Let's call the height of the viaduct "h".
Using trigonometry, we can set up the following equation:
tan(46.2) = h / (150 + 6)
Simplifying this equation, we get:
h = (150 + 6) * tan(46.2)
Solving this equation, we get:
h ≈ 148.5 feet
Rounding to the nearest foot, we get that the height of the viaduct is approximately 149 feet.