(a) When authorized. Rights-of-entry for construction will be obtained by the district engineer only after a real estate directive or authorization to lease has been issued and then only when the construction schedule does not allow sufficient time to complete negotiations for an option to purchase or for a lease, as appropriate.

(b) Involuntary. Where a right-of-entry for construction cannot be negotiated, under the circumstances set forth in paragraph (a) of this section, a right-of-entry will be obtained through the institution of proceedings for the condemnation of fee title, an easement interest, or a leasehold interest, as appropriate.