Answer
The dam does not need to be reinforced.
Work Step by Step
We find the force on the dam:
$ F = \int_0^H (\rho gbh)dh \\ F = .5\rho gbh^2 $
Plugging in the known values, it follows:
$F=.5(1000)(9.81)(1500)(95^2) = 66.4 \ GN$
We find:
$\frac{100}{66.4} = 1.51$
This is greater than 1.5 times the force, so the dam is fine.
