ETC Soil & Groundwater Remediation 2

Question 1

What is the difference between LNAPL and DNAPL in groundwater contamination scenarios?

Accepted Answer

LNAPL floats on the water table; DNAPL sinks below it

Answer

Light Non-Aqueous Phase Liquids (LNAPLs) have densities less than water and float on the water table, while Dense Non-Aqueous Phase Liquids (DNAPLs) are denser than water and sink below it.

Question 2

In groundwater monitoring, what is the purpose of a 'sentinel well' placed downgradient of a remediation system?

Accepted Answer

To detect contaminant migration beyond the treatment zone

Answer

Sentinel wells serve as early warning indicators to detect whether contamination is migrating past the capture zone of a pump-and-treat or containment system.

Question 3

Which EPA guidance document provides the framework for evaluating risk at contaminated sites to establish cleanup levels protective of human health?

Accepted Answer

EPA Risk Assessment Guidance for Superfund (RAGS)

Answer

EPA's Risk Assessment Guidance for Superfund (RAGS) provides the standard framework for conducting baseline human health risk assessments that determine remediation goals at contaminated sites.

Question 4

Enhanced bioremediation of chlorinated solvents often involves injecting an electron donor such as vegetable oil or molasses. What process does this stimulate?

Accepted Answer

Anaerobic reductive dechlorination

Answer

Electron donor injection creates anaerobic conditions that stimulate reductive dechlorination, in which microorganisms sequentially remove chlorine atoms from compounds like PCE and TCE.

Question 5

What does the term 'plume diving' describe in a groundwater contamination scenario?

Accepted Answer

Contaminant sinking into deeper aquifer units due to density or recharge

Answer

Plume diving occurs when a dissolved contaminant plume is driven downward into deeper aquifer zones due to recharge events, density differences, or aquifer heterogeneity.

ETC - Environmental Technician Certification Practice Test

ETC - Environmental Technician Certification Practice Test

ETC Soil & Groundwater Remediation 2