1

Passive Soil Gas Sampling: A Cost Effective Approach to Identify Source Areas

and Vapor Intrusion Pathways, Delineate Contaminant Plumes, and Optimize

Remediation Systems

By: Harry O’Neill

Beacon Environmental Services, Inc.

May 3, 2012

Presented to: U.S. EPA Technical Support Project

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Road Map

• Passive Soil Gas (PSG): Background and Technology

• Why PSG Surveys: Spatial and Temporal Variability of VOCs/SVOCs in

the Subsurface

• QA/QC Procedures: In the Field and In the Lab

• How to use PSG Data

• Case Study: Application and Results Targeting Source Area and

Delineating PCE Plume

• Conclusions

• Resources -- New Guidance Documents Available

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Experience -- The Company

• Beacon Environmental formed in 1999 with the focus of providing site characterization solutions through the use of advanced passive soil gas (PSG) sampling methodologies.

• Beacon provides PSG services throughout the United States, as well as internationally, and continues to improve upon the process and understanding of subsurface vapor movement.

• Beacon supports the research community by aligning ourselves with several prominent universities to further the understanding of soil vapor dynamics and develop innovative sorbent based sampling and analytical methods for soil gas, indoor air, and ambient air applications.

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Experience -- The People

• Beacon’s staff has managed soil gas investigations for more than 20 years working on both industrial and military projects.

• We have been on the forefront of the acceptance of passive soil gas sampling technologies at both the national and international level and have overseen the implementation of over one-thousand soil gas surveys.

• Harry O’Neill is the lead author of the recently drafted ASTM Standard: D7758-11, Standard Practice for Passive Soil Gas Sampling in the Vadose Zone for Source Identification, Spatial Variability Assessment, Monitoring, and Vapor Intrusion Evaluations.

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BESURE Sample Collection Kit

Passive Soil Gas Technologies are typically provided through easy to use sample collection kits.

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Easy-to-Use in the Field

PSG Technologies are easy to use and are designed to maintain high quality control (QC) in the field

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ASTM D5314 and D7758 Compliant Sampler

The sorbents need to be hydrophobic and the housing of the PSG Samplers should not contain sorptive materials (e.g.,

PDMS or other membranes) that will compete with the sorbents and bias results

Two types of adsorbents to target a broad

range of compounds

Two pairs for duplicate or confirmatory

analysis

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Applications

• Identify source areas and release locations of VOCs/SVOCs

• Focus soil and groundwater sampling locations

• Focus remediation plans

• Identify vapor intrusion pathways

• Track groundwater plumes

• Monitor remediation progress

• TRIAD Approach – Expedited Site Characterization

PSG surveys are routinely performed to:

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Routine Targets

Halogenated compounds • PCE • TCE • DCEs • Vinyl chloride • TCA • Carbon tetrachloride • Chloroform • Freons • Chlorobenzene • Dichlorobenzenes • Trichlorobenzenes

Complex mixtures • Stoddard solvent • Paint thinners Petroleum Blends • Gasoline • Fuel oil • Diesel • Jet Fuel BTEX, MTBE and PAHs • Naphthalene • 2-Methylnaphthalene

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Additional Targets

Heavier PAHs • Acenaphthalene, Fluorene, Pyrene

Ketones

Alcohols

Explosives

Pesticides

Chemical Warfare Agent (CWA) and Breakdown Products

• Mustard, GB, VX, 1,4-Thioxane, 1,4-Dithiane, Thiodiglycol

Mercury (Hg)

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• Maximize the number of locations that can be sampled

• Reduce uncertainty, surprises, and unforeseen costs

• Make well-informed and appropriate corrective action decisions

• Rapidly collect accurate data

Why PSG Surveys? – Spatial Variability

Benefits of PSG Surveys:

Overcome the challenges of SPATIAL VARIABILITY of subsurface contamination by allowing you to collect a high resolution data set

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Why PSG Surveys? – Temporal Variability

Overcome the challenges of the TEMPORAL VARIABILITY of soil gas concentrations by collecting time-integrated measurements over several days or weeks

Soil gas concentrations can change daily and

even hourly at the same location.

On which day and at what time should you collect an

active soil gas sample? Chart courtesy of

Ion Science

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Why PSG Surveys? – Cost Saving Approach

"If we had not had the soil gas data we would have taken 200 borings (identified by ground penetrating radar) across the entire site. Instead we were able to drill only about 40 borings, which resulted in excellent data.” – Bhate Environmental

High Density, Low Cost Low Density, High Cost

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Why PSG Surveys? – Versatile Technology

Passive Targets a Broader Range of VOCs and SVOCs than Active

Effective in Most Soil and Geologic Conditions

Time Integrated… able to identify contamination at low concentrations

“The Circles of Trust”

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Sustainable Technology

IN THE FIELD No waste from soil cuttings are generated when sampling.

Only hand tools required to collect samples -- no DPT or drill rigs. In-situ sample collection onto adsorbents that are reused, no waste.

IN THE LAB Samples analyzed using thermal desorption-gas chromatography/

mass spectrometry (TD-GC/MS) instrumentation. No solvents are used for sample extraction.

Green CharacterizationTM

A green site investigation relies on information gained from a thorough preliminary assessment that identifies target areas and

site conditions through minimally intrusive techniques. -- USEPA OSWER Dec. 2009

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Precision In Sampler Design

Each PSG Sampler is made of inert materials in accordance w ith ASTM protocols – no membranes are used which can act as competing adsorbents

Each PSG Sampler contains an equal mass of hydrophobic

adsorbents weighed out w ith an analytical balance

Important for consistency of sampling from one location to another and allows for excellent reproducibility and precision,

as demonstrated w ith duplicate field samples

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Precision In The Lab

• Analysis by thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) following EPA Method 8260C or equivalent

• Analytical results based on 5-point initial calibration

• Internal standards and surrogates included with each analysis

• Daily continuing calibration checks

• Duplicate field samples

• System daily tunes

• Method blanks

• Method Detection Limit (MDL) Studies

• Meets requirements of EPA Level III/Level IV data quality objectives

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Survey Reports

Reports are provided with a narrative discussing QA/QC findings and include tabular results, as well as color isopleth maps showing distribution of compounds.

Options:

EDDs (e.g., SEDD 2A)

EPA CLP Summary Forms

Surrogate Results

TICS

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Reported Data in Units of Mass… Not Concentration

PSG data should not be reported in units of concentration No agencies or regulators accepting PSG data converted to concentration All soil gas guidance documents clearly state data not to be used for determining concentration However, reporting data in units of mass (ng or ug) meets project objectives to characterize sites and guide where to collect a limited number of soil, gw, or active soil gas samples

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Temporal Variability

Separate objective is to determine the average or worst case soil gas concentrations

Soil gas concentrations can change daily and

even hourly at the same location.

On which day and at what time should you collect an

active soil gas sample? Chart courtesy of

Ion Science

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Applications

EXAMPLE PROJECTS

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V02Scale in Feet

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12,203

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23-123-223-323-423-523-623-723-8

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Example Project: Manufacturing Site Investigation

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Example Project: Gas Station Investigation

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Example Project: DOD Site – Identify Fuel Releases

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Example Project: DOE Site – Identify Legacy CCl4

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Example Project: TCE Source Area and Plume

22-122-222-3

23-123-223-323-423-523-623-723-8

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55-2

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A-1A-2A-3A-4A-5A-6A-7A-8A-9A-10A-11

B-1B-2B-3B-4B-5

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Case Study: Identify Source Area and Track Plume

Objective: Identify Source of PCE in Monitoring Well

PCE concentration in groundwater is 6.8 ug/L

Challenges: Urban Environment Multiple potential source areas present Gaining access to properties difficult PCE concentration at low ppb level in gw at 5 m depth

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OVERALL GRID PATTERN 74 PSG Samplers

Sampled near PRPs and in public right of ways.

Groundwater was approximately 5 meters bgs

10 m spacing near two dry cleaners

Typically 30 m spacing along public right of ways

Case Study – PSG Sampling Plan

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Case Study – PSG Sampling Plan

GRID NEAR DRY CLEANERS

Locations of former and active

dry cleaners

Location of MW-1 which reported 6.8 ppb of PCE

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Definitively identified PCE releases from

former and active dry cleaners.

Non-Detects Excluded out other PRPs

Tracked plume to downgradient well contaminated with

PCE by sampling in public right of ways.

Case Study – Results

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Case Study – GW Results

PSG Data and GW data correlated very well

GW data isoconcentration maps confirming PSG findings

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Case Study – Findings

Findings: • PSG data for PCE ranged from non detects to 29,117 ng

• Sources of PCE releases were identified

• PCE measurement of 29,117 ng equated to 17,000 ug/L in gw

• PSG data identified migration pathways from source areas to impacted monitoring well – plumes commingled

• PCE measurement of 125 ng equated to 6.8 ug/L in gw – SENSITIVE METHOD

Client Stated: “The PSG survey proved to be a cost-effective method to identify the source areas and the extent of the PCE plume. A minimal number of soil borings to collect grab groundwater samples was required to confirm the results of the passive soil vapor survey, thus minimizing costs.”

Reference: Clarke, Goodwin, O’Neill, Odencrantz, Preliminary Investigation of a Perchloroethylene (PCE) Groundwater P lume using a Passive Soil Gas Survey, 2008, REMEDIATION, Wiley Periodicals, Vol. 18, No. 4.

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Conclusions

• PSG Surveys Reduce Data Gaps and Overcome the Uncertainty Associated With Subsurface Spatial Variability

• PSG Surveys Collect Time-Integrated Samples over Several Days or Weeks and Overcome the Uncertainty Associated with Temporal Variability

• PSG Surveys Can Rapidly Characterize a Site for a Broad Range of Compounds (VOCs and SVOCs) with Minimal Disturbance to the Site

• Advanced PSG Surveys will Identify Source Areas, as well as Delineate the Contaminant Plume even at Low Concentrations

• When Strict QA/QC Procedures are Followed in the Field and in the Lab, the Resulting PSG Data will Best Reflect Subsurface Concentrations

• High-Quality PSG Data Sets Minimize the Required Number of Soil and/or Groundwater Samples

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ASTM D7758-11 – Approved Dec. 1, 2011

Standard Practice for Passive Soil Gas Sampling in the Vadose Zone for Source Identification, Spatial Variability Assessment, Monitoring, and Vapor Intrusion Evaluations.

Provides guidance on: • Sampler design • Sampling depth • Sampler exposure periods • Sampling procedures • Applications • Limitations • Field QC samples • Reporting • Data Usage

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Additional Resources

Brownfields Technology Primer: Vapor Intrusion Considerations for Redevelopment U.S. EPA Office of Solid Waste and Emergency Response, EPA Document No. 542-R-08-001, 2008.

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Additional Resources

Cal/EPA DTSC -- Guidance For The Evaluation And Mitigation Of Subsurface Vapor Intrusion To Indoor Air (Vapor Intrusion Guidance), October 2011 US EPA OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance) – Final Scheduled for Nov. 2012 Byrnes, M.E., Field Sampling Methods for Remedial Investigations, CRC Press, New York, 2009. New Jersey Department of Environmental Protection Field Sampling Procedures Manual, 2005.

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Any Questions?

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Thank You!

Please contact us if you have any questions:

Beacon Environmental Services, Inc. Harry O’Neill

President Bel Air, MD 21014 USA

1-410-838-8780 www.beacon-usa.com