LNAPL Transmissivity (T n ) Remediation Design, Progress and Endpoints H 2 A Environmental, Ltd. J. Michael Hawthorne, P.G. [email protected] www.h2altd.com September 2010
Dec 16, 2015
LNAPLTransmissivity (Tn)
R e m e d i a ti o n D e s i g n , P r o g r e s s a n d E n d p o i n t s
H2A Environmental, Ltd.
J. Michael Hawthorne, [email protected]
www.h2altd.comSeptember 2010
Outline
• LNAPL multi-phase fluid mechanics review
• LNAPL metrics review
• LNAPL transmissivity (Tn) principles
• Applicability
• Summary
Intr
oduc
tion
LNAPL at the Pore Scale
• LNAPL co-exists with water in aquifer pores
• LNAPL only partially fills the aquifer pore space
• The degree of LNAPL saturation depends upon lithology and fluid properties
Sediment GrainsWetting Fluid (Water)
Non-Wetting Fluid (Air or LNAPL) Filling Large Pore Spaces
Mul
ti-Ph
ase
Flui
d M
echa
nics
RTDF 2006
Ideal vs. Observed LNAPL Saturations
RTDF 2006
Mul
ti-Ph
ase
Flui
d M
echa
nics
Saturation curve height = thickness of mobile LNAPL interval
T vs. Tn / Tn vs. Sn
• Transmissivity (T) for water– Unit cross-section, gradient, time– Aquifer thickness
– Single fluid (krw drops out)
• LNAPL Transmissivity (Tn)– Unit cross-section, gradient, time– Mobile LNAPL interval thickness
– Multi-fluid (krn matters)
w
rwww
gkkK
n
rnnn
gkkK
bKT ww
nnn bKT
Mul
ti-Ph
ase
Flui
d M
echa
nics
“How Much, How Fast”
Ideal LNAPL Metric
• Collective property incorporates: – Aquifer properties (e.g., permeability)
– Aquifer type (sand vs. clay)
– LNAPL properties (e.g., viscosity)
– LNAPL type (condensate vs. crude oil)
• Fundamental or characteristic property – Repeatable
• Saturation / mass driven
• Easy and cheap to measure
LNAP
L M
etric
s
Non-Ideal Metrics - ThicknessLN
APL
Met
rics
• Same mass exhibits different thicknesses in different soil types
• Inconsistent under varying hydrostatic conditions
Modified after RTDF (2006)
Modified after Kirkman (2009)
Non-Ideal Metrics – Recovery DataLN
APL
Met
rics
Benefits• Direct measure of remediation
performance
• Provides predictive data for decline curve analysis
Problems
• Strongly affected by system operational settings
• Varies by technology – not directly comparable
• Can’t be used to predict performance prior to startup
Tn – An Improved Metric
Tn Advantages
• Direct numeric measure of hydraulic recoverability
• Varies directly with LNAPL saturation / mass
• Normalizes all sites to a single measurement standard
• Multiple Methods
• Measurable prior to, during and after remediation
LNAP
L M
etric
s
LNAPL Transmissivity (Tn)
• Analog to aquifer transmissivity• Provides basis for mobility /
recoverability analyses• Four measurement methods
– Baildown / skimming tests– Recovery data analysis
• skimming• Vacuum enhanced skimming• Total fluids pumping• Multi-phase extraction
– Physical properties / modeling– Tracer tests
• Hydraulic recovery only• Dissolved and vapor phase risk
issues are separateTran
smis
sivi
ty (T
n) Prin
cipl
es
Applicability – Uses for Tn
1. Alternative to laboratory Sn
2. Model calibration parameter3. Technical impracticability threshold4. Remediation design parameter5. Operational progress metric6. Recovery end point
Appl
icab
ility
Applicability - TI DemonstrationAp
plic
abili
ty
3. Technical Impracticability (TI) requires either:– Recovery system data
• “Can I please turn it off now?”• Direct recoverability threshold metric
– Data from a pilot test and modeling study• “Can I please not turn it on?”
• Robust calibration parameter for TI modeling
Applicability – Remediation Design
4. Remediation design parameter– Compare different technologies (calibrated model)
• Technology-specific production curves• Predicted rate and total volume decline curve analyses• Sustainability
– Design parameters• Equipment sizing• Waste management / recycling volumes
– Design cost-benefit analysis• Projected operational lifetime• Capital vs. mobile infrastructure
Appl
icab
ility
Applicability – Operational Progress5. Operational Progress Metric
– Recovery data decline curve analysis (progress towards endpoint)
– Non-recovery wells to monitor plume progress to endpoint
Appl
icab
ility
Tn Endpoint Analysis
6. Hydraulic recovery end point (0.3 to 0.8 ft2/day)
Appl
icab
ility
(Kirk
man
201
0)
Tn Endpoint AnalysisAp
plic
abili
ty
Summary
• Tn is an improved metric for hydraulic recoverability
• Four calculation methods:– Baildown / manual skimming testing– Recovery data analysis– Physical properties analysis– Tracer testing
• Tn use as a metric– Indirectly as a robust model calibration parameter– Directly as a recoverability threshold (0.3-0.8 ft^2/day)
• Remediation and Tn
– TI threshold– Design parameter – End point for hydraulic recovery
Sum
mar
y