  General criteria for the existence of conformally flat Riemannian solutions
in 3D Poincar\'e gauge theory without matter are formulated. Using these
criteria, we show that the Oliva-Tempo-Troncoso black hole, a solution of the
Bergshoeff-Hohm-Town\-send gravity, is also an exact vacuum solution of the
Poincar\'e gauge theory. The related conserved charges, calculated from the
Hamiltonian boundary term, are shown to satisfy the first law of black hole
thermodynamics. The form of the boundary term is verified by using the
covariant Hamiltonian approach.
