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Landfill Gas Migration: A Method for Remediation
By: Sara Hoovestol, P.G.
What Are We Going To Cover:
▪ Site Background
▪ Historical Landfill Gas (LFG) Measurements
▪ Investigation and Design of Remediation Method
▪ Construction of Trench
▪ How Did It All Turn Out
▪ Lessons Learned
Site Background
Overview of the Site
▪ Bullets
▪ Bullets
▪ Bullets
Historical LFG Measurements
Historical LFG MeasurementsMethane Monitoring Results
June 2011-October 2013
GW-1R
Date
Percent
Methane by
Volume
in Air
Percent of
Lower
Explosive
Limit (LEL
for Methane)
6/20/2011 32.7 654
9/28/2011 26.5 530
12/13/2011 14.5 290
3/5/2012 21.1 422
6/20/2012 21.4 428
10/25/2012 10.1 202
11/27/2012 1.7 34
3/14/2013 16.5 330
6/19/2013 28.7 574
9/10/2013 26.7 534
Investigation and Design of Remediation Method
Investigation
▪ Previously installed passive gas vents are not adequate
▪ Weaver Consultants Group developed a gas sounding method
▪ Gas sounding results were compared to the gas probe boring log
▪ Determined a general correlation between the sounding result interval and an angular gravel/sandstone cobble interval in the boring log
Findings and Design
▪ The results of the investigation indicated LFG gas appeared to be migrating approximately 18 feet below ground surface.
▪ Weaver Consultants Group proposed the installation of a gas cutoff trench
▪ Design Objective:
▪ Induce vacuum at the depth of gas migration
Design Drawing
Construction of Trench
Digging The Trench
Placement of 80-mil HDPE
Pipe Being Placed in Trench
Trench with Gravel
Trench Being Backfilled
Completed Trench
How Did It All Turn Out(The Results)
Recent Monitoring ResultsMethane Monitoring Results
October 2013-November 2018
GW-1R
Date
Percent
Methane by
Volume
in Air
Percent of
Lower
Explosive Limit
(LEL for
Methane)
10/15/2013* 5.7 114
3/27/2014 0 0
6/16/2014 0.1 2
9/23/2014 0 0
11/4/2014 0 0
3/26/2015 0 0
6/26/2015 0 0
9/24/2015 0 0
11/3/2015 0 0
3/17/2016 0 0
6/9/2016 0 0
9/23/2016 0 0
11/15/2016 0 0
3/16/2017 0 0
6/22/2017 0 0
9/15/2017 0 0
11/1/2017 0 0
3/14/2018 0 0
6/20/2018 0 0
9/20/2018 0 0
11/7/2018 0 0
Methane Monitoring Results
June 2011-September 2013
GW-1R
Date
Percent
Methane by
Volume
in Air
Percent of
Lower
Explosive
Limit (LEL
for Methane)
6/20/2011 32.7 654
9/28/2011 26.5 530
12/13/2011 14.5 290
3/5/2012 21.1 422
6/20/2012 21.4 428
10/25/2012 10.1 202
11/27/2012 1.7 34
3/14/2013 16.5 330
6/19/2013 28.7 574
9/10/2013 26.7 534
Recent Monitoring ResultsMethane Monitoring Results
2016-2018
Trench Vents (near GW-1R)
DateVent
Number
Percent
Methane by
Volume
in Air
Percent of
Lower
Explosive
Limit (LEL
for
Methane)
3/17/2016
1 0 0
2 0 0
3 0 0
6/9/2016
1 0.9 18
2 0 0
3 0 0
9/23/2016
1 0 0
2 0 0
3 0 0
11/15/2016
1 0 0
2 0 0
3 0 0
3/16/2017
1 0.8 16
2 0 0
3 0 0
6/22/2017
1 4.7 94
2 0 0
3 0 0
Methane Monitoring Results
2016-2018
Trench Vents (near GW-1R)
DateVent
Number
Percent
Methane by
Volume
in Air
Percent of
Lower
Explosive
Limit (LEL
for
Methane)
9/15/2017
1 6.3 126
2 0 0
3 0 0
11/1/2017
1 0.4 8
2 0 0
3 0.2 4
3/14/2018
1 0 0
2 0 0
3 0 0
6/20/2018
1 10.9 218
2 0 0
3 0 0
9/20/2018
1 0 0
2 0 0
3 0 0
11/7/2018
1 0 0
2 0 0
3 0 0
Lessons Learned
Lessons Learned
▪ Importance of quality boring logs
▪ Do it once
▪ Proper construction quality assurance
Questions?Contact Information:
Sara Hoovestol, P.G.
720-529-0132
