jmc

Drawing the square and examining the given lengths,you find that the three segments cut the square into three equal horizontal sections. Therefore, ($x$ being the side length), $\sqrt{x^2+(x/3{)}^2}=30$, or $x^2+(x/3{)}^2=900$. Solving for $x$, we get $x=9\sqrt{10}$, and $x^2=810.$ Area of the square is $\boxed{810}$.