Quick search by citation:

42 U.S. Code § 13284 - Cost-sharing

(a) Requirement

The Secretary shall require at least 50 percent of the costs directly and specifically related to any project under this part to be from non-Federal sources. Such share may be in the form of cash, personnel, services, equipment, and other resources.

(b) ReductionThe Secretary may reduce the amount of costs required to be provided by non-Federal sources under subsection (a) if the Secretary determines that the reduction is necessary and appropriate—
considering the technological risks involved in the project; and
in order to meet the objectives of this part.