K.P. Smith, R.L. Johnson, and J. Quinn Environmental Assessment Division

A U.S. Department of EnergyOffice of Science LaboratoryOperated by The University of ChicagoOffice of Science

U.S. Department of Energy

Streamlined Approaches to Characterizing NORM-Contaminated Sites Can Translate into Significant Cost Savings

K.P. Smith, R.L. Johnson, and J. Quinn

Environmental Assessment DivisionArgonne National Laboratory

Pioneering Science andTechnology

Office of Science U.S. Department

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Sampling Programs Are Key Components of All Environmental Restoration Processes

• Preliminary site assessment

• Extended site investigation

• Corrective action study

• Remedial action

• Closure

Multiple steps in a restoration project involve environmental sampling and analysis:

Traditional sampling and analysis programs are expensive and time-consuming.



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Adaptive Sampling and Analysis Programs (ASAP) Can Cut Costs Significantly

Approach•Real-time sample analysis•Rapid on-site decision making

Requirements•Field analytical method•Decision support on site

Advantages•Reduce cost/sample•Reduce # of samples•Reduce # of events•Better characterization•Allows in situ soil segregation

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ASAP Decision Support Has Three Distinct Phases

Assemble Baseline Information•Base maps•Geological information•Existing sampling data

Make Quantitative Decisions On Site•Extent of contamination•Where to stop•When to stop

Make Qualitative Decisions about Data Management•Data integration•Data visualization•Data dissemination



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Can ASAP Efficiencies Be Realized at a NORM Site?

Oil and gas production and processing activities can cause NORM to accumulate above natural background levels.

Radionuclides: Ra-226, Ra-228, and their decay products

Waste streams: produced water, scale, sludge, equipment, surface soils



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NORM Cleanup Requirements in the U.S.

Typical NORM cleanup criteria:

• Averaged over 100 m2

• Ranges from 5 to 30 pCi/g (0.185 to 1.1 Bq/g) Ra-226 or Ra-228 above background

• Sometimes two different limits based on radon emanation rate



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NORM Case Study: Michigan Site

• 1.4-hectare pipe handling facility

• NORM contamination in surficial soils: Ra-226 activity levels into the tens of thousands of pCi/g

• State guidelines require remediation to 5 pCi/g (0.185 Bq/g) averaged over 100 m2

• About 27 m3 of soil previously excavated and drummed based on gross activity screens



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The ASAP Approach Is Ideal for NORM-Contaminated Soils

Large number of field screening, direct measurement, and field analytical methods:

• Combined walkover/GPS systems for gross activity

• Stationary in situ NaI instruments

• Stationary in situ HPGe measurements

• Mobile laboratories with gamma spectroscopy capabilities



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Gamma Walkover Surveys Provide Inexpensive, Comprehensive, Qualitative Information

• Sodium Iodide (Na I) sensor measures total activity

• High detection efficiency, low energy resolution

• Collects data at 2 second intervals, generating hundreds to thousands of data points per acre

• Inexpensive: pennies per data point

• Combined with differential GPS systems to visualize walkover results



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Direct NaI Measurements Can Provide Estimates of Ra-226 Concentrations

• RadInSoilTM provides Ra-226 concentrations (pCi/g) for surface soils based on 5–10 min. readings

• Instrument needs to be calibrated to background at the site and assumes no other decay chain exists above background

• Per measurement costs on the order of $10–20 per data point

• Requires little training to operate



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In Situ HPGe Measurements Provide Accurate, Isotope-Specific Concentrations

• In situ High Purity Germanium (HPGe) gamma spectroscopy provides accurate, isotope-specific concentrations for surface soils

• Concentrations hold for the “field of view” of the instrument

• Costs are on the order of $100 per measurement

• Requires trained operator

• Low detection efficiency, high energy resolution



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Relationships between Gross Activity and Cleanup Criteria Are Key

• Decisions are binary — either cleanup soil or leave behind

• Want to identify “trigger” levels that can be used to carve up the site based on gross activity information

• Makes use of nonparametric approach with no assumptions about linear correlation

• Use paired information to do the analysis 0

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ASAP Process for Michigan SiteStep 1: Complete Gamma Walkover Step 2: Develop Relationship between

Gamma Walkover Data and Cleanup Criteria

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• Paired gross activity to RadInSoil measurements collected at 49 sites

• Established trigger levels for 5-pCi/g cleanup criterion: 1,800–2,500 cpm



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ASAP Process for Michigan Site

• Three areas: likely clean, likely contaminated, and uncertain based on available data

Step 3: Divide Site on Basis of Trigger Levels

• Average data over 100 m2 using moving window averages on gamma walkover data



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ASAP Process for Michigan Site

Step 4: Remediate and Rewalk

• Verification of “uncertain” areas with in situ HPGe

• Selective removal of “hot” spots across site

• Rewalk with gamma walkover surveys and reshoot with HPGe to confirm clean

Note: The site was not cleaned up to background but was brought into compliance with state guidelines: 5 pCi/g Ra-226 averaged over 100 m2.



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The Michigan Case Had Positive Results

• Excellent agreement between off-site confirmatory sample results and on-site analytics

• Reduced disposal costs possibly as much as $36,000 less

• Significant analytical cost savings about a 90% savings using in situ analytical capabilities

• Compressed time line because remediation was integrated with characterization



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For more information:Final report available from:• Download in PDF format from

“www.ead.anl.gov”More information available from:• Bob Johnson

[email protected]

• Karen P. [email protected], ext. 267

Consistent with Triad approach being recommended by the USEPA: www.triadcentral.org

Documents

K.P. Smith, R.L. Johnson, and J. Quinn Environmental Assessment Division