Except as to property designated as possessing a special use, the fair cash market value of property in a proceeding in eminent domain shall be the amount of money that a purchaser, willing, but not obligated, to buy the property, would pay to an owner willing, but not obliged, to sell in a voluntary sale. For the acquisition or damaging of property under the O'Hare Modernization Act, the amount shall be determined as of the date of filing the complaint to condemn. For the acquisition of other property, the amount shall be determined and ascertained as of the date of filing the complaint to condemn, except that:
In the condemnation of property for a public improvement, there shall be excluded from the fair cash market value of the property any appreciation in value proximately caused by the improvement and any depreciation in value proximately caused by the improvement. However, such appreciation or depreciation shall not be excluded when property is condemned for a separate project conceived independently of and subsequent to the original project.
735 ILCS 30/10-5-60