Dartmouth requires 35 courses to graduate, or just under 3 courses per quarter over 12 quarters. Presumably, this means that the normal course load is 3 courses per quarter.
http://www.dartmouth.edu/~regarchive/catalog/regulations04/undergrad/degree-req.html
Taking an overload of 4 courses in a quarter is only allowed in up to 4 of the 12 quarters. So the maximum number of courses in 12 quarters is 40.
http://www.dartmouth.edu/~reg/guides/csel/csel_student.html#fourthcourse
ABET-accredited BE degrees require at least 9 additional courses (total of 44), which means that more than 12 quarters will be needed to complete the BE degree.
http://engineering.dartmouth.edu/academics/undergraduate/be