By Hydrosimulatics INC  

Continuous Subsurface Contamination Source

Modern landfills that meet federal standards are designed to prevent runoff from leaching into the groundwater, both through careful site selection and through installation of a protective landfill liner and leachate collection and treatment system. Sometimes these protective measures may fail. Additionally, older dumps and landfills did not have these protections. Runoff and leaching can carry a wide variety of pollutants from such sites, contaminating streams, groundwater, springs and wells. Improperly discarded hazardous wastes, such as those buried or placed in open pits, or just dumped on the land, can filter through the soil and find their way into the groundwater.  These are sometimes called "continuous" subsurface contamination sources, because the the contaminant is continuously released over time (rather than being released 'all at once'). Continuous sources may have time-varying or constant chemical concentrations.

Develop a MAGNET model that can simulate the plume migration for the following specific situation and perform a sensitivity analysis with respect to different ways to represent the subsurface contamination source (e.g., a leaky landfill, fertilizes from farming activities):

  • "specified concentration",  
  • "specified flux" or "recharge" with a concentration
  • "head-dependent flux", with a concentration 


Suggested Model Setup:

  • 2D Model size: 200m x 50m;
  • Driving head difference (left edge to right edge): 1m;
  • initial plume size: 10m x 10m.
  • Time step: 1 day

MAGNET/Modeling Hints:

  • Use 'Synthetic Mode' to set up your flow model ( 'Other Tools' > 'Utilities' > 'Go to Synthetic Case Area').
  • Conceptualize the model as 1-layer, confined aquifer.
  • Use line features as prescribed head boundaries to generate the head difference from the left edge to the right edge of the model.