Bridgeton Landfill Data Review Update
Primarily Reflects Data and Documents Published on MDNR '.v Webpage for data collected in
December 2015
Introductory Remarks
The ORD 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 West lake 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 primarily collected during December 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 rates of CH4 (374 standard cubic feet per minute (scfm)), and CO2 (1,207 scfm)
from the flare were more than those measured with the GEM in November 2015. The
balance gas flow rate of 1,228 scfm in December was 20% less than in November 2015
(1,521 scfm).
• The average total flare flow rate of 3,042 scfm in December was 10% less than the
average total flare flow rate in November 2015 (3,364 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
GEW temperatures in December 2015 showed eight wells with a drop in temperature in the
earlier part of the month, accompanied by a positive applied pressure (> 2 inches water
column (" w.c.)) and high balance gas concentrations. This contrasts with trends from
November, which generally showed a large applied vacuum (> 2" w.c.). Data for the remaining
wells exhibited mostly steady or decreasing temperature trends when compared to November
2015. The maximum temperature measured in North Quarry wells was 148 °F (GEW-54), and
no wells exhibited increasing temperature trends.
Data from several new TMPs in the North Quarry were also analyzed: TMP-16 through 18, and
TMP-21 through 29. The TMP data showed temperatures in the North Quarry having mostly
steady trends across all depths. However, three TMPs (#16, #17, and #29) indicated decreasing
temperatures (> 2 °F decrease) at certain depths.
Similar to November 2015, two TMPs (#16 and #17) had depths with measured
temperatures > 160 °F. One TMP (#16) had depths with measured temperatures > 160 °F
in October 2015.
Collected Gas Quality
December data trends were similar to November 2015, with respect to balance gas results
but differed slightly in pressure measurements. The higher applied vacuum (> 2" w.c.)
prevalent in November carried over to seven wells in December, but the total number of
wells with this higher applied vacuum decreased. The applied vacuum for the remaining 10
wells can be characterized as 'limited vacuum' (< 2" w.c.), consistent with historical trends.
Eleven wells had balance gas concentrations > 10%, which is less than November (14 wells). In
nearly every case, laboratory measurements showed that the higher balance gas was composed of
N2. Neither the field data nor the laboratory data exhibited elevated O2 concentrations,
suggesting air intrusion may be occurring. Air (composed of 78% N2 and 20% O2) intrusion can
increase either/both N2 and O2 subsurface concentrations. N2 is typically used to show air
intrusion, as it is not consumed in the environment as quickly as O2.
Settlement
No settlement data were collected for the North Quarry in December 2015.
Neck Area
Temperature
TMP measurements were stable, compared to November 2015 data. Five TMP depths
showed a temperature decline in December 2015: TMP-2 (0-ft depth (-5.8°F)), TMP-4R (10-ft
depth (-4.9 °F)) and TMP-14, (41 -ft depth (-3.5 °F); 81-ft depth (-2 °F); 101 -ft depth (-3.3 °F)).
Data for December 2015 showed either steady or decreasing temperature trends in the
GIWs. Two wells (GIW-1 and GIW-6) exhibited steady trends, while the remaining 11
GIWs showed a declining temperature trend. Five GIWs (GIW-3 through 7) exhibited a
temperature decrease of approximately 30 °F based on the last reading in December. Two of five
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wells (GIW-3 and GIW-5) had low vacuum (< 2" w.c.). All 13 wells maintained a temperature <
100 °F. The GIWs exhibited more variability in vacuum pressures compared to November data,
with six GIWs drawing > 2" w.c.
December GEW data exhibited a mix of steady or decreasing temperature trends
compared to November 2015, with GEW-110 exhibiting a large drop in temperature
accompanied by low (< 2" w.c.) vacuum pressures. Three additional wells exhibited lower
vacuum when compared to historical data (GEW-10, GEW-38, GEW-109), which were
accompanied by elevated balance gas concentrations (except for GEW-10). GEW-109 was the
only well to maintain vacuum > 2" w.c. The maximum observed temperature in any of the Neck
Area wells was 166 °F, and the range of temperatures for GEWs in the neck area was 60 °F to
148 °F.
Heat Extraction System (HES) Evaluation
TMPs installed adjacent to GIWs retrofitted with the Heat Extraction System (HES, or cooling
loop system) were examined and compared to November 2015 TMP data from these locations.
The December 2015 TMP data displayed mostly steady and decreasing temperatures. Only one
TMP (#20) had increased temperatures (5.1 °F) at the 140-ft depth. The temperature decreases
were all generally < 2 °F, except for six TMPs that exhibited temperature declines > 2 °F at
varying depths.
• TMP-5-5N: -4.4°F at 20-ft.
• TMP-5-9S: -8 °F at 60-ft.
• TMP-10-5N: -4.1 °F at 20-ft.
• TMP-10-5S: -2.6 °F at 20-ft, -2.6 °F at 40-ft, -2.7 °F at 60-ft, -2.4 °F at 80-ft, and -3.0
°F at 100-ft.
• TMP-10-9N: -2.8 °F at 40-ft.
• TMP-10-9S: -2.0 °F at 40-ft and -2.3 °F at 100-ft.
The TMPs continued showing higher temperatures than the adjacent GIWs, and the TMPs closer
to the GIW generally had lower temperatures than those farther from the GIWs. Therefore the
data suggest that any cooling that does occur due to the HES is localized.
Generally, temperatures increased with depth in the Neck, with maximum measured values
ranging from 200 °F to > 250 °F, in some cases. At most depths, the northern TMPs (5-5N, 5-
9N, 10-5N, and 10-9N) showed temperatures < 200 °F, and less than temperatures measured in
the southern TMPs (5-5S, 5-9S, 10-5S, and 10-9S). In many cases, observed temperature
differences between southern and northern TMPs in the Neck Area were > 50 °F.
Collected Gas Quality
Six of 14 GEWs exhibited elevated balance gas concentrations at least once during
December 2015. O2 concentrations in these wells were low in comparison to the amount of
balance gas present, which suggests possible air intrusion.
All 13 GIWs exhibited elevated concentrations of balance gas and/or CO2. Balance gas
concentrations were elevated during the entire month, and the majority of GIWs had measured
concentrations > 20%. CH4 concentrations were generally < 20%.
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Settlement
Limited elevation points were measured in the Neck Area, therefore no assessment of settlement
rates were made in December.
South Quarry
Temperature
• No GEWs (with data) had temperatures > 200 °F.
• Thirty-two wells had temperatures ranging from 140 °F to 200 °F.
• Twelve wells had measured temperatures < 100 °F.
• Forty-eight wells maintained an applied vacuum >2" w.c. for the month.
• Two TMPs (#31 and #32) were examined. No temperature increases were noted for
these TMPs.
Collected Gas Quality
No GEWs in the South Quarry exhibited gas concentrations consistent with anaerobic
waste decomposition conditions.
Settlement
The maximum settlement amount in December was 1.28 ft, which is less than the 1.58 ft in
November 2015. Surface elevation points reported in December were compared to surface
elevation points collected in November 2015, and a volume difference was calculated by
analyzing surfaces created with both sets of data points using a computer-aided design (CAD)
program. The analysis showed a decrease in volume of approximately 16,000 yd3 from
November to December 2015. This is less than the 19,000 yd3 volume loss from October to
November 2015. This value should be considered an estimate since there were some settlement
points missing from this month's data and details on surface filling or removal activities were not
available in the site's monthly report narrative.
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