The underground storage of a gas station has leaked gasoline into the ground. Among the constituents of gasoline are benzene, with a Kd value of 1.8 L/kg for the soil in that location, and toluene, with a Kd of 3.3 L/kg. The soil has a solids density of 2.6 kg/L and a hydraulic conductivity of 2.9 × 10^-5 m/s and is 37% pores (by volume). The site is to be remediated by pumping out and treating groundwater from a well 15 m downgradient from the site of the spill, where the water table is 0.4 m lower than at the leaking tank. How long will it take for:

a. benzene
b. toluene to reach the well?

a) benzene = 910 days

b) toluene = 1612.67 days

Explanation:

Given:

Kd = 1.8 L/kg (benzene)

Kd = 3.3 L/kg (toluene)

psolid = solids density = 2.6 kg/L

K = 2.9x10⁻⁵m/s

pores = n = 0.37

water table = 0.4 m

ground water = 15 m

u = K/n = (2.9x10⁻⁵ * (0.4/15)) / 0.37 = 2.09x10⁻⁶m/s

a) For benzene:

The time will take will be:

b) For toluene:

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