Mont. Code § 87-5-502
An agency of state government, county, municipality, or other subdivision of the state of Montana, hereafter called applicant, shall not construct, modify, operate, maintain, or fail to maintain any construction project or hydraulic project which may or will obstruct, damage, diminish, destroy, change, modify, or vary the natural existing shape and form of any stream or its banks or tributaries by any type or form of construction without first causing notice of such planned construction to be served upon the department on forms furnished by the department as soon as preliminary plans are completed but not less than 60 days prior to commencement of final plans for construction. Such notice shall include detailed plans and specifications of so much of said project as may or will affect any such stream in any manner specified above.
§ 87-5-502, MCA