The Secretary of the Army, in expending appropriations in the preparation for and construction of works for the restraining or impounding of mining debris in the State of California, is authorized to enter into an agreement that the contractor shall look solely to the State of California for one-half of such expense, to be paid out of said State’s appropriation, and the United States shall in nowise be liable for said one-half.

The Secretary of the Army, in carrying out the provisions of any Act of Congress, providing for the restraining or impounding of mining debris in California, may, in his discretion, when in his judgment the aggregate of appropriations already made by said State and Congress and available therefor are sufficient to complete the same, undertake the works necessary thereto by hired labor and by purchase of supplies and materials therefor, and may accept payments on account thereof as the work progresses under and according to the provisions of the acts of the legislature of said State for such purposes.