ETC Soil & Groundwater Remediation 1 — Questions and Answers
Question 1: Which remediation technology uses a series of extraction wells to pump contaminated groundwater to the surface for treatment before reinjection or discharge?
- Air Sparging
- Pump-and-Treat (Correct answer)
- Permeable Reactive Barrier
- Monitored Natural Attenuation
Correct answer: Pump-and-Treat
Pump-and-treat is a common groundwater remediation method that extracts contaminated water, treats it above ground, and either reinjects or discharges the treated water.
Question 2: What is the primary goal of a Remedial Investigation/Feasibility Study (RI/FS) at a CERCLA Superfund site?
- To immediately remove contaminants from the site
- To characterize site contamination and evaluate cleanup alternatives (Correct answer)
- To issue fines to potentially responsible parties
- To install monitoring wells for long-term stewardship
Correct answer: To characterize site contamination and evaluate cleanup alternatives
The RI/FS process characterizes the nature and extent of contamination and evaluates remedial alternatives to support selection of a cleanup remedy.
Question 3: In soil vapor extraction (SVE), which contaminant property most directly governs how effectively the technology will remove the target compound?
- Water solubility
- Henry's Law constant (volatility) (Correct answer)
- Octanol-water partition coefficient (Kow)
- Soil organic carbon content
Correct answer: Henry's Law constant (volatility)
Henry's Law constant describes a compound's tendency to volatilize from soil/water into the vapor phase, making it the key parameter controlling SVE effectiveness.
Question 4: Which in-situ technology injects air below the water table to volatilize and biodegrade dissolved volatile organic compounds (VOCs) in groundwater?
- Bioventing
- Air Sparging (Correct answer)
- Soil Vapor Extraction
- Chemical Oxidation
Correct answer: Air Sparging
Air sparging injects air directly into saturated groundwater to volatilize VOCs and deliver oxygen to stimulate aerobic biodegradation of contaminants.
Question 5: A permeable reactive barrier (PRB) treats contaminated groundwater by allowing it to passively flow through reactive media. Which material is most commonly used to treat chlorinated solvents?
- Activated carbon
- Zero-valent iron (ZVI) (Correct answer)
- Potassium permanganate
- Hydrogen peroxide
Correct answer: Zero-valent iron (ZVI)
Zero-valent iron is the most widely used PRB fill material because it reductively dechlorinates chlorinated solvents like TCE and PCE through abiotic chemical reduction.
Question 6: What term describes the fraction of non-aqueous phase liquid (NAPL) that becomes physically trapped in soil pores and is essentially immobile?
- Free-phase NAPL
- Residual saturation (Correct answer)
- Dissolved plume
- Mobile LNAPL
Correct answer: Residual saturation
Residual saturation is the NAPL held by capillary forces in soil pore spaces that cannot move under natural gradients and serves as a long-term source of dissolved contamination.
ETC Soil & Groundwater Remediation 1
Which remediation technology uses a series of extraction wells to pump contaminated groundwater to the surface for treatment before reinjection or discharge?