Description
This problem is based on the Former Radiator Factory Site. Groundwater pump and
treat is being considered for containment of the source area (triangle shape on property
south of the railroad tracks). A single extraction well is proposed to capture and contain
a TCE plume at the northern property boundary. The aquifer can be assumed to be
isotropic and homogenous. Depth to groundwater is approximately 15 feet, and depth to
bedrock is approximately 36 feet below ground surface near the downgradient property
boundary (unconfined aquifer thickness is 21 feet) with a hydraulic conductivity of
2.4×10 -4 cm/s and a hydraulic gradient of 0.05 m/m (ft/ft). Assume that the design
drawdown at the extraction well is limited to 2 meters, and the extraction well diameter is
12 inches.
a) Estimate the pore volume of the source area
b) Calculate transmissivity of the aquifer
c) What extraction flow rate is required to contain the entire plume width?
d) Where does the stagnation point occur downgradient of the extraction well?
e) What is the capture zone width at the extraction well?
f) What is the radial zone of influence of the extraction well?
g) Provide a sketch of the zone of influence, the capture zone, and stagnation point.
h) Estimated the number of contaminated pore volumes to be extracted by the system
to meet remedial goals of Federal Maximum Contaminant Levels (MCLs) with the
following maximum baseline concentrations and assuming linear sorption is the
primary retardation mechanism (assume bulk density of 1.65 kg/L and 1% for f oc )
TCE = 200,00 ug/L
Cis-1,2-Dichloroethene = 12,000 ug/L
Vinyl Chloride = 1,000 ug/L
i) Using the flow rate calculated in Part C, how many pore volumes would be removed
in one year. Estimate the number of years the pump and treat system will need to
operate to meet remedial goals
