During the construction activities at an industrial facility, it was observed th
ID: 532224 • Letter: D
Question
During the construction activities at an industrial facility, it was observed that some damage occurred to the two underground storage tanks (USTs) releasing some contaminants to the vadose zone as follows: a. The 250-gallon underground storage tank damaged releasing chlorobenzene (in the vadose zone).
At the time of incident, neither of the tanks was full, but had some material stored in them.
During site investigations, the vapor concentrations in the vadose zone were measured as:
Chlorobenzene 8 ppmV
Assume: The porosity of soil is 30% and 35% of the porosity is occupied by water.
Assume: Ambient temperature is 20C
Assume: 1 mole of ideal gas occupies 24 liters at 20C
Bulk density of soil: 1.8 g/cm3
Fraction of organic carbon in soil : 8 % (f=0.08)
7.48 gal = 1 ft3
1 m3 = 1,000 liters
Using 1 m3 of contaminated soil as the basis for your calculations, determine the following in the units indicated: (refer to the example on p. 53) practical calculations for ground water and soil Remediation.
a. Concentration of chlorobenzene in the soil phase (mg/Kg)
b. Mass of chlorobenzene in the soil (mg)
c. Total mass of chlorobenzene in all three phases (mg)
The selected properties of the contaminants are as follows:
Relevant properties of the contaminants are as follows:
Parameter Contaminants
Chlorobenzene
Benzene
Henry’s constant (dimensionless)
1.52x10-1
2.28x10-1
Molecular weight
112.6
78.1
Koc (L/Kg)
2.19x102
5.89x10
Density (at 20oC) (g/cm3)
1.106
0.876
Solubility (at 20oC) (mg/L)
4.90 x102
1.78 x103
Vapor pressure (mm Hg)
1.36
76
Note: The values provided above are from Chem Eng Handbook. Please use these values in your calculations.
Required information:
A. Summarize your results in a table listing the results (from a-i above) for each contaminant.
B. Estimate the maximum concentration of benzene (ppmV) (in the gas in vadose zone) if there was any free product (as benzene) above the groundwater. (refer to example on p. 42) practical calculations for ground water and soil Remediation.
C. Comment on:
- Behavior and distribution of the two contaminants in the vadose zone (DNAPL, LNAP, Kp etc)
- If there is any free product present (benzene) (in view of the maximum possible concentration if there is free product vs the measured gas concentration in the vadose zone).
Relevant properties of the contaminants are as follows:
Parameter Contaminants
Chlorobenzene
Benzene
Henry’s constant (dimensionless)
1.52x10-1
2.28x10-1
Molecular weight
112.6
78.1
Koc (L/Kg)
2.19x102
5.89x10
Density (at 20oC) (g/cm3)
1.106
0.876
Solubility (at 20oC) (mg/L)
4.90 x102
1.78 x103
Vapor pressure (mm Hg)
1.36
76
Explanation / Answer
A flood creates an elevated level of risk for environmental damage from UST systems. For example, UST systems may become displaced and release their contents into the environment, causing soil, surface water, and groundwater contamination. While there is little that can be done to prevent flooding, UST owners can take actions to minimize the damage potential that impacted USTs have on human health and the environment when flooding occurs.
Forces of rapidly moving water can cause soil erosion (resulting from soil above or around the UST being carried away by wind and floodwaters) and scour (resulting from the velocity of flowing water removing soil cover and supporting backfill material around the UST system). Exposing the system to stressors from flood water pressure or floating debris makes it even more vulnerable to being undermined or collapse. As a result of erosion and scour, underground piping can also shift and become detached from the UST, releasing product into the environment.
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