  We establish several boundary $\varepsilon$-regularity criteria for suitable
weak solutions for the 3D incompressible Navier-Stokes equations in a half
cylinder with the Dirichlet boundary condition on the flat boundary. Our proofs
are based on delicate iteration arguments and interpolation techniques. These
results extend and provide alternative proofs for the earlier interior results
by Vasseur [18], Choi-Vasseur [2], and Phuc-Guevara [6].
