Presentation is loading. Please wait.

Presentation is loading. Please wait.

Lessons Learned Multi Incremental Sampling Alaska Forum on the Environment February, 2009 Alaska Department of Environmental Conservation.

Similar presentations


Presentation on theme: "Lessons Learned Multi Incremental Sampling Alaska Forum on the Environment February, 2009 Alaska Department of Environmental Conservation."— Presentation transcript:

1 Lessons Learned Multi Incremental Sampling Alaska Forum on the Environment February, 2009 Alaska Department of Environmental Conservation

2 Sampling Theory Review Heterogeneity – The Rule Heterogeneity – The Rule Impossible to sample the entire population Impossible to sample the entire population Statistical methods must be used to determine a representative mean Statistical methods must be used to determine a representative mean Goal is to minimize sampling error Goal is to minimize sampling error

3 Sampling Error Compositional Heterogeneity Compositional Heterogeneity Contributes to fundamental error (FE) - result of not representing proportional concentrations of all of the particles in the population. Contributes to fundamental error (FE) - result of not representing proportional concentrations of all of the particles in the population. Distributional Heterogeneity Distributional Heterogeneity Contributes to grouping and segregation error (GSE) – result of not collecting enough random increments in enough locations to capture spatial variability. Contributes to grouping and segregation error (GSE) – result of not collecting enough random increments in enough locations to capture spatial variability.

4 To minimize fundamental error… collect enough mass.

5 To minimize grouping and segregation error… collect from many random locations.

6 Fundamental Error Equation Where FE = Sampling fundamental error 20 = Sampling constant d = maximum particle size (centimeters) m = sample mass (grams)

7 Goal Maintain FE at 15% or less Maintain FE at 15% or less At least 30 g of sample analyzed At least 30 g of sample analyzed 2 mm soil fraction 2 mm soil fraction Grinding required for smaller sample size Grinding required for smaller sample size

8 Composite or MI? MI uses a defined decision unit MI uses a defined decision unitBUT Composite sampling does not consider the decision unit Composite sampling does not consider the decision unit MI attempts to control FE and GSE MI attempts to control FE and GSEBUT Compositing is a simple combination of discrete samples and does not control FE or GSE Compositing is a simple combination of discrete samples and does not control FE or GSE

9 Decision Unit Identification The area or volume in question The area or volume in question (i.e. contaminated zone) Systematic planning - Thorough documentation when setting decision unit boundaries Systematic planning - Thorough documentation when setting decision unit boundaries Potential “dilution” effect and hot spot removal must be considered Potential “dilution” effect and hot spot removal must be considered Decision units must be approved by DEC Decision units must be approved by DEC

10 Sampling Locations Increments collected from multiple random locations Increments collected from multiple random locations Different types of random sampling techniques Different types of random sampling techniques Systematic random preferred Systematic random preferred Sample depth considerations Sample depth considerations Sampling from the excavator bucket Sampling from the excavator bucket

11 Current Procedure – Non-Volatiles Lab must meet MI-specific requirements Lab must meet MI-specific requirements Scoop at least g into appropriate container from each random increment location Scoop at least g into appropriate container from each random increment location Sieve now or bag and sieve later Sieve now or bag and sieve later Sub-sample in field or lab Sub-sample in field or lab Approx. 500 – 1,000 g should be available after sieving Approx. 500 – 1,000 g should be available after sieving Spread evenly and divide into sections (~30) Spread evenly and divide into sections (~30) One small scoop (about 1-2 g) from each section into a 2-4 oz sample jar One small scoop (about 1-2 g) from each section into a 2-4 oz sample jar

12 Current Procedure - Volatiles Volatile sample containers Volatile sample containers Small spoon, spatula Small spoon, spatula No sieving No sieving Sample increments deposited into methanol at a minimum 1:1 ratio Sample increments deposited into methanol at a minimum 1:1 ratio Remove large clumps or rocks Remove large clumps or rocks 2-5 g from each increment location 2-5 g from each increment location

13 QA/QC Triplicates collected to determine Relative Standard Deviation (RSD) Triplicates collected to determine Relative Standard Deviation (RSD) Multiple, similar decision units may have a reduced triplicate sampling frequency Multiple, similar decision units may have a reduced triplicate sampling frequency Do not collect triplicates from co-located or adjacent locations Do not collect triplicates from co-located or adjacent locations

14 RSD is a measure of data precision expressed in percent RSD is a measure of data precision expressed in percent Indication of representativeness of MI sampling of decision unit Indication of representativeness of MI sampling of decision unit 30% or less required 30% or less required At RSDs >35%, the data distribution starts to become non-normal and the confidence in the representativeness on the MI sample results diminishes. At RSDs >35%, the data distribution starts to become non-normal and the confidence in the representativeness on the MI sample results diminishes.

15 95% UCL 95 % UCL must be calculated for all decision units 95 % UCL must be calculated for all decision units Only the 95% UCL will be used to evaluate the decision units Only the 95% UCL will be used to evaluate the decision units

16 MI Sampling Projects Review ADEC Developed Draft Guidance in March 2007 ADEC Developed Draft Guidance in March 2007 Approximately 40 projects have been proposed using MI sampling since then with approximately 20 projects accomplished using MI sampling Approximately 40 projects have been proposed using MI sampling since then with approximately 20 projects accomplished using MI sampling ADEC plans on updating the guidance in the near future ADEC plans on updating the guidance in the near future

17 Lessons Learned Sample Drying Sample Drying Sample grinding Sample grinding SW 846 SW 846 VOCs VOCs Decision Units Decision Units Sieving Sieving Risk Assessment and ITRC Risk Assessment and ITRC

18 Sample Drying Sieving wet samples can be difficult and might leave material behind Sieving wet samples can be difficult and might leave material behind Based on limited information, drying samples for semi-volatile and non-volatile analyses has not shown a significant decrease in contaminant concentrations (e.g. weathered DRO) Based on limited information, drying samples for semi-volatile and non-volatile analyses has not shown a significant decrease in contaminant concentrations (e.g. weathered DRO) Contact ADEC if sample drying will affect holding times Contact ADEC if sample drying will affect holding times

19 Sample Grinding Grinding may be required for samples to be analyzed for metals or any other analytes where the analytical sample size is small Grinding may be required for samples to be analyzed for metals or any other analytes where the analytical sample size is small Some out of state labs are offering grinding and MI prep Some out of state labs are offering grinding and MI prep Likely to become more common as more MI samples are collected Likely to become more common as more MI samples are collected

20 SW 846- General Test Methods EPA Method 8330B- Explosives EPA Method 8330B- Explosives “Various studies have shown that concentrations of energetic residues at military training ranges that were measured using the procedures in 8330B (MI Sampling) were statistically more representative relative to traditional sampling and analytical protocols” 1 (MI Sampling) were statistically more representative relative to traditional sampling and analytical protocols” 1

21 VOC’s Using a spoon or spatula with wide mouth jar results in loss of volatiles Using a spoon or spatula with wide mouth jar results in loss of volatiles Updated guidance will recommend using an Encore TM Sampler or other similar coring device that will reduce the loss of volatiles and a narrow mouth jar Updated guidance will recommend using an Encore TM Sampler or other similar coring device that will reduce the loss of volatiles and a narrow mouth jar

22

23 Decision Units Should include only the release area, if known Should include only the release area, if known Alternative decision units may be proposed, if impacted area is not known or has been reworked Alternative decision units may be proposed, if impacted area is not known or has been reworked Decision units must be clearly identified in a work plan and must be approved by ADEC Decision units must be clearly identified in a work plan and must be approved by ADEC

24 Sieving Highly organic soil types such as peat are not conducive to sieving, therefore, MI sampling is not appropriate without alternate sample collection and preparation procedures Highly organic soil types such as peat are not conducive to sieving, therefore, MI sampling is not appropriate without alternate sample collection and preparation procedures Contact ADEC for additional information on MI sampling for this matrix Contact ADEC for additional information on MI sampling for this matrix

25 Risk Assessment EPA Region X Risk Assessment Conference in 2008 included a presentation on MI sampling EPA Region X Risk Assessment Conference in 2008 included a presentation on MI sampling MI sampling may be accepted for use in Risk Assessments in the future MI sampling may be accepted for use in Risk Assessments in the future Contact ADEC to discuss how this might impact your Risk Assessment Contact ADEC to discuss how this might impact your Risk Assessment

26 ITRC Workgroup Will begin working on a guidance document for MI sampling in 2009 Will begin working on a guidance document for MI sampling in 2009

27 For Best Results, Use MI Sampling… To find the mean concentration of a contaminant in surface soil that is conducive to MI sample preparation and analysis To find the mean concentration of a contaminant in surface soil that is conducive to MI sample preparation and analysis Where the decision unit is easily identified Where the decision unit is easily identified When you’ve considered the potential outcome and are comfortable with it. When you’ve considered the potential outcome and are comfortable with it.

28 Consider another sampling method when… Soil type is not conducive to MI sample preparation and analyses Soil type is not conducive to MI sample preparation and analyses Identifying hot spots Identifying hot spots Delineating the extent of contamination Delineating the extent of contamination Determining the maximum concentration Determining the maximum concentration

29 Questions and Discussion

30 References 1- DoD Environmental Data Quality Workgroup, Guide for Implementing EPA SW-846 Method 8330B July 7, DoD Environmental Data Quality Workgroup, Guide for Implementing EPA SW-846 Method 8330B July 7, 2008.


Download ppt "Lessons Learned Multi Incremental Sampling Alaska Forum on the Environment February, 2009 Alaska Department of Environmental Conservation."

Similar presentations


Ads by Google