A hazardous waste facility is to be constructed in a given area. The state requires a buffer zone between the trenches and the property boundary. Over 500 different constituents are to be included in the waste, some with reasonably large distribution coefficients, others with a likely distribution of zero. A few years after construction, a plume is first noted by observation wells at the waste boundary. The maximum concentration in the plume occurs in a zone of about 6m thick and extends the entire length of waste boundary, or about 60m. Because of low permeability bounding materials, the plume is only capable of lateral spreading in Y but not vertical spreading in Z.
A. Calculate the maximum concentration that might be expected (in terms of c0, the plume concentration at the waste boundary) once the plume arrives at the edge of the buffer zone, which is 1500m from the waste boundary. The transverse dispersion coefficient is 1 x 10-2m2/s and the linear velocity (flow through the pores) is 1x10-4m/s.
B. Develop a MAGNET model to confirm your results using an analytical approach.
MAGNET/Modeling Hints:
- Use ‘Synthetic mode’ in MAGNET to create a model domain.
- Use the ‘Distance Display’ capabilities when editing geometric features and/or the ‘Ruler’ tool to properly represent distances between model features.
- Represent the rivers as constant head zone features.