Transcript New Groundwater Techniques and Technologies 17th Annual RETS REMP Conference June 25-27, 2007 Eric L.

New Groundwater
Techniques and
Technologies
17th Annual RETS REMP Conference
June 25-27, 2007
Eric L. Darois, CHP
EPRI Consultant/RSCS Inc.
Project Scope
• Evaluate New and Current Technologies for Groundwater
Sampling
• Evaluate New and Current Technologies for
Contaminated Groundwater Detection
• Evaluate New and Current Technologies for
Contaminated Groundwater Remediation
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Technology Conferences
• 7th Passive Sampling Workshop and Symposium, Reston
Virginia, United States Geological Survey (USGS), April
2007
• 2007 Ground Water Summit, Albuquerque New Mexico,
National Ground Water Association (NGWA), April 2007
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Passive Sampling Technologies
• SPMD’s
– Semi-Permeable Membrane Devices (SPMD’s)
– These accumulate contaminants within an absorption media, typically a polyethylene
absorption media.
• The Gore Module
– Developed exclusively produced by and for GORE-TEX®
– Similar to SPMD’s, does not collect a sample of water, uses a patented absorption
material.
– Consists of a tube of GORE-TEX® fiber containing absorption beads.
– Has pore sizes large enough to allow volatile and semi-volatile gas phase
contaminants to diffuse and to accumulate on the absorption material.
– Pore size restricts liquid phase water from entering the sampler.
• PDBS
– Passive Diffusion Bag Samplers (low-density polyethylene diffusion bag samplers)
– Collects groundwater samples using a tube of Low Density Polyethylene (LDPE).
– Fits into a 5 cm dia. well.
– Filled with DI Water, sealed at both ends and lowered into Well.
– Averages Concentration over 1 – 2 weeks – no additional equipment
• RCDMS
– The Regenerated Cellulose Dialysis Membrane Sampler (RCDMS)
– Similar to the PDBS.
– Pore size between 5-20 microns.
– May Be Susceptible to Degradation
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Passive Sampling Technologies (con’t)
• RPP
– The Rigid Porous Polyethylene sampler (RPP)
– Also Similar to PDBS and RCDMS
– Porous polyethylene membrane with pore sizes ranging between
6 and 15 microns.
– Limited to 100mL sample
• The Snap Sampler
– Groundwater passive grab sampler.
– Device consists of a sample bottle, trigger lines, end caps and springs
– Sample Volumes of 40 and 125 mL.
• The Hydra Sleeve
– Groundwater passive grab sampler.
– Disposable thin-wall sleeve of polyethylene sealed on the bottom and
fitted with a one way reed valve on the top.
– Effectively Collects a Core of Water ~1000 mL
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Passive Sampling Comparisons
Diffusion
Sampler
Grab
Sampler
Commercially
Available
X
X
Snap
Sampler
RCDMS
RPP
X
X
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Easy to
Use
X
X
Hydra
Sleeve
Disposable
Limited by
Sample
Volume
X
X
X
X
X
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X
X
X
Tritium Groundwater Contamination Detection
Soil Vapor Extraction System (SVES)
• Current EPRI Research Initiative
• 4 Project Phases
– 1 Develop Predictive Model
– 2 Laboratory Testing of Model
– 3 System Test at a Decommissioning Site with
Characterized H-3 Plume
– 4 System Test at Operating NPP
• Currently Beginning Phase 2
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SVES Basis
• Research Currently at the Armagosa Desert Research
Site
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SVES Principle
• Extract Soil Vapor from Vadose Zone
• Condense Vapor, Analyze for H-3
• The Vadose Zone H-3 Vapor “Plume” Likely Extends Well
Beyond Contaminated Groundwater
• If the H-3 Vapor is Within the Extraction Zone of Influence,
Detection will Occur.
• System May Provide Early Indication of H-3 Subsurface
Leak.
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Project Objectives
• Determine Physical System Configuration Requirements
• Determined Required Data for System Installation
• Evaluate Sensitivity of SVES to “detect” Groundwater
Contamination
• Provide for Data Assessment Methodologies
• Prediction of:
– Soil Gas Velocity
– Radius of Influence
– Subsurface Release Activity
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SVES Model
• Principal Parameters
– Soil Gas Velocity, q
– Air Permeability, and
– Pressure Gradient.
q 
d isc har ge ve lo c ity (d isc har g e) [ m /s ]
ka 
a ir p er m eab ility [ m ]
 
v isco s ity o f a ir [k g /m /s]

ka

P
k a  k ra k i
ki 
ksw
Pw g
Figure 1.1
Typical Relationship Between Vacuum vs Radius from
the Extraction Point
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 P  in sta n ta neo us p r ess ure g rad ie n t [ (k g/m /s )/m ]
2
k s=
µ w=
P w=
g=
Vacuum
satura ted hydra ulic co nd uc tivity [ m/s]
viscos ity o f w ate r [k g/m/s]
3
dens ity o f w a ter [ m /k g]
2
acce lera tio n d ue to gra vity [ m/s ]
Radius
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Model Assumptions
•
•
•
•
•
The thickness of the vadose zone is relatively constant,
homogeneous and isotropic within the extraction point’s ROI, i.e.
construction backfill.
An impervious or semi-pervious surface barrier to atmospheric gas
transfer and direct infiltration of precipitation to the vadose zone is
in place, i.e. pavement or concrete.
A detection or change in condensate activity concentration is due
to a soil vapor plume entering the ROI of an extraction point and is
not the result of diffuse background H-3 activity in the soil.
The approximate cross-sectional area OR volume of contaminated
soil AND the approximate distance from the extraction point can be
determined.
Soil vapor within the capillary fringe of the liquid plume has the
same activity concentration as the liquid release.
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Conceptual Design
• Each Extraction Capable
of Covering Large Areas
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Specific Discharge and Capture Ratio
• Specific Discharge Within Plume Front
Q pf  ( b  b ' )  ( c  c ' )  q r
b-b’=
c-c’=
q r=
plume w idth [ m]
plume dep th [ m]
so il gas ve loc ity a t the p lume fro nt rad ius [ m/s] ;
• Total Discharge at Plume Front, Qr
• Geometric Capture Ratio, C  Q
pf
Qr
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Ideal and Non-Ideal Conditions
• System is More Effective with Concrete or Asphalt Cover
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Cylinder-Sphere Model – Non-Ideal

(T  r )( ros  ros )   4 r 2 
A   2 ( r ) 

  ( 2 r c t ) 
2
r
2


os


Total Surface Area
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 4 r

 2
2



Additional Model Considerations
• Thick Vadose Zone
• 3-D Rendering to Determine Shape Surface Areas
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SVES Benefits
• Fewer GW Monitoring Wells
• More Effective Sentry System
• Onsite Analysis for H-3
• More Effective Early Warning Methodology
• Less Dependent on Precise Placement
• Less Invasive (Push-Probe Installation Method) than
Traditional GW Monitoring Well
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Project Schedule
• Phase 1 – Complete
• Phase 2 – 12/31/2007
• Phase 3 & 4 – 12/31/2008
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