48 CFR §436.205

1. (a)When it appears that funds may be insufficient for all the desired features of construction, the contracting officer may provide in the solicitation for a base bid item covering the work as specified and for one or more additive or deductive bid items which progressively add or omit specified features of the work in a stated order of priority.
2. (b)In the alternative, the contracting officer may use the policies and procedures found in FAR 17.2, Options.