45 C.F.R. § 84.81
This subpart does not require a recipient to take any action that it can demonstrate would result in a fundamental alteration in the nature of a program or activity or undue financial and administrative burdens. In those circumstances where a recipient's personnel believe that the proposed action would fundamentally alter the program or activity or would result in undue financial and administrative burdens, the recipient has the burden of proving that compliance with this subpart would result in such alteration or burdens. The decision that compliance would result in such alteration or burdens must be made by the head of the recipient or their designee after considering all the recipient's resources available for use in the funding and operation of the program or activity and must be accompanied by a written statement of reasons for reaching that conclusion. If an action required to comply with this part would result in such an alteration or such burdens, the recipient shall take any other action that would not result in such an alteration or such burdens but would nevertheless ensure that, to the maximum extent possible, individuals with disabilities receive the benefits or services provided by the recipient.
45 C.F.R. §84.81