CHMM Site Remediation 3 — Questions and Answers
Question 1: A permeable reactive barrier (PRB) using zero-valent iron (ZVI) remediates chlorinated solvents primarily through which mechanism?
- Adsorption onto activated carbon
- Reductive dechlorination via electron donation from iron (Correct answer)
- Oxidation by permanganate
- Volatilization to atmosphere
Correct answer: Reductive dechlorination via electron donation from iron
ZVI donates electrons to chlorinated compounds, causing reductive dechlorination that breaks chlorine-carbon bonds and produces less-toxic or non-toxic daughter products.
Question 2: In a remedial investigation, what is the primary purpose of installing groundwater monitoring wells in a transect downgradient of the source area?
- To inject remediation reagents
- To delineate the contaminant plume extent and direction (Correct answer)
- To measure soil gas concentrations
- To collect surface water samples
Correct answer: To delineate the contaminant plume extent and direction
Downgradient transect wells define the lateral and vertical extent of the dissolved-phase plume, confirming contaminant migration pathways.
Question 3: Which RCRA corrective action document establishes the final cleanup standards and schedule for a facility subject to a corrective action order?
- Preliminary assessment report
- Corrective measures implementation (CMI) plan (Correct answer)
- Site investigation report
- RCRA facility assessment (RFA)
Correct answer: Corrective measures implementation (CMI) plan
The CMI plan details the selected corrective measures, implementation schedule, and performance standards that a RCRA facility must achieve.
Question 4: Thermal in situ remediation techniques such as electrical resistance heating (ERH) are most advantageous for which contaminant class?
- Heavy metals in surface soil
- Chlorinated solvents with low vapor pressure in low-permeability soils (Correct answer)
- Dissolved nitrate in shallow aquifers
- Radioactive isotopes in bedrock
Correct answer: Chlorinated solvents with low vapor pressure in low-permeability soils
ERH heats the subsurface to increase volatility of chlorinated solvents, enabling vapor extraction even from tight, low-permeability formations where other methods fail.
Question 5: Risk-based corrective action (RBCA) frameworks allow remediation to a site-specific risk level rather than a generic standard. What primary factor drives site-specific cleanup levels?
- The cost of the most expensive technology
- Exposure pathways, receptor populations, and contaminant toxicity (Correct answer)
- The age of the contamination
- The depth of the water table
Correct answer: Exposure pathways, receptor populations, and contaminant toxicity
RBCA tier calculations incorporate contaminant toxicity, site-specific exposure pathways, and sensitive receptors to derive protective cleanup levels tailored to actual risk.
Question 6: Which document formally records the deed restriction or land use control (LUC) placed on a remediated property to limit future land use?
- Environmental covenant or deed restriction (Correct answer)
- Remedial action plan
- Notice of violation
- Brownfields assessment report
Correct answer: Environmental covenant or deed restriction
An environmental covenant or deed restriction is recorded with the property deed to legally restrict land use and protect the integrity of the remedy.
Question 7: Monitored natural attenuation (MNA) relies on which natural processes to reduce contaminant concentrations without active intervention?
- Excavation and disposal
- Biodegradation, dispersion, dilution, sorption, and volatilization (Correct answer)
- Chemical oxidation by injected reagents
- Thermal destruction
Correct answer: Biodegradation, dispersion, dilution, sorption, and volatilization
MNA harnesses naturally occurring physical, chemical, and biological processes to reduce contaminant mass, toxicity, mobility, or concentration over time.
CHMM Site Remediation 3
A permeable reactive barrier (PRB) using zero-valent iron (ZVI) remediates chlorinated solvents primarily through which mechanism?