New Groundwater Techniques and Technologies 17 th Annual RETS REMP Conference June 25-27, 2007 Eric L. Darois, CHP EPRI Consultant/RSCS Inc.

New Groundwater Techniques and Technologies

17th Annual RETS REMP Conference

June 25-27, 2007

Eric L. Darois, CHP

EPRI Consultant/RSCS Inc.

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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

DisposableLimited by

Sample Volume

Easy to Use

Snap Sampler X X X

RCDMS X X

RPP X X X X X

Hydra Sleeve X X X X

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Tritium Groundwater Contamination DetectionSoil 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,

– Air Permeability, and

– Pressure Gradient.

Pkaq

q discharge velocity (discharge) [m/s]

ak air permeability [m2] viscosity of air [kg/m/s]

P instantaneous pressure gradient [(kg/m/s2 )/m]

iraa kkk gP

kk

w

wsi

ks= saturated hydraulic conductivity [m/s] µw= viscosity of water [kg/m/s] Pw= density of water [m3 /kg] g= acceleration due to gravity [m/s2]

Figure 1.1Typical Relationship Between Vacuum vs Radius from

the Extraction Point

Radius

Vacuum

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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

• Total Discharge at Plume Front, Qr

• Geometric Capture Ratio,

rpf qccbbQ )'()'(b-b’= plume width [m] c-c’= plume depth [m] qr= soil gas velocity at the plume front radius [m/s];

r

pf

Q

QC

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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

2

4)2(

2

4

2

))(()(2

22 rcr

r

r

rrrTrA t

os

osos

Total Surface Area

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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