Mad River, Humboldt and Trinity Counties, California. Letter from the Secretary of the Army transmitting a letter from the Chief of Engineers, Department of the Army, dated June 3, 1968, submitting a report, together with accompanying papers and illustrations, on an interim report on Mad River, Humboldt and Trinity Counties, California, requested by a resolution of the Committee on Public Works, House of Representatives, adopted June 13, 1956. additional authority for the study is contained in section 209 of the Flood Control Act of 1962.