Incremental Sampling Methodology (ISM) Part 1 - Introduction to ISM – Jeffrey E. Patterson Jeffrey E. Patterson – TCEQ, Technical Specialist, Superfund Section, Remediation Division – – – Member ITRC Committee on ISM Part 2 - ISM Field Implementation – Case Study – Ben Camacho – Daniel B. Stephens & Associates, Inc. – –

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

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

Volume to be Sampled (e.g. 1/8 th acre x 1 foot) 754,502,380 grams Decision WRONG Decision ? RIGHT Decision ? Sample 226 grams Field Sampling Sub-sample Lab sub-sampling 30 grams 300 ml Extract Lab Extraction Assay Volume 10 uls Extract Sub-sampling & Dilution Analysis Result Instrumental Analysis & Calculations “..the end point of an entire process..” A ratio of 25,000,000 to 1 4

Error associated with the sampling processes. Most importantly location of the sample!! Measurement True Value Measurement Error Sampling Error Error Error associated with laboratory preparation & analysis. 5

Total Error Sampling Error Dominates!!! 6 Errors associated as sum of squares (ME 2 + SE 2 = TE 2 ) Total Error Measurement Error Sampling Error

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

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. Three Sampling Approaches 8 Typical Grab Sampling What volume of soil does each sample represent? 100 Grab Samples How often do we get to do this? How much does this cost? 8

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

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

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

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

Heterogeneity Based on the location where the sample happens to be collected. Largest source of decision error faced by the environmental community. Many discrete samples – required to adequately address. Many discrete samples – routinely cost-prohibitive. 13

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

Sample # Total Cadmium (mg/kg) % Difference Site 1 Cadmium 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

Site 2 Chromium Duplicate Grab Samples 16 Sample # Total Chromium (mg/kg) % Difference

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

Site 4 Lead Concentrations in Grab Samples 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 ,500 4,600 1, ,900 5,500 1,100 2, ,400 1, inches inches 6-9 inches

This schematic shows concentrations in grab samples collected within a few feet of each other in three different residential yards. 4 feet Yard 1Yard 2Yard feet 7 feet 8 feet 15 feet Site 5 Arsenic Concentrations in Grab Samples from three Residential Yards (mg/kg) 19

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 ,400 41,200 33,000 22,400 37,500 45, ,170 1, feet 20 Site 6 TNT Concentrations in Grab Samples (mg/kg)

Site Grab samples in 10 x 10 meter grid

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 Original Grab = meter Grid 1Grid 20Grid 41 Grid 42 Grid 57Grid 85 Original Grab = 0.4Original Grab = 53 Original Grab = 21Original Grab = 3.3 Original Grab = 0.2

24 Grab Samples From Six Different Grids Original Grab = meter Grid 1Grid 20Grid 41 Grid 42 Grid 57Grid 85 Original Grab = 0.4Original Grab = 53 Original Grab = 21Original Grab = 3.3Original Grab = 0.2

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

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

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

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

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 x SF = C x CR x EF x ED BW x AT Sounds Like a Mean to Me! 29

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 concentrations of COCs present in the sampled medium.” 30

Remember! Heterogeneity – The largest source of decision error faced by the environmental community. Based on where we happen to sample! 31

Heterogeneity 2 32

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

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

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

Conclusion ISM = cost-effective method to: – Address contaminant heterogeneity, – Results are: more scientifically defensible, more reproducible, more representative. – Therefore – fewer decision errors. 36

ISM – Further Information Interstate Technology & Regulatory Council (ITRC) – 2015 Webinars Part 1 – May 7, November 3 Part 2 – May 14, November 10. (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