Numerical Investigations of Flow through Fractured Porous Media
Field Approach for Investigating Contaminated Sites in ...€¦ · modeling of groundwater flow and...
Transcript of Field Approach for Investigating Contaminated Sites in ...€¦ · modeling of groundwater flow and...
The Discrete Fracture Network (DFN) Field Approach for Investigating
Contaminated Sites in Fractured Sedimentary Rock
Beth ParkerNSERC Industrial Research ChairProfessor, School of Engineering
Solinst SymposiumGeorgetown, ONOctober 29, 2010
(shortened version for distribution)
Discrete Fracture Network Approach
PCE
Mackay and Cherry, 1989
DNAPLs Commonly Pass Through Overburden Into Bedrock
DNAPL source zone initial condition
Interbedded sandstone and shaleSandstone with shale interbeds
FracturedPorous Rocks
Bedding planes and joints in dolostone
Small Fracture Porosity and Large Matrix Porosity0.1 to 0.001% 2 to 25%
A
Microscopicview of rock
matrix
mineral particleDETAIL A
PLUMEZONE
SOURCEZONE
vadosezone
groundwaterzone
PLUMEFRONT
Nature of Contamination inFractured Sedimentary Rock
Requires a Different Approach
Matrix Diffusion Causes Plume Front Retardation
No DiffusionSolute front
With Diffusion and Sorption
non-porousmatrix
porousmatrix
With Diffusiont = 1
t = 1
time = 1
retardationporousmatrix
(Freeze and Cherry, 1979)
Critical Issues
Fracture network characteristics• Fracture aperture, spacing, • length and connectivity
Matrix properties• transport, storage and reactions
Discrete Fracture Network Field Approach
Use chlorinated solvent plumes as tracersNatural flow system conditions
DFN numerical models with appropriate (DFN) field and laboratory data for input / verification can realistically
represent and predict plumes in sedimentary rock
Premise
Questions: How many active fractures?
What is their Interconnectivity?
DenseNetwork
SparseNetwork
Sparse Fracture Network Yields Rapid Transport of TCE and Distant Plumes
South North2000
1500
1000
500
CA Site
Feet
abo
ve s
ea l
evel
0 5000 ft
Strong Retardation Restricts Expansion of TCE Plume
0 5000 ft
South North
2000
1500
1000
500
CA Site
Feet
abo
ve s
ea le
vel
Data Acquisition Framework for Site Characterization
Drill Corehole
Core Hole
Contaminant Analysis
Physical / Chemical Properties
Geophysics / Hydrophysics
Packer TestsK-Profiler
Multilevel Systems
Rock Matrix Fracture Networkuse lined holes almost exclusively
Obtain Data while Drilling
vadosezone
groundwaterzone
Core Hole for Rock Core Analyses in Areas of Previous DNAPL Occurrence
coredhole
0 1 10 100TCE mg/L
rock core
non-detect
Fractures withTCE migration
1
2
3
4
5
6
fractures coresamplesanalyzed
cored hole
Core Sampling for Mass Distribution &Migration Pathway Identification
DNAPL Disappearance from Fractures by DiffusionParker et al., Ground Water (1994)
Fracture Aperture2b
FractureSpacing
φfφm
H O2
DNAPLφf φm
DissolvedPhase
φfφm
DissolvedPhase
Early Intermediate Later Time
FORMER SOURCEZONE
vadosezone
groundwaterzone
PLUMEZONE
Current Site Condition: No DNAPL Remains and Plume Expands Very Slowly
Waterloo (Solinst) Removable
Modular System :
Installation in Progress
1998
California Site
Casing is Moved Towards Hole with Cables and Tubes Inside
Transducer & Double Valve Pump Attached to Each Port
Comparison of Multilevel and Rock Core Data:
Total TCE (μ g / g)
200
250
300
350
0.01 0.1 1 10
Pore water TCE (mg / L)
Dep
th (
feet
)0.01 0.1 1 10 102
multilevelzone
non-detects
Zone6
5
4
3
21
6
5
4
3
21
rock core35Bsimilar
dissimilardue to cross-contamination
Sterling et al. GW (2005)
Rock Core Results Show…
Numerous migration pathways hydraulically active, interconnected fractures
Open boreholes cause cross-contamination
ThereforeUse Rock Core AnalysisAvoid cross-connection
Prevention of Borehole Cross-Connection
Three methods exist
• FLUTe Liner
• Solinst Continuous Modular Packer
• Conventional Packers
FLUTe LinerUrethane Coated Nylon Fabric
Cherry, Parker and Keller (2007) GWMR
FLUTe liner pressed tightly against borehole wall to seal
without liner with liner
P.Pehme, 2006
Cross-Connected Not Cross-Connected
Depth Discrete Multilevel SystemsUse maximum number of ports!
FLUTe WestbaySolinst“Waterloo”
Westbay System
ExceptionallyDetailed
Head Profiles
38 ports
Abrupt inflectionsindicate unitboundaries
J.Meyer et al. 2009
FRACTRAN Simulations
Matrix for each unit has the same properties
Km = 10-6 cm/s
η = 15%
Average horizontal gradient ~ 0.01
Average vertical gradient ~ 0.03
Bulk Kh ~ 3.0 x 10-3 cm/s
Bulk Kv ~ 2.1 x 10-5 Meyer et al 2008
FRACTRAN SimulationsHead Profiles
0
5
10
15
20
25
30
35
40
45
7.0 7.5 8.0 8.5 9.0 9.5 10.0
Hydraulic Head (m)
Z (m
)
X=50mX=100mX=150m
Unit 1
Unit 2
Unit 3
Unit 4
Key Points
HGUs are partitions of the groundwater flow domain that are hydraulically consistent
HGUs are the framework for numerical modeling of groundwater flow and contaminant transport
Detailed head profiles are essential for delineating hydrogeologic units
J.Meyer et al. 2009
Summary
• Essential Methods for Contaminant Site Characterization in Sedimentary Rock
• Rock Core • Multi-Level Monitoring• Temporary Borehole Seals
• K-profiling• Temperature profiling in sealed boreholes
with lots of detail
minimize openhole conditions
Funding & Acknowledgements
Funding provided by site owners, NSERC and University Consortium for Field-Focused Groundwater Contamination Research
Support / collaboration with Westbay®, FLUTe™, and Solinst
The datasets presented are part of a larger research program and were collected by many graduate students, field technicians, research associates, and lab staff at the UoGuelph and UWaterloo
Key collaborators include John Cherry, Steve Chapman, Jessi Meyer
ReferencesCherry, J.A., B.L. Parker, and C. Keller. 2007. A new depth-discrete multilevel monitoring approach for fractured rock. Ground Water
Monitoring & Remediation 27, no.2: 57-70.
Keller, C.K., J.A. Cherry, and B.L. Parker. in submission. New method for continuous hydraulic conductivity profiling in fractured rock. submitted to Ground Water.
Meyer, J.R., B.L. Parker, and J.A. Cherry. 2008. Detailed hydraulic head profiles as essential data for defining hydrogeologic units in layered fractured sedimentary rock. Environmental Geology 56, no.1: 27-44.
Parker, B.L. 2007. Investigating contaminated sites on fractured rock using the DFN approach. In Proceedings of 2007 U.S. EPA/NGWA Fractured Rock Conference: State of the Science and Measuring Success in Remediation, September 24-26, 2007, Portland, Maine, Westerville, Ohio: National Ground Water Association.
Parker, B.L., J.A. Cherry, and B.J. Swanson. 2006. A multilevel system for high-resolution monitoring in rotasonic boreholes. Ground Water Monitoring and Remediation 26, no.4: 57-73.
Parker, B.L., S.W. Chapman, and J.A. Cherry. 2010. Plume persistence in fractured sedimentary rock after source zone removal.Ground Water, in press.
Pehme, P.E., B.L. Parker, J.A. Cherry, and J.P. Greenhouse. 2010. Improved resolution of ambient flow through fractured rock with temperature logs. Ground Water 48, no.2: 191-205.
Sterling, S.N., B.L. Parker, J.A. Cherry, Williams, Lane and Haeni. 2005. Vertical x-connection of TCE in a borehole in fractured sandstone. Ground Water 43, no.2: 557-573.
Sudicky, E.A. and R.G. McLaren. 1992. The Laplace transform Galerkin technique for large-scale simulation of mass transport in discretely fractured porous formations. Water Resources Research 28, no.2: 499-514.