4. A manufacturing facility prints circuit boards using TCE. The TCE washwater spills into a shallow groundwater at a steady rate such that it creates a continuous source of 10.0 mg/L. The groundwater beneath the site has an average linear velocity of 1.0 ft/d. The fractional organic carbon content of the soil is 0.012. The bulk density of the soil is 1.6 g/mL. The porosity is 0.35 and effective porosity is 0.18.

a) What is the retardation coefficient for TCE in this system?

b) Estimate the longitudinal dispersivity using a plume length of 600 feet using the Xu and Eckstein relationship.

c) What is the concentration of TCE at a well 75 feet directly downgradient of the spill after 200 days? Use the full Ogata-Banks solution with retardation. Assume no degradation of TCE.

d) If the TCE did not adsorb to the soil what would the concentration be at this well after 200 days? Assume no degradation of TCE.

e) Recalculate the concentration at 200 days assuming TCE is retarded and degrades according to a first order rate with coefficient of 0.01 /d.

f) What is the concentration of TCE at this well once the plume has reached steady state? Assume retarded transport and that degradation of TCE at a first order rate with coefficient of 0.01 /d.