The Secretary shall require each organization to contribute toward the cost of the project (other than by loan and/or grant of Federal funds) an amount equal to 25 percent or more of the allowable estimated cost of the project:
Provided, That the Secretary, at his discretion, may reduce the amount of such contribution to the extent that he determines that the organization is unable to secure financing from other sources under reasonable terms and conditions, and shall include letters from lenders or other written evidence in support of any funding of an applicant’s inability to secure such financing in any project proposal transmitted to the Congress:
Provided further, That under no circumstances shall the Secretary reduce the amount of such contribution to less than 10 percent of the allowable estimated total project costs. In determining the amount of the contribution as required by this paragraph, the Secretary shall credit toward that amount the cost of investigations, surveys, engineering, and other services necessary to the preparation of proposals and plans for the project as required by the Secretary, and the costs of lands and rights-of-way required for the project, and the $5,000 fee described in
section 422c of this title. In determining the allowable estimated cost of the project, the Secretary shall not include the amount of grants accorded to the organization under
section 422e(b) of this title.