Neb. Rev. Stat. § 81-15,308

In lieu of issuing an order under section 81-15,304 , the director may allow the responsible person or any other person to voluntarily remediate site conditions under the Remedial Action Plan Monitoring Act. A person that voluntarily chooses to apply under section 81-15,184 must meet all requirements of such section. Based on the nature of the release, the director may require such person to pay for a contractor to oversee remedial work hired or approved by the department.