Unitsd States Rtgion VJII July 1981
Environmental Prowction 1860 Lincoln Street . Report M«»J
Agency Denver, Colorado 80295 908/6-81-002
Solid Watt
LANDFILL GAS AND LEACHATE
MONITORING: HELENA, MONTANA
- A TECHNICAL ASSISTANCE PANELS
PROGRAM REPORT
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^LANDFILL GAS AND LEACHATE MONITORING:
HELENA, MONTANA - A TECHNICAL ASSISTANCE PANELS PROGRAM REPORT
Prepared for:
U.S. Environmental Protection Agency
Region VIII
1860 Lincoln Street
Denver, Colorado 80295
Prepared by:
Fred C. Hart Associates, Inc,
Market Center
1320 17th Street
Denver, Colorado 80202
July, 1981
NTIS Report No. 908/6-81-002
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Public Law 94-580 - October 21, 1976
Technical assistance by personnel teams. 42 USC 6913
RESOURCE RECOVERY AND CONSERVATION PANELS
SEC. 2003. The Administrator shall provide teams of personnel, including
Federal, State, and Local Employees or contractors (hereinafter referred to as
"Resource Conservation and Recovery Panels") to provide technical assistance on
solid waste management, resource recovery, and resource conservation. Such
teams shall include technical, marketing, financial, and institutional special-
ists, and the services of such teams shall be provided without charge to States
or local governments.
This report has been reviewed by the Project Officer,
EPA, and approved for publication. Approval does not
signify that the contents necessarily reflect the
views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for
use.
Project Officer: William Rothenmeyer, EPA Region VIII
DISTRIBUTION STATEMENT
The report is available to the public through the National Technical Infor-
mation Service, U.S. Department of Commerce, Springfield, Virginia, 22161.
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LANDFILL GAS AND LEACHATE MONITORING HELENA, MONTANA
ENVIROMENTAL PROTECTION AGENCY REGION VIII
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TABLE OF CONTENTS
PAGE
List of Tables i
List of Figures 11
I. EXECUTIVE SUMMARY 1
Potential Problems Associated with Municipal Landfills 1
The Helena, Montana Case 1
Summary of Conclusions 3
II. INTRODUCTION-METHANE AND LEACHATE PRODUCTION IN
MUNICIPAL LANDFILLS 4
Characteristics of Methane in Landfills 4
Production of Leachate in Landfills 12
III. STUDY AREA DESCRIPTION J9
Helena Landfill Site 19
Landfill Site Geology 22
Potential Methane Production from the Helena Landfill 23
Ground Water Contamination from the Helena Landfill 24
IV. METHODS 25
Field Investigation 25
Samp! 1 ng 30
V. DATA ANALYSIS 34
Methane Gas Analysis 34
Leachate Analysis 39
Statistical Significance of the Data 45
VI. CONCLUSIONS AND RECOMMENDATIONS 47
Methane Gas Generation 47
Leachate Contami nation 49
VII. REFERENCES 53
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LIST OF TABLES
Table Number Title Page Number
1 Chemical Characteristics of Municipal
Landfill Leachate 15 .
2 Chemical Tests Employed by the Colorado Depart-
ment of Health on Landfill Leachate 17
3 Results of Gas Measurements from Barhole
Punch Tests at the Helena Landfill 31
4 Results of Gas Measurements from Monitoring
Wells at the Helena Landfill 36
5 Chemical Test Parameters Used in the
Helena Landfill Study 40
6 Results of the Chemical Analyses 41
7 Water Table Elevations 44
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LIST OF FIGURES
Figure Number Title Page Number
1 Landfill Gas Production During the Four
Principal Stages of Solid Waste
Decomposition 5
2 Limits of Flammability of Methane in Mixtures
of Air and Carbon Dioxide: The Methane
Explosive Envelope 7
3 Relationship Between Levels of Gases and
Flammability of Mixtures of Methane, Air
and Nitrogen: Methane's Envelope of
Explosivity 8
4 Water Balance and Leachate Production In
Landfills 13
5 The Helena Landfill Site Showing Barhole
Punch Test and Monitoring Well
Locations 20
6 Cross Section of Monitoring Well 28
7 Well Logs from the Seven Monitoring Wells
Placed in the Helena Landfill 29
11
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I. EXECUTIVE SUMMARY
Potential Problems Associated with Municipal Landfills
Leachate contamination of ground water and methane gas production are po-
tential problems associated with solid wastes deposited in municipal landfills.
Ground water contamination and methane gas generation may present particularly
acute problems in older landfills which were originally sited on the outskirts
of urban areas. As the urban areas expand, former landfill sites become at-
tractive for building sites and may be used for residences, schools, and parks.
Urban expansion onto abandoned landfill sites increases the likelihood that
contaminated ground water and/or methane gas may jeopardize the health and
well being of people living in or using the areas. Analyzing and eliminating
the potential hazards posed by landfill areas situated within urban boundaries
may be difficult for small or medium size cities which may not have the re-
sources or expertise to solve these problems. This report presents an example
of how ground water contamination and methane gas generation problems from
urban landfills may be identified and monitored with relatively little expense.
The Helena, Montana Case
The City of Helena, Montana and the Montana Department of Health and Envi-
ronmental Sciences' Solid Waste Management Bureau (SWMB) are concerned about
the possible existence of ground water contamination and methane gas migration
from a landfill located within the Helena city limits.
The State of Montana requested the assistance of the Environmental Protec-
tion Agency (Region VIII) to identify the existence and extent of ground water
contamination and methane gas production from the Helena site. EPA granted the
request under authority of Section 2003 (Panels) of the Resource Conservation
and Recovery Act which states "the Administrator shall provide teams of person-
nel, including Federal, State and local employees or contractors to provide
technical assistance on solid waste management, resource recovery, and resource
conservation." Fred C. Hart Associates, Inc., EPA Region VIII's designated
Panels contractor performed the study. Tasks which were performed to satisfy
this request include the following:
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o preliminary identification of landfill methane gas hazards
o preliminary identification of ground water contamination by leachate
from the sites
o identification of the threats to public health and the environment
posed by ground water contamination and methane gas migration
o discussion of the potential for the recovery of methane from the
landfill for use as an energy fuel
The Helena landfill site has been used for the disposal of solid waste for
about fifty years. Open burning was the principal waste disposal method at the
site prior to 1970. Burning was halted in 1970 and sanitary landfill practices
began. These practices consisted of the placement and compaction of waste in
large cells. Refuse deposited at the site since 1970 consists mostly of
household wastes. Construction debris has been deposited in the southern
section of the landfill site. Household refuse may have been placed above the
construction debris. The southern section has been covered with soil and
reclaimed. The waste deposited at the site is covered daily. The Helena
landfill is in compliance with all local, State and Federal regulations.
A site monitoring project was established in cooperation with the State of
Montana and City of Helena officials. A barhole punch survey was performed
initially to delineate areas of methane gas concentration for the positioning
of permanent monitoring wells. The barhole punch test was conducted within the
landfill boundaries and on adjacent areas. Monitoring wells were drilled
following the completion of the barhole punch survey. Gas and ground water
samples were taken from the wells for laboratory analysis.
A single set of samples was collected and analyzed for methane and leachate
levels. This preliminary analysis was performed to establish the general
parameters of methane and leachate problems.
Initial data obtained from the barhole punch survey and the monitoring
wells are presented and analyzed in this report. Recommendations for the
-------
mitigation of methane and leachate hazards and the potential for using methane
as a fuel are Included.
Sunmary of Conclusions
Methane Gas Generation. Preliminary findings indicate that only a moderate
amount of methane gas is being generated within the inactive landfill area.
The migration of methane gas from the landfill appears to be minimal. Recovery
of the methane gas for use as a fuel is not economically feasible at the
present time. The lack of volume of fill precludes the installation of any
methane recovery system. Automated methane monitoring systems (alarms) should
be installed in two buildings located near the landfill site (YMCA and Armory)
to ensure that methane levels do not present a safety hazard.
Leachate generation. Leachate from the Helena landfill does not appear to
have contaminated ground water to a discernible degree or to pose a human
health hazard. Preliminary results from tests on ground water samples obtained
from wells upgradient of the landfill site, within the landfill site, and
downgradient from the landfill site indicate that leachate migration from the
disposal site has not occurred.
Conclusions drawn from this initial effort are preliminary and not based on
a statistically significant number of samples. A long-term monitoring program
should begin on the landfill site to verify the results of this study. Results
from further sampling and testing should be used to design permanent methane
gas and leachate monitoring programs. Discontinuing the operation of the
Helena landfill due to its proximity to an urban area will not mean the cessa-
tion of methane gas and leachate generation and migration problems. Recommend-
ations contained in this report apply regardless of the operational status of
the Helena landfill.
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II. INTRODUCTION - METHANE AND LEACHATE PRODUCTION IN MUNICIPAL LANDFILLS
Characteristics of Methane in Landfills
Stages of decomposition 1n landfills. Municipal landfills typically con-
tain a mixture of solid wastes including paper, wood, plastics, glass, living
organisms, and ferrous and non-ferrous metals. After the waste is deposited,
microbial processes begin to break down the organic matter. Moisture and warm
temperatures accelerate the microbial decomposition of organic matter. Most
sanitary landfills have moisture levels around 25 percent. Optimum moisture
levels for methane production in landfills range between 60 to 80 percent (1).
Temperatures within landfills during the anaerobic decomposition stages range
between 90° and 110° F. Ambient air temperatures below 50° F. result in sig-
nificant decreases in methane production (1). However, methane production can
occur at temperatures lower than 50°F. Frozen ground surfaces increase the
potential for methane to move laterally beneath the landfill surface and may
contribute to methane problems which are usually associated with warmer temper-
atures.
There are four principal stages in organic decomposition in solid waste
landfills (see Figure 1). The first or aerobic stage requires oxygen. During
this stage organic decomposition is an exothermic reaction which liberates ad-
ditional heat to fuel further decomposition. The availability of oxygen also
determines the rate of organic decomposition. Normally, microbial action in
solid waste landfills rapidly depletes available oxygen supplies unless supple-
mental oxygen is introduced. The absence of oxygen halts the oxidation pro-
cess.
The latter three, or anaerobic (oxygen-free), stages occur as the oxygen
supply in the landfill mass is depleted. Stage II, the first part of the an-
aerobic decomposition, occurs without the production of methane. Carbon
dioxide and hydrogen are the principal end products produced during this
phase. Methane is produced in increasing quantities in Stage III. Stage III
begins six months to several years after initial landfill placement (4). The
fourth stage of decomposition is marked by the relatively steady-state produc-
tion of methane.
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FIGURE 1. LANDFILL GAS PRODUCTION DURING
THE FOUR PRINCIPAL STAGES OF SOLID
WASTE DECOMPOSITION
z
o
O 3
0. o
2 >
O „
O J
3*
(0
IOO
90
ao
70
60
50
40
20
10
I 1 II
1
III
TV
l!
'i /
-W-
y
40%
/
N
• TIME AFTER PLACEMEN'
I. AERO8IC
it. ANAtSCaiC, NON - METViANCGc.NIC
III. ANAcSCSIC, METHANCGcNiC, UNSTEADY
IV. ANAtSQSIC, V£THANOG£NiC, STEAOY
Source: Farquhar and Rovers (3),
5.
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Many site-specific variables determine the rates of solid waste decomposi-
tion and the onset of the decomposition stages. Tests on a fixed volume of re-
fuse in a sealed tank show that over two years are necessary to achieve the
anaerobic stage IV where methane production occurs at a constant rate (2).
Decomposition of solid waste in anaerobic (oxygen-free) conditions yields
methane gas as the principal end-product. Other end-products from the anaero-
bic decomposition of solid waste includes alcohols, aldehydes, and sulphur, ni-
trogen, iron, and manganese compounds. Optimum conditions for anaerobic decom-
position in solid waste landfills include the absence of oxygen, the tempera-
ture of the landfill mass ranging between 85° and 1008F, pH of the landfill
ranging between 6.8 and 7.2, the absence of toxic materials, and the moisture
content of the landfill greater than 40 percent (1).
Gases produced in landfills can migrate upward or outward, depending on the
porosity of the soil or the impermeability of the soil cover. Site-specific
gas migration is influenced by numerous factors including soil characteristics,
climate, and soil surface conditions.
Hazards. All landfills produce methane. The generation of methane from
solid waste landfills presents a potentially significant hazard to people liv-
ing in the vicinity of the disposal site. Potential fire, explosion, asphyxia-
tion hazards, and vegetation kills are associated with the production of meth-
ane gas in landfills. Public safety may be endangered if methane accumulates
in combustible or explosive concentrations.
Methane is explosive in concentrations in the atmosphere of between five
and fifteen percent (see Figure 2). Concentrations of methane lower than five
percent are not enough to support an explosion. Concentrations of methane in
the atmosphere higher than fifteen percent mean that too little oxygen is
available to support an explosion. The five to fifteen percent range is called
the methane flammable envelope (see Figure 3). An enclosed combustion chanter
or confined area where methane can collect are required before methane will ex-
plode.
Landfill methane is usually produced in concentrations above the explosive
range. Landfill methane will always pass through the explosive range when dil-
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02 IN ORIGINAL ATMOSPHERE PERCENT
ZO 19 19 iT 16 13
FllAMMABLE
0 3 10 19 20 26 3O
CARSON OIOXIOE IN ATMOSPHERE, PERCENT
FIGURE 2. LIMITS OF FLAMMABILITY OF METHANE
IN MIXTURES OF AIR AND CARBON DIOXIDE:
THE METHANE EXPLOSIVE ENVELOPE
Source: Farquhar and Rovers (3).
COPYHIGH T! AW fTTfh r/ (;.«. (;o»H)
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LIMITS OF INDIVIDUAL GASES AND VAPORS
2
lu
U
•
x
o
22
20
!•
19
14
12
10
' . I I
Miiturvt wfwcD con not b«
oroductd from m«fhor» ond air
Ccpoblt or forming flommobk
. cir(conrairrtaDmucri rrxfhoo* to 8ipto6« p*r
Nor caoooM o/
forming flommool*
mixtures wif.i air
\
a a 10 12 i4 i a it
.METHANE, PERCENT
20
FIGURE 3. RELATIONSHIP BETWEEN LEVELS OF GASES,
AND FLAMMABILITY OF MIXTURES OF METHANE,
AIR, AND NITROGEN: METHANE'S ENVELOPE OF
EXPLOSIVITY
Source: Farquhar and Rovers (3).
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uted with air. There is usually no explosion when methane concentrations are
within the explosive range because of the lack of a flame source (spark, etc.)
in the landfill.
Explosions have been known to occur because of landfill methane. Explo-
sions occur most frequently when methane concentrates in poorly ventilated
areas. Methane can migrate subterraneously great distances through permeable
media - porous soils, trench backfills, utility or drainage corridors - and
collect in poorly ventilated structures, sanitary and storm sewers, etc.
Various site specific conditions will determine the level of the methane
explosion hazard. These include the type of landfill cover, type of surround-
ing soil, amount of methane produced, ambient air temperatures, precipitation
and landfill moisture content, air pressure, atmospheric turbulence, and the
presence or absence of conduits or barriers (1).
Production of Methane In Landfills. An anaerobic condition in a landfill
is the most critical factor in determining the production of methane. Waste
treatment (compaction, shredding, deposition in cells) accelerates the reduc-
tion of available oxygen and increases the timing of anaerobic conditions.
However, if methane is recovered faster than it is generated, air may infil-
trate through the landfill cover and slow the generation of methane. The in-
filtration of air into the landfill mass usually occurs in landfills which are
unable (not deep enough) to support a high methane recovery rate.
The depth of the landfill is another important factor in determining the
production of methane. Landfills with depths greater than 100 feet are best
able to support an adequate methane recovery system. Generally, 30 to 40 feet
of fill are necessary to support a minimum, but uniform, methane production and
recovery system (5, 6, 7). Compaction tends to lower initial landfill gas and
leachate production rates by decreasing the landfill waste volume and
increasing the waste density. This results in a longer period of methane and
leachate production.
Potential for Methane Migration. Methane will normally migrate upward be-
cause of its relatively low density.However, when upward movement is restrict-
-------
ed, the gas will tend to migrate laterally along paths of low resistance to a
location where upward movement is possible. Conditions which reduce the po-
tential for upward movement increase the possibility of horizontal migration.
Frost or heavy precipitation tend to fill or close the soil voids, causing the
soil to become less permeable and increase the potential for lateral gas move-
ment. Layers of clay or other impermeable materials placed near the surface of
the landfill or within the landfill will tend to increase lateral gas migra-
tion. The potential for methane migration is roughly estimated at 10 feet of
lateral movement for each foot of landfill depth (5, 8).
The migration of gas beyond the limits of landfills is a common occurence.
Uncontrolled migration of methane gas is capable of producing hazardous condi-
tions in structures, excavations and underground conduits. Gas migration oc-
curs through convection and diffusion. Convection is the movement of gas in
response to pressure gradients; diffusion is the movement of gas from areas of
higher gas concentration to areas of lower concentrations.
Gas flows through a soil mass in a fashion similar to water movement.
Soils having a high void ratio, such as sands and gravels, are conducive to gas
migration. Low permeability soils, such as silts and clays, tend to restrict
gas migration. The actual amount and extent of gas migration from landfills is
largely dependent on the hydrogeologic environment of the site. Landfill con-
structed in sand and gravel environments have more vertical and lateral move-
ment of gases than landfills built in an impervious soil environment. Since
methane is relatively insoluble in water, the presence of ground water signifi-
cantly decreases gas migration.
Natural ventilation of any methane gas produced occurs to varying degrees
during the summer months. Such natural ventilation will be enhanced by the
course-grained composition of the cover soil. However, potential for off-site
migration will tend to increase during the winter months due to frost closing
the voids in the cover material which limits vertical ventilation and encour-
ages horizontal migration.
Migrating methane gas may enter structures through cracks in the floor
slabs or foundation walls, joints in the floor slab or around structural mem-
10
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anaerobic stage of decomposition, gas concentrations normally range between 40
to 50 percent carbon dioxide and between 45 to 70 percent methane (4, 5, 6).
Average heating values for recovered methane gas from landfills are typically
between 400 and 600 British thermal units (Btu) per standard cubic foot (scf).
The recoverability of methane gas from landfills depends upon the combination
of gas production factors mentioned above and the time elapsed since the
disposal of the solid waste. Reports have shown that methane gas in landfills
may be generated at rates between 0.06 and 0.23 scf/pound of solid waste per
year (6).
Production of Leachate in Landfills
Leachate is produced in solid waste landfills by the introduction of sup-
plemental moisture, either through the infiltration of precipitation, or the
contact of the wastes with ground or surface waters. In a properly sited land-
fill, however, the infiltration of precipitation will be the primary manner in
which water can enter the body of the landfill. Solid waste decomposition also
produces water as one of its principal end-products, although a certain amount
of water will be absorbed by the solid waste as it decomposes.
Water Balance Formula. The formation of leachate within a landfill can
best be illustrated by EPA's water balance formula for estimating percolation
rates through a landfill (9). Figure 4 illustrates the components of the water
balance formula. The water balance concept is based upon the relationship
between precipitation, evapotranspiration, surface runoff, and the water
storage characteristics of both the overlying soil and the solid waste
material. Percolation will occur under those conditions where the amount of
infiltrating water (derived from either direct precipitation or surface water
which flows onto the landfill from adjoining higher ground) exceeds the amount
necessary to satisfy actual evapotranspiration and the soil and solid waste
water retainment capabilities. This water which percolates through the
landfill can move downward, under gravity, into the native soil beneath the
landfill. The concept is illustrated schematically in Figure 4.
Ground Water Contamination. Ground water contamination from landfill lea-
chate is a distinct possibility depending on how close the water table exists
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FIGURE 4. WATER BALANCE AND LEACHATE
PRODUCTION IN LANDFILLS
ACTUAL
EVAPOTRANSPIRATION
PRECIPITATION
SURFACE RUNOFF
SOIL MOISTURE STORAGE
t
I PERCOLATION
!SOLID WASTE CELLS
ISOLID WASTE MOISTURE STORAGE;
TEACHATE
/VIRGIN GROUND
Source: EPA (9)
13
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below the base of the landfill. Although the water-balance method is useful
for predicting the quantity of percolate which can migrate downward from a
landfill, it does not allow for a prediction of the actual quality of the water
(either in terms of concentration or constituents present) following contact
with the waste. Water quality can only be determined through a sampling and
analysis program in which representative ground water samples are obtained from
monitoring wells.
As the percolate migrates downward through the various soil and waste
layers in the landfill, it generally shows a net gain in concentration of dis-
solved constituents; however, it may lose some individual ions from cation ex-
change or other chemical reactions which occur en route. Leachate degradation
of groundwater poses significant health hazards if the water is used for domes-
tic or agricultural purposes. Contaminated groundwater may be tapped by wells,
may be discharged to surface water or may emerge on the surface downgradient
from the disposal site.
Leachate Characteristics. The quality characteristics of leachate depend
upon many site-specific variables. Major factors which determine the make-up
of leachate are: 1) time since the deposition of the solid waste; 2) quantity
and distribution of moisture; 3) temperature; 4) solid waste characteristics
(the principal components of the waste and disposal methods used); and 5) geo-
logy and geohydrology of the site. Many of the chemical components of leachate
are common to all municipal waste sites. However, certain heavy metals or syn-
thetic organic compounds may be present if wastes other than typical municipal
refuse have been deposited at the site. These atypical compounds, usually of
an industrial origin, may include such diverse compunds as pesticides, PCB's
and organic solvents. Under current Federal and State regulations, wastes
which have been determined to be hazardous must be disposed of in secure facil-
ities other than municipal landfills. It is not uncommon for these wastes to
have been deposited in older municipal landfills prior to the advent of the
regulations.
Table 1 shows the typical chemical constituents found in landfill leachate,
along with ranges of concentrations observed by several researchers. Several
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TABLE 1. CHEMICAL CHARACTERISTICS OF
MUNICIPAL LANDFILL LEACHATE
Constituent
Chloride (Cl)
Iron (Fe)
Manganese (Hn)
Zinc (Zn)
Magnesium (Mg)
Calcium (Ca)
Potassium (K)
Sodium (Na)
Phosphate (P)
Copper (Cu)
Lead (Pb)
Cadmium (Cd)
Sulfate (SO.)
Total M
Conductivity (Amhos)
TOS
TSS
pH
Alk as CaCO,
Hardness tot.
BODr
COO
Range*
(mg/l)
34-2,800
0.2-5,500
.06-1,400
0-1,000
16.5-15.600
5 -A, 080
2.8-3,770
0-7,700
0-15*1
0-9-9
0-5.0
--
1-1,826
0-1, 416
--
0-42,276
6-2.685
3.7-8.5
0-20,850
0-22,800
9-5*1,610
0 -.89, 520
Range +
(mg/l)
100-2, 400
200- I, 700
—
1-135
—
—
—
100-3,800
5-130
--
--
—
25-500
20-500
--
--
—
4.0-8.5
—
200-5,250
"
100-51,006
Ranger
(mg/D
600-800
210-325
75-125
10-30
160-250
900-1,700
295-310
450-500
~
0.5
1.6
0.4
400-650
--
6,000-9,000
10,000-14)000
100-700
5.2-6.4
800-4,000
3,500-5.000
7,500-10,000
16,000-22,000
Leachat
Fresh
742
500
*9-
45
277
2,136
--
--
7.35
0.5
—
—
--
989
9.200 1
12,620 1
327
5.2
—
--
14,950
22,650
e5
old
197
1.5
«
0.16
81
254
--
—
4.96
0.1
.-
—
~
7.51
,400
,144
266
7.3
—
—
—
81
*0fffce of Soltd Waste Management Programs, Hazardous Waste Management Division. An environmental
assessment of potential gas and leachate problems at land disposal sites. Environmental
Protection Publication SW-llOof. [Cincinnati], U.S. Environmental Protection Agency, 1973.
33 P. [Open-file report, restricted distribution.]
-t-Stelner, R. C., A. A. Fungaroli, R. J. Schoenberger, and P. W. Purdcm. Criteria for sanitary
landfill development. Public Works. 102(2): 77-79, Mar. 1971
$Gas and leachate from land disposal of municipal solid waste; summary report. Cincinnati, U.S.
Environmental Protection Agency, Municipal Environmental Research Laboratory, 1975.
(In preparation.)
SSrunner, 0. R., and R. A. Carnes. Characteristics of percolate of solid and hazardous waste
deposits. Presented at AWWA American Water Works Association 94th Annual Conference, June
17. 1974. Boston, Mass, 23 p.
Source: EPA (11).
15
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Inorganic constituents (metallic and non-metallic) are present in typical land-
fill leachate. The organic component of landfill leachate is usually char-
acterized indirectly, using general analyses such as biochemical oxygen demand
(BOO), chemical oxygen demand (COD),and, in some instances, total organic car-
bon (TOO. Although the three tests do not differentiate and identify individ-
ual chemical species, they do provide a reasonable indication of the amount of
organic matter present in the leachate solution.
In addition to the chemical constituents present in landfill leachate, the
presence of bacteria and viruses has also been reported. Those organisms iden-
tified include fecal coliform, fecal streptococci, and poliovirus.
Leachate Parameters. The Colorado State Department of Health (CDH) has
assembled a list of parameters which the CDH considers typical of landfill
leachate (9). These are shown in Table 2. The list has been prepared as a
guideline for leachate and ground water monitoring programs, where the
principal effort is directed at identifying the presence of off-site leachate
migration. Since the list has been developed as a guideline, the parameters
should not be viewed as the necessary minimum which must be monitored in a
landfill investigation. Abbreviated parameter lists may also be quite
satisfactory. Selection of appropriate parameters to test will depend on
site-specific requirements.
Leachate Monitoring. A typical leachate monitoring program uses ground
water samples from monitoring wells located at various distances from the land-
fill site. The samples are tested for the levels of representative constitu-
ents of leachate. The constituents included in the program are typically
selected based on consultation with published lists of parameters, such as
those which appear in Tables 1 and 2 of this report. Other considerations in
this selection process include:
o A knowledge of the types of wastes disposed at the site. This informa-
tion is particularly important if a waste is present which would pro-
duce contaminants which are not characteristic of municipal landfill
leachate. This information is usually not available in any detail.
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TABLE 2
CHEMICAL TESTS EMPLOYED BY THE COLORADO DEPARTMENT OF HEALTH ON
LANDFILL LEACHATE.
1. BOD
2. COD
3. pH
4. Ammonia (NH^-N)
5. Nitrate (N03-N)
6. Conductivity
7. Ortho-Phosphate
8. Cadmium
9. Zinc
10. Copper
11. Nickel
12. Total Alkalinity
13. Free C02
14. Potassium
15. Iron
16. Manganese
17. Total Hardness
18. Boron
19. Lead
20. Chromium
21. Chloride
22. Sulfates
23. Sodium
SOURCE: COLORADO DEPARTMENT OF HEALTH (10).
17
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o Budget constraints, which would limit the amount of funds available for
analytical purposes. In this case, the selection process would limit
the number of constituents to those which would be absolutely neces-
sary.
The number of monitoring wells are selected so that at least one well is
located upgradient of the landfill site; one well is located at the downgra-
dient edge of the fill area; and three wells are located downgradient from the
site to detect potential leachate migration off-site (11). The size of the
landfill, the hydrogeologic environment, and budgetary restrictions are the
primary factors which will dictate the actual number of wells used. Every
effort should be made to have a minimum of five wells at each landfill (11).
Locations of the wells, their placement sequence, and the need for additional
wells depend upon the site-specific conditions present at each landfill.
18
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III. STUDY AREA DESCRIPTION
Helena Landfill Site
The City of Helena landfill is situated northwest of the roadway intersec-
tion of Lyndale Avenue and Last Chance Gulch Street in the central part of the
city. The site is bounded on the west by a small ridge upon which Carroll Col-
lege buildings are located and on the north by the Burlington Northern Railroad
tracks. The site is owned by the Burlington Northern Railroad and is leased to
the City. Figure 5 depicts a layout of the site.
The landfill is situated within the alluvial valley of Last Chance Gulch,
an intermittent stream which flows through the center of Helena. Last Chance
Gulch has been diverted through a 60-inch concrete conduit beneath the present
landfill. Water flows both in the conduit and in the bedding material upon
which the conduit rests. The conduit presently discharges at the northwestern
border of the landfill.
The City of Helena has indicated that other utility lines transect the
landfill, including a sanitary sewer which crosses the property from the
southwest to the northeast. It appears that this sewer line is below the
existing landfill and that service lines from this sewer extend to the YMCA and
National Guard Armory buildings on the eastern edge of the landfill.
The Helena landfill site is best described by dividing it into three dis-
tinct areas:
(1) Inactive Fill Area: The 17-acre inactive fill area, which encompasses
the old burning dump, is located north of Lyndale Avenue, west of Last
Chance Gulch Street and east of the north-south railroad spur. When
sanitary landfilling practices were implemented in 1970, twelve acres
of the original 17 acre burning dump were filled with wastes. A
National Guard Armory and a Y.M.C.A. have been built on the remaining
acreage of the old burning dump. The inactive fill area was completed
in June, 1977.
19
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Access to the site 1s limited to six days per week, Monday through
Saturday. The site has a gatehouse with scales and all vehicles are
weighed to determine the quantity of waste received at the site. Ap-
proximately 30,000 tons of waste are received at the site annually and
it is estimated that in January 1982, the expected closing date of this
portion, 159,000 tons of municipal refuse will have been deposited.
The majority of these wastes are generated within the city limits of
Helena. No user fee is assessed to city residents; rather, an annual
collection assessment is charged. Citizens or commercial establish-
ments which are not assessed collection fees must pay a user fee at the
gate.
Four persons are employed at the landfill - a gate keeper, two
equipment operators, and a laborer. The site is maintained primarily
by a bulldozer and a landfill compactor. A scraper is also available
for excavating trenches and stockpiling cover material. The landfill
is in full compliance with all local, State, and Federal standards.
(3) Future Fill Area: The future fill area is located west of Last Chance
Gulch Street and between the two east-west Burlington Northern Railroad
tracks. This area is expected to have an 18-year life beginning in
January, 1982 with an average annual waste load of 35,000 tons per
year. It is approximately 20 to 25 feet lower than the landfill mass
to the south. The ground surface slopes gently down to the north with
a maximum difference in elevation on the order of 5 to 10 feet. In
this area, Last Chance Gulch leaves the 60-concrete conduit beneath the
landfill, and returns to its natural channel. The channel had a moder-
ate amount of flow at the time of the study. Vegetation consists of
grasses, weeds and numerous deciduous trees along the drainage way.
Landfill Site Geology
An independent assessment of the geological and geotechnical data associ-
ated with the Helena landfill site was beyond the scope of this study. Site
geology information, which follows, was obtained from a memo prepared by Mr.
Kenneth L. Waesche, geologist for the State of Colorado Department of Health
22
-------
(10). Mr. Waesche prepared a monitoring plan for the Helena landfill as part
of a peer match visit (an EPA program which seeks to bring problem-solving ex-
pertise to areas which do not have that capability).
The alluvial soils of Last Chance Gulch consist of interbedded silts,
sands, gravels and cobbles which extend to depth of approximately 30 to 35
feet. The alluvium has been thoroughly worked as a placer deposit and con-
sequently is more uniformly graded at those locations where such operations
occurred. Research conducted by the U.S. Geological Survey indicates that
the alluvium directly beneath the landfill has been worked as a placer.
Abandoned dredgings from placer operations are still present north of the
site.
According to available literature, the groundwater flow beneath the site is
confined primarily to the alluvial soils. The groundwater level in the
vicinity of the 12-acre parcel landfilled to date is approximately 30 to 35
feet deep, as indicated from past operations on site. Immediately north of
the Burlington Northern railroad tracks, groundwater is ponded at the sur-
face.
Potential Methane Production from the Helena Landfill
Methane production will be higher in those portions of the Helena landfill
which received household refuse rather than construction debris. The disposal
of liquid paint solvents and snow at the Helena facility will facilitate the
decomposition of the refuse and may enhance methane production because of the
added moisture content of the landfill. It is more likely that methane will be
produced in the sections of the dump which were not burned earlier.
At the Helena landfill, the Y.M.C.A. and the Armory buildings, located on
the inactive fill area, are susceptible to gas migration through both the
natural soils and the sanitary sewer service trenches. Migration of methane to
the south and southeast is restricted by compacted highway fill beneath Lynda!e
Avenue and Last Chance Gulch Street. However, if artifical conduits extend
beneath the highway to the landfill, structures on the other sides of the em-
bankments could also be subject to gas migration. A report by Mr. Kenneth
23
-------
Waesche of the Colorado Department of Health confirms the possibility of
methane migration at the Helena landfill (10). Methane migration to the west
is limited by bedrock outcropping.
Current methane levels are not sufficient to support a methane recovery
system. Older parts of the landfill have been oxidized by previous burning
which has reduced the organic content of the fill and the methane production
potential. Recovery of methane gas from landfills is not considered practical
from landfill sites less than 30 feet deep. The potential for drawing air
through the landfill surface during a methane recovery operation is greater on
sites less than 30 feet deep (5). The depth of fill in the Helena site (12-25
feet) will not adequately support a conventional methane recovery system.
An economic feasibility study and more extensive testing will have to be
completed before a final decision can be made on methane recovery from the
Helena landfill. The methane gas supply does not currently appear to be
dependable enough to support a methane recovery program.
Ground water Contamination from the Helena Landfill
Although landfill personnel indicated that solid waste was not disposed of
directly into the ground water at the Helena site, the ground water level at
the site is approximately five to ten feet below the bottom of the landfill,
with pervious soils in between. Contamination of the ground water by leachate
is therefore possible. Leachate production would be aided by the disposal of
paint solvents and snow from city streets, which occured during the initial
years of operation of this facility.
24
-------
IV. ICTHODS
Field Investigation
The field Investigation for the project was conducted between the 8th and
12th of September, 1980. A barhole punch survey was conducted to delineate
areas of gas concentrations. Seven monitoring wells were drilled and logged to
test for methane and leachate. Gas monitoring equipment was placed in each
well. Methane gas measurements and water samples were collected from each of
the wells.
Fred C. Hart Associates of Denver, Colorado, was the principal contractor
on the project. Chen and Associates assisted in the field investigations and
the assessment of methane gas hazards. Rhinehart Laboratories of Denver,
Colorado, performed the laboratory analyses on the gas and water samples.
State of Montana officials participated in the field investigation.
Barhole Punch Survey. The barhole punch survey technique is a useful pre-
liminary method of delineating areas of gas concentrations in order to position
permanent monitoring wells (1,8). The barhole punch test consists of driving a
small diameter (<1 inch), solid metal rod with a weighted sleeve to a depth of
approximately three feet, removing the rod, and measuring the in-hole gas with
a portable gas meter. The MSA 53 gascope was used to measure the methane. Gas
sampling in each hole was done with a metal probe attached to the gascope. It
is necessary to seal the hole after the metal rod is removed to prevent or
reduce contamination of the gas in the hole by atmospheric gases. Dilution of
the gas samples in this study cannot be ruled out. The barhole punch holes
were larger than the probe and a perfect seal was impossible to maintain.
The barhole punch survey was used to determine the methane gas levels pres-
ent at the landfill surface. The readings obtained during this survey were
used as guidelines rather than accurate determinations of subsurface gas condi-
tions. Several factors may affect the measurements of methane gas levels. For
example, frozen ground, impermeable soils, and barometric conditions can sig-
nificantly influence the subsurface gas levels. Impervious and frozen soils
25
-------
and high barometric pressures tend to restrict the upward migration of landfill
gas. If the barhole punch tests do not fully penetrate the confining barrier,
resulting gas readings may be lower than the actual concentrations of gas with-
in the landfill. For this reason, barhole punch surveys may not be adequate to
accurately monitor landfill methane gas levels. Deep monitoring wells were
drilled to obtain more accurate measurements of methane gas levels in the land-
fill.
Monitoring Hells. Seven monitoring wells were drilled upon completion of
the barhole punch survey. Monitoring wells were located in the general vicini-
ty of sites recommended by the Colorado Department of Health (9). Figure 5
shows monitoring well locations at the Helena site.
Monitoring wells were drilled within the boundaries of the landfill and in
areas adjacent to the landfill. The wells were augered to a sufficient depth
below the ground water level to obtain a representative water sample. The
wells were placed at least ten feet below the groundwater level.
Wells 2, 3, and 5 were drilled slightly outside the limits of the known
sanitary landfill. The primary purpose of these wells was to monitor off-site
methane migration. Well 4 was drilled in the landfill mass to allow measure-
ment of actual landfill gas generation and leachate quality. Wells 1, 6, and 7
were drilled outside the landfill mass to provide ground water level measure-
ments and samples of possible ground water contamination. Well 1 is an up-
stream well and Wells 6 and 7 are downstream wells.
The wells were drilled with a truck-mounted drill rig using a 4-inch con-
tinuous flight power auger. Upon completion of drilling, a 2-inch O.D. (outer
diameter) perforated PVC pipe was inserted into the hole and the annular space
between the pipe and the hole was backfilled with clean sand to five feet from
grade. The sand allows relatively unrestricted gas and water flow into the
perforated casing. The perforated sections of the PVC pipe were prepared by
cutting 1/8" wide slots in the pipe with a hacksaw. All wells used for gas
monitoring purposes were designed so that the perforated sections of the wells
extended above the ground water level, in order to permit gas to enter the well
26
-------
casing. Each well was tightly capped after the PYC pipe was placed in the hole
to exclude atmospheric gases and to allow landfill gas concentrations to col-
lect.
The last five feet of the annular space was backfilled with bentonite clay
to preclude precipitation and surface water from entering the well and prevent
gas transfer into or out of the well. The top and bottom of each monitoring
well were fitted with a PYC cap. A typical monitoring well cross-section is
presented in schematic form as Figure 6.
Subsurface Conditions. The subsurface conditions encountered during in-
stallation of the monitoring wells are shown in Figure 7. The soils encounter-
ed were classisifed in accordance with the Unified Soils Classification System
(12).
The subsurface conditions typically consisted of zero to fourteen feet of
fill overlying either seven to eight feet of stiff, sandy clay or seven to ten
feet of medium dense to dense, clayey sand and gravel. The fill encountered in
Wells 1 and 5 appears to be associated with roadway and railroad embankment
construction. This fill is composed of mixtures of clay, silt, sand and gravel
and cinders. The fill encountered in Wells 2 and 3 appears to be residue of
the old burning dump. This fill is primarly sandy to very sandy clay with
occasional to numerous gravel and cobbles. Varying amounts of glass, brick,
concrete and metal were observed within the fill.
Well 4, drilled in the inactive sanitary landfill area, encountered six
feet of clay, sand, and gravel overlying 20 feet of household refuse. The wood
and paper portions of the refuse appeared to have only decomposed slightly.
Wells 6 and 7, drilled north of the landfill, encountered six inches to two
feet.of sand and gravel fill or silt overlying clayey sand and gravel. Clean
to clay sand was encountered at depths of four to nine feet below the ground
surface.
Bedrock was encountered in Well 3 at a depth 28 feet below the ground sur-
face. The bedrock is hard to very hard limestone.
27
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FIGURE 6. CROSS SECTION OF MONITORING WELL
REMOVABLE PVC CAP
BENTONITE PACK
PVC COUPLING
GRAVEL PACK
GROUND SURFACE
PVC PIPE TWO INCH
SCHEDULE 40
SLOTTED AS NECESSARY*
PVC CAP
FOUR INCH
AUGERED HOLE
NOT TO SCALE
Source: Fred C. Hart Associates, Inc.
* Note: The monitoring well should be slotted so that perforations will be located
above the groundwater level in order to permit gas to enter the well casing.
28
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FIGURE 7. WELL LOGS FROM THE SEVEN MONITORING WELLS PLACED IN THE HELENA LANDFILL
t
^
r
- 0
.
- 5
•
— 10
1
-
0.2.
- 15 •*•
i
1
r>
X
X
X
\
>•
<*
Jj
'*
1
3
1
!
— 20 1
|
~ 25
— )o
X]
5
x
X
)
<
:
-
-
T
I
a
L
•
— 35
X
x
x
x
X
x
x
k
x
k
V
,
J
i
£
i
»
k
t
1
|
1
0.1
LEGENO
- "io
.'
s
/^.
X
g
X
X
\
X
A
r^
I
1
,}
(•1
iS
a
T
p
|
'•V
:>
./.
T>
U
J
?
|
i
t
i
/]
1;
j:
[:]
P*J
J
^
. _
rSj Fill, sand and gravel, clayey sand and a ravel, rock debris, occasional
^^ brick, gfass, ash,1 metal and" concrete, slightly moist to moist
brown to black
~~ l.c ^H
Trash fill, paper products, plastic, metal, wood, cans, concrete, etc.
dark brown to gray,, moist, odiferous.
Clay (CL), sandy, 'scattered gravel, medium stiff to stiff, moist to
very moist brown.
TO Sand (SC), clayey to very clayey, scattered gravel, medium dense,
id moist ccf wet, brown.
Silt (ML), sandy, soft to medium stiff, moist, gray to brown .
f£B Sand £ Gravel (GC-SC), clayey, scattered cobbles, medium dense to dense
ffiS moist to wet, brown
Wj Sand £ Gravel (GM-SM), silty, numerous cobbles loose to medium dense,
Sa moist, brown.
fT3 Sand (SP-GP), gravelly, numerous cobbles, medium dense to dense, moist
uj to wet, brown.
5 —
15 —
Limestone Bedrock, hard to very hard, slightly moist brown to wet, brown
0.2
^. Depth to free water and number of days after drilling measurement was taken.
Indicates depth to which perforar-id PVC pipe was installed in test hole
A Depth at which practical rig refusal was met
Notes
(1) Test holes were drilled September 9, 10, 11, and 12, 1S80, witti a * Inch
diameter contlnous flight power auger or 3 Inch tri-cone rotary methods.
(2) well »5 not completed at time of Initial sampling. Depth to water therefore
not established.
(3) The soil layers shown have been determined based on soil samoles that were
retrieved at the surface from the auger drill. The boundaries that are
shown are approximate.
29
-------
Free water was encountered in Wells 1, 4, 5, 6, and 7 during the study.
The water levels measured ranged from six to 34 feet below the ground surface.
Sampling
Methane Gas SanpHng. The MSA model 53 Gascope was used to measure methane
levels. Two different types of filaments in the gascope measure the percent of
volume of gas in air and the lower explosive limit (LED of the gas. The
gascope was initially calibrated for the LEL of methane. Gas concentrations
below the lower explosive limit are measured by the hot wire, Wheatstone Bridge
method. The combustible gases are burned as they pass across the filament; the
temperature of the filament is raised and the electrical resistance is in-
creased. The increased resistance is proportional to the concentration of com-
bustibles and registers on the meter as percent of the lower explosive limit.
Gas concentrations above the lower explosive limit are measured by a thermal
conductivity filament. The gas sample is passed across the filament which
results in a decrease in the filament's resistance. The decrease is propor-
tional to the gas concentration and is displayed on the meter as the percent of
gas by volume in air. The MSA 53 Gascope measures all combustible gases and
does not differentiate between types of combustible gases (1).
The barhole punch survey at the Helena landfill consisted of 23 tests with-
in and adjacent to the landfill (see Figure 5). Gas readings taken during the
barhole punch survey, inside both the YMCA and the National Guard Armory, and
at the outlet of the Last Chance Gulch conduit are presented in Table 3.
Samples were obtained from the monitoring wells to analyze for subsurface
gases. Gas samples for gas chromotography analyses were collected in evacuated
glass cylinders with stopcocks on each end. Gas samples from each well were
taken by uncapping the well and inserting a long rubber tube attached to the
inlet end of the evacuated cylinder. When the inlet stopcock is opened the
pressure differential between the atmosphere and the cylinder forces a gas sam-
ple into the evacuated cylinders. Several volumes are drawn through the cylin-
der to flush out any atmospheric gas contamination and to get a representative
sample. The outlet side of the cylinder is equipped with a small, hand bellows
which can be used to force air out of the cylinder if it has leaked and lost
30
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TABLE 3. RESULTS OF GAS MEASUREMENTS FROM
BARHOLE PUNCH TESTS AT THE HELENA
LANDFILL
-^\
USA MODEL 51
TEST LOCATION
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* 10
* 11
* 12
* 13
* 14
* 15
* 16
* 17
* 18
* 19
* 20
* 21
* 22
* 23
* 2
-------
its vacuum. After a representative gas sample 1s obtained, both stopcocks are
closed and each cylinder is packed for shipment to the laboratory for analysis.
Mater Quality Sampling. Ground water samples were obtained from each of
the water-bearing monitoring wells installed at the site. A surface water
sample was also obtained from Last Chance Gulch downstream from the site, at
the point where the drainage exits from the 60-inch culvert located beneath the
landfill.Figure 5 shows where each of the wells and the Last Chance Gulch
sampling site are located. At the time of initial sampling, Wells 2, 3, and 7
were dry, and Well 5 had not yet been completed by the driller. Therefore, it
was possible to obtain samples Initially only from Wells 1, 4, and 6, and Last
Chance Gulch.Approximately two days after the initial sampling date,
representatives from the State of Montana Solid Waste Management Bureau (MSWMB)
were able to obtain samples from Well 5 (following completion of drilling) and
Well 7 (which yielded water after the two day recovery period). Since the
budget allowed for the collection of two additional samples, Wells 1 and 6 were
each sampled a second time by the Montana SWMB.
The ground water samples were obtained by using a galvanized steel thief-
bailer well sampler. The wells were bailed to dryness and allowed to recover
prior to collection of the samples. The water samples were placed in the ap-
propriate labeled sample containers provided by the laboratory and preserved
according to EPA procedures (11). Each sample container was rinsed with a por-
tion of the sample prior to containment. The sampling progressed from the up-
gradient and peripheral wells (least contaminated) to the wells in closest
proximity to the site (potentially higher levels of contamination) to avoid the
introduction of artificial interference from contaminated equipment. To fur-
ther preclude this possibility, the sampler and attached cord were rinsed with
distilled water prior to sampling each of the wells.
The pH of the samples was measured in the field using pH-sensitive test
paper, accurate to within a tenth of a pH unit. All other parameters were ana-
lyzed in the laboratory within 48 hours of collection. The samples were stored
in ice from the time of collection until the time of analysis.
32
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Wells 1, 4, and 5 were selected for a scan of trace-level organlcs, utiliz-
ing a gas chromatographic (GC) analysis in order to detect the presence of or-
ganic solvent contamination. The samples obtained from these wells were stored
in glass containers prior to analysis to preclude the leaching of low-level
organic compounds from the sample containers into the samples. As with the
conventional analyses, the GC scan was performed within 48 hours of sample col-
lection.
33
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V. DATA ANALYSIS
Methane Gas Analysis
The MSA model 53 gascope was chosen for the methane gas analysis in the
barhole punch survey. The barhole punch locations can be seen in Figure 5.
Results from the gascope meters for the two variables tested in the survey are
presented in Table 3. The lower explosive limit (LED is defined as the mini-
mum volume of a particular gas necessary to sustain combustion (with a flame
source present) or the lowest point at which gas will explode if concentrated
in a confined area. For this survey, the gascope was specifically calibrated
for measuring methane. Therefore, a gascope reading of 100 percent LEL (e.g.,
test #17 in Table 3) denotes that combustible gases are present at levels
greater than or equal to the five percent (5%) by volume LEL for methane. A
second meter utilizing a different measurement principle is provided on the
gascope as a check on the percent LEL. This meter measures the percent volume
of contaminant gases in the atmosphere based on thermal conductivity instead of
catalytic combustion which is the basis of the percent LEL. The percent gas
meter, like the LEL meter, is calibrated for methane but actually reflects only
the presence of gases other than those normally composing the atmosphere.
The actual severity of the methane problem must be gauged by evaluating and
comparing the readings obtained from both meters to eliminate inherent inaccu-
racies of the measuring instruments. The MSA gascope always shows a slight
fluctuation when the suction bulb is activated. As a result, readings of one
or two percent LEL occurring concurrently with readings of one or two percent
gas should be considered equal to zero. A reading of two percent gas would be
reinforced by a reading of 40% LEL (when instruments are calibrated to methane
where 5 percent gas = 100 percent LEL) but not by a reading of 2 percent LEL.
It must be emphasized that both meters represent indirect measures in that
they are sensitive to characteristics of specific gases rather than the pres-
ence of the particular gases. The identification of the constituent gases and
their relative percentages requires gas chromatography analysis.
34
-------
Since the test holes showing the highest percent LEL and percent gas read-
ing (#13, #17, #20) are located in the active landfill area, it is assumed that
methane gas is present and comprises all or part of the combustible gas volumes
measured.
Results from the barhole punch survey are used only to guide the placement
of monitoring wells. The margin of error in measuring gas levels in a barhole
punch test hole is estimated at 20-30 percent. This large margin of error
makes a definitive analysis of barhole punch test results impossible. The only
conclusions which can be drawn from the Helena Landfill barhole punch data are
that it appears that little methane migration is occurring in the landfill and
that the landfill is producing combustible gases.
The higher percent LEL and percent gas readings in test #13, #17, and #26
along the western perimeter of the active landfill indicate that some concen-
trations of combustible gases are present in that area. A monitoring well was
not placed in the vicinity of the barhole punch test holes on the western peri-
meter of the landfill. Steep slopes and bedrock outcropping adjacent to the
landfill will halt any methane migration on the western perimeter of the land-
fill. Methane produced in the active fill area either exits through the land-
fill cover or moves laterally in other directions.
The absence of methane in the barhole punch test holes may be caused by the
shallowness of the test holes (three feet) or the low production of methane gas
at the Helena landfill due to the limiting factors discussed previously in this
report (temperature, air pressure, moisture, waste content). Methane gas meas-
urements taken near or inside the structures on the inactive landfill sections
do not differ appreciably from the results in the other test holes. This indi-
cates that no methane build up is occuring in the buildings on or near the
Helena landfill at the present time.
Samples were taken from the monitoring wells in order to determine the con-
stituents of the subsurface gases. Table 4 shows the results of the MSA model
53 Gascope measurements and the gas chromatograph analyses. Concentrations of
methane, carbon dioxide, and oxygen from the well samples are listed as percent
of volume of gas. The initial sample showed high percent LEL and percent gas
35
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TABLE 4. RESULTS OF GAS MEASUREMENT FROM
MONITORING WELLS AT THE HELENA LANDFILL l
MSA MODEL 53 GAS SCOPE R AD DIGS
' TEST LOCATION
8smt - YMCA - Service Corridor
Chemical Room - YMCA .
Test Hole 1 JMSWMB)
Test Hole 2
Test Hole 2 (MSWMB)
Test Hole 3
Test Hole 3 (MSWMB)
Test Hole *i
Test Hole 5 (MSWMB)
•
^^•"••^B^E^^V^^^^^^^Bg^^^Hj^^a^^^^^^^Hta^^H^Q^^B^^Bg^^a^^^g^H^^BB^^^Mtp
NOTE: Gas Scope readings taken In
test holes affected by PVC cement
used to glue perforated casing
* LEI
0
0
100
100
100
^•^^•••^•••MMII^^BHMI
VM«IHII^HMV«MMBMH*^MH
% GAS
0
0
10
23
37
' -
^—^•HBKMHMMIH^
BAKUMtlKli.
PRESSURE 3
26.00
26.00
26.00
26.00
•MHMMMOMMBM^HH^Baafl
^bmmifVHa^MafiBfeva
TEMPERATURE
66
66
63
63
l"*V«^M*H^VM^nillHM
*""^Mtf««HB*MMVM^BMHBM
GAS COMPOS)
METHANE
0.0
1.0
8.2
0.05
0.0
1.2
0.0
^••^••••••••••••MM
^^•^•MViVMHV^HV^H^b^
ION - * VOL
CO*
•
0.05
111. 6
18.6
. 4-3
4.3
0.9
0.1
{^•••••^•^•^^•^•^^•^••h
VMH*M*^^inMi^H^BMMVa
HE 2.
02
20.8
5.1
5-9
13- <»
15-6
18.3
20.5
^•MMMMMHMI^HI^HHB^BV
IBMMHVMBIiHII^MHM— •
(MSWMB) Samples obtained for testing by Montana Solid Waste Management Bureau.
1. All samples were taken on September 12, 1980 except samples designated MSWMB
which were taken during the week of September 22.
2. N2 component was not analyzed. Gas analyses can include measurement of N2 content,
ij^ check to ensure the gas components add to almost 100% is needed. N2 is about
T^Jof atmosphere by volume and can generally be assumed to be the remainder of the gas
composistion after 02,
C02, and CH^ are analyzed.
3, Between the time the barometric readings in Table 3 and 4 were taken, a definitive
low pressure system moved into the Helena area.
-------
readings in Wells 2, 3, and 4. These high readings are attributed to the
cement used in bonding the PVC pipe joints for the well casing. The cement
gives off volatile gases as it dries. Subsequent samples taken by the Montana
Solid Waste Management Bureau (Table 4 lists these samples as MSWMB) indicate
that the wells have vented sufficiently to allow more accurate measurement of
the gas conditions in the landfill. A comparison of the results of the gas
chromatography analysis shows the discrepancy between the sample data. The
second sample set indicates combustible gases in Wells 2 and 3. Well 4 was not
tested a second time. Gascope readings were not taken for the second sample
set.
Test results from the seven monitoring wells show that methane gas genera-
tion at the site does not appear to be in an unusually active state (see Table
4). Well holes 2 and 4 show methane gas concentrations of 1.2 percent and 8.0
percent, respectively. Measurable amounts of methane were not found in the re-
maining well holes. Although recent measurements by the Montana State Health
Department show higher LEL values than measured during this study, methane gas
generation remains minimal at the present time. A monthly monitoring program
would reveal data variations caused by seasonal fluctuations, sampling proce-
dure, or analysis methods and would yield baseline data which could be used to
predict methane production trends and the potential magnitude of the methane
hazards.
Varying barometric pressures will influence the gas readings in gas
sampling wells. Studies have shown that the specific barometric pressure has
little affect on the gas volumes in the wells. However, rising or falling
barometric pressures can affect the accuracy of the gas samples' reflecting
existing conditions. Decreasing barometric pressures enables the gas to move
upward through the well; the gas can be measured near the ground surface.
Stable or increasing barometric pressures may force gases in the monitoring
wells to the bottom of the wells. Surface or near-surface gas sampling in such
instances will misrepresent existing conditions. The sampling method for this
report used specific barometric readings. Barometric pressures are not
expected to affect the gas samples obtained in this study due to the deep
sampling technique used to obtain samples from the monitoring wells.
37
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An additional sample set from the seven monitoring wells was taken in the
first week of May, 1981, by personnel of the Montana SWMB. Wells 1, 3, 6 and 7
have no gas concentrations measured. Wells 2 and 4 continue to show possibly
high methane gas readings with a 6 percent (14% in a later test) combustible
gas composition yielding 100 percent of the LEL in Well 2. Well 4 showed a 40
percent LEL reading (30% and 35% combustible gas composition readings). Well 5
yielded a 30 percent LEL reading. Although no conclusive results can be drawn
from this single measuring effort, it is useful to note the possible
confirmation of methane (or other combustible gas) in Wells 2 and 4.
Additional testing and analysis are needed to corroborate these measurements;
they lend added emphasis for establishing a methane gas monitoring system for
the landfill site.
The organic element of the older sections of the landfill underlying the
YMCA and the National Guard Armory have been oxidized by previous burning on
the site. Methane generation in this section is expected to be low. The
remaining portion of the inactive fill area appear to contain moderate concen-
trations of organic material. These materials lack the relatively high
moisture contents associated with large methane production.
The unburned refuse placed in the inactive fill section between 1970 and
completion of filling in 1977 has undergone a moderate amount of deterioration.
The percentage of oxygen, carbon dioxide, and methane measured in the wells and
the undecomposed nature of the materials in the wells supports the observation
that only a moderate amount of waste decomposition has occured. The potential
exists in the inactive fill area for a significant amount of future anaerobic
decomposition and methane production.
Migration. Lateral methane gas migration at the Helena landfill site
appears minimal, although Well 2 indicates that some methane migration is
occurring. Well, 2 was drilled within ten to fifteen feet of the landfill
mass. Well 3 was drilled near the YMCA building, about 50 to 100 feet outside
the landfill, and had insignificant methane gas levels. No significant gas
levels were measured in Wells 1, 5, 6, and 7. Well 4, drilled in the northern
part of inactive fill area (near the baseball fields), shows a small amount of
methane.
38
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The granular composition of the landfill cover material may account for the
absence of gas migration at the landfill. The on-site alluvial materials are
probably allowing the methane to escape vertically before it is forced to
migrate horizontally. Because some migration appears to be occuring in the
vicinity of Well 2 and the landfill mass has continuing potential for methane
gas production, an additional methane gas monitoring well should be placed
between the YMCA and the Armory buildings and several barhole punch tests
should be placed around the foundations of the buildings. An additional well
between the two buildings would provide more conclusive information on the
extent of gas migration to an area where methane might collect and explode.
Leachate Analysis
All samples were delivered to Rinehart Laboratories of Denver, Colorado for
analysis. Table 5 lists the parameters which were selected for analysis in
this study. The selection was made based on a review of published municipal
landfill leachate characteristics (11) , the recommendations of the Colorado
Department of Health (10), and a budgetary review by EPA Region YIII person-
nel. A gas chromatograph (GO analysis for trace-level organic compounds was
also included in the study for three of the wells, based on information pro-
vided by the Montana SWMB which indicated that organic solvents had at one time
been disposed of at the site.
All analyses were performed using analytical methodology specified by EPA
(9), supplemented by procedures published in Standard Methods (14). The GC
analysis was performed using a pentane extraction procedure recommended by Dr.
Robert Rinehart (15).
Table 6 presents the results of the water quality analysis program. As can
be seen from this table, two of the wells, #2 and #3, were dry at the time of
collection and samples could therefore not be obtained. Wells 1 and 6 were
each sampled twice (within a three day period), since budget constraints
allowed the collection of two additional samples.
The results of the analyses indicate that the Helena landfill is not posing
any major hazard as a result of leachate migration. In Table 6, the water
quality results are compared against three sets of published values for inter-
39
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TABLE 5
PARAMETERS USED IN THE HELENA LANDFILL STUDY
Paramters used in the Helena Landfill study.
1. pH
2, Specific Conductivity
3. Total Dissolved Solids
4. Total Alkalinity
5. Chemical Oxygen Demand
6. Nitrate-Nitrogen
7. Sulfate
8. Sodium
9. Potassium
10. Cadmium
11. Zinc
12. Copper
13. Nickel
14. Chromium
15. Lead
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TABLE 6. RESULTS OF THE CHEMICAL ANALYSES
PARAMETER
PH
SP. coroucnmr
(umos/cn)
TOTAL DISSOLVED
SKIDS (Mg/L)
TOTAL AUAUKin
("9/1 )
COO (Hj/l)
11 1 IRA IE-" (Mg/l)
Kill
Sample 11 .
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pretative purposes. These comparative values include the EPA Primary and
Secondary Drinking Water Standards (16), the EPA Water Quality Criteria (17),
and published values for those constituents which occur in natural ground water
(18). This comparison indicates that the ground water in the vicinity of the
site has not been altered significantly by the existence of the landfill. None
of the values greatly exceed any of the published values, although the dissolv-
ed solids content of the samples generally are higher than the EPA drinking
water standard of 500 mg/1. Samples from two of the wells, numbers 4 and 6,
showed elevated levels of nitrate. Both samples showed nitrate-N concentra-
tions of 12 mg/1., which is slightly above drinking water standard of 10 mg/1.
Wells 1 and 7, and Last Chance Gulch, also showed elevated levels of lead,
above the EPA drinking water standard of 0.05 mg/1. The high lead value from
well number 1 located upgradient from the site, may be attributable to
analytical error, since the anomalously high value of 0.14 mg/1. was observed
for only one of the two samples obtained from that well. The other sample
showed a lead value of 0.011 mg/1., an order of mangitude below the former
samples. Further sampling and analysis will be needed to clarify this discrep-
ancy. The lead values obtained from the wells sited within the landfill were
below the EPA drinking water standard.
Although the dissolved solids content of the samples indicates that the
ground water in the vicinity of the landfill (both upgradient and downgradient)
is generally not potable, the range of values observed for the monitoring wells
still fall within those expected for natural ground water. In summary, the
comparison of the sample values with published water quality information
indicates that the ground water has generally not received any of the measured
constituents from the landfill at levels which would provide cause for alarm.
However, the ground water is not considered potable due to elevated levels of
dissolved solids, and possibly nitrates and lead.
In addition to comparing the results of the water analyses to published
water quality information, the significance of leachate contributions to the
ground water of the area can also be assessed by comparing the water quality
characteristics of the background (upgradient) well with the characteristics of
the downgradient wells. In this case, the water quality observed for Wells 6
and 7, downgradient from the landfill, was generally as good as that observed
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for Well 1. Wells 4 and 5 are sited within the landfill boundaries; typically,
they should have poorer water quality characteristics than the downgradient
(off-site) wells. This trend was not observed to a significant degree at the
Helena landfill. The fact that ground water beneath the landfill site (as
indicated by wells 4 and 5) does not contain significantly elevated levels of
constituents (relative to either the upgradient or downgradient wells)
indicates that large volumes of leachate are probably not being generated in
the landfill.
Trace-Level Organic Compounds. The gas chromatograph analysis of the water
samples obtained from Wells 1, 4, and 5 showed no detectable organic constitu-
ents. Dr. Robert Rinehart confirmed that the GC scan employed was of suffi-
cient scope to detect any organic solvents in the samples which may be present
as a result of the disposal of paint solvents in the landfill (15). The scan
would be able to detect compounds present in the sample in the microgram/liter
(parts per billion) range if indeed they were present. As a result, the sol-
vents which were reportedly disposed of in the Helena landfill pose little dan-
ger to the environment at this time. Further analyses may be required in the
future, however, to verify that the conditions have not changed and to confirm
that a leachate plume containing organic solvents has not been generated.
Direction of Ground water Flow. The direction of ground water flow in the
vicinity of the Helena landfill site can be established by plotting the water
table elevations (relative to an arbitrary datum) observed in each of the
monitoring wells. Table 7 shows the elevation of the water table in each well,
relative to the ground surface at the top of Well 1 (the assumed arbritary
datum in this study). The ground surface at Well 1 is arbitrarily assigned an
elevation equal to zero.
Based on this information, the direction of ground water flow in the
vicinity of the Helena landfill is from south to north, following the general
slope of the land surface. In this area, the ground water should also be in
hydraulic connection with Last Chance Gulch, which also flows to the north.
The reason for the temporal variation in ground water levels near the land-
fill is unknown at this time; further long term monitoring of water levels
would be required to establish this variation. It is possible that the ground
43
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TABLE 7
WATER TABLE ELEVATIONS
WELL NUMBER
ELEVATION*
DEPTH TO WATER
WATER SURFACE
ELEVATION*
1
2
3
4
5
6
7
O.O1
-10.O1
-13.51
-16.O1
-24.51
-43.O1
-50.51
15' -15'
Dry N/A
Dry N/A
34' -50'
Not Established** N/A
6' -49'
10' -60.5'
* All elevations are in reference to well number 1, which is arbitrarily
assigned an .elevation equal to zero.
**Well not completed at the time initial measurements were made.
44
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water levels 1n the vicinity of the landfill could vary in direct response to
individual precipitation events. The direction of flow is topographically con-
trolled and will not change.
It is also important to realize that the water levels recorded in this
study were those present shortly after drilling; the ultimate levels could
deviate from these values following further recovery of the wells.
During certain times of the year, it is possible that Last Chance Gulch may
serve as a source of recharge to the ground water system in the vicinity of the
landfill. This would occur under those circumstances where the water levels in
the wells were below the stage elevation of Last Chance Gulch. During the re-
mainder of the year, the ground water would ultimately discharge to the Gulch,
serving to maintain base flow in the channel. In order to precisely define
these relationships long-term monitoring of water levels in the wells would be
necessary.
Statistical Significance of the Data
It is important to realize that the above discussion is based on the re-
sults of a single sampling effort which has little statistical significance.
These conclusions must be viewed with caution, since the variability in the
data, for the most part, has not been established. For example, Wells 1 and 6
were each sampled twice during the three day field investigation, and the
results for these wells indicate that the ground water quality can vary. These
variations can result from natural fluctuations in the ground water quality,
from the introduction of artifical interferences such as sampling error, and in
the range of accuracy expected for the analytical procedures.
In order to fully determine trends, long term averages, seasonal
fluctuations, and ranges in concentration of ground water and methane for each
of the wells, monitoring must be continued over a longer period of time. A
number of data points for each well would allow a statistical comparison of the
water quality and methane levels which exist at each monitoring location. The
statistical significance of the data cannot be determined from a single set of
samples.
45
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We can conclude based on the single set of data points, that the Helena
landfill does not pose an Immediate risk to the environment or general public.
No ground water contaminants were observed at any levels which would classify
the landfill as an "imminent hazard," as defined by Section 7003 of the
Resource Conservation and Recovery Act. Methane levels were also not
considered hazardous. This is the most important conclusion which can be drawn
from the initial sampling and analysis program.
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VI. CONCLUSIONS AND RECOMMENDATIONS
Methane Gas Generation
Conclusions. Preliminary findings indicate that:
o A minimal amount of methane is currently being generated within the in-
active landfill area.
o The migration of methane appears minimal.
o Current methane production is not sufficient to support a dependable,
long-term methane recovery system.
o An automated methane monitoring alarm system should be installed in the
Helena YMCA and the National Guard Armory.
Some methane gas concentration occurs along the eastern edge of the inac-
tive fill area. As a precautionary measure, it is recommended that additional
methane monitoring wells should be drilled between the YMCA and the Armory
buildings to assess the potential methane concentrations in this area.
Although methane migration at the Helena landfill does not appear exten-
sive, it is possible that concentrated pockets of methane may exist in the
landfill. Current data does not support this conjecture, however. A more
thorough well drilling and monitoring program would be necessary to establish
the likelihood, if any, of this potential.
Methane concentrations are not dangerous (and barely detectable) within and
adjacent to the landfill site. Methane levels are not expected to increase
appreciably in the near future.
It may be prudent, however, to construct impermeable barriers to control
methane migration where possible in the active fill area. While the data do
not indicate alarming levels of methane in or adjacent to the landfill, the
proximity to residential or recreation areas would dictate taking precautionary
measures where possible to control potential methane migration. Additionally,
the future fill site design might include impermeable barriers or an effective
ventilation system around the site perimeter.
47
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The absence of substantial methane migration at the Helena landfill is
probably due to the granular nature of the landfill cover. The alluvial
materials on the site appear to allow any methane gase produced in the landfill
to exit vertically without forcing the methane to migrate laterally. Although
no methane control measures are currently in place at the landfill, the
continued placement of organic refuse in this area will result in future
methane gas generation in the landfill and a potential off-site methane migra-
tion problem east of the landfill.
Reconraendations. Gas readings with a MSA Gascope should be taken on a
monthly basis in Wells 2, 3, 4. Additional monitoring wells should be drilled
around each building and further barhole punch testing done near the founda-
tions of the YMCA and the Armory (See Figure 5 for recommended locations).
Seasonal gas readings should also be taken in the service corridor of the YMCA
building and in the basement of the National Guard Armory building by the local
gas company with a flame pack or more sensitive device. These readings should
be taken during exteme seasonal conditions such as during hot summer period
shortly after a heavy rain, when the ground is frozen in the winter, and during
the spring runoff period. Additionally, readings in the buildings should be
taken at times when the surrounding monitoring wells indicate high levels of
methane. Sufficient baseline data could be established by seasonal flame pack
and monthly readings over a two year period. Methane gas migration control
systems could be installed in the landfill based on the analysis of this data.
Installation of an automated monitoring and alarm system in the YMCA and
the Armory is also recommended. The YMCA and Armory buildings should be moni-
tored closely during the winter months since building doors and windows are
closed during the winter months. Frost reduces the vertical ventilation of gas
in the landfill and greater horizontal methane migration is possible.
The costs for additional drilling of monitoring wells and installations of
a methane alarm system for the YMCA and Armory buildings are estimated below.
Well development costs are estimated to be about $500 per well which includes
drilling, logging, and installation. The seven wells used for this study aver-
aged about $570/well. The probable cost range for developing each well is
between $400 and $650. These estimates include the use of a well-drilling rig
./IP
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for four hours at $60/hour, an engineer/logger for 4 hours at $25/hour, and
mountings for about $100 (for a 30 foot well). The severity of the drilling
conditions at the Helena site limits the use of an auger because of the rock
and gravel deposits and Increases the expense of the drilling operation.
The cost to Install a methane alarm system in the YMCA and Armory buildings
is estimated to range between $2,000 and $4,500, depending upon whether a com-
bined or separate alarm system is used. The central panel and four monitors of
a combined alarm system cost about $2,000. Additional monitors each cost
between $400 and $500. Six to eight monitors are expected to be needed for the
YMCA and the Armory. These monitors should be located based on the results of
the flame pack analysis. The central panel could be located in either
building, although an Armory location may be easier to monitor. Placement of
remote monitors should not exceed 1,000 feet from the central panel due to the
resistance to the signal impulses over long distances. The local fire
department should be informed regarding the operation of the methane alarm
system.
Leachate Contamination
Conclusions. The primary conclusion which can be reached concerning the
leachate contamination potential of the Helena landfill is that the landfill
poses no immediate hazard to the environment or the general public. The water
quality analyses performed on the water samples obtained from the site indicate
that there is little difference in the constituent levels present in the down-
gradient wells, relative to the upgradient (background) well. Furthermore, the
wells sited within the landfill body showed comparatively little significant
increase in constituent levels, although dissolved solids and specific conduc-
tivity were slightly above those observed for the background well. Generally,
the constituent levels for all the wells were within the ranges expected for
natural ground water. Although the constituent levels were low in comparison
to published values, the ground water quality is probably not potable, due to
elevated levels of total dissolved solids and to the absence of long range
water quality testing.
49
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The gas chromatographic scan of three water samples from the site also in-
dicated that low-levels of organic solvents are not present. The scan was com-
prehensive in scope, and would have detected the presence of industrial paint
solvents, reportedly disposed of at the site, if they had entered the ground
water in significant quantities near the wells.
The overall conclusion that the landfill poses no immediate health or en-
vironmental hazard must be viewed with caution, since the conclusion is based
on a result of a single set of sampling points only. Statistically, it is not
possible to determine the variability which may exist in the data for each
well, since additional data points, obtained through additional monitoring ef-
forts, would be necessary. This information would also be required before sub-
tle, yet discernible, trends could be distinguished. The initial set of samp-
ling points indicates that the landfill does not consitute an immediate health
or environmental hazard, since extensive, off-site leachate migration was not
observed.
Recoamendations. It is recommended that the State of Montana Solid Waste
Management Bureau institute a long term water quality monitoring program at the
Helena landfill site. The program should involve the collection of water
samples from each of the water-bearing wells installed at the site, as well as
from Last Chance Gulch, both upstream from the site and at the point of exit
from beneath the landfill. Water-level measurements should also be made at
each of the wells. It is anticipated that a quarterly sampling program will be
adequate; however, the sampling schedule should be flexible, allowing for modi-
fication should the results of the program dictate the need for either an
increase or a decrease in sampling frequency. If the results of the quarterly
program substantiate that leachate contamination is not significant, the
program could be reduced further to sampling on either a semi-annual or annual
basis. However, it is important that the program be instituted soon so that
additional data can be obtained to validate the conclusions drawn in this
report. The observed elevated levels of nitrate and lead further substantiate
the necessity of a monitoring program.
50
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It 1s recommended that the ground water monitoring program initially in-
clude all the test parameters contained 1n Table 5 of this report. This would
verify the statistical significance of the conclusions presented. However, de-
pending on budget considerations, a reduced set of parameters may be consider-
ed. A reduced set could consist of the following key parameters suggested by
EPA (10):
o Specific Conductance
o pH
o Temperature
o Chloride
o Iron
o Color
o Turbi di ty
o COD
plus the addition of:
o Nitrate - N
o Lead
Nitrate - N and lead were observed in some of the wells at values above drink-
ing water standards.
By utilizing a reduced set of parameters, a substantial cost savings in
analytical work can be achieved. The above analyses would typically cost about
fifty dollars ($50) or less per sample. However, if a sudden change in an in-
dicator parameter is observed, it will require extended analytical work. Ex-
tended analyses are necessary to pinpoint the limits of the possible contamina-
tion.
In addition to the limited list of conventional parameters considered
above, it may also be beneficial to include a GC scan on an annual, or semi-an-
nual, basis to ensure that a solvent-laden leachate plume from the disposed
solvent drums has not entered any of the wells. The initial data indicates
that trace organic compounds do not pose a major problem at this time.
51
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If the results of the long term program at any time indicate that extensive
off-site migration of leachate is occurring, additional test parameters should
be added to fully define the magnitude of the problem. Tables 1 and 2 will be
useful for determining the other constituents which may have to be tested.
If a problem is identified through long-term monitoring, the program should be
amended to include as many as possible of the pertinent leachate constituents.
Although the initial program did not reveal any significant health or en-
vironmental problems resulting from leachate generation at the Helena landfill,
the institution of the long-term monitoring program is recommended for the fol-
lowing reasons:
o to generate enough data so that stastically valid conclusions can be
made.
o to observe subtle trends in ground water quality, observable over long
periods of time, which would indicate that discernible leachate migra-
tion is occurring.
o to identify seasonal trends in ground water levels and direction of
flow.
o to verify that a leachate plume does or does not exist within the
Helena landfill.
We recommend that the City of Helena and the State of Montana implement a
long-term methane and leachate monitoring program at the Helena landfill site
in order to assemble the necessary baseline data.
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REFERENCES
1. Intergovernmental Methane Task Force (1979). Methane from Landfills:
Hazardous and Opportunities, EPA Region VIII Symposium Proceedings.
2. Stone, Ralph (1978). Reclamation of Landfill Methane and Control of Off-
Site Migration Hazards, in Solid Waste Management.
3. Farquhar, G. J. and F. A. Rovers (1973). Gas Production During Refuse
Decomposition, in Water, Air, and Soil Pollution.
4. Dix, Stephen (n.d.) Report on Methane Evaluation at Landfills in Larimer
County, Larimer County Health Department, unpublished report.
5. Fred C. Hart Associates (1979). The Examination of the Problems and Po-
tential for Methane Gas Recovery. Draft report prepared for Colorado
Energy Research Institute.
6. SCS Engineers (1980). Feasibility of Landfill Gas Utilizations - Larimer
County, Colorado; unpublished report.
7. U.S. EPA (1977). Recovery of Landfill Gas at Mountain View. EPA/530/SW-
587 d.
8. Environmental Impact Control Directorate (1977). Procedures for Landfill
Gas. Environmental Protection Service, unpublished report.
9. U.S. EPA (1975). Use of the Water Balance Method for Predicting Leachate
Generation from Solid Waste Disposal Sites. EPA/530/SW-168.
10. Colorado Department of Health (1980). Preliminary Assessment of the Po-
tential Methane Gas and Leachate Problems at the Helena, Montana, Land-
fill, prepared by Kenneth L. Waesche (unpublished).
11. U.S. EPA (1977). Procedures Manual for Groundwater Monitoring at Solid
Waste Disposal Sites. EPA/530/SW-611.
12. ASTM D-2487-69 (75). Standard Method for Classification of Soils for
Engineering Purposes. Annual Book of Standards, ASTM, Philadelphia, PA.
13. U.S. EPA (1979). Methods for Chemical Analysis for Water and Wastes.
EPA-600/4-79-020.
14. American Public Health Association (1976). Standard Methods for the Exam-
ination of Water and Waste Water, 14th ed.
15. Dr. Robert Rinehart, Rinehart Laboratories, Inc., Denver, Colorado
(1980). Personal communications.
16. U.S. EPA (1979). National Interim Primary Drinking Water Regulations,
EPA-570/9-76-003, U.S. GPO, Washington D.C., July 1976. National Second-
ary Drinking Water Regulations. Federal Register, 44FR42195.
53
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17. U.S. EPA (1970) Quality Criteria for Water. U.S. Government Printing
Office, Washington DC.
18. Davis, F.N., and J.M. Dewiest (1966). Hydrogeology. John Wiley & Sons,
NY, as cited in : U.S. EPA (1977), Procedures Manual for Groundwater
Monitoring at Solid Waste Disposal Facilities, EPA/536/SW-611.
54
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
908/6-81-002
4. TITLE AND SUBTITLE
Landfill Gas and Leachate Monitoring.
Helena, Montana-A Technical Assistance Program Report
7. AUTHOH(S)
Roger Baker, Marc Jewett, David Jubenville, David Kuntz,
Burke Lokey, Stephen Orzynski
9. PERFORMING ORGANIZATION NAME AND ADDRESS
FRED C. HART ASSOCIATES, INC.
1320 17th Street
Denver, Colorado 802S2
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Region VIII
1860 Lincoln Street
Denver, Colorado
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
.lulv 1981
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-6008
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Leachate contamination of ground water and methane gas production are potential
problems associated with solid wastes deposited in landfills. Expanding urban areas
may utilize former sites for residential building sites, schools, and parks. This
report presents an example of a method which can be used to design a permanent methane
gas and leachate monitoring program from a relatively inexpensive preliminary investi-
gation.
The monitoring program was conducted on a landfill located within the city limits
of Helena, Montana in 1980. A barhole punch survey was conducted to delineate areas
of methane gas concentrations and to guide placement of wells. Seven monitoring wells
were drilled, logged, and samples were collected. An MSA Model 53 Gascope was used to
measure the percent of volume of gas in air and the lower explosive limit of the gas.
Water samples were analyzed in a laboratory under selected parameters.
Preliminary findings indicated that only a moderate amount of methane gas is
being generated and migration of the gas appeared to be minimal. Leachate from the
landfill did not appear to have contaminated the ground water.
The report recommends that a long term water quality and methane gas monitoring
program be instituted and estimates costs of such a program.
17. KEY WORDS AND DOCUMENT ANALYSIS ~~"
a. DESCRIPTORS
Methane, Sanitary Landfills, Solid Waste
Disposal, Ground Water, Monitoring.
18. DISTRIBUTION STATEMENT
Released to public
b.lDENTIFIERS/OPEN ENDED TERMS
Helena, Montana
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
c. COSATI Field/Croup
21. NO. OF PAGES
61
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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