A partial acquisition will always be considered as severed land and appraised with the same basis as the whole property or as a separate economic unit. The appraiser shall ascertain in the appraisal of the property if the part to be acquired constitutes a separate economic unit or whether the acquisition area should be appraised in conjunction with the parent tract. The conclusion of the appraiser in this process must be supported with market and sales data.

When the part to be acquired is not considered as a separate tract or as an economic unit, it will be valued with the same basis of value as the whole property, or parent tract. The basis of value is the value per square foot or acre that was used to value the whole property.

However, the appraiser may conclude that the part to be acquired may be considered an economic unit or part of a larger economic unit. An economic unit may be defined as the smallest, marketable, and sustainable portion of a property. The existence of an economic unit should be justified by market sales of similar properties that defines the size and shape of the subject parcel and have the same highest and best use. The existence of economic units may also be justified by the presence of similar tracts in the market area and by physical divisions in the property such as roads, streets, creeks, rivers, and topographical differences. It must be remembered that in the valuation of a property with separate economic units, that the sum of the values of the parts of a property cannot exceed the market value of the whole property.

With the exception of the appraisal of small and vacant uncomplicated parcels that are valued with abbreviated appraisal report forms other than , the value of the remainder after the acquisition must be found by the appraisal process. The valuation of the remainder after the acquisition cannot be valued by a mathematical process of deducting the value of the part acquired from the whole property. In the valuation of the remainder property, the appraiser should consider the remainder in the most probable circumstances in accordance with the highest and best use analysis of the remainder tract. The difference in value between the remainder before the acquisition and remainder after the acquisition is the amount of damages or enhancements.

The improvements in the part to be acquired are to be valued by accepted appraisal methods and techniques. The appraiser will value only the improvements in the acquisition area for the part to be acquired in the initial appraisal report. This is also applicable to the valuation of bisected improvements such as buildings and structures. If the parcel should proceed to eminent domain, ROW PD will provide instructions to the appraiser on the valuation of bisected improvements; refer to that subsection of .