The Secretary of the Interior is authorized, in order to carry out the purposes mentioned in section 571 of this title, to make financial contributions on the basis of programs or projects approved by the Secretary to the Commonwealth of Pennsylvania (hereinafter designated as the "Commonwealth") to seal abandoned coal mines and to fill voids in abandoned coal mines, in those instances where such work is in the interest of the public health or safety, and for control and drainage of water which, if not so controlled or drained, will cause the flooding of anthracite coal formations, said contributions to be applied to the cost of drainage works, pumping plants, and related facilities but subject, however, to the following conditions and limitations:

(a) Contributions to be matched by Commonwealth
The amounts authorized to be contributed by the Secretary of the Interior to the Commonwealth shall be equally matched by the Commonwealth;

(b) Amount of contributions authorized
The total amount of contributions by the Secretary of the Interior under the authority of this chapter shall not exceed $8,500,000, of which $1,500,000 of the unexpended balance remaining as of July 31, 1962, shall be reserved for the control and drainage of water;

(c) Limitation on use of contribution
The amounts contributed by the Secretary of the Interior under the authority of this chapter and the equally matched amounts contributed by the Commonwealth shall not be used for operating and maintaining projects constructed pursuant to this chapter or for the purchase of culm, rock, or spoil banks;

(d) Commonwealth responsible for installation and operation of projects
The Commonwealth shall have full responsibility for installing, operating, and maintaining projects constructed pursuant to this chapter, and shall give evidence, satisfactory to the Secretary of the Interior, that it will enforce effective installation, operation, and maintenance safeguards;

(e) Location and operation of projects
Projects constructed pursuant to this chapter shall be so located, operated, and maintained as to provide the maximum conservation of anthracite coal resources or, in those instances where such work would be in the interest of the public health or safety, to seal abandoned coal mines and to fill voids in abandoned coal mines, and, where possible, to avoid creating inequities among those mines which may be affected by the waters to be controlled thereby; and

(f) Economic justification for abandoned coal mine projects
Projects for the sealing of abandoned coal mines or the filling of voids in abandoned coal mines shall be determined by the Secretary of the Interior to be economically justified. The Secretary shall not find any project to be economically justified unless the potential benefits are estimated by him to exceed the estimated cost of the project.