Managing Your
Groundwater Program Do’s and Don’ts
Matthew Daly, P.G.
2007 RETS-REMP
Philadelphia, PA
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Groundwater Programs
• Non-nuclear – thousands of sites over the past 30 years
• Gas stations and bulk terminals
• Dry cleaners
• Manufacturing facilities
• Landfills
• Myriad of contaminants and site conditions
• NAPLs, solvents, metals, PAHs….
• Sand, silt, clay, fractured bedrock, sediment and surface
water
• Well depths from 15 to 300+ feet
• Sampling methods, frequency and parameters
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Groundwater Programs – cont’d
• Lessons learned can help to streamline and
maximize effectiveness of groundwater programs
at nuclear power plants
• Planning with the end in mind – REMP
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The Six Components of
Effective Groundwater Monitoring Programs
Calculate
Tritium Flux
Component
Assemble
Project Team
(1)
Identify Sources,
Receptors and
Plant Influences
(2)
(6)
Groundwater Monitoring Program
Implement
Monitoring
Program
(5)
Implement
Phased Field
Investigation
(4)
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Develop &
Refine Initial
Conceptual
Model
(3)
Assemble Project Team
Corporate
External
Stakeholder
Interests
Plant
Operations
Use
Internal and External
Resources
Data
Validation &
Management
Specialists
Health
Physicists &
Engineers
Geologists
Hydrogeologists
Subcontractors
Drilling &
Laboratory
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Field
Technicians/
Specialists
Identify Sources
• Identify known or potential sources of liquid
release to groundwater, e.g., Spent Fuel Pool,
piping, sumps, tanks, spills, etc.
• Tritium most common, but Cobalt-60, Cesium-137
and Strontium-90 also found.
• Consider hierarchy of potential sources based on
magnitude, age, duration, exposure potential to
receptors and logistics of investigation.
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Identify Sources – cont’d
• Source Identification – Continue to evaluate
throughout program to identify, control and
eliminate where feasible.
• Evaluation of Systems and Components
• Evaluation of Procedures and Past Practices
• Evaluation of Available Groundwater Monitoring
Results
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Identify Receptors
• Groundwater Usage Survey
• Springs
• Surface water
• On-site and off-site water supply wells
• Receptor Analysis – Early in program to reinforce
lack of risk posed and build stakeholder
confidence
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Sources & Receptors – Use Existing Data
• FSAR & USAR geologic and hydrogeologic
reports
• Plant drawings and construction diagrams
• 50.75(g) Files
• Locate, inventory and sample existing wells
• REMP program
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Develop Conceptual Site Model
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Refine Conceptual Site Model
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Implement Phased Field Investigations
• Design site assessment program to achieve
project goal(s)
• Characterize site geology and hydrogeology to the
extent necessary
• How do they affect contaminant distribution,
migration and attenuation
• Define contamination source, nature and extent
• Don’t exacerbate site conditions – work from
“outside-in, top-down”
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Drilling Techniques
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Unit Cost / well
Drilling Technologies
Rotosonic
Telescope
Casing
Hollow Stem
Auger
Geoprobe
Investigation Depth
Degree of Conservatism
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Overburden Investigation Tools
Monitoring Wells
Multilevel wells
Cost
Waterloo Profiler
Soil borings
Cone
Penetrometer
Qualitative
Quantitative
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Bedrock Investigation Tools
Long open boreholes
Pumping Tests
Packer Tests
FLUTe
Rock coring
Cost
Multilevel wells
Surface geophysics
Air rotary
Borehole geophysics
Transducers
Qualitative
Quantitative
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30
30
20
20
10
10
0
0
-10
-20
-10
0
2
4
6
8
10
Index of Hydraulic Conductivity
(unitless)
23 24
25
26
27
28
Hydraulic Head
(feet)
29 100 200 300 400 500 600
4
5
Specific Conductance
(uS/cm)
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6
pH
7
0
2
4
6
Dissolved Oxygen
(mg/L)
8 -200
-100
0
100
-20
200
Oxidation/Reduction Potential
(mV)
Elevation (ft)
Elevation (ft)
Heterogeneity – Variability of Subsurface Aquifers
Data Representativeness
40'
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0
Scale
40'
80'
160'
Aquifer Testing – Determine Groundwater Flow
Rate
• Hydraulic conductivity (K)
• Field test to “stress” a well and monitor response
in the groundwater level
• Examples include slug, pumping and tracer tests
• Need to consider scale effects
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Aquifer Testing – Tools for Determining K
Tracer Test
Cost
Pumping Test
Slug Test
Degree of Certainty in K value
Volume of Aquifer Tested
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Implement Monitoring Program
• Select groundwater sampling method(s)
• Select analytical parameters
• Implement quality assurance/control program
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Groundwater Sampling Methods
• Various techniques
• Bailer, thief, grab, diffusion bag, low-flow
• Low yield wells need special attention
• Low-flow considered most robust for obtaining
representative groundwater samples (EPA, State
and EPRI Draft Guidance)
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Groundwater Sampling – Methods
Low-flow
3-well volumes
Cost
Diffusion Bags
Thief
Grab
Representativeness
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Low-Flow Groundwater Sampling
Stabilization Parameters:
•Temperature
•Conductance
•pH
•Redox Potential
•Dissolved Oxygen
•Turbidity
•Water Level
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Selection of Analytical Parameters
• Radiological
• Tritium
• Gamma
• Hard to Detects?
• Non-radiological?
• VOCs (solvents)
• PAH (fuels, oils)
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Date
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04
04
01/
08/
14/
01/
03
28/
06/
02
02
10/
12/
24/
05/
01
05/
01
Concentration (ug/L)
Species A
250
155.00
200
150.00
150
145.00
100
140.00
50
135.00
0
130.00
Water Level Elevation (ft asl)
300
11/
19/
04/
00
00
01/
10/
15/
03/
99
28/
08/
99
98
09/
02/
24/
07/
98
97
05/
01/
19/
06/
96
01/
12/
96
95
15/
05/
28/
10/
95
11/
04/
Consider Monitoring Frequency
160.00
Species B
Water Level Elevation
Implement QA/QC Program
• Laboratory Quality Control Issues
• Verify appropriate and consistent Lower Limits of
Detection
• Need to consider site-specific background levels
• Need to consider State and Federal reporting
levels
• Reporting units (pCi/L versus mCi/ml)
• Third party analysis of duplicate samples
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Implement QA/QC Program – cont’d
• Field Quality Control Methods
• Duplicate/Blind Samples
• Matrix Spike & Matrix Spike Duplicate
• Equipment Blanks (Decontamination)
• Performance Evaluation Samples
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Tritium Flux Component
• What is it?
• How many curies of tritium are being discharged through
groundwater
• Why calculate?
• Account for released tritium to groundwater as part of ODC
• How to calculate?
• 1st Approximation Method – combine Darcy’s Law for
groundwater flow and concentration data from sample results
• Calibrated groundwater flow model
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Tritium Flux Component – cont’d
• Groundwater Discharge (Q) using Darcy’s Law:
Q  KA
dh
dl
• Q = groundwater discharge rate within plume [Liters/day];
• K = hydraulic conductivity from aquifer test [m/day];
• A = cross sectional area perpendicular to groundwater flow and
plume [m2]; and
• dh/dl = hydraulic gradient calculated from wells [unit-less].
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Tritium Flux Component – cont’d
• Tritium Flux [mCi/day] = Concentration x Groundwater
Flow Rate
• Concentration [pCi/L] – groundwater monitoring
results
• Groundwater Flow Rate [L/day] – Darcy’s Law
• Apply unit conversions for mCi/day
• Calculate tritium flux over REMP reporting period
(quarterly, annually, etc.) for mCi released
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Pitfalls to Avoid
• Don’t treat all sites as equal
• Don’t assume plumes are static (new releases,
seasonal effects)
• Don’t just look shallow – releases can occur below
the water table (plant construction and geology)
• Don’t drill deep in a potential source area unless
rigorous controls are in place (crosscontamination)
• Don’t expect all answers to questions after one
round of investigation and sampling (phased
approach)
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Low-Flow Sampling - References
• Puls, R.W., and Barcelona, M.J., April 1996, “Low-Flow (Minimal Drawdown)
Ground-Water Sampling Procedures”. EPA Ground Water Issue. EPA/540/S95/504.
• U.S. Environmental Protection Agency, July 30, 1996. “Low Stress (low flow)
Purging and Sampling Procedure for the Collection of Ground Water
Samples from Monitoring Wells”. Region I. SOP #: GW 0001.
• U.S. Environmental Protection Agency, May 2002. “Ground-Water Sampling,
Guidelines for Superfund and RCRA Project Managers” stagnant water
removal procedure.
• Yeskis, D., and Zavala, B., May 2002. “Ground-Water Sampling Guidelines
for Superfund and RCRA Project Managers”. Ground Water Forum Issue
Paper. EPA 542-S-02-001.
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Questions?
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