CEA Soil Contamination Assessment 2 — Questions and Answers
Question 1: Which EPA method is most commonly used for the extraction of semivolatile organic compounds (SVOCs) from soil samples?
- EPA Method 8270
- EPA Method 3510C
- EPA Method 8015
- EPA Method 3550C (Correct answer)
Correct answer: EPA Method 3550C
EPA Method 3550C (Ultrasonic Extraction) is the standard extraction method for SVOCs from soil prior to analysis by methods like 8270.
Question 2: A Phase II ESA soil boring reveals petroleum hydrocarbons at 500 mg/kg at 5 feet bgs. The site is in a residential zone. What is the immediate next step?
- Close the boring and file a no-further-action letter
- Compare results to applicable state residential soil cleanup standards (Correct answer)
- Install a groundwater monitoring well immediately
- Submit a RCRA Part B permit application
Correct answer: Compare results to applicable state residential soil cleanup standards
Detected concentrations must be compared to applicable state residential cleanup standards to determine if further action is required.
Question 3: Which parameter best describes the tendency of a contaminant to volatilize from soil into the overlying air?
- Octanol-water partition coefficient (Kow)
- Henry's Law constant (H) (Correct answer)
- Soil-water partition coefficient (Kd)
- Organic carbon partition coefficient (Koc)
Correct answer: Henry's Law constant (H)
Henry's Law constant describes the equilibrium partitioning of a compound between the aqueous phase and vapor phase, indicating volatilization potential.
Question 4: What is the purpose of a 'soil background concentration' study during a contamination assessment?
- To establish baseline levels of naturally occurring substances for comparison with site data (Correct answer)
- To calculate the total mass of contaminants in the vadose zone
- To determine the soil cation exchange capacity
- To identify the depth to groundwater
Correct answer: To establish baseline levels of naturally occurring substances for comparison with site data
Background concentration studies establish naturally occurring or ambient levels of substances so that site-related contamination can be distinguished from natural conditions.
Question 5: Soil vapor intrusion risk is GREATEST under which site condition?
- Low soil moisture with a clay cap over contamination
- Shallow groundwater contaminated with chlorinated VOCs beneath a building (Correct answer)
- Deep bedrock contamination with no overlying structures
- Surface spill of non-volatile heavy metals near a parking lot
Correct answer: Shallow groundwater contaminated with chlorinated VOCs beneath a building
Shallow groundwater contaminated with chlorinated VOCs directly beneath a building maximizes the vapor intrusion pathway to indoor air.
Question 6: Which soil property most strongly controls the adsorption of non-polar organic contaminants?
- pH
- Cation exchange capacity (CEC)
- Total organic carbon (TOC) content (Correct answer)
- Particle size distribution
Correct answer: Total organic carbon (TOC) content
Total organic carbon content is the primary soil property controlling adsorption of non-polar organic compounds, as described by the Koc relationship.
Question 7: In a human health risk assessment for soil contamination, the 'exposure frequency' variable for a residential receptor is typically assumed to be:
- 52 days per year
- 125 days per year
- 250 days per year
- 350 days per year (Correct answer)
Correct answer: 350 days per year
EPA default exposure frequency for a residential receptor is 350 days per year, reflecting nearly continuous occupancy at a home.
CEA Soil Contamination Assessment 2
Which EPA method is most commonly used for the extraction of semivolatile organic compounds (SVOCs) from soil samples?