2. After widespread groundwater contamination in the U.S. was discovered in the

Question

2. After widespread groundwater contamination in the U.S. was discovered in the 1980s, regulations were put in place to prevent or contain leaks from underground storage tanks, such as those used by gas stations to hold gasoline and by various industries to hold solvents and fuels. To some these regulations appeared overly stringent, but a small spill, or a small leak over an extended period of time, can contaminate a large volume of groundwater. How many millions of gallons per day of groundwater could potentially be contaminated by a leak of one drop per second (a steady drip) of trichloroethylene (TCE)? Note that a leak of this size from a large or heavily used tank would be very difficult to detect if it occurred below the ground surface. In your calculation, assume that “contamination” is defined as a TCE concentration of 5 g/L of TCE (the MCL for TCE in drinking water). Also assume that the volume of one drop is 0.05 mL, TCE has a density of 1.46 g/mL, and there are 3.785 liters in a gallon.

Explanation / Answer

density of TCE=1.46 g/mL

volume of one drop TCE= 0.05 mL

So mass of TCE added per drop= 0.05 mL*1.46 g/mL=0.073g

If 1drop(=0.073g) is added per second ,then mass of TCE added in a day=0.073g/s *[no of seconds in a day]=0.073g/s *[24 hrs*3600s/hr]=6307.2 grams per day=6307.2 *10^6 ug/day

Contamination by TCE=5 ug/L

So volume of water contaminated by 6307.2 *10^6 ug of TCE=6307.2 *10^6 ug/(5 ug/L)=1261.44 *10^6 L

So volume of ground water contaminated=1261.44 L*10^6* (1gallon/3.785 L)=333.273 *10^6 gallons of ground water contamination in a day

1 million =10^6

So Answer =333.273 million gallons of ground water contamination in a day

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