How long does it take for NJDEP to clean up an oil tank soil contamination?

I placed an offer on a home and it was accepted. Did all the necessary steps had a mortgage commitment did an inspection. The inspector discovered An oil tank. The sellers were responsible to remove it. When they did they discovered numerous corrosion holes, oil odor, and oil in the subsoil layer. The NJDEP was called. There is now a case number. When should I expect to close on this home?

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