We construct cohomology groups with compact support $H^i_c(X_{\rm ar},{\mathbb Z}(n))$ for separated schemes of finite type over a finite field which generalize Lichtenbaum's Weil-étale cohomology groups for smooth and projective schemes (see [22]). In particular, if Tate's conjecture holds, and rational and numerical equivalence agree up to torsion, then the groups $H^i_c(X_{\rm ar},{\mathbb Z}(n))$ are finitely generated, form an integral model of $l$ -adic cohomology with compact support, and admit a formula for the special values of the $\zeta$ -function of $X$