Bridgeton Landfill Data Review Update
Primarily Reflects Data and Documents Published on MDNR '.v Webpage for data collected in
October 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 October 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 (388 standard cubic feet per minute (scfm)), and CO2 (1,250 scfm)
from the flare were less than those measured with the GEM in September 2015. The
balance gas flow rate of 1,576 scfm in October was 18% less than in September 2015
(1,922 scfm).
• The average total flare flow rate of 3,522 scfm was about 12% less than the average total
flare flow rate in September 2015 (4,018 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
October 2015 temperature measurements in the GEWs showed two GEWs (GEW-44 and
GEW-45R) had decreasing trends, when compared to September data, while the remaining
21 GEWs maintained steady trends. Two wells, GEW-53 and GEW-54, had measured
temperature readings > 140 °F. GEWs had vacuums ranging from 2 inches water column (" w.c.)
to no vacuum. None of the wells maintained vacuum > 2" w.c. for the month.
Data from several new TMPs in the North Quarry (TMP-16 through 18, and TMP-21 through
29) were examined, and results indicated steady trends across all depths, compared to September
2015 data.
Only one TMP had temperatures > 160 °F (TMP-16) in October. The maximum temperature at
the other 11 TMP clusters ranged from 76 °F to 155 °F.
Collected Gas Quality
Overall, the GEWs exhibited expected CH4 and CO2 concentrations from anaerobic
conditions within the landfill, though there were a few wells that displayed elevated balance
gas concentrations, which are discussed below. As in previous months, many of the wells
had low or no applied vacuum, which confounds discerning trends. Five of 23 wells had
balance gas concentrations > 10%. One well (GEW-47R) had at least one balance gas
concentration reading that exceeded 20%.
Trace gas constituents were measured in 15 North Quarry wells. Fh and N2 concentrations were
> 10%) for three wells, which correlated with the field-measurement balance gas concentrations
at two wells, but not for GEW-03. These results suggest possible sampling errors. CO was
measured in two wells (GEW-53 and GEW-55), with concentrations of 64 ppm and 30 ppm,
respectively.
Settlement
No settlement data were collected for the North Quarry in October 2015.
Neck Area
Temperature
Only one TMP (TMP-10) exhibited increased temperatures. The remaining TMPs in the neck
showed steady or decreasing trends. The instances of decreased temperature were usually < 2°F,
with the exception of TMP-4R and TMP-14. These TMPs had decreases > 2°F at various depths
ranging from 10 ft to 101 ft. This suggests possible ambient effects, due to the fact these
readings are from thermocouples that are close to the surface. TMP-10 was the only one with a
temperature increase > 2 °F (at 13 ft depth).
October 2015 displayed a mix of decreasing and steady temperature trends in the GIWs,
with 7 wells showing decreased temperatures from the previous month; the remaining 6
wells were steady. All 13 GIWs maintained an approximately constant vacuum, with 10 wells
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drawing > 2" w.c. GIW-01 had measured temperatures > 140 °F, while the remaining 12 wells
all maintained temperatures < 100 °F.
Four of six GEWs displayed steady temperature data trends in October, compared to
September 2015. Additional observations include:
• GEW-10 and GEW-110 exhibited decreased temperatures from the previous month.
GEW-110 temperatures returned to historical trends.
• GEW-5 6R and GEW-109 had temperatures > 140 °F, reaching maximum readings of 180
°F.
• GEW-10, GEW-56R, GEW-109 and GEW-110 maintained vacuum throughout the entire
month, with GEW-10 and GEW-109 holding > 2" w.c. vacuum for the month.
Heat Extraction System (HES) Evaluation
TMPs installed adjacent to GIWs retrofitted with the HES (cooling loop system) were examined
and compared to September 2015 data. October 2015 displayed mostly steady and decreasing
temperatures (six locations with one or more depths exhibiting a decline). These instances of
decreased temperature were usually < 2 °F, but five TMPs exhibited temperature decreases > 2
°F:
• TMP-5-5N (-4.4 °F at 20 ft depth; -7.3 °F at 40 ft depth; -8.8 °F at 60 ft depth)
• TMP-5-9N (-3.2 °F at 20 ft depth; -3.7 °F at 40 ft depth; -4.2 °F at 60 ft depth)
• TMP-10-5N (-4.5 °F at 40 ft depth; -5.2 °F at 60 ft depth; -6.6 °F at 80 ft depth; -8.3°F
at 100 ft depth)
• TMP-10-5S (-3.2 °F at 100 ft depth)
• TMP-10-9N (-2.4 °F at 40 ft depth)
Increases in temperature were observed at three TMP locations. The TMPs that exhibited
increased temperatures > 2 °F at particular depths were:
• TMP-14R (+2.4 °F at 60 ft depth)
• TMP-20 (+2.5 °F at 140 ft depth)
• TMP-31 (+25 °F at 120 ft depth; +80.7 °F at 180 ft depth).
This TMP is located in the southern part of the Neck Area and could be considered to be
within the South Quarry. The temperature at the 180-ft depth increased from 178 °F to
259 °F from late September to early October, 2015. Although this is a relatively large
increase in a small time window, the temperature is consistent with other temperatures
measured in nearby TMPs in this depth range.
TMP data 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, indicating a
localized cooling effect from the HES.
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
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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 were > 50 °F.
Collected Gas Quality
Three of six GEWs (GEW-56R, GEW-109, GEW-110) in the Neck area continue to exhibit
elevated concentrations of both balance gas and/or CO2 resulting in decreased levels of
methane. The CO2 concentrations from these wells ranged from 10% to 56%, while balance gas
ranged from 39 to 72%. GEW-110 also displayed elevated levels of O2, with a maximum
reading of 17% for the month. This is consistent with previously-measured O2 levels for this
GEW.
All 13 GIWs exhibited elevated concentrations of balance gas and/or CO2, resulting in
decreased CH4 concentrations. Balance gas concentrations were elevated during the entire
month, with a majority of the GIWs having values > 20%. GIW-07 and GIW-08 had
measurements < 20%. The remaining 11 GIWs had concentrations ranging from 27% to 70%.
CH4 concentrations remained < 20% for 11 of the GIWs, and 10 of these wells were consistently
at < 10%). Elevated O2 levels (>10%) were measured at GIW-05, GIW-09, and GIW-12.
Settlement
Limited elevation points were measured in the Neck Area, thus no assessment of settlement rates
in the Neck Area are made here.
South Quarry
Temperature
• No GEWs with data had temperatures > 200 °F.
• Thirty-six GEWs exhibited temperature readings ranging from 140 °F to 200 °F.
• Fifteen of the GEWs exhibited sustained temperatures < 100 °F for the month.
• Forty-nine of the GEWs had consistent applied vacuum pressures > 2" w.c.
Collected Gas Quality
No GEWs in the South Quarry exhibited gas concentrations consistent with anaerobic
waste decomposition conditions.
Settlement
The maximum settlement amount in October 2015 was 1.75 ft, which is greater than the
maximum reported settlement amount of 1.36 ft in September 2015. Surface elevation points
reported in October 2015 were compared to surface elevation points collected in September, 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 of
approximately 23,000 yd3 from September to October 2015. This value should be considered an
estimate since details on surface filling or removal activities were not available in the site's
monthly report.
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