Dioxin Remediation at the Da Nang Airport
Transcript of Dioxin Remediation at the Da Nang Airport
Eleventh International Conference on Remediation of Chlorinated and Recalcitrant CompoundsApril 8‐12, 2018 | Palm Springs, California
April 9, 2018
Dioxin Remediation at the Da Nang Airport
Using the Incremental Sampling Methodology for Soil and Sediment Confirmation Sampling
Alexis LópezKent SorensonRanda ChichakliJeff BamerDan Moats
Outline
Introduction Site Background Remediation Activities ISM Confirmation Sampling Results Conclusions
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Introduction
Over 43 million liters of defoliants brought to Vietnam
Agent Orange was contaminated during production
2,3,7,8‐TCDD is toxic at low (ppt) concentrations
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Site Background
Danang and Bien Hoa were major U.S. airbases during the war
In Danang, civil and military airport In Bien Hoa, military airport >20 million liters of Agent Orange
used at both sites Residents nearby at risk Some elevated dioxin in blood serum
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Site BackgroundDanang EA Samples were collected
from 1997 through 2010 EA performed in 2009
and 2010 150 discrete and 10‐pt
composite samples Vietnam standards as
total dioxin TEQ: 150 ppt sediment, 1,000 ppt soil
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Site BackgroundDanang EA Total remediation area: 19.3 Ha Remediation areas
MLA – Mixing and Loading Area SA – Storage area DD – Drainage Ditch SL – Sen Lake EW – Eastern Wetland EH – Area Between Eastern Wetland
and Drainage Ditch Conceptual Site Model:
Spills in MLA and SA, erosion to DD, EW and SL
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Site BackgroundBien Hoa EA Samples were collected
from 2006 to 2015 EA performed in 2014
and 2015 438 full DU and sub‐DU
samples collected Vietnam standards as
total dioxin TEQ: 150 ppt sediment to 1,200 ppt soil (industrial)
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Site BackgroundBien Hoa EA Total area to be
remediated: >52 Ha Future remediation areas
Z1 – main storage area SA – southwest area PI – Pacer Ivy area NW – northwest area NE – northeast area
Conceptual Site Model: Dioxin in Z1 to sediment &
fish, and in SW to PI to sediment & fish
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Danang Remediation ActivitiesApproach Built a containment/treatment
structure Excavated contaminated soil and
sediment Placed in structure Confirmed excavation areas are
clean Treated the soil Re‐used treated soil
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Danang Remediation ActivitiesExecution Divided into two treatment
phases Space and electrical
constraints on treatment structure
Designed volume of contaminated material was too much to fit into one treatment structure.
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Danang ISM Confirmation SamplingConfirmation Sampling Needs Needed a reliable methodology
to confirm concentrations left in place meet standards Large area Significant heterogeneity High cost of analytical
Incremental Sampling Methodology (ISM)
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ISM Confirmation SamplingISM Primer Following 2012 ITRC guidance What is ISM?
Structured composite sampling and processing protocol
Reduces data variability Provides a single sample for
analysis with a concentration representative of the mean concentration of a “decision unit” (DU)
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ISM Confirmation SamplingISM Primer ISM minimizes short‐scale
heterogeneity >30‐pt composite in field
ISM minimizes micro‐scale heterogeneity Sample conditioning Particle size reduction
(sieving) 30‐pt composite sub‐sampling
(systematic random)
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ISM Confirmation SamplingSample Preparation After sampling
Homogenize Sieve Spread into thin layer Systematic random: sub‐sample 30 aliquots Place in lab cleaned container Store in freezer
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ISM Excavation Confirmation SamplingApplication to Danang Excavation DUs based on understanding of
contaminant distribution and conceptual model
Bottom of excavation is a DU Each sidewall is a DU Subdivision of DUs to gain
additional resolution
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ISM Characterization SamplingApplication to Bien Hoa EA Must determine average
concentrations in areas across the site
DUs based on understanding of potential contaminant distribution/historical documentation
ISM used to collect samples Numerous triplicate samples
collected
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ISM Treatment Confirmation SamplingApplication to Danang Treatment Must confirm average
concentration <150 ppt Pile divided into six, 1‐m
decision units vertically (DU layers)
Modified “pot‐holing” used to collect samples
Triplicate collected for one layer
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Results Danang EA samples 89 samples grouped by depth
into 25 remediation decision units
Discrete or 10‐point composite High CV between samples from
most areas Low cost to collect, but more
samples for analysis
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0%20%40%60%80%
100%120%140%160%180%200%
0 2 4 6 8 10
CV
Number of Samples
0%
50%
100%
150%
200%
CV
Avg=97%
Results Bien Hoa EA Triplicate samples Samples grouped by remediation
decision unit Minimum 30‐point composite 24 triplicates collected Low CV between samples from
most areas = higher confidence Higher cost to collect, but less
samples for analysis
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0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
CV
Avg=31%
Results Phase 1 Final Sample Results (May 2015)
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0 10 20 30 40 50 60 70
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2
3
4
5
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Phase 1 Post‐treatment TEQ (pg/g)
Depth (m
)
95% UCL = 2.6 pg/g
Results Phase 2 Final Sample Results (June 2017)
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0 1 2 3 4 5 6 7 8 9 10
1
2
3
4
5
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Phase 2 Post‐treatment TEQ (pg/g)
Depth (m
)
95% UCL = 0.24 pg/g
Conclusions
ISM did NOT “dilute” high concentration hot spots Revealed larger volume requiring treatment than discrete samples Confirms discrete samples give many false negatives in moderately
contaminated areas
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Conclusions ISM for confirmation sampling was successful
Provided data on whether the project goals were achieved Provided data on how additional excavation should be performed
ISM used for the BH EA provided a more accurate representation of the mean than traditional methods used during the Danang EA
Triplicates showed that ISM likely did not underestimate the “true” average dioxin concentrations within a DU
Based on experience from Danang, using the ISM for pre‐ and post‐excavation samples showed ISM can more reliably determine the limits of excavation
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Acknowledgements
The Danang Airport and Bien Hoa Airbase projects were funded by USAID, and USAID has approved CDM Smith'suse of the project data for this presentation.
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