(a) Emergency response.--The provisions of this chapter shall not prevent or impede the immediate response of the department or responsible person to an emergency which involves an imminent or actual release of a regulated substance which threatens public health or the environment. The final remediation of the site shall comply with the provisions of this chapter which shall not be prejudiced by the mitigation measures undertaken to that point.

(b) Interim response.--The provisions of this chapter shall not prevent or impede a responsible person from undertaking mitigation measures to prevent significant impacts on human health or the environment. Those mitigation measures may include limiting public access to the release area, installing drainage controls to prevent runoff, stabilization and maintenance of containment structures, actions to prevent the migration of regulated substances, on-site treatment or other measures not prohibited by the department. The final remediation of the site shall comply with the provisions of this chapter which shall not be prejudiced by the mitigation measures undertaken to that point.