CEA Environmental Assessment & Sampling Techniques 4 — Questions and Answers
Question 1: During low-flow groundwater sampling, which stabilization criteria must be met before collecting a sample?
- pH ±0.5, specific conductance ±5%, DO ±10%, ORP ±10 mV across three readings (Correct answer)
- pH ±1.0, turbidity <10 NTU, and temperature ±2°C
- Dissolved oxygen at saturation and turbidity <1 NTU
- Three well volumes purged and water level recovery to within 80% of static
Correct answer: pH ±0.5, specific conductance ±5%, DO ±10%, ORP ±10 mV across three readings
Low-flow sampling requires stabilization of field parameters (pH ±0.5 units, SC ±5%, DO ±10%, ORP ±10 mV) across three consecutive readings before sample collection.
Question 2: Which type of environmental sampling error occurs when the sample collected does not represent the true population due to a flaw in sampling design?
- Analytical error from laboratory instrument drift
- Sampling bias from non-representative location selection (Correct answer)
- Preservation error from improper container preparation
- Transcription error in field logbook documentation
Correct answer: Sampling bias from non-representative location selection
Sampling bias occurs when the sampling design systematically favors certain portions of the population, resulting in samples that do not accurately represent site conditions.
Question 3: A site investigation requires characterizing contamination at depths ranging from 15 to 60 feet below ground surface in unconsolidated sediments. Which direct push technology is most commonly used?
- Hollow-stem auger drilling with split-spoon sampling
- Cone Penetrometer Testing (CPT) with chemical sensors (Correct answer)
- Rotary air blast (RAB) drilling
- Hand augering with Shelby tube sampling
Correct answer: Cone Penetrometer Testing (CPT) with chemical sensors
Cone Penetrometer Testing (CPT) with chemical sensors provides continuous subsurface profiling for contaminant characterization at depth in unconsolidated sediments without generating significant cuttings waste.
Question 4: When assessing indoor air quality for vapor intrusion from groundwater contamination, which approach provides the most site-specific exposure assessment?
- Using EPA's generic attenuation factor of 0.001 without sub-slab data
- Collecting simultaneous sub-slab soil gas and indoor air samples (Correct answer)
- Reviewing only the historical groundwater analytical data
- Applying the Johnson & Ettinger model without field verification
Correct answer: Collecting simultaneous sub-slab soil gas and indoor air samples
Simultaneous sub-slab soil gas and indoor air sampling provides the most defensible site-specific vapor intrusion assessment by measuring actual conditions rather than relying on default model assumptions.
Question 5: A Phase I ESA report identifies a prior underground storage tank (UST) that was removed in 1989 with no closure documentation. How should this be classified?
- De minimis condition requiring no further action
- Controlled Recognized Environmental Condition (CREC)
- Recognized Environmental Condition (REC) warranting Phase II investigation (Correct answer)
- Historical Recognized Environmental Condition (HREC) with no further concern
Correct answer: Recognized Environmental Condition (REC) warranting Phase II investigation
A UST removal without documented closure confirmation or soil/groundwater sampling represents a REC because there is no evidence the removal was completed without a release.
Question 6: Which EPA method is the standard for determining volatile organic compounds (VOCs) in groundwater samples submitted to a laboratory?
- EPA Method 8270D (semivolatile organics by GC/MS)
- EPA Method 8260C (VOCs by purge-and-trap GC/MS) (Correct answer)
- EPA Method 6010C (metals by ICP-OES)
- EPA Method 9040C (pH electrometric method)
Correct answer: EPA Method 8260C (VOCs by purge-and-trap GC/MS)
EPA Method 8260C uses purge-and-trap concentration followed by GC/MS analysis and is the standard method for determining volatile organic compounds in aqueous and solid samples.
Question 7: During a Preliminary Assessment under CERCLA, what is the primary source of information used to evaluate potential releases?
- Extensive field sampling of soil and groundwater
- Existing records, databases, and file reviews without field sampling (Correct answer)
- Installation of groundwater monitoring wells
- Collection of surface water samples from nearby streams
Correct answer: Existing records, databases, and file reviews without field sampling
A CERCLA Preliminary Assessment is a records review that uses existing information including federal and state databases, historical records, and file reviews to identify potential releases without field sampling.
CEA Environmental Assessment & Sampling Techniques 4
During low-flow groundwater sampling, which stabilization criteria must be met before collecting a sample?