 1.79 1.81 1.78 1.76 1.79 1.77 1.83 1.79 1.78 

7 1.78 1.80 1.78 1.77 1.79 1.77 1.82 1.78 1.79 

8 1.78 1.80 1.78 1.77 1.78 1.71 1.82 1.78 1.78 

9 1.80 1.79 1.78 1.77 1.77 1.76 1.82 1.78 1.78 

10 1.77 1.79 1.77 1.77 1.78 1.76 1.83 1.78 1.78 

Brownfield Landfill in Ft. Collins, Colorado 

Chapter 3

Results and Discussion

The results from the ORS-RPM data collected at the 

site are presented in the following subsections. The 

HRPM results from Areas B, C, and D are not presented because no significant hot spots of methane or 

VOC were detected in these areas. Data from the 

VRPM surveys were collected only in Area A. 

VRPM surveys in Areas B, C, or D were not necessary because the HRPM surveys in these areas 

indicated that there were no significant methane or 

VOC hot spots to contribute to a significant emissions flux. Moreover, physical and geographical 

barriers in Areas B, C, and D would have precluded 

VRPM measurements. It should be noted that the 

concentration values reported in the following sections have not been corrected to standard atmospheric 

conditions. 

3.1 Area A 

Data from HRPM and VRPM surveys using the OPFTIR instrument were collected for Area A, In 

addition, the OP-TDLAS collected methane emission 

data to validate the OP-FTIR measurements, and the 

UV-DOAS collected supplemental BTX data. 

3.1.1 HRPM Results 

A HRPM survey was performed in Area A to identify 

possible hot spots of methane and VOCs. Table 3 1 

presents the average methane concentrations detected 

along each beam path in the configuration. The 

locations of the mirrors used in this configuration are 

presented in Appendix A of this report. 

continued 

3-1
Table 3-1. Average Methane Concentrations Measured During the HRPM Survey of Area A 

(concluded). 

Methane Concentrations 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 Mirror 9 

11 1.77 1.79 1.78 1.78 1.80 1.77 1.81 1.78 1.78 

12 1.78 1.80 1.78 1.78 1.79 1.77 1.83 1.80 1.79 

13 1.78 1.79 1.77 1.78 1.78 1.77 1.81 1.79 1.77 

14 1.78 1.80 1.77 1.78 1.79 1.77 1.82 1.78 1.77 

15 1.77 1.79 1.78 1.78 1.78 1.76 1.81 1.78 1.78 

Mean 1.79 1.80 1.78 1.78 1.79 1.77 1.83 1.79 1.79 

Std. 

Dev. 0.014 0.015 0.013 0.014 0.013 0.022 0.012 0.014 0.016 

Evaluation of Fugitive Emissions at a 

The survey did not detect the presence of any methane hot spots along the surface in Area A. This is 

supported by the relatively small standard deviations 

of measured methane concentrations for each beam 

path in the configuration (Table 3-1). Average methane concentrations measured along each beam path 

were very close to ambient background levels. 

The HRPM survey detected the presence of gasoline 

(primarily octane) in Area A. Figure 3-1 presents the 

reconstructed map of surface gasoline concentrations 

(in parts per billion) measured in Area A. The figure 

shows the presence of one hot spot with an average 

concentration over 81 ppb and a maximum concentration of about 100 ppb located in the southern corner 

of Area A. The MDL of the OP-FTIR instrument is 

15 ppb for gasoline. 

Figure 3-1. Reconstructed Gasoline Surface Concentrations in 

Area A. 

3-2
Brownfield Landfill in Ft. Collins, Colorado 

3.1.2 VRPM Results 

The VRPM survey of the site detected methane, 

ammonia, and gasoline on the downwind VRPM 

configuration (Figure 1-2). Figure 3-2 shows a time 

series of methane and ammonia concentrations 

measured along beam path #5 of the VRPM downwind survey (which extended from the OP-FTIR 

instrument to the mirror placed at the top of the 

scissors jack), and observed wind direction during the 

period of data collection. The methane and ammonia 

concentrations are well-correlated, indicating that the 

measured concentrations probably came from the 

same source. The peak concentrations of methane and 

ammonia occur during periods that the wind direction 

is around -20o from normal to the plane of the configuration (approximately 123o from due north). Since 

methane and ammonia hot spots were not detected 

during the HRPM survey of Area A, and methane and 

ammonia were detected on the downwind VRPM 

configuration when the winds shifted to a more 

easterly direction, it is likely that the source of the 

methane and ammonia detected is located outside of 

Area A across the river. 

Figure 3-3 is a vertical map of the reconstructed 

gasoline plume from the downwind VRPM survey 

showing contours of gasoline concentrations in parts 

per million. The average calculated gasoline flux 

from this survey was 0.87 g/s. The reconstruction 

shows that the shape of the plume is very broad both 

horizontally and vertically, indicating that the source 

of the plume is relatively far from the configuration. 

This is consistent with the location of the gasoline hot 

spot found in the HRPM survey of this area. No 

vertical gasoline plume was detected on the upwind 

VRPM configuration, but low levels of gasoline were 

detected on the surface beam paths of the upwind 

VRPM configuration. This is probably due to the 

gasoline hot spot located close to the axis of the 

upwind VRPM configuration (Figures 1-1 and 1-2). 

Figure 3-2. Time Series of Wind Direction and Concentrations of Methane 

and Ammonia Measured on Beam Path #5 of the VRPM Downwind Survey. 

3-3
Evaluation of Fugitive Emissions at a 

Figure 3-3. Reconstructed Gasoline Plume Map from the Downwind 

VRPM Survey. 

Figure 3-4 presents a time series of gasoline, methane, and ammonia fluxes measured during the downwind VRPM survey. The average flux values were 

calculated using a moving average of 4 cycles. The 

well-correlated methane and ammonia fluxes appeared during the second half of the survey when 

wind shifted slightly to the east. These flux values are 

probably a significant underestimation of the emission rate of the methane and ammonia source because 

only a small portion of the plume was captured by the 

measurement configuration. However, the gasoline 

flux values are significant throughout the measurement period. The gasoline flux values are probably a 

slight underestimation of the source emission rate 

since the detected hot spot is located approximately 

100 meters away from the downwind VRPM configuration. The highest gasoline flux values occurred 

during periods when the observed wind direction was 

close to perpendicular to the downwind VRPM 

configuration (see Figure 3-2 for a time series of 3.1.3 UV-DOAS Results 

observed wind directions during this period). The UV-DOAS instrument was set up along the 

Figure 3-4. Gasoline, Methane, and Ammonia 

Fluxes Measured during the Downwind VRPM 

Survey. 

3-4
Table 3-2. Average Concentration of BTX Compounds Measured by the UV-DOAS Instrument. 

Concentration 

Compound (ppb) 

Average Range Std. Dev.

benzene 2.6 0.91 to 7.2 1.8 

toluene 21 5.6 to 27 5.8 

p-xylene 4.9 3.8 to 7.6 0.95 

Brownfield Landfill in Ft. Collins, Colorado 

surface approximately parallel to the downwind 

VRPM configuration on September 9. Table 3-2 

presents the average concentrations of benzene, 

toluene, and p-xylene (in parts per billion) measured 

by the UV-DOAS instrument during the same time 

period as the VRPM run. The MDL of the UV-DOAS 

instrument was 1 ppb for benzene, toluene, and 

p-xylene. 

Figure 3-5 presents a time series of gasoline concentrations (in parts per billion) collected with the 

OP-FTIR instrument along beam path #3 (which 

extended along the surface from the OP-FTIR instru 

ment to the base of the scissors jack), and BTX 

concentrations (in parts per billion) collected with the 

UV-DOAS instrument. The time period depicted in 

the figure represents times that the two instruments 

were concurrently collecting data. The figure shows 

that the concentrations of toluene and gasoline 

correlate well although they were collected with 

different instruments, indicating that the detected 

gasoline plume contains BTX compounds below the 

detection levels of the OP-FTIR (MDL of 90 ppb for 

benzene, 40 ppb for toluene, and 37 ppb for 

p-xylene). 

3.1.4 Summary of Results from Area A 

Figure 3-6 presents a summary of the results of the 

gasoline surface concentration map from the HRPM 

survey in Area A showing a hot spot in the southern 

corner of the area. The figure also shows the suspected location of the source of methane and ammonia measured on the VRPM downwind plane. The 

location of this source is based on wind data and the 

fact that methane and ammonia plumes were not 

Figure 3-5. Time Series of Path-Averaged 

Concentrations of Benzene, Toluene, and 

p-Xylene Measured with the UV-DOAS 

Instrument and Gasoline Measured with the 

OP-FTIR in Area A. 

detected during the HRPM survey or the upwind 

VRPM configuration. 

3.2 Areas B, C, and D 

HRPM surveys were completed in Areas B, C, and D, 

and these surveys did not detect any methane hot 

spots. Table 3-3 presents the average methane concentrations (in parts per million) found during the 

HRPM survey of Areas B, C, and D. The location of 

the mirrors used in each configuration are presented 

in Appendix A. The table shows that the average 

surface methane concentrations measured in each 

area were close to ambient background levels. The 

fact that the standard deviations of the methane 

concentrations are small relative to the mean measured concentration in each area supports the finding 

that methane hot spots were not present. 

The data collected from the HRPM surveys of Areas 

B, C, and D were also analyzed for the presence of 

VOCs. Methanol was detected along beam path #3 in 

Area B, indicating a small hot spot south of the 

playground. The average methanol concentration 

measured was 20.9 ppb, with a range from not detected (at the OP-FTIR MDL of 14 ppb) to 127 ppb. 

3-5
Evaluation of Fugitive Emissions at a 

Figure 3-7 presents a time series of measured methanol concentrations. 

3.3 OP-TDLAS Measurements 

The OP-TDLAS measured methane concentrations in 

Areas A, B, C, and D. As mentioned previously, the 

configurations used by the OP-TDLAS were often 

similar to the configurations used with the OP-FTIR 

instruments. Data from the survey of Area C were 

unavailable due to a software malfunction. Table 3-4 

presents the average methane concentrations (in parts 

per million) measured at the site by the OP-TDLAS 

system. The table also includes information on the 

average methane concentrations measured by the 

OP-FTIR instrument for cases that the OP-FTIR 

beam paths were similar to those of the OP-TDLAS. 

The methane concentrations measured by the 

OP-TDLAS did not show much variability between 

areas. In fact, most of the measured concentrations 

were only slightly above ambient methane levels, 

reinforcing the findings of the HRPM surveys. 

Concentrations measured with the OP-TDLAS 

ranged from 1.83 to 2.09 ppm. The methane concentrations measured with the OP-TDLAS system were 

almost always slightly higher than concentrations 

measured with the OP-FTIR instrument along similar 

optical paths. 

Figure 3-6. Results Summary Map from Area A Measurements. 

3-6
Table 3-3. Average Methane Concentrations Found during the HRPM Surveys of Areas B, C, and D.

Concentration

Area (ppm)

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 

A 1.89±0.027 1.81±0.008 1.89±0.012 1.81±0.009 1.92±0.012 1.82±0.005 1.81±0.009 1.89±0.009 

B 1.80±0.011 1.76±0.011 1.75±0.012 1.73±0.010 1.73±0.011 1.74±0.011 1.74±0.010 1.78±0.011 

C 1.80±0.020 1.75±0.020 1.73±0.017 1.77±0.018 1.73±0.018 1.75±0.018 1.72±0.017 1.71±0.017 

Brownfield Landfill in Ft. Collins, Colorado

Figure 3-7. Time Series of Methanol Concentrations Measured 

along Beam Path #3 of the Area B HRPM Survey. 

3-7
Table 3-4.Comparison of Methane Concentrations Measured with the OP-TDLAS and OP-FTIR 

Instruments. 

Methane Concentration 

(ppm) 

Mirror Area A Area B Area D 

No. 09/08/03 09/09/03 

OP- OP- OP- OPOP- OP- OP- OP- OP- OP- TDLAS FTIR TDLAS FTIR

TDLAS FTIR TDLAS FTIR TDLAS FTIR 

Avg. 1.91 1.92 1.94 1.96 1.74 2.01 1.81 2.03 1.80 

1 

Std. Dev. 0.02 0.03 0.02 0.05 0.04 0.04 0.01 0.12 0.02 

Avg. 1.99 1.88 1.96 1.78 1.83 1.88 2.03 1.93 1.77 

2 

Std. Dev. 0.08 0.03 0.01 0.01 0.12 0.04 0.05 0.18 0.02 

Avg. 2.08 1.84 1.98 1.78 2.03 1.86 2.06 1.81 1.90 1.75 

3 

Std. Dev. 0.05 0.02 0.01 0.01 0.05 0.04 0.05 0.02 0.24 0.02 

Avg. 2.05 1.85 1.95 1.77 2.03 1.88 2.03 1.98 1.75 

4 

Std. Dev. 0.04 0.03 0.02 0.02 0.05 0.05 0.04 0.12 0.02 

Avg. 2.06 1.84 1.98 1.79 2.03 1.87 1.98 1.82 1.94 1.73 

5 

Std. Dev. 0.05 0.02 0.03 0.02 0.04 0.04 0.03 0.02 0.12 0.02 

Avg. 2.09 1.99 2.07 2.05 1.95 1.72 

6 

Std. Dev. 0.03 0.02 0.06 0.02 0.15 0.02 

Avg. 2.09 2.01 2.04 2.02 1.81 1.99 1.73 

7 

Std. Dev. 0.02 0.02 0.05 0.02 0.02 0.13 0.02 

Avg. 2.06 1.96 2.04 2.07 1.97 1.71 

8 

Std. Dev. 0.02 0.02 0.04 0.02 0.15 0.02 

Evaluation of Fugitive Emissions at a 

3-8
Brownfield Landfill in Ft. Collins, Colorado 

Chapter 4

Conclusion

This report presents the results from a field campaign 

conducted in September 2003 at a former landfill site 

in Fort Collins, Colorado. The study used measurements from several ground-based ORS instruments 

and the ORS-RPM method to characterize fugitive 

emissions of methane, ammonia, and VOCs from the 

site. 

HRPM surveys of the site did not detect the presence 

of any methane hot spots, and methane surface 

concentrations at the site were essentially at ambient 

background levels. The HRPM survey of Area A 

detected a gasoline hot spot (average concentration 

over 81 ppb, maximum concentration about 100 ppb) 

in the southern corner of Area A (north of the large 

playground adjacent to the gymnasium). The HRPM 

survey of Area B detected the presence of methanol 

along beam path #3, indicating a small hot spot south 

of the large playground, within the fence line of the 

property. The average methanol concentration measured during the survey was 21 ppb. 

A VRPM survey was done in Area A to measure 

fluxes of fugitive emissions. The VRPM survey 

detected methane, ammonia, and gasoline in the 

downwind configuration, along the fence line of the 

site. The measured concentrations of methane and 

ammonia correlated well temporally, suggesting the 

source of the methane and ammonia emissions may 

be the same. Looking at data on wind direction and 

the lack of methane and ammonia concentrations 

measured during the HRPM survey, it is concluded 

that this source of ammonia and methane was located 

outside of Area A, northeast of the survey area 

(across the river). The calculated gasoline flux of 

0.87 g/s was from the gasoline hot spot detected 

during the HRPM survey of Area A. Since the location of this hot spot is approximately 100 meters 

upwind of the VRPM measurement configuration, it 

is concluded that this flux is a slight underestimation 

of the actual emission rate from the source because a 

small portion of the plume may not have been captured by the measurement configuration. The above 

conclusions are confirmed by the fact that the VRPM 

survey did not detect any methane, ammonia, or 

gasoline plumes along the upwind configuration. 

The UV-DOAS instrument was deployed in Area A 

to collect data concurrently with the OP-FTIR instrument. The UV-DOAS detected the presence benzene, 

toluene, and p-Xylene. The average measured concentrations of benzene, toluene, and p-Xylene were 

2.6 ppb, 21 ppb, and 4.9 ppb, respectively. The 

concentrations of toluene measured with the 

UV-DOAS instrument correlated well with gasoline 

concentrations measured with the OP-FTIR instrument during the same time period, indicating that the 

gasoline plume contains BTX compounds at levels 

lower than the MDL of the OP-FTIR. 

The OP-TDLAS system collected information on 

methane concentrations in Areas A, B, C, and D. The 

methane concentrations measured with the 

OP-TDLAS were generally slightly higher (less than 

10%) than concentrations measured with the 

OP-FTIR instrument along similar optical paths. 

4-1
Evaluation of Fugitive Emissions at a 

4-2 
Table 5-1. Instrumentation Calibration Frequency and Description. 

Calibration Instrument Measurement Date Calibration Detail

Climatronics Model 101990-G1 Wind speed in 22 April 2003 APPCD Metrology Lab calibration records on 

meteorological heads miles/hour file 

Climatronics Model 101990-G1 Wind direction in 22 April 2003 APPCD Metrology Lab calibration records on 

meteorological heads degrees from north file 

Topcon Model GTS-211D Distance 1 May 2003 Calibration of distance measurement: 

theodolite measurement Actual distance=50 ft. 

Measured distance=50.6 ft. and 50.5 ft. 

Topcon Model GTS-211D Angle 21 May 2003 Calibration of angle measurement: 

theodolite measurement Actual angle= 360o 

Measured angle= 359o41N18O, and 

359o59N55O

Brownfield Landfill in Ft. Collins, Colorado 

Chapter 5

Quality Assurance/Quality Control

5.1 Equipment Calibration

As stated in the ECPD Optical Remote Sensing 

Facility Manual (U.S. EPA, 2004), all equipment is 

calibrated annually or cal-checked as part of standard 

operating procedures. Certificates of calibration are 

kept on file. Maintenance records are kept for any 

equipment adjustments or repairs in bound project 

notebooks that include the data and description of 

maintenance performed. Instrument calibration 

procedures and frequency are listed in Table 5-1 and 

further described in the text. 

As part of the preparation for this project, a Category 

III Quality Assurance Project Plan (QAPP) was 

prepared and approved for each separate field campaign. In addition, standard operating procedures 

were in place during the field campaign. 

5.2 Assessment of DQI Goals 

The critical measurements associated with this 

project and the established data quality indicator 

(DQI) goals in terms of accuracy, precision, and 

completeness are listed in Table 5-2. More information on the procedures used to assess DQI goals can 

be found in Section 10 of the ECPD Optical Remote 

Sensing Facility Manual (U.S. EPA, 2004). 

5.2.1 DQI Check for Analyte PIC Measurement 

The precision and accuracy of the analyte pathintegrated concentration (PIC) measurements was 

assessed by analyzing the measured nitrous oxide 

concentrations in the atmosphere. A typical background atmospheric concentration for nitrous oxide 

is about 315 ppb, but this value may fluctuate due to 

5-1
Evaluation of Fugitive Emissions at a 

Table 5-2. DQI Goals for Instrumentation. 

Measurement 

Parameter Analysis Method Accuracy Precision Detection Limit Completeness 

Analyte PIC OP-FTIR: Nitrous Oxide ±25%/15%/10% a ±10% See Table 1-2 90% 

Concentrations 

Ambient Wind Climatronics heads met ±1 m/s ±1 m/s N/A 90% 

Speed side-by-side comparison in the 

field 

Ambient Wind Climatronics heads met ±10o ±10o N/A 90% 

Direction side-by-side comparison in the 

field 

Distance Theodolite- Topcon ±1m ±1m 0.1m 100% 

Measurement a The accuracy acceptance criterion of ±25% is for pathlengths of less than 50 m, ±15% is for pathlengths between 50 and 100 m, and ±10% 

is for pathlengths greater than 100 m. 

seasonal variations in nitrous oxide concentrations or 

elevation of the site. The elevation of the site surveyed in this field campaign is approximately 5,000 

ft above sea level. At this elevation, the optical 

density of a nitrous oxide concentration of 315 ppb 

would be equivalent to a lower concentration of 

nitrous oxide at sea level, due to the decreased air 

density. To correct the background nitrous oxide 

level for the effects of elevation, the measured 

temperature and atmospheric pressure were ratioed to 

standard temperature and pressure values. The 

corrected background nitrous oxide concentration is 

approximately 265 ppb. 

The precision of the analyte PIC measurements was 

evaluated by calculating the relative standard deviation of each data subset. A subset is defined as the 

data collected along one particular path length during 

one particular survey in one survey sub-area. The 

number of data points in a data subset depends on the 

number of loops used in a particular survey. 

The accuracy of the analyte PIC measurements was 

evaluated by comparing the calculated nitrous oxide 

concentrations from each data subsets to the corrected background concentration of 265 ppb. The 

number of calculated nitrous oxide concentrations 

that failed to meet the DQI accuracy criterion in each 

data subset was recorded. 

Overall, 61 data subsets were analyzed from this field 

campaign. Based on the DQI criterion set forth for 

precision of ±10%, each of the 61 data subsets were 

found to be acceptable. The range of calculated 

relative standard deviations for the data subsets from 

this field campaign was 0.57 to 11.7 ppb, which 

represents 0.22% to 4.4% RSD. 

Each data point (calculated nitrous oxide concentration) in the 61 data subsets were analyzed to assess 

whether or not it met the DQI criterion for accuracy 

of ±25% (265 ± 66 ppb) for path lengths less than 50 

meters, ±15% (265 ± 40 ppb) for path lengths between 50 and 100 meters, and ±10% (265 ± 27 ppb) 

for path lengths greater than 100 meters. All the 1136 

data points that were analyzed met the DQI criteria 

for accuracy. Based on the DQI criterion set forth for 

accuracy and precision, all data points were found to 

be acceptable, for a total completeness of 100%. 

5.2.2 DQI Checks for Ambient Wind Speed 

and Wind Direction Measurements 

Section 10 of the ECPD Optical Remote Sensing 

Facility Manual (U.S. EPA, 2004) states that the DQI 

5-2
Brownfield Landfill in Ft. Collins, Colorado 

goals for precision and accuracy of the Climatronics 

meteorological heads are assessed by collecting 

meteorological data for 10 minutes with the two 

heads set up side-by side. This was not done prior to 

the current field campaign because this DQI procedure had not been implemented at the time of the 

study. However, the Climatronics heads were calibrated in April 2003 by the APPCD Metrology Lab 

(see Table 5 2). Additionally, checks for agreement 

of the wind speed and wind direction measured from 

the two heads (2 m and 10 m) were done in the field 

during data collection. Although it is true that some 

variability in the parameters measured at different 

levels should be expected, this is a good first-step 

check for assessing the performance of the instruments. Another check is done in the field by comparing the measured wind direction to the forecasted 

wind direction for that particular day. 

5.2.3 DQI Check for Precision and Accuracy 

of Theodolite Measurements 

Although this instrument was not calibrated immediately prior to the current field campaign, the theodolite was originally calibrated by the manufacturer 

prior to being received by the U.S. EPA. Additionally, there are several internal checks in the theodolite 

software that prevent data collection from occurring 

if the instrument is not properly aligned on the object 

being measured or if the instrument has not been 

balanced correctly. When this occurs, it is necessary 

to reinitialize the instrument to collect data. 

The following DQI checks were performed on the 

theodolite prior to the current field campaign. These 

checks were performed during May 2003 at a field 

site near Chapel Hill, NC. The calibration of distance 

measurement was done using a tape measure to 

compare the actual distance to the measured distance. 

This check was duplicated to test the precision of this 

measurement. The actual distance measured was 

15.2m. The measured distance during the first test 

was 15.4m, and the measured distance during the 

second test was 15.4m. The results indicate the 

accuracy (1.3% bias for test one and two) and precision (0% RSD) of the distance measurement fell well 

within the DQI goals. 

The check to test the precision and accuracy of the 

angle measurement was done by placing two mirror 

targets approximately 180 degrees apart. The theodolite was placed in the middle of the imaginary circle 

formed by the two mirrors. The actual angle was 

360°. The angle measured during the first test was 

359°41N18O, and the angle measured during the 

second test was 359°59N55O. The results indicate the 

accuracy and precision of the angle measurement fall 

well within the DQI goals. 

5.3 QC Checks of OP-FTIR Instrument 

Performance 

Several checks should be performed on the OP-FTIR 

instrumentation prior to deployment to the field and 

during the field campaign. More information on these 

checks can be found in MOP 6802 and 6807 of the 

ECPD Optical Remote Sensing Facility Manual. At 

the time of the current field campaign, the procedures 

and schedule of QC checks were still being developed. Consequently, QC checks were performed only 

in the field on the Unisearch OP-FTIR. 

On the first day of the field campaign (September 7), 

the single beam ratio, electronic noise, saturation, 

linearity, baseline stability, and random baseline 

noise tests were performed. The results of the saturation test indicated that some saturation was occurring 

in the detector of the instrument. In response to this, 

the instrument detector response was adjusted slightly 

to correct this problem. The results of the other tests 

indicated that the instrument was operating within the 

acceptable criteria range. 

On September 8, the signal-to-noise, and single beam 

ratio tests were performed on the Unisearch 

OP-FTIR. The results of these tests indicated that the 

instrument was operating within the acceptable 

criteria range. 

In addition to the QC checks performed on the 

OP-FTIR, the quality of the instrument signal (interferogram) is checked constantly during the field 

5-3
Evaluation of Fugitive Emissions at a 

campaign. This is done by ensuring that the intensity 

of the signal is at least five times the intensity of the 

stray light signal (the stray light signal is collected as 

background data prior to actual data collection and 

measures internal stray light from the instrument 

itself). In addition to checking the strength of the 

signal, checks are done constantly in the field to 

ensure that the data are being collected and stored to 

the data collection computer. During the campaign, a 

member of the field team constantly monitors the 

data collection computer to make sure these checks 

are completed. 

5.4 Validation of Concentration Data 

Collected with the OP-FTIR 

During the analysis of the OP-FTIR data, a validation 

procedure was performed to aid in identifying the 

presence of gasoline and ammonia in the dataset. This 

validation procedure involves visually comparing an 

example of the measured spectra to a laboratorymeasured reference spectrum. 

Figure 5-1 shows an example of a validation done 

using a spectrum collected at the site. Gasoline was 

detected in this particular spectrum. The reference 

spectrum used to quantify gasoline concentrations is 

an actual laboratory-measured spectrum of Exxon 

87-octane gasoline. The gasoline features can be seen 

in the measured field spectrum (green trace). Classical Least Squares (CLS) analysis performed on this 

spectrum resulted in determinations of 55.1 ± 3.0 ppb 

of gasoline. The uncertainty value is equal to three 

times the standard error in the regression fit of the 

measured spectrum to a calibrated reference spectrum, propagated to the concentration determination. 

Figure 5-2 shows a validation done for an ammonia 

spectrum collected at the site. The ammonia features 

can be clearly seen in the measured field spectrum 

(blue trace). Classical Least Squares (CLS) analysis 

performed on this spectrum resulted in determinations of 17.4 ± 0.97 ppb of ammonia. 

5.5 Internal Audit of Data Input Files

An internal audit was performed by the ARCADIS 

Figure 5-1. Comparison of a Gasoline Spectrum 

Measured at the Site (Green Trace) to Reference 

Spectra of Gasoline (Red Trace). 

Figure 5-2. Comparison of an Ammonia Spectrum Measured at the Site (Blue Trace) to Reference Spectra of Ammonia (Red Trace). 

Field Team Leader on a sample of approximately 

10% of the data from the field campaign. The audit 

investigated the accuracy of the input files used in 

running the radial plume mapping (RPM) programs. 

The input files contain analyzed concentration data, 

mirror path lengths, and wind data. The results of this 

audit found no problems with the accuracy of the 

input files created. 

5-4
Brownfield Landfill in Ft. Collins, Colorado 

5.6 OP-TDLAS Instrument 

At the time of the field campaign, the OP-TDLAS 

system had only recently been acquired by EPA. 

Consequently, standard operating and calibration 

procedures were still being developed. Many improvements have been made to the QA process since 

this field campaign. Some of these improvements 

include the development of calibration cells and the 

development of a standard operating procedure for 

collecting emissions measurements with the 

OP-TDLAS (see MOP 6811 of the ECPD Optical 

Remote Sensing Facility Manual). 

The comparison of methane concentrations measured 

with the OP-TDLAS system to methane concentrations measured with the OP-FTIR is a good validation of the OP-TDLAS. Table 3-4 shows that there is 

reasonable agreement between the concentrations 

measured with the two instruments, although the 

methane concentrations measured with the 

OP-TDLAS system were generally slightly higher 

(within 10%) than concentrations measured with the 

OP-FTIR instrument along similar optical paths. The 

data from Table 3-4 also indicates that the precision 

of the data collected with the OP-FTIR is better than 

the precision of the OP-TDLAS data. This is especially true of data collected in Area D, where the 

standard deviation of the OP-TDLAS data is as high 

as 0.24 ppm. 

An experiment performed in January 2004 compared 

methane concentrations measured with the 

OP-TDLAS system and the IMACC OP-FTIR. The 

experiment collected methane measurements at a 

wide range of concentrations. Figure 5-3 shows the 

results of this experiment. The results show that there 

is very good agreement in methane concentrations 

measured with both instruments. However, a closer 

inspection of this dataset found that the precision of 

the OP-TDLAS data was not favorable at methane 

concentrations close to ambient background levels. 

This is consistent with the findings of the current 

study. 

Despite the issue of precision of the OP-TDLAS 

Figure 5-3. Post-Fort Collins Comparison of 

Methane Concentrations Measured with the 

OP-TDLAS and OP FTIR Instruments. 

instrument at low concentrations, it is apparent from 

the data presented in Figure 5-3 that methane concentrations measured with the OP-TDLAS and OP-FTIR 

instruments are comparable for area emissions 

monitoring when a wide range of concentrations are 

measured. 

5.7 UV-DOAS Instrument 

Data from the UV-DOAS instrument were collected 

and analyzed by a representative of OPSIS, Inc. The 

following QC summary was created using information provided to ARCADIS by OPSIS, Inc. 

• The UV-DOAS AR500 emitter and receiver were 

placed on a stable foundation in order to provide 

a high and stable light signal input to the spectrometer. 

• The AR500 provides a system check function that 

performed a complete check of the integrity of 

the spectrometer. 

• A zero and span calibration check was performed 

for all gases involved when the system was 

installed at the site. 

• Monitored data, including the stored concentra5-5
Evaluation of Fugitive Emissions at a 

tion, deviation, and light level values, were 

reviewed. Data that was sampled with light level 

values below minimum threshold were invalidated. A few of the data points collected were 

invalidated due to loss of light signal. 

• Spectral validation of the detected compounds 

(similar to validation provided for the OP-FTIR 

data in Section 5.4) was not provided. This is 

recommended for future studies using the 

UV-DOAS instrument. 

• In the application of BTX measurements using 

the standard resolution spectrometer, the effect of 

oxygen in the monitoring path was compensated 

for. This was done in the oxygen reference calibration procedure. This procedure was performed 

for each specific optical path length that the 

system operated on. Some of the data were corrected in offset levels. The origin of offset concentration was due to the fact that only one 

oxygen reference was performed during the 

project. 

• The MDL for benzene, toluene, and p-xylene was 

1 ppb. The precision and accuracy of the measurements is 1%, as reported by OPSIS, Inc. 

5-6
Brownfield Landfill in Ft. Collins, Colorado 

Chapter 6

List of References

Hashmonay, R.A., M.G. Yost, D.B. Harris, and E.L. Thompson (1998), Simulation study for gaseous fluxes 

from an area source using computed tomography and optical remote sensing, presented at SPIE Conference 

on Environmental Monitoring and Remediation Technologies, Boston, MA, Nov., 1998, in SPIE Vol. 3534, 

pp. 405-410. 

Hashmonay, R.A., and M.G. Yost (1999), Innovative approach for estimating fugitive gaseous fluxes using 

computed tomography and remote optical sensing techniques, J. Air Waste Manage. Assoc., 49:8, pp. 966-972. 

Hashmonay, R.A., M.G. Yost, and C. Wu (1999), Computed tomography of air pollutants using radial scanning 

path-integrated optical remote sensing, Atmos. Environ., 33:2, pp. 267-274. 

Hashmonay, R.A., D.F. Natschke, K.Wagoner, D.B. Harris, E.L.Thompson, and M.G. Yost (2001), Field 

evaluation of a method for estimating gaseous fluxes from area sources using open-path Fourier transform 

infrared, Environ. Sci. Technol., 35:11, pp. 2309-2313. 

Hashmonay, R.A., K. Wagoner, D.F. Natschke, D.B. Harris, and E.L. Thompson (2002), Radial computed 

tomography of air contaminants using optical remote sensing, presented June 23-27, 2002 at the AWMA 95th 

Annual Conference and Exhibition, Baltimore, MD. 

Platt, U. (1994), Differential optical absorption spectroscopy (DOAS), In: Air Monitoring by Spectroscopic 

Techniques, Chemical Analysis Series, Vol. 127, John Wiley & Sons, Inc. pp. 27-84. 

U.S. EPA QA/G4 (2000), Guidance for the Data Quality Objectives Process, EPA-600/R-96/055, Office of 

Environmental Information, U.S. EPA, Washington, DC. Also at 

http://www.epa.gov/quality/qs-docs/g4-final.pdf (accessed April 2005). 

U.S. EPA (2004), ECPB Optical Remote Sensing Facility Draft Facility Manual, approved April. 

Wu, C., M.G. Yost, R.A. Hashmonay, and D.Y. Park (1999), Experimental evaluation of a radial beam 

geometry for mapping air pollutants using optical remote sensing and computed tomography, Atmos. Environ., 

33:28, pp. 4709-4716. 

6-1
Evaluation of Fugitive Emissions at a 

6-2 
Table A-2. Standard Distance and Horizontal

Coordinates of Mirrors Used in the HRPM Survey

of Area B. 

Standard Horizontal Angle Mirror Distance from North Number (m) (degrees) 

1 42.4 353 

2 83.7 1 

3 37.9 10 

4 79.1 15 

5 38.2 25 

6 77.2 29 

7 82.8 50 

8 45.2 54 

Table A-1. Standard Distance and Horizontal 

Coordinates of Mirrors Used in the HRPM Survey 

of Area A. 

Standard Horizontal Angle Mirror Distance from North Number (m) (degrees) 

1 125 76 

2 87.3 82 

3 149 88 

4 179 97 

5 117 99 

6 149 105 

7 49.8 110 

8 86.2 116 

9 121 120 

Table A-4. Standard Distance and Horizontal

Coordinates of Mirrors Used in the HRPM Survey

of Area D. 

Standard Horizontal Angle Mirror Distance from North Number (m) (degrees) 

1 52.2 286 

2 84.9 290 

3 107 292 

4 52.5 309 

5 87.5 310 

6 50.0 341 

7 88.2 335 

8 126 329 

Brownfield Landfill in Ft. Collins, Colorado 

Appendix A

OP-FTIR Mirror Coordinates

Table A-3. Standard Distance and Horizontal 

Coordinates of Mirrors Used in the HRPM Survey 

of Area C. 

Mirror 

Number 

Standard 

Distance 

(m) 

Horizontal Angle 

from North 

(degrees) 

1 50.0 68 

2 69.7 62 

3 93.2 61 

4 139 59 

5 129.1 40 

6 92.7 30 

7 68.3 29 

8 37.9 20 

A-1
Table A-5. Standard Distance and Horizontal

Coordinates of Mirrors Used in the VRPM Survey.

Horizontal Standard Mirror Angle from Vertical Anglea 

Distance Number North (degrees) (m) (degrees) 

Upwind 

1 36.9 65 0 

2 68.7 70 0 

3 110 70 0 

70b 4 113 1 

69b 5 113 5 

Downwind 

1 44.9 48 0 

2 89.9 51 0 

3 117 53 0 

4 118 53 2 

5 118 53 6 a Vertical angle shown is the angle from horizontal (positive values 

indicate elevation from the horizontal, negative values indicate 

descent from the horizontal). b Although Mirrors 4 and 5 were on the same scissors jack, Mirror 5 

was not directly above Mirror 4. 

Evaluation of Fugitive Emissions at a 

A-2
Table B-1. Standard Distance of Path Lengths Used in OP-TDLAS Configurations. 

Area A 

09/09/03 Area B Mirror Number 09/08/03 (m) Surface Vertical (m) (m) (m) Area D

(m)

1 41.0 136 48.1 82.4 52.2 

2 76.3 146 83.6 80.9 52.5 

3 118 174 119 79.6 50.0 

4 119 143 120 79.3 84.9 

5 119 114 120 79.3 87.5 

6 173 156 156 80.6 88.2 

7 203 193 194 87.1 107 

8 195 105 106 153 126 

Brownfield Landfill in Ft. Collins, Colorado 

Appendix B 

OP-TDLAS Configuration Path Length Distances 

B-1
Evaluation of Fugitive Emissions at a 

B-2
Brownfield Landfill in Ft. Collins, Colorado 

Appendix C 

Methane Concentrations 

Table C-1. Methane Concentrations Found during the Area A HRPM Survey. 

Methane Concentration 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 Mirror 9 

1 1.81 1.83 1.81 1.81 1.81 1.81 1.86 1.83 1.83 

2 1.81 1.83 1.81 1.81 1.82 1.80 1.84 1.81 1.82 

3 1.80 1.82 1.78 1.79 1.80 1.79 1.83 1.80 1.79 

4 1.79 1.82 1.80 1.80 1.80 1.78 1.83 1.80 1.80 

5 1.79 1.81 1.78 1.79 1.79 1.78 1.83 1.79 1.78 

6 1.79 1.81 1.78 1.76 1.79 1.77 1.83 1.79 1.78 

7 1.78 1.80 1.78 1.77 1.79 1.77 1.82 1.78 1.79 

8 1.78 1.80 1.78 1.77 1.78 1.71 1.82 1.78 1.78 

9 1.80 1.79 1.78 1.77 1.77 1.76 1.82 1.78 1.78 

10 1.77 1.79 1.77 1.77 1.78 1.76 1.83 1.78 1.78 

11 1.77 1.79 1.78 1.78 1.80 1.77 1.81 1.78 1.78 

12 1.78 1.80 1.78 1.78 1.79 1.77 1.83 1.80 1.79 

13 1.78 1.79 1.77 1.78 1.78 1.77 1.81 1.79 1.77 

14 1.78 1.80 1.77 1.78 1.79 1.77 1.82 1.78 1.77 

15 1.77 1.79 1.78 1.78 1.78 1.76 1.81 1.78 1.78 

C-1
Table C-2. Methane Concentrations Found during the Area B HRPM Survey. 

Methane Concentration

Loop (ppm)

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 

1 1.90 1.81 1.90 1.83 1.92 1.83 1.82 1.88 

2 1.91 1.81 1.89 1.82 1.94 1.82 1.82 1.90 

3 1.89 1.82 1.89 1.82 1.93 1.82 1.81 1.89 

4 1.90 1.81 1.90 1.83 1.92 1.82 1.81 1.89 

5 1.90 1.81 1.89 1.80 1.91 1.82 1.81 1.90 

6 1.85 1.82 1.90 1.81 1.92 1.81 1.82 1.88 

7 1.90 1.80 1.89 1.82 1.92 1.82 1.80 1.88 

8 1.89 1.80 1.88 1.80 1.92 1.82 1.81 1.88 

9 1.89 1.80 1.87 1.81 1.92 1.81 1.80 1.88 

10 1.89 1.80 1.89 1.81 1.90 1.81 1.81 1.88 

11 1.90 1.81 1.89 1.81 1.89 1.81 1.80 1.88 

12 1.89 1.80 1.90 1.82 1.92 1.81 1.80 1.80 

13 1.83 1.81 1.89 1.81 1.91 1.81 1.81 1.89 

14 1.84 1.80 1.90 1.81 1.90 1.82 1.83 1.91 

15 1.92 1.82 1.92 1.82 1.92 1.82 1.82 1.89 

Evaluation of Fugitive Emissions at a 

Table C-3. Methane Concentrations Found during the Area C HRPM Survey. 

Methane Concentration 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 

1 1.78 1.74 1.73 1.71 1.71 1.72 1.73 1.76 

2 1.78 1.74 1.72 1.71 1.71 1.72 1.73 1.77 

3 1.78 1.75 1.73 1.71 1.72 1.73 1.73 1.77 

4 1.79 1.76 1.75 1.72 1.73 1.74 1.74 1.78 

5 1.79 1.75 1.73 1.73 1.72 1.74 1.74 1.78 

6 1.78 1.76 1.75 1.73 1.73 1.74 1.74 1.78 

7 1.79 1.76 1.74 1.72 1.73 1.74 1.74 1.78 

8 1.80 1.76 1.75 1.73 1.73 1.74 1.74 1.79 

9 1.80 1.76 1.74 1.73 1.73 1.75 1.75 1.79 

10 1.80 1.76 1.76 1.74 1.74 1.76 1.75 1.80 

11 1.81 1.77 1.76 1.74 1.74 1.76 1.76 1.79 

12 1.81 1.77 1.76 1.73 1.73 1.75 1.75 1.79 

13 1.80 1.76 1.75 1.73 1.74 1.75 1.75 1.79 

14 1.81 1.77 1.76 1.74 1.74 1.75 1.75 1.79 

15 1.81 1.77 1.76 1.74 1.73 1.75 1.75 1.79 

16 1.80 1.77 1.75 1.74 1.74 1.76 1.75 1.80 

C-2
Brownfield Landfill in Ft. Collins, Colorado 

Table C-4. Methane Concentrations Found during the Area D HRPM Survey. 

Methane Concentration 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 Mirror 6 Mirror 7 Mirror 8 

1 1.78 1.73 1.71 1.75 1.72 1.73 1.70 1.69 

2 1.77 1.74 1.72 1.76 1.71 1.74 1.71 1.70 

3 1.78 1.73 1.72 1.76 1.71 1.73 1.70 1.69 

4 1.79 1.73 1.71 1.75 1.72 1.73 1.70 1.70 

5 1.78 1.74 1.72 1.76 1.72 1.73 1.69 1.70 

6 1.78 1.74 1.71 1.76 1.72 1.74 1.70 1.69 

7 1.78 1.73 1.72 1.75 1.72 1.73 1.70 1.70 

8 1.78 1.73 1.71 1.76 1.72 1.73 1.71 1.69 

9 1.77 1.74 1.71 1.75 1.71 1.72 1.70 1.69 

10 1.78 1.73 1.71 1.76 1.72 1.73 1.70 1.70 

11 1.78 1.74 1.72 1.77 1.73 1.73 1.70 1.70 

12 1.79 1.75 1.72 1.76 1.72 1.73 1.71 1.70 

13 1.78 1.74 1.71 1.77 1.73 1.73 1.71 1.71 

14 1.78 1.75 1.72 1.76 1.73 1.73 1.71 1.71 

15 1.79 1.75 1.73 1.77 1.74 1.74 1.71 1.71 

16 1.80 1.75 1.73 1.78 1.74 1.75 1.72 1.73 

17 1.81 1.74 1.74 1.79 1.76 1.76 1.73 1.73 

18 1.81 1.82 1.77 1.78 1.73 1.76 1.73 1.73 

19 1.85 1.77 1.73 1.78 1.75 1.77 1.74 1.74 

20 1.82 1.77 1.75 1.81 1.76 1.79 1.74 1.73 

21 1.83 1.77 1.75 1.79 1.75 1.77 1.73 1.73 

22 1.82 1.77 1.75 1.80 1.76 1.78 1.74 1.74 

23 1.82 1.79 1.75 1.78 1.74 1.77 1.72 1.72 

24 1.80 1.76 1.73 1.77 1.74 1.76 1.72 1.72 

25 1.80 1.75 1.74 1.78 1.73 1.76 1.72 1.72 

26 1.80 1.76 1.70 1.77 1.73 1.75 1.73 1.73 

27 1.80 1.77 1.75 1.79 1.76 1.76 1.73 1.73 

28 1.80 1.78 1.76 1.80 1.77 1.77 1.75 1.74 

29 1.82 1.77 1.75 1.81 1.75 1.77 1.74 1.73 

30 1.81 1.76 1.74 1.78 1.74 1.76 1.72 1.73 

C-3
Evaluation of Fugitive Emissions at a 

Table C-5. Methane Concentrations Found during the Downwind VRPM Survey Run 1. 

Methane Concentration 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 

1 1.92 1.87 1.82 1.83 1.81 

2 1.91 1.86 1.81 1.83 1.84 

3 1.90 1.87 1.84 1.86 1.87 

4 1.97 1.92 1.83 1.81 1.81 

5 1.97 1.88 1.81 1.81 1.80 

6 1.91 1.84 1.80 1.82 1.80 

7 1.85 1.84 1.79 1.81 1.79 

8 1.89 1.83 1.81 1.86 1.85 

9 1.90 1.86 1.81 1.83 1.81 

10 1.91 1.86 1.82 1.83 1.81 

11 1.90 1.85 1.81 1.83 1.82 

12 1.91 1.86 1.83 1.87 1.86 

13 1.92 1.88 1.85 1.86 1.83 

14 1.91 1.86 1.84 1.85 1.84 

15 1.94 1.89 1.84 1.87 1.84 

16 1.92 1.87 1.82 1.83 1.84 

17 1.92 1.86 1.85 1.90 1.88 

18 1.93 1.89 1.84 1.84 1.85 

19 1.91 1.87 1.84 1.87 1.84 

20 1.95 1.88 1.85 1.88 1.82 

21 1.92 1.86 1.82 1.84 1.84 

22 1.90 1.89 1.87 1.90 1.86 

23 1.93 1.91 1.86 1.88 1.88 

24 1.95 1.90 1.85 1.87 1.87 

25 1.92 1.88 1.84 1.88 1.86 

26 1.93 1.87 1.84 1.87 1.85 

27 1.93 1.87 1.84 1.84 1.85 

28 1.94 1.91 1.88 1.87 1.85 

29 1.99 1.92 1.87 1.89 1.85 

30 2.00 1.94 1.88 1.88 1.85 

C-4
Brownfield Landfill in Ft. Collins, Colorado

Table C-6. Methane Concentrations Found during the Downwind VRPM Survey Run 2.

Methane Concentration 

Loop (ppm) 

Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5 

1 1.70 1.84 1.83 1.85 1.84 

2 1.71 1.85 1.83 1.82 1.84 

3 1.72 1.85 1.82 1.84 1.84 

4 1.70 1.84 1.82 1.83 1.83 

5 1.70 1.85 1.82 1.84 1.84 

6 1.70 1.84 1.83 1.84 1.83 

7 1.70 1.83 1.82 1.83 1.83 

8 1.70 1.84 1.82 1.86 1.84 

9 1.71 1.85 1.83 1.86 1.84 

10 1.71 1.85 1.84 1.86 1.85 

11 1.72 1.85 1.83 1.84 1.84 

12 1.70 1.84 1.82 1.84 1.83 

13 1.70 1.84 1.82 1.84 1.84 

14 1.71 1.85 1.84 1.86 1.85 

15 1.73 1.86 1.85 1.91 1.86 

16 1.73 1.88 1.85 1.86 1.87 

17 1.74 1.87 1.86 1.89 1.87 

18 1.75 1.90 1.88 1.91 1.90 

19 1.77 1.90 1.88 1.90 1.91 

20 1.77 1.93 1.92 1.97 1.94 

21 1.81 1.95 1.92 1.94 1.93 

22 1.80 1.95 1.92 1.94 1.92 

23 1.80 1.94 1.92 1.94 1.92 

24 1.79 1.93 1.90 1.93 1.90 

25 1.78 1.92 1.90 1.92 1.91 

26 1.78 1.93 1.89 1.95 1.90 

27 1.78 1.92 1.90 1.96 1.91 

C-5