A bill to extend and increase the authorization for the program to extend the winter navigation season for the Great Lakes-Saint Lawrence Seaway System.

Amends the River and Harbor Act of 1970 to extend the study of the winter navigation season for the Great Lakes-Saint Lawrence Seaway System until June 30, 1979 (presently December 31, 1976). Increases appropriations for such program to $15,684,000 (presently $9,500,000). Provides an allocation for Soo Locks operations.