Grades of sidewalks. The grade or elevation of the top
of the inner line of sidewalks, except when otherwise specifically
provided by the Common Council, shall be above the grade of the adjoining
street in an amount equal to a minimum of 1/4 inch per foot of width
and a maximum of one inch per foot of width from the inner edge of
the sidewalk to the curb of the street. The grade or elevation of
the top of the inner line of the sidewalk between any two fixed grade
points shall be upon straight lines, or on vertical curves, if necessary,
to conform to the curblines, from one fixed point to the nearest fixed
point, excepting in cases otherwise specifically provided for by resolution
or approved plans.