Bridgeton Landfill Data Review Update
Primarily Reflects Data and Documents Published on MDNR's Webpage for data collected
between June and July 2015
Introductory Remarks
The (3RD Engineering Technical Support Center (ETSC)
and their subcontractor reviewed data and reports at the
Missouri Department of Natural Resources (MDNR)
Bridgeton Landfill website. The purpose of the review
was to examine available reported data collected at the
landfill gas extraction wells (GEWs), gas interceptor wells
(GIWs), and temperature monitoring probes (TMPs) to
assess the presence and progression of any subsurface
oxidation event/heat-generating event occurring in the
South Quarry, North Quarry or the adjoining "Neck" area
(see figure on right for an approximate depiction of these
areas and the adjacent Westlake Landfill OU-1 cell). The
shaded areas shown in the figure are intended to provide a
quick reference to different areas of interest. This report
analyzes data collected during the m onths of June and July
2015.
The South Quarry and North Quarry landfill cells began the closure process in 2008 and 2010,
respectively. The landfill cells were covered with a 2-ft thick clay cap (with specified hydraulic
conductivity <1 * 10-5 cm/sec) overlain by a 1 -ft thick vegetative soil layer. An ethylene vinyl
alcohol (EVOH) flexible membrane cap was placed over the South Quarry, Neck Area, and a
portion of the North Quarry in 2013 and 2014. Work was initiated in the South Quarry at
various times in 2014 and 2015 to repair slopes that had subsided
This document provides a summary and discussion of data collected in North Quarry, Neck
Area, and South Quarry of the landfill. Observations on the flare data are also provided below:
• The flow rate of CH4 (430-446 standard cubic feet per minute (scfm)) and CO2 (1,538-
1,542 scfm) from the flare were less than that measured with the GEM in May 2015. The
balance gas flow rate had a range of 2,141-2,248 scfm in June and July 2015, which was
slightly more than in May (2,179 scfm).
• The average total flare flow rate had a range of 4,560-4,688 scfm in June-July 2015, with
May's average falling in between the range (4,655 scfm).
Flare data are subject to further examination, as subsequent meetings in December 2015 and
January 2016 indicate the flow measurements for the overall gas collection system and flares
were not accurate, and flow data for the mentioned systems were not accurately measured until
after March 12, 2015 (per MDNR). However, it is our understanding that flow data from
individual GEWs and GIWs were accurate throughout 2015.
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North Quarry
Temperature
Temperature measurements in the GEWs showed generally steady levels. Nearly all GEWs
showed some vacuum pressure, but most were less than 2 inches water column (" w.c.). Some
wells showed a slight temperature increase, but levels were generally consistent with historical
measurements. GEW-51 exhibited its highest recorded temperature (approximately 126 °F) but
gas quality data indicated normal anaerobic decomposition conditions.
• In June 2015, 21 GEWs showed generally steady temperatures compared to the
previous month, with 19 GEWs showing a temperature less than 140 °F:
GEW-02
GEW-07
GEW-43R
GEW-50
GEW-03
GEW-08
GEW-44
GEW-51
GEW-04
GEW-40
GEW-46R
GEW-52
GEW-05
GEW-41R
GEW-47R
GEW-55
GEW-06
GEW-42R
GEW-48
o GEW-49 exhibited a temperature decline of >10 °F towards the end of the
month, which resulted in temperature readings <100 °F.
o GEW-45R increased slightly when compared to May 2015 data. However,
even with the slight increase, temperatures still remained <100 °F.
• In July 2015, 22 GEWs exhibited generally steady temperatures compared to June,
and 20 GEWs had a temperature less than 140 °F:
GEW-02
GEW-07
GEW-43R
GEW-48
GEW-03
GEW-08
GEW-44
GEW-50
GEW-04
GEW-40
GEW-45R
GEW-51
GEW-05
GEW-41R
GEW-46R
GEW-52
GEW-06
GEW-42R
GEW-47R
GEW-55
o GEW-49 was the only well to exhibit an increase in temperature from the
previous month. Temperature readings showed that the temperature increased
by over 20°F, but remained less than 140 °F.
Most TMPs exhibited a decline in temperature of about 2-3 °F at the beginning of June. It is
unclear whether this is a true temperature decline or a reflection of the measurement device(s)
used. Beyond this observation, temperatures in TMPs were generally steady during June and
July, with slight decreases observed in some TMPs. The peak measured temperature occurred at
TMP-25 (approximately 160 °F). One TMP showed a temperature increase of about 4 °F (TMP-
29 at the 8-ft depth), but this appears to be a reflection of ambient temperature changes based on
the proximity to the surface.
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Collected Gas Quality
The GEWs exhibited CH4 and CO2 concentrations from typical anaerobic decomposition,
although there were a few wells which displayed elevated balance gas concentrations.
• In June 2015, nine out of 23 wells had balance gas concentrations >10%, with four wells
(GEW-05, GEW-44, GEW-47R, and GEW-49) having balance gas concentrations >20%.
GEW-49 had a maximum balance gas concentration of 48.4%, which is higher than its
historical measurements. Laboratory analysis was conducted at 14 of the 23 wells. H2 and
N2 concentrations were >10% for 5 of the wells, which generally agrees with field
measurements. Three wells had detected CO levels (GEW-08, GEW-53, GEW-54), all
less than 100 ppm.
• In July 2015, 11 of the 23 wells exhibited balance gas concentrations > 10%, with four
wells (GEW-05, GEW-06, GEW-47R, GEW-49) exhibiting concentrations >20%.
Settlement
No settlement data were collected for the North Quarry from June-July 2015.
Neck Area
Temperature
Data from June through July 2015 show that four TMPs exhibited increased temperatures,
though only at particular depths. The remaining depths typically showed decreased temperature
(>2°F decrease) levels compared to May 2015 data. The remaining TMPs typically showed
either steady or decreasing trends in temperature for some depths or did not have any data
recorded. Similar to North Quarry TMPs, many of the Neck Area TMPs exhibited an abrupt,
mostly uniform decline of about 5 °F in early June 2015, potentially reflecting an adjustment in
the measurement device(s).
TMPs that showed a temperature increase of greater than 2 °F during June-July 2015 were as
follows:
• TMP-2 (+9.8°F at 0 ft depth)
• TMP-4R (+4.1 °F at 10 ft depth)
• TMP-6 (+11,6°F at 15 ft depth)
• TMP-14 (+5.5°F at 61 ft depth)
June and July 2015 displayed mostly steady trends in temperature with some decreasing
cases for the GIWs. 10 of the 13 GIWs maintained constant vacuums through the entire 2
month period, with six of those wells having constant vacuum >2" w.c. Many of the GIWs had
substantially increased vacuum relative to historical values from 2014, with several GIWs with
vacuum as much as -30" w.c. The increased vacuum appeared to coincide with the operation of
the pilot heat extraction system (HES). Some of the monthly trends observed in the GIWs were:
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• In June 2015, five of the 13 GIWs exhibited steady temperatures when compared to the
May 2015 data. Six GIWs exhibited fluctuating temperature readings throughout the
month (e.g., a temperature swing of 20 °F from one measurement to the next). GIW-12
and GIW-13 decreased in temperature from the previous month - this is consistent with
previous monthly temperature readings/trends.
• In July 2015, six of the 13 GIWs exhibited steady temperatures when compared to the
June 2015 data. Another six of the 13 GIWs showed a decrease in temperature from the
previous month, with three of these wells having an HES installed (GIW-09, GIW-11, and
GIW-12), suggesting the HES operation resulted in a decline in the extracted gas
temperature. One well (GIW-04) had an increased temperature from the previous month,
where temperatures started off lower in the beginning of month, but increased to a peak of
103.9°F during the last reading of the month. Additionally, GIW-01 was the only well to
exhibit a temperature reading >140°F.
GEWs in the neck area exhibited mainly steady temperatures over the June to July 2015
duration. Other observations made for these GEWs are discussed further below:
• No readings were taken during the month of June for GEW-109 and GEW-110, therefore
all July 2015 data were compared to May 2015 data for the analysis.
• GEW-10 is the only well that maintained temperatures below 100°F during both months.
• GEW-56R and GEW-109 maintained temperatures above 140°F during their readings,
which is consistent with the past readings taken from these wells.
• GEW-109 was the only well to maintain a vacuum >2" w.c.
Collected Gas Quality
GEW-56R, GEW-109, and GEW-110 exhibited elevated concentrations of both balance gas
and CO2 (>30%) resulting in decreased levels of methane. GEW-109 and GEW-110 only had
data available for July. The remaining GEWs showed CH4 and CO2 concentrations consistent
with anaerobic conditions across the two-month period.
All but GIW-07 and GIW-08 exhibited high concentrations of balance gas (>20%) during the
entire two-month period. Elevated balance gas concentrations in the other 11 GIWs ranged from
34.2% - 74.3%). CO2 readings were also elevated, which resulted in low CH4 concentrations for
all GIWs. Most CO2 concentrations were greater than 50%, while CH4 typically remained below
20%), with the exception of GIW-07 which had a maximum CH4 reading of 38.7%> in July.
Elevated O2 levels occurred at specific wells each month. In June, GIW-05 and GIW-09 had
maximum O2 readings of 18.6%> and 12%, respectively; in July, GIW-05 and GIW-12 had
maximum O2 readings of 13.8%> and 10.9%>, respectively.
Settlement
Limited surface elevation data were available in the neck - some areas (northeast and northwest
portions of the surveyed area) showed slight elevation increases, while other areas showed a
surface settlement of less than 1 ft.
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South Quarry
Temperature
• One GEW had a temperature greater than 200 °F for both months (GEW-24A
(201.6°F)).
• 17 and 36 GEWs had temperatures ranging between 140 °F to 200 °F in June and July
2015, respectively.
• 10 GEWs exhibited temperatures readings <100 °F in June, while there were 16 GEWs
in July 2015.
• Many of the wells had a vacuum >2" w.c. during each month, though it did not seem to
have any drastic effect on the temperature. Twenty-eight of the GEWs were able to
maintain vacuums > 2" w.c. during the month of June, while 43 GEWs maintained
these vacuums in July.
Collected Gas Quality
Between June and July 2015, only four of 64 GEWs monitored (GEW-120, GEW-124,
GEW-149, and GEW-154) in the South Quarry exhibited gas concentrations consistent
with anaerobic waste decomposition conditions.
• CH4 readings revealed consistently low readings with 64 GEWs having CH4 concentrations
less than 30%. GEW-120, GEW-124, GEW-140, GEW-149, and GEW-154 were the only
wells with methane concentration data greater than 30%. 51 monitored GEWs exhibited
concentrations <10% during the month of July.
• CO2 readings revealed high concentration levels (>30%) with the majority of wells having
concentrations ranging between 50-70%>. No well exceeded 70%. Only 11 GEWs exhibited
consistent concentration <30% over the two-month period.
• Balance gas typically remained between 30-50%, with some GEWs exhibiting concentrations
>50%), measuring up towards 80% in both June and July.
• As with the previous months, O2 concentration levels typically remained below 5%, however
there were 14 GEWs that did exhibit elevated O2 levels >10%, which include:
GEW-21A
GEW-61B
GEW-89
GEW-148
GEW-26R
GEW-67A
GEW-116
GEW-154
GEW-37
GEW-84
GEW-136
GEW-38
GEW-85
GEW-146
Settlement
The maximum monthly settlement occurred in June, with a maximum decrease in elevation of up
to 2.2 feet, while July had a maximum settlement of 1.8 feet, which is more than the settlement
amount observed in May 2015.
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