jmc

Let $s$ represent the sidelength of the equilateral triangular base. Each face of the pyramid has an area of $\frac{1}{2}bh=75$, where $b$ is the sidelength of the base and $h$ is the slant height of 30 meters. We have $$75=\frac{1}{2}s(30)=15s.$$So, $s=5$ and the sidelength of the base is $\boxed{5}$ meters.