Great Lakes and Great Times: Michigan boasts four Great Lakes, 11,000 inland lakes, 36,000 miles of rivers and streams, 20 million acres of forests, 100 state and national parks and recreation areas, 1,300 miles of bike trails, 6,500 miles of snowmobile trails, the second-most ski areas in the nation, 650 public golf courses, 600 campgrounds, and an international dark-sky park-just for starters. Completion of 60 semester (90 term) credits including 24 semester (36 term) credits in any combination of course work in the following areas: structures, materials, soils, hydrology, surveying, design, bituminous, concrete, aggregate, chemistry, physics, geology, environmental science, computer science, highway or traffic technology, construction management, engineering, or mathematics may be substituted for the associates degree.