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Incremental Sampling Methodology (ISM)

Incremental Sampling Methodology (ISM). Part 1 - Introduction to ISM Jeffrey E. Patterson TCEQ, Technical Specialist, Superfund Section, Remediation Division j eff.patterson@tceq.texas.gov 512-239-2489 Member ITRC Committee on ISM Part 2 - ISM Field and Laboratory Implementation

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Incremental Sampling Methodology (ISM)

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  1. Incremental Sampling Methodology (ISM) • Part 1 - Introduction to ISM • Jeffrey E. Patterson • TCEQ, Technical Specialist, Superfund Section, Remediation Division • jeff.patterson@tceq.texas.gov • 512-239-2489 • Member ITRC Committee on ISM • Part 2 - ISM Field and Laboratory Implementation • Mark L. Bruce, Ph.D. • TestAmerica, Inc. • mark.bruce@testamericainc.com • 330-966-7267 • Member ITRC Committee on ISM 1

  2. Measurement - # the process of assigning a number to an attributeaccording to a set of rules. The measurement is not the same thing as the-thing-being-measured. Measurement True Value 2

  3. Quote from EPA Guidance “Data users often look at a concentration obtained from a laboratory as being “THE CONCENTRATION” in the soil, without realizing that the number generated by the laboratory is the end point of an entire process, extending from design of the sampling, through collecting, handling, processing, analysis, quality evaluation, and reporting”. (Soil Sampling Quality Assurance User’s Guide EPA/600/8-69/046) 3

  4. “..the end point of an entire process..” Volume to be Sampled (e.g. 1/8thacre x 1 foot) Extract Field Sampling Lab Extraction Sample 300 ml 226 grams Extract Sub-sampling & Dilution 754,502,380 grams Sub-sample Assay Volume 30 grams Lab sub-sampling RIGHT Decision 10 uls Instrumental Analysis & Calculations ? WRONG Decision ? Analysis Result Decision 4

  5. Error Measurement Measurement Error Sampling Error – error associated with the sampling processes, particularly with location of the sample. Measurement Error – error associated with laboratory preparation & analysis. Sampling Error True Value 5

  6. Total Error Sampling Error Dominates!!! Errors associated as sum of squares (ME2 + SE2 = TE2) Total Error Measurement Error Sampling Error 6

  7. SOILS = PARTICULATE MATTER • Natural soils are complex mixtures of: • different particle types, shapes, densities, and • Particle sizes • fine clays (4 µm diameter) to • coarse sand (2 mm in diameter). • 4 orders of magnitude. • COC particle sizes in soil • fine airborne particles (<1 µm diameter) • to relatively large pellets. 7

  8. Three Sampling Approaches Typical Grab Sampling 100 Grab Samples There are two types of grab sampling: Typically only a few discrete samples are collected from haphazardly selected locations – 3 grab samples are shown. In rare cases, many grab samples may be collected at regular intervals on a grid system – 100 samples are shown. How much does this cost? How often do we get to do this? What volume of soil does each sample represent? 8 8

  9. The Third Sampling Approach ISM Sampling The third sampling approach is ISM sampling, where up to 100 increments are collected, combined and processed as a single sample. One Sample Increment 9 9 9

  10. What is ISM? • Incremental Sampling Methodology (ISM) • A structured field sampling & • Laboratory processing & sub-sampling protocol. • Designed to address contaminant heterogeneity • By collection of many increments. 10

  11. What is ISM? 2 • Based in well-documented theory. • Well-demonstrated in practice. • Highly reproducible mean concentrations. • Increments collected in a specified volume of soil: • Called the “Decision Unit”. 11

  12. What is ISM? 3 • Based on recommendations of Pierre Gy’s Sampling Theory: • many increments (30-100 recommended); • each particle has an equal chance of being selected; • particle size reduction; and • large sample volume. • Result is an estimate of the mean concentration in the Decision Unit. 12

  13. Heterogeneity • Largest source of decision error faced by the environmental community. • Many discrete samples – required to adequately address • Many discrete samples – routinely cost-prohibitive. 13

  14. Heterogeneity Happens! Large volumes of soil in the field ≠ test-tube volumes. “Duplicate soil samples” do not produce duplicate results. Grab samples – huge variability over surprisingly small distances. 14

  15. Site 1Cadmium Duplicate Grab Samples • This table shows the percent difference between duplicate samples. The percent difference ranges between 1 and 161 percent. The five pairs of samples with the highest percent differences are highlighted with a box. 15

  16. Site 2Chromium Duplicate Grab Samples 16

  17. Site 3Lead Duplicate Grab Samples (mg/kg) This point graph shows percent difference between duplicate samples. The 17

  18. Site 4Lead Concentrations in Grab Samples3 inchesApart (mg/kg) This schematic shows concentrations of grab samples collected in seven borings at various depth intervals: 0-3 inches, 3 to 6 inches and 6 to 9 inches deep. 0-3 inches 13,500 500 1,900 51,900 1,100 400 19,400 3-6 inches 4,600 100 100 5,500 2,600 200 1,500 6-9 inches 400 3 inches apart! 18

  19. Site 5Arsenic Concentrations in Grab Samples from three Residential Yards (mg/kg) This schematic shows concentrations in grab samples collected within a few feet of each other in three different residential yards. Yard 1 Yard 2 Yard 3 8 feet 15 feet 37 290 625 94 27 29 45 34 29 24 79 120 17 41 367 351 268 129 221 61 39 14 6 feet 4 feet 7 feet Adapted From: Clu-In Incremental-Composite Webinar Module 1.2 19

  20. Site 6 TNT Concentrations in Grab Samples (mg/kg) 390 382 305 227 113 116 2 feet 1,170 1,200 37,500 45,000 33,000 22,400 44,400 41,200 This schematic shows the concentrations of seven duplicate grab sample pairs located within 2 feet of each other in a circular pattern. The 2 pairs with the highest differences are highlighted with a box. Adapted from: “Sampling Studies at an Air Force Live-Fire Bombing Range Impact Area, Cold Regions Research and Engineering Laboratory, US Army Corps of Engineers, February 2006. 20

  21. Site 7 100 Grab Samples in 10 meter x 10 meter grid (CRREL) TNT Concentration This three dimensional graph shows the concentrations of 100 grab samples collected on a 10 by 10 meter grid pattern. The highest concentration located next to non-detect samples is emphasized.Adapted from: “Sampling Studies at an Air Force Live-Fire Bombing Range Impact Area, Cold Regions Research and Engineering Laboratory, US Army Corps of Engineers, February 2006. 749 ppm Non Detect 21

  22. Site 7 (same as previous slide)1 x 1 meter squares • Resample six grids • 9 samples in each of six 1 x 1 meter squares 22

  23. Grab Samples From Six Different Grids Grid 1 Grid 20 Grid 41 1 meter Original Grab = 1.4 Original Grab = 0.4 Original Grab = 53 Grid 57 Grid 85 Grid 42 Adapted from: “Sampling Studies at an Air Force Live-Fire Bombing Range Impact Area, Cold Regions Research and Engineering Laboratory, US Army Corps of Engineers, February 2006. Original Grab = 21 Original Grab = 3.3 Original Grab = 0.2 23

  24. Grab Samples From Six Different Grids Grid 1 Grid 20 Grid 41 53 29 20 1.1 0.5 0.5 0.2 5.6 0.4 15 290 3.1 3.4 0.6 2.3 0.2 1.6 9.6 1 meter 1.7 5.7 55 0.3 0.5 0.2 4.4 0.7 0.6 Original Grab = 1.4 Original Grab = 0.4 Original Grab = 53 Grid 57 Grid 85 Grid 42 Adapted from: “Sampling Studies at an Air Force Live-Fire Bombing Range Impact Area, Cold Regions Research and Engineering Laboratory, US Army Corps of Engineers, February 2006. 0.1 0.2 2.1 8.8 22 22 1.3 0.6 2.6 0.4 0.2 64 2.8 2.3 2.6 12 2.4 15 2.1 0.2 402 22 42 2.0 0.6 0.6 9.9 Original Grab = 21 Original Grab = 3.3 Original Grab = 0.2 24

  25. The Mean Concentration • ISM produces an estimate of the mean concentration in the Decision Unit; • The mean is an integral part of the framework upon which all risk-based action levels (including TRRP PCLs) are based; • “the concentration term in the intake equation is an estimate of the arithmetic average concentration for a contaminant based on a set of site sampling results”. • (EPA: Supplemental Guidance to RAGS: Calculating the Concentration Term) 25

  26. The Mean Concentration 2 • The basis of most environmental decision criteria. • EPA Risk-based Soil Screening Levels • Groundwater Protection Levels • Background values • TRRP PCLs 26

  27. TRRP PCLs • Based on Risk Assessment equations • 3 assumptions: • 1) Chronic exposure (not acute); • 2) mean concentration over an area; and • 3) steady-state. • the receptor is exposed to a variety of concentrations • Best represented by the mean. 27

  28. The Risk Equation Existing Risk Existing Concentration Calculation Forward Direction Acceptable Risk TRRP PCL (Safe Concentration) Calculation Backward Direction 28

  29. The Risk Equation 2 Risk = I x SF = C x CR x EF x ED over BW x AT I = Intake SF = Slope Factor C = COC Concentration contacted over exposure period. CR = Contact Rate EF = Exposure Frequency ED = Exposure Duration AT = Averaging Time Risk = I xSF = C x CR x EF x ED BW x AT Sounds Like a Mean to Me! 29

  30. TRRP and ISM • Assessment requirements under TRRP are broad (§350.51): • “…in a manner most likely to detect the presence and distribution of COCs…” • “…sample collection techniques that meet the data quality needs and are acceptable to the executive director.” • “…collection and analysis of a sufficient number of samples…” • “…reliably characterize the nature and degree of COCs…” • “…collect and handle samples in accordance with sampling methodologies which will yield representative concentrationsof COCs present in the sampled medium.” 30

  31. Remember! • Heterogeneity – The largest source of decision error faced by the environmental community. 31

  32. Heterogeneity 2 32 Jackson Pollock

  33. ISM Implementation – The Bad News • More increments. • More field time per sample. • Larger sample volume. • Additional laboratory preparation. 33

  34. ISM Implementation – The Good News • Fewer sample supplies. • Less time for selecting sample locations. • Fewer locations to survey. • No decon between increments. • Less field documentation. • Fewer samples to ship, prepare & analyze! 34

  35. ISM Results – More Good News • More repeatable! • More accurate! • Better science! • Better decisions! 35

  36. Conclusion • ISM offers a cost-effective method to: • address contaminant heterogeneity, • provide more scientifically defensible, reproducible, and representative results, and • produce fewer decision errors. 36

  37. ISM – Further Information • Interstate Technology & Regulatory Council (ITRC) • 2014 Webinars • Part 1 – May 13, September 9, November 4 • Part 2 – May 15, September 16, November 6. • (also see archived webinars) • Cold Regions Research and Engineering Laboratory (CRREL) (USACE) • EPA Clu-in • Clu-In Incremental-Composite Webinar (also see archived webinars) • Method 8330B • Other Guidance Documents • US Army Corp of Engineers (USACE) • State of Alaska • State of Hawaii 37

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