  We describe a family of genus one fibered Calabi-Yau threefolds with
fundamental group ${\mathbb Z}/2$. On each Calabi-Yau $Z$ in the family we
exhibit a positive dimensional family of Mumford stable bundles whose symmetry
group is the Standard Model group $SU(3)\times SU(2)\times U(1)$ and which have
$c_{3} = 6$. We also show that for each bundle $V$ in our family, $c_{2}(Z) -
c_{2}(V)$ is the class of an effective curve on $Z$. These conditions ensure
that $Z$ and $V$ can be used for a phenomenologically relevant compactification
of Heterotic M-theory.
