Underground injection, the controlled emplacement of fluids into selected, deeply buried geologic formations through specially designed and monitored wells, was developed and used by the oil and gas industry in the 1930s. The same concept was first applied to the disposal of industrial wastes in the early 1950s, and the first operating permit for deep well injection of industrial wastes in Illinois was issued in 1965.

There are more than 680,000 underground waste and injection wells in the US, more than 150,000 of which shoot industrial fluids thousands of feet below the surface. Scientists and federal regulators acknowledge they do not know how many of the sites are leaking.

Use MAGNET to investigate the following problem.

A disposal well for liquid industrial waste commences operation in a horizontal isotropic confined limestone aquifer that has the following characteristics: thickness = 10m, secondary porosity =0.1%, bulk hydraulic conductivity = 5x 10^-5 m/s, specific storage =10^-6 cm^-1/ The injection rate is 100 gal/min.

• To what distance from the injection well will the front of potentiometric mound have extended after 1 month?
• To what distance from the injection well will the front of contamination have moved after 1 month? Neglect the effects of regional groundwater flow and dispersion. Assume that the aquifer is homogeneous and that the primary permeability of the limestone matrix is negligible. 

MAGNET/Modeling Hints:

• Use ‘Synthetic mode’ in MAGNET to create a model domain.
•  Add a well and assign it as a positive pumping rate off 100 gal/min(injection well adding water to the aquifer)
• Model a large enough area so that the plume is still well within the model domain after 1 month.