Use of Indicator Parameters to
Diagnose Potential Source(s) of
Groundwater Contamination
Shawn Carroll
Lead Environmental Protection Manager
Waste Management – South Atlantic Area
SC Palmetto SWANA May 19, 2016
Acknowledgement:
Seth Ramaley
Groundwater Director
Waste Management – Southern Tier
Discussion Topics
•
•
•
•
•
Sources
Geochemical Toolbox
Advanced Analyses
Field Tools
Case Studies
Sources
• Lab or Sampling Artifact
– Data Validation, Verification Sampling
• Non-landfill
– Alternate Source?
– Naturally Occurring, Neighboring Site, etc.
• Leachate
• Landfill Gas
Typical MSW Leachate Composition
• Dissolved organic matter (COD or TOC) including
methane and volatile fatty acids.
• Organic compounds including aromatic hydrocarbons
and chlorinated aliphatics (i.e., VOCs).
• Inorganic macrocomponents: Ca, Mg, Na, K, NH4,
Fe, Mn, Cl, SO4, and HCO3.
• Heavy metals Cr, Cu, Pb, Ni, and Zn.
• (SCR000000 Sector L – BOD, TSS, NH3, aTerpineol, Benzoic Acid, p-Cresol, Phenol, Zinc)
[Christensen et al, 1994]
Landfill Gas Composition
Generally…
• Methane:
40 to 70 %
• Carbon Dioxide:
30 to 50 %
• Trace Gases (VOCs):
< 5%
(Source: Brosseau and Heitz, 1993/Kerfoot 1994)
Common Trace Gas VOCs Found
in MSW Landfill Gas
Benzene
1,1-Dichloroethane
Dichlorodifluoromethane 1,2-Dichloroethane
Acetone*
Chlorobenzene
Methyl ethyl ketone (MEK)*Tetrachloroethylene
Toluene
Trichloroethylene
Trichloromethane
Ethylbenzene
Vinyl chloride*
Xylenes
Others: Methylene Chloride, Freons
*Lab artifact potential and/or false positive.
(Source: Brosseau and Heitz, 1993/ Vogt, 1995)
Typical Site Monitoring Network
GP-1
MW-D
MW-A
GP-4
Landfill
MW-E
MW-B
GP-2
(1%)
MW-C
GP-3
Legend:
MW-A
N
GP-1
Groundwater Flow
Direction
Detection Monitoring
Well
Gas Probe
Property
Boundary
Geochemical Toolbox
• Leachate Indicators
• Primary (Chloride, Sodium, Ammonia)
• Secondary (TOC, TDS, SpC)
• LFG Indicators
• Primary (Alkalinity, Calcium, Magnesium)
• Secondary (Methane)
• Data Review
• Piper Stiff Diagrams
• Statistics
Landfill Gas Impact Inorganic
GW Geochemistry
1)
Dissolution of inorganics through the formation of
carbonic acid:
CO2 (g) + H2O (aq) = H2CO3 (aq)
H2CO3 (aq) + CaCO3 (s) = Ca2+ (aq) + 2HCO3- (aq)
2)
3)
Reduction of Fe (III) and Mn (IV) from methane
Dissolution of metals complexed with Fe and Mn
(i.e. Arsenic)
Landfill A
Geochemical Data
80
Sul
fat
e(S
O4
)+C
hlo
40
rid
e(C
l)
60
1995
1996
1997
1998
1999
1999
Lcht 95
20
20
Tri-Linear
Diagrams
CL-Na Shift
With Leachate
Impacts 1994
g)
m(M
siu
gne 0
4
Ma
a)+
m(C
ciu 60
Cal
Alkalinity Shift
Common with
LFG-impacts
80
Lcht 97
Lcht 98
Lcht 99
Mg
20
80
0
Ma
gne
siu
m(M
g)
6
40
20
CATI ONS
20
Na+K
20
40
60
80
60
Calcium(Ca)
)
O4
e(S 40
fat
Sul
80
80
80
(K)
60
um
ssi 60
ota
)+P
40
(Na
ium 40
Sod
20
Car
bon 80
ate
(CO
3) 60
60 +Bic
arb
ona 40
te(
40
HC
O3)
20
20
Ca
SO 4
80
Inorganic
Geochemistry
HCO +CO
3
3 20
%meq/l
40
60
Chloride (Cl)
ANI ONS
80
Cl
Inorganic
Geochemistry
Landfill
Geochemical Data
Cations
meq/l
Anions
25
25
Cl
Na+K
1994
Ca
Stiff Plots
Mg SO4
Na+K
HCO3+CO3
Cl
1995
Ca
Mg
Na+K
SO4
1996
Ca
Mg
Na+K
SO4
1997
Ca
Na+K
Mg
SO4
1998
Ca
Na+K
Mg
Na+K
Mg
Mg
HCO3+CO3
Cl
HCO3+CO3
Cl
HCO3+CO3
Cl
HCO3+CO3
SO4
1999
Ca
Cl
SO4
1999
Ca
HCO3+CO3
SO4
Cl
HCO3+CO3
Forensics - Fingerprinting
Isotopic Source Identification
IDENTIFICATION OF BACTERIAL GASES
15
Natural Gas &
Petroleum-based Chemicals
Number of Samples
(no detectable
14
C)
Pre-1950’s Source
10
Glacial
Drift
Gas
5
Landfill
Gas
Swamp & Marsh Gas
(potential range)
0
0
10 20 30 40 50 60 70
14
[Coleman et al, 1995]
80 90 100 110 120 130 140 150
C Activity of Methane (pMC)
Delta O-18 vs. delta D
10
0
delta D of Water (o/oo)
Leachate
-10
Dueterium Shift due to
methanogenisis
-20
MH-02
MW-01
MW-03
MW-06
MW-09
MW-3
-30
Global meteoric water line
MW-1
MW-6
MW-09
-40
O18 Shift due to
Water/Rock Interactions
-50
-60
-70
-8
-7
-6
-5
-4
delta O-18 of Water (0/00)
-3
-2
Field Tools
• Site Investigation
• Site Operations
• Site Construction History
• LFG and Leachate Piping Network
• Well Headspace Analysis
• Direct Push or Bar-Hole Probes For LFG Migration
• Thermocouples
• Depth of gas migration
CASE STUDIES:
Sudden spike in liquid
indicators
This image cannot currently be displayed.
MW-26
•Old rainfall toe drain perforated pipe
that comes from under the rain flap to
outside the rain flap...right by the
well.
•Direct conduit for leachate.
•It should have been cut off when rain
flap was installed or fully contained
inside the rainflap/liner, which were
and are welded together.
•Instead, it was booted it right
through.
TOE
DRAIN
•Site uses crushed shale as
cover with very little runoff
•Constantly battles seeps
because hill is over
saturated
•Gas system is watered in
STORMWATER
DITCH
RAINFA
LL
Picked up liquid indicators, MEK, and Acetone
in MW
SEEP – Hits
Low
Permeability
Layer
•Installed Rain Cover to Prevent
Seeps on outside slope of
active area
•Eliminated seeps
•Mitigate GW impacts
•Reduced leachate volumes by
increasing run-off
Installation
of Rain
Cover
Edge of
Liner
No Tie-in
STORMWATER
DITCH
(LFG bubbling in Ditch)
LEACHATE
AND GAS
Problem Area
LINER
IMPACTED
MW
GW
IMPACTS
•VOCs in Groundwater wells attributed to
gas migration
•No indicator signature – sampled for
methane
•Initiated installation of toe drain to prevent
gas migration over anchor trench
•Found liner Issue with a retrofitted cell built
to capture air space during construction of
toe drain that was allowing gas and leachate
to discharge directly to unsaturaed zone and
GW
CGI Landfill
Richland County, SC
•Unlined Class II landfill in SC, older facility that
WM acquired and has essentially been
mothballed since.
•Tested dissolved methane and alkalinity,
determined gas (H2S and methane) impacts,
resulting in mobilization of metals (arsenic).
• Installed probes, submitted Gas Monitoring
Plan, offsite impacts (no sensitive receptors)
•Installed passive vents, partial but not sufficient
relief
•Converted passive wells to active, will be
installing blower skid this month to extract gas.
Site ideal for this option due to remote location,
size of property, and no impacted receptors.
Questions?
Thanks!