CES Groundwater & Hydrogeology 3

Question 1

The vadose zone (unsaturated zone) is characterized by pore spaces that contain:

Accepted Answer

Both air and water at pressures less than atmospheric

Answer

Only water under artesian pressure

Answer

No water — all voids are filled with soil gas

Answer

Water fully saturating all pore spaces at atmospheric pressure

Question 2

A slug test is used in field hydrogeology to:

Accepted Answer

Estimate hydraulic conductivity of the aquifer immediately surrounding a single monitoring well

Answer

Measure the total dissolved solids concentration in groundwater

Answer

Determine aquifer storativity over a large pumping radius

Answer

Assess vertical hydraulic gradient between screened intervals

Question 3

Natural attenuation as a groundwater remediation strategy relies on which set of processes?

Accepted Answer

Biodegradation, dispersion, dilution, sorption, and volatilization occurring without active intervention

Answer

Injection of nutrients and electron acceptors to accelerate microbial breakdown only

Answer

Precipitation and co-precipitation of dissolved metals using lime slurry

Answer

Phytoremediation by deep-rooted vegetation extracting contaminants from the water table

Question 4

Under RCRA and CERCLA frameworks, the Maximum Contaminant Level (MCL) for a groundwater contaminant typically serves as:

Accepted Answer

A health-based cleanup standard representing the maximum permissible concentration in drinking water

Answer

A trigger concentration requiring immediate site closure and evacuation

Answer

A background concentration established from pristine reference wells

Answer

An action level used only for air quality permit compliance

Question 5

Which parameter is measured by a geophysical borehole method to distinguish between clay-rich and sand-rich formations in an aquifer investigation?

Accepted Answer

Natural gamma radiation, which is higher in clay/shale due to radioactive potassium and thorium

Answer

Resistivity, which is lower in clean sandy formations saturated with fresh water

Answer

Neutron porosity, which is higher in dense crystalline rock

Answer

Acoustic velocity, which increases in clay-rich units due to lower rigidity

Question 6

A perched aquifer forms when:

Accepted Answer

An unsaturated zone lenticular aquitard intercepts infiltrating water, creating a localized saturated body above the regional water table

Answer

Recharge rates exceed the lateral discharge capacity of a confined aquifer

Answer

Two regional aquifers merge through hydraulic connection across a breached aquitard

Answer

Dense non-aqueous phase liquids displace native groundwater and form a saturated lens

Question 7

During a groundwater sampling event at a monitoring well, the purpose of purging the well before sample collection is to:

Accepted Answer

Remove stagnant water stored in the well casing so that the sample represents formation water

Answer

Increase hydraulic head in the well to improve sample volume

Answer

Add preservatives to the water column before collection

Answer

Test pump performance and calculate the well yield for permit reporting