ITRC ISM Team (90 members)

Transcription

1 Incremental Sampling Methodology (ISM) Florida Brownfields Conference Ligia Mora-Applegate Florida DEP Nov. 15, 2010 ITRC ISM Team (90 members) Academic 3% State Regulators 30% DOD 34% Stakeholders 1% Academic DOD DOE EPA Priv ate Stakeholders State Regulators DOE 3% EPA 9% Private 21% 1

2 Discussion Topics Applicability ISM Overview Systematic planning Conceptual Site Model (CSM) Data Quality Objectives (DQOs) Decision Units (DUs) FieldSamplingandPocessing and Processing Laboratory Processing and Analysis Challenges/Limitations Tech-Reg Document (web-based) General Application Media ISM Team focus on soils Type of Contaminants Metals Semi-Volatiles Volatiles Eplosives Sites 4 2

3 Sampling Overview Limited number of discrete samples Sampling variability >> Analytical variability Quality control and reproducibility are lacking Scientifically defensible Q: How can we get representative and defensible data that meet DQO s, including use in a risk assessment, and reduce overall analytical costs? 5 ISM- A Structured Composite Sampling Protocol ISM is a sampling methodology used to obtain a representative sample having analytes in eactly the same proportions as the entire decision unit 6 3

4 Protocol Components of ISM Systematic Planning Determining the Decision Unit (DU) Field Sample Collection Systematic random collection of increments per DU Laboratory Processing and Analysis Particle size selection (dry, sieve, grind), sub-sample, analysis Data Evaluation 7 Conceptual Site Model of Environmental Hazards Ecotoicity Direct Eposure Leaching Leaching Stream Stream Vapor Intrusion Gross Contamination Groundwater Flow Free Product Discharge to aquatic habitats Dissolved plume Drinking Water 8 4

5 Decision Units (DU) An area (volume) where samples are to be collected and a decision made Decision Risk based decision Need for remediation Background levels Comparison to screening level(s) 9 Does Your Sample Represent the Decision Unit Discrete Sampling Incremental Sampling Collection point for 100 discrete samples Typically only a few discrete samples are collected Path of travel Increment collection point for 3 to 5 separate IS 10 5

6 DU Types Release/Source Area DUs (e.g., drums, waste pits, soil around primary sources, etc.) Focus on investigation of obvious or suspected contaminated areas Identify contaminants of potential concern Flag potential environmental problems that warrant additional attention Eposure Area DUs (e.g., eposed soil in yard) Focus on risk to humans (or ecological health) Used in traditional human health risk assessments 11 Surface Decision Units (DUs) An area (volume) where samples are to be collected and decisions made based on the resulting data. Variability within the DU needs to be captured in data but not specifically determined? Source Areas Eposure Areas 6

7 Investigate Obvious Source Areas Separately waste oil pit Release Area DU (after draining pit) 13 Source Area DU Transformer Pad (Representative concentration of PCBs in DU soil?) Coverage of DU based on three discrete samples Will these samples give a reliable estimate of PCB concentrations in DU soil. 14 7

8 Source Area DU Transformer Pad (Representative concentration of PCBs in DU soil?) Coverage of DU based on one incremental sample Is this a better estimate of representative PCB concentration in DU soil. 15 Eposure Area DUs What s the representative Eposure Area ("point") concentration in my...? Neighborhood Park Utility Trench Yard Sandbo? Home Range Size & shape of decision unit depends on the targeted receptor and the desired resolution of the evaluation. 16 8

9 Discrete Samples Collect a few discrete samples Statistically estimate EPC (e.g., 95% UCL) Decisions usually based on "maimum" reported Poor spatial coverage, high lab cost 9

10 Incremental Sample Collect 1-3 incremental samples per DU Include 30 to 50 increments of soil per sample More likely to incorporate small "hot spots" in estimation of eposure area concentrations Collect 3 replicate samples (triplicates) per DU if 95% UCL needed Collect an increment of soil at each point (e.g., grams) 20 10

11 Collect Core Samples From Target Layers Core Increments Total 30 Borings 0m -2m -4m -6m DU-1 DU-2 DU-3 DU-4-8m Individual core samples combined to prepare an IS sample for each DU and/or for each core (e.g. to identify areas of high contamination). Ecavation Decision Units Floor and sides tested as separate decision units DU-5 DU-3 DU-1 11

12 Increment Core (IC) Sample Preservation in Methanol (1:1 Soil:MeOH Ratio) Traditional 5-gram VOC sample Planned 50- to 150- gram VOC sample Laboratory Analysis Alternate analytical technique, e.g. SIM, may be required for reporting 23 limits to meet DQOs photos courtesy of Hewitt, Ramsey & Bigl; ACE Sieve each incremental sample to <2mm (can be done in lab) 24 12

13 Collect increments from sieved sample as final sample sent to lab (reduces sample volume) 25 Laboratory Subsampling Air dry Sieve Sometimes grind Subsample for each analysis (30-50 increments) Analyze at least 10 gram mass to minimize fundamental error Maintain quality of field sample in lab analysis 26 13

14 Challenges Regulatory, Process & Mis-Perceptions Some policies or regulations may specify the need for a maimum and/or mean or a 95% UCL of the mean to evaluate: Human Health Environmental Ecological Groundwater protection 27 Barriers Regulatory, Process & Mis-Perceptions Incremental vs. composite Dilution of sample Shortage of ISM eperienced laboratories Doesn t work for volatiles Will not see hotspots Not full characterization spatial resolution Determine what is significant eposure unit and what is threshold concentration up front 28 14

15 ITRC ISM Web-Based Tech-Reg Document Provide technically sound guidance to design ISM approaches for improved soil and sediment data quality Aid in developing consistent and technically sound ISM policies Point out pitfalls to avoid in designing sampling strategies Address misperceptions about: Composite sampling Lack of characterization Minimizing hot spots 29 ITRC ISM Web-Based Tech-Reg Document Overview Systematic Planning CSM/DUs Sampling Theory ISM/Discrete/Composite issues Theory/Statistical simulations/sampling design Case studies Field Implementation Laboratory Processing and Analysis Regulatory/Stakeholder Implementation Concerns Conclusions/Recommendations References Schedule Eternal Review February 2011 Final November 2011 Training in