in such paragraph is feasible and in the public interest, the Secretary may provide for the construction of the routes. (B) Modifications The Secretary may modify the routes as necessary in the opinion of the Secretary. (C) Use of volunteer services and contributions Routes may be constructed under this section through the acceptance of volunteer services and contributions from non-Federal sources to reduce or eliminate the need for Federal expenditures to construct the route. (3) Compliance In carrying out this section, the Secretary shall comply with— (A) the laws (including regulations) generally applicable to the National Forest System