A truck hauling liquid waste has overturned on the highway. The waste is not recovered at the time of the spill, and we are interested in the concentration reaching a small stream located at a distance 150 meters from the highway and running parallel with it. The stream carries a discharge of 5 cfs. The waste moves through a sandy aquifer that is 9 meters thick and has a porosity of 0.35. The longitudinal dispersivity is 3.0 m while the vertical and horizontal dispersivities are 0.1 and 0.6 m, respectively. The groundwater seepage velocity is 0.8 m/day and is directed transverse to the highway and the stream. 4000 kg of waste were spilled. For each of the following cases, determine the maximum concentration of waste reaching the stream, and plot the stream concentration that will be observed by downstream users of surface water from the stream.
- the waste is conservative.
- the waste is radioactive with a half-life of 120 days.
- the waste adsorbs onto the soil with a retardation factor of 3.5.
Solve the problem using MAGNET.
MAGNET/Modeling Hints:
- Use 'Synthetic Mode' to set up your flow model ( 'Other Tools' > 'Utilities' > 'Go to Synthetic Case Area')
- Use the ‘Distance Display’ capabilities when editing geometric features and/or the ‘Ruler’ tool to properly represent distances between model features.