CHMM Site Remediation 2 — Questions and Answers
Question 1: Which remediation technology uses microorganisms to degrade petroleum hydrocarbons in situ by injecting oxygen or nutrients into the subsurface?
- Air sparging
- Enhanced bioremediation (Correct answer)
- Thermal desorption
- Soil vapor extraction
Correct answer: Enhanced bioremediation
Enhanced bioremediation stimulates naturally occurring microorganisms by supplying oxygen, nutrients, or electron donors to accelerate biodegradation of contaminants in situ.
Question 2: Under CERCLA, the National Contingency Plan (NCP) requires that remedies selected for Superfund sites meet what primary standard?
- Cost-effectiveness only
- Applicable or relevant and appropriate requirements (ARARs) (Correct answer)
- State permit compliance only
- Best available technology (BAT)
Correct answer: Applicable or relevant and appropriate requirements (ARARs)
NCP requires that Superfund remedies attain ARARs, which are federal and state environmental standards relevant to the site conditions.
Question 3: A site has chlorinated solvent DNAPL contamination. Which technology directly targets the dense non-aqueous phase liquid source zone most effectively?
- Pump and treat with activated carbon
- In situ chemical oxidation (ISCO) (Correct answer)
- Monitored natural attenuation
- Air sparging alone
Correct answer: In situ chemical oxidation (ISCO)
ISCO delivers oxidants such as permanganate, persulfate, or hydrogen peroxide directly into the source zone to chemically destroy DNAPL-phase contaminants.
Question 4: What term describes the process of documenting that a remediated site has achieved cleanup goals and no further action is required?
- Feasibility study
- Remedial investigation
- Site closure (Correct answer)
- Preliminary assessment
Correct answer: Site closure
Site closure is the formal regulatory process confirming cleanup objectives have been met, often resulting in a no-further-action (NFA) letter.
Question 5: During a pump-and-treat operation, 'asymptotic tailing' refers to which phenomenon?
- Rapid contaminant removal in the early phase
- Concentrations declining quickly to non-detect levels
- Contaminant concentrations leveling off at low but persistent levels (Correct answer)
- Groundwater mounding beneath the extraction wells
Correct answer: Contaminant concentrations leveling off at low but persistent levels
Asymptotic tailing occurs when dissolved contaminant concentrations drop steeply at first but then flatten at persistently low levels due to back-diffusion or NAPL dissolution.
Question 6: Which vapor intrusion mitigation system depressurizes the sub-slab zone to prevent soil vapors from entering a building?
- Positive-pressure ventilation
- Sub-slab depressurization (SSD) (Correct answer)
- Heat recovery ventilation
- Carbon filter air scrubber
Correct answer: Sub-slab depressurization (SSD)
SSD installs suction pipes through the floor slab to maintain negative pressure beneath the building, diverting vapors away from interior spaces.
Question 7: When excavating contaminated soil near a property boundary, which engineering control is most commonly used to prevent dust migration offsite?
- Groundwater extraction
- Wind breaks and water misting systems (Correct answer)
- Soil vapor extraction
- Permeable reactive barriers
Correct answer: Wind breaks and water misting systems
Water misting and wind breaks suppress fugitive dust during excavation operations, protecting neighboring receptors and complying with air quality requirements.
CHMM Site Remediation 2
Which remediation technology uses microorganisms to degrade petroleum hydrocarbons in situ by injecting oxygen or nutrients into the subsurface?